Degradable PLA composite material and preparation method thereof

Abstract

The application discloses a degradable PLA composite material and a preparation method thereof, and belongs to the technical field of polylactic acid materials. The degradable PLA composite material comprises the following raw materials in mass fractions: 80-95 parts of polylactic acid, 5-15 parts of carboxyl-terminated hyperbranched polycaprolactone, 3-5 parts of potassium titanate whisker, 0.1-3 parts of antioxidant, 1-5 parts of compatilizer and 1-2 parts of hydrolysis inhibitor. The carboxyl-terminated hyperbranched polycaprolactone is compounded with the polylactic acid, a large number of flexible segments are introduced into the polylactic acid matrix material, and the problem of large brittleness of the polylactic acid can be well solved; the potassium titanate whisker is further added into the composite material, and the excellent strength and stability of the potassium titanate whisker can improve the thermal stability and mechanical properties of the material. The potassium titanate whisker can be used as a nucleating agent to compensate for the problem of the decreased crystallization performance of the polylactic acid caused by the compounding of the carboxyl-terminated hyperbranched polycaprolactone, improve the crystallinity of the polylactic acid composite material, and thus improve the heat resistance of the polylactic acid composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polylactic acid materials, and particularly relates to a degradable PLA composite material and a preparation method thereof. BACKGROUND

[0002] With the increasing pollution caused by plastics to the environment and the continuous consumption of petroleum resources, it is urgent to develop green and environmentally friendly renewable materials that can be biodegraded. Polylactic acid (PLA) is a new green biodegradable material, which has good biocompatibility, degradability and physical and mechanical properties, and can be processed by various processes such as injection molding, extrusion and spinning to prepare different degradable plastic products, and is widely used in clothing, packaging, agriculture, automobiles, electronics, biological medicine and engineering and many other fields.

[0003] However, polylactic acid has defects such as brittleness, poor heat resistance and low melt strength. Pure polylactic acid often breaks when subjected to external force at room temperature, and the mechanical properties cannot be significantly improved by changing the production process, thereby limiting the application range of polylactic acid. Therefore, it is urgent to develop a material that can overcome the defects of poor toughness and maintain degradability to meet the application requirements in various fields. SUMMARY

[0004] The purpose of the present application is to provide a degradable PLA composite material and a preparation method thereof to solve the problems of brittleness and poor heat resistance of polylactic acid materials.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] In a first aspect, the present application provides a degradable PLA composite material, comprising the following raw materials by mass fraction:

[0007] 80-95 parts of polylactic acid;

[0008] 5-15 parts of carboxyl-terminated hyperbranched polycaprolactone;

[0009] 3-5 parts of potassium titanate whiskers;

[0010] 0.1-3 parts of antioxidant;

[0011] 1-5 parts of compatibilizer;

[0012] 1-2 parts of hydrolysis-resistant agent.

[0013] Preferably, the compatibilizer is an epoxy reactive compatibilizer.

[0014] More preferably, the compatibilizer is an ADR compatibilizer.

[0015] Preferably, the polylactic acid is levorotatory polylactic acid.

[0016] Preferably, the antioxidant includes a combination of one or more of antioxidant 1010, antioxidant 1790, antioxidant 1076, antioxidant 168 and antioxidant 626.

[0017] Preferably, the hydrolysis inhibitor includes a combination of one or more of monomeric carbodiimide hydrolysis inhibitors and polymeric carbodiimide hydrolysis inhibitors.

[0018] By adopting the technical scheme, the flexible polycaprolactone has excellent processability, and after being blended and compounded with polylactic acid, the flexibility of the polylactic acid can be significantly improved. The hyperbranched polycaprolactone has more flexible long chains and ester groups than the general linear polycaprolactone, the activity between the molecular chains is high, the flexibility and flexibility are higher, and the highly branched structure of the hyperbranched polyester is combined, so that the toughening effect of the polycaprolactone on the polylactic acid is further improved.

[0019] The polarity of the hyperbranched polycaprolactone is also improved compared with the polycaprolactone, and the dispersibility in the polylactic acid is enhanced. The hyperbranched polycaprolactone of the application is also subjected to carboxylation treatment, and the terminal carboxyl groups in the obtained hyperbranched polyester can react with the epoxy groups of the epoxy group reactive compatilizer used in the application to generate a block copolymer in situ, linking the polylactic acid matrix and the terminal carboxyl hyperbranched polycaprolactone in the system, thereby improving the interfacial adhesion between the two phases and playing a compatibilizing effect, and enhancing the interfacial bonding force between the polylactic acid and the terminal carboxyl hyperbranched polyester. In addition, the hyperbranched structure of the terminal carboxyl hyperbranched polycaprolactone can form a certain cross-linked three-dimensional network structure in the system, which can absorb impact energy when subjected to external force impact, thereby improving the impact resistance of the material, and improving the problem of brittleness of polylactic acid and enhancing the flexibility of the composite material. In addition, the terminal carboxyl hyperbranched polycaprolactone is a biodegradable material, which does not affect the degradability of the polylactic acid composite material, and can also regulate the degradation rate of the polylactic acid to a certain extent.

[0020] However, the tensile strength of the polylactic acid modified by the terminal carboxyl hyperbranched polycaprolactone is decreased, and since the terminal carboxyl hyperbranched polycaprolactone itself has general heat resistance, the heat resistance of the composite material after being compounded with the polylactic acid is not improved and even decreased due to the influence on the crystallization performance of the polylactic acid. In order to improve this problem, potassium titanate whiskers are added to the composite material of the application. The potassium titanate whisker itself has very high strength, as well as excellent chemical stability and thermal stability. After being mixed with the polylactic acid, the tensile strength and thermal stability of the material can be significantly improved.

[0021] In addition, the fine-sized potassium titanate whisker can be used as a heterogeneous nucleating agent of the polylactic acid material, providing additional nucleation sites for the polylactic acid molecular chain, reducing the energy barrier required during crystallization, and promoting the crystallization process of the polylactic acid; and the high aspect ratio of the potassium titanate whisker also promotes the formation of an ordered structure inside the polylactic acid system, thereby increasing the crystallinity of the polylactic acid composite material, and thus improving the heat resistance of the polylactic acid composite material.

[0022] Preferably, the raw material of the carboxyl-terminated hyperbranched polycaprolactone comprises hyperbranched polycaprolactone and dianhydride in a molar ratio of 1:(12-15).

[0023] Preferably, the raw material of the hyperbranched polycaprolactone comprises 2,2-bishydroxymethyl propionic acid and caprolactone in a molar ratio of 1:(20-22).

[0024] More preferably, the hyperbranched polycaprolactone is prepared by the following method:

[0025] 2,2-bishydroxymethyl propionic acid and caprolactone are mixed, a tin catalyst is added, the temperature is raised to 100-120°C under a nitrogen atmosphere, stirring is performed for 2-3h, the temperature is then raised to 145-150°C under vacuum, stirring is performed for 4-5h, the temperature is then raised to 170-180°C, stirring is performed for 12-15h, and then the hyperbranched polycaprolactone is obtained through standing, dissolution, precipitation, and drying.

[0026] Preferably, the tin catalyst comprises one or more of stannous octoate and dibutyltin dilaurate in combination; and the amount of the tin catalyst added is 0.02-0.1wt% of the mass of the caprolactone.

[0027] Preferably, the dianhydride comprises one or more of succinic anhydride, maleic anhydride, phthalic anhydride, and adipic anhydride in combination.

[0028] Preferably, the carboxyl-terminated hyperbranched polycaprolactone is prepared by the following method: the hyperbranched polycaprolactone and the dianhydride are added to a solvent, the temperature is raised to 85-95°C after mixing, the reaction is stopped after stirring until the acid value of the system is constant, and then the carboxyl-terminated hyperbranched polycaprolactone is obtained through precipitation and drying.

[0029] Preferably, the solvent comprises one or more of dibenzoylmethane, N,N-dimethylformamide, and N-methylpyrrolidone in combination.

[0030] By adopting the technical scheme, the carboxyl-terminated hyperbranched polycaprolactone is obtained by the reaction between the dianhydride and the hydroxyl on the hyperbranched polycaprolactone molecular chain. The hyperbranched polycaprolactone treated by the carboxylation has more polar groups introduced on the molecular chain, can form intermolecular forces with the polar groups in the polylactic acid, the intermolecular interaction can improve the binding force and dispersibility of the carboxyl-terminated hyperbranched polycaprolactone in the polylactic acid, in the preparation process, the carboxyl-terminated hyperbranched polycaprolactone can be uniformly distributed in the polylactic acid matrix and react with the compatilizer, thereby improving the compatibility and interfacial bonding force between the two; more active sites also form a stable network structure in the material, thereby improving the ductility of the composite material and showing higher impact performance and comprehensive mechanical properties.

[0031] And by the reaction between the carboxyl-terminated hyperbranched polycaprolactone and the compatilizer, the processing performance of the polylactic acid composite material is also improved, the flowability is improved, which is helpful to improve the molding efficiency and reduce the internal defects of the material, thereby improving the toughness of the material. The introduction of the carboxyl group can also control the biodegradation behavior of the polylactic acid composite material. Since the carboxyl group can accelerate the hydrolysis reaction, the degradation rate of the obtained PLA composite material is improved and the rate is controllable.

[0032] Preferably, the potassium titanate whisker is modified by sodium lignosulfonate.

[0033] Preferably, the mass ratio of the potassium titanate whisker to sodium lignosulfonate is 1:(0.02-0.06).

[0034] Preferably, the potassium titanate whisker is modified by the following method: sodium lignosulfonate is dissolved in deionized water, the potassium titanate whisker and an acidic catalyst are added, stirring, dispersing and impregnating for 8-12 hours, and then centrifuging, washing, drying and grinding to obtain the modified potassium titanate whisker.

[0035] Preferably, the acidic catalyst includes one or more of a combination of p-toluenesulfonic acid, sulfuric acid, hydrochloric acid and phosphoric acid; the addition amount of the acidic catalyst is 0.01-0.05wt% of the mass of the potassium titanate whisker.

[0036] The particle size of the potassium titanate whisker is small, and the potassium titanate whisker is prone to agglomeration or bridging phenomenon in the processing process, which affects the uniform dispersion of the potassium titanate whisker in the polylactic acid composite material. The uneven distribution of the potassium titanate whisker as a reinforcing phase in the polylactic acid composite material can cause the use performance of the composite material to decrease and the uniformity of the processing and manufacturing to be poor. Therefore, the potassium titanate whisker needs to be surface modified.

[0037] By adopting the technical scheme, the potassium titanate whisker is surface treated by the sodium lignosulfonate, and the sodium lignosulfonate is connected on the surface of the potassium titanate whisker by the reaction between the sulfonic acid group in the sodium lignosulfonate and the hydroxyl group on the surface of the potassium titanate whisker or by the hydrogen bond or other intermolecular forces. On one hand, the molecular chain of the sodium lignosulfonate can form a spatial barrier in the potassium titanate whisker to hinder the mutual attraction and agglomeration of the potassium titanate whiskers, and improve the dispersibility of the potassium titanate whisker in the polylactic acid matrix; on the other hand, the sodium lignosulfonate is a natural polymer lignin modified by sulfonation and has the biodegradability, and will not affect the biodegradability of the polylactic acid composite material.

[0038] In addition, after the modification treatment of the sodium lignosulfonate, a large number of polar groups such as sulfonic acid groups are introduced on the surface of the potassium titanate whisker, which can further improve the bonding force of the potassium titanate whisker in the polylactic acid composite material, will not be precipitated during use, and can participate in the three-dimensional crosslinking network between the carboxyl-terminated hyperbranched polycaprolactone and the polylactic acid, to improve the mechanical properties of the material. Meanwhile, the main chain molecule of the sodium lignosulfonate is the basic skeleton of lignin and has a certain rigidity, which can improve the heat resistance of the polylactic acid composite material when participating in the crosslinking network structure.

[0039] In the second aspect, the application provides a preparation method of the degradable PLA composite material, which comprises the following process steps:

[0040] S1. drying the polylactic acid at 60-80 DEG C for 6-8 hours;

[0041] S2. taking the dried polylactic acid, the carboxyl-terminated hyperbranched polycaprolactone, the potassium titanate whisker, the compatilizer, the antioxidant and the anti-hydrolysis agent according to the corresponding mass fraction, and stirring and mixing for 10-30 minutes to obtain a mixture;

[0042] S3. melting and plasticizing the mixture to obtain the degradable PLA composite material by extruding and granulating.

[0043] Preferably, the melting and plasticizing temperature is 190-210 DEG C.

[0044] The application has the following beneficial effects:

[0045] 1. This invention employs carboxyl-terminated hyperbranched polycaprolactone (PCV) composites with polylactic acid (PLA), which significantly improves the impact resistance of the material and addresses the problem of high brittleness in PLA. The hyperbranched structure increases the content of flexible molecular chains, enhancing the ability to absorb external impact energy and strengthening the flexibility of the PLA composite. Furthermore, the carboxylation treatment of the hyperbranched PCV increases its polarity, thereby improving its dispersibility in the matrix. Additionally, the terminal carboxyl groups and the terminal hydroxyl groups in PLA can react with epoxy-based reactive compatibilizers in the system, improving interfacial bonding and compatibility. The resulting cross-linked network structure further enhances the mechanical properties of the material.

[0046] 2. The composite material of this invention also contains potassium titanate whiskers, which can compensate for the decrease in tensile strength and poor heat resistance caused by the addition of end-carboxyl hyperbranched polycaprolactone. Furthermore, to further improve the improving effect of potassium titanate whiskers, sodium lignosulfonate is used to modify the potassium titanate whiskers, improving their dispersibility in the polylactic acid matrix and allowing them to participate in the formation of the crosslinking network, thereby further improving the heat resistance and mechanical properties of the composite material without affecting its biodegradability. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] Preparation Example

[0049] Preparation Example 1: Terminal Carboxyl Hyperbranched Polycaprolactone

[0050] Preparation Example 1-1: A carboxyl-terminated hyperbranched polycaprolactone was prepared according to the following method:

[0051] 2,2-Dimethylolpropionic acid and caprolactone were mixed at a molar ratio of 1:20, and 1.5 g of stannous octoate was added. Under a nitrogen atmosphere, the temperature was raised to 120°C and stirred for 2 h. Then, under vacuum, the temperature was raised to 150°C and stirred for 5 h. The temperature was then raised to 180°C and stirred for 12 h. After standing, dissolving, precipitating and drying, hyperbranched polycaprolactone was obtained.

[0052] The hyperbranched polycaprolactone and succinic anhydride obtained above were added to N,N-dimethylformamide at a molar ratio of 1:13. After mixing, the temperature was raised to 85-95°C, and the reaction was stopped after stirring until the acid value of the system was constant. Then, the reaction was obtained by precipitation and drying to obtain carboxyl-terminated hyperbranched polycaprolactone.

[0053] Preparation Example 1-2, a carboxyl-terminated hyperbranched polycaprolactone, differs from Preparation Example 1-1 only in that the molar ratio of 2,2-bishydroxymethyl propionic acid and caprolactone is 1:22; and the molar ratio of the hyperbranched polycaprolactone and succinic anhydride is 1:12.

[0054] Preparation Example 1-3, a carboxyl-terminated hyperbranched polycaprolactone, differs from Preparation Example 1-1 only in that the molar ratio of the hyperbranched polycaprolactone and succinic anhydride is 1:15.

[0055] Preparation Example 1-4, a carboxyl-terminated hyperbranched polycaprolactone, differs from Preparation Example 1-1 only in that the molar ratio of the hyperbranched polycaprolactone and succinic anhydride is 1:10.

[0056] Preparation Example 1-5, a carboxyl-terminated hyperbranched polycaprolactone, differs from Preparation Example 1-1 only in that the molar ratio of the hyperbranched polycaprolactone and succinic anhydride is 1:16.

[0057] Preparation Example 1-6, a hyperbranched polycaprolactone, is prepared according to the following method:

[0058] 2,2-bishydroxymethyl propionic acid and caprolactone are mixed in a molar ratio of 1:20, 1.5 g of stannous octoate is added, the temperature is raised to 120°C under a nitrogen atmosphere, and the reaction is stirred for 2 h, then the temperature is raised to 150°C under vacuum, and the reaction is stirred for 5 h, then the temperature is raised to 180°C, and the reaction is stirred for 12 h, and then the hyperbranched polycaprolactone is obtained by standing, dissolving, precipitating, and drying.

[0059] Preparation Example 2 Modification of potassium titanate whiskers

[0060] Preparation Example 2-1, a potassium titanate whisker, is modified according to the following method:

[0061] 0.4 g of sodium lignosulfonate is dissolved in 100 mL of deionized water, 10 g of potassium titanate whiskers (0.1-0.3 μm in diameter) and 0.003 g of hydrochloric acid are added, and the mixture is stirred and dispersed and immersed for 10 h, and then the modified potassium titanate whiskers are obtained by centrifugation, washing, drying, and grinding.

[0062] Preparation Example 2-2, a potassium titanate whisker, differs from Preparation Example 2-1 only in that the amount of sodium lignosulfonate added is 0.2 g.

[0063] Preparation Example 2-3, a potassium titanate whisker, differs from Preparation Example 2-1 only in that the amount of sodium lignosulfonate added is 0.6 g.

[0064] Preparation Example 2-4, a potassium titanate whisker, is modified according to the following method:

[0065] Take 0.4 g of γ-glycidyloxypropyltrimethoxysilane and deionized water to obtain an amino silane coupling agent hydrolysate, wherein the mass ratio of deionized water to phthalate coupling agent is 7:1; disperse 10 g of potassium titanate whisker in 100 nL of methanol solution, add the amino silane coupling agent hydrolysate, stir for 6 h, and then centrifuge, wash and dry to obtain modified potassium titanate whisker.

[0066] Example

[0067] Example 1, a degradable PLA composite material, is prepared according to the following method:

[0068] S1. Dry the levorotatory polylactic acid (weight average molecular weight of 10000-200000 g / mol) at 80°C for 6 h;

[0069] S2. Weigh 9 kg of dried polylactic acid, 1 kg of carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1, 0.4 kg of potassium titanate whisker (diameter of 0.1-0.3 μm), 0.3 kg of ADR compatibilizer, 0.2 kg of antioxidant (including antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1), and 0.1 kg of monomeric carbodiimide hydrolysis inhibitor, and stir and mix for 20 min to obtain a mixture;

[0070] S3. Melt plasticize the mixture to obtain a degradable PLA composite material by extrusion and granulation, wherein the melt plasticizing temperature is 200°C.

[0071] Example 2 and Example 3, a degradable PLA composite material, differ from Example 1 only in that the proportion of raw materials is adjusted, as shown in Table 1:

[0072] Table 1 Formulation table of Example 1-Example 3

[0073]

[0074]

[0075] The carboxyl-terminated hyperbranched polycaprolactone used is the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0076] Example 4, a degradable PLA composite material, differs from Example 1 only in that an equal amount of carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-2 is used to replace the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0077] Example 5, a degradable PLA composite material, differs from Example 1 only in that an equal amount of carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-3 is used to replace the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0078] Example 6, a degradable PLA composite, differs from Example 1 only in that the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-4 is used instead of the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0079] Example 7, a degradable PLA composite, differs from Example 1 only in that the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-5 is used instead of the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0080] Example 8, a degradable PLA composite, differs from Example 1 only in that the potassium titanate whisker prepared in Preparation Example 2-1 is used instead of the potassium titanate whisker.

[0081] Example 9, a degradable PLA composite, differs from Example 8 only in that the potassium titanate whisker prepared in Preparation Example 2-2 is used instead of the potassium titanate whisker prepared in Preparation Example 2-1.

[0082] Example 10, a degradable PLA composite, differs from Example 8 only in that the potassium titanate whisker prepared in Preparation Example 2-3 is used instead of the potassium titanate whisker prepared in Preparation Example 2-1.

[0083] Example 11, a degradable PLA composite, differs from Example 8 only in that the potassium titanate whisker prepared in Preparation Example 2-4 is used instead of the potassium titanate whisker prepared in Preparation Example 2-1.

[0084] Comparative Example

[0085] Comparative Example 1, a degradable PLA composite, differs from Example 1 only in that the amount of the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1 is 0.2 kg.

[0086] Comparative Example 2, a degradable PLA composite, differs from Example 1 only in that the amount of the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1 is 2 kg.

[0087] Comparative Example 3, a degradable PLA composite, differs from Example 1 only in that the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-6 is used instead of the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0088] Comparative Example 4, a degradable PLA composite, differs from Example 1 only in that the amount of the potassium titanate whisker is 0.1 kg.

[0089] Comparative Example 5, a degradable PLA composite, differs from Example 1 only in that the amount of potassium titanate whiskers added is 0.6 kg.

[0090] Comparative Example 6, a degradable PLA composite, differs from Example 1 only in that an equal amount of polycaprolactone (average molecular weight 10000 g / mol) is used to replace the carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1.

[0091] Comparative Example 7, a degradable PLA composite, differs from Example 1 only in that no carboxyl-terminated hyperbranched polycaprolactone prepared in Preparation Example 1-1 is added.

[0092] Comparative Example 8, a degradable PLA composite, differs from Example 1 only in that no potassium titanate whiskers are added.

[0093] Comparative Example 9, a degradable PLA composite, differs from Example 1 only in that an equal amount of POM compatibilizer (density 1.1-1.3 g / cm 3 ) is used to replace the ADR compatibilizer.

[0094] Performance test

[0095] 1. Mechanical property test:

[0096] (1) Tensile property test: According to the relevant records in GB / T 1040.2-2022 “Determination of tensile properties of plastics Part 2: test conditions for moulded and extruded plastics”, the tensile strength and elongation at break of the PLA composite obtained in the examples and comparative examples are tested.

[0097] (2) Impact property test: According to the relevant records in GB / T 1843-2008 “Determination of Izod impact strength of plastics”, the impact strength of the PLA composite obtained in the examples and comparative examples is tested. The test results are shown in Table 2.

[0098] 2. Heat resistance test: According to the relevant records in ISO 75-2:2013 “Determination of the heat distortion temperature of plastics Part 2: plastics and ebonite”, the heat distortion temperature of the PLA composite obtained in the examples and comparative examples is tested under the condition of 0.45 MPa load, 120 ℃ / h. The test results are shown in Table 3.

[0099] Table 2 Test results of mechanical property test

[0100]

[0101] Table 3 Test results of heat resistance test

[0102]

[0103]

[0104] According to Table 2 and Table 3, combined with Example 1, Example 2-Example 5, it can be seen that the mechanical properties and heat resistance of Example 2-Example 5 have no obvious change compared with Example 1, and the difference between Example 2-Example 5 and Example 1 is only that the raw materials and the raw material ratio are adjusted within the required range, and the performance of the obtained PLA composite material has no obvious change compared with Example 1.

[0105] Combined with Example 1, Example 6, Example 7 and Comparative Example 3, it can be seen that the elongation at break and impact strength of Example 6, Example 7 and Comparative Example 3 have decreased compared with Example 1, and the heat distortion temperature has also decreased, and the decrease of Comparative Example 3 is more obvious, indicating that the mechanical properties and heat resistance of Example 6, Example 7 and Comparative Example 3 have decreased compared with Example 1. The reason is that the difference between Example 6, Example 7 and Comparative Example 3 and Example 1 is only that the carboxyl content of the carboxyl-terminated hyperbranched polycaprolactone used is changed outside the required range, among which the carboxyl content in Example 6 is reduced, the number of active groups between the compatilizer is reduced, the dispersibility in polylactic acid is reduced, the crosslinking network density is reduced, and the performance improvement effect of the material is reduced, while in Comparative Example 3, no carboxylation treatment is performed, and the performance decreases more significantly; the carboxylation degree is increased in Example 7, and the introduction of a large number of polar groups will increase the attraction between the carboxyl-terminated hyperbranched polycaprolactone, which is easy to agglomerate, and the dispersibility in the polylactic acid matrix is reduced, and the performance of the material is reduced.

[0106] Combined with Example 1, Example 8, Example 9-Example 11, it can be seen that the tensile strength and heat distortion temperature of Example 8 have improved compared with Example 1, and the changes of Example 9 and Example 10 compared with Example 8 are not obvious, and the performance of Example 11 compared with Example 1 is not obviously improved. The reason is that the difference between Example 8 and Example 1 is that the potassium titanate whisker used is modified by sodium lignosulfonate, and the dispersibility of the potassium titanate whisker in the polylactic acid matrix is obviously increased, and the introduction of the molecular chain of sodium lignosulfonate can also participate in the formation of the crosslinking network, and the rigid skeleton can also improve the heat resistance of the material without affecting the biodegradability. The difference between Example 9 and Example 10 and Example 8 is only that the amount of the modifier sodium lignosulfonate is changed within the required range, and the effect on the performance is not obvious. In Example 11, the potassium titanate whisker is modified by silane coupling agent, which can also improve the dispersibility to a certain extent, but it does not help to improve the flexibility and heat resistance of the material.

[0107] Compared with Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 7, it can be seen that the mechanical properties and heat resistance of Comparative Example 1, Comparative Example 2 and Comparative Example 7 all decrease compared with Example 1, and the decrease of Comparative Example 7 is the most obvious. The reason is that the only difference between Comparative Example 1, Comparative Example 2 and Comparative Example 7 and Example 1 is that the addition amount of the carboxyl-terminated hyperbranched polycaprolactone is adjusted. The addition amount of the carboxyl-terminated hyperbranched polycaprolactone is reduced in Comparative Example 1, which greatly reduces the flexible chain segment in the polylactic acid composite material, reduces the flexibility and impact resistance of the material. In Comparative Example 7, no carboxyl-terminated hyperbranched polycaprolactone is added, and the performance decreases more obviously. In Comparative Example 2, the addition amount of the carboxyl-terminated hyperbranched polycaprolactone is increased. The introduction of a large amount of hyperbranched structure and polar groups will increase the crosslinking structure density and reduce the free activity of the molecular chain, which is not conducive to the improvement of flexibility.

[0108] Compared with Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 8, it can be seen that the mechanical properties and heat resistance of Comparative Example 4, Comparative Example 5 and Comparative Example 8 all decrease compared with Example 1, and the decrease of Comparative Example 8 is the most obvious. The reason is that the only difference between Comparative Example 4, Comparative Example 5 and Comparative Example 8 and Example 1 is that the addition amount of potassium titanate whisker is adjusted. In Comparative Example 4, the addition amount of potassium titanate whisker is reduced, which reduces the improvement effect of the tensile strength of the composite material, and the lack of potassium titanate whisker as a nucleating agent for heterogeneous nucleation of polylactic acid causes the heat resistance of the composite material to decrease. In Comparative Example 8, no potassium titanate whisker is added, and the tensile strength and heat resistance decrease more obviously. In Comparative Example 5, the addition amount of potassium titanate whisker is increased. Excessive addition will cause the aggregation of small-size potassium titanate whiskers, which will affect the processing performance and the improvement of the mechanical properties and heat resistance of the material.

[0109] Compared with Example 1 and Comparative Example 6, it can be seen that the mechanical properties and heat resistance of Comparative Example 6 decrease obviously compared with Example 1. The reason is that linear polycaprolactone is used in Comparative Example 6. On the one hand, the lack of hyperbranched structure reduces the impact absorption of the composite material, and the impact resistance of the material decreases. On the other hand, polycaprolactone is a non-polar polymer, which has poor compatibility when it is compounded with polylactic acid. The reactivity between polycaprolactone and the compatibilizer is very low, which cannot improve the interfacial bonding force between them, and it is difficult to form a stable crosslinking network, so the performance of the material decreases.

[0110] It can be seen from the combination of Embodiment 1 and Comparative Example 9 that the mechanical properties and heat resistance of Comparative Example 9 are decreased compared with Embodiment 1, and the reason is that the compatilizer used in Comparative Example 9 is a non-reactive compatilizer. Although the non-reactive compatilizer can increase the compatibility between the carboxyl-terminated hyperbranched polycaprolactone and polylactic acid to a certain extent, compared with the reactive compatilizer, the combination between them is only based on intermolecular force, rather than forming a block copolymer, which can significantly increase the binding force between them and is less affected by external force, and also cannot help the composite material form a stable cross-linked network structure, so the performance is decreased.

[0111] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0112] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A degradable PLA composite, characterized in that, The raw materials include the following mass fractions: Polylactic acid 80-95 parts; Carboxyl-terminated hyperbranched polycaprolactone 5-15 parts; Potassium titanate whisker 3-5 parts; Antioxidant 0.1-3 parts; Compatibilizer 1-5 parts; Anti-hydrolysis agent 1-2 parts; The raw material of the carboxyl-terminated hyperbranched polycaprolactone includes hyperbranched polycaprolactone and dianhydride in a molar ratio of 1:(12-15); the raw material of the hyperbranched polycaprolactone includes 2,2-dimethylol propionic acid and caprolactone in a molar ratio of 1:(20-22); The potassium titanate whisker is subjected to modification treatment with sodium lignosulfonate; The compatibilizer is an epoxy reactive compatibilizer.

2. The degradable PLA composite of claim 1, wherein, The dianhydride includes a combination of one or more of succinic anhydride, maleic anhydride, phthalic anhydride and adipic anhydride.

3. The degradable PLA composite of claim 1, wherein, The carboxyl-terminated hyperbranched polycaprolactone is prepared by adding the hyperbranched polycaprolactone and the dianhydride to a solvent, mixing, raising the temperature to 85-95℃, stirring to react until the acid value of the system is constant, then stopping the reaction, and then precipitating and drying to obtain the carboxyl-terminated hyperbranched polycaprolactone.

4. The degradable PLA composite of claim 1, wherein, The mass ratio of the potassium titanate whisker to the sodium lignosulfonate is 1:(0.02-0.06).

5. The degradable PLA composite of claim 1, wherein, The potassium titanate whisker is modified by dissolving sodium lignosulfonate in deionized water, adding potassium titanate whisker and an acidic catalyst, stirring and dispersing, and then immersing for 8-12 hours, followed by centrifugation, washing, drying and grinding to obtain the modified potassium titanate whisker.

6. A method of producing the degradable PLA composite according to any one of claims 1 to 5, characterized by, The process includes the following steps: S1. Dry the polylactic acid at 60-80℃ for 6-8 hours; S2. Take the dried polylactic acid, carboxyl-terminated hyperbranched polycaprolactone, potassium titanate whisker, compatibilizer, antioxidant and anti-hydrolysis agent according to the corresponding mass fractions, and stir and mix for 10-30 minutes to obtain a mixture; S3. Melt plasticize the mixture, extrude and granulate to obtain the degradable PLA composite material.

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