CN111534068A - A kind of ultra-high impact strength polylactic acid material and preparation method thereof - Google Patents

Abstract

The invention provides an ultra-high impact strength polylactic acid material and a preparation method thereof. The ultra-high impact strength polylactic acid material provided by the present invention uses elastomer or plastic as a toughening agent, and is uniformly blended to form a parison and then stretched above its glass transition temperature, thereby significantly improving the polylactic acid/elasticity. impact resistance of polylactic acid/plastic blends. The experimental results show that the tensile strength of the polylactic acid blend material is increased from 60MPa to 171MPa, the elongation at break is increased from 6% to 17‑124%, and the notched impact strength is increased from 2KJ/m ² to 272KJ/ m ² , the mechanical properties enhancement and impact toughening effect are very significant. The stretching treatment can also increase the crystallinity of the polylactic acid blend material, thereby greatly improving the heat resistance of the material.

Description

A kind of ultra-high impact strength polylactic acid material and preparation method thereof

technical field

The invention belongs to the technical field of polymer materials, and more particularly relates to a preparation method of a polylactic acid material with ultra-high impact strength.

Background technique

In recent years, with the increasingly serious problems of resource shortage and environmental pollution, the development and application of sustainable utilization of resources, especially environmentally friendly and biodegradable materials, has attracted widespread attention. At the same time, due to the rapid development of materials science, existing materials can no longer meet the needs of human beings. Therefore, research and development of materials with high performance, degradability and excellent comprehensive properties and expansion of their application fields are the main trends of current development.

Polylactic acid is an environmentally friendly biomass-derived plastic with excellent biocompatibility, biodegradability and processability. focus on. However, polylactic acid still has problems such as brittleness, low toughness, and poor heat resistance, and the notched impact strength value is lower than 4KJ/m ² , which seriously limits the wide application of polylactic acid materials in various fields. Therefore, the research on the modification of polylactic acid materials has become a hot spot, especially various toughening modifications.

Chinese patent CN1701082 discloses the technical scheme of blending polyoxymethylene and polylactic acid, and adding impact modifier to improve the impact resistance of the blend. This solution improved the impact resistance of the mixture, with a notched impact strength value of 128.2 J/m.

Chinese patent CN107033563 discloses that a reinforced and toughened polylactic acid material is obtained by melt blending of polyurethane modification and polylactic acid, and its notched impact strength value is 15KJ/m ² .

Chinese patent CN110305457 discloses that silicone rubber microspheres and polylactic acid particles are melt-blended to prepare transparent and toughened polylactic acid materials. The transparency is basically the same as that of pure polylactic acid, and the unnotched impact strength value is 115KJ/m ² .

Chinese patent CN110305435 discloses a transparent toughened polylactic acid/acrylic alloy material prepared by melt blending of crystalline polylactic acid, polymethyl methacrylate, transparent toughening agent and compatibilizer, and its notched impact strength value is 38KJ/m ² .

Chinese patent CN107022181 discloses melt blending of natural rubber and polylactic acid, in an attempt to make natural rubber toughen polylactic acid more effectively without losing the rigidity and strength of polylactic acid, but its notched impact strength is only 6KJ/m ² .

Chinese patent CN105602214 discloses that polylactic acid is blended with low molecular weight and high molecular weight polyethylene glycol ester at the same time to achieve both plasticizing and toughening effects on polylactic acid. Its elongation at break and notched impact strength are respectively is 271% and 68KJ/m ² .

SUMMARY OF THE INVENTION

One object of the present invention is to provide a polylactic acid material with ultra-high impact strength and a preparation method thereof, so as to overcome the inherent brittleness defect of polylactic acid pointed out in the introduction of the background art. The preparation method of the ultra-high impact strength polylactic acid material includes: drying the polylactic acid pellets and the toughening agent respectively, then adding the toughening agent under the polylactic acid melting condition for blending, and obtaining the type by hot pressing or injection molding. Then, the parison is stretched above its glass transition temperature, and after reaching a certain strain, it is cooled and solidified below its glass transition temperature, thereby obtaining a polylactic acid material with ultra-high impact strength.

Preferably, the toughening agent is an elastomer or plastic.

Preferably, the toughening agent comprises ethylene-methyl acrylate-glycidyl methacrylate random copolymer, hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer and elastomers such as natural rubber Or polycaprolactone plastic, etc.

Preferably, the mass ratio of the toughening agent blended with the polylactic acid is 1:(1-99), preferably 1:(80-99), more preferably 1:(80-95).

Preferably, the melt blending conditions are that the blending temperature is 160-250° C., and the blending time is 3-30 min.

Preferably, the temperature of the stretching treatment is between the glass transition temperature of the polylactic acid blend and 90°C, more preferably 60-85°C, still more preferably 65-80°C.

Preferably, the stretching rate of the stretching treatment is 1-50 mm/min, preferably 10-50 mm/min, more preferably 20-50 mm/min.

Preferably, the stretching processing strain of the stretching treatment is 100-700%, preferably 200-700%, more preferably 300-500%.

Another object of the present invention is to provide an ultra-high impact strength polylactic acid material, which contains 80-99% by mass of polylactic acid and 1-20% by mass of a toughening agent, and has a maximum breaking strength of 171 MPa, 17- 124% elongation at break, notched impact strength up to ^272KJ /m2. Furthermore, the ultra-high impact strength polylactic acid material of the present invention has a minimum breaking strength of 61 MPa or more, and a minimum notched impact strength of 115 KJ/m ² or more.

Description of drawings

Figure 1: Stress-strain curve diagram of the stretching process of Example 6;

Fig. 2: the sample physical map of embodiment 4;

Fig. 3: the sample physical map of embodiment 1;

Figure 4: Izod notched impact strength diagrams of Examples 1-6 and Comparative Example 1;

Figure 5: Stress-strain curves of secondary stretching of Examples 1-6 and Comparative Example 3;

Figure 6: Change diagram of the elongation at break of the secondary stretching of Examples 1-6 and Comparative Example 3;

Fig. 7: The breaking strength change diagram of the secondary stretching of Examples 1-6 and Comparative Example 3;

Fig. 8: Tensile toughness change graph of the secondary stretching of Examples 1-6 and Comparative Example 3;

Fig. 9: the scanning electron microscope picture of embodiment 4;

Figure 10: Scanning electron microscope image of Example 6;

FIG. 11 : Wide-angle X-ray diffraction patterns of Example 4 and Comparative Example 1. FIG.

FIG. 12 : Small angle X-ray scattering plots of Example 4 and Comparative Example 1. FIG.

FIG. 13 : Ultra-small angle X-ray scattering plots of Example 4 and Comparative Example 1. FIG.

Figure 14: Stress-strain graph of the stretching process of Example 12;

Figure 15: The sample physical map of Example 10;

Figure 16: Izod notched impact strength graph of Examples 7-11 and Comparative Example 2;

Figure 17: Stress-strain plots for secondary stretching of Examples 7-12 and Comparative Example 3;

Figure 18: Change diagram of the elongation at break of the secondary stretching of Examples 7-12 and Comparative Example 3;

Fig. 19: Variation diagram of the breaking strength of the secondary stretching of Examples 7-12 and Comparative Example 3;

Figure 20: Storage modulus-temperature curve graph in the dynamic mechanical analysis test of Example 10;

Figure 21: Storage modulus-temperature change curve graph in the dynamic mechanical analysis test of Comparative Example 2;

FIG. 22 : Graph of storage modulus versus temperature in the dynamic mechanical analysis test of Comparative Example 3. FIG.

Figure 23: The sample physical map of Example 15;

Figure 24: The sample physical map of Example 16;

Figure 25: the sample physical map of Example 17;

Figure 26: The sample physical map of Example 18;

Figure 27: The sample physical map of Example 19;

Figure 28: The sample physical map of Example 20;

FIG. 29 : The physical image of the sample of Example 21. FIG.

Detailed ways

definition

The "polylactic acid pellets" described in this application include crystalline polylactic acid and non-crystalline polylactic acid. In the present application, the particle size, molecular weight and molecular weight distribution of polylactic acid are not particularly limited.

The size of the "parison" described in this application is not particularly limited, and is usually pressed into a "parison" of different sizes according to the mold in the compression molding machine, for example, it can be 0.5-16mm thick, 10-80mm wide, and 50-150mm long . Depending on the size of the parison, the stretched materials can include films, sheets, and bulk materials.

The "toughening agent" described in this application is not particularly limited, and elastomers or plastics are preferably used, examples of which include ethylene-methyl acrylate-glycidyl methacrylate random copolymer, hydrogenated polystyrene-polybutadiene Ethylene-polystyrene triblock copolymers and elastomers such as natural rubber or polycaprolactone plastics, etc., and more specific examples thereof are ethylene-methyl acrylate-glycidyl methacrylate random copolymer toughening agents .

In the process of the present application, polylactic acid and a toughening agent (eg, ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) or other elastomers or plastics are combined. Both the lactic acid and the toughening agent were dried separately) to prepare a base material or profile by melt blending, and then stretching the blend base material or profile above its glass transition temperature will make the elastomer Alternatively, both the plastic particles and the PLA matrix form a strongly oriented microstructure, which significantly increases the stiffness and toughness of the material. The tensile strength of the polylactic acid material treated in this way is increased from 60MPa to 171MPa, the elongation at break is increased from 6% to 17-124%, and the notched impact strength is increased from 2KJ/m ² to 272KJ/m ² . Strengthening and toughening effects are very significant.

In the preparation method of the present invention, the "drying" treatment of the polylactic acid and the toughening agent refers to the general technical meaning in the field of chemical materials, that is, in order to reduce the water content. For example, the water content is usually controlled below 100×10 ^-6 .

In the production method of the present invention, the equipment suitable for melt blending is not particularly limited, for example, a torque rheometer can be used.

In the preparation method of the present invention, the cooling process used is not particularly limited, and generally the material can be cooled to room temperature. In addition, the process of testing the tensile properties of the ultra-high impact strength polylactic acid material of the present invention also includes cooling and solidification after stretching the parison. This cooling solidification is also not particularly limited in the present invention, that is, conventional cooling solidification in the art can be used.

In a specific embodiment of the present invention, the preparation method of the above-mentioned ultra-high impact strength polylactic acid material provided by the present invention is:

(1) drying of raw materials, the drying temperature is 20-90°C, and the drying time is 1-72h. Specifically, amorphous polylactic acid needs to be dried at a lower temperature (23-45°C); crystalline polylactic acid can be dried at 65-90°C, or can be dried using a dehumidifying dryer dedicated to polylactic acid. The raw material is dried because it is considered that excessive moisture will increase the thermal degradation of polylactic acid in steps (2) and (3), and affect the material properties.

(2) 80 to 99 parts by mass of dried polylactic acid and 1 to 20 parts by mass of toughening agent are added to a high-speed mixer to mix uniformly, and then added to a twin-screw extruder at 160-250 ° C for melt extrusion and granulation; also Melt mixing can be performed using an internal mixer or the like.

(3) Add the obtained pellets into an injection molding machine at 160-250°C to prepare molded products, wherein the mold temperature is set to room temperature or 100-140°C, and the corresponding molding cycle is 20-40s or 90-120s; a compression mold can also be used Molded products are prepared by machine, the molding temperature is 160-250°C, the pressure is 2-12MPa, and the time is 1-300min.

(4) On the stretching equipment with temperature control, the parison is stretched, and the stretching temperature is above the glass transition temperature of the parison and lower than the melting temperature. Preferably, the stretching temperature is 60-90°C, more preferably 60-85°C, still more preferably 65-80°C. The rate is 1-50mm/min, after reaching the customized strain (100-700%), it is cooled and solidified at room temperature or below, thereby obtaining a polylactic acid material with ultra-high impact strength.

In the present invention, the elastomer or plastic is added to the polylactic acid matrix, and under the action of the shear field and temperature field, the elastomer or plastic as a toughening agent can be dispersed in the matrix at micron or submicron scale. , which can achieve very limited partial toughening and modification purposes. However, since the strength and modulus of the elastomer or plastic itself are much lower than those of PLA, the rigidity and strength of PLA will be reduced after the introduction of the PLA matrix. The introduction of elastomers will also further reduce the heat resistance of PLA, limiting its application. In the present invention, the post-processing operation of the blend is carried out by using the stretching technology, so that the elastomer or plastic particles and the polylactic acid matrix are highly oriented, and the microstructure with a high degree of orientation is maintained, thereby not only improving the rigidity of the material. and strength, but also endows the material with ultra-high impact strength.

The technical points of the present invention are as follows: firstly, melt blending the polylactic acid pellets and the toughening agent; secondly, obtain the parison through a molding process such as hot pressing or injection molding; stretch treatment. Compared with the conventional techniques in the art, there is no precedent for preparing ultra-high impact-strength polylactic acid materials by stretching techniques above the glass transition temperature. The three-step processing method created by the present invention is obtained through countless experiments and continuous adjustment. The impact resistance of the polylactic acid material obtained through this technical solution is currently the best, and the notched impact strength can be from the 2KJ of the polylactic acid matrix. The increase of /m ² is as high as 272KJ/m ² , and the post-stretching operation steps are simple and the effect is very obvious.

In a particular embodiment of the present invention, a method for preparing a polylactic acid material with ultra-high impact strength is provided, which is characterized in that: banburying the dried polylactic acid and elastomer or plastic according to a specific ratio, such as , carry out banburying in a torque rheometer, banburying temperature 160-250 ℃, rotating speed 20-200rpm, banburying time 3-30min, the obtained blend is molded in a compression molding machine into different sizes (thickness 0.5 -16mm, width 10-80mm, length 50-150mm), the molding temperature is 160-250 ℃, the pressure is 2-12MPa, the time is 1-300min, and the parison is drawn on the stretching equipment with temperature control. Stretching treatment, the stretching temperature is 60-90°C, preferably 60-85°C, more preferably 65-80°C, the rate is 1-50mm/min, after reaching a custom strain of 100-700%, cooling and solidification below the glass transition temperature of polylactic acid , and then obtain the ultra-high impact strength polylactic acid material.

The ultra-high-impact-strength polylactic acid material obtained by the above preparation method of the ultra-high-impact-strength polylactic acid material can be used to manufacture packaging materials, fibers and nonwovens, etc., and is mainly used in clothing (underwear, outerwear), industry (construction , agriculture, forestry, paper, automobile manufacturing) and health and medical equipment and other fields.

Beneficial effects of the present invention:

(1) The elastomer or plastic is uniformly dispersed in the polylactic acid by melt blending in the polylactic acid body, and then stretching treatment is performed above the glass transition temperature of the blend to make the elastomer or plastic particles and the polylactic acid matrix All of them are highly oriented, forming an oriented microstructure distribution, which not only significantly improves the rigidity and strength of the material, but also significantly improves the impact strength of the material. The tensile strength of the PLA material was increased from 60 MPa to 171 MPa, the elongation at break was increased from 6% to 17-124%, and the notched impact strength was increased from 2KJ/m ² to 272KJ/m ² . And the toughening effect is very significant.

(2) Part of the limited toughening modification can be realized during the melt processing of the polylactic acid matrix, the operation process is simple and easy, and the toughening effect does not have to be particularly significant, but the patent proposed to carry out stretching above its glass transition temperature The stretching process will bring about a huge improvement in impact strength, because a highly oriented microstructure is generated in the system, and stretching also produces oriented polylactic acid crystals. While the material is reinforced and toughened, it also It endows the material with more excellent heat resistance performance, which can significantly increase the heat resistance temperature of the material.

Example

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications or improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

The polylactic acid used in the following examples was purchased from Natureworks, the brand is 2003D, and the toughening agents used are all commercially available products, such as ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA ) were purchased from Arkema, France, under the trade name LOTADER@AX8900.

Example 1

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 6 × 15 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Co. The temperature of the stretching chamber is 70 °C, the stretching rate is 20 mm/min, and the strain is 100%. After reaching the predetermined strain, it is cooled and solidified in an air environment at room temperature to obtain a polylactic acid blend sample with a strain of 100%. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

FIG. 3 shows that the thus obtained polylactic acid material after stretching treatment at 70° C. is translucent.

Example 2

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 18 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 200%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated samples were cut out to prepare a 3×80×10mm rectangular impact bar with a notch and a 1×4×50mm dumbbell-shaped tensile bar, which were then subjected to impact and tensile tests respectively.

Example 3

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 6 × 22 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 4

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 9 × 20 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 400%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

FIG. 2 shows the process of cooling and solidifying the splines of Example 4 after reaching a predetermined strain in an air environment at room temperature.

Figure 9 shows that in the splines of Example 4 it can be clearly seen that the polylactic acid blend is aligned along the stretching direction, resulting in an oriented structure.

Figure 11 shows that the two-dimensional wide-angle X-ray diffraction pattern of the unstretched polylactic acid blend (Comparative Example 1) exhibits isotropic dispersed rings, indicating that the unstretched polylactic acid blend is amorphous and does not have Orientation of the structure. After stretching at 70 °C, with the increase of the tensile strain, the 2D wide-angle X-ray diffraction pattern (Example 4) of the polylactic acid blend is parallel to the stretching direction (vertical direction) of the disperse ring intensity It gradually becomes stronger, while the intensity of the dispersion ring perpendicular to the stretching direction gradually weakens, and the isotropic dispersion ring transforms into a pair of broad diffraction arcs parallel to the stretching direction, and diffraction spots appear inside the broad diffraction arc, indicating that During the stretching process, the molecular chains are gradually oriented along the stretching direction, and the degree of orientation is gradually increased.

Figure 12 shows that the two-dimensional small angle X-ray scattering pattern of the unstretched PLA blend (Comparative Example 1) appears isotropic, indicating that the unstretched PLA blend is non-oriented on the nanoscale. After stretching at 70 °C, the two-dimensional small-angle X-ray scattering diagram (Example 4) shows that with the increase of the tensile strain, the molecular chains are gradually oriented along the stretching direction during the stretching process, and a high degree of height appears in the polylactic acid material. Oriented fibrous microstructure.

Figure 13 shows that the two-dimensional ultra-small angle X-ray scattering pattern of the unstretched PLA blend (Comparative Example 1) appears isotropic, indicating that the unstretched PLA blend is not oriented on a sub-micron scale of. After stretching at 70°C, the two-dimensional ultra-small-angle X-ray scattering diagram (Example 4) shows that with the increase of the tensile strain, the molecular chains are gradually oriented along the stretching direction during the stretching process, and the appearance of the polylactic acid material appears in the polylactic acid material. Highly oriented fibrous submicron structure with possible partial cavitation.

Example 5

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-6MA) (number average molecular weight 130k) after drying at 60°C for 12h was 95/5 by mass ratio at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 30 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 500%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 6

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-6MA) (number average molecular weight 130k) after drying at 60°C for 12h was 95/5 by mass ratio at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 30 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 700%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Figure 1 shows the stress-strain curve of the Example 6 sample during the tensile process. According to the different stress responses during stretching, the stress-strain curve can be divided into three different regions: elastic deformation region (I), strain softening region (II) and strain hardening region (III). Before the yield point (strain is 100%, Example 1) is the elastic deformation zone (I), the sample exhibits Hooke's elastic behavior, remove the stress, the strain can be recovered without leaving permanent deformation; after the yield point is the plastic deformation zone, the sample It exhibits plastic behavior; if the stress is removed, the strain cannot recover, leaving permanent deformation. In the plastic deformation region, when the strain is in the range of 100%-200%, the stress decreases or remains unchanged with the increase of the strain, which is called the strain softening region (II); when the strain is greater than 200% (implementation Example 2), the stress increases sharply with the increase of strain, which is called the strain hardening zone (III). When the temperature of the stretching chamber is 70°C, the originally frozen chain segments in the polylactic acid blend material begin to move, and the extension of the polymer chain provides the deformation of the material. When the sample is stretched to the set strain at 70°C, and then cooled to room temperature, the stretched polymer chains are frozen again, and the deformation cannot be recovered spontaneously even if the external force is removed. Therefore, according to the stress-strain curve, different tensile strains were selected in the above three different regions, and the tensile splines under the corresponding strains were obtained, and the mechanical properties were tested and the microstructure was characterized.

Figure 4 shows that the polylactic acid blend material is obviously brittle at room temperature when it is not stretched, and the notched impact strength is only 2.6KJ/m ² . When the polylactic acid blend material was stretched to 100% at 70°C (Example 1), the cohesive and entangled network was just reorganized, the degree of orientation was low, and the notched impact strength did not change significantly. When stretched to 200% (Example 2), with the further increase of the degree of orientation, the notched impact strength of the sample increased sharply, from 12KJ/m ² (Example 1) to 204KJ/m ² . The value is nearly 17 times that of 12KJ/m ² and 78 times that of 2.6KJ/m ² . With the further increase of the tensile strain, the notched impact strength of the polylactic acid blend material continues to increase. When the tensile strain is 400% (Example 4), the notched impact strength has a maximum value of 272KJ/m ² , and the toughening effect is very good. Obviously, it is 105 times the notched impact strength value of the unstretched polylactic acid blend material, which is 2.6KJ/m ² . After the notched impact strength of the polylactic acid blend reaches the maximum value, with the further increase of the tensile strain, the oriented fibrous structure inside the sample may be tensile ruptured, resulting in a decrease in the notched impact strength.

Figure 5 shows that the tensile behavior of the PLA blends obtained by the tensile treatment also changed significantly, from brittle fracture to ductile fracture at room temperature, showing typical yielding, necking and strain hardening phenomena. In addition, with the increase of tensile strain, the thin neck region of the splines in room temperature secondary stretching gradually became smaller; when the tensile strain increased to 700% (Example 6), the thin neck phenomenon almost disappeared.

Figure 6 shows that the elongation at break of the polylactic acid blend obtained by stretching treatment at room temperature decreases gradually with the increase of tensile strain. When the tensile strain of the polylactic acid blend material is 100% (Example 1), the polylactic acid blend material has the maximum elongation at break (101%); when the tensile strain of the polylactic acid blend material is the largest (implementation Example 6), the elongation at break was the smallest (17%), but still greater than the elongation at break (6%) of the unstretched unblended PLA splines.

Figure 7 shows that the breaking strength of the polylactic acid blend obtained by stretching treatment increases gradually with the increase of tensile strain at room temperature after secondary stretching. When the tensile strain of the polylactic acid blend material is 100% (Example 1), the breaking strength of the polylactic acid blend material does not increase significantly compared with the unstretched and unblended polylactic acid material. With the further increase of the tensile strain, the breaking strength of the polylactic acid blend material in the secondary stretching at room temperature gradually increases. When the tensile strength reaches 700% of the maximum strain (Example 6), the breaking strength shows the maximum value, which is 171MPa.

Figure 8 shows that the tensile toughness of the polylactic acid blend obtained by stretching treatment decreases gradually with the increase of tensile strain in the secondary stretching at room temperature. When the tensile strain of the polylactic acid blend material is 100% (Example 1), the polylactic acid blend material has the maximum tensile toughness (46KJ/m ³ ); when the tensile strain of the polylactic acid blend material is the largest ( Example 6), the tensile toughness is the smallest (20KJ/m ³ ), but it is still greater than the tensile toughness (1.8 KJ/m ³ ) of the unstretched and unblended PLA splines.

Figure 10 shows that after the polylactic acid blend material is stretched (Example 6), the microstructure ordering along the stretching direction clearly appears, resulting in an oriented microstructure.

Example 7

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 6 × 15 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 100%. Cool and solidify in the air environment to obtain ultra-high impact strength polylactic acid. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 8

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 18 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 200%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 9

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 6 × 22 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 10

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blend was molded into parisons of 9 × 20 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 400%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Figure 20 shows the storage modulus-temperature curve diagram of the dynamic mechanical analysis test of Example 10. It can be seen that its storage modulus is 214MPa at 106°C, which is much higher than the same temperature condition The storage modulus values of Comparative Example 2 (103 °C, 2.4 MPa) and Comparative Example 3 (103 °C, 3.3 MPa) below show that the tensile treatment significantly improves the heat resistance of the material. Figure 20 shows the spline The heat-resistant temperature can be raised to 142 ℃.

Example 11

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 30 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 500%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Example 12

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The resulting blends were molded into parisons of 6 × 30 × 100 mm (for making impact bars) and 3 × 30 × 100 mm (for making secondary stretch bars) in a compression molding machine at a molding temperature of 200°C, pressure 10MPa, time 10min, and the sample was cooled to room temperature by ice-water quenching. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 700%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Figure 14 shows the stress-strain curve of the Example 12 sample during the stretching process. According to the different stress responses during stretching, the stress-strain curve can be divided into three different regions: elastic deformation region (I), strain softening region (II) and strain hardening region (III). Before the yield point (strain is 100%, Example 7) is the elastic deformation zone (I), the sample exhibits Hooke elastic behavior, and the strain can be recovered after removing the stress, leaving no permanent deformation; after the yield point is the plastic deformation zone, the sample It exhibits plastic behavior; if the stress is removed, the strain cannot recover, leaving permanent deformation. In the plastic deformation region, when the strain is in the range of 100%-200%, the stress decreases or remains unchanged with the increase of the strain, which is called the strain softening region (II); when the strain is greater than 200% (implementation Example 8), the stress increases sharply with the increase of strain, which is called the strain hardening zone (III). When stretched at 70°C, the originally frozen segments of the polylactic acid blend material began to move, and the extension of the polymer chain provided the deformation of the material. When the sample is stretched to the set strain at 70°C, and then cooled to room temperature, the stretched polymer chains are frozen again, and the deformation cannot be recovered spontaneously even if the external force is removed. Therefore, according to the stress-strain curve, different tensile strains were selected in the above three different regions, and the tensile splines under the corresponding strains were obtained, and their mechanical properties were tested and their microstructures were characterized.

FIG. 15 shows that the polylactic acid blend material obtained after the stretching treatment in Example 10 is milky white.

Figure 16 shows that when the polylactic acid blend material is not stretched, it is brittle at room temperature, and the notched impact strength is only 21KJ/m ² . When the polylactic acid blend material was stretched to 100% at 70°C (Example 7), the cohesive and entangled network was reorganized, the sample was oriented, and the notched impact strength was greatly increased to 115KJ/m ² . With the further increase of the tensile strain, the degree of orientation of the polylactic acid blend material increases, and the notched impact strength increases continuously. When the tensile strain is 400% (Example 10), the notched impact strength has a maximum value of 165KJ/m ² , the toughening effect is very obvious. After the notched impact strength of the polylactic acid blend reaches the maximum value, with the further increase of the tensile strain, the oriented fibrous microstructure inside the sample is stretched and fractured, and the notched impact strength decreases.

Figure 17 shows that the tensile behavior of the PLA blends obtained by stretching at 70 °C also changed significantly, from brittle fracture to ductile fracture at room temperature, showing typical yielding, necking and strain hardening phenomena . In addition, with the increase of tensile strain, the thin neck region of the splines after secondary stretching at room temperature gradually became smaller; when the tensile strain increased to 700% (Example 12), the thin neck phenomenon almost disappeared.

FIG. 18 shows that the elongation at break of the polylactic acid blend material obtained by stretching at 70° C. at room temperature decreases gradually with the increase of tensile strain. When the tensile strain of the polylactic acid blend material is 100% (Example 7), the polylactic acid blend material has the maximum elongation at break (124%); when the tensile strain of the polylactic acid blend material is the largest (implementation Example 12), the elongation at break was the smallest (20%), but still greater than the elongation at break (6%) of the unstretched unblended PLA material.

FIG. 19 shows that the breaking strength of the polylactic acid blend obtained by stretching at 70° C. at room temperature gradually increases with the increase of tensile strain. When the tensile strain of the polylactic acid blend material was 100% (Example 7), the breaking strength of the polylactic acid blend material did not increase significantly compared with the unstretched polylactic acid material. With the further increase of the tensile strain, the breaking strength of the polylactic acid blend material in the room temperature secondary stretching gradually increases. When the tensile strength reaches 700% of the maximum strain (Example 12), the breaking strength has a maximum value of 144 MPa.

Example 13

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 9 × 20 × 100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 °C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching. to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 80 °C, the stretching rate was 20 mm/min, and the strain was 400%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 129 KJ/m ² .

Example 14

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a torque of 99/1 in the mass fraction ratio. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 9 × 20 × 100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 °C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching. to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 400%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 203 KJ/m ² .

Example 15

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-6MA) (number average molecular weight 130k) after drying at 60°C for 12h was 95/5 by mass ratio at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 50 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 222 KJ/m ² .

FIG. 23 shows that the thus obtained polylactic acid material after stretching treatment at 70° C. appears translucent.

Example 16

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 1 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 156KJ/m ² .

FIG. 24 shows that the thus obtained polylactic acid material after stretching treatment at 70° C. appears translucent.

Example 17

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 90 °C, the stretching rate was 20 mm/min, and the strain was 300%. It was cooled and solidified in an air environment to obtain a polylactic acid sample with a tensile strain of 300%. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 6KJ/m ² .

FIG. 25 shows that the thus obtained polylactic acid material after stretching treatment at 90° C. appears translucent.

Example 18

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 60 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 229 KJ/m ² .

FIG. 26 shows that the thus obtained polylactic acid material after stretching treatment at 60° C. appears translucent.

Example 19

The polylactic acid and natural rubber after drying at 60°C for 12h were mixed in a torque rheometer at a mass ratio of 95/5. The mixing temperature was 200°C, the rotational speed was 80rpm, and the mixing time was 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 152 KJ/m ² .

FIG. 27 shows that the thus obtained polylactic acid material after stretching treatment at 70° C. has a light milky yellow color.

Example 20

The polylactic acid and hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer (SEBS) after drying at 60℃ for 12h were mixed in a torque rheometer in a mass ratio of 95/5. , Banbury temperature 200 ℃, speed 80rpm, Banbury time 12min. The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 195KJ/m ² .

FIG. 28 shows that the thus obtained polylactic acid material after stretching treatment at 70° C. has a light milky yellow color.

Example 21

The polylactic acid and polycaprolactone (PCL) after drying at 60°C for 12h were mixed in a torque rheometer at a mass ratio of 95/5. The mixing temperature was 200°C, the rotational speed was 80rpm, and the mixing time was 12min. . The obtained blend was molded into a parison of 6×22×100 mm (for the preparation of impact bars) in a compression molding machine, the molding temperature was 200 ° C, the pressure was 10 MPa, and the time was 10 min, and the sample was cooled by ice-water quenching to room temperature. The parison was stretched on the temperature-controlled stretching equipment UTM2502 universal testing machine of Shenzhen Sansi Company. The stretching chamber temperature was 70 °C, the stretching rate was 20 mm/min, and the strain was 300%. Cool and solidify in the air environment to obtain a polylactic acid sample with ultra-high impact strength. The tensile-treated sample was cut out to prepare a 3×80×10 mm rectangular impact bar with a notch, and then the impact test was carried out.

The notched impact strength of the polylactic acid material sample was 181 KJ/m ² .

FIG. 29 shows that the thus obtained polylactic acid material after stretching treatment at 70°C is translucent.

Comparative Example 1

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were prepared at a torque of 95/5. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a polylactic acid sheet in a compression molding machine. The molding temperature was 200° C., the pressure was 10 MPa, and the time was 10 min. The sample was cooled to room temperature by ice-water quenching. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Comparative Example 2

Polylactic acid and ethylene-methyl acrylate-glycidyl methacrylate random copolymer (EMA-GMA) (number-average molecular weight 130k) after drying at 60°C for 12h were subjected to a mass ratio of 80/20 at torque. Banburying was carried out in a rheometer, the banburying temperature was 200°C, the rotating speed was 80rpm, and the banburying time was 12min. The obtained blend was molded into a polylactic acid sheet in a compression molding machine. The molding temperature was 200° C., the pressure was 10 MPa, and the time was 10 min. The sample was cooled to room temperature by ice-water quenching. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Fig. 21 shows the storage modulus-temperature change curve diagram in the dynamic mechanical analysis test of Comparative Example 2, the storage modulus is only 14MPa at 80°C, and the storage modulus is much lower than the embodiment under the same temperature condition 10 (1054MPa), indicating that the sample of Example 10 significantly increases the heat resistance temperature of the material due to the stretching treatment.

Comparative Example 3

The polylactic acid dried at 60 °C for 12 h was molded into a polylactic acid sheet village in a compression molding machine. The molding temperature was 200 °C, the pressure was 10 MPa, and the time was 10 min. The sample was cooled to room temperature by ice-water quenching. The samples after tensile treatment were cut out to prepare 3×80×10mm notched rectangular impact bars and 1×4×50mm dumbbell-shaped tensile bars, which were then subjected to impact and tensile tests respectively.

Figure 22 shows the storage modulus-temperature change curve diagram in the dynamic mechanical analysis test of Comparative Example 3, the storage modulus is 23MPa at 80°C, and the storage modulus is much lower than that of Example 10 under the same temperature condition (1054MPa), indicating that the sample of Example 10 significantly increased the heat resistance temperature of the material due to the stretching treatment.

Combining the above examples and accompanying drawings 1-19, it can be seen that the tensile strength of the polylactic acid blended material above the glass transition temperature of each system is increased from 60MPa to 171MPa, and the elongation at break is increased from 6% to 17%. -124%, the notched impact strength is increased from 2KJ/m ² to 272KJ/m ² , and the obtained strengthening and toughening effects are very significant. The stretching treatment can also increase the crystallinity of the polylactic acid matrix, thereby greatly improving the heat resistance of the material.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. a preparation method of super high impact strength polylactic acid material, described method comprises the following steps: (1) blending the polylactic acid pellets and the toughening agent in the molten state of the polylactic acid; (2) molding the obtained blend to obtain a parison; (3) The parison is stretched above its glass transition temperature, and then cooled and solidified below its glass transition temperature, so as to obtain a polylactic acid material with ultra-high impact strength. 2 . The method for preparing an ultra-high impact strength polylactic acid material according to claim 1 , wherein the toughening agent is an elastomer or a plastic. 3 . 3. The preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein the toughening agent is selected from the group consisting of ethylene-methyl acrylate-glycidyl methacrylate random copolymer, hydrogenated polyphenylene Ethylene-polybutadiene-polystyrene triblock copolymers, natural rubber and polycaprolactone plastics. 4. the preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein, in described step (1): The mass ratio of the toughening agent to the polylactic acid pellets is 1:(1-99). 5. the preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein, in described step (1): The blending temperature is 160-250°C, and the blending time is 3-30 min. 6. the preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein, in described step (3): The temperature of the stretching treatment is between the glass transition temperature of the polylactic acid blend and 90°C. 7. the preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein, in described step (3): During the stretching process, the stretching rate is 1-50 mm/min. 8. the preparation method of ultra-high impact strength polylactic acid material according to claim 1, wherein, in described step (3): During the stretching process, the tensile strain is 100-700%. 9. An ultra-high impact strength polylactic acid material, comprising 80-99% by mass of polylactic acid and 1-20% by mass of a toughening agent, and having a maximum breaking strength of 171 MPa and a breaking elongation of 17-124% rate, the highest notched impact strength of ^272KJ /m2. 10. The ultra-high impact-strength polylactic acid material according to claim 9, which is a biodegradable plastic.

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