CN118834471B

CN118834471B - A rigid-toughness balanced polypropylene composite material and preparation method thereof

Info

Publication number: CN118834471B
Application number: CN202411320559.2A
Authority: CN
Inventors: 李勇进; 王亨缇; 夏衍
Original assignee: Hangzhou Normal University
Current assignee: Hangzhou Normal University
Priority date: 2024-09-23
Filing date: 2024-09-23
Publication date: 2025-01-24
Anticipated expiration: 2044-09-23
Also published as: CN118834471A

Abstract

The invention discloses a rigid-tough balance polypropylene composite material and a preparation method thereof, wherein the method comprises the steps of carrying out melt blending on polyolefin-glycidyl methacrylate copolymer and polylactic acid through a mixing mill to obtain a uniform blend, then cooling to room temperature, adding the blend into polypropylene, and uniformly mixing at the room temperature to obtain a mixture A; or the polyolefin-glycidyl methacrylate copolymer, polylactic acid and polypropylene are directly and uniformly mixed at normal temperature to obtain a mixture B, and one of the mixture A or B is selected and added into mixing equipment to be melt-blended, so that the modified polypropylene composite material is finally obtained. The invention realizes the high performance of the polypropylene material through a specific formula and a specific process, is suitable for various industrial applications, and the preparation method is simple and convenient to operate and is suitable for large-scale production. The composite material shows the characteristic of high-performance polymer alloy and provides excellent material selection for application fields requiring high strength and high toughness.

Description

Rigid-tough balance polypropylene composite material and preparation method thereof

Technical Field

The invention belongs to the technical field of high polymer materials, and relates to a rigid-tough balance polypropylene composite material and a preparation method thereof. The composite material realizes the combination of high strength and high toughness through a specific formula and a specific process, and is suitable for various industrial applications.

Background

Polypropylene (PP) is one of five general plastics, has the advantages of abundant sources, low price, excellent performance, good processing performance and wide application, and is the resin with the most development prospect in the high performance of the general plastics worldwide at present. PP has regular structure, higher mechanical strength than polyethylene, good insulating property, heat resistance, chemical resistance and the like, but has poor low-temperature toughness, large notch sensitivity, poor dimensional stability of products, easy bending deformation, poor weather resistance, light resistance, heat resistance and ageing resistance, and limits the application of the PP in some fields. In order to improve the deficiency in PP performance, the toughening modification of PP is generally realized by blending rubber, thermoplastic elastomer and PP, so as to form a blend with excellent impact strength and low-temperature toughness.

Polyolefin elastomers (POE) are typically random copolymers of high alpha-olefin content obtained by copolymerizing ethylene with alpha-olefins (e.g., 1-butene, 1-octene) using a metallocene catalyst. POE has better compatibility with polyolefin plastics (such as polyethylene, polypropylene and the like), can be used as a modifier of plastics, and obviously increases the flexibility and impact resistance of the materials. The crystalline ethylene chain in POE molecule can be used as physical cross-linking point to bear load, and the amorphous ethylene and octene long chain can endow excellent high elasticity, high strength, high elongation and excellent low-temperature performance. But because POE has poor flowability, and the rigidity of the material is greatly reduced after the POE is added. How to further improve the mechanical strength and modulus, and prepare the blending material with excellent comprehensive performance and balanced rigidity and toughness, and the core science problem facing the toughening modification of PP is still solved.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a preparation method of a novel elastomer, and the PLLA molecule contains terminal carboxyl groups and has higher reactivity with epoxy groups. Therefore, reactive polyolefin elastomer-glycidyl methacrylate (POE-g-GMA) is introduced into the blending system, PLLA is directly melt blended with the component containing the epoxy group, and the graft copolymer POE-g-PLLA is generated in situ in the processing process, so that the PLLA molecular chain is effectively fixed in the elastomer, and the novel elastomer with POE (high toughness) and PLLA (high modulus) components is prepared. Further, the modified polypropylene is used as a toughening agent to be blended with PP, so that the in-situ construction of the salami structure in the PP matrix is realized. POE as the outer shell layer of salami can effectively reduce interfacial tension between a matrix and an elastomer, improve interphase adhesion and promote effective transmission of interfacial stress, PLLA as the inclusion in salami can endow the material with certain rigidity and hardness, and finally PP blending material with balanced rigidity and toughness and excellent comprehensive performance is obtained.

In order to achieve the above object, in one aspect, the present invention provides a method for preparing a rigid-tough balance polypropylene composite material, which specifically comprises the following steps:

S1, melting and blending granules or powder of polyolefin elastomer-glycidyl methacrylate copolymer and polylactic acid in a mass ratio of 3:7-7:3 to obtain a uniform blend, then cooling the blend to room temperature, adjusting the content of the polyolefin elastomer-glycidyl methacrylate to 10-20 wt%, and then mixing the blend with polypropylene granules or powder (with a ratio of 60-79 wt%) at room temperature to obtain a mixture A, or directly adding granules or powder of the polyolefin elastomer-glycidyl methacrylate copolymer (with a ratio of 10-20 wt%) and polylactic acid (with a ratio of 9-20 wt%) into granules or powder (with a ratio of 60-71 wt%) of polypropylene, and mixing at room temperature to obtain a mixture B.

S2, putting the mixture A or B into a mixing mill, and carrying out melt blending at high temperature to ensure that the components are fully combined, so as to finally prepare the polypropylene composite material with high strength and high toughness, which is also called modified polypropylene.

As a preferable technical scheme of the invention, the method also comprises a pretreatment drying step of raw materials, and the specific operation is as follows:

And carrying out vacuum drying on the granules or powder of the polypropylene and the polylactic acid at the temperature of 60-80 ℃ for 24-48 hours. And carrying out vacuum drying on the granules or powder of the polyolefin elastomer-glycidyl methacrylate copolymer at the temperature of 40-50 ℃ for 24-48 h.

In addition, for the kneading apparatus and the process parameters for melt blending in step S1, the conditions are preferably selected such that an internal mixer or an extruder is used as the kneading apparatus. The rotation speed is set to be 50-100 rpm, and the blending time is set to be 10-15 min.

In the step S2, the operation parameters of the mixing equipment are further defined, wherein when an internal mixer is used, the mixing rotating speed is 50-100 rpm, and the mixing time is 10-15 min. When an extruder is used, the speed of blending can be extended to 50 to 150 rpm.

Preferably, in the steps S1 and S2, the temperature interval for melt blending is 180 to 230 ℃.

According to another important aspect of the present invention, there is also provided a polypropylene composite material prepared by the method described in detail above. Such composite materials exhibit excellent properties, benefiting from their unique manufacturing processes.

According to another important aspect of the invention, the invention also provides application of the prepared modified polypropylene as a master batch in the fields of automobiles, buildings, chemical industry, medical appliances, agriculture and the like.

According to the high-strength and high-toughness polypropylene composite material and the preparation method thereof, the following remarkable advantages can be realized by implementing the optimized technical scheme:

1) The polyolefin elastomer-glycidyl methacrylate copolymer utilized is re-reactive, which enhances the processability of the material and the mechanical properties of the final product.

2) The polylactic acid is an environment-friendly biodegradable polymer material, which is beneficial to improving the performance of the composite material, reduces the influence on the environment in the whole life cycle and accords with the concept of green manufacture.

3) The optimal proportion of each component of the rigid-tough balance polypropylene composite material is 60-79 wt% of matrix polypropylene, 15-20 wt% of polyolefin elastomer-glycidyl methacrylate copolymer and 6-20 wt% of polylactic acid; in the preparation process of the rigid-tough balance polypropylene, a key reaction mechanism, namely a novel elastomer formed by a polyolefin elastomer-glycidyl methacrylate copolymer and polylactic acid, is involved. Specifically, when melt blending is carried out, epoxy groups in POE-g-GMA and carboxyl groups in PLLA undergo a ring-opening reaction to generate a graft copolymer POE-g-PLLA, so that the dispersing effect and the toughening efficiency of the toughening agent are remarkably improved. The elastomer effectively improves the strength and toughness of the polypropylene material by combining chemical reaction and physical blending.

4) According to the invention, the mechanical property adjustability of the modified polypropylene is realized by finely regulating and controlling the proportion and the addition amount of the polyolefin elastomer-glycidyl methacrylate copolymer and the polylactic acid in the melt blending process. The method opens up a new way for expanding the application range of polypropylene in different industries. In addition, the composite material prepared by the invention shows the characteristic of high-performance polymer alloy, and provides excellent material selection for application fields requiring high strength and high toughness.

5) The invention has the advantages that the method can be implemented by means of conventional melting and mixing equipment, and the industrial preparation process is concise and efficient, thus being very suitable for large-scale industrial production.

6) In addition, the preparation method of the invention also considers the proportion of each component and the processing condition so as to ensure the optimal performance of the final product. The method is not only suitable for laboratory scale research, but also suitable for industrial production, and has wide application prospect.

Drawings

The invention will be elucidated in more detail below with reference to the drawings and to specific embodiments. The accompanying drawings are included to provide an understanding of the structure and principles of operation of the present invention, and wherein:

Fig. 1 shows Scanning Electron Microscope (SEM) images of comparative example 1 and example 1. A, b in the figure correspond to the internal microstructure of each sample, respectively, while "1" and "2" represent SEM observations at magnifications of 2K and 10K, respectively.

Fig. 2 shows Transmission Electron Microscope (TEM) images of comparative example 1 and example 1. Likewise, a, b represent the internal microstructure of each sample, and "1" and "2" correspond to TEM observations at magnifications of 1.5K and 6K, respectively.

Fig. 3 shows the comparative mechanical properties of comparative example 1 and example 1.

The implementation, functional features and unique advantages of the present invention will be further described with reference to the embodiments with reference to the accompanying drawings. Reference is made to the accompanying drawings and examples which provide a clearer explanation of the technical details of the present invention.

Detailed Description

The following description will make detailed description of the embodiments of the invention with reference to the accompanying drawings. It is emphasized that these specific examples are provided only to illustrate and exemplify the invention and are not intended to limit the scope of the invention. Any obvious modifications and alterations shall be included within the scope of protection of the present invention without departing from the spirit of the present invention.

In the following examples, all technical terms are used in the sense commonly understood by those skilled in the art unless otherwise indicated. Similarly, unless otherwise indicated, all reagents used were standard biochemical reagents and the methods were also in accordance with conventional operating specifications.

The following examples and comparative examples used the following raw materials were obtained from the manufacturers of H501 type polypropylene (PP) base material available from Toyo chemical Co Ltd (Tokyo, japan) having a melt flow index of 3.0 g/10 min, 2.16 kg at 230 ℃, polylactic acid (PLLA) having a number average molecular weight in the range of 5000 to 150000 g/mol, and polyolefin elastomer-glycidyl methacrylate copolymer (POE-g-GMA) having the brand SOG-03, incorporated by reference as "Kagaku Yi Rong" (Shanghai).

Comparative example 1 preparation of Polypropylene composite PP/POE-g-GMA, the mass ratio of the raw materials was set to 85:15. The method comprises the following specific steps:

Step S1, drying the raw materials, namely vacuum drying the PP granules at the temperature of 80 ℃ for 24h hours. Similarly, POE-g-GMA pellets were vacuum dried at a temperature of 50℃for a drying time of 24 h.

And S2, mixing raw materials, namely adding the dried POE-g-GMA granules into the dried PP granules, and fully mixing under the normal temperature condition to ensure uniform dispersion.

And S3, melt blending, namely adding the uniformly mixed raw materials into an internal mixer. Melt blending was performed at a speed of 50 rpm C for a duration of 10 min C at a temperature of 190C. Through the process, the modified polypropylene composite material is finally obtained.

Comparative example 2 preparation of Polypropylene composite PP/POE-g-GMA, the mass ratio of the raw materials was set to 90:10. The method comprises the following specific steps:

Comparative example 3 preparation of Polypropylene composite PP/POE-g-GMA, the mass ratio of the raw materials was set to 80:20. The method comprises the following specific steps:

Based on the comparative examples 1-3, the following examples 1-9 were respectively proposed, wherein the POE-g-GMA ratio was kept the same, the balance PLLA+PP ratio was used, and the raw materials were simultaneously blended in a two-step method, namely, the polyolefin elastomer-glycidyl methacrylate copolymer was melt blended with polylactic acid, and then mixed with polypropylene to form a mixture.

Example 1 preparation of Polypropylene composite PP/POE-30PLLA, fixed POE-g-GMA 15wt%, PLLA+PP 85wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials is 7:3. The method comprises the following specific steps:

Step S1, drying the raw materials, namely vacuum drying PP and PLLA granules at the temperature of 80 ℃ for 24 h. The POE-g-GMA pellets were vacuum dried at a temperature of 50℃for a drying time of 24 h as well.

Step S2. Pre-blending and mixing the dried POE-g-GMA pellets and PLLA pellets were blended at a temperature of 190℃and a rotational speed of 50 rpm for a duration of 10min to obtain a homogeneous blend. After the blend has cooled to room temperature, it is added to the dried PP pellets. Fully mixing under the normal temperature condition to ensure that the materials are uniformly dispersed, and obtaining the final mixture.

And S3, melt blending and modification, namely adding the mixture obtained in the step S2 into an internal mixer. Melt blending was performed at a speed of 50 rpm C for a duration of 10 min C at a temperature of 190C. Through the process, the modified polypropylene composite material is finally obtained.

As shown in FIG. 1, SEM analysis (15 wt% of POE-g-GMA mass fraction) of example 1 (POE-g-GMA toughened PP composite) and comparative example 1 (POE-30 PLLA toughened PP composite) showed that the addition of PLLA had a significant effect on the microstructure of the PP/POE-g-GMA blend. This is believed to be due to the ring-opening reaction of the epoxide groups of the POE-g-GMA with the terminal hydroxyl groups of the PLLA during melt blending, resulting in the formation of new chemical bond linkages. This attachment not only enhances the internal bonding forces of the material, but also promotes dispersion of the elastomer in the polypropylene matrix.

As shown in fig. 2, when TEM analysis is performed on example 1 and comparative example 1, it can be seen more clearly that a unique "salami" structure is formed in the sample of example 1, and the salami structure is distributed in the PP matrix as a sea-island structure, which corresponds well to the SEM image of example 1 in fig. 1. The PLLA and the PP matrix are incompatible, so that PLLA grafted molecular chains are selectively dispersed in POE-g-GMA phase, and the in-situ construction of the salami structure in the PP matrix is realized. The POE is used as an outer shell layer of the salami, so that the interfacial tension between a matrix and an elastomer can be effectively reduced, the interphase adhesion force can be improved, and the effective transmission of the interfacial stress can be promoted, so that when the material is subjected to impact stress, the matrix material can well transfer the stress to a toughening agent dispersed phase; meanwhile, PLLA is used as an inclusion of salami, has higher rigidity and hardness, so that the prepared polypropylene composite material has high toughness and obviously improved strength, thereby meeting the requirement of high-performance materials. By controlling the microscopic morphology of the blend, the rigidity and toughness of the PP composite material are synergistically improved, and explanation is made for the PP blend material with balanced rigidity and toughness prepared next.

Performance test:

The modified polypropylene samples prepared in the comparative example 1 and the example 1 are respectively subjected to notch impact and tensile test to characterize the mechanical properties of the samples.

Impact test, namely preparing impact bars with the length of 80 mm times the width of 10 mm times the thickness of 4 mm by adopting a microinjection molding instrument, wherein the v-shaped notch depth is 2 mm, and then standing for 12-24 hours at room temperature. The bars were impact tested using an impact tester according to GB/T16420-1997, using a pendulum energy of 2J.

And (3) stretching test, namely preparing dumbbell-shaped stretching bars with the length of 20 mm multiplied by the width of 4 mm multiplied by the thickness of 2mm by adopting a microinjection molding apparatus, and standing for 12-24 hours at room temperature. The bars were tensile tested using a universal material tester at a tensile rate of 10 mm/min.

Comparative mechanical properties were tested for example 1 and comparative example 1, and the results are shown in fig. 3.

Table 1 is a summary of specific data for mechanical properties of example 1 and comparative example 1:

TABLE 1

Comprehensive impact and tensile property analyses were performed on example 1 and comparative example 1. The results show that comparative example 1 has an impact strength of only about 9.7 kJ/m2 and that both Young's modulus and elongation at break are at a low level. In contrast, example 1 employs a two-step blending strategy by first blending POE-g-GMA with PLLA and then melt blending the resulting blend with PP. This strategy significantly improves the performance of the material. Specifically, the impact strength of example 1 reached about 26.7 kJ/m2, which was improved by approximately 175% as compared to comparative example 1. This is mainly because the chemical bond formed between POE-g-GMA and PLLA enhances the internal bonding force of the material in the two-step blending process, while the elastomeric properties of POE-g-GMA effectively improve the toughness of the material. In addition, the Young's modulus of example 1 is about 0.92 GPa, which is significantly higher than that of comparative example 1, 0.74 GPa, indicating that the modified PP-based composite is also significantly improved in stiffness. The increase in elongation at break (from 898.2% for comparative example 1 to 950.0% for example 1) further demonstrates the improvement in tensile properties of the material, which makes it more ductile and tough when subjected to external forces.

In summary, PP-based composite materials having both high impact strength and excellent tensile properties were successfully prepared by the two-step blending process of example 1.

Example 2 preparation of Polypropylene composite PP/POE-50PLLA, fixed POE-g-GMA 15wt%, PLLA+PP 85wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials is 5:5. The method comprises the following specific steps:

Example 3 preparation of Polypropylene composite PP/POE-70PLLA, fixed POE-g-GMA 15wt%, PLLA+PP 85wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 3:7. The method comprises the following specific steps:

Step S1, drying the raw materials, namely vacuum drying PP and PLLA granules at the temperature of 80 ℃ for 24 h. The POE-g-GMA pellets were vacuum dried at a temperature of 50℃for a drying time of 24h as well.

Example 4 preparation of Polypropylene composite PP/POE-30PLLA, fixed POE-g-GMA with a mass fraction of 10wt%, PLLA+PP with a 90wt% ratio, wherein the POE-g-GMA/PLLA raw material mass ratio was 7:3. The method comprises the following specific steps:

Example 5 preparation of Polypropylene composite PP/POE-50PLLA, fixed POE-g-GMA with a mass fraction of 10wt%, PLLA+PP with a 90wt% ratio, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 5:5. The method comprises the following specific steps:

Example 6 preparation of Polypropylene composite PP/POE-70PLLA, fixed POE-g-GMA with a mass fraction of 10wt%, PLLA+PP with a 90wt% ratio, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 3:7. The method comprises the following specific steps:

Example 7 preparation of Polypropylene composite PP/POE-30PLLA, fixed POE-g-GMA with a mass fraction of 20 wt% and PLLA+PP 80wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 7:3. The method comprises the following specific steps:

Example 8 preparation of Polypropylene composite PP/POE-50PLLA, fixed POE-g-GMA with a mass fraction of 20 wt%, PLLA+PP 80wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 5:5. The method comprises the following specific steps:

Example 9 preparation of Polypropylene composite PP/POE-70PLLA with a mass fraction of fixed POE-g-GMA of 20wt% and PLLA+PP of 80wt%, wherein the mass ratio of POE-g-GMA/PLLA raw materials was 3:7. The method comprises the following specific steps:

Table 2 shows the summary of the specific data of the mechanical properties of examples 1 to 9 and comparative examples 1 to 3 (the test methods are the same as in example 1):

TABLE 2

In order to further prove the beneficial technical effects of the invention, based on the above examples 1-9, the corresponding examples 10-18 are also provided, and the difference is that the two-step blending in the examples 1-9 is replaced by the one-step blending at normal temperature, namely, the polyolefin-glycidyl methacrylate copolymer and the polylactic acid are added into the polypropylene, the mixture is obtained by one-step mixing, and then the mixture is subjected to melt blending at the temperature of 190 ℃ at the rotating speed of 50 rpm for the duration of 10min, and the modified polypropylene composite material is finally obtained.

Table 3 shows the summary of the specific data of the mechanical properties of examples 10 to 18 and comparative examples 1 to 3 (the test methods are the same as in example 1):

TABLE 3 Table 3

The present invention is further analyzed in conjunction with tables 2,3 and examples 1-18.

The impact properties of examples 1 and 10 and comparative example 1 were analyzed. The results of the analysis showed that the impact strength of comparative example 1 was about 9.7 kJ/m2, whereas in the samples of examples 1 and 10, the impact strength was significantly improved due to the grafting of PLLA in the elastomer. In particular, in example 1, the POE-g-GMA and PLLA were first blended by a two-step method, and then the obtained blend was melt blended with PP, and the impact strength of the modified polypropylene was further improved compared with example 10, thereby obtaining a PP-based composite material with higher toughness.

The impact properties of examples 1-3 and 10-12, 4-6 and 13-15, 7-9 and 16-18 were analyzed. The analysis results show that the impact strength of the material is improved with the increase of the PLLA content (namely the decrease of the PP content). However, when the PLLA content reaches a certain critical value, a significant decrease in the notched impact strength of the material occurs. We speculate that, with the elastomer content remaining unchanged, PLLA fails to achieve good dispersion in the elastomer domains as the PLLA proportion increases, which may be responsible for the reduced impact strength.

Comparative examples 1, 2 and 3 were subjected to comparative analysis of impact properties. It can be seen that the impact strength of the material increases significantly with increasing POE-g-GMA content.

Examples 1 and 10 and comparative example 1 were subjected to analysis of tensile properties. The analysis results show that examples 1 and 10 each exhibit higher Young's modulus and elongation at break. In particular, in example 1, POE-g-GMA was first blended with PLLA and then melt blended with PP by a two-step process, which further improved the Young's modulus and elongation at break of the modified polypropylene. This is because the two-step process promotes the immobilization of PLLA in elastomer (POE-g-GMA) and thus results in a structure with "salami" which is more effective in enhancing the toughness of PP.

The tensile properties of examples 1-3 and 10-12, 4-6 and 13-15, and 7-9 and 16-18 were analyzed. The analysis results show that the Young's modulus of the material increases with increasing PLLA content (i.e., decreasing PP content). However, when the PLLA content reaches a certain critical value, a significant decrease in elongation at break of the material occurs. This shows that at higher PLLA levels, the plastic deformation capacity is reduced, although the stiffness of the material is increased.

Comparative examples 1, 2 and 3 were analyzed for tensile properties. The analysis results show that the Young's modulus of the material decreases with increasing POE-g-GMA content, which means that the rigidity of the material decreases. At the same time, the elongation at break of the material increases, which means that the plastic deformability of the material is enhanced. The change trend shows that the rigidity and toughness balance of the material can be regulated to a certain extent by adjusting the content of POE-g-GMA.

In summary, the polypropylene composite material PP/POE-g-GMA/PLLA (the mass fraction of POE-g-GMA is 15% or 20% by weight, the PLLA+PP accounts for 85% or 80% by weight, and the mass ratio of POE-g-GMA/PLLA raw materials is 7:3 or 5:5) has the optimal comprehensive performance. At the same time, PLLA and the PP matrix are incompatible, so that PLLA is selectively dispersed in the POE-g-GMA phase to form a unique salami structure, and the PLLA is distributed in the PP matrix in a sea island structure. In the ternary system of PP/POE-g-GMA/PLLA, the blending of the one-step blending two-step method is more excellent, and the superiority is mainly reflected in several aspects. Firstly, the method can remarkably improve the compatibility, because the epoxy group in POE-g-GMA can chemically react with the hydroxyl and carboxyl in PLLA to form more stable interface combination, thereby improving the compatibility of the whole system. Secondly, the two-step method blending allows PLLA and POE-g-GMA to fully react in the first step, so that the reaction time is increased, the efficiency of the grafting reaction is improved, more epoxy groups are ensured to participate in the reaction, and the interface cohesive force is enhanced. In addition, the method can improve the dispersibility, ensure the PLLA to be dispersed more uniformly in the system, reduce the phase separation in the blend and improve the overall performance of the material. Meanwhile, the two-step method blending can optimize the processing conditions, reduce the processing problems possibly encountered in the one-step method, such as selecting the processing temperature and time more suitable for the two materials, and then adjust the processing parameters according to the formed good compatibility, thereby improving the processing performance of the whole system. Finally, the two-step blending also contributes to improving the stability of the material properties, since a stable interface structure is formed in the first step, and the performance fluctuation of the whole system is smaller when PP is added, so that the performance of the final product is easier to control. Overall, two-step blending offers advantages over one-step blending in PP/POE-g-GMA/PLLA ternary systems by improving compatibility, reaction efficiency, dispersibility, optimizing processability, and enhancing performance stability. The two-step method successfully improves the comprehensive performance of each component of the incompatible blend, realizes the synergistic effect on the performance, and obtains the polypropylene composite material with high strength and high toughness. In addition, the mechanical properties of the modified polypropylene composite material can be effectively adjusted by accurately adjusting and controlling the adding proportion of polypropylene, polyolefin elastomer-glycidyl methacrylate copolymer and polylactic acid, so that flexibility and customization possibility are provided for meeting the requirements of different application scenes.

The above examples are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention. The scope of the invention encompasses all forms which come within the spirit of the invention and their equivalents. Any modification and adjustment of the essential and essential features of the present invention should be included in the scope of the present invention. The specific scope of protection is indicated by the appended claims.

Claims

1. A method for preparing a rigid-toughness balanced polypropylene composite material, characterized in that it comprises the following steps:

S1. Melt-blending polyolefin elastomer-glycidyl methacrylate copolymer pellets or powders with polylactic acid pellets or powders in a mass ratio of 3:7 to 7:3 to obtain a uniform blend, then cooling to room temperature, fixing the content of polyolefin elastomer-glycidyl methacrylate to 15 to 20 wt %, and then adding the blend to 60 to 79 wt % of polypropylene pellets or powders, and mixing at room temperature to obtain a mixture A; the polylactic acid is L-type polylactic acid and contains terminal carboxyl groups;

S2. Adding mixed material A into a mixing device for melt blending to obtain modified polypropylene.

2. The method for preparing a rigid-toughness balanced polypropylene composite material according to claim 1, characterized in that, before step S1, it also includes a drying step for the raw materials, which is specifically as follows:

The polypropylene and polylactic acid are vacuum dried at a temperature of 60-80°C for 24-48 h; the polyolefin elastomer-glycidyl methacrylate copolymer is vacuum dried at a temperature of 40-50°C for 24-48 h.

3. The method for preparing a rigid-toughness balanced polypropylene composite material according to claim 1, characterized in that, in step S1, an internal mixer or an extruder is used for melt blending, the speed is 50-100 rpm, and the blending time is 10-15 min.

4. The method for preparing a rigidity-toughness balanced polypropylene composite material according to claim 1, characterized in that in step S2, the mixing equipment is one of an internal mixer or an extruder.

5. The method for preparing a rigid-toughness balanced polypropylene composite material according to claim 4 is characterized in that the speed of the internal mixer blending is 50-100 rpm and the blending time is 10-15 min.

6. The method for preparing a rigid-toughness balanced polypropylene composite material according to claim 4, wherein the speed of the extruder blending is 50-100 rpm.

7. The method for preparing a rigid-toughness balanced polypropylene composite material according to any one of claims 1 to 6, characterized in that in steps S1 and S2, the temperature range for melt blending is 180-230°C.

8. A polypropylene composite material, characterized in that it is prepared by the method according to any one of claims 1 to 7.