CN114228086B

CN114228086B - Method for preparing high-performance PLA/PBSA miniature product based on miniature injection molding process

Info

Publication number: CN114228086B
Application number: CN202111530245.1A
Authority: CN
Inventors: 陈英红; 谢页平; 张力凡
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2022-11-22
Anticipated expiration: 2041-12-14
Also published as: CN114228086A

Abstract

The invention provides a method for preparing a high-performance PLA/PBSA miniature product based on a miniature injection molding process, which is characterized in that the proportion of the PLA/PBSA is improved to adapt to the miniature injection molding process, so that the PBSA forms a fibrous structure in the product, the compatibility and the interface bonding property between the PBSA and the PLA are improved, and the ideal mechanical property of the miniature product is endowed; in addition, the micro injection molding processing technology is combined with the annealing process step, and unexpected remarkable progress is made on properties such as elongation at break and the like of the prepared PLA/PBSA micro product.

Description

Method for preparing high-performance PLA/PBSA miniature product based on miniature injection molding process

Technical Field

The invention belongs to the technical field of injection molding processing of biomedical polymer materials, and relates to a method for preparing a high-performance PLA/PBSA miniature product based on a miniature injection molding process, in particular to a method for preparing a PLA/PBSA miniature bone nail capable of being implanted into a human body.

Background

With the progress of medical technology, the application of micro medical devices in the human body is gradually becoming widespread. Surgical accessories with high precision such as medical bone screws, vascular stents, and the like have been indispensable. The devices are implanted into the human body, so that the requirements on biocompatibility, toughness and the like of the devices are high, the materials widely used at present are mainly based on titanium alloy, but the materials are expensive and often difficult to bear by consumers, and in addition, the devices have postoperative problems, such as titanium alloy bone plates and bone nails applied to treating fracture, and the devices need to be taken out after a patient recovers, so that secondary injury is undoubtedly caused to the patient. Therefore, the development of biodegradable biomedical in vivo-fixing materials is very important. Polylactic acid (PLA) is a biodegradable biomedical material, has high strength modulus and good compatibility with human bodies, has been applied to some medical fields, but has the characteristic of brittleness, and limits the wide application of the PLA in some advanced medical fields. The toughening modification research of polylactic acid is concerned by more and more scientific researchers, and generally, the method for improving the toughness of PLA mainly comprises the steps of adding a small-molecule plasticizer, copolymerization modification and physical blending, but intermediates related to the methods are difficult to degrade in a human body, and some intermediates are even harmful to the human body. In addition, such medical devices are typically completed by solution casting, solvent residue, product deformation during demolding, and extremely low production efficiency, all of which greatly limit the use of PLA for implantation into body devices.

In order to solve the above problems, the current research is mainly directed to improving the shortages of brittleness and the like of polylactic acid by a technical means of blending, crosslinking or copolymerizing the polylactic acid. For example, US20070129784 describes stents made of shape memory polymers, where the material includes a crosslinked polymer. However, the mechanical properties of such stents are very poor, such as the elastic modulus of only 0.5-50MPa, and the requirement of making vascular stents cannot be met at all. In recent years, the Changchun Shengbo Ma biomaterial company develops and develops a medical biodegradable composite material which has independent intellectual property and is blended by hydroxyapatite grafted and modified by oligolactic acid and polylactic acid, the medical biodegradable new material solves the problems of poor toughness, easy brittle fracture and the like of pure polylactic acid, and has more advantages when being used on bone nails and bone plates for bearing large bones and frontal bones. However, the preparation process of the hydroxyapatite related to the technology is relatively complex, and the cost is high due to the fact that the PLA molecular chain is grafted with the hydroxyapatite. Therefore, in view of the factors of cost, complex preparation process and the like, the prior art has good effects, but is generally difficult to popularize and apply, and the metal materials in the medical field still occupy the leading position at present.

The Poly Butylene Succinate Adipate (PBSA) has good biodegradation performance, and simultaneously, a large number of methyl structures in a main chain enable the Poly Butylene Succinate Adipate (PBSA) to have mechanical properties similar to those of a general Polyethylene (PE) material, so that the Poly Butylene Succinate Adipate (PBSA) is suitable for various processing technologies such as blow molding films and hollow containers, extrusion processing sheets, spinning, injection molding and the like, and is a material with good processing performance in the conventional degradable plastics. However, the PBSA has low relative molecular mass, low processing temperature and low viscosity, and the mechanical properties of the obtained material cannot be compared with those of PE, so that blending modification is required. The PLA/PBSA blend prepared by melt blending PLA and PBSA is a common preparation process, and on the other hand, the PLA/PBSA tensile sample obtained by the traditional injection molding process has the defects of low mechanical properties such as elongation at break and the like, so that the high-performance micro medical device is difficult to prepare by the traditional injection molding.

With the progress of the technology and the optimization of the production process, the application range of the micro injection molding technology is continuously expanded. Compared with traditional injection molding, micro injection molding processing is usually performed under extreme conditions, such as significantly reduced micro cavity and runner dimensions, high shear rate, high temperature gradient, high injection pressure, high injection rate, and the like, which creates conditions for forming highly oriented structures in the micro injection molding process of polymer materials and realizing high performance of micro products and devices. Therefore, it is expected that the polymer and its composite material under the micro-processing condition have different structure and performance from the traditional processing (Jiang Zhi, chen Yinggong, liu Zhuo, crystal morphology and filling behavior of polyoxymethylene/nylon 11/carbon nanotube composite material under the micro-injection molding processing condition, polymer material science and engineering, 2014, 30 (9)).

Therefore, if a micro injection molding processing technology can be used for preparing the PLA-based micro medical device, the processing technology is simple, the cost is low, and the prepared PLA-based micro medical device has excellent performance, thereby being greatly beneficial to the use and popularization of the PLA-based micro medical device.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a method for preparing a high-performance PLA/PBSA miniature product based on a miniature injection molding process, which is characterized in that the proportion of the PLA/PBSA is improved to adapt to the miniature injection molding process, so that the PBSA forms a fibrous structure in the product, the compatibility and the interface bonding property between the PBSA and the PLA are improved, and the ideal mechanical property is endowed to the miniature product; in addition, the micro injection molding processing technology is combined with the annealing process step, and unexpected remarkable progress is made on properties such as elongation at break and the like of the prepared PLA/PBSA micro product.

In order to achieve the purpose, the invention adopts the technical scheme formed by the following technical measures.

A method for preparing a high-performance PLA/PBSA miniature product based on a miniature injection molding process comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80 to 90 portions of polylactic acid (PLA),

10-20 parts of polybutylene succinate adipate (PBSA);

wherein the total amount of the polylactic acid and the polybutylene succinate-co-adipate is 100 parts;

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 180-200 ℃ at 100-200 r/min, stably drawing extruded strands by using a tractor, and cooling and pelletizing to obtain PLA/PBSA granules;

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a mold cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 50-600 mm/s, the mold temperature is 20-60 ℃, the melt temperature is 180-200 ℃, the pressure maintaining and cooling time is 5-15 s, and the stretching speed of the blend passing through the gate in the micro-injection molding machine is controlled to be 50000-70000 s ^-1 ；

(4) Annealing

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 80-120 ℃, and the annealing time is 20-60 min.

Through the process conditions, in the finally prepared PLA/PBSA micro injection molding product, the PBSA forms a fibrous structure in the product, the compatibility and the interface bonding property between the PBSA and the PLA are improved, the product is endowed with the silver streak resistance, and a hybrid cross-crystal structure exists in a shear layer of the product, so that the ductility of the product can be greatly improved while the mechanical strength of the material is kept unchanged. In addition, through the annealing process step, the breaking elongation of the product is further greatly improved.

Generally, the polylactic acid in step (1) may be selected from L-or D-polylactic acid according to the actual product use and functionality, and those skilled in the art may select polylactic acid with an appropriate molecular weight as required, and for the convenience of describing the present invention, 4032D type and 6201D type polylactic acid are generally preferred in terms of biomedical materials.

Generally, the polybutylene succinate adipate in the step (1) can select models with different molecular weights, such as injection molding grades, blow molding grades and the like according to actual requirements to realize different viscosity ratios between the PLA and the PBSA.

It is worth noting that the extrusion in step (2), generally because PLA and PBSA have water absorption, the water content during melt blending in the extruder tends to cause depolymerization of the polymer, so PLA and PBSA need to be dried at 80 and 50 ℃ for 12h, respectively, and those skilled in the art can select an appropriate drying time according to the actual processing amount.

The PLA/PBSA granules are obtained by cutting the granules in the step (2), and the PLA/PBSA granules are usually subjected to micro injection molding for the convenience of subsequent assistance, so the particle size of the PLA/PBSA granules is preferably 0.5-2 mm. In general, the skilled person will be able to select the appropriate particle size of the pellets depending on the micro injection moulding equipment used.

It should be noted that, in the step (2), the extrusion is performed by a twin-screw extruder at a limited condition of 100-200 rpm, because the dispersed phase forms nano-sized spherical particles dispersed in the PLA matrix under the action of the strong shear flow, and more nanofiber bundles can be formed in the later micro-injection molding process, thereby limiting the use of the twin-screw extruder. If the extrusion rotating speed is too low, the sea-island structure blend with the nano-scale dispersed phase is not easy to form; if the extrusion rotation speed is too high, although the nano-scale dispersed phase can be obtained, PLA molecular chains are broken, and serious degradation behaviors occur, so that the mechanical properties are reduced.

The inventor of the invention finds that when the dispersed phase material is polybutylene succinate adipate and the proportion of the polybutylene succinate adipate in the raw materials is different in the actual research and production process, the product performance prepared under the same micro injection molding processing condition has a change rule different from that of the traditional injection molding about PLA/PBSA under the same proportion. In the existing PLA/PBSA traditional melt blending technical literature, in order to enable a PLA/PBSA blending material to have the best elongation at break, the toughness improvement effect of the obtained sample is better when the PBSA addition amount is 30% -40%, and the toughness improvement effect of the sample is not obvious when the PBSA addition amount is less.

Unlike the prior art processes, in order to obtain a product with better properties, preferably the preparation steps are as follows:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

85 to 90 portions of polylactic acid,

10-15 parts of polybutylene succinate adipate;

(2) Preparation of the blend

Adding the prepared polylactic acid and polybutylene succinate adipate obtained in the step (1) into a double-screw extruder, extruding at 180-200 ℃ at 100 revolutions per minute, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules;

(3) Micro injection molding

Respectively injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 50-600 mm/s, the mold temperature is 20-60 ℃, the melt temperature is 180-200 ℃, the pressure maintaining and cooling time is 5-15 s, and the stretching speed of the blend passing through the gate in the micro-injection molding machine is controlled to be 50000-70000 s ^-1 ；

(4) Annealing

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 80-120 ℃, and the annealing time is 60min.

The PLA/PBSA miniature injection molding product prepared by the preferable technical scheme has the advantages that the mechanical tensile strength can reach 61MPa, the Young modulus can reach 2300MPa, and the elongation at break can reach 53%. Compared with the pure PLA miniature injection molding product, the tensile strength of the pure PLA miniature injection molding product is about 66MPa, the Young modulus is 2500MPa, and the breaking elongation is 17%.

The reason why the addition amount of polybutylene succinate adipate (PBSA) is preferably 10 to 15 parts is that the inventor of the invention finds that the addition of PBSA in the micro injection molding process can obviously improve the elongation at break of PLA indeed in the actual production process, and a fibrous structure can be formed under certain process conditions when the addition amount is more than 20 percent. However, as the content of PBSA increases, the strength and modulus of the product decrease remarkably, and in order to improve the elongation at break while maintaining high strength and modulus, the amount of PBSA added is preferably 10 to 20 parts, more preferably 10 to 15 parts. And the finding shows that according to the technical scheme of the invention, even if the material is prepared when the PBSA doping amount is 10%, the material has the mechanical property which is obviously higher than that of the material prepared by the traditional injection molding with the same proportion of PBSA addition amount, and even is much higher than that of the material prepared by the traditional injection molding preparation technology with the preferred proportion of PBSA addition amount. The research of the inventor of the invention preliminarily considers that the PBSA can have better performance at low mixture ratio in the system, and is attributed to that under the condition of a micro injection molding process, the compatibility and the interface bonding property between PLA are improved due to the formed fibrous structure of the PBSA, meanwhile, the fibrous structure can play a role of a rivet to inhibit the transformation from silver lines to cracks, and the final annealing treatment endows the product with better elongation at break.

Further preferably, the processing conditions in step (3) further include an injection speed of 50-600 mm/s, and the inventor of the present invention found that, in the production process, when the injection speed is 200mm/s, 400mm/s, 600mm/s, the difference between the fiber orientation morphology inside the prepared product and the mechanical property thereof is not great, and when the injection speed is preferably 50mm/s, the fiberization structure can be formed inside the sample and the lower the injection speed is, the more the cross-grain structure is formed inside, which is beneficial to the improvement of the mechanical strength.

However, due to the difference of the micro injection molding products, considering that the distribution of the velocity field of the polymer fluid depends on the structural size of the mold, the rheology and the heat conducting property of the polymer material, the specific processing technology and the size of the melt flow provided by the injection molding machine, the stretching rate can not be equivalent to the range corresponding to the injection speed of 50-600 mm/s of the injection molding machine of the inventor under all the process conditions of micro injection molding, so that the research on the stretching rate at which the microfibrillated structure can be formed is particularly important, and theoretical guidance can be provided for product design and process optimization. In view of the above, the present invention has carried out computer simulation of the injection molding process of PLA/PBSA, and the drawing rate of the melt passing through the gate is calculated, and the melt drawing rate is found to exceed 150000s ^-1 When this happens, the fiber structure is severely damaged; the drawing rate is 60000s ^-1 When the fiber is in good form, the drawing rate at the casting gate is finally summarized to be 50000-70000 s ^-1 The prepared product has good fiber form and obviously improved mechanical properties; therefore, those skilled in the art can design the gates and the flow channels by using fluid finite element simulation software, such as a polyflow, and the like to design a product in the early stage according to the data, or optimize the machining process in the actual production process, so that the stretching rate of the flow field is at the optimum or near the optimum, and the workload of process regulation and control is reduced.

Further preferably, the temperature of the die is 25-35 ℃, the PBSA is used as a dispersed phase, and the specific surface area of the PBSA is greatly increased after the PBSA is stretched into fibers by a flow field, and the process is an entropy reduction process. The surface tension causes sinusoidal disturbance to occur, and then fibers are broken, so that the shape of the injection-molded product needs to be configured at a fast cooling rate, according to the traditional mold heat transfer theory, the cooling rate of the injection-molded product in the cooling process is mainly determined by the melt temperature, the mold temperature and the thermal conductivity of the material, and the inventor of the invention finds that the mold temperature has a great influence on the configuration of PBSA (Poly-p-phenylene-SA) fibrosis, particularly on the preparation of micro medical devices with local thickness of about 0.33mm and relatively large area in the vertical thickness direction, such as vascular clamps and the like. When the temperature of the mold is 50 ℃, the formed fibrous structure is easy to break into small liquid drops, but when the temperature of the mold is reduced to 40 ℃, more fibrous structures are formed, a few liquid drops exist, when the temperature of the mold is reduced to 30 ℃, the liquid drops almost disappear, and the surface of the fiber is attached with crystal clusters, which is mainly because the overall cooling rate in the product is extremely high due to the reduction of the temperature of the mold, and the fiber is configured in the future and deformed and broken. When the temperature of the mould is 25-35 ℃, the microfiber structure of the product is easier to be maintained. The technical content is preferably used as a guide for actual production and processing, and in some medical products such as a micro vascular clamp, the bending part is thinner and cools quickly and is a key part of the medical product, and whether the internal form of the medical product, namely a fibrosis structure, can be cooled and configured in time often determines whether the medical product is usable or not.

It is worth to be emphasized that, in the research process, the inventor of the present invention also finds that, in the PLA/PBSA product prepared based on micro injection molding, annealing treatment after micro injection molding can greatly improve the mechanical strength and elongation at break of the product, because after annealing, PLA molecular chains crystallize in the direction perpendicular to the PBSA fiber to form a hybrid crystal string structure. Taking a sample containing 10% of PBSA as an example, the mechanical properties, especially the elongation at break, of the PLA/PBSA articles prepared by micro injection molding after annealing treatment showed a large increase as compared with the pure system, the increase being 211.8%. However, if the annealing time is too short, the PLA platelet content perpendicular to the PBSA fiber is low, and a perfect hybrid cross-crystal structure cannot be formed; if the annealing treatment time is too long, the PLA crystallinity increases greatly, brittleness increases, and elongation at break decreases.

In contrast, in PLA/PBSA articles prepared based on conventional injection molding processes, PBSA is difficult to form into a fibrous structure due to the weak shear effect and slow cooling rate of conventional injection molding, while PLA forms mostly a spherulitic structure and is difficult to form into a fiber string structure. By comparison, the PLA/PBSA products prepared by traditional injection molding have weaker properties in all aspects than the micro injection molding samples with the same PBSA content. After annealing treatment is carried out on PLA/PBSA products prepared by the traditional injection molding process, the mechanical properties of the products are greatly changed, for example, the elongation at break of the PLA/PBSA products is remarkably reduced (all the elongation at break is less than 5%), which is probably caused by that a large amount of spherulites are formed by PLA in the annealing process, meanwhile, the movement capability of PLA molecular chains is increased due to the addition of the PBSA, and the PLA is more likely to form spherulites, so that the elongation at break of all samples containing the PBSA is greatly reduced after annealing. Due to the phenomenon, when the PLA/PBSA product prepared based on the traditional injection molding process needs better flexibility, the annealing treatment can not be carried out.

The invention principle of the invention is as follows:

for PLA/PBSA blend, because of its inherent incompatibility, PBSA as disperse phase is in the form of nanometer globular distribution in the blend, the invention successfully stretches PBSA nanometer liquid drop under the molten state to form fibrous structure with high length-diameter ratio by controlling the size of the disperse phase PBSA and the micro injection molding process, and the huge cooling temperature gradient in the micro mold cavity is favorable for the configuration of the PBSA fibrous structure, and reduces the relaxation of the orientation unit of the molecular chain; in the annealing process, PLA molecular chains grow in an arrangement mode in a direction perpendicular to the PBSA fibers, and finally a hybrid crystal string structure with the PBSA nanofibers as shish and the PLA platelets as Kebab is formed.

Secondly, the introduction of the PBSA phase reduces the viscosity of the system and can promote the disentanglement of PLA molecular chains, so that the system presents a special viscosity reduction effect and is beneficial to reducing the filling resistance; and the fiberization structure can induce PLA molecular chains to form initial crystal nucleuses on the fiberization structure, and the initial crystal nucleuses grow into flaky crystals in later annealing, so that a hybrid crystal string structure is formed, and the improvement of mechanical properties is facilitated. Therefore, compared with a PLA/PBSA blended product prepared by a traditional injection molding processing technology, the product prepared by the preparation technology has a fibrous structure, the ductility is obviously improved while the mechanical strength is not sacrificed, and the possibility of being used as a micro medical product, especially a biomedical product implanted into a human body such as a bone nail is greatly enhanced.

In addition, it is known in the art that in the conventional injection molding of polymers, the thickness of an injection molded product is relatively uniform, the stretching rate is relatively low, and it is difficult to utilize the structure of the injection molded product to generate in-situ fiber forming effect, so that if the mechanical properties of the product are improved through a fiberization structure, the stretching rate at a runner and a gate in the micro injection molding process is crucial to the formation of the fiberization structure. For example, micro-medical devices such as micro-vascular clamps, micro-bone screws, etc., those skilled in the art can design the dimensions of the flow channel or the gate according to the technical contents of the present invention to construct the stretching flow field to guide the actual production process.

It is worth explaining that the injection pressure and the injection speed of the micro injection molding machine used in the micro injection molding process are different due to different models, product requirements and actual conditions, and the difference caused by different processing environments is avoided by providing the stretching speed of the runner and the sprue in the injection molding process, so that a technician in the field can calculate the specific processing conditions suitable for the current processing environment by the stretching speed, stably obtain the PLA/PBSA blended micro injection molding product with the fibrous structure, do not need to perform pre-production operations such as mold testing and the like, and greatly reduce the production cost.

The invention has the following beneficial effects:

1. according to the invention, the PLA/PBSA blend with the nano-scale dispersed phase is prepared and obtained through the strong shearing force provided by the double-screw extruder at the high rotating speed, the PLA micro-injection product with the PBSA nano-fibers is prepared and obtained through the strong stretching flow field provided by micro-injection and the huge temperature difference, and finally, the crystallinity of the PLA is improved through annealing treatment, and the ductility of the PLA is obviously improved compared with that of the traditional injection molding process without sacrificing the mechanical strength. The method has simple process and low cost, and is widely suitable for manufacturing biomedical micro devices.

2. The invention has the advantages of low cost and wide source of raw materials, safety, no toxicity and good compatibility with human bodies.

3. Various processing conditions of the invention have guiding significance for product development, mold preparation and process optimization, and technicians in the field can stably obtain the micro injection molding product with the fibrous structure according to the content of the invention, thereby reducing preproduction operations such as mold testing and the like and greatly reducing the production cost.

4. The invention verifies that the polymer and the composite material thereof under the micro-processing condition have different structures and performances from the traditional processing, and have great revelation effect on the field of micro-injection molding process.

Drawings

FIG. 1 is an electron microscope image of brittle cross-sections of PLA/PBSA micro injection molded preforms made in example 1 of the present invention. The surface thereof is rough, and the PBSA fibers are dispersed therein in the flow direction.

FIG. 2 is an electron microscope image of brittle cross-sections of PLA/PBSA micro injection molded preforms made in example 2 of the present invention. The surface was rough, PBSA fibers were dispersed therein in the flow direction, and the trace of the fiber being pulled apart was clearly seen.

FIG. 3 is an electron microscope image of the brittle cross-section of a PLA mini injection molded preform prepared in comparative example 1 of the present invention.

FIG. 4 is an electron microscope image of brittle cross-sections of PLA/PBSA micro injection molded preforms made in comparative example 2 of the present invention. The surface was rougher than in example 2, with a large number of PBSA fibers dispersed in it in the flow direction, and the evidence of fiber stretch-breaking was evident.

FIG. 5 is a graph of stress-strain comparison of comparative example 5 (MP 0), comparative example 3 (MP 10), comparative example 4 (MP 20), and comparative example 6 (MP 40) of the present invention. It is evident that as PBSA content increases, the elastic modulus and yield strength decrease and the elongation at break increases.

FIG. 6 is an electron microscope image of a brittle section of a PLA micro injection molded article obtained in comparative example 1 of the present invention after etching. After the amorphous regions were etched, it was seen that the crystalline regions were aligned parallel and perpendicular to the flow direction.

FIG. 7 is an electron microscope image of the etched brittle section of the PLA/PBSA micro injection-molded article obtained in example 1 of the present invention. The PBSA nanofibers are embedded in the PLA matrix in the flow direction.

FIG. 8 is an electron microscope image of the etched brittle section of the PLA/PBSA micro injection molded article obtained in comparative example 2 of the present invention. Due to the increase in the content of PBSA, the PBSA is dispersed in a PLA matrix in a band shape, unlike the fiber structure in example 1.

FIG. 9 is a stress-strain comparison graph of example 1 (AMP 10), example 2 (AMP 20), comparative example 1 (AMP 0), and comparative example 2 (AMP 40), showing that the elastic modulus and yield strength of the composite material after annealing are both significantly increased, the elongation at break of the pure PLA sample after annealing is slightly increased for the elongation at break, the elongation at break of the sample containing 10% PBSA is significantly increased (> 50%), the elongation at break of the sample containing 20% PBSA is also slightly increased, and the elongation at break of the sample containing 40% PBSA is decreased, probably because the addition of PBSA increases the molecular chain mobility of PLA, and the PLA forms a large number of spherulites during annealing, thus decreasing the elongation at break.

Fig. 10 is a stress-strain comparison graph of comparative example 7 (CP 10), comparative example 9 (CP 20), comparative example 11 (CP 0), and comparative example 13 (CP 40).

Fig. 11 is a stress-strain comparison graph of comparative example 8 (ACP 10), comparative example 10 (ACP 20), comparative example 12 (ACP 0), and comparative example 14 (ACP 40).

FIG. 12 is a photograph of a micro-injection molded sample of the present invention after stretching and during a tensile test

FIG. 13 is a photograph of a conventional injection-molded sample after stretching and at the time of the stretching test in a comparative example of the present invention

Detailed Description

The invention is further illustrated by the following examples in connection with the accompanying drawings. It should be noted that the examples given are not to be construed as limiting the scope of the invention, and that those skilled in the art, on the basis of the teachings of the present invention, will be able to make numerous insubstantial modifications and adaptations of the invention without departing from its scope.

To better reflect the generality of the experimental data, the average of the test performance of 5-8 samples in each example and comparative example is taken as the representative of the example. It is noted that the tensile properties and the electron micrographs of the samples obtained in the following examples and comparative examples were measured by the following apparatus and by the prior art.

Tensile property: the dumbbell-shaped sample has a middle length of 9mm, a width of 2mm, a thickness of 0.33mm and a stretching speed of 10mm/min.

SEM: the micro tensile sample is frozen for 30min by liquid nitrogen, then quenched along the flowing direction, and then is etched in a sodium hydroxide aqueous solution (water: methanol =1, 2, v/v) containing 0.025mol/L for 12h at the etching temperature of 30 ℃, the etched sample is cleaned by ultrasonic oscillation, then is dried in vacuum and sprayed with gold, and the test is carried out by adopting an INSPECTF scanning electron microscope of Japan at the voltage of 5 KV.

Injection molding micro-machines (model MicroPower 5, battenfeld, austria), PLA (Mn = 100000), PBSA (injection grade, mn = 120000).

Example 1

The embodiment of the invention relates to a method for preparing a high-performance PLA/PBSA miniature medical product based on a miniature injection molding process, which comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

90 parts of polylactic acid (PLA),

10 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly (butylene succinate-co-adipate) in the step (1), adding the mixture into a double-screw extruder, extruding at 190 ℃ at 100 r/min, stably drawing and extruding strands by using a drawing machine, and cooling and granulating to obtain PLA/PBSA granules (0.5 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 200mm/s, the mold temperature is 30 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

(4) Annealing of

Annealing the PLA/PBSA miniature injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA miniature injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 60min.

Tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 61.2 +/-3.0 MPa, the Young modulus of 2318.5 +/-24.8 MPa and the elongation at break of 51.2 +/-4.5 percent.

Example 2

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80 parts of polylactic acid (PLA),

20 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 190 ℃ at 100 revolutions per minute, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules (0.5 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a mold cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 200mm/s, the mold temperature is 30 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

(4) Annealing of

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 60min.

Tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 52.2 +/-2.6 MPa, the Young modulus of 2088.9 +/-106.4 MPa and the elongation at break of 42.3 +/-3.6 percent.

Comparative example 1

The method for preparing the PLA miniature medical product based on the miniature injection molding process comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

100 parts of polylactic acid (PLA);

(2) Preparation of the blend

Adding the prepared polylactic acid obtained in the step (1) into a double-screw extruder, extruding at 190 ℃ at 100 r/min, stably drawing extruded strands by a drawing machine, and cooling and dicing to obtain PLA granules (0.5 mm);

(3) Micro injection molding

Injecting the PLA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 200mm/s, the mold temperature is 30 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

(4) Annealing

Annealing the PLA miniature injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA miniature injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 60min.

Tests show that the prepared PLA miniature injection molding product has the tensile strength of 67.1 +/-2.1 MPa, the Young modulus of 2498 +/-137.3 MPa and the breaking elongation of 16.2 +/-2.3 percent.

Comparative example 2

The method for preparing the PLA/PBSA miniature medical product based on the miniature injection molding process in the comparative example comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

60 parts of polylactic acid (PLA),

40 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Micro injection molding

(4) Annealing

Tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 39.0 +/-2.4 MPa, the Young modulus of 1576.8 +/-106.6 MPa and the breaking elongation of 32.7 +/-3.5 percent.

Comparative example 3

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

90 parts of polylactic acid (PLA),

10 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding product by a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 200mm/s, the mold temperature is 30 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 57.7 +/-1.2 MPa, the Young modulus of 1912 +/-56.3 MPa and the elongation at break of 23.1 +/-2.7 percent.

Comparative example 4

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80 parts of polylactic acid (PLA),

20 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Micro injection molding

tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 51.1 +/-1.9 MPa, the Young modulus of 1693 +/-79.7 MPa and the elongation at break of 27 +/-2.5 percent.

Comparative example 5

The method for preparing the PLA miniature medical product based on the miniature injection molding process in the comparative example comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

100 parts of polylactic acid (PLA),

(2) Preparation of the blend

Adding the prepared polylactic acid in the step (1) into a double-screw extruder, extruding at 190 ℃ at 100 r/min, stably drawing and extruding a strand by using a drawing machine, and cooling and granulating to obtain PLA granules (0.5 mm);

(3) Micro injection molding

Injecting the PLA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA micro injection molding product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 200mm/s, the mold temperature is 30 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

tests show that the prepared PLA miniature injection molding product has the tensile strength of 62.4 +/-2.6 MPa, the Young modulus of 1984 +/-101.4 MPa and the elongation at break of 10 +/-1.5 percent.

Comparative example 6

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

60 parts of polylactic acid (PLA),

40 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Micro injection molding

tests show that the prepared PLA/PBSA miniature injection molding product has the tensile strength of 37.6 +/-2.0 MPa, the Young modulus of 1308.2 +/-93.4 MPa and the elongation at break of 42 +/-3.1 percent.

Comparative example 7

The method for preparing the PLA/PBSA miniature medical product based on the traditional injection molding process in the comparative example comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

90 parts of polylactic acid (PLA),

10 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Traditional injection moulding

Injecting the PLA/PBSA granules prepared in the step (2) into a mold cavity in a traditional injection molding machine, and preparing a PLA/PBSA injection molding product by a traditional injection molding process; wherein, the process conditions of the traditional injection molding process are as follows: the injection speed is 20mm/s, the mold temperature is 50 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

tests show that the prepared PLA/PBSA injection molding product has the tensile strength of 53.3 +/-0.8 MPa, the Young modulus of 1811.5 +/-11 MPa and the elongation at break of 8.6 +/-1.8 percent.

Comparative example 8

In the comparative example, annealing treatment is performed on the basis of the comparative example 7, the rest process conditions are unchanged, and the annealing treatment is specifically as follows:

annealing the PLA/PBSA injection molding product prepared in the step (3); wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 60min.

Tests show that the tensile strength of the PLA/PBSA injection molding product after annealing treatment is 53.2 +/-3.1 MPa, the Young modulus is 2146.9 +/-164 MPa, and the elongation at break is 2.4 +/-0.4 percent.

Comparative example 9

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80 parts of polylactic acid (PLA),

20 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Traditional injection moulding

tests show that the prepared PLA/PBSA injection molding product has the tensile strength of 46.7 +/-3.7 MPa, the Young modulus of 1546.2 +/-65 MPa and the elongation at break of 26.1 +/-5.3 percent.

Comparative example 10

In the comparative example, annealing treatment is performed on the basis of the comparative example 9, the rest process conditions are unchanged, and the annealing treatment is specifically as follows:

Tests show that the tensile strength of the PLA/PBSA injection molding product after annealing treatment is 50.3 +/-1.8 MPa, the Young modulus is 1924.6 +/-50 MPa, and the breaking elongation is 3.4 +/-0.8%.

Comparative example 11

The method for preparing the PLA/PBSA miniature medical product based on the traditional injection molding process comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

100 parts of polylactic acid (PLA);

(2) Preparation of the blend

(3) Traditional injection moulding

Injecting the PLA granules prepared in the step (2) into a mold cavity in a traditional injection molding machine, and preparing a PLA injection molding product by a traditional injection molding process; wherein, the process conditions of the traditional injection molding process are as follows: the injection speed is 20mm/s, the mold temperature is 50 ℃, the melt temperature is 190 ℃, and the pressure maintaining and cooling time is 10s;

tests show that the prepared PLA injection molding product has the tensile strength of 58.4 +/-2 MPa, the Young modulus of 1956.1 +/-144 MPa and the elongation at break of 3.7 +/-0.9 percent.

Comparative example 12

In the comparative example, annealing treatment is performed on the basis of the comparative example 11, the rest process conditions are unchanged, and the annealing treatment specifically comprises the following steps:

annealing the PLA injection molding product prepared in the step (3); wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 60min.

Tests show that the tensile strength of the PLA injection molding product after annealing treatment is 41.5 +/-2.1 MPa, the Young modulus is 2592.4 +/-25 MPa, and the elongation at break is 1.3 +/-0.08 percent.

Comparative example 13

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

60 parts of polylactic acid (PLA),

40 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

(3) Traditional injection moulding

tests show that the prepared PLA/PBSA injection molding product has the tensile strength of 37.9 +/-1.2 MPa, the Young modulus of 1216 +/-32 MPa and the elongation at break of 30.1 +/-4 percent.

Comparative example 14

In the comparative example, annealing treatment is performed on the basis of the comparative example 13, the rest process conditions are not changed, and the annealing treatment specifically comprises the following steps:

Tests show that the tensile strength of the PLA/PBSA injection molding product after annealing treatment is 39.7 +/-3.4 MPa, the Young modulus is 1457 +/-250 MPa, and the elongation at break is 2.6 +/-0.5%.

Example 3

The method for preparing the high-performance PLA/PBSA miniature medical product based on the miniature injection molding process comprises the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

90 parts of polylactic acid (PLA),

10 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 180 ℃ at 180 r/min, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules (1 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 100mm/s, the mold temperature is 40 ℃, the melt temperature is 180 ℃, and the pressure maintaining and cooling time is 12s;

(4) Annealing

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 90 ℃, and the annealing time is 40min.

Example 4

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

90 parts of polylactic acid (PLA),

10 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 200 ℃ at 120 r/min, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules (1 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a mold cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 400mm/s, the mold temperature is 50 ℃, the melt temperature is 200 ℃, and the pressure maintaining and cooling time is 6s;

(4) Annealing of

Annealing the PLA/PBSA miniature injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA miniature injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 120 ℃, and the annealing time is 30min.

Example 5

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

85 parts of polylactic acid (PLA),

15 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 180 ℃ at 200 revolutions per minute, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules (1 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a mold cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 550mm/s, the mold temperature is 40 ℃, the melt temperature is 180 ℃, and the pressure maintaining and cooling time is 15s;

(4) Annealing

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 100 ℃, and the annealing time is 50min.

Example 6

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80 parts of polylactic acid (PLA),

20 parts of polybutylene succinate adipate (PBSA);

(2) Preparation of the blend

Mixing the prepared polylactic acid and poly succinic acid butanediol adipate in the step (1), adding the mixture into a double-screw extruder, extruding at 200 ℃ at 100 revolutions per minute, stably drawing extruded strands by using a drawing machine, and cooling and pelletizing to obtain PLA/PBSA granules (1 mm);

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and preparing a PLA/PBSA micro injection molding prefabricated product through a micro injection molding process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 300mm/s, the mold temperature is 60 ℃, the melt temperature is 180 ℃, and the pressure maintaining and cooling time is 8s;

(4) Annealing

Annealing the PLA/PBSA micro injection molding prefabricated product prepared in the step (3) to obtain a PLA/PBSA micro injection molding product; wherein the process conditions of the annealing treatment are as follows: the temperature is 80 ℃, and the annealing time is 60min.

Claims

1. A method for preparing a high-performance PLA/PBSA miniature product based on a miniature injection molding process is characterized by comprising the following preparation steps:

(1) Stock preparation

The raw materials mainly comprise the following components in parts by weight:

80-90 parts of polylactic acid,

10-20 parts of polybutylene succinate adipate;

(2) Preparation of the blend

(3) Micro injection molding

Injecting the PLA/PBSA granules prepared in the step (2) into a die cavity of a required product in a micro injection molding machine, and micro injectingPreparing a PLA/PBSA micro injection molding prefabricated product by a plastic process; wherein, the process conditions of the micro injection molding process are as follows: the injection speed is 50-600 mm/s, the mould temperature is 20-60 ℃, the melt temperature is 180-200 ℃, the pressure maintaining and cooling time is 5-15 s, and the stretching speed of the blend passing through the gate in the micro injection molding machine is controlled to be 50000-70000 s ^-1 ；

(4) Annealing of

2. The method of claim 1, further comprising: in the step (1), the polybutylene succinate adipate accounts for 10-15 parts.

3. The method of claim 1, further comprising: in the step (3), the temperature of the die is 25-35 ℃.

4. A PLA/PBSA micro-article prepared by the method for preparing a high performance PLA/PBSA micro-article based on a micro injection molding process according to any one of claims 1 to 3.