High-toughness polyglycolic acid composite material, and preparation method and application thereof

Abstract

The application discloses a high-toughness polyglycolic acid composite material and a preparation method and application thereof, and belongs to the technical field of polymer processing. The application obtains a tough polyglycolic acid-based film material with novel beta crystals by solid phase stretching, control of formula design and process parameter regulation, and can simultaneously improve the tensile strength, elongation at break and other performances of the material, and has achieved a breakthrough in improving the physical properties of PGA by using a basic crystal modification method. The application process is simple and easy to control, and has a very good application prospect in the fields of shrink film packaging, high-strength fibers and the like.

Description

Technical Field

[0001] This invention relates to a high-strength and tough polyglycolic acid composite material, its preparation method and application, belonging to the field of polymer processing technology. Background Technology

[0002] With the continuous improvement of people's living standards, plastic products have permeated all sectors of the national economy. In recent years, the negative impact of excessive use of plastic products on the environment and ecosystems has become increasingly serious. Developing and applying environmentally friendly polymer materials is one of the effective strategies to solve these problems. Currently, the main biodegradable plastics on the market include polylactic acid (PLA), polybutylene adipate / terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate-adipate-butylene glycol (PBSA), and polycaprolactone, etc. However, due to their inherent structure, these materials all have poor barrier properties against oxygen and water vapor.

[0003] Polyglycolic acid (PGA), as a biodegradable polyester material, possesses advantages such as high mechanical strength, good chemical resistance, and good barrier properties. In recent years, with breakthroughs in synthesis technology, its cost has decreased significantly, making it a promising candidate for high-barrier packaging materials. However, PGA has inherent disadvantages such as brittleness and opacity. Furthermore, its low crystallinity and poor heat resistance in the preparation of films and other products greatly limit its practical applications. Current research on PGA focuses primarily on improving its mechanical properties and aging resistance. CN1768114A describes the addition of a small amount of aromatic polyester resin to PGA resin to improve its moisture resistance and toughness. CN113088055A describes the blending of PGA and toughening polyester to prepare a high-toughness, high-heat-resistant PGA composite material. CN109575536A describes the blending of PGA and polybutylene succinate-co-butylene terephthalate, with the addition of mesoporous silica, which simultaneously improves the material's mechanical properties and heat and moisture retention capabilities. However, current research on toughening or hydrolysis-resistant modification of polyglycolic acid (PGA) often results in a significant decrease in material strength, making it difficult to achieve excellent overall performance. Therefore, given the current state of PGA research, there is a need to develop a simple and easily controllable process for preparing PGA materials with high strength, high toughness, and high crystallinity, which is of great significance for expanding the practical applications of PGA. Summary of the Invention

[0004] To address the current challenge of achieving both high strength and high toughness in polyglycolic acid films, this invention constructs a β-crystal structure in stretched polyglycolic acid through processes such as hot stretching and annealing. By controlling the crystal form, polyglycolic acid with high strength and high toughness is obtained.

[0005] The basic principle of this invention is that polyglycolic acid (PGA) possesses high mechanical strength and excellent barrier properties due to its unique crystal structure, dense molecular packing, and strong intermolecular forces. However, its low ductility and opacity make it difficult to meet application requirements. Current research on toughening modification of PGA often results in a significant decrease in material strength. This invention first uses stretching and heat treatment processes to highly orient the PGA molecular chains and crystals, constructing a β-type PGA crystal. The highly oriented β-type PGA film exhibits significantly improved strength and toughness compared to ordinary PGA materials. The preparation process is simple and easy to control, and it can be widely used in shrink film packaging materials, high-strength fibers, wires, ropes, and many other fields.

[0006] Specifically, based on the above principles, this invention provides a method for preparing high-strength and tough polyglycolic acid composite materials, comprising the following steps:

[0007] (1) Polyglycolic acid, polymer A, compatibilizer, additives and fillers are melt-blended and extruded through a screw extruder, and then the melt extrudate is rapidly cooled to a temperature of 1.

[0008] (2) The cooled molten extrudate from step (1) is stretched at temperature 2;

[0009] (3) The stretched polyglycolic acid was heat-treated at a temperature of 3.

[0010] Step (3) may be performed or omitted.

[0011] Temperature 1 is 0-80℃, temperature 2 is 35-80℃, and temperature 3 is 40-80℃;

[0012] The polymer A is at least one of the following: adipic acid / butylene terephthalate copolymer, polylactic acid, polycaprolactone, polybutylene succinate, polyhydroxy fatty acid ester, polybutylene succinate / butylene adipate copolymer, and copolymers containing epoxy groups.

[0013] In an embodiment of the present invention, the mass ratio of polyglycolic acid to polymer A is (0.5-5):1. More preferably, it is (1.5-4):1.

[0014] In one embodiment of the present invention, the weight ratio of polyglycolic acid to polymer A is (50-80):(50-20). Specifically, the following combinations are possible: 80 parts polyglycolic acid and 20 parts polymer A; 70 parts polyglycolic acid and 30 parts polymer A; or 60 parts polyglycolic acid and 40 parts polymer A; or 50 parts polyglycolic acid and 50 parts polymer A.

[0015] In embodiments of the present invention, the compatibilizer has a mass fraction of 0.01%-20% relative to the total mass of polyglycolic acid and polymer A. Further options include 0.1%-5%. Specifically, 0.3% is possible.

[0016] In one embodiment of the present invention, the compatibilizer is at least one of a polyfunctional compound or polymer containing multiple epoxy groups or isocyanate groups, or a copolymer containing both polyglycolic acid and polymer A structural units. Specifically, options include: epoxy chain extenders ADR4370, ADR4468, ADR4380, ADR4400, ADR4300, ADR4400, ADR4368; and diisocyanate derivatives such as MDI, HDI, HMDI, LDI, IPDI, and TDI.

[0017] In embodiments of the present invention, the mass fraction of the additive relative to the total mass of polyglycolic acid and polymer A is 0-10%.

[0018] In embodiments of the present invention, the additive is at least one of antioxidants, nucleating agents, anti-hydrolysis agents, lubricants, anti-aging agents, antibacterial agents, antistatic agents, and anti-ultraviolet additives.

[0019] In embodiments of the present invention, the antioxidant has a mass fraction of 0.1-5% relative to the total mass of polyglycolic acid and polymer A. Specifically, 0.3% is an option.

[0020] In embodiments of the present invention, the antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris[2,4-di-tert-butylphenyl]phosphite, and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0021] In embodiments of the present invention, the mass fraction of the lubricant relative to the total mass of polyglycolic acid and polymer A is 0-5%.

[0022] In embodiments of the present invention, the lubricant is at least one selected from solid paraffin, liquid paraffin, polyethylene wax, stearamide, methyl bis-stearamide, N,N-ethylene bis-stearamide, and pentaerythritol stearate.

[0023] In embodiments of the present invention, the mass fraction of the filler additive relative to the total mass of polyglycolic acid and polymer A is 0-5%. More preferably, it is 0.5%-5%. Specifically, it can be 1%-2%.

[0024] In one embodiment of the present invention, the filler is at least one of fibrous filler and lamellar filler, wherein the lamellar filler includes at least one of talc, graphite, graphene, wollastonite, boron nitride, and clay.

[0025] In one embodiment of the present invention, the stretching ratio is 2-15 times; more preferably 3-15 times; specifically, it can be 3, 5, 7, 9, 11, 13, or 15 times.

[0026] In one embodiment of the present invention, temperature 1 is 10-40°C. Specifically, it can be 20°C, 25°C, or 30°C.

[0027] In one embodiment of the present invention, the temperature 2 is 35-80°C. More preferably, it is 40-70°C. Specifically, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0028] In one embodiment of the present invention, temperature 3 is 50-70°C. Specifically, 50°C, 55°C, 60°C, 65°C, and 70°C can be selected.

[0029] The present invention provides a high-strength and high-toughness polyglycolic acid composite material based on the above method.

[0030] The present invention also provides the application of the above-mentioned high-strength and tough polyglycolic acid composite material in the fields of heat shrink film, agriculture, packaging, wire, rope and 3D printing.

[0031] Compared with existing methods for preparing PGA packaging films, the present invention has the following key advantages:

[0032] (1) By controlling the process parameters during the stretching process, this invention obtains a tough polyglycolic acid-based thin film material with a novel β crystal. The new crystal form of PGA can simultaneously improve the physical and mechanical properties of the material, such as tensile strength and elongation at break. This invention represents a breakthrough in improving the physical properties of PGA through basic crystal modification.

[0033] (2) The present invention changes the microcrystalline structure of PGA, adjusts the crystal region size and crystal morphology, and produces a stretch film with high transparency, which is conducive to its expansion in the packaging field.

[0034] (3) By adding reactive compatibilizers or copolymers, the present invention can significantly improve the interfacial interaction between polyglycolic acid and polymer A, reduce the average size of the dispersed phase, and enable the dispersed phase to play a better toughening or other modification effect.

[0035] (4) The method provided by the present invention does not use any solvent, is non-toxic and non-polluting, and the equipment involved is simple and readily available, making it suitable for industrial production. Attached Figure Description

[0036] Figure 1 Two-dimensional wide-angle X-ray scattering images of the polyglycolic acid-based composite films prepared in Example 4 and Comparative Examples 1 and 3 of this invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to embodiments and comparative examples. However, it should be noted that the following embodiments are only used to further illustrate the present invention and should not limit the scope of the present invention.

[0038] The polyglycolic acid involved in the following implementation process has a weight-average molecular weight of 170,000 and a molecular weight distribution of 1.3.

[0039] The polyglycolic acid involved in the following implementation process has a melting temperature of 220°C and a glass transition temperature of 32°C.

[0040] Example 1

[0041] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 3 times at 65°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0042] Example 2

[0043] Compared to Example 1, only the stretch ratio is changed to 5 times:

[0044] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 5 times at 65°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0045] Example 3

[0046] Compared to Example 1, only the stretch ratio is changed to 7 times:

[0047] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 7 times at 65°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0048] Example 4

[0049] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 7 times at 55°C, and finally heat-treated at 50°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0050] Example 5

[0051] Compared to Example 4, only the heat treatment temperature was changed to 70℃:

[0052] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 7 times at 55°C, and finally heat-treated at 60°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0053] Example 6

[0054] Compared to Example 4, only the heat treatment temperature was changed to 90℃:

[0055] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 7 times at 55°C, and finally heat-treated at 70°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0056] Example 7

[0057] Compared to Example 3, talc filler was added:

[0058] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2 parts of talc powder were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was stretched 7 times at 65°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0059] Example 8

[0060] 50 parts of polyglycolic acid, 50 parts of polybutylene succinate, 0.5 parts of MDI diisocyanate, 0.3 parts of tris[2,4-di-tert-butylphenyl]phosphite, and 1 part of talc were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C, and then stretched 5 times at 65°C. Finally, it was heat-treated at 50°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0061] Example 9

[0062] 60 parts of polyglycolic acid, 40 parts of polylactic acid, 0.7 parts of epoxy chain extender ADR4468, 0.3 parts of tris[2,4-di-tert-butylphenyl]phosphite, and 1 part of talc powder were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C, and then stretched 5 times at 65°C. Finally, it was heat-treated at 50°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0063] Example 10

[0064] 70 parts of polyglycolic acid, 30 parts of polyhydroxyalkanoate (molecular weight 450,000), 0.3 parts of diisocyanate MDI, 0.3 parts of tris[2,4-di-tert-butylphenyl]phosphite, and 1 part of boron nitride were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C, and then stretched 5 times at 65°C. Finally, it was heat-treated at 50°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0065] Example 11

[0066] Compared to Example 2, only the stretching method is changed to biaxial stretching;

[0067] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] were thoroughly dried and then added to a twin-screw extruder for melt blending and extrusion granulation to obtain blend A. The dried blend A was melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was biaxially stretched 5 times at 65°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0068] Example 12

[0069] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 11 times at 55°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0070] Comparative Example 1

[0071] After thoroughly drying, 80 parts of polyglycolic acid and 20 parts of poly(butylene adipate / terephthalate) were added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C and then heat-treated at 50°C to obtain a polyglycolic acid-based film material.

[0072] Comparative Example 2

[0073] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] were thoroughly dried and then added to a twin-screw extruder for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C and then heat-treated at 50°C to obtain a polyglycolic acid-based film material.

[0074] Comparative Example 3

[0075] Compared to Example 2, the only difference is that the cooling method is changed to natural cooling:

[0076] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2 parts of talc powder were thoroughly dried and added to a twin-screw extruder for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was naturally cooled to 20°C and then stretched 7 times at 55°C to obtain a polyglycolic acid-based film material.

[0077] Comparative Example 4

[0078] Compared to Example 4, only the heat treatment temperature was changed to 90°C:

[0079] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2 parts of talc powder were thoroughly dried and added to a twin-screw extruder for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C, and then stretched 7 times at 45°C. Finally, it was heat-treated at 90°C to obtain a polyglycolic acid-based film material.

[0080] Comparative Example 5

[0081] Compared to Example 4, only the heat treatment temperature was changed to 120°C:

[0082] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2 parts of talc powder were thoroughly dried and added to a twin-screw extruder for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder. The melt extrudate was rapidly cooled to 20°C, and then stretched 7 times at 55°C. Finally, it was heat-treated at 120°C to obtain a polyglycolic acid-based film material.

[0083] Comparative Example 6

[0084] Compared to Example 2, only the stretching temperature was changed to 80°C:

[0085] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 5 times at 80°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0086] Comparative Example 7

[0087] Compared to Example 2, only the tensile temperature was changed to 90°C:

[0088] 80 parts of polyglycolic acid, 20 parts of polybutylene adipate / terephthalate, 0.3 parts of epoxy chain extender ADR4370, and 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were thoroughly dried and then added to a twin-screw extruder in the specified weight ratio for melt blending and extrusion granulation to obtain blend A. The dried blend A was then melt-extruded through a single-screw extruder, and the melt extrudate was rapidly cooled to 20°C. Subsequently, the cooled melt extrudate was uniaxially stretched 5 times at 90°C to obtain a high-strength and tough polyglycolic acid-based film material.

[0089] After thorough drying, the polyglycolic acid materials obtained in Examples 1-12 were tested for tensile properties at room temperature according to the standard method of GB / T 1040-2006. The tensile rate was set to 10 mm / min, and at least 5 specimens of the same sample were tested and the average value was taken. The crystallinity of the polyglycolic acid material was calculated by heating 5-8 mg of the sample from 0℃ to 250℃ at a rate of 20℃ / min using DSC. The azimuth diffraction intensity distribution curve of the sample was obtained by cyclic integration of the azimuth angle using 2D-WAXD testing, and its orientation degree was calculated. The results are shown in Table 1.

[0090] Table 1 Mechanical properties, crystallinity, and orientation degree of the embodiments.

[0091] Example Tensile strength (MPa) Elongation at break (%) Total crystallinity (%) β-crystal crystallinity (%) Orientation Example 1 375 325 40 35 0.32 Example 2 91 219 47 42 0.43 Example 3 117 168 52 47 0.51 Example 4 121 187 55 51 0.53 Example 5 128 165 59 55 0.50 Example 6 132 129 61 58 0.51 Example 7 125 111 56 51 0.52 Example 8 79 127 59 56 0.49 Example 9 179 127 52 55 0.44 Example 10 192 147 51 46 0.43 Example 11 147 171 46 36 0.52 Example 12 170 68 48 41 0.68

[0092] The polyglycolic acid materials obtained in Comparative Examples 1-7 were subjected to the same testing procedure to determine their performance and quality. The results are shown in Table 2.

[0093] Table 2 Comparative examples: mechanical properties, crystallinity, and orientation.

[0094] Comparative Example Tensile strength (MPa) Elongation at break (%) Crystallinity (%) Relative content of β crystals (%) Orientation Comparative Example 1 46 21 42 0 0.01 Comparative Example 2 53 48 40 0 0.01 Comparative Example 3 114 62 49 6 0.48 Comparative Example 4 120 43 56 0 0.46 Comparative Example 5 123 31 58 0 0.45 Comparative Example 6 108 51 51 0 0.41 Comparative Example 7 115 42 55 0 0.41

[0095] Figure 1 The figures show two-dimensional wide-angle X-ray scattering (BPS) patterns of the polyglycolic acid-based composite materials prepared in Example 4 and Comparative Examples 1 and 3 of this invention. As can be seen from the figures, Comparative Example 1, having undergone no stretching treatment, exhibits a regular circular BPS pattern, demonstrating isotropic properties. In contrast, the BPS patterns of Comparative Examples 3 and Example 4 show significant anisotropy along the equator and meridian, indicating that stretching caused a clear orientation (crystal) in the molecular chains and crystals. Furthermore, Comparative Example 3 exhibits typical α-type PGA scattering, while Example 4 shows a β-crystal structure scattering pattern. The anisotropy of Example 4 is significantly stronger than that of Comparative Example 1, indicating a higher degree of orientation in Example 4.

[0096] As can be seen from Tables 1 and 2, the mechanical properties of the polyglycolic acid / poly(adipic acid) / butylene terephthalate blend (Comparative Example 2) after the addition of a compatibilizer are somewhat improved compared to the direct blend (Comparative Example 1), but the tensile strength and elongation at break are still at a low level. The molecular chains inside the material are basically in a random arrangement, and the crystallinity is low. In Comparative Example 3, the PGA film stretched after natural cooling shows a significant increase in tensile strength with increasing crystallinity and orientation. However, since most of the formed crystals are traditional α-crystals, although the tensile strength increases significantly with increasing crystallinity and orientation, its elongation at break decreases (62%). Similarly, in Comparative Examples 4-7, only traditional α-crystals can be formed, and the elongation at break is not significantly improved. In this invention, however, oriented β-type polyglycolic acid is constructed using processes such as hot stretching, which significantly improves the strength and toughness of the polyglycolic acid-based film. As can be seen from the film materials with different stretching ratios (Examples 1-3), increasing the stretching ratio is beneficial for the PGA molecular chains to align along the stress direction, resulting in increased β-crystal content and orientation degree. This significantly improves the tensile strength of the material, while reducing the elongation at break, but both are still much higher than the comparative samples. On the other hand, this invention can also construct β-type polyglycolic acid through stretching and heat treatment processes, further improving its performance. Appropriate stretching and annealing temperatures play a crucial role, affecting the β-crystal content and orientation degree, thus influencing the final properties of the material (as in Examples 2-7). Other polyglycolic acid-based materials and biaxially stretched polyglycolic acid (as in Examples 8-12) were prepared using the same method, and their mechanical properties, especially the elongation at break, were significantly higher than the comparative samples. In summary, this invention prepares a strong and tough polyglycolic acid composite material that is simple, practical, and easy to industrialize, and is expected to be applied in shrink film packaging materials, high-strength fibers, and other fields.

[0097] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this invention, technical features of the above embodiments or different embodiments can also be combined, and many other variations of different aspects of the invention as described above exist, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for preparing a high-strength and high-toughness polyglycolic acid composite material, characterized in that, The process includes the following: (1) Polyglycolic acid, polymer A, compatibilizer, additives and fillers are melt-blended and extruded through a screw extruder, and then the melt extrudate is rapidly cooled to a temperature of 1. (2) The cooled molten extrudate from step (1) is stretched at temperature 2; (3) The stretched polyglycolic acid is heat-treated at a temperature of 3. Step (3) may be performed or omitted. Temperature 1 is 0-80 ℃, temperature 2 is 40-70 ℃, and temperature 3 is 40-60 ℃; The polymer A is at least one of the following: adipic acid / butylene terephthalate copolymer, polylactic acid, polycaprolactone, polybutylene succinate, polyhydroxy fatty acid ester, polybutylene succinate / butylene adipate copolymer, and copolymers containing epoxy groups. The weight ratio of polyglycolic acid to polymer A is (50-80):(50-20); The compatibilizer has a mass fraction of 0.01%-20% relative to the total mass of polyglycolic acid and polymer A; the compatibilizer is at least one of a polyfunctional compound or polymer containing multiple epoxy groups or isocyanate groups, or a copolymer containing both polyglycolic acid and polymer A structural units. The mass fraction of the additive relative to the total mass of polyglycolic acid and polymer A is 0-10%; the additive is at least one of antioxidants, nucleating agents, anti-hydrolysis agents, lubricants, anti-aging agents, antibacterial agents, antistatic agents, and anti-UV additives. The mass fraction of the filler relative to the total mass of polyglycolic acid and polymer A is 0-5%; the filler is at least one of fibrous filler and lamellar filler, wherein the lamellar filler includes at least one of talc, graphite, graphene, wollastonite, boron nitride, and clay.

2. The method according to claim 1, characterized in that, The stretching ratio is 2-15 times.

3. The method according to any one of claims 1-2, characterized in that, Temperature 1 is 10-40℃; Temperature 2 is 40-60℃; Temperature 3 is 50-60℃.

4. A high-strength and high-toughness polyglycolic acid composite material prepared by the method according to any one of claims 1-3.

5. The application of the high-strength and high-toughness polyglycolic acid composite material according to claim 4 in the fields of heat shrink film, agriculture, packaging, wire, rope and 3D printing.

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