Synthetic polymers with improved light stability by incorporation of inorganic phosphors

Abstract

Described herein are methods for improving the color stability of synthetic polymer compositions by incorporating one or more inorganic phosphor dopants into synthetic polymers. The inorganic phosphor dopant absorbs UV light and emits the UV light as down-converted visible light, resulting in a brighter appearance for the synthetic polymer composition. Also described are methods of making synthetic polymer compositions with improved color stability.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 366,582, filed on June 17, 2022, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The presently disclosed subject matter generally relates to methods for improving the color stability of synthetic polymers. Background Art

[0004] Phosphor materials have the property of emitting ultraviolet, visible and infrared light by the action of external excitation means such as irradiation of electromagnetic waves (e.g., electron beams, X-rays, ultraviolet rays, visible light, etc.) or application of electric fields, and are therefore used in a large number of photoelectric transducers or photoelectric conversion devices. Examples of such devices are light-emitting devices, including white light-emitting diodes, fluorescent lamps, electron beam tubes, plasma display panels, inorganic electroluminescent displays and scintillators. In particular, inorganic phosphors are widely studied to meet the demand for low-voltage stimulated lighting sources due to the increased global energy consumption. Modern white light-emitting diodes (WLEDs) have replaced less efficient incandescent lamps and conventional fluorescent lighting sources containing mercury due to their environmental protection, long life, low energy consumption, reliability, and high luminous efficiency.

[0005] Lanthanides are often used as phosphors for luminescence applications. For example, the shielded f orbitals of praseodymium allow for long excited state lifetimes and high luminescence yields. In fact, Pr 3+ Typically a dopant ion for red, blue, green and ultraviolet phosphors. Summary of the invention

[0006] In one aspect, the subject matter of the present disclosure relates to a method for improving the color stability of a synthetic polymer composition, the method comprising: exposing a synthetic polymer host material comprising one or more inorganic phosphor dopants to UV light; wherein the one or more inorganic phosphor dopants in the synthetic polymer host material absorb the UV light and then emit the UV light as down-converted visible light.

[0007] On the other hand, the subject matter of the present disclosure relates to a synthetic polymer composition comprising: a synthetic polymer host material containing one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the synthetic polymer host material emit down-converted visible light when exposed to UV light; and the synthetic polymer composition exhibits mechanical and flammability properties comparable to those of a synthetic polymer composition not containing the one or more inorganic phosphor dopants.

[0008] On the other hand, the subject matter of the present disclosure relates to a method for preparing a synthetic polymer composition, which includes: contacting a synthetic polymer host material with one or more inorganic phosphor dopants to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material are capable of absorbing UV light and then emitting the UV light as down-converted visible light.

[0009] These and other aspects are fully explained in this article. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A The process of preparing inorganic phosphor-doped synthetic polymer materials according to the method described herein is shown.

[0011] Figure 1B A process for creating a brighter appearance for an object by applying the inorganic phosphor-doped synthetic polymer material described herein is shown.

[0012] Figure 2A A process for creating a brighter appearance for an object by applying the inorganic phosphor-doped synthetic polymer material described herein is shown.

[0013] Figure 2B A process for creating a brighter appearance for an object by applying the inorganic phosphor-doped synthetic polymer material described herein is shown.

[0014] Figure 3 Exemplary excitation and emission spectra of inorganic phosphor dopants are shown.

[0015] Figure 4 It shows how white light can be produced by mixing blue, green and red emitted light.

[0016] Figure 5 Exemplary lattice structures of doped solid-state materials (ie, inorganic phosphor dopants) are shown. DETAILED DESCRIPTION

[0017] The subject matter described herein relates to methods for improving the color stability of synthetic polymeric materials by exploiting the intrinsic luminescent properties of inorganic rare earth phosphors.

[0018] When exposed to UV light in the presence of oxygen, synthetic polymers (such as thermoplastics) will generally undergo photo-oxidation. When the polymer absorbs the UV radiation energy, it can lead to bond breakage because the energy of the UV light is greater than the dissociation energy of the carbon-carbon sigma bond in the synthetic polymer. In fact, UV light (such as UV-C light) has a wavelength of 200nm to 280nm and a photon energy of 6.2eV to 4.4eV. In contrast, the bond energy of a typical carbon-carbon sigma bond is only 3.8eV. Thus, absorption of UV-C light in the presence of oxygen can lead to bond dissociation oxidation, which leads to changes in the molecular structure of the polymer. Such structural changes are usually accompanied by undesirable and noticeable changes in the polymer, such as discoloration (yellowing) and embrittlement.

[0019] Current solutions to the discoloration and embrittlement often experienced by synthetic polymers exposed to UV light include: (1) using polymers with higher color stability in applications where there is high UV light exposure; and / or (2) incorporating UV stabilizing additives into synthetic polymer formulations. However, synthetic polymers that exhibit satisfactory color stability may lack appropriate mechanical properties, such as impact durability and chemical resistance. In addition, additives used to improve color stability in synthetic polymers often reduce the mechanical properties of the material, such as tensile strength. These additives have also been shown to reduce the flammability of the material. Therefore, there is a need in the art to stabilize the color of synthetic polymers exposed to UV light without reducing other material performance properties.

[0020] The subject matter described herein overcomes the limitations of the prior art by incorporating inorganic phosphors into synthetic polymer compositions. The inorganic phosphors absorb UV light (103) and convert it into harmless visible light (104). The inorganic phosphors used in the methods and compositions described herein are crystalline materials having a lattice structure that imparts high photostability, such as Figure 5As shown in the exemplary lattice structure of . For example, the regular and rigid arrangement of atoms in the lattice gives the phosphor an enhanced thermal stability. In these phosphors, a small percentage of metal "dopant" ions are incorporated into the lattice, which will affect the excitation and emission properties of the phosphor. As used herein, an inorganic phosphor dopant (102) refers to a metal oxide or metal fluoride material containing a rare earth (107) or a transition metal. In certain instances, the synthetic polymer composition contains from about 0.05 wt % to about 10 wt % or from about 0.05 wt % to about 5 wt % of an inorganic phosphor dopant. In certain other examples, the synthetic polymer composition comprises about 0.05 wt % to about 0.15 wt %, about 0.10 wt % to about 0.25 wt %, about 0.15 wt % to about 3 wt %, about 0.25 wt % to about 4 wt %, about 1 wt % to about 5 wt %, about 1.5 wt % to about 3.5 wt %, about 2.5 wt % to about 4 wt %, about 0.50 wt % to about 4.5 wt %, about 4 wt % to about 5 wt %, about 5 wt % to about 10 wt %, about 3 wt % to about 7 wt %, about 4 wt % to about 8 wt %, about 6 wt % to about 9 wt %, or about 7 wt % to about 10 wt % of an inorganic phosphor dopant. Since the inorganic phosphor material is a ceramic type material, it has no adverse effect on the mechanical or flammability properties of the synthetic polymer host material (101). Many phosphors strongly absorb (high energy; short wavelength) UV light (103) with emission of longer wavelength and lower energy light than originally absorbed by the phosphor. This emission is usually in the visible range which is not destructive to the synthetic polymer. The process of light absorption at one wavelength followed by emission at a longer wavelength is called "down conversion". The inorganic phosphors in the synthetic polymers described herein absorb high energy UV light (180nm-360nm) and emit the energy as "down converted" visible light (200nm-700nm), such as Figure 3 Exemplary excitation and emission spectra of an example inorganic phosphor are shown in FIG.

[0021] As described herein, the color of the emitted light energy can be customized by incorporating different metal ions into the metal oxide (106) or metal fluoride (109) host lattice. Combinations of different emission colors will produce white / off-white light. For example, a blue-yellow or blue-green-red emitter combination provides white / off-white emission. Such combinations of light emission from phosphors can be used to customize the visual color of solids.

[0022] The subject matter described herein manages the effects of UV light on synthetic polymers by selectively incorporating inorganic phosphors to absorb and down-convert visible light to provide a brighter appearance to the synthetic polymer material. A brighter appearance is the brightness perceived by a viewer.

[0023] Figure 1B ,2A 2B illustrate an exemplary process for producing a brighter appearance for an object by applying the inorganic phosphor-doped synthetic polymer material described herein. In short, as Figure 1A As shown, one or more inorganic phosphor dopants (102) are prepared in step 150, and as shown in step 155, the one or more inorganic phosphor dopants (102) are incorporated into the synthetic polymer host material (101) to prepare an inorganic phosphor-doped synthetic polymer material. Figure 1B and 2A As shown, in step 160, the inorganic phosphor doped synthetic polymer material is exposed to UV light to charge the inorganic phosphor dopant in the material. Dark and bright inorganic phosphor dopants represent two different types of dopants, each emitting visible light of different wavelengths. Figure 2A After the inorganic phosphor dopant is charged, the UV light is removed and the inorganic phosphor dopant emits visible light, thereby producing a brighter appearance for the synthetic polymer host material, such as Figure 2B and Figure 1B In this example, the synthetic polymer host material includes two different inorganic phosphor dopants that emit light of different wavelengths but combine to form white light. The brighter appearance of the synthetic polymer host material can be visually perceived by an observer (by Figure 2B The eyes shown are shown).

[0024] The subject matter of the present disclosure will now be described more fully below. However, the technical personnel of the field of the subject matter of the present disclosure that benefits from the teaching presented in the foregoing description will think of many modifications and other examples of the subject matter of the present disclosure set forth herein. Therefore, it should be understood that the subject matter of the present disclosure is not limited to the disclosed specific examples, and modifications and other examples should be included in the scope of the appended claims. In other words, the subject matter described herein covers all substitutions, modifications and equivalents. Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art are generally understood. All publications, patent applications, patents and other references mentioned herein are incorporated herein by reference as a whole. In the case where one or more of the documents, patents and similar materials incorporated are different or contradictory from the present application (including but not limited to the terms, term usage, described technology, etc. defined), the present application shall prevail.

[0025] I. Definitions

[0026] As used herein, "and / or" refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the absence of a combination when interpreted in the alternative ("or").

[0027] As used herein, the terms "approximately," "about," "substantially," and "substantially" refer to an amount that is close to a stated amount and still performs a desired function or achieves a desired result. For example, in some instances, as the context may dictate, the terms "approximately," "about," and "substantially" may refer to an amount that is within less than or equal to 10% of a stated amount. As used herein, the term "generally" refers to a value, amount, or characteristic that primarily includes or tends toward a particular value, amount, or characteristic.

[0028] As used herein, conditional language, such as "can," "may," "might," "could," "for example," and the like, unless otherwise specifically stated or otherwise understood in the context of use, is generally intended to convey that certain instances include (while other instances do not include) certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that one or more instances require features, elements, and / or steps in any way, or that one or more instances must include logic for determining whether such features, elements, and / or steps are included or will be performed in any particular instance with or without author input or prompting. The terms "consisting of," "composed of," and the like are synonymous and used in a closed manner and do not contain additional elements, features, actions, operations, and the like. The terms "consisting essentially of," "consisting essentially of," and the like are synonymous semi-closed terms that indicate that items in a claim are limited to the components specified in the claim and those components that do not materially affect the basic and novel characteristics of the claim. Additionally, the term "or" is used in its inclusive sense (rather than in its exclusive sense) such that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list.

[0029] As used herein, "contacting" refers to contacting a synthetic polymer host material (101) with an inorganic phosphor dopant (102) to prepare an inorganic phosphor-doped synthetic polymer material. In an example, such contacting may be referred to as "compounding," wherein the synthetic plastic is melted and mixed with an additive material (i.e., an inorganic phosphor dopant) to prepare a modified polymer. The synthetic polymer acts as a host material, wherein Figure 1A As shown, the inorganic phosphor dopant (102) is incorporated into the host material by, for example, applying heat and / or pressure.

[0030] As used herein, "improving color stability" refers to extending the color life of the synthetic polymer host material (101) and / or reducing the incidence of yellowing of the synthetic polymer host material (101) caused by exposure to UV light (103). As described herein, the inorganic phosphor dopant (102) in the synthetic polymer material can absorb UV light (103), thereby reducing the effect of UV absorption on the color stability of the polymer. In an example, the inorganic phosphor dopant (102) absorbs more incident UV light (103) than the synthetic polymer host material (101), thereby counteracting photo-oxidation and discoloration of the polymer material.

[0031] This improved color stability can be measured visually using a control synthetic polymer that has not been subjected to UV exposure ("control"), a synthetic polymer that has been subjected to UV exposure ("standard"), and a synthetic polymer described herein that has also been subjected to UV exposure and includes one or more inorganic phosphor dopants ("test") The color change can be easily perceived by comparing the amount of any color change between the control, standard, and test samples. For example, if a synthetic polymer that includes one or more inorganic phosphor dopants (test sample) shows no or significantly less yellowing compared to a standard sample that has also been subjected to UV exposure, it is referred to as having improved color stability. Both the standard and the test are compared to the control to visualize any changes in color.

[0032] Additionally, different phosphors can be mixed in the synthetic polymer host material (101) to emit white or off-white visible light (104), thereby creating a brighter appearance of the polymer material. The concept of creating white light by mixing phosphors that emit light of different wavelengths is similar to what is observed when using LEDs to create white light, e.g. Figure 4 For example, a conventional white light source can be achieved by mixing red light, green light, and blue light at a suitable intensity ratio. Alternatively, a white light source can be achieved by mixing yellow light and blue light at a suitable intensity ratio. Examples of selecting phosphors and incorporating them into synthetic polymer materials to emit light of different colors, which then combine to produce white light, are provided herein.

[0033] As used herein, "white light" refers to the combination of all wavelengths of electromagnetic radiation in the visible range of the spectrum, wherein each wavelength is present in equal amounts relative to the other wavelengths. "Off-white" light refers to a combination of wavelengths in the visible range of electromagnetic radiation that is, for example, close to white light but not present in equal amounts.

[0034] As used herein, "photo-oxidation" refers to the degradation of polymer surfaces due to the combined action of light and oxygen. Photo-oxidation causes polymer chain scission, resulting in the material becoming increasingly brittle.

[0035] As used herein, the terms "inorganic phosphor dopant" and "phosphor" are used interchangeably.

[0036] II. Methods for Improving Color Stability of Synthetic Polymers

[0037] In certain examples, the subject matter described herein relates to a method for improving the color stability of a synthetic polymer composition, comprising:

[0038] exposing a synthetic polymer host material (101) comprising one or more inorganic phosphor dopants (102) to UV light (103);

[0039] The one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) absorb UV light (103) and then emit the UV light as down-converted visible light (104).

[0040] When a phosphor is exposed to radiation, orbiting electrons in its atoms are excited to a higher energy level; when they return to their previous energy level, they emit energy as light of a specific color. In fact, the scintillation process in inorganic materials is due to the electronic band structure present in the crystal. Incoming particles can excite electrons from the valence band to the conduction band or exciton band (located just below the conduction band and separated from the valence band by an energy gap). This leaves associated holes in the valence band. Impurities create electronic energy levels in the forbidden band. Excitons are loosely bound electron-hole pairs that diffuse through the crystal lattice until they are captured as a whole by the impurity center. The latter then quickly de-excite by emitting scintillation light (i.e., photons). The wavelength of the emission depends on the atoms themselves and the surrounding crystal structure.

[0041] As described herein, the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) absorb UV light (103) and emit the UV light as down-converted visible light (104). In certain examples, the UV light (103) used to excite (charge) orbital electrons of the inorganic phosphor dopant (102) has a wavelength of about 160nm to 380nm. In other examples, the UV light (103) has a wavelength of about 160nm to 320nm, about 160nm to 260nm, about 160nm to 200nm, about 180nm to 240nm, about 200nm to 250nm, about 250nm to 380nm, about 210nm to 250nm, about 225nm to 260nm, about 230nm to 250nm, or about 190nm to 260nm. In certain other examples, the UV light (103) has a wavelength of approximately 222 nm, 254 nm, or 275 nm.

[0042] Non-limiting examples of UV light sources for providing UV light (103) in the above method include, for example, black lights, short-wave UV lamps, incandescent lamps, gas discharge lamps, UV LEDs, deuterium lamps, pulsed xenon lamps, and UV lasers. For example, the UV light source can be a pulsed xenon UV device in the form of a handheld stick. The stick can be held, for example, at a distance of 1 to 5 inches from the surface of the material containing one or more inorganic phosphor dopants (102), wherein the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) absorb the UV light (103). In another example, the UV light source for providing UV light (103) is a deuterium lamp having a light range of about 185 nm to about 400 nm.

[0043] In addition to UV light, other excitation energy sources can also be used in the methods described herein. Personal protective equipment (PPE) may be required to operate such energy sources.

[0044] In certain examples of the above methods for improving the color stability of synthetic polymer compositions, the absorption of UV light (103) by the one or more inorganic phosphor dopants (102) reduces photo-oxidation of the synthetic polymer host material (101). As used herein, reducing photo-oxidation of the synthetic polymer host material (101) refers to a reduction in discoloration and / or embrittlement of the synthetic polymer host material (101) when exposed to UV light (103) because the inorganic phosphor dopant (102) in the synthetic polymer host material (101) absorbs most of the UV light (103) instead of the synthetic polymer host material (101) itself. Given the different behaviors of UV absorption in synthetic polymers, the specific reduction in photo-oxidation is material-dependent. The inorganic phosphor dopant (102) typically exhibits very strong absorption. Thus, incorporating the one or more inorganic phosphor dopants (102) into the synthetic polymer host material (101) can reduce photo-oxidation of the synthetic polymer host material (101) by up to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45% compared to a synthetic polymer host material without the one or more inorganic phosphor dopants. For example, photo-oxidation of a material can be detected using infrared spectroscopy. In particular, peroxy species and carbonyl groups formed by photo-oxidation typically contain different absorption bands.

[0045] In certain examples of the method for improving the color stability of a synthetic polymer, the visible light (104) emitted by the one or more inorganic phosphor dopants (102) produces a brighter appearance for the synthetic polymer composition. An observer observing the synthetic polymer composition perceives a brighter appearance. In fact, "brightness" as used herein is a property of visual perception that a source appears to be radiated or reflected light. Brightness is a perception caused by the brightness of a visual target. In certain examples, the inorganic phosphor dopant (102) can emit blue visible light (104) with a wavelength of 450nm to 495nm. The blue visible light (104) emitted from the synthetic polymer composition containing the one or more inorganic phosphor dopants can visually offset the yellow discoloration of the synthetic polymer host material (101). The aforementioned effect is similar to the effect of broad visible light emission, where certain dopants in a material emitting broad light have the effect of making the entire material appear visually brighter.

[0046] In certain examples of the method for improving the color stability of a synthetic polymer, the light emitted by the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) is down-converted visible light (104). In certain examples of the above method, the one or more inorganic phosphor dopants (102) emit visible light (104) with a wavelength of about 200 nm to 700 nm. In other examples, the one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength of about 400nm to 495nm, about 620nm to 700nm, about 590nm to 620nm, about 570nm to 590nm, about 495nm to 570nm, about 390nm to 450nm, about 380nm to 600nm, about 350nm to 460nm, about 600nm to 700nm, about 450nm to 600nm, about 200nm to 280nm, about 450nm to 495nm, about 380nm to 450nm, about 200nm to 270nm, about 200nm to 250nm, about 225nm to 250nm, about 200nm to 225nm, about 200nm to 275nm, or about 225nm to 275nm. A specific wavelength or range of wavelengths may be selected based on the desired color of the emitted light. For example, if the inorganic phosphor dopant (102) is desired to emit blue light, a phosphor is selected that emits visible light (104) having a wavelength of about 400 nm to 495 nm. In certain other instances, if the inorganic phosphor dopant (102) is desired to emit green light, a phosphor is selected that emits visible light (104) having a wavelength of about 495 nm to 570 nm. In other instances, if the inorganic phosphor dopant (102) is desired to emit violet light, a phosphor is selected that emits visible light (104) having a wavelength of about 380 nm to 450 nm. In certain other instances, if the inorganic phosphor dopant (102) is desired to emit yellow light, a phosphor is selected that emits visible light (104) having a wavelength of about 570 nm to 590 nm. In another example, if the inorganic phosphor dopant (102) is desired to emit orange light, a phosphor emitting visible light (104) with a wavelength of about 590 nm to 620 nm is selected. In addition, in other examples, if the inorganic phosphor dopant (102) is desired to emit red light, a phosphor emitting visible light (104) with a wavelength of about 620 nm to 700 nm is selected.

[0047] In certain examples of the method for improving the color stability of a synthetic polymer, a synthetic polymer host material (101) comprises two or more inorganic phosphor dopants (102), wherein down-converted visible light (104) emitted by the two or more inorganic phosphor dopants (102) is combined to produce white light or off-white light. In certain examples of the method for improving the color stability of a synthetic polymer, a synthetic polymer host material comprises three or more inorganic phosphor dopants (102), wherein down-converted visible light (104) emitted by the three or more inorganic phosphor dopants (102) is combined to produce white light or off-white light. For example, an inorganic phosphor dopant (102) emitting blue visible light (104) having a wavelength of about 450 nm to 495 nm can be inserted into a synthetic polymer host material (101) having a second inorganic phosphor dopant (102) emitting yellow visible light (104) having a wavelength of about 570 nm to 590 nm. The combination of blue and yellow visible light (104) emitted by the first and second inorganic phosphor dopants (102) will produce white or off-white emission (white visible light (104)). In a similar manner, a first inorganic phosphor dopant (102) emitting blue visible light (104) having a wavelength of about 450nm to 495nm can be inserted into a synthetic polymer host material (101) having a second inorganic phosphor dopant (102) emitting green visible light (104) having a wavelength of about 495nm to 570nm and a third inorganic phosphor dopant (102) emitting red visible light (104) having a wavelength of about 620nm to 750nm. The combination of blue, green and red visible light (104) emitted by the first, second and third inorganic phosphor dopants (102) will produce white or off-white emission (white visible light (104)).

[0048] In some examples of the method for improving the color stability of synthetic polymers, the synthetic polymer is thermoplastic or thermosetting. In some examples, the synthetic polymer host material (101) is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine. In particular, it is known that fluorine strongly resists photooxidation due to its high electronegativity and the need to accept electrons. Therefore, in some examples, fluorinated synthetic polymers such as tetrafluoroethylene or polyvinyl fluoride can be used for the synthetic polymer in the method described herein. In addition, it is generally known that thermosetting polymers have a higher degree of crosslinking than other types of polymers, which makes them further resist photooxidation.

[0049] In certain examples of the method for improving the color stability of synthetic polymers, the inorganic phosphor dopant (102) is a metal oxide (106) or a metal fluoride (109) containing a rare earth ion (107) or a transition metal ion. The rare earth ion (107) or the transition metal ion is referred to as an "activator ion". As used herein, an "activator ion" is an ion added to the crystal structure as a dopant. The activator ion is surrounded by the host crystal ion and forms a luminescent center, where the excitation-emission process of the phosphor occurs. The wavelength emitted by the activator ion depends on the ion itself, its electronic configuration, and the crystal structure around it. In certain examples, the rare earth ion (107) is a lanthanide ion. In certain examples, the rare earth ion (107) is selected from Tm 3+ , Pr 3+ 、Ho 3+ , Er 3+ 、Sm 3+ 、Nd 3+ , Yb 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ 、Ce 3+ 、Ce 2+ , Tb 3+ , Tb 4+ 、Dy 3+ , Yb 3+ , Y 3+ He Lu 3+ or a combination thereof. In some examples, the inorganic phosphor dopant (102) is selected from Pr 3+ 、Ce 3 + 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+ or a mixture thereof. In some examples, the inorganic phosphor dopant is a metal oxide (106) containing a rare earth ion (107). In an example, the rare earth ion (107) and the metal oxide (106) are selected to prepare, for example, Figure 1A The inorganic phosphor dopant (102) shown emits light having a specific color and wavelength. For example, Eu doped in Y2O3 is expected to 3 + The emission wavelength is about 611nm red-orange visible light (104), and it is expected that Eu doped in InBO3 3+ The yellow visible light (104) with a wavelength of about 588 nm is emitted. In another example, BaMg2Al may be doped16 O 27 Eu 2+ , which is expected to emit blue visible light (104) having a wavelength of about 450 nm.

[0050] In certain examples of the method for improving the color stability of a synthetic polymer, the inorganic phosphor dopant (102) is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4, and NaGd4, and comprising a rare earth ion (107) or a transition metal ion. Such metal fluoride hosts are generally characterized by having a large band gap, structural defects that may act as electron traps, and anion defects, which make them useful in inorganic phosphors.

[0051] In certain examples of the method for improving the color stability of a synthetic polymer, the inorganic phosphor dopant (102) is a metal oxide (106) selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates or combinations thereof. In certain examples, the silicate is selected from the group consisting of pyroxene, cyclosilicates, silicate garnets, oxyorthosilicates and orthosilicates. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7, (Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 and Y2SiO5. Non-limiting examples of borates include YBO3 and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2, where M=Ba, Sr or Ca. Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12 、NaGdGeO4、Cd3Al2Ge3O 12 、CaTiO3、Ca 0.8 Zn 0.2 TiO3 and Ca2Zn4Ti 15 O 36 Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O4, CaAl2O4, SrAl2O4, and Sr4Al14 O 25 .

[0052] In some examples, the synthetic polymer host material (101) comprises two different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant (102) is a metal oxide (106) or a metal fluoride (109) containing a rare earth ion (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). In some examples, the synthetic polymer host material (101) comprises two different inorganic phosphor dopants (102), wherein the two different inorganic phosphor dopants (102) are metal oxides (106) containing rare earth ions (107). As an example, the synthetic polymer host material (101) may include a first inorganic phosphor dopant (102) of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant (102) of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light will together produce white or off-white visible light (104).

[0053] In some examples, the synthetic polymer host material (101) includes three different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant (102) is a metal oxide (106) or a metal fluoride (109) containing a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some examples, the synthetic polymer host material (101) may include BaMg2Al2O3 that emits blue visible light (104) at a wavelength of about 450 nm. 16 O 27 The first inorganic phosphor dopant (102) of Y2SiO5:Tb(III) emitting green visible light (104) with a wavelength of about 545 nm, and the third inorganic phosphor dopant (102) of Y2O3:Eu(III) emitting red visible light (104) with a wavelength of about 611 nm. The combined visible light will produce white or off-white visible light (104).

[0054] In certain examples of the method for improving the color stability of a synthetic polymer composition, the synthetic polymer composition is a substrate or surface located in an aircraft interior. In certain other examples, the synthetic polymer composition is a substrate or surface located in a hospital or other medical institution, a school, a gym, or a car.

[0055] In certain examples of the method for improving the color stability of a synthetic polymer composition, a synthetic polymer host material (101) comprising one or more inorganic phosphor dopants (102) is exposed to UV light (103) for a time sufficient to charge the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101). In certain examples, the time sufficient to charge the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) is about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 3 hours, 5 hours, 7 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0056] The one or more inorganic phosphor dopants (102) absorb UV light and emit the UV light (103) as down-converted visible light (104) for a period of time typically on the order of nanoseconds. In addition, in examples, the phosphor absorbs energy and does not release the light immediately. Instead, in examples, the energy is dissipated to the lowest excited state in picoseconds before emission. In certain examples, by applying continuous irradiation, for example, the one or more inorganic phosphor dopants (102) continuously absorb UV light (103) and emit the UV light as down-converted visible light (104).

[0057] In certain other examples, persistent phosphors may be applied in the above methods to improve the color stability of synthetic polymer compositions. Persistent phosphors differ from ordinary conversion phosphors in that they exhibit light emission that lasts from seconds to hours after excitation ceases. The reason for this delayed emission is their ability to store energy in the material, possibly at defects other than the luminescent "activator" ions. These defects are called wells because charge carriers originating from the luminescent ions are locally trapped at the defects. When sufficient energy is provided to the trapped charge, it will be released. After recombination at the luminescent ion, it will produce a delayed emission commonly known as afterglow. The time span of the afterglow can be adjusted because it depends on the so-called depth of the well, which is usually detected by thermoluminescence. For example, it is generally understood that shallow wells are easy to empty, while deep wells are difficult to empty at room temperature; a portion of the trapped electrons remain stored there. If the well is too deep, the trapped electrons cannot escape, preventing a continuous afterglow. Thermoluminescence can be used to assess the well depth. In fact, the thermoluminescence glow curve represents the relationship between the intensity of the emitted light and the temperature; each glow peak is associated with a recombination center and is associated with a specific well. Glow curves can provide useful information for materials. For example, activation energy and escape frequency factor can be calculated from the glow curve. Many methods can be used to calculate well parameters based on the kinetic series of the glow peak, such as the initial rise method and variable heating rate. Based on the glow curve, the luminescence efficiency of the material can be obtained.

[0058] The change of the structure-luminescence property of the material can be observed by the modification of its glow curve. For example, the reduction of the thermoluminescence intensity can sometimes be attributed to the inhibition of the well. In other examples, the luminous efficiency of the material can be increased after impurities (such as other ions) are added to the phosphor. The presence of such impurities can modify the well distribution and deepen the well sites caused by the modification of the energy gap in the phosphor. The thermoluminescence glow curve can be obtained using a thermoluminescence measuring instrument such as a FJ-427ATL meter.

[0059] In certain other examples, the electronic transitions of a phosphor may be characterized as "forbidden". Forbidden transitions are spectral lines associated with the absorption or emission of photons by a nucleus or atom that undergoes a transition that is not permitted by a particular selection rule, but is permitted if the approximation associated with the rule is not performed. For example, under the usual approximation (e.g., the electric dipole approximation for interaction with light), the process cannot occur, but under a higher level of approximation (i.e., the magnetic dipole), the process is allowed but at a slower rate. An example of such a forbidden transition is observed in phosphorescent materials, which absorb light and form an excited state whose decay involves a spin flip, which is forbidden by the electric dipole transition. The result is a slow emission of light over minutes or hours. In practice, "forbidden" transitions occur at a much slower rate than "allowed" transitions. "Allowed" transitions are transitions that: obey the appropriate (1) spin and (2) Laporte (orbital) selection rules; exhibit a change in parity (symmetry) during the transition; emit a photon with an energy that matches the gap between the ground and excited states; and which exhibit a change in dipole moment. The allowed spin selection rules dictate that the spin orientation should not change (i.e., no spin reversal occurs during an electronic transition). According to the Laporte selection rules, transitions between similar atomic orbitals, such as ss, pp, dd, or ff transitions, are forbidden in a centrosymmetric environment. Even when a transition may be forbidden, it is often coupled to vibrational factors that reduce, for example, the molecular symmetry of the system and cause some previously forbidden transitions to be allowed due to the reduced symmetry. This generally results in weaker allowed transitions and in reduced transition rates. Typical emission lifetimes for materials that undergo forbidden transitions can be milliseconds or even seconds.

[0060] As described above, in certain examples, one or more inorganic phosphor dopants (102) can be used to tune the emission to longer or shorter wavelengths and still produce white light.

[0061] In certain examples of the method for improving the color stability of a synthetic polymer composition, the synthetic polymer host material (101) is a thermoplastic material, wherein the thermoplastic material is polyvinyl fluoride; the synthetic polymer host material (101) contains two inorganic phosphor dopants (102), wherein the first inorganic phosphor dopant (102) is Y2SiO5:Ce(III), which emits blue visible light (104) with a wavelength of about 400 nm, and the second inorganic phosphor dopant (102) is InBO3:Eu(III), which emits yellow visible light (104) with a wavelength of about 588 nm. The phosphor in the thermoplastic host material is exposed to UV light (103) using a xenon UV rod for about 10 minutes, and then emits visible light (104), and the visible light combines to produce white visible light (104).

[0062] III. Synthetic polymer compositions with improved color stability

[0063] In certain examples, the subject matter described herein relates to synthetic polymer compositions having improved color stability, comprising:

[0064] A synthetic polymer host material (101) containing one or more inorganic phosphor dopants (102), wherein the one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) emit down-converted visible light (104) when exposed to UV light (103); and

[0065] Therein, the synthetic polymer composition exhibits mechanical and flammability properties comparable to synthetic polymer compositions that do not contain the one or more inorganic phosphor dopants.

[0066] As used herein, a synthetic polymer composition comprising one or more inorganic phosphor dopants has mechanical and flammability properties suitable for the intended use of the material when the synthetic polymer composition exhibits mechanical and flammability properties that are "comparable" to a synthetic polymer composition. As used herein, the mechanical properties of a synthetic polymer composition may refer to its impact durability, tensile strength, and chemical resistance, among others. In certain instances, the presence of the one or more inorganic phosphor dopants (102) may enhance the flammability performance of the synthetic polymer host material (101).

[0067] In certain examples of synthetic polymer compositions with improved color stability, the synthetic polymer host material (101) is thermoplastic or thermosetting. In certain examples, the synthetic polymer host material (101) is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine. In particular, fluorine is known to strongly resist photooxidation due to its high electronegativity and need to accept electrons. Therefore, in certain examples, fluorinated synthetic polymers such as tetrafluoroethylene or polyvinyl fluoride can be used in the synthetic polymer in the methods described herein.

[0068] In certain examples of synthetic polymer compositions with improved color stability, the inorganic phosphor dopant (102) is a metal oxide (106) or metal fluoride (109) containing a rare earth ion (107) or a transition metal ion. In certain examples, the rare earth ion (107) is a lanthanide ion. In certain examples, the rare earth ion (107) is selected from the group consisting of Tm 3+ , Pr 3 + 、Ho 3+ , Er 3+ 、Sm 3+ 、Nd 3+ , Yb 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ 、Ce 3+ 、Ce 2+ , Tb 3+ , Tb 4+ 、Dy 3+ , Yb 3+ , Y 3+ He Lu 3+ or a combination thereof. In some embodiments, the inorganic phosphor dopant is selected from the group consisting of Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+ or a mixture thereof. In some embodiments, the inorganic phosphor dopant is a metal oxide (106). The rare earth ion (107) is combined with the metal oxide (106) to prepare a phosphor that emits visible light (104) of a specific color and wavelength. For example, Eu doped in Y2O3 3+It is expected to emit red-orange visible light (104) with a wavelength of about 611 nm, and Eu doped in InBO3 3+ It is expected to emit yellow visible light (104) having a wavelength of about 588 nm. In another example, BaMg2Al may be doped 16 O 27 Eu 2 + , which is expected to emit blue visible light (104) having a wavelength of about 450 nm.

[0069] In certain examples of synthetic polymer compositions with improved color stability where the inorganic phosphor dopant (102) is a metal oxide (106), the metal oxide (106) is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates or combinations thereof. Such metal oxides (106) are ceramic materials and therefore exhibit multiple advantages, including chemical, thermal and photochemical stability, due to their strong lattice structure. In certain examples, the silicate is selected from the group consisting of pyroxene, cyclosilicates, silicate garnets, oxyorthosilicates and orthosilicates. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7, (Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 and Y2SiO5. Non-limiting examples of borates include YBO3 and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2, where M=Ba, Sr or Ca. Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12 、NaGdGeO4、Cd3Al2Ge3O 12 、CaTiO3、Ca 0.8 Zn 0.2 TiO3 and Ca2Zn4Ti 15 O 36 Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O4, CaAl2O4, SrAl2O4, and Sr4Al 14 O25 .

[0070] In certain examples of synthetic polymer compositions with improved color stability, the inorganic phosphor dopant (102) is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4, and NaGd4, and comprising rare earth ions (107) or transition metal ions. Such metal fluoride hosts are generally characterized by having large band gaps, structural defects that may act as electron traps, and anion defects, which make them useful in inorganic phosphors.

[0071] In certain examples of synthetic polymer compositions with improved color stability, the synthetic polymer material comprises two different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) comprising a rare earth ion (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). In certain examples, the synthetic polymer material comprises two different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) comprising a rare earth ion (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some instances, the synthetic polymer host material (101) may include a first inorganic phosphor dopant of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light will together produce white or off-white visible light (104).

[0072] In some instances, the synthetic polymer material comprises three different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) comprising a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). In some instances, the synthetic polymer material comprises three different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) comprising a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, the synthetic polymer host material (101) may comprise BaMg2Al2O3 emitting blue visible light (104) having a wavelength of about 450 nm. 16 O 27The first inorganic phosphor dopant of Y2SiO5:Tb(III) emits green visible light (104) at a wavelength of about 545 nm, and the third inorganic phosphor dopant of Y2O3:Eu(III) emits red visible light (104) at a wavelength of about 611 nm. The combined visible light will produce white or off-white visible light (104).

[0073] In certain examples of synthetic polymer compositions with improved color stability, the synthetic polymer composition comprises a substrate or surface located inside an aircraft. Other non-limiting examples of other places where the substrate or surface may be placed include a gym, a school, a health care facility, or a car.

[0074] In certain examples of synthetic polymer compositions, one or more inorganic phosphor dopants (102) in the synthetic polymer host material (101) emit down-converted visible light (104) when exposed to UV light (103). In certain other examples of synthetic polymer compositions, the one or more inorganic phosphor dopants (102) emit light having a wavelength of about 200 nm to 700 nm. In other examples, the one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength of about 400nm to 500nm, about 620nm to 700nm, about 590nm to 620nm, about 570nm to 590nm, about 495nm to 570nm, about 390nm to 450nm, about 380nm to 600nm, about 350nm to 460nm, about 600nm to 700nm, about 450nm to 600nm, about 200nm to 280nm, about 450nm to 495nm, about 200nm to 270nm, about 200nm to 250nm, about 225nm to 250nm, about 200nm to 225nm, about 200nm to 275nm, or about 225nm to 275nm.

[0075] In certain examples of the synthetic polymer composition, the synthetic polymer host material (101) is a thermoplastic material, wherein the thermoplastic material is polyvinyl fluoride; the host material contains two inorganic phosphor dopants (102), wherein the first inorganic phosphor dopant is Y2SiO5:Ce(III) emitting blue visible light (104) with a wavelength of about 400nm, and the second inorganic phosphor dopant is InBO3:Eu(III) emitting yellow visible light (104) with a wavelength of about 588nm.

[0076] IV. Methods of Preparing Synthetic Polymer Compositions Having Improved Color Stability

[0077] In certain instances, the subject matter described herein relates to a method for preparing a synthetic polymer composition having improved color stability, comprising: contacting a synthetic polymer host material (101) with one or more inorganic phosphor dopants (102) to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants (102) in the inorganic phosphor-doped synthetic polymer material are capable of absorbing UV light (103) and then emitting the UV light as down-converted visible light (104).

[0078] In certain examples of the method for preparing a synthetic polymer composition having improved color stability, the one or more inorganic phosphor dopants (102) are capable of emitting UV light as down-converted visible light (104). In certain other examples of the method for preparing a synthetic polymer composition having improved color stability, the one or more inorganic phosphor dopants (102) emit light having a wavelength of about 200 nm to 700 nm. In other examples, the one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength of about 400nm to 500nm, about 620nm to 700nm, about 590nm to 620nm, about 570nm to 590nm, about 495nm to 570nm, about 390nm to 450nm, about 380nm to 600nm, about 350nm to 460nm, about 600nm to 700nm, about 450nm to 600nm, about 200nm to 280nm, about 450nm to 495nm, about 200nm to 270nm, about 200nm to 250nm, about 225nm to 250nm, about 200nm to 225nm, about 200nm to 275nm, or about 225nm to 275nm.

[0079] In certain examples of the method for preparing a synthetic polymer composition having improved color stability, the synthetic polymer host material (101) is a thermoplastic or a thermoset. In certain examples, the synthetic polymer host material (101) is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

[0080] In certain embodiments of the method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) containing a rare earth ion (107) or a transition metal ion. In certain embodiments, the rare earth ion (107) is a lanthanide ion. In certain embodiments, the rare earth ion (107) is selected from the group consisting of Tm 3+ , Pr3+ 、Ho 3+ , Er 3+ 、Sm 3+ 、Nd 3+ , Yb 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ 、Ce 3+ 、Ce 2+ , Tb 3+ , Tb 4+ 、Dy 3+ , Yb 3+ He Lu 3+ or a combination thereof. In some embodiments, the inorganic phosphor dopant is selected from the group consisting of Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+ or a metal oxide (106) of a rare earth ion (107) selected from the group consisting of a mixture thereof.

[0081] In certain examples of the method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) is a metal oxide (106), wherein the metal oxide (106) is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates or combinations thereof. In certain examples, the silicate is selected from the group consisting of pyroxene, cyclosilicates, silicate garnets, oxyorthosilicates and orthosilicates. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7, (Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 and Y2SiO5. Non-limiting examples of borates include YBO3, InBO3, and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2, where M is Ba, Sr, or Ca. Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12、NaGdGeO4、Cd3Al2Ge3O 12 、CaTiO3、Ca 0.8 Zn 0.2 TiO3 and Ca2Zn4Ti 15 O 36 Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O4, CaAl2O4, SrAl2O4, and Sr4Al 14 O 25 .

[0082] In certain examples of methods for preparing synthetic polymer compositions having improved color stability, the synthetic polymer material comprises two different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) comprising a rare earth ion (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). In certain examples, the synthetic polymer material comprises two different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) comprising a rare earth ion (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some instances, the synthetic polymer host material (101) may include a first inorganic phosphor dopant of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light will together produce white or off-white visible light (104).

[0083] In certain examples of the method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4 and NaGd4, and comprising a rare earth ion (107) or a transition metal ion. Such metal fluoride hosts are generally characterized by having large band gaps, structural defects that may act as electron traps, and anion defects, which make them useful in inorganic phosphors.

[0084] In certain examples of methods for preparing synthetic polymer compositions having improved color stability, the synthetic polymer material comprises three different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) comprising a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). In certain examples, the synthetic polymer material comprises three different inorganic phosphor dopants (102), wherein each inorganic phosphor dopant is a metal oxide (106) comprising a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in certain examples, the synthetic polymer host material (101) may include BaMg2Al2O3 emitting blue visible light (104) at a wavelength of about 450 nm. 16 O 27 The first inorganic phosphor dopant (102) of Y2SiO5:Tb(III) emitting green visible light (104) with a wavelength of about 545 nm, and the third inorganic phosphor dopant (102) of Y2O3:Eu(III) emitting red visible light (104) with a wavelength of about 611 nm. The combined visible light will produce white or off-white visible light (104).

[0085] In certain examples of a method for preparing a synthetic polymer composition having improved color stability, a synthetic polymer host material (101) is a thermoplastic material, wherein the thermoplastic material is polyvinyl fluoride; the host material comprises two inorganic phosphor dopants (102), wherein the first inorganic phosphor dopant (102) is Y2SiO5:Ce(III) which emits blue visible light (104) at a wavelength of approximately 400 nm; and the second inorganic phosphor dopant (102) is InBO3:Eu(III) which emits yellow visible light (104) at a wavelength of approximately 588 nm.

[0086] In an example, the synthetic polymer composition prepared exhibits mechanical and flammability properties comparable to those of a synthetic polymer composition that does not contain one or more inorganic phosphor dopants. For example, ASTM E1354 (ASTM E-1354) is a fire test-response standard for measuring the response of a material to controlled levels of radiant heat, which can be used to evaluate the flammability properties of a material. Other methods for analyzing the flammability properties of a material include ASTM D7309-21b and ASTM E2058-19. A general purpose testing machine can be used to evaluate the mechanical properties of a material to measure, for example, tensile strength or compressive strength. In addition, a hydraulic fatigue tester can be used to measure the fatigue of a material.

[0087] In certain examples of a method for preparing a synthetic polymer composition having improved color stability, the step of contacting a synthetic polymer host material (101) with one or more inorganic phosphor dopants (102) to prepare an inorganic phosphor-doped synthetic polymer material can be carried out for a time sufficient to incorporate the one or more inorganic phosphor dopants (102) into the synthetic polymer host material (101).

[0088] Methods for preparing solid-state phosphors are known in the art. See, for example, Broxtermann et al., ECS Journal of Solid State Science and Technology, 6 (4) R47-R52 (2017); and Poelman et al., Journal of Applied Physics 128, 240903 (2020). In an example, a metal oxide (or metal fluoride) host material and a rare earth oxide are weighed so that a certain amount of rare earth ions are substituted or doped into the metal oxide (or metal fluoride) lattice. The amount of ion addition can be determined by calculating the suggested stoichiometry of the material and then weighing an appropriate amount of raw materials using dimensional analysis. The metal oxide powder is fully ground using a mortar and pestle to maximize contact between particles in the mixture. After being placed in a suitable crucible (usually alumina), the mixture is heated in a tubular or muffle furnace to a temperature sufficient to cause a solid-state reaction but below the melting temperature of the final compound. From a temperature of about 200-300°C below the melting temperature, the grain size of the final compound increases strongly. This heating process is called sintering. Sintering usually results in very dense and strongly agglomerated materials that cannot be used directly as phosphors. Therefore, post-synthesis grinding, either manually or using a ball mill, is usually required.

[0089] Ball milling is a mechanical method of reducing particle size by mechanical impact and friction. Typically, the powder is placed in a grinding jar together with a number of hard grinding balls (usually Al2O3 or ZrO2) and a solvent to obtain a slurry. The grinding jar is then moved so that maximum friction is achieved. Similar to manual grinding with a mortar and pestle, the effectiveness of the process is highly dependent on the size and hardness of the raw material.

[0090] For the above solid-state synthesis, the atmosphere used for heating may vary depending on the host material. In the case of oxides, air may generally be applied. However, some dopants, particularly europium, may oxidize in the oxygen lattice while being heated in oxygen, resulting in the formation of fully oxidized Eu 3+ Dopant. If Eu 2+ is the preferred valence state of the dopant, additional heat treatment in a reducing atmosphere such as helium or argon may be required.

[0091] Other methods for preparing inorganic phosphor dopants (102) include sol-gel synthesis, colloidal synthesis and coprecipitation. For example, in the sol-gel process, the powder is weighed and dissolved in a concentrated acid, such as HNO3 (e.g., 70 wt%), and then diluted with deionized water. The solution can then be cooled to room temperature and added dropwise to a cold saturated aqueous solution of another acid (e.g., oxalic acid). The solid material is then precipitated and then washed with deionized water and other polar solvents (e.g., acetone, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol or methanol). The solid material is then calcined for several hours at a temperature of about 1000° C. to 1200° C., followed by intermittent grinding and sintering. In some instances, after weighing and mixing, the metal oxide host powder and rare earth oxide powder are directly placed in a furnace at 1000-1100° C. for 2-48 hours.

[0092] The prepared solid-state phosphor dopant material is then inserted into the synthetic polymer substrate main material. The synthetic polymer substrate main material can be purchased from commercial suppliers, such as Dupont or Sigma. The solid-state phosphor material is a powder and can be incorporated into the synthetic polymer substrate main material by melting the polymer substrate and then mixing in the solid-state phosphor material. If two or more inorganic phosphor dopants (102) are incorporated into the synthetic polymer substrate main material, two or more inorganic phosphor dopant powders can be first mixed and then dispersed throughout the synthetic polymer substrate main material. The mixing of the powder in the entire substrate main material can be promoted, for example, by further heating the material and / or by using a mixing blade.

[0093] A solid state phosphor dopant may be incorporated into the synthetic polymer host material (101) in an amount sufficient to maintain the color stability of the synthetic polymer host.

[0094] After incorporating the solid-state phosphor dopant into the synthetic polymer host material (101), the inorganic phosphor doped synthetic polymer host material (101) is cured. Curing can be performed, for example, in air at room temperature. Curing hardens the inorganic phosphor doped synthetic polymer host material (101) together with the inorganic phosphor dopant uniformly dispersed throughout the substrate.

[0095] In addition, the present disclosure includes examples according to the following clauses:

[0096] Clause 1. A method for improving the color stability of a synthetic polymer composition, comprising:

[0097] exposing a synthetic polymer host material comprising one or more inorganic phosphor dopants to UV light;

[0098] The one or more inorganic phosphor dopants in the synthetic polymer host material absorb the UV light and then emit the UV light as down-converted visible light.

[0099] Clause 2. The method of Clause 1, wherein the one or more inorganic phosphor dopants absorb the UV light to reduce photo-oxidation of the synthetic polymer host material.

[0100] Clause 3. The method of Clause 1 or 2, wherein the visible light emitted by the one or more inorganic phosphor dopants produces a brighter appearance for the synthetic polymer composition.

[0101] Clause 4. The method of any one of clauses 1-3, wherein the synthetic polymer host material comprises two or more inorganic phosphor dopants, wherein down-converted visible light emitted by the two or more inorganic phosphor dopants combines to produce white light or off-white light.

[0102] Clause 5. The method of any one of clauses 1-4, wherein the synthetic polymer host material comprises three or more inorganic phosphor dopants, wherein down-converted visible light emitted by the three or more inorganic phosphor dopants combines to produce white light or off-white light.

[0103] Clause 6. The method of any of Clauses 1-5, wherein the UV light absorbed by the one or more inorganic phosphor dopants has a wavelength of about 160 nm to 380 nm.

[0104] Clause 7. The method of Clause 6, wherein the UV light absorbed by the one or more inorganic phosphor dopants has a wavelength of approximately 222 nm, 254 nm, or 275 nm.

[0105] Clause 8. The method of any of Clauses 1-7, wherein the synthetic polymer body material is a thermoplastic or a thermoset.

[0106] Item 9. A method as described in Item 8, wherein the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

[0107] Clause 10. The method of any one of clauses 1 to 9, wherein the one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions selected from the group consisting of Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu2+ , Gd 3+ , Tb 3+ and Dy 3+ or a combination thereof.

[0108] Clause 11. The method of Clause 10, wherein the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof.

[0109] Clause 12. A synthetic polymer composition comprising:

[0110] a synthetic polymer host material comprising one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the synthetic polymer host material emit down-converted visible light when exposed to UV light; and

[0111] Therein, the synthetic polymer composition exhibits mechanical and flammability properties comparable to synthetic polymer compositions that do not contain the one or more inorganic phosphor dopants.

[0112] Clause 13. The synthetic polymer composition of Clause 12, wherein the UV light has a wavelength of about 160 nm to 380 nm.

[0113] Clause 14. The synthetic polymer composition of Clause 13, wherein the UV light has a wavelength of about 222 nm, 254 nm, or 275 nm.

[0114] Clause 15. The synthetic polymer composition of any of Clauses 12-14, wherein the synthetic polymer body material is a thermoplastic or a thermoset.

[0115] Item 16. A synthetic polymer composition as described in Item 15, wherein the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

[0116] Clause 17. A synthetic polymer composition as described in any of Clauses 12-16, wherein the one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions, wherein the rare earth ions are selected from Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+or a combination thereof.

[0117] Clause 18. The synthetic polymer composition of Clause 17, wherein the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates, or combinations thereof.

[0118] Clause 19. The synthetic polymer composition of any of Clauses 12-18, wherein the polymer composition has improved color stability compared to a coating without the one or more inorganic phosphor dopants subjected to UV exposure.

[0119] Clause 20. A method of preparing a synthetic polymer composition comprising:

[0120] A synthetic polymer host material is contacted with one or more inorganic phosphor dopants to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material are capable of absorbing UV light and then emitting the UV light as down-converted visible light.

[0121] Clause 21. The method of Clause 20, wherein the UV light absorbed by the one or more inorganic phosphor dopants has a wavelength of about 160 nm to 380 nm.

[0122] Clause 22. The method of Clause 21, wherein the UV light absorbed by the one or more inorganic phosphor dopants has a wavelength of approximately 222 nm, 254 nm, or 275 nm.

[0123] Clause 23. The method of any one of Clauses 20 to 22, wherein the synthetic polymer body material is a thermoplastic or a thermoset.

[0124] Item 24. A method as described in Item 23, wherein the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

[0125] Clause 25. The method of any one of clauses 20-24, wherein the one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions selected from the group consisting of Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2 + , Gd 3+ , Tb 3+and Dy 3+ or a combination thereof.

[0126] Clause 26. The method of Clause 25, wherein the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof.

[0127] Clause 27. The method of any of Clauses 20-26, wherein the synthetic polymer composition produced exhibits mechanical and flammability properties comparable to synthetic polymer compositions that do not contain the one or more inorganic phosphor dopants.

[0128] Clause 28. The method of any of Clauses 20-27, wherein the polymer composition has improved color stability compared to a coating without the one or more inorganic phosphor dopants subjected to UV exposure.

[0129] The following examples are offered by way of illustration and not limitation.

[0130] Example

[0131] Preparation of synthetic polymer materials with improved color stability

[0132] Step 1: Y 2-x SiO5: x Preparation of Ce phosphor powder

[0133] Analytical grade Y(NO3)3·6H2O, Na2SiO3·9H2O, Ce(NO3)3 and NaOH were purchased from Sigma Aldrich. First, Y(NO3)3·6H2O, Na2SiO3·9H2O, Ce(NO3)3 and NaOH were added to a 100 mL glass beaker in a certain amount so that the final product would produce 0.75-2% cerium substitution on the Y site in the Y2SiO5 lattice. After stirring for 30 minutes, the solution was poured into a 70 mL hydrothermal autoclave. The autoclave was sealed and placed in a microwave digestion system. During the reaction, the autoclave temperature was maintained at 200°C. After 20 minutes, the autoclave was removed from the microwave hydrothermal device and naturally cooled to room temperature. Then, the precipitate was filtered, washed with deionized water and isopropanol, and dried at 80°C for 1 hour. Thereafter, the inorganic phosphor dopant (102)Y was heated at 700°C and 900°C, respectively. 2-x SiO5: x Ce powder.

[0134] The prepared Y 2-x SiO5: x Ce inorganic phosphor dopant (102). FullProf was used to analyze the crystal structure to verify Y 2-x SiO5: xCe / Y sites are mixed in the Ce crystal structure.

[0135] Step 2: In 1-x BO3: x Preparation of Eu phosphor powder

[0136] Indium(III) nitrate (99.9%), tri-n-butyl borate (98%), and 12 H 27 BO3), citric acid (C6H8O7) and europium nitrate (Eu(N3O)9·5H2O). First, stoichiometric amounts of indium nitrate and tri-n-butyl borate were dissolved in distilled water. A certain amount of europium nitrate was added to the solution so that the final product would produce 0.75-2% europium substitution on the In sites in the InBO3 lattice. Then, sufficient citric acid was added to the solution as a chelating agent. The molar ratio of citric acid to total metal ions used was 1:1. The powder was dried in an oven at 120°C for 10 hours. Thereafter, the powder was calcined at 700°C in air for 3 hours.

[0137] The prepared In was analyzed by powder X-ray diffraction 1-x BO3: x Eu inorganic phosphor dopant (102). The crystal structure was solved using FullProf to verify the In / Eu site mixing in the InBO3 crystal structure.

[0138] Step 3: Y 2-x SiO5: x Ce and In 1-x BO3: x Preparation of Eu-doped Polyvinyl Fluoride

[0139] Polyvinyl fluoride (Dupont) was heated to about 180° C. in an argon atmosphere to melt the material. The inorganic phosphor dopant (102) prepared in steps 1 and 2, namely Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor powders were mixed together and ground using an agate mortar and pestle. The mixed phosphor powders were then thoroughly mixed with molten polyvinyl fluoride to make Y 2- x SiO5: x Ce and In 1-x BO3: x Eu is uniformly dispersed throughout the polyvinyl fluoride host material. The doped polyvinyl fluoride is then cured to form a cured Y 2-x SiO5: x Ce and In 1-x BO3: x Eu-doped polyvinyl fluoride substrate.

[0140] In some instances, Y 2-x SiO5: x Ce and In1-x BO3: x Eu-doped polyvinyl fluoride substrate material can be formed using, for example, a mold while it is curing. The mold can assist in forming the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu-doped polyvinyl fluoride substrates are constructed into useful products such as cabinets, countertops, wall coverings or covers for various household, healthcare, automotive or aviation products. 2-x SiO5: x Ce and In 1-x BO3: x After forming the Eu-doped polyvinyl fluoride substrate, the material can be easily shaped and reformed, for example using a saw, sandpaper or a suitable mold.

[0141] Y 2-x SiO5: x Ce and In 1-x BO3: x Color stability of Eu-doped polyvinyl fluoride

[0142] The Y prepared in step 3 2-x SiO5: x Ce and In 1-x BO3: x Eu doped polyvinyl fluoride material is exposed to UV light (103) having a wavelength of about 160 nm to 380 nm. This is the Y in the polyvinyl fluoride host matrix. 2-x SiO5: x Ce and In 1-x BO3: x The Eu phosphor radiates excitation energy. The substrate is exposed to UV light for about 2 to 10 minutes to make the Y 2-x SiO5: x Ce and In 1-x BO3: x The Eu phosphor is charged. Then the UV lamp is turned off. Then, the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor emits visible light (104) for about 3 nanoseconds to about 15 minutes. 2-x SiO5: x Ce phosphor emits blue light with a wavelength of about 400nm, In 1- x BO3: xThe Eu phosphor emits yellow visible light (104) at a wavelength of approximately 588 nm. The combined visible light from the phosphors produces white visible light (104), creating a brighter appearance for the polyethylene material.

[0143] In another example, the UV light (103) can be a pulsed xenon UV device having a wavelength of about 222 nm, 254 nm, or 275 nm and is used as an excitation source to excite the inorganic phosphor dopant (102) (i.e., Y 2- x SiO5: x Ce and In 1-x BO3: x Eu phosphor).

[0144] Comparative Example: Flammability

[0145] ASTM E1354 (ASTM E-1354) is a fire test-response standard that measures the response of materials to controlled levels of radiant heat. The test method is often used to test new products still in development, to demonstrate compliance of products entering the market, and for quality control purposes. ASTM E1354 utilizes a cone calorimeter and oxygen consumption calorimetry to determine the heat released from the products of combustion. The heat release rate (RHR) and the heat released by the products are direct factors in fire severity, flame spread, and fire growth.

[0146] ASTM E1354 testing is performed using a cone calorimeter. The main components of the cone calorimeter are a cone furnace for generating radiant heat, a spark igniter for igniting the test sample, a load cell for measuring mass loss, and an exhaust system for making smoke measurements and collecting gas samples. The sampled gas passes through an oxygen analyzer to determine the heat release.

[0147] In this embodiment, the cone calorimetry test of the polyvinyl fluoride main material was performed using ASTM E1354 and compared with Y 2- x SiO5: x Ce and In 1-x BO3: x Eu doped polyvinyl fluoride material was compared. Briefly, the test sample was placed on top of the load cell and below the conical furnace. The spark igniter was moved over the sample surface until sustained combustion was achieved over the entire sample surface. Testing can also be performed without the spark igniter. The combustion products are pulled through the exhaust system where a laser is passed through the duct to measure the smoke and the gases are sampled and sent to an oxygen analyzer. Testing continues until two minutes after one of the following conditions: last sign of combustion, mass loss rate drops below 150g / m 2, the sample mass has been completely consumed, the oxygen concentration has returned to the value before the test, or 60 minutes have passed.

[0148] The ASTM E1354 report obtained from the above test procedure shows that the polyvinyl fluoride main material and Y 2-x SiO5: x Ce and In 1-x BO3: x Eu-doped polyvinyl fluoride materials all exhibit comparable properties, including ignition time, flame extinction time, peak heat release rate, time to reach peak heat release rate, average heat release rate, total heat release, average effective heat of combustion, average smoke extinction area, and time to reach peak smoke extinction area.

[0149] Supplementary Example: Blending phosphor with polyacrylate

[0150] Polyacrylate was purchased from Alfa. Y prepared in steps 1 and 2 above was added 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor powder was ground and mixed together using an agate mortar and pestle. The polyacrylate was heated to about 125°C to slightly melt the material. The phosphor powder was added to the molten polyacrylate and mixed using a mixing blade for about 10 minutes to evenly disperse the powder throughout the polyacrylate host material. The material was then cured in air.

[0151] Y 2-x SiO5: x Ce and In 1-x BO3: x Color stability of Eu-doped polyacrylates

[0152] The Y prepared above 2-x SiO5: x Ce and In 1-x BO3: x The Eu-doped polyacrylate material is exposed to UV light (103) having a wavelength of about 160 nm to 380 nm. This is the Y 2-x SiO5: x Ce and In 1-x BO3: x The Eu phosphor radiates excitation energy. The substrate is exposed to UV light for about 2 to 10 minutes to make the Y 2-x SiO5: x Ce and In 1-x BO3: x The Eu phosphor is charged. Then the UV lamp is turned off. Then, the Y2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor emits visible light (104) for about 3 nanoseconds to about 15 minutes. 2-x SiO5: x Ce phosphor emits blue light with a wavelength of about 400nm, In 1-x BO3: x The Eu phosphor emits yellow light at a wavelength of about 588 nm. The combined visible light from the phosphors produces white light, creating a brighter appearance for the polyacrylate material.

[0153] Efforts have been made to ensure accuracy with respect to numbers used (eg amounts, temperature, etc.) but some experimental errors and deviations should be accounted for.

[0154] One skilled in the art will recognize many methods and materials similar or equivalent to those described herein that can be used to practice the subject matter described herein.The present disclosure is in no way limited to the methods and materials described.

[0155] Where a numerical range is provided, unless the context clearly dictates otherwise, it is understood that the upper and lower limits of the range and any other stated value or intervening value in the stated range are included to the tenth of the unit of the lower limit. The upper and lower limits of these smaller ranges, which may be independently included in the smaller ranges, are also included, subject to any specifically excluded limits in the stated range. Where the stated range includes one or both of these limits, then ranges excluding one or both of those included limits are also included.

[0156] Many modifications and other examples set forth herein will occur to those skilled in the art having benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it should be understood that the subject matter is not limited to the specific examples disclosed, and modifications and other examples are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for improving the color stability of a synthetic polymer composition, comprising: exposing a synthetic polymer host material comprising one or more inorganic phosphor dopants to UV light; The one or more inorganic phosphor dopants in the synthetic polymer host material absorb the UV light and then emit the UV light as down-converted visible light.

2. The method of claim 1, wherein: Absorption of the UV light by the one or more inorganic phosphor dopants reduces photo-oxidation of the synthetic polymer host material.

3. The method according to claim 1 or 2, wherein: The visible light emitted by the one or more inorganic phosphor dopants creates a brighter appearance for the synthetic polymer composition.

4. The method according to any one of claims 1 to 3, wherein: The synthetic polymer main material contains two or more inorganic phosphor dopants, and the down-converted visible light emitted by the two or more inorganic phosphor dopants is combined to produce white light or gray-white light, and / or the synthetic polymer main material contains three or more inorganic phosphor dopants, and the down-converted visible light emitted by the three or more inorganic phosphor dopants is combined to produce white light or gray-white light.

5. The method of claim 1, wherein: The UV light absorbed by the one or more inorganic phosphor dopants has a wavelength of about 160 nm to 380 nm.

6. The method of claim 1, wherein: The synthetic polymer host material is a thermoplastic or a thermoset, and optionally, the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

7. The method according to any one of claims 1 to 7, wherein: The one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions, wherein the rare earth ions are selected from Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+ or a combination thereof, and / or optionally, the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates or a combination thereof.

8. A synthetic polymer composition comprising: A synthetic polymer host material comprising one or more inorganic phosphor dopants, wherein: The one or more inorganic phosphor dopants in the synthetic polymer host material emit down-converted visible light when exposed to UV light; and Therein, the synthetic polymer composition exhibits mechanical and flammability properties comparable to synthetic polymer compositions that do not contain the one or more inorganic phosphor dopants.

9. The synthetic polymer composition of claim 9, wherein: The synthetic polymer host material is a thermoplastic or a thermoset, and / or optionally, the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

10. The synthetic polymer composition according to claim 9 or 10, wherein The one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions, wherein the rare earth ions are selected from Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2 + , Gd 3+ , Tb 3+ and Dy 3+ or a combination thereof, and / or optionally, the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides and aluminates or a combination thereof.

11. A method for preparing a synthetic polymer composition comprising: A synthetic polymer host material is contacted with one or more inorganic phosphor dopants to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material are capable of absorbing UV light and then emitting the UV light as down-converted visible light.

12. The method of claim 12, wherein: The synthetic polymer host material is a thermoplastic or a thermoset, and / or optionally, the synthetic polymer host material is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy resin, phenolic resin, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyetherketoneketone, polycarbonate, polyphenylsulfone, polymethyl methacrylate, polyacrylate and benzoxazine.

13. The method according to claim 12 or 13, wherein: The one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions, wherein the rare earth ions are selected from Pr 3+ 、Ce 3+ 、Eu 3+ 、Eu 2+ , Gd 3+ , Tb 3+ and Dy 3+ or a combination thereof.

14. The method according to any one of claims 12 to 14, wherein: The synthetic polymer composition produced exhibits mechanical and flammability properties comparable to synthetic polymer compositions that do not contain the one or more inorganic phosphor dopants.

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