Halogen-free flame-retardant nylon as well as preparation method and application thereof
By using functionalized boron nanofibers and gradient hyperbranched polyols in halogen-free flame-retardant nylon, the flame-retardant and mechanical properties of flame-retardant nylon were improved, the problem of flame retardant decomposition and migration at high temperatures was solved, and higher heat resistance and better material stability were achieved.
Patent Information
- Application Number
- CN202511393619.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2025-12-23
AI Technical Summary
Existing halogen-free flame-retardant nylons have poor thermal stability at high temperatures, and the flame retardants are prone to decomposition or migration, resulting in reduced flame retardant efficiency. Furthermore, the bonding force between the nylon and the matrix is weak, which affects the mechanical properties and heat resistance.
Functionalized boron nanofibers and gradient hyperbranched polyols are used to form carbon through SiC vapor deposition and black phosphorus catalytic polymerization. The functional group gradient distribution of the phosphate core, epoxy middle layer and alkyl outer layer enhances the interfacial strength and flame retardant properties.
It improves the flame retardant properties, mechanical properties, and heat resistance limit of halogen-free flame retardant nylon, solves the problem of decomposition and migration of traditional halogen-free flame retardants at high temperatures, and achieves higher flame retardant efficiency and better material stability.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of flame-retardant nylon, in particular to a halogen-free flame-retardant nylon, a preparation method and application thereof. BACKGROUND
[0002] Nylon (polyamide) is a kind of high-performance engineering plastic, which is widely used in key components such as gears, bearings, connectors in the fields of automobiles, electronics and electrical appliances, rail transit, etc. due to its excellent mechanical strength, wear resistance, chemical corrosion resistance and processing performance.
[0003] However, the limiting oxygen index (LOI) of unmodified nylon is only about 20-22%, which belongs to flammable materials. When burning, it produces molten droplets and releases a large amount of toxic smoke, which seriously threatens life and property safety. With the increasingly stringent global environmental regulations (such as the EU RoHS directive and IEC 61249-2-21 halogen-free standard), traditional halogen-based flame-retardant nylon has been gradually eliminated from the market due to the release of carcinogens such as dioxins during combustion, and halogen-free flame-retardant technology has become the core direction of nylon functional modification.
[0004] The current mainstream halogen-free flame-retardant system mainly includes phosphorus-based, nitrogen-based, metal hydroxide and intumescent flame retardant. The processing temperature of nylon is usually higher than 220℃, while most organic phosphorus flame retardants (such as phosphate ester) have poor thermal stability (decomposition temperature <200℃), which will decompose or volatilize during melt extrusion, not only reducing the flame-retardant efficiency, but also corroding the equipment; in addition, nano flame-retardant fillers (such as layered silicate) are easy to agglomerate under high temperature shear, forming local stress concentration points and accelerating material fatigue fracture. Boron fibers have high modulus and low thermal expansion coefficient, but their surface inertness makes their interfacial bonding with the nylon matrix weak, and the exposed boron fibers are easy to oxidize to B2O3 in a high-temperature and humid environment, resulting in a sharp drop in mechanical properties.
[0005] In addition, there are currently hyperbranched polyols used in nylon, which have high loadings of phosphorus and nitrogen elements due to the bonding of 6-12 flame-retardant groups per molecule, and also have a toughening effect due to the spherical structure that blocks the crack propagation path. However, the decomposition temperature of hyperbranched polyols is usually lower than 200℃ (such as phosphate ester groups are prone to thermal decomposition), while the melt processing temperature of nylon is as high as 220-280℃, so it is only suitable for automotive interior parts, electrical appliance housings and other fields with a temperature requirement of <180℃. Secondly, the poor compatibility of the polar hydroxyl groups of hyperbranched polyols with the nylon matrix causes the flame retardant to migrate to the surface over time, and the phosphorus flame-retardant groups will concentrate in the core of the molecule, which cannot quickly migrate to the surface of the material during combustion, resulting in a decrease in flame-retardant efficiency.
[0006] In order to improve the flame-retardant performance of flame-retardant nylon while taking into account its mechanical properties and upper limit of heat resistance, the present application provides a solution. SUMMARY
[0007] The application provides a halogen-free flame-retardant nylon and a preparation method and application thereof, which can improve the flame-retardant performance, mechanical performance and upper limit of heat resistance of the halogen-free flame-retardant nylon.
[0008] In one aspect, the application provides a halogen-free flame-retardant nylon, wherein the raw materials of the halogen-free flame-retardant nylon include a base resin, a heat-resistant agent, a flame retardant and a functional additive; the heat-resistant agent is functionalized nanometer boron fiber, and the raw materials of the functionalized nanometer boron fiber include nanometer boron fiber, trichloromethylsilane and black phosphorus nanosheet; the flame retardant is gradient hyperbranched polyol, and the raw materials of the hyperbranched polyol include trimethylolpropane, diphenyl phosphate, epoxy chloropropane, glycidyl stearate and tetrabutylammonium bromide.
[0009] By adopting the above technical scheme, the heat-resistant agent in the application is functionalized nanometer boron fiber, and the raw materials thereof include nanometer boron fiber, trichloromethylsilane and black phosphorus nanosheet; when burning, SiC is oxidized into SiO2 glass body covering layer, and black phosphorus catalyzes polymer to form carbon and capture free radicals, thereby increasing the flame-retardant effect, and the interfacial strength of the nanometer boron fiber combined with the base resin is improved. In addition, the flame retardant in the application is hyperbranched polyol, which is gradientized, including phosphate ester core, epoxy middle layer and alkyl outer layer, to realize the spatial gradient distribution of functional groups. Specifically, the phosphate ester core can condense into carbon and capture free radicals, the epoxy middle layer can open ring chain extension with the amino group at the end of PA6, and in addition, the alkyl outer layer can reduce the melt viscosity and surface lubrication, thereby helping to improve the flame-retardant performance, mechanical performance and upper limit of heat resistance of the halogen-free flame-retardant nylon.
[0010] Preferably, the functional additive includes a carbonization catalyst, a synergistic carbonization agent, a toughening agent and an antioxidant; the carbonization catalyst includes one or more of zinc borate, zinc stannate and zinc molybdate; the synergistic carbonization agent includes one or more of pentaerythritol ester, lignin sulfonate and cage-type silsesquioxane; and the toughening agent includes one or more of POE-g-MAH, EPDM-g-MAH and SEBS-g-GMA.
[0011] In one aspect, the application provides a preparation method of a halogen-free flame-retardant nylon, which includes the following operation steps: preparation of functionalized nanometer boron fiber, preparation of gradient hyperbranched polyol, melt extrusion of the halogen-free flame-retardant nylon, and post-curing treatment of the halogen-free flame-retardant nylon.
[0012] Preferably, the preparation of the functionalized boron nanofibers includes the following steps: S1, boron fiber pretreatment: boron fibers are acid-washed at room temperature, then rinsed with deionized water until neutral, and dried to obtain pretreated boron fibers; S2, SiC vapor deposition: trichloromethylsilane is preheated and dehumidified, then deposition is started on the surface of the pretreated boron fibers, and the temperature is maintained at a constant temperature. Finally, the temperature is gradually reduced until the SiC layer covers the surface of the boron fibers to obtain SiC@boron fibers; S3, vacuum impregnation loading of boron fibers: black phosphorus nanosheets are mixed in ethanol and ultrasonically treated to obtain a black phosphorus dispersion; then the SiC@boron fibers are vacuum impregnated in the black phosphorus dispersion; finally, the fibers are heated in a tube furnace for curing to obtain functionalized boron nanofibers.
[0013] By adopting the above technical solutions, the purpose of the boron fiber pretreatment in this application is to remove surface oxides and enhance interfacial bonding. Furthermore, the SiC vapor deposition is used to composite the SiC layer with the boron fibers, thereby forming a strong interfacial strength. By vacuum-extracting air from the fibers, black phosphorus is loaded onto the boron fibers, increasing the loading rate of black phosphorus on the boron fibers and thus improving the flame-retardant efficiency of the flame-retardant nylon.
[0014] Preferably, the preparation of the gradient hyperbranched polyol includes the following steps: S1, adding trimethylolpropane to a reaction vessel and dissolving it in toluene, then adding diphenyl phosphate dropwise in proportion, and adding tetrabutylammonium bromide catalyst under controlled temperature to obtain a phosphate core, namely tri(diphenyl phosphate)trimethylolpropane; S2, dissolving the phosphate core in toluene, adding epichlorohydrin, and under controlled temperature, modifying the hyperbranched phosphate ester with epoxy groups to obtain an epoxy-modified hyperbranched phosphate ester; S3, mixing glycidyl stearate and sorbitan oleate, performing a pre-emulsification operation, and adding it to the epoxy-modified hyperbranched phosphate ester to obtain a gradient hyperbranched polyol.
[0015] By adopting the above technical solution, this application constructs a gradient structure of "phosphate core - epoxy middle layer - alkyl outer layer" through a three-step reaction. The phosphate core provides phosphorus through tris(diphenyl phosphate)trimethylolpropane, which helps to catalyze the dehydrogenation of nylon to form carbon. The epoxy transition layer is covalently bonded to the terminal amine group of nylon through an epichlorohydrin grafting reaction, thereby improving the stability of the structure. Finally, the alkyl outer layer is a hydrophobic shell, which is formed by using glycidyl stearate to form a gradient hyperbranched polyol outer layer, thereby reducing the migration of flame retardants and improving flame retardant performance.
[0016] Preferably, the melt extrusion of the halogen-free flame-retardant nylon includes the following steps: First, the matrix resin, gradient hyperbranched polyol, char-forming catalyst, and synergistic char-forming agent are initially mixed in a high-speed mixer, and then fed into the main feed port 1 zone of a twin-screw extruder, with the screw extruder temperature set in zones 1-3 respectively; second, functionalized nano-boron fibers are added to the side feed port 4 zone of the twin-screw extruder, and the screw extruder temperature is set in zone 4; then, a toughening agent is added to the side feed port 5 zone of the twin-screw extruder, and the screw extruder temperature is set in zones 5-7; finally, the screw extruder temperature is set in zone 8 to obtain unformed halogen-free flame-retardant nylon.
[0017] Preferably, in the melt extrusion step of the halogen-free flame-retardant nylon, the temperature settings and residence times of the twin-screw extruder are as follows: Zone 1 temperature is 200-210℃; Zone 2 temperature is 220-240℃; Zone 3 temperature is 230-250℃; Zone 4 temperature is 210-230℃; Zone 5 temperature is 230-240℃; Zone 6 temperature is 230-250℃; Zone 7 temperature is 220-240℃; and Zone 8 temperature is 200-210℃.
[0018] By adopting the above technical solution, zones 1-3 belong to the melt ring-opening reaction. Zone 1 is set at 200-210℃, at which time the nylon matrix resin melts. Zone 2 is set at 220-240℃, where the epoxy groups on the gradient hyperbranched polyol undergo ring-opening and chain extension. Zone 3 is set at 230-250℃, at which time the phosphate ester bonds with the nylon groups. Zone 4 is set at 210-230℃, so that the melt viscosity is reduced to 850 Pa·s within the temperature range, making it easier for the low-viscosity melt to coat the boron fibers and reducing the probability of boron fiber breakage. Zones 5 and 6 are set at 230-240℃, and Zone 7 is set at 220-240℃, respectively, to improve the toughening effect of the toughening agent and help to achieve dynamic cross-linking between nylon and toughening agent. Zone 8 is set at 200-210℃ to homogenize the nylon melt, prevent decomposition, and form at low temperature.
[0019] Preferably, the post-curing treatment of the halogen-free flame-retardant nylon includes the following steps: placing the halogen-free flame-retardant nylon in a hot air circulating oven under nitrogen protection for post-curing treatment to obtain halogen-free flame-retardant nylon.
[0020] On the other hand, this application provides an application of halogen-free flame-retardant and antistatic nylon. The halogen-free flame-retardant and antistatic nylon in this application is used to manufacture mechanical industrial parts, such as gear parts and transmission parts; specifically, the application scope includes automobiles, subways, ships and robots.
[0021] One or more technical solutions provided in this application have at least the following technical effects or advantages:
[0022] 1. The heat resistant agent in this invention is functionalized boron nanofiber, the raw materials of which include boron nanofiber, trichloromethylsilane and black phosphorus nanosheets; when burning, SiC is oxidized to a SiO2 glassy covering layer, while black phosphorus catalyzes the polymer to form carbon and captures free radicals, thereby increasing the flame retardant effect, and the interfacial strength between the boron nanofiber and the matrix resin is improved.
[0023] 2. The flame retardant in this invention is a hyperbranched polyol, which undergoes a gradient treatment, including a phosphate core, an epoxy middle layer, and an alkyl outer layer, achieving a spatial gradient distribution of functional groups. Specifically, the phosphate core can condense into carbon and capture free radicals, the epoxy middle layer can ring-open and extend the chain with the PA6-terminal amino group, and the alkyl outer layer can reduce melt viscosity and surface lubrication, thereby helping to improve the flame retardant properties, mechanical properties, and upper limit of heat resistance of halogen-free flame-retardant nylon.
[0024] 3. This invention makes specific adjustments to the melt extrusion of functionalized boron nanofibers and hyperbranched polyols in halogen-free flame-retardant nylon, including melt ring opening, fiber protection, dynamic cross-linking and low-temperature molding operations, to achieve chemical bonding and fixation of flame retardants, fundamentally solving the defects of physical mixing of flame retardants. Detailed Implementation
[0025] This application provides a halogen-free flame-retardant nylon, its preparation method, and its application, which can improve the flame-retardant properties, mechanical properties, and upper limit of heat resistance of halogen-free flame-retardant nylon.
[0026] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0027] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or modules not explicitly listed or inherent to such processes, methods, products, or devices.
[0028] Example
[0029] Example 1
[0030] The preparation of functionalized boron nanofibers in Example 1 of this application includes the following steps:
[0031] S1. Boron Fiber Pretreatment: Boron fibers are acid-washed at room temperature using a 10% HF + 5% HNO3 (volume ratio). The acid washing temperature is 25℃ for 15 minutes, followed by rinsing with deionized water until neutral. Finally, the fibers are dried in a vacuum oven at 80℃ for 2 hours to obtain pretreated boron fibers. The purpose of this step is to dissolve the surface B2O3 oxide layer and expose active boron atoms. The principle is as follows.
[0032] 2B + 6HF + 3HNO3 → 2BF3 + 3NO2 + 6H2O
[0033] S2, SiC vapor phase deposition: First, trichloromethylsilane is preheated and dehumidified at 300℃ for 30 min, and then purged with Ar to form a vapor phase. Deposition then begins on the pretreated boron fiber surface, with the temperature increased from 300℃ to 1100℃ in an Ar:hydrogen atmosphere of 95:5. This temperature is maintained at a constant deposition time of 40 min. Finally, a gradient cooling process is performed, reducing the temperature from 1100℃ to 600℃ over 60 min under Ar atmosphere protection, until a SiC layer covers the surface of the boron fiber, resulting in SiC@boron fiber. The deposition rate of the above reaction is 2 nm / min, and the coating thickness is 80±5 nm. The principle of vapor phase deposition is as follows.
[0034]
[0035] S3. Vacuum Impregnation Loading of Boron Fibers: Black phosphorus nanosheets were mixed in ethanol and ultrasonically treated at 800W / 30min and centrifuged at 8000rpm / 15min to obtain a black phosphorus dispersion. SiC@boron fibers were then vacuum impregnated in the black phosphorus dispersion at 60℃ for 2h. The air inside the fibers was removed by vacuum extraction, and the dispersion was injected into the micropores when the pressure returned to normal. Finally, the fibers were cured in a tube furnace by temperature gradient increase from 250℃ to 350℃ to obtain functionalized boron nanofibers.
[0036] Example 1 of this application also discloses a preparation method for a gradient hyperbranched polyol, which specifically includes the following steps:
[0037] S1. Trimethylolpropane was added to a reaction vessel and dissolved in toluene. Then, diphenyl phosphate was added dropwise at a rate of 5 g / min, with a total weight ratio of 1:3. A small amount of tetrabutylammonium bromide catalyst was added. The temperature in the reaction vessel was controlled at 120℃ for 3 hours, and the stirring speed was 500 rpm. The resulting phosphate core was tris(diphenyl phosphate)trimethylolpropane. The chemical formula of the reaction is as follows.
[0038]
[0039] S2. Dissolve the phosphate core in toluene and add epichlorohydrin dropwise at a rate of 0.1 mL / min·g of raw material. Control the temperature at 80℃ for 2 hours to obtain an epoxy-modified hyperbranched phosphate ester.
[0040] S3. Glycidyl stearate and sorbitan oleate were mixed in a weight ratio of 15:1 and pre-emulsified. The mixture was then added to epoxy-modified hyperbranched phosphate ester at 140°C for 2 hours to obtain a gradient hyperbranched polyol. The underlying reaction is shown below.
[0041]
[0042] This application discloses specific steps for melt extrusion of halogen-free flame-retardant nylon:
[0043] First, 50 parts of PA6 matrix resin (intrinsic viscosity 2.4 dL / g), 6 parts of gradient hyperbranched polyol, 8 parts of zinc borate, 0.3 parts of antioxidant 1098 / 168 (1:1 blend), and 3 parts of pentaerythritol ester were initially mixed in a high-speed mixer at 1200 rpm for 5 minutes at 60°C. The purpose was to allow the epoxy groups (-O-) of the hyperbranched polyol to initially contact the terminal amino groups (-NH2) of PA6 before melting, and to ensure a more uniform subsequent reaction. The mixture then entered the main feed port zone 1 of a twin-screw extruder, with the extruder temperatures set for zones 1-3.
[0044] Specifically, the temperature in zone 1 is 200-210℃; the temperature in zone 2 is 220-240℃; and the temperature in zone 3 is 230-250℃. The reactions occurring in zones 1-3 are melt ring-opening reactions. In zone 1, set at 200-210℃, the nylon matrix resin melts; in zone 2, set at 220-240℃, the epoxy groups on the gradient hyperbranched polyol undergo ring-opening and chain extension; and in zone 3, set at 230-250℃, the phosphate ester bonds with the nylon groups.
[0045] Secondly, functionalized nano-boron fibers are introduced into zone 4 of the side feed port of the twin-screw extruder, and the temperature of the screw extruder is set in zone 4. The temperature in zone 4 is set to 210-230℃, so that the melt viscosity is reduced to 850 Pa·s within the temperature range, making it easier for the low-viscosity melt to coat the boron fibers and reducing the probability of boron fiber breakage.
[0046] Then, the toughening agent POE-g-MAH is added to zone 5 of the side feed port of the twin-screw extruder, and the temperature of the screw extruder is set in zones 5-7; the temperature in zone 5 is 230-240℃, the temperature in zone 6 is 230-250℃, and the temperature in zone 7 is 220-240℃, which is to improve the toughening effect of the toughening agent and help to achieve dynamic cross-linking between nylon and toughening agent.
[0047] The temperature of the screw extruder is set in zone 8, at 200-210℃, to homogenize the nylon melt, prevent decomposition, and form it at a low temperature to obtain crude halogen-free flame-retardant nylon.
[0048] Finally, Embodiment 1 of this application discloses the following steps for the post-curing treatment of halogen-free flame-retardant nylon: the halogen-free flame-retardant nylon is placed in a hot air circulating oven under nitrogen protection at a temperature of 120°C for 2 hours, and then post-cured to obtain halogen-free flame-retardant nylon.
[0049] Example 2
[0050] The difference between Example 2 and Example 1 is that the char-forming catalyst is different. In Example 2, 8 parts of zinc stannate were used as the char-forming catalyst in the melt extrusion step of halogen-free flame-retardant nylon.
[0051] Example 3
[0052] The difference between Example 3 and Example 1 is that the char-forming catalyst is different. In Example 3, 8 parts of zinc molybdate are used as the char-forming catalyst in the melt extrusion step of halogen-free flame-retardant nylon.
[0053] Example 4
[0054] The difference between Example 4 and Example 1 is that the selection of the synergistic charring agent is different. In the melt extrusion step of halogen-free flame-retardant nylon, the charring catalyst used in Example 4 is 3 parts of lignin sulfonate.
[0055] Example 5
[0056] The difference between Example 5 and Example 1 is that the selection of the synergistic charring agent is different. In the melt extrusion step of halogen-free flame-retardant nylon, the charring catalyst used in Example 5 is 3 parts of cage-type silsesquioxane.
[0057] Example 6
[0058] The difference between Example 6 and Example 1 is that the choice of synergistic charring agent is different. In Example 6, the toughening agent added in the side feed port 5 zone of the twin-screw extruder in the melt extrusion step of halogen-free flame-retardant nylon is EPDM-g-MAH.
[0059] Example 7
[0060] The difference between this example and Example 1 is that the choice of synergistic charring agent is different. In Example 7, the toughening agent added in the side feed port 5 zone of the twin-screw extruder in the melt extrusion step of halogen-free flame-retardant nylon is SEBS-g-GMA.
[0061] Comparative Example
[0062] Comparative Example 1
[0063] The difference between Comparative Example 1 and Example 1 is that no functionalized boron nanofibers and gradient hyperbranched polyols were added in the melt extrusion step of halogen-free flame-retardant nylon.
[0064] Comparative Example 2
[0065] The difference between Comparative Example 2 and Example 1 is that untreated boron fibers and hyperbranched polyols were added in the melt extrusion step of halogen-free flame-retardant nylon.
[0066] Performance testing
[0067] The halogen-free flame-retardant nylons prepared in Examples 1-7 and Comparative Examples 1-2 were subjected to UL94 flame retardancy, tensile strength, and heat resistance tests. The specific test standards and schemes are as follows, and the relevant test data are compiled into Table 1 below.
[0068] 1. UL 94 Flame Retardant Test: The test standard is UL 94-2020, "Tests on the flammability of plastic materials for use in equipment and appliance parts". A sample of 125mm × 13mm × 0.8mm is selected and tested using a flame. The flame height is 20mm (methane flow rate 105mL / min). The first application lasts 10 seconds, and after extinguishing, a second application lasts 10 seconds. The judgment criteria are: single burning time ≤ 10s, total burning time ≤ 50s, no molten droplets igniting the absorbent cotton, and burn length ≤ 80mm. The classification is shown in the table below.
[0069] 2. Tensile strength test: The test standard adopted is ISO 527-2:2012 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics". The sample is placed in the fixture and fixed. The environment is set at 25°C and 50% humidity. The fixture spacing is 115mm. Tension is carried out at 50mm / min. The obtained data are compiled into the table below.
[0070] 3. Heat resistance test: The test standard adopts ISO 75-2:2013 "Plastics—Determination of deformation temperature under load—Part 2: Plastics and hard rubber". Select a sample of 80mm×10mm×4mm and measure the temperature of nylon material when it deforms by 0.34mm under a three-point bending load (i.e., heat distortion temperature).
[0071] Table 1, Performance Test Tables of Examples 1-7 and Comparative Examples 1-2
[0072] Flame retardant test Tensile strength / MPa Heat resistance test / °C Example 1 V-0 192 210 Example 2 V-0 190 205 Example 3 V-0 188 200 Example 4 V-0 191 205 Example 5 V-0 185 208 Example 6 V-0 183 203 Example 7 V-0 186 204 Comparative Example 1 V-2 158 115 Comparative Example 2 V-1 170 140
[0073] Analysis of Example 1 and Comparative Example 1 reveals that the difference between them lies in the absence of functionalized boron nanofibers and gradient hyperbranched polyols in the melt extrusion step of the halogen-free flame-retardant nylon. The lack of boron fibers and hyperbranched polyols results in a flame retardancy rating of only V-2, and the tensile strength and heat resistance are significantly inferior to those of Example 1.
[0074] Combined with the analysis of Comparative Example 2, which used untreated boron fibers and hyperbranched polyols, it was found that both ordinary boron fibers and hyperbranched polyols could improve flame retardancy, tensile strength, and heat resistance. This is because boron fibers, as rigid fillers, can disperse stress and, due to their high thermal conductivity, delay local temperature rise. Furthermore, each molecule of hyperbranched polyol can bond 6-12 flame-retardant groups, thus exhibiting a high phosphorus and nitrogen loading characteristic. Simultaneously, hyperbranched polyols have a toughening effect, with their spherical structure blocking crack propagation paths.
[0075] Analysis of Comparative Example 2 and Example 1 shows that this application modifies boron fibers, where SiC is oxidized to a SiO2 glassy capping layer during the combustion of flame-retardant nylon. Simultaneously, black phosphorus catalyzes polymer char formation and captures free radicals, thereby increasing the flame-retardant effect. Furthermore, the interfacial strength between the nano-boron fibers and the matrix resin is enhanced. Additionally, the hyperbranched polyol undergoes a gradient treatment, including a phosphate core, an epoxy middle layer, and an alkyl outer layer, achieving a spatial gradient distribution of functional groups. Consequently, Example 1, compared to Comparative Example 1, exhibits significantly improved flame-retardant properties, tensile strength, and heat resistance.
[0076] Furthermore, analysis of Examples 1-7 reveals that the charring catalyst, synergistic charring agent, and toughening agent are all crucial components in the synthesis of flame-retardant nylon. The charring catalyst is zinc borate, the synergistic charring agent is pentaerythritol ester, and the toughening agent is POE-g-MAH, all of which significantly improve the flame-retardant properties, tensile strength, and heat resistance of halogen-free flame-retardant nylon.
[0077] Finally, the halogen-free flame-retardant nylon described in this application, due to its excellent flame-retardant properties, tensile strength, and heat resistance, is highly suitable for manufacturing mechanical industrial parts, such as gear components and transmission components. Specifically, its applications include the automotive, subway, marine, and robotics industries.
[0078] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the described process does not necessarily require a specific or sequential order to achieve the desired result. In some implementations, multitasking and parallel processing are also possible or may be advantageous.
[0079] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
[0080] This specification is merely an illustrative description of this application and is intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Therefore, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.
Claims
1. A halogen-free flame-retardant nylon, characterized in that, The raw materials for the halogen-free flame-retardant nylon include a matrix resin, a heat resistant agent, a flame retardant, and functional additives. The heat-resistant agent is functionalized boron nanofiber, and the raw materials of the functionalized boron nanofiber include boron nanofiber, trichloromethylsilane and black phosphorus nanosheets. The flame retardant is a gradient hyperbranched polyol, and the raw materials of the hyperbranched polyol include trimethylolpropane, diphenyl phosphate, epichlorohydrin, glycidyl stearate, and tetrabutylammonium bromide.
2. The halogen-free flame-retardant nylon as described in claim 1, characterized in that, The functional additives include char-forming catalysts, synergistic char-forming agents, toughening agents, and antioxidants: The char-forming catalyst includes one or more of zinc borate, zinc stannate, and zinc molybdate. The synergistic char-forming agent includes one or more of pentaerythritol ester, lignin sulfonate, and cage-type silsesquioxane; The toughening agent includes one or more of POE-g-MAH, EPDM-g-MAH, and SEBS-g-GMA.
3. The method for preparing halogen-free flame-retardant nylon according to any one of claims 1-2, characterized in that, The process includes the following steps: preparation of functionalized boron nanofibers, preparation of gradient hyperbranched polyols, melt extrusion of halogen-free flame-retardant nylon, and post-curing treatment of halogen-free flame-retardant nylon.
4. The method for preparing halogen-free flame-retardant nylon as described in claim 6, characterized in that, The preparation of the functionalized boron nanofibers includes the following steps: S1. Boron fiber pretreatment: The boron fiber is acid-washed at room temperature, then rinsed with deionized water until neutral, and dried to obtain pretreated boron fiber; S2, SiC vapor deposition: Trichloromethylsilane is preheated and dehumidified, and then deposition begins on the surface of the pretreated boron fiber by heating and maintaining a constant temperature deposition. Finally, the temperature is gradually reduced until the SiC layer covers the surface of the boron fiber, thus obtaining SiC@boron fiber. S3. Vacuum impregnation loading of boron fibers: Black phosphorus nanosheets are mixed in ethanol and ultrasonically treated to obtain a black phosphorus dispersion; then the SiC@boron fibers are vacuum impregnated in the black phosphorus dispersion; finally, they are cured by heating in a tube furnace to obtain functionalized boron nanofibers.
5. The method for preparing halogen-free flame-retardant nylon as described in claim 4, characterized in that, The preparation of the gradient hyperbranched polyol includes the following steps: S1. Trimethylolpropane is added to the reaction vessel and dissolved in toluene. Then, diphenyl phosphate is added dropwise in proportion. Under the control of a certain temperature, tetrabutylammonium bromide catalyst is added to obtain the phosphate core, which is tri(diphenyl phosphate)trimethylolpropane. S2. Dissolve the phosphate core in toluene and add epichlorohydrin. Under controlled temperature, modify the hyperbranched phosphate ester with epoxy groups to obtain an epoxy-modified hyperbranched phosphate ester. S3. Glycidyl stearate and sorbitan oleate are mixed and pre-emulsified, and then added to the epoxy-modified hyperbranched phosphate ester to obtain a gradient hyperbranched polyol.
6. The method for preparing halogen-free flame-retardant nylon as described in claim 5, characterized in that, The melt extrusion of the halogen-free flame-retardant nylon includes the following steps: First, the matrix resin, gradient hyperbranched polyol, char catalyst, and synergistic char agent are initially mixed in a high-speed mixer, and then fed into the main feed port 1 zone of the twin-screw extruder. The temperatures of the screw extruder are set in zones 1-3 respectively. Secondly, functionalized nano-boron fibers are introduced into zone 4 of the side feed port of the twin-screw extruder, and the temperature of the screw extruder is set in zone 4. Then, toughening agent is added to zone 5 of the side feed port of the twin-screw extruder, and the temperature of the screw extruder is set in zones 5-7; Finally, the temperature of the screw extruder was set in zone 8 to obtain unformed halogen-free flame-retardant nylon.
7. The method for preparing halogen-free flame-retardant nylon as described in claim 6, characterized in that, In the melt extrusion step of the halogen-free flame-retardant nylon, the temperature settings and residence times of the twin-screw extruder are as follows: Zone 1 temperature is 200-210℃; Zone 2 temperature is 220-240℃; Zone 3 temperature is 230-250℃; Zone 4 temperature is 210-230℃; Zone 5 temperature is 230-240℃; Zone 6 temperature is 230-250℃; Zone 7 temperature is 220-240℃; Zone 8 temperature is 200-210℃.
8. The method for preparing halogen-free flame-retardant nylon as described in claim 6, characterized in that, The post-curing treatment of the halogen-free flame-retardant nylon includes the following steps: The halogen-free flame-retardant nylon was placed in a hot air circulating oven under nitrogen protection for post-curing treatment to obtain halogen-free flame-retardant nylon.
9. The halogen-free flame-retardant nylon as described in any one of claims 1-2, or the halogen-free flame-retardant and antistatic nylon prepared by the method of preparing the halogen-free flame-retardant and antistatic nylon as described in any one of claims 3-8, characterized in that, The halogen-free flame-retardant nylon is used in the manufacture of mechanical industrial parts, such as gear components and transmission components; Specifically, its applications include automobiles, subways, ships, and robots.