PCL-PLA composite material, preparation method and application thereof

Abstract

The application relates to the technical field of high polymer materials, in particular to a PCL-PLA composite material and a preparation method and application thereof, the PCL-PLA composite material comprises, in terms of weight parts, polycaprolactone 40-55 parts, polylactic acid 20-35 parts, modified thermoplastic polyurethane 5-15 parts and bio-based chain extender containing a disulfide bond 0.5-2 parts; the modified thermoplastic polyurethane is prepared by a prepolymer method, and raw materials for preparing the prepolymer include 50-70 wt% polycaprolactone glycol, 15-30 wt% L-lactic acid oligomer and 15-25 wt% bio-based diisocyanate. The PCL-PLA composite material has good shape memory capability, self-repairing performance and degradability.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a PCL-PLA composite material, its preparation method, and its application. Background Technology

[0002] Composites of polycaprolactone (PCL) and thermoplastic polyurethane (TPU) have shown potential in the fields of medical rehabilitation fixation and flexible functional devices due to their good biocompatibility, biodegradability and inherent shape memory properties.

[0003] Existing polycaprolactone-thermoplastic polyurethane composites (PCL-TPU composites) are typically prepared using physical blending methods. Compatibilizers such as maleic anhydride grafts are added to improve the compatibility between the two phases, or nanofillers (such as n-HA) are introduced to improve mechanical properties. Essentially, they are still physical blending systems. The physical and mechanical properties of the composites are limited by the uniformity of the mixture. To achieve thorough mixing, existing technologies generally employ high-shear, high-speed co-rotating twin-screw extrusion processes (screw speed is usually >300 rpm). However, this process can impair the self-healing properties of the composites. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a PCL-PLA composite material and its preparation method. By introducing polylactic acid and a bio-based chain extender containing disulfide bonds into the PCL-TPU composite material and modifying the TPU, and further by limiting the amount of each component, the prepared PCL-PLA composite material has good shape memory ability, self-healing performance and degradability.

[0005] The technical solution of the present invention is achieved in the following ways: A PCL-PLA composite material, by weight, comprises: 40-55 parts of polycaprolactone, 20-35 parts of polylactic acid, 5-15 parts of modified thermoplastic polyurethane, and 0.5-2 parts of a bio-based chain extender containing disulfide bonds; wherein the modified thermoplastic polyurethane is prepared by a prepolymer method, and the raw materials for preparing the prepolymer include 50-70 wt% polycaprolactone diol, 15-30 wt% L-lactic acid oligomer, and 15-25 wt% bio-based diisocyanate.

[0006] Through extensive practical experience, the inventors discovered that the poor self-healing performance of existing PCL-TPU composite materials is fundamentally due to the following reasons: In the extruder, the physical entanglement and hydrogen bond network strength of TPU as the stationary phase is insufficient, making it unable to effectively lock and guide the recovery process; while PCL as the driving phase is extremely sensitive to heat and shear, and its molecular chains are prone to β-elimination reactions and hydrolytic chain breaks under high temperatures (>180℃) or strong shear fields, resulting in damage to molecular weight and crystal integrity, a significant decrease in molecular weight (Mw) and intrinsic viscosity (IV), which in turn leads to a severe decrease in the intrinsic recovery driving force of PCL molecular chains, impairing the self-healing performance of the material; ultimately, the prepared PCL-TPU composite material has low shape recovery rate, weak recovery force, and unstable precision.

[0007] The PCL-PLA composite material of the present invention is modified by introducing polylactic acid and a bio-based chain extender containing disulfide bonds into the PCL-TPU composite material and modifying TPU. Furthermore, by limiting the amount of each component, the prepared PCL-PLA composite material has good shape memory ability, self-healing performance and degradability.

[0008] The modified thermoplastic polyurethane (modified TPU) of this invention incorporates 50-70 wt% polycaprolactone diol segments and 15-30 wt% L-lactic acid oligomer segments. In the extruder, the polycaprolactone diol segments in the modified TPU co-crystallize with polycaprolactone, and the L-lactic acid oligomer segments in the modified TPU co-crystallize with polylactic acid, forming strong hydrogen bonds. This rigid co-crystallization method ensures a more uniform and compact mixing between the TPU backbone and the PCL and PLA molecular chains. Furthermore, the active isocyanate groups (-N=C=O) at the ends of the modified TPU can also... The modified TPU reacts with the terminal hydroxyl groups (-OH) in the PCL molecular chain, the carboxyl groups (-COOH) generated from the hydrolysis of the PLA molecular chain, and the urethane groups (-NH-CO-NH-COO-) on the TPU backbone to form covalent bonds for "anchoring." In addition, the urethane groups (-NH-COO-) in the modified TPU can also form hydrogen bonds with the ester groups in PCL, further enhancing the connection between TPU and PCL. Under the combined effect of co-crystallization, covalent bond "anchoring," and hydrogen bonding, the modified TPU forms a strong bond with PCL and PLA that cannot be achieved by physical compatibilizers.

[0009] Based on this, the thiol group (-SH) in the bio-based chain extender containing disulfide bonds added in this invention reacts with the isocyanate group (-NCO) in TPU and other isocyanate groups (-NCO) that may exist in the system, introducing dynamic disulfide bonds (-SS-) as side chains or network nodes into the system. Utilizing the characteristic that dynamic disulfide bonds can undergo reversible homolytic exchange reactions under thermal or mechanical stimulation, the composite material compensates for mechanical stimulation by the breaking of disulfide bonds. After the mechanical stimulation disappears, new disulfide bonds can be recombined through re-contact of the composite material, accelerating the material's self-repair at new contact interfaces, realizing the construction of a reversible cross-linked network, and endowing the material with stronger self-healing ability. Furthermore, the dynamic disulfide bond (-SS-) can also synergistically interact with the hydrogen bonds formed by the modified TPU and PCL, enhancing interfacial compatibility.

[0010] Furthermore, the number-average molecular weight of the L-lactic acid oligomer is 1000-5000 g / mol; and the number-average molecular weight of the polycaprolactone diol is 10000-50000 g / mol.

[0011] Furthermore, the polycaprolactone has a melting point of 58~64℃, a glass transition temperature of -60~-50℃, and a weight-average molecular weight of 20000-200000g / mol.

[0012] Furthermore, the number-average molecular weight of the modified thermoplastic polyurethane is 50,000-200,000 g / mol.

[0013] Furthermore, the polylactic acid has a molecular weight of 10,000-15,000 g / mol, and its melt index is measured to be 30-65 g / 10 min at 210 °C and 2.16 kg.

[0014] Furthermore, the bio-based chain extender containing disulfide bonds includes one or more of bis(2-hydroxyethyl) disulfide and bis(3-hydroxypropyl) disulfide.

[0015] Furthermore, the bio-based diisocyanate includes one or more of lysine diisocyanate, lysine diisocyanate derivatives, 1,5-pentanediisocyanate, 1,5-pentanediisocyanate derivatives, castor oil-based diisocyanate, and castor oil-based diisocyanate derivatives.

[0016] Furthermore, by weight, it also includes one or more of the following: 0-20 parts filler, 0-0.5 parts antioxidant, 0-0.8 parts antibacterial agent, 0-1 parts light stabilizer, and 0-1 parts anti-hydrolysis agent.

[0017] The present invention also provides a method for preparing the PCL-PLA composite material according to any of the above-mentioned methods, comprising the following steps: weighing each raw material according to the proportion, mixing the other raw materials except the polylactic acid evenly, adding them into the extruder from the main feed port of the twin-screw extruder, adding the polylactic acid into the extruder from the side feed port of the intermediate temperature zone of the twin-screw extruder, and then melting and extruding the mixture into granules to obtain the PCL-PLA composite material.

[0018] The present invention also provides an application of any of the above-described PCL-PLA composite materials for preparing high-strength medical rehabilitation fixation materials.

[0019] To better understand and implement this invention, the invention will be described in detail below. Detailed Implementation

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0021] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0022] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] It should be understood that the embodiments of this application are not limited to the precise structures already described above, and various modifications and changes can be made without departing from their scope. The scope of the embodiments of this application is limited only by the appended claims.

[0025] The physical properties and testing methods of the embodiments or comparative examples of the present invention are as follows: Shape memory behavior characterization: Quantitatively assess the shape memory capability of composite materials; a strip-shaped sample film (5mm×40mm×0.6mm) was deformed into a U-shape in a water bath at 46℃ or 60℃, held for 5 min, and then fixed in an ice-water bath for 5 min. The angle between the two arms of the strip was measured and recorded as θ1; subsequently, the sample film was restored to its shape in a water bath at 20℃, 46℃, or 60℃, and the angle between the two arms of the strip was measured again and recorded as θ2; the shape fixation rate (Rf) and shape recovery rate (Rr) were calculated using the following formulas: Rf=(180°-θ1)÷180°×100%; Rr=(θ2-θ1)÷(180°-θ1)×100%.

[0026] Characterization of self-healing behavior: The material was injection molded into a dumbbell-shaped template of ISO 527-2 standard 1A; the template was completely cut with a sharp blade, and the cut surfaces were tightly joined together and left to stand for 72 hours in an environment of 25℃ and 50% relative humidity; subsequently, the repair was tested according to ISO 527-1 standard: Self-healing efficiency = tensile strength (or elongation at break) of the repaired specimen ÷ tensile strength (or elongation at break) of the original undamaged specimen × 100%.

[0027] Characterization of weight loss rate under controlled environment degradation: The material sample was placed in a simulated composting environment with constant temperature of 58℃ and constant humidity, inoculated with microorganisms and kept for 12 weeks; then the sample was taken out, thoroughly cleaned and dried, and its remaining dry weight was measured; by comparing the change in initial dry weight with the dry weight after degradation, the weight loss rate of the material can be calculated. Weight loss rate of compostable waste (%) = (initial dry weight - dry weight after degradation) ÷ initial dry weight × 100%; The higher the weight loss rate, the faster the material degrades under natural composting conditions. If the material maintains a certain strength and a moderate weight loss rate (e.g., 35%-50%) during the test period, it indicates that it is stable during use and degradable after disposal, achieving environmental friendliness throughout its entire life cycle.

[0028] It should be noted that the types of modified TPU used in the embodiments and comparative examples of this invention and their preparation methods are as follows: TPU-1: 50wt% polycaprolactone diol (number average molecular weight of 30000 g / mol), 30wt% L-lactic acid oligomer (number average molecular weight of 2000 g / mol), and 20wt% lysine diisocyanate (number average molecular weight of 226.23 g / mol) were placed in a reactor and reacted at 60-90℃ under inert gas protection to generate a prepolymer. Then, chain extender HDO and catalyst stannous octoate T-9 were added to the reactor, and chain growth reaction was carried out at 70-100℃ until the -NCO reaction was complete. After degassing and molding, TPU-1 was obtained. The number average molecular weight of TPU-1 was measured to be 58000 g / mol by GPC. TPU-2: 60wt% polycaprolactone diol (number average molecular weight 30000 g / mol), 25wt% L-lactic acid oligomer (number average molecular weight 2000 g / mol), and 15wt% lysine diisocyanate (number average molecular weight 226.23 g / mol) were placed in a reactor and reacted at 60-90℃ under inert gas protection to generate a prepolymer. Then, chain extender HDO and catalyst stannous octoate T-9 were added to the reactor, and chain growth reaction was carried out at 70-100℃ until the -NCO reaction was complete. After degassing and molding, TPU-2 was obtained. The number average molecular weight of TPU-2 was measured to be 126000 g / mol by GPC. TPU-3: 70wt% polycaprolactone diol (number average molecular weight of 30000 g / mol), 15wt% L-lactic acid oligomer (number average molecular weight of 2000 g / mol), and 15wt% lysine diisocyanate (number average molecular weight of 226.23 g / mol) were placed in a reactor and reacted at 60-90℃ under inert gas protection to generate a prepolymer. Then, chain extender HDO and catalyst stannous octoate T-9 were added to the reactor, and chain growth reaction was carried out at 70-100℃ until the -NCO reaction was complete. After degassing and molding, TPU-3 was obtained. The number average molecular weight of TPU-3 was measured to be 185000 g / mol by GPC. TPU-4: 25wt% polytetrahydrofuran diol, 20wt% polypropylene carbonate polyol, 39wt% diisocyanate, 15wt% 1,4-butanediol and 1wt% antioxidant 1010 are placed in a reactor and reacted at 60-90℃ under inert gas protection to generate a prepolymer. Then, chain extender HDO and catalyst stannous octoate T-9 are added to the reactor, and chain growth reaction is carried out at 70-100℃ until the -NCO reaction is complete. After degassing and molding, TPU-4 is obtained. The number average molecular weight of TPU-4 is 82000 g / mol as measured by GPC.

[0029] It should be noted that the PCL used in the embodiments and comparative examples of this invention includes: PCL-1: Hunan Juren PCL-6500, molecular weight Mw is 50000 g / mol, melting point is 58-62℃, glass transition temperature is -60℃; PCL-2: Hunan Juren PCL-6800, with a molecular weight (Mw) of 80,000 g / mol, a melting point of 58-62℃, and a glass transition temperature of -60℃.

[0030] It should be noted that the PLA used in the embodiments and comparative examples of this invention includes: PLA-1: Zhejiang Hisun Biotechnology REVODE110, with a molecular weight of 10000 g / mol, and a melt index of 65 g / 10 min measured at 210℃ and 2.16 kg. PLA-2: Anhui Fengyuan Biotechnology FY201, with a molecular weight of 11000 g / mol, and a melt index of 30 g / 10 min measured at 210℃ and 2.16 kg.

[0031] The filler used in this embodiment of the invention is nano-hydroxyapatite (Maclean Twin Biotechnology, H811001, molecular weight Mw is 502.31 g / mol).

[0032] The antioxidant used in the embodiments and comparative examples of this invention is DSTDP antioxidant (Jiangsu Linluda Polymer, molecular weight Mw is 683.16 g / mol).

[0033] The antibacterial agent used in this embodiment of the invention is THOP (Zhongshan Dixin Chemical Co., Ltd., molecular weight Mw is 566.52g / mol).

[0034] The light stabilizer used in the embodiments of the present invention is Tinuvins 292 (BASF, molecular weight 508 g / mol).

[0035] As an optional implementation, 0-1 parts of an anti-hydrolysis agent can be added, and the anti-hydrolysis agent can be carbodiimide.

[0036] The bio-based chain extender containing disulfide bonds used in the embodiments and comparative examples of this invention is bis(2-hydroxyethyl) disulfide (Yuanfeng Chemical, molecular weight 154.24 g / mol).

[0037] The extruder used in the embodiments and comparative examples of this invention is the SHJ35 co-rotating twin-screw extruder from Nanjing Hongjiayuan Machinery Technology Co., Ltd.

[0038] Example 1 This embodiment provides a PCL-PLA composite material, which, by weight, includes 40 parts PCL-2, 35 parts PLA-2, 10 parts TPU-1, 0.5 parts bis(2-hydroxyethyl) disulfide, 15 parts nano hydroxyapatite, and 0.5 parts antibacterial agent.

[0039] The preparation method of PCL-PLA composite material includes the following steps: after uniformly mixing other raw materials except polylactic acid, the mixture is added into the extruder through the main feed port of the twin-screw extruder; polylactic acid is added into the extruder through the side feed port of the intermediate temperature zone of the twin-screw extruder; and the mixture is melt-extruded and granulated by the twin-screw extruder to obtain PCL-PLA composite material; the temperature from the feeding section to the die head is set sequentially to 80-90℃, 120-140℃, 150-170℃, 160-180℃, and 180-190℃.

[0040] Example 2 This embodiment provides a PCL-PLA composite material, which, by weight, includes 48 parts PCL-1, 25 parts PLA-1, 15 parts TPU-1, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0041] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0042] Example 3 This embodiment provides a PCL-PLA composite material, which, by weight, comprises 55 parts PCL-2, 20 parts PLA-2, 5 parts TPU-1, 2 parts bis(2-hydroxyethyl) disulfide and 0.8 parts light stabilizer.

[0043] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0044] Example 4 This embodiment provides a PCL-PLA composite material, which, by weight, comprises 48 parts PCL-1, 25 parts PLA-1, 15 parts TPU-2, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0045] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0046] Example 5 This embodiment provides a PCL-PLA composite material, which, by weight, comprises 48 parts PCL-1, 25 parts PLA-1, 15 parts TPU-3, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant. The preparation method of the PCL-PLA composite material is the same as that in Example 1, and therefore will not be described in detail.

[0047] Comparative Example 1 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 48 parts PCL-1, 25 parts PLA-1, 15 parts TPU-4, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0048] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0049] Comparative Example 2 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 58 parts PCL-1, 30 parts PLA-1, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0050] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0051] Comparative Example 3 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 53 parts PCL-1, 15 parts PLA-1, 20 parts TPU-1, 1 part bis(2-hydroxyethyl) disulfide and 0.2 parts antioxidant.

[0052] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0053] Comparative Example 4 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 35 parts PCL-1, 38 parts PLA-1, 15 parts TPU-1, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0054] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0055] Comparative Example 5 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 58 parts PCL-1, 15 parts PLA-1, 15 parts TPU-1, 1 part bis(2-hydroxyethyl) disulfide, and 0.2 parts antioxidant.

[0056] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0057] Comparative Example 6 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 73 parts PCL-1, 15 parts TPU-1, 1 part bis(2-hydroxyethyl) disulfide and 0.2 parts antioxidant.

[0058] The preparation method of PCL-PLA composite material differs from that of Example 1 in that this example does not include polylactic acid, and therefore does not include the step of feeding polylactic acid into the extruder from the side feed port. The remaining steps are the same as those in Example 1, so they will not be described in detail.

[0059] Comparative Example 7 This comparative example provides a PCL-PLA composite material, which, by weight, comprises 48 parts PCL-1, 25 parts PLA-1, 15 parts TPU-1, and 0.2 parts antioxidant.

[0060] The preparation method of PCL-PLA composite material is the same as that in Example 1, so it will not be described again.

[0061] The performance test results of the PCL-PLA composite materials of Examples 1-5 and Comparative Examples 1-7 are shown in Table 1 below.

[0062] Table 1

[0063] The performance test data above show that the PCL-PLA composite material of the present invention has an Rf value > 96%, an Rr value > 95%, a self-healing efficiency > 80%, and a degradation rate > 35%; it is suitable for preparing high-strength medical rehabilitation fixation materials.

[0064] Comparative Example 1 did not use the modified TPU specified in this invention, and the prepared PCL-PLA composite material had poor self-healing performance.

[0065] As can be seen from Comparative Examples 2-6, the PCL-PLA composite material of the present invention requires a specific content of PCL / PLA / modified TPU to be compounded in order to achieve good self-healing performance at the same time.

[0066] Comparative Example 7, without the addition of a bio-based chain extender containing disulfide bonds, produced a PCL-PLA composite material with poor self-healing properties.

[0067] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A PCL-PLA composite material, characterized in that, By weight, it comprises: 40-55 parts of polycaprolactone, 20-35 parts of polylactic acid, 5-15 parts of modified thermoplastic polyurethane, and 0.5-2 parts of a bio-based chain extender containing disulfide bonds; the modified thermoplastic polyurethane is prepared by a prepolymer method, and the raw materials for preparing the prepolymer include 50-70 wt% polycaprolactone diol, 15-30 wt% L-lactic acid oligomer, and 15-25 wt% bio-based diisocyanate.

2. The PCL-PLA composite material according to claim 1, characterized in that, The number-average molecular weight of the L-lactic acid oligomer is 1000-5000 g / mol; the number-average molecular weight of the polycaprolactone diol is 10000-50000 g / mol.

3. The PCL-PLA composite material according to claim 1, characterized in that, The polycaprolactone has a melting point of 58~64℃, a glass transition temperature of -60~-50℃, and a weight-average molecular weight of 20000-200000g / mol.

4. The PCL-PLA composite material according to claim 1, characterized in that, The number average molecular weight of the modified thermoplastic polyurethane is 50,000-200,000 g / mol.

5. The PCL-PLA composite material according to claim 1, characterized in that, The polylactic acid has a molecular weight of 10,000-15,000 g / mol, and its melt index was measured to be 30-65 g / 10 min at 210 °C and 2.16 kg.

6. The PCL-PLA composite material according to claim 1, characterized in that, The bio-based chain extender containing disulfide bonds includes one or more of bis(2-hydroxyethyl) disulfide and bis(3-hydroxypropyl) disulfide.

7. The PCL-PLA composite material according to claim 1, characterized in that, The bio-based diisocyanate includes one or more of lysine diisocyanate, lysine diisocyanate derivatives, 1,5-pentanediisocyanate, 1,5-pentanediisocyanate derivatives, castor oil-based diisocyanate, and castor oil-based diisocyanate derivatives.

8. The PCL-PLA composite material according to claim 1, characterized in that, By weight, it also includes one or more of the following: 0-20 parts filler, 0-0.5 parts antioxidant, 0-0.8 parts antibacterial agent, 0-1 parts light stabilizer, and 0-1 parts anti-hydrolysis agent.

9. A method for preparing the PCL-PLA composite material as described in any one of claims 1 to 8, characterized in that, Includes the following steps: After weighing each raw material according to the formula, the raw materials other than polylactic acid are mixed evenly and added into the extruder through the main feed port of the twin-screw extruder. The polylactic acid is added into the extruder through the side feed port of the twin-screw extruder. The PCL-PLA composite material is obtained by melt extrusion granulation through the twin-screw extruder.

10. An application of the PCL-PLA composite material as described in any one of claims 1 to 8, characterized in that, Used to prepare high-strength medical rehabilitation fixation materials.

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