Bio-based PTT composite fiber and preparation method thereof

Abstract

The invention relates to the technical field of polyester fibers, in particular to a bio-based PTT composite fiber and a preparation method thereof. The problem that traditional polyester fibers are poor in mechanical property and antibacterial property is solved. According to the invention, a ternary blending system of bio-based PTT, polylactic acid-glycolic acid and nanocellulose is adopted, and a citric acid loaded metal organic framework is introduced as a dynamic cross-linking agent, so that the mechanical properties of the composite fiber are improved; a sheath layer is obtained by adopting a composite system of polycaprolactone and chitosan-silver nanoparticles and combining an electrostatic spinning process, so that the antibacterial property of the composite fiber is improved; the preparation method comprises the following steps: preparing a tannic acid modified silicon dioxide filling interface, and combining a plasma treatment technology and an annealing process to realize chemical-physical synergistic reinforcement of a core-sheath interface; the steeping liquor is prepared from the tea polyphenol-cyclodextrin inclusion compound, controlled release of tea polyphenol is achieved through a hydrophobic cavity of cyclodextrin, and therefore broad-spectrum bacteriostasis is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester fibers, and specifically to a bio-based PTT composite fiber and a preparation method thereof. Background Art

[0002] With the rapid development of material science and the textile industry, conjugated multi-component artificial filaments are increasingly widely used in the fields of textile and clothing, medical and health, industrial manufacturing, etc. due to their unique composite structure and excellent properties. As a typical conjugated fiber, poly(trimethylene terephthalate) (PTT) fiber combines the high performance of PET and the easy processability of PBT, has excellent elastic recovery rate, soft hand feeling and dyeing performance, and can be used to prepare continuous and discontinuous fiber-reinforced composites, which has great application value in the textile field.

[0003] However, in practical applications, traditional PTT fibers expose many performance shortcomings. In terms of mechanical properties, its tensile strength and wear resistance are poor. When subjected to large external forces or long-term friction, the fibers are prone to breakage, pilling, etc., greatly shortening the service life of the products and restricting their application in the fields of industrial fabrics, high-performance sports equipment, etc.; in terms of antibacterial properties, PTT fibers themselves do not have antibacterial functions, which is likely to breed bacteria in scenarios with high hygiene requirements such as medical and health, home textiles, etc., causing health problems such as peculiar smell and allergies, threatening the health of users.

[0004] Therefore, it is urgent to develop a bio-based PTT composite fiber and a preparation method thereof, which can significantly improve the mechanical properties and antibacterial properties of the fiber while ensuring product quality and functionality. Summary of the Invention

[0005] The purpose of the present invention is to provide a bio-based PTT composite fiber and a preparation method thereof. By using a ternary blend system of bio-based PTT, poly(lactic-co-glycolic acid) and nanocellulose, and introducing citric acid-loaded metal-organic framework as a dynamic crosslinking agent, the mechanical properties of the composite fiber are improved; by adopting a composite system of polycaprolactone and chitosan-silver nanoparticles and combining with an electrospinning process to obtain a sheath layer, the antibacterial properties of the composite fiber are enhanced; by preparing a tannic acid-modified silica-filled interface and combining with plasma treatment technology and annealing process, the chemical-physical synergistic strengthening of the core-sheath interface is achieved; by using a tea polyphenol-cyclodextrin inclusion complex to prepare an impregnating solution, the controlled release of tea polyphenols is realized through the hydrophobic cavity of cyclodextrin, thereby achieving broad-spectrum antibacterial.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a method for preparing a bio-based PTT composite fiber, and the preparation method is as follows: melt-blend bio-based PTT, poly(lactic-co-glycolic acid), and nanocellulose, and add CA@MOF for in-situ crosslinking to obtain a core layer; compound polycaprolactone and chitosan-silver nanoparticles and then coat the core layer by electrospinning to obtain a sheath layer; adsorb tannic acid-modified silica at the core-sheath interface, and perform plasma treatment on the core-sheath interface, and then anneal at 50°C for 10 min to obtain enhanced fibers; immerse the enhanced fibers in a tea polyphenol-cyclodextrin inclusion complex solution, the fibers pass through the impregnation tank at a speed of 5 m / min, blow off the excess liquid by an air knife, and then perform ultraviolet curing to obtain composite fibers.

[0008] Preferably, the preparation method of the core layer is as follows: activate 5 parts of CA@MOF at 120°C for 4 h to remove pore moisture to obtain dry CA@MOF; add bio-based PTT, poly(lactic-co-glycolic acid), and nanocellulose to a twin-screw extruder according to a mass ratio of 9-12:4-7:3, set the feeding section temperature to 180-195°C, the melting section temperature to 195-210°C, and the discharging section temperature to 190°C, add dry CA@MOF through a side feeding port at the end of the melting section, and extrude to obtain the core layer.

[0009] Preferably, the preparation method of CA@MOF is as follows: dissolve 5 parts of citric acid in a mixed solution of 50 parts of ethanol and deionized water, ultrasonically disperse, adjust the pH to 3.5 with 0.1 M hydrochloric acid, add 6.5 parts of ZIF-8, stir and impregnate at 60°C for 35-45 h, then centrifuge and vacuum dry the obtained solid at 60°C for 24 h to obtain CA@MOF.

[0010] Preferably, the preparation method of the sheath layer is as follows: dissolve 10 parts of polycaprolactone with a molecular weight of 80-120 kDa in 30 parts of acetic acid solution, stir at 60°C for 12 h, add 2 parts of chitosan-silver nanoparticles, and ultrasonically disperse at a power of 300 W for 30 min to obtain a spinning solution; stretch the core layer into a monofilament with a diameter of 50-80 μm by a melt spinning machine, and the winding speed is 500 m / min; then perform electrospinning using a coaxial spinning needle, the voltage is 40-60 kV, the injection pump flow rate is 0.4 mL / h, and the receiving distance is 12-15 cm to obtain the sheath layer.

[0011] Preferably, the working gas for plasma treatment is composed of 90% argon and 10% oxygen, the flow rate is 20 sccm, the power is 100-125 W, and the treatment time is 30-60 s.

[0012] Preferably, the preparation method of tannic acid-modified silica is as follows: Disperse 5 parts of silica nanoparticles in 78 parts of ethanol, ultrasonically treat for 30 min, and vacuum-dry the solid particles obtained after centrifugal separation at 60 °C for 12 h to obtain pretreated silica; dissolve 3.75 parts of tannic acid in 100 parts of Tris-HCl buffer solution, stir until completely dissolved, add the pretreated silica, introduce nitrogen, and stir at 50-70 °C for 24 h, then perform centrifugal separation.

[0013] Wash with deionized water until the supernatant is colorless, and vacuum-dry the obtained filter cake at 60 °C for 24 h to obtain tannic acid-modified silica.

[0014] Preferably, the preparation method of the tea polyphenol-cyclodextrin inclusion complex solution is as follows: Dissolve 8-15 parts of the tea polyphenol-cyclodextrin inclusion complex in 30 parts of a 5 wt% aqueous ethanol solution, add 0.5 part of photoinitiator 2959, and stir at a rotation speed of 600 rpm for 4 h to obtain the tea polyphenol-cyclodextrin inclusion complex solution.

[0015] Preferably, the irradiation time for ultraviolet curing is 3-8 min, and the light intensity is 70-85 mW / cm 2 .

[0016] On the other hand, the present invention provides a bio-based PTT composite fiber. The raw materials for producing the composite fiber include bio-based PTT, poly(lactic-co-glycolic acid), nanocellulose, CA@MOF, polycaprolactone, chitosan-silver nanoparticles, tannic acid-modified silica, and tea polyphenol-cyclodextrin inclusion complex; the composite fiber is prepared by any one of the above preparation methods.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. Through the ternary blending system of bio-based PTT, poly(lactic-co-glycolic acid) (PLGA), and nanocellulose, the mechanical properties and degradability of bio-based materials are fully exerted; citric acid-loaded metal-organic framework (CA@MOF) is introduced as a dynamic crosslinking agent to trigger in-situ transesterification reactions during melt blending to form a controllable three-dimensional crosslinked network. The hydrogen bond interaction between the polar segments of PLGA and nanocellulose enhances the matrix compatibility within the core layer, and the confined acid release characteristics of CA@MOF avoid the chain segment degradation of polymers by traditional acidic crosslinking agents; the segmented temperature control of the twin-screw extruder precisely matches the acid release temperature window of CA@MOF, improving the mechanical properties of the composite fiber.

[0019] 2. The sheath layer of the present invention adopts a composite system of polycaprolactone (PCL) and chitosan-silver nanoparticles (Ag NPs). Through the electrospinning process driven by double-solvent evaporation, the antibacterial performance of the composite fibers is improved. Chitosan not only serves as a stable carrier for Ag NPs but also endows the fiber surface with antibacterial activity through cationic amino groups; the hydrophobicity of PCL forms an interfacial interlock with the polar core layer of PLGA; in addition, the combination of the coaxial spinning needle design and the control of acetic acid evaporation kinetics promotes the directional migration of Ag NPs to the outer surface of the sheath layer due to the surface tension gradient, and the antibacterial performance of the prepared composite fibers increases gradually from the inside to the outside.

[0020] 3. The present invention realizes the chemical-physical synergistic strengthening of the core-sheath interface through the interfacial molecular bridging strategy of tannic acid-modified silica (SiO2@TA) combined with plasma treatment technology. The phenolic hydroxyl groups of tannic acid in SiO2@TA are transformed into quinone structures under the induction of oxygen free radicals activated by plasma, reacting with the carboxyl groups of the core-layer polyester chain and the ester groups of the sheath-layer PCL to form a covalent bond network; the high-energy etching of the interface micro-region by plasma exposes more active sites, while the annealing treatment relieves the internal stress of the fiber and promotes the rearrangement and stabilization of the bonding sites.

[0021] 4. In the present invention, tea polyphenols (TP) are immobilized on the fiber surface by cyclodextrin (CD) through inclusion. The active hydroxyl groups in its polyphenol structure form hydrogen bonds and van der Waals forces complexes with the hydrophobic groups in the CD cavity, effectively inhibiting the oxidative inactivation of tea polyphenols and regulating their release kinetics; during the ultraviolet curing process, the photoinitiator triggers the crosslinking reaction of the coating to form a three-dimensional network on the fiber surface. On the one hand, the inclusion complex is fixed by covalent bonds to prevent the TP / CD coating from falling off due to friction or washing. On the other hand, the release rate of TP is controlled by the crosslinking density, enabling TP to migrate to the fiber surface in a long-term and directional manner to contact bacteria. Its catechol groups achieve broad-spectrum antibacterial by destroying the integrity of the bacterial cell membrane (lipid peroxidation) and inhibiting enzyme activity, while avoiding the sudden decrease in antibacterial efficiency caused by the short-term burst release of traditional coatings. Brief Description of the Drawings

[0022] Figure 1 It is a graph showing the test results of the mechanical properties of Examples 1-4 and Comparative Examples 1-3 of the present invention. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Please refer to Figure 1, the present invention provides a bio-based PTT composite fiber and its preparation method, and the technical solution is as follows:

[0025] The substance information involved in the present invention is as follows:

[0026] Poly(lactic-co-glycolic acid) CAS: 34346-01-5; citric acid CAS: 77-92-9; ethanol CAS: 64-17-5; ZIF-8 CAS: 59061-53-9; polycaprolactone CAS: 24980-41-4; acetic acid CAS: 64-19-7; silica nanoparticles CAS: 60676-86-0; tannic acid CAS: 1401-55-4; photoinitiator 2959 CAS: 106797-53-9; nanocellulose was purchased from Kaiyi New Materials Technology (Shanghai) Co., Ltd.; Tris-HCl buffer was purchased from Shanghai Merck Biochemical Technology Co., Ltd.; bio-based PTT was purchased from Jiangsu Orient Shenghong Co., Ltd.; chitosan-silver nanoparticles were prepared according to the method in "Preparation and Properties of Silver Nanoparticles / Chitosan"; tea polyphenol-β-cyclodextrin inclusion complex was prepared according to the method in "Preparation and Characterization of Oxygen Absorbent of Tea Polyphenol-β-Cyclodextrin Inclusion Complex".

[0027] Example 1

[0028] Activate 5 parts of CA@MOF at 120 °C for 4 h to remove pore moisture and obtain dry CA@MOF; add biobased PTT (moisture content ≤ 0.1%), poly(lactic-co-glycolic acid) (Mw = 80 kDa), and nanocellulose (diameter ≤ 50 nm, length 1 - 2 μm) into a twin-screw extruder in a mass ratio of 9:4:3. Set the temperature of the feeding section to 180 °C, the melting section to 195 °C, and the discharging section to 190 °C. Add the dry CA@MOF through the side feeding port at the end of the melting section and extrude to obtain the core layer; dissolve 10 parts of polycaprolactone with a molecular weight of 80 kDa in 30 parts of acetic acid solution, stir at 60 °C for 12 h, add 2 parts of chitosan-silver nanoparticles, and ultrasonically disperse for 30 min at a power of 300 W to obtain a spinning solution; stretch the core layer into monofilaments with a diameter of 50 μm by a melt spinning machine (spinning temperature 200 °C) at a winding speed of 500 m / min; then use a coaxial spinning needle (inner diameter of the core layer 1.2 mm, outer diameter of the sheath layer 1.5 mm) for electrospinning, with a voltage of 40 kV, an injection pump flow rate of 0.4 mL / h, and a receiving distance of 12 cm to obtain the sheath layer; adsorb tannic acid-modified silica at the core-sheath junction (disperse tannic acid-modified silica in a mixed solution of 20 parts of deionized water and ethanol, and then spray it onto the core-sheath interface through an electrostatic spraying device, with a voltage of 8 kV, a nozzle distance of 10 cm, and a flow rate of 0.2 mL / min, and then dry at 50 °C), and perform plasma treatment on the core-sheath interface. The working gas for plasma treatment consists of 90% argon and 10% oxygen, with a flow rate of 20 sccm, a power of 100 W, and a treatment time of 30 s. Then anneal at 50 °C for 10 min to eliminate residual stress and enhance the interfacial bonding strength to obtain the reinforced fiber; immerse the reinforced fiber in a tea polyphenol-cyclodextrin inclusion complex solution. The fiber passes through the impregnation tank (liquid temperature 30 °C) at a speed of 5 m / min, and then blows off the excess liquid through an air knife (wind speed 3 m / s), and then perform UV curing to obtain the composite fiber. The irradiation time for UV curing is 3 min, and the light intensity is 70 mW / cm 2 。

[0029] The preparation method of CA@MOF is as follows: dissolve 5 parts of citric acid in a mixed solution of 50 parts of ethanol and deionized water (volume ratio of the two 4:1), ultrasonically disperse, adjust the pH to 3.5 with 0.1 M hydrochloric acid to inhibit the ionization of citric acid and promote its entry into the pores in molecular form, enhance the hydrogen bond interaction between citric acid and the MOF pores, add 6.5 parts of ZIF-8, stir and impregnate at 60 °C for 35 h to ensure that citric acid molecules enter the MOF pores, then centrifuge (8000 rpm, 10 min) to remove the unadsorbed free citric acid and vacuum dry the obtained solid at 60 °C for 24 h to obtain CA@MOF.

[0030] The preparation method of tannic acid-modified silica is as follows: Disperse 5 parts of silica nanoparticles in 78 parts of ethanol, ultrasonically treat for 30 min (300 W), and the solid particles obtained after centrifugal separation (8000 rpm, 10 min) are vacuum-dried at 60 °C for 12 h to obtain pretreated silica; Dissolve 3.75 parts of tannic acid in 100 parts of Tris-HCl buffer solution (pH = 8.5), stir until completely dissolved, add the pretreated silica, pass in nitrogen and stir at 50 °C for 24 h, then perform centrifugal separation (10000 rpm, 15 min) and wash with deionized water until the supernatant is colorless. The obtained filter cake is vacuum-dried at 60 °C for 24 h to obtain tannic acid-modified silica.

[0031] The preparation method of the tea polyphenol-cyclodextrin inclusion complex solution is as follows: Dissolve 8 parts of the tea polyphenol-cyclodextrin inclusion complex in 30 parts of a 5 wt% ethanol aqueous solution, add 0.5 part of photoinitiator 2959, and stir at a rotation speed of 600 rpm for 4 h to obtain the tea polyphenol-cyclodextrin inclusion complex solution.

[0032] Examples 2 - 4

[0033] Refer to the preparation method and parameter conditions of Example 1. The specific differences are shown in Table 1; The mass ratio of the three in Table 1 is the mass ratio of bio-based PTT, polylactic acid-glycolic acid, and nanocellulose; The impregnation time is the impregnation time when preparing CA@MOF.

[0034] Comparative Example 1

[0035] Refer to the preparation method and parameter conditions of Example 1. The difference is that polylactic acid-glycolic acid was not added when preparing the core layer.

[0036] Comparative Example 2

[0037] Refer to the preparation method and parameter conditions of Example 1. The difference is that nanocellulose was not added when preparing the core layer.

[0038] Comparative Example 3

[0039] Refer to the preparation method and parameter conditions of Example 1. The difference is that CA@MOF was not added when preparing the core layer.

[0040] Experimental Example 1 Mechanical Property Test

[0041] Refer to the standard of GB / T 14337 - 2008 to test the mechanical properties; The obtained results are shown in Table 1 and Figure 1 as follows.

[0042] Table 1 Mechanical Property Tests of Examples 1 - 4 and Comparative Examples 1 - 3

[0043]

[0044] As can be seen from Table 1 and Figure 1 it can be seen that in Examples 1-4, through the ternary blend system of bio-based PTT, poly(lactic-co-glycolic acid) (PLGA), and nanocellulose, the mechanical properties and degradability of bio-based materials are fully utilized; CA@MOF is introduced as a dynamic crosslinking agent to trigger in-situ transesterification reactions during the melt blending process, forming a controllable three-dimensional crosslinked network. The hydrogen bonding between the polar segments of PLGA and nanocellulose enhances the matrix compatibility within the core layer, and the confined acid release characteristics of CA@MOF avoid the degradation of polymer segments by traditional acidic crosslinking agents; the segmented temperature control of the twin-screw extruder precisely matches the acid release temperature window of CA@MOF, improving the mechanical properties of the composite fibers. In Example 4, when the mass ratio of the three components is 9:7:3, the feeding section temperature is 190 °C, the melting section temperature is 200 °C, and the impregnation time is 40 h, the composite fibers prepared have the best mechanical properties, with a breaking strength of 3.87 cN / dtex. In Comparative Example 1, poly(lactic-co-glycolic acid) (PLGA) was not added during the preparation of the core layer, resulting in an imbalance in the polarity regulation of the core layer blend system, weakening the interfacial compatibility between bio-based PTT and nanocellulose, disrupting the ester group interaction between PTT and PLGA, reducing the dispersibility of nanocellulose in the PTT matrix, and prone to agglomeration to form stress concentration points; in addition, PLGA as a blend phase can improve the melt flow stability, and when PLGA is not added, the melt viscosity will be too high or thermal degradation will occur during the twin-screw extrusion process, further deteriorating the overall mechanical properties of the fibers. In Comparative Example 2, nanocellulose was not added during the preparation of the core layer, destroying the "soft-hard synergy" structure in the core layer; the PTT and PLGA blend matrix lacks the rigid support of nanocellulose, resulting in a decrease in the modulus and creep resistance of the fibers; the role of nanocellulose in anchoring polymer chains through hydrogen bonds disappears, and the chain segment slippage of the material during stress increases. In Comparative Example 3, CA@MOF was not added during the preparation of the core layer, and a three-dimensional dynamic crosslinked network could not be formed. The lack of chemical bond connection between polymer chains leads to the dominant deformation process of molecular chain slippage, and the mechanical properties are significantly deteriorated.

[0045] Examples 5-7

[0046] Referring to the preparation method and parameter conditions of Example 4, the specific differences are shown in Table 2.

[0047] Comparative Example 4

[0048] Referring to the preparation method and parameter conditions of Example 4, the difference is that the spinning solution does not contain chitosan-silver nanoparticles.

[0049] Comparative Example 5

[0050] Referring to the preparation method and parameter conditions of Example 4, the difference is that the monofilament diameter is 120 μm.

[0051] Comparative Example 6

[0052] Referring to the preparation method and parameter conditions of Example 4, except that the monofilament diameter is 20 μm.

[0053] Comparative Example 7

[0054] Referring to the preparation method and parameter conditions of Example 4, except that the molecular weight of polycaprolactone is 200 kDa.

[0055] Comparative Example 8

[0056] Referring to the preparation method and parameter conditions of Example 4, except that the molecular weight of polycaprolactone is 30 kDa.

[0057] Experimental Example 2 Antibacterial Performance Test

[0058] The antibacterial performance was tested according to the standard of ISO 20743-2013; the obtained results are shown in Table 2.

[0059] Table 2 Antibacterial Performance Test of Examples 4-7 and Comparative Examples 4-8

[0060]

[0061]

[0062] As can be seen from Table 2, in Examples 4-7, the sheath layer adopts a composite system of polycaprolactone (PCL) and chitosan-silver nanoparticles (Ag NPs). Through the electrospinning process driven by double-solvent evaporation, the antibacterial performance of the composite fibers is improved. Chitosan not only serves as a stable carrier for Ag NPs but also endows the fiber surface with antibacterial activity through cationic amino groups; the hydrophobicity of PCL forms an interfacial interlock with the polar core layer of PLGA; in addition, the combination of the coaxial spinning needle design and the control of acetic acid evaporation kinetics promotes the directional migration of Ag NPs to the outer surface of the sheath layer due to the surface tension gradient, forming a gradient distribution with gradually increasing antibacterial performance from the inside to the outside. In Example 6, when the molecular weight of polycaprolactone is 100 kDa, the single-filament diameter is 70 μm, the electrospinning voltage is 50 kV, and the receiving distance is 14 cm, the prepared composite fibers have the best antibacterial performance, with a Staphylococcus aureus inhibition rate of 99.2% and an Escherichia coli inhibition rate of 99.0%. Chitosan-silver nanoparticles are the main antibacterial components of the sheath layer. In Comparative Example 4, the spinning solution does not contain chitosan-silver nanoparticles, resulting in a simplified antibacterial mechanism of the fiber, relying only on the slow-release coating of tea polyphenol-cyclodextrin (TP / CD) to play an antibacterial role, with a decrease in antibacterial performance. Moreover, when relying only on TP / CD, the antibacterial activity of the fiber decays faster in a humid and hot environment. In Comparative Example 5, the single-filament diameter is 120 μm, and the decrease in specific surface area leads to a reduction in the loading of TP / CD per unit area coated by the sheath layer, resulting in insufficient exposure of antibacterial active substances. In Comparative Example 6, the single-filament diameter is 20 μm, and the amount of TP / CD loaded per unit volume of the fiber increases sharply, resulting in uneven coating thickness, an increase in internal stress during ultraviolet curing, and the appearance of microcracks, making the antibacterial substances escape in advance; moreover, the too-thin single filament will cause the sheath layer to break during the electrospinning process, and the binding force between TP / CD and the core layer decreases. In Comparative Example 7, the molecular weight of polycaprolactone is 200 kDa, and the higher crystallinity of high-molecular-weight PCL makes the encapsulated Ag NPs unable to be effectively released, and the Ag + concentration is lower than the minimum inhibitory concentration, resulting in a decrease in the antibacterial performance of the fiber. In Comparative Example 8, the molecular weight of polycaprolactone is 30 kDa, and the degradation period of low-molecular-weight PCL is shortened, and Ag NPs are rapidly released and oxidized and agglomerated, resulting in a sudden drop in antibacterial performance in the later stage.

[0063] Examples 8-10

[0064] Referring to the preparation method and parameter conditions of Example 6, the specific differences are shown in Table 3; the temperature in Table 3 is the temperature after introducing nitrogen when preparing tannic acid-modified silica.

[0065] Comparative Example 9

[0066] Referring to the preparation method and parameter conditions of Example 6, the difference is that the silica is not modified.

[0067] Comparative Example 10

[0068] Referring to the preparation method and parameter conditions of Example 6, except that the plasma treatment was not performed on the core-sheath interface.

[0069] Comparative Example 11

[0070] Referring to the preparation method and parameter conditions of Example 6, except that annealing was not performed after the plasma treatment.

[0071] Comparative Example 12

[0072] Referring to the preparation method and parameter conditions of Example 6, except that the working gas for the plasma treatment was only argon.

[0073] Comparative Example 13

[0074] Referring to the preparation method and parameter conditions of Example 6, except that the working gas for the plasma treatment was only oxygen.

[0075] Comparative Example 14

[0076] Referring to the preparation method and parameter conditions of Example 6, except that the silica was not pretreated when preparing tannic acid-modified silica.

[0077] Experimental Example 3 Mechanical Property Test

[0078] The mechanical properties were tested according to the standard of GB / T 14337-2008; the obtained results are shown in Table 3.

[0079] Table 3 Mechanical Property Tests of Example 6, Examples 8-10 and Comparative Examples 9-14

[0080]

[0081] As can be seen from Table 3, in Examples 6 and 8-10, the chemical-physical synergistic strengthening of the core-sheath interface is achieved through the interfacial molecular bridging strategy of tannic acid-modified silica (SiO2@TA) combined with plasma treatment technology. The phenolic hydroxyl groups of tannic acid in SiO2@TA are converted into quinone structures under the induction of plasma-activated oxygen free radicals, and react with the carboxyl groups of the core polyester chains and the ester groups of the sheath PCL to form a covalent bond network; the high-energy etching of the interface micro-region by plasma exposes more active sites, while the annealing treatment relieves the stress in the fiber and promotes the rearrangement and stabilization of the bonding sites. In Example 9, when the plasma treatment power is 120W, the plasma treatment time is 50s, and the temperature is 60°C, the mechanical properties of the composite fiber obtained are optimal, and the breaking strength is 4.02cN / dtex. In Comparative Example 9, the silica was not modified, and a large number of hydroxyl groups remained on the surface of the unmodified silica nanoparticles, which had a low polarity match with the core-sheath polymer matrix, resulting in weak interface bonding. When subjected to force, interface debonding easily occurred between the silica and the matrix material, resulting in stress concentration, and the stress could not be effectively dispersed and transmitted, thereby reducing the tensile mechanical properties of the composite fiber. In Comparative Example 10, the core-sheath interface was not plasma treated. During the stress process, the core layer and the sheath layer were prone to relative sliding and separation, and could not cooperate to resist external forces, resulting in a decrease in the overall mechanical properties of the composite fiber, especially when subjected to large external forces, the fiber was more likely to break. In Comparative Example 11, no annealing was performed after the plasma treatment, and the surface free radicals introduced by the plasma bombardment were not reorganized by annealing. The residual stress inside the fiber would be superimposed on the external stress, accelerating crack propagation. In Comparative Example 12, the working gas for plasma treatment is only argon. Although it can improve the surface roughness and increase the physical bonding force, it has limited effect on enhancing chemical bonding. The degree of chemical bonding at the core-sheath interface is low. When subjected to force, the bonding strength of the interface is insufficient, which affects the mechanical properties of the composite fiber. In Comparative Example 13, the working gas for plasma treatment is only oxygen. Excessive oxidation can cause damage and degradation of the material surface, destroying the structure and performance of the material. In Comparative Example 14, the silica was not pretreated when preparing tannic acid-modified silica. Impurities hindered the reaction of tannic acid with the hydroxyl groups on the surface of silica, reduced the grafting density, and poor compatibility between the modified particles and the matrix. When subjected to force, stress could not be effectively transferred, resulting in decreased mechanical properties of the composite fiber.

[0082] Examples 11-13

[0083] Referring to the preparation method and parameter conditions of Example 9, the specific differences are shown in Table 4.

[0084] Comparative Example 15

[0085] Referring to the preparation method and parameter conditions of Example 9, the difference is that the reinforcing fiber was not immersed in the tea polyphenol-cyclodextrin inclusion complex solution for impregnation.

[0086] Comparative Example 16

[0087] Referring to the preparation method and parameter conditions of Example 9, the difference is that the UV curing time was 20 min.

[0088] Experimental Example 4 Antibacterial Performance Test

[0089] The antibacterial performance was tested according to the standard of ISO 20743-2013; the obtained results are shown in Table 4.

[0090] Table 4 Antibacterial Performance Test of Example 9, Examples 11-13 and Comparative Examples 15-16

[0091]

[0092] As can be seen from Table 4, in Example 9 and Examples 11-13, tea polyphenol (TP) was fixed on the fiber surface by cyclodextrin (CD) through inclusion. The active hydroxyl groups in its polyphenol structure formed hydrogen bonds and van der Waals forces with the hydrophobic groups in the CD cavity, effectively inhibiting the oxidative inactivation of tea polyphenols and regulating their release kinetics; during the UV curing process, the photoinitiator triggered the cross-linking reaction of the coating to form a three-dimensional network on the fiber surface. On the one hand, the inclusion complex was fixed by covalent bonds to prevent the TP / CD coating from falling off due to friction or washing. On the other hand, the release rate of TP was controlled by the cross-linking density, enabling TP to migrate to the fiber surface in a long-term and directional manner and contact bacteria. Its catechol group achieved broad-spectrum antibacterial by destroying the integrity of the bacterial cell membrane (lipid peroxidation) and inhibiting enzyme activity, while avoiding the sudden drop in antibacterial efficiency caused by the short-term burst release of traditional coatings. In Example 12, when the irradiation time was 6 min and the light intensity was 80 mW / cm 2 , when the dosage of the tea polyphenol-cyclodextrin inclusion complex was 12 parts, the antibacterial rate of the prepared composite fiber against Staphylococcus aureus was 99.9%, and the antibacterial rate against Escherichia coli was 99.9%. In Comparative Example 15, the reinforcing fiber was not immersed in the tea polyphenol-cyclodextrin inclusion complex solution for impregnation. When contacting bacteria, the fiber did not have the antibacterial effect of tea polyphenols, and bacteria were prone to grow and reproduce on the fiber surface, resulting in a significant reduction in the antibacterial performance of the composite fiber. In Comparative Example 16, the UV curing time was 20 min. Excessive curing would cause excessive cross-linking of the molecular structure inside the coating, inhibiting the activity of tea polyphenols and affecting the exertion of their antibacterial performance.

[0093] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a bio-based PTT composite fiber, characterized in that: The preparation method is as follows: melt-blend bio-based PTT, poly(lactic-co-glycolic acid), and nanocellulose, add CA@MOF for in-situ crosslinking to obtain the core layer; compound polycaprolactone and chitosan-silver nanoparticles and then coat the core layer by electrospinning to obtain the sheath layer; adsorb tannic acid-modified silica at the core-sheath interface, perform plasma treatment on the core-sheath interface, and then anneal to obtain the reinforced fiber; immerse the reinforced fiber in a tea polyphenol-cyclodextrin inclusion complex solution, and then perform UV curing to obtain the composite fiber.

2. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The preparation method of the core layer is as follows: activate 5 parts of the CA@MOF at 120 °C for 4 h to remove pore moisture to obtain dry CA@MOF; add the bio-based PTT, the poly(lactic-co-glycolic acid), and the nanocellulose into a twin-screw extruder according to a mass ratio of 9-12:4-7:3, set the feeding section temperature to 180-195 °C, the melting section temperature to 195-210 °C, and the discharging section temperature to 190 °C, and add the dry CA@MOF through a side feeding port at the end of the melting section, and extrude to obtain the core layer.

3. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The preparation method of the CA@MOF is as follows: dissolve citric acid in a mixed solution of ethanol and deionized water, perform ultrasonic dispersion, adjust the pH to 3.5 using hydrochloric acid, add ZIF-8, stir and impregnate at 60 °C for 35-45 h, then perform centrifugal separation and vacuum dry the obtained solid to obtain the CA@MOF.

4. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The preparation method of the sheath layer is as follows: dissolve the polycaprolactone with a molecular weight of 80-120 kDa in an acetic acid solution and stir for 12 h, add the chitosan-silver nanoparticles, and perform ultrasonic dispersion to obtain a spinning solution; stretch the core layer into a monofilament with a diameter of 50-80 μm by a melt spinning machine; then perform the electrospinning using a coaxial spinning needle, with a voltage of 40-60 kV and a receiving distance of 12-15 cm, to obtain the sheath layer.

5. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The working gas for the plasma treatment consists of 90% argon and 10% oxygen, with a power of 100-125 W and a treatment time of 30-60 s.

6. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The preparation method of the tannic acid-modified silica is as follows: disperse silica nanoparticles in ethanol, perform ultrasonic treatment and centrifugal separation, and vacuum dry the obtained solid particles to obtain pretreated silica; dissolve tannic acid in a Tris-HCl buffer solution, stir until completely dissolved, add the pretreated silica, introduce nitrogen and stir at 50-70 °C, then perform centrifugation, washing, and drying to obtain the tannic acid-modified silica.

7. The preparation method of a bio-based PTT composite fiber according to claim 1, wherein: The preparation method of the tea polyphenol-cyclodextrin inclusion complex solution is as follows: dissolve 8-15 parts of the tea polyphenol-cyclodextrin inclusion complex in 30 parts of an ethanol aqueous solution, add 0.5 part of a photoinitiator and stir to obtain the tea polyphenol-cyclodextrin inclusion complex solution.

8. The preparation method of a bio-based PTT composite fiber according to claim 1, characterized in that: The irradiation time of the ultraviolet curing is 3 - 8 min, and the light intensity is 70 - 85 mW / cm 2 .

9. A bio-based PTT composite fiber, characterized in that: The raw materials for producing the composite fiber include bio-based PTT, poly(lactic-co-glycolic acid), nanocellulose, CA@MOF, polycaprolactone, chitosan-silver nanoparticles, tannic acid-modified silica, and tea polyphenol-cyclodextrin inclusion complex; the composite fiber is prepared by the preparation method according to any one of claims 1-8.

Images