High-strength antibacterial polypropylene composite material and preparation method thereof

Abstract

The invention discloses a high-strength antibacterial polypropylene composite material and a preparation method thereof. The composite material comprises the following components in parts by weight: 100 parts of polypropylene, 15-25 parts of glass fiber, 1-8 parts of a compatilizer, 3-6 parts of unsaturated polyester, 1-5 parts of a stabilizer, 0.1-0.5 part of an initiator, 0.1-0.3 part of a metal ion antibacterial agent and 0.2-1.5 parts of an antioxidant, the stabilizer is selected from at least one of methyl methacrylate, acrylonitrile and divinyl benzene; the melting processing temperature of the polypropylene material is 160-175 DEG C. According to the invention, a micro-crosslinking structure is formed in the glass fiber reinforced polypropylene, so that the anisotropic shrinkage difference of the glass fiber reinforced polypropylene is effectively reduced, and the appearance quality defects caused by anisotropic characteristics of anisotropic shrinkage of the current glass fiber reinforced polypropylene material are reduced.

Description

Technical Field

[0001] This application relates to the field of polypropylene materials, and particularly to a high-strength antibacterial polypropylene composite material and a preparation method thereof. Background Art

[0002] As a general thermoplastic plastic, polypropylene is widely used in fields such as automotive parts, household appliance casings, and packaging materials due to its advantages of light weight, chemical corrosion resistance, easy processing and low cost. However, the mechanical strength, dimensional stability and creep resistance of ordinary polypropylene are relatively limited, making it difficult to meet the stringent requirements of high-end structural parts for material properties. Therefore, glass fiber reinforcement technology is widely used in the field of polypropylene modification, and the rigidity, tensile strength and heat resistance of the material are significantly improved by adding glass fibers to the matrix. For example, the patent application with the publication number CN113388189A discloses a polypropylene composition containing glass fibers, and effectively improves the creep resistance and mechanical properties of the material by optimizing fiber dispersion and interfacial bonding.

[0003] However, with the expansion of application scenarios towards thin-walled and lightweight directions, the limitations of glass fiber reinforced polypropylene materials gradually emerge. Specifically, due to the high aspect ratio of glass fibers, they are prone to highly orient along the flow direction during injection molding or extrusion processing, resulting in a significant difference in thermal shrinkage rates of the material in the direction parallel and perpendicular to the flow direction. This anisotropic shrinkage is particularly prominent in thin-walled planar structure products (such as electronic device casings, thin-walled containers), causing problems such as edge warping, surface ripple wrinkles and even local cracking of the product, severely restricting the dimensional accuracy and appearance quality of the product. In addition, traditional glass fiber reinforced polypropylene lacks antibacterial function and is limited in applications in fields with high hygiene requirements such as medical devices (such as casings) and food packaging (such as containers). Therefore, developing a polypropylene composite material with high mechanical strength, low shrinkage anisotropy and long-term antibacterial performance has become the key direction to break through the bottleneck of existing technologies and expand the application scenarios of materials. Summary of the Invention

[0004] This application provides a high-strength antibacterial polypropylene composite material and a preparation method thereof, which effectively reduce the difference in anisotropic shrinkage rate by forming a micro-crosslinked structure in glass fiber reinforced polypropylene, and reduce the appearance quality defects caused by the anisotropic shrinkage characteristics of the current glass fiber reinforced polypropylene materials.

[0005] In the first aspect, this application provides a high-strength antibacterial polypropylene composite material, which comprises the following components in parts by weight: 100 parts of polypropylene, 15 - 25 parts of glass fiber, 1 - 8 parts of compatibilizer, 5 - 10 parts of unsaturated polyester, 1 - 5 parts of stabilizer, 0.1 - 0.5 parts of initiator, 0.1 - 0.3 parts of metal ion antibacterial agent, 0.2 - 1.5 parts of antioxidant; the stabilizer is selected from at least one of methyl methacrylate, acrylonitrile, and divinylbenzene; the melt processing temperature of the polypropylene material is 160 - 175 °C.

[0006] In any of the above technical solutions, the stabilizer contains 30 - 50 wt% of divinylbenzene.

[0007] In any of the above technical solutions, the initiator is dicumyl peroxide.

[0008] In any of the above technical solutions, the polypropylene is linear isotactic polypropylene, and the melt index under the conditions of 230 °C / 2.16 kg is 20 - 30 g / 10 min.

[0009] In this application, by introducing unsaturated polyester, initiator, and stabilizer into the polypropylene resin, a mild micro-crosslinked network is constructed using dynamic crosslinking technology to inhibit the shrinkage anisotropy of glass fiber reinforced polypropylene. During the melt processing, the initiator (such as dicumyl peroxide) decomposes upon heating to generate free radicals, which attack the tertiary carbon atoms of the polypropylene molecular chain to form macromolecular free radicals (PP·). At this time, the double bond of the stabilizer (such as methyl methacrylate / MMA) captures the free radicals through chain transfer to generate a more stable intermediate (such as PP - MMA·), improving the crosslinking activity and reducing the β - scission of the polypropylene main chain caused by free radicals, avoiding excessive decrease in molecular weight and affecting its mechanical properties. The stable intermediate further undergoes a graft reaction with the double bond of the unsaturated polyester (at this time, monovinyl stabilizers such as methyl methacrylate and acrylonitrile participate in the graft reaction as comonomers), forming crosslinking points and generating local micro-crosslinked gels.

[0010] The above - mentioned moderate crosslinking reaction is beneficial to balancing the anisotropic shrinkage of the material and improving the strength performance. The bifunctional group characteristic of divinylbenzene enables it to connect two polypropylene chains or a polypropylene chain and an unsaturated polyester chain simultaneously, which is particularly significant for improving the crosslinking density. However, when its dosage is too high (greater than 50 wt%), it will cause deterioration of the material's flexibility and notch impact strength. Further, if divinylbenzene is used alone as the stabilizer, it is easy to cause the material to become hard and brittle, not only reducing the notch impact strength but also deteriorating the tensile strength. Monovinyl stabilizers such as methyl methacrylate have a weaker crosslinking effect. When compounded with divinylbenzene, it can form a sufficient crosslinked network to balance the shrinkage stress and avoid over - crosslinking leading to deterioration of the material's flexibility or even embrittlement. Finally, the difference in shrinkage rate between the parallel and perpendicular directions of the material is reduced to less than 0.3%, effectively alleviating the warping and cracking problems of thin - wall products while maintaining good mechanical properties.

[0011] It should be noted that polar monomers such as maleic anhydride should not be used as stabilizers in this application. Their chain transfer performance is poor, and it is difficult to effectively capture free radicals and form stable intermediates, which may lead to increased β-scission of the polypropylene main chain, a decrease in molecular weight, and an impact on mechanical properties. Moreover, side reactions may be triggered, interfering with the formation of the crosslinked network.

[0012] In any of the above technical solutions, the unsaturated polyester is prepared by polycondensation of an unsaturated dibasic acid or anhydride, a saturated dibasic acid, pyridine-containing terephthalic acid, and a diol in a molar ratio of 0.4 - 0.5:0.4 - 0.5:0.1 - 0.2:1.

[0013] In any of the above technical solutions, the pyridine-containing terephthalic acid is selected from 2-(4-pyridyl)terephthalic acid and / or 2,5-bis(pyridin-4-yl)terephthalic acid.

[0014] In any of the above technical solutions, the metal ion antibacterial agent is selected from zinc ion antibacterial agents and / or silver ion antibacterial agents.

[0015] In the synthesis of the unsaturated polyester, introducing pyridine-containing terephthalic acid (such as 2,5-bis(pyridin-4-yl)terephthalic acid) endows the polyester chain with nitrogen-containing coordination groups. On the one hand, these pyridine groups can form a coordination network with metal ions, which can reduce the anisotropy of shrinkage in all directions without deteriorating the notched impact strength of the material, and achieve the coordinated improvement of antibacterial function and appearance quality. On the other hand, they can undergo coordination complexation with metal ion antibacterial agents (such as silver ions or zinc ions) to form stable metal-organic complexes, thereby firmly anchoring the antibacterial agent in the polypropylene matrix and avoiding migration loss during processing or use. In addition, the electron donor characteristics of the pyridine group can enhance the redox activity of metal ions, further improving the destruction efficiency of antibacterial agents on bacterial cell membranes. Experiments show that the antibacterial rate of the composite material containing pyridine polyester against Escherichia coli and Staphylococcus aureus can reach more than 99%, and it still maintains more than 90% antibacterial activity after 50 washes.

[0016] In any of the above technical solutions, the raw materials of the compatibilizer include the following components in parts by mass: 100 parts of maleic anhydride-modified liquid polybutadiene, 10 - 30 parts of hydroxyacrylate, and 0.5 - 2 parts of catalyst. The maleic anhydride-modified liquid polybutadiene and hydroxyacrylate are subjected to an esterification reaction under the action of the catalyst to obtain the compatibilizer.

[0017] In any of the above technical solutions, the temperature of the esterification reaction is 90 - 120 °C.

[0018] In any of the above technical solutions, the hydroxyacrylate is selected from at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0019] In any of the above technical solutions, the catalyst is p-toluenesulfonic acid.

[0020] In this application, the amount of unsaturated polyester is relatively high. To ensure the compatibility and dispersibility of the two phases, a specific compatibilizer is used in this application. This compatibilizer has both a non-polar main chain of polybutadiene and polar side groups (ester groups or unreacted hydroxyl groups) of acrylate. The non-polarity of its polybutadiene main chain is similar to that of PP, and the interfacial bonding can be enhanced through chain segment entanglement or van der Waals forces. The acrylate chain segments form hydrogen bonds or dipole-dipole interactions with the ester groups in the unsaturated polyester, etc., improving the compatibility of the two phases to ensure the crosslinking effect. In addition, the polybutadiene main chain in this compatibilizer has a certain toughening effect, which helps to improve the loss of flexibility caused by crosslinking and increase its impact strength.

[0021] In any of the above technical solutions, the length of the glass fiber is 1-5 mm, the aspect ratio ≥ 20, and the surface is treated with a silane coupling agent.

[0022] In any of the above technical solutions, the silane coupling agent is selected from at least one of vinyl silane coupling agents, amino silane coupling agents, and epoxy silane coupling agents.

[0023] In any of the above technical solutions, the dosage of the silane coupling agent is 2-4% of the mass of the glass fiber.

[0024] The above surface treatment of the glass fiber with a silane coupling agent in this application means that by the spraying method, a silane coupling agent solution, such as an ethanol solution, is evenly sprayed on the surface of the glass fiber and cured at 110-120 °C for 20-30 minutes to obtain the treated glass fiber.

[0025] In a second aspect, this application provides a method for preparing a high-strength antibacterial polypropylene composite material, including: Mix polypropylene, compatibilizer, unsaturated polyester, stabilizer, initiator evenly and then feed them into a screw extruder, and melt and blend at 160-175 °C for 5-10 minutes; then add glass fiber, antioxidant and metal ion antibacterial agent from the side feeding port, and continue to mix and knead at 190-220 °C for 3-6 minutes, and then extrude and pelletize to obtain the product.

[0026] In summary, this application has the following beneficial effects: The high-strength antibacterial polypropylene composite provided by this application significantly reduces the anisotropic shrinkage of glass fiber-reinforced polypropylene through dynamic micro-crosslinking technology. The shrinkage rate difference between the parallel and perpendicular directions is controlled within 0.3%, effectively solving the warping and cracking problems of thin-walled products. At the same time, the coordination effect of the pyridine-containing polyester and the metal ion antibacterial agent endows the material with long-term antibacterial performance and the ability to further inhibit anisotropic shrinkage. The antibacterial rate exceeds 99% and the wash resistance is excellent. The material has both high mechanical strength and good processing fluidity (melt index 20-30 g / 10 min), and is suitable for fields such as automotive interiors, electronic enclosures, and medical devices. The preparation process realizes the synergistic optimization of dynamic crosslinking and fiber dispersion through segmented temperature control (160-175 °C for premixing and modification and 190-220 °C for final mixing). The process window is wide and suitable for industrial production. Detailed implementation mode Preparation example

[0027] Preparation example 1, an unsaturated polyester, with the following raw material ratios: Maleic anhydride 220.6 g (2.25 mol), phthalic anhydride 333.3 g (2.25 mol), 2,5-bis(pyridin-4-yl)terephthalic acid 125 g (0.5 mol), propylene glycol 380.5 g (5.0 mol), p-toluenesulfonic acid (catalyst) 50 g.

[0028] The preparation process is as follows: Add maleic anhydride, phthalic anhydride, 2,5-bis(pyridin-4-yl)terephthalic acid and propylene glycol to the reaction kettle, and heat up to 160 °C under ammonia protection. Add the catalyst, gradually heat up to 190 °C, and stir and react for 4 hours; evacuate to -0.095 MPa, continue to react for 2 hours to remove by-product water; cool to 80 °C and discharge to obtain a light yellow viscous polyester with an acid value ≤ 15 mgKOH / g.

[0029] Preparation example 2, an unsaturated polyester, with the following raw material ratios: Maleic anhydride 245.2 g (2.5 mol), phthalic anhydride 296.2 g (2.0 mol), 2-(4-pyridyl)terephthalic acid 125 g (0.5 mol), ethylene glycol 310.4 g (5.0 mol), p-toluenesulfonic acid (catalyst) 50 g.

[0030] The preparation process is as follows: Add maleic anhydride, phthalic anhydride, 2-(4-pyridyl)terephthalic acid and propylene glycol to the reaction kettle, and heat up to 160 °C under ammonia protection. Add the catalyst, gradually heat up to 185 °C, and stir and react for 3 hours; evacuate to -0.095 MPa, continue to react for 2 hours to remove by-product water; cool to 80 °C and discharge to obtain a light yellow viscous polyester with an acid value ≤ 12 mgKOH / g.

[0031] Preparation Example 3, an unsaturated polyester, the raw material ratio is as follows: Maleic anhydride 232.1 g (2.0 mol), phthalic anhydride 292.3 g (2.0 mol), 2,5-di(pyridin-4-yl)terephthalic acid 250 g (1 mol), butanediol 450.6 g (5.0 mol), p-toluenesulfonic acid (catalyst) 60 g.

[0032] The preparation process is as follows: Maleic anhydride, phthalic anhydride, 2,5-di(pyridin-4-yl)terephthalic acid and propylene glycol were added to the reactor, and the temperature was raised to 160°C under the protection of ammonia. Catalyst was added, the temperature was gradually raised to 5°C, and the reaction was stirred for 4 hours; the vacuum was evacuated to -0.095MPa, and the reaction was continued for 3 hours to remove the by-product water; the reaction was cooled to 80°C, and the light yellow viscous polyester was obtained, and the acid value was ≤10mgKOH / g.

[0033] Preparation Example 4, an unsaturated polyester, is different from Preparation Example 1 in that 2,5-di(pyridin-4-yl)terephthalic acid is replaced by an equal mole of terephthalic acid, and the raw material ratio is as follows: Maleic anhydride 220.6g (2.25mol), phthalic anhydride 333.3g (2.25mol), terephthalic acid 83.1g (0.5mol), propylene glycol 380.5g (5.0mol), p-toluenesulfonic acid (catalyst) 50g.

[0034] The preparation process is the same as that of Preparation Example 1.

[0035] Preparation Example a, a compatibilizer, is prepared as follows: 1 kg of maleic anhydride modified liquid polybutadiene (Evonik POLYVEST® MA-75) was mixed evenly with 0.2 kg of hydroxyethyl acrylate and 0.01 kg of p-toluenesulfonic acid, and heated to 110°C under nitrogen protection, and stirred for 3 hours. The reaction liquid was cooled to below 60°C, and an appropriate amount of acetone was added to precipitate the product, which was filtered and vacuum dried for 24 hours to obtain a compatibilizer.

[0036] Preparation Example b, a compatibilizer, is prepared as follows: 1 kg of maleic anhydride modified liquid polybutadiene (Ricon 131MA17) was mixed evenly with 0.1 kg of hydroxyethyl methacrylate and 0.01 kg of p-toluenesulfonic acid, and heated to 100°C under nitrogen protection, and stirred for 4 hours. The reaction liquid was cooled to below 60°C, and an appropriate amount of acetone was added to precipitate the product, which was filtered and vacuum dried for 24 hours to obtain a compatibilizer.

[0037] Preparation Example c, a compatibilizer, is prepared as follows: Mix 1 kg of maleic anhydride-modified liquid polybutadiene (Ricon 131MA20) evenly with 0.3 kg of hydroxypropyl acrylate and 0.02 kg of p-toluenesulfonic acid. Under nitrogen protection, heat the mixture to 120 °C and stir for 3 h. Cool the reaction solution to below 60 °C, add an appropriate amount of acetone to precipitate the product, filter, and then dry it under vacuum for 24 hours to obtain the compatibilizer. Example

[0038] Example 1. A high-strength antibacterial polypropylene composite material is prepared according to the following steps: Raw material preparation: Linear isotactic polypropylene (230 °C / 2.16 kg, melt index 30 g / 10 min): 1.0 kg; glass fiber (length 3 mm, aspect ratio 25, surface treated with vinyl silane coupling agent, dosage 3 wt%): 0.2 kg; compatibilizer (Preparation Example a): 0.05 kg; unsaturated polyester (Preparation Example 1): 0.08 kg; stabilizer (methyl methacrylate and divinylbenzene with a mass ratio of 6:4): 0.04 kg; dicumyl peroxide: 0.003 kg; silver ion antibacterial agent (ADM-Ag08): 0.002 kg; antioxidant (antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1): 0.01 kg.

[0039] The preparation steps are as follows: Premix polypropylene, compatibilizer, unsaturated polyester, stabilizer, and initiator and add them to the main feeding port of a twin-screw extruder; set the temperature of each zone of the extruder: 160 °C (feeding zone), 170 °C (melting zone), 175 °C (mixing zone), rotation speed 200 rpm, and melt blend for 8 minutes.

[0040] Add glass fiber, antioxidant, and antibacterial agent from the side feeding port, heat to 190 °C (melting zone) and 210 °C (mixing zone), knead for 5 minutes, extrude and pelletize, and obtain composite material pellets after water cooling and pelletizing.

[0041] Example 2. A high-strength antibacterial polypropylene composite material is prepared according to the following steps: Raw material preparation: Linear isotactic polypropylene (230 °C / 2.16 kg, melt index 20 g / 10 min): 1.0 kg; glass fiber (length 1 mm, aspect ratio 20, surface treated with vinyl silane coupling agent, dosage 2 wt%): 0.15 kg; compatibilizer (Preparation Example b): 0.08 kg; unsaturated polyester (Preparation Example 2): 0.05 kg; stabilizer (acrylonitrile and divinylbenzene with a mass ratio of 5:5): 0.05 kg; dicumyl peroxide: 0.001 kg; zinc ion antibacterial agent (iHeir-907): 0.001 kg; antioxidant (antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1): 0.02 kg.

[0042] The preparation steps are as follows: Premix polypropylene, compatibilizer, unsaturated polyester, stabilizer, and initiator, and then add them to the main feeding port of a twin-screw extruder; set the temperatures of each zone of the extruder: 160 °C (feeding zone), 165 °C (melting zone), 170 °C (mixing zone), rotate at 200 rpm, and melt blend for 10 minutes.

[0043] Add glass fiber, antioxidant, and antibacterial agent from the side feeding port, raise the temperature to 195 °C (melting zone) and 210 °C (mixing zone), knead for 5 minutes, extrude and pelletize, and obtain composite material pellets through water-cooled pelletizing.

[0044] Example 3, a high-strength antibacterial polypropylene composite material, is prepared according to the following steps: Raw material preparation: Linear isotactic polypropylene (230 °C / 2.16 kg, melt index 30 g / 10 min): 1.0 kg; glass fiber (length 5 mm, aspect ratio 30, surface treated with vinyl silane coupling agent, dosage 4 wt%): 0.25 kg; compatibilizer (Preparation Example c): 0.03 kg; unsaturated polyester (Preparation Example 3): 0.1 kg; stabilizer (methyl methacrylate and divinylbenzene with a mass ratio of 7:3): 0.04 kg; dicumyl peroxide: 0.005 kg; silver ion antibacterial agent (ADM-Ag08): 0.003 kg; antioxidant (antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1): 0.02 kg.

[0045] The preparation steps are as follows: Premix polypropylene, compatibilizer, unsaturated polyester, stabilizer, and initiator, and then add them to the main feeding port of a twin-screw extruder; set the temperatures of each zone of the extruder: 160 °C (feeding zone), 175 °C (melting zone), 175 °C (mixing zone), rotate at 300 rpm, and melt blend for 5 minutes.

[0046] Add glass fiber, antioxidant, and antibacterial agent from the side feeding port, raise the temperature to 195 °C (melting zone) and 220 °C (mixing zone), knead for 4 minutes, extrude and pelletize, and obtain composite material pellets through water-cooled pelletizing.

[0047] Example 4, a high-strength antibacterial polypropylene composite material, is different from Example 1 in that in the stabilizer, a composition of methyl methacrylate and divinylbenzene is used, and the dosage ratio of divinylbenzene is 60 wt%.

[0048] Example 5, a high-strength antibacterial polypropylene composite material, is different from Example 1 in that in the stabilizer, a composition of methyl methacrylate and divinylbenzene is used, and the dosage ratio of divinylbenzene is 20 wt%.

[0049] Example 6. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that methyl methacrylate is used to replace divinylbenzene in the stabilizer in equal mass.

[0050] Example 7. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that divinylbenzene is used to replace methyl methacrylate in the stabilizer in equal mass.

[0051] Example 8. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that the unsaturated polyester of Preparation Example 4 is used to replace the unsaturated polyester of Preparation Example 1 in equal mass.

[0052] Example 9. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that maleic anhydride grafted polypropylene (grafting rate 1.2%) is used to replace the compatibilizer prepared in Preparation Example a in equal mass.

[0053] Example 10. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that maleic anhydride modified liquid polybutadiene (Evonik POLYVEST® MA-75) is used to replace the compatibilizer prepared in Preparation Example a in equal mass. Comparative Example

[0054] Comparative Example 1. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that polypropylene is used to replace the stabilizer in equal mass in the raw materials of the composite material.

[0055] Comparative Example 2. A high-strength antibacterial polypropylene composite, which is different from Example 1 in that polypropylene is used to replace the unsaturated polyester in equal mass in the raw materials of the composite material.

[0056] Comparative Example 3. A high-strength antibacterial polypropylene composite is prepared according to the following steps: Raw material preparation: Linear isotactic polypropylene (230 °C / 2.16 kg, melt index 30 g / 10 min): 1.0 kg; glass fiber (length 3 mm, aspect ratio 25, surface treated with vinyl silane coupling agent, dosage 3 wt%) 0.2 kg; maleic anhydride grafted polypropylene (grafting rate 1.2%) 0.05 kg; silver ion antibacterial agent (ADM-Ag08) 0.002 kg; antioxidant (antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1) 0.01 kg.

[0057] The preparation steps are as follows: Premix polypropylene, antioxidant and antibacterial agent and add them to the main feeding port of a twin-screw extruder; set the temperature of each zone of the extruder: 160 °C (feeding zone), 170 °C (melting zone), 175 °C (mixing zone), rotation speed 200 rpm, and melt blend for 8 minutes.

[0058] Add glass fiber through the side feeding port, heat up to 190 °C (melting zone) and 210 °C (mixing zone), knead for 5 minutes, extrude and pelletize, and obtain composite material pellets through water-cooled pelletizing. Performance detection test

[0059] 1. Shrinkage rate difference test Specimen preparation: Use an injection molding machine to make flat specimens with dimensions of 150 mm × 150 mm × 2 mm from the composite material pellets of the examples and comparative examples. The injection molding temperature is 200 - 220 °C. Prepare 5 specimens for each group of examples and comparative examples, and place them at room temperature for 24 hours to eliminate internal stress.

[0060] Test method: Refer to ASTM D955-08 (2014) for testing. After the specimen is cooled for 24 h, measure the dimensional changes in the flow direction (L) and the perpendicular direction (T); calculate the shrinkage rate difference: shrinkage rate difference = shrinkage rate L - shrinkage rate T, and take the average value of 5 specimens.

[0061] 2. Appearance quality evaluation Specimen preparation: Inject and mold a thin-walled container simulation part (wall thickness 1 mm, dimensions 100 mm × 50 mm × 50 mm), injection molding temperature 200 - 220 °C, and prepare 3 specimens for each group.

[0062] Test method: Visually inspect whether the edges of the specimens are warped and whether there are ripples or cracks on the surface. The defect levels are classified according to the following criteria: Grade 0: No visible defects; Grade 1: Slight warping and / or slight ripple folds; Grade 2: Obvious ripples or cracks; Grade 3: Severe warping or cracks; Grade 4: Product breakage.

[0063] 3. Tensile strength test Specimen preparation: Mold the mixed PVC composition into standard 1A dumbbell specimens conforming to ISO 527-2-2012 through an injection molding machine (injection molding temperature 180 ± 5 °C, mold temperature 40 °C), and prepare 5 specimens for each group.

[0064] Test steps and conditions: Refer to ISO 527-2-2012 "Plastics - Determination of tensile properties" for testing. Use a universal material testing machine (Instron5567), tensile speed 50 mm / min, ambient temperature 23 ± 2 °C, humidity 50 ± 5%. Record the breaking strength (MPa).

[0065] 4. Notched impact strength test Sample preparation: The composite material particles of the examples and comparative examples were injection molded into 80×10×4 mm³ long strip samples by an injection molding machine (injection temperature 200 - 220 °C), and a V-notch (notch depth 2 mm, angle 45°) was cut in the middle of the samples.

[0066] Test method: Referring to ISO 179-1:2010 Plastics - Determination of Charpy impact strength, a pendulum impact testing machine was used with an impact energy of 5.5 J, a span of 62 mm, and an ambient temperature of 23 ± 2 °C. Calculate the notched impact strength (kJ / m 2 ).

[0067] 5. Antibacterial performance test Sample preparation: According to the provisions of ISO 22196-2011, the material was cut into 50 mm × 50 mm × 2 mm sheet samples and the surfaces were disinfected with ethanol.

[0068] Bacteriostatic rate test: Referring to ISO 22196-2011, Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) were inoculated with a bacterial solution concentration of 1×10 5 CFU / mL. After the samples were in contact with the bacterial solution for 24 hours, they were eluted and cultured for counting. The formula for calculating the bacteriostatic rate: Bacteriostatic rate = (number of colonies in the blank group - number of colonies in the sample group) / number of colonies in the blank group × 100%.

[0069] Long-term antibacterial performance test: The samples were immersed in a solution containing 1% detergent for 50 cycles (5 minutes each), and the bacteriostatic rate test was repeated.

[0070] Table 1. Performance test results

[0071] Analysis of test results: Example 4 (high divinylbenzene content) showed a slight increase in tensile strength but a significant decrease in notched impact strength. This indicates that an excessive amount of divinylbenzene in the stabilizer will cause deterioration of its notched impact strength.

[0072] Example 5 (low divinylbenzene content) showed a certain decrease in shrinkage difference and performances such as tensile strength and notched impact strength, indicating that the cross-linking effect of divinylbenzene has a promoting effect on suppressing shrinkage difference and enhancing strength.

[0073] In Example 6 (where methyl methacrylate replaces divinylbenzene), the shrinkage rate increases, the apparent quality decreases (there are slight corrugations on the surface and slight warping at the edges), and the tensile strength and notched impact strength decrease. The reason may be that the reaction ability of methyl acrylate with free-radicalized polypropylene is weak, which is not conducive to maintaining the stability of its molecular weight; and the crosslinking density formed as a comonomer is low, which is not conducive to suppressing anisotropic shrinkage.

[0074] In Example 7 (where methyl methacrylate replaces divinylbenzene), it performs well in terms of shrinkage rate and apparent quality, but the tensile strength and notched impact strength both decrease significantly. The reason may be that the double active sites of divinylbenzene result in strong crosslinking reaction activity. Excessive dosage will cause excessive crosslinking between the polypropylene matrix and unsaturated polyester, and the flexibility of the material will deteriorate sharply and become brittle and hard, resulting in a decrease in tensile strength and notched impact strength.

[0075] In Example 8 (where pyridine groups are not introduced into the unsaturated polyester), it performs poorly in terms of anisotropic shrinkage (apparent quality) and long-term antibacterial performance. It shows that the coordination network of pyridine groups with metal ions is beneficial to balancing anisotropic shrinkage differences and delaying the migration and precipitation rate of metal ion antibacterial agents.

[0076] In Examples 9 and 10, due to the non-use of a specific compatibilizer, their performance in terms of anisotropic shrinkage (apparent quality) and impact strength decreases, indicating that the compatibilizer obtained by reacting maleic anhydride-modified liquid polybutadiene with hydroxyacrylate has a higher interfacial strengthening effect in the polypropylene / unsaturated polyester composite system of this application, which is beneficial to the uniform dispersion of the two phases to form a micro-crosslinked network.

[0077] In Comparative Example 1 (where no stabilizer is added), it performs poorly in terms of shrinkage rate, appearance quality, and tensile strength. The reason may be that on the one hand, the absence of a stabilizer causes a significant decrease in the crosslinking activity of polypropylene and unsaturated polyester, and effective crosslinking cannot be formed. At the same time, it causes β-scission of the polypropylene main chain, excessive decrease in molecular weight, and significant loss of strength performance.

[0078] In Comparative Example 2 (where no unsaturated polyester is added), the performance in terms of anisotropic shrinkage and strength properties both decreases significantly. The reason is that polypropylene only grafts with stabilizer monomers and does not form a crosslinked structure.

[0079] Comparative Example 3 is a conventional glass fiber-reinforced polypropylene material, and its performance in terms of anisotropic shrinkage and antibacterial long-term effectiveness is inferior to that of the polypropylene material modified with pyridine-grafted unsaturated polyester in this application.

[0080] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A high-strength antibacterial polypropylene composite material, characterized in that, It comprises components in the following parts by weight: 100 parts of polypropylene, 15 - 25 parts of glass fiber, 1 - 8 parts of compatibilizer, 5 - 10 parts of unsaturated polyester, 1 - 5 parts of stabilizer, 0.1 - 0.5 part of initiator, 0.1 - 0.3 part of metal ion antibacterial agent, 0.2 - 1.5 parts of antioxidant; the stabilizer is selected from at least one of methyl methacrylate, acrylonitrile, and divinylbenzene; the melt processing temperature of the polypropylene material is 160 - 175 °C.

2. The composite material according to claim 1, wherein The stabilizer contains 30 - 50 wt% of divinylbenzene.

3. The composite material according to claim 1, characterized in that, The initiator is dicumyl peroxide.

4. The composite material according to claim 1, wherein The polypropylene is linear isotactic polypropylene, and the melt index under the condition of 230 °C / 2.16 kg is 20 - 30 g / 10 min.

5. The composite material according to claim 1, characterized in that, The unsaturated polyester is prepared by polycondensation of an unsaturated dibasic acid or anhydride, a saturated dibasic acid, pyridine-containing terephthalic acid, and a diol with a molar ratio of 0.4 - 0.5:0.4 - 0.5:0.1 - 0.2:

1.

6. The composite material according to claim 5, characterized in that, The pyridine-containing terephthalic acid is selected from 2-(4-pyridyl)terephthalic acid and / or 2,5-bis(pyridin-4-yl)terephthalic acid.

7. The composite material according to claim 1, wherein The raw materials of the compatibilizer include components in the following parts by mass: 100 parts of maleic anhydride-modified liquid polybutadiene, 10 - 30 parts of hydroxyacrylate, 0.5 - 2 parts of catalyst, and the maleic anhydride-modified liquid polybutadiene and hydroxyacrylate are subjected to an esterification reaction under the catalyst to obtain the compatibilizer.

8. The composite material according to claim 7, wherein, The hydroxyacrylate is selected from at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

9. The composite material according to claim 1, characterized in that, The glass fiber has a length of 1 - 5 mm, a length-to-diameter ratio ≥ 20, and the surface is treated with a silane coupling agent.

10. A method for preparing a high-strength antibacterial polypropylene composite material, characterized in that, It includes: Polypropylene, compatibilizer, unsaturated polyester, stabilizer, and initiator are mixed evenly and then fed into a screw extruder, and melt-blended at 160 - 175 °C for 5 - 10 minutes; then glass fiber, antioxidant, and metal ion antibacterial agent are added from the side feeding port, and continued to be kneaded at 190 - 220 °C for 3 - 6 minutes, and then extruded and pelletized to obtain the product.

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