Modified polypropylene composite material for a head and a method for producing the same

Abstract

The application relates to the technical field of high polymer materials, and discloses a modified polypropylene composite material for a sealing head and a preparation method thereof; the modified polypropylene composite material for the sealing head is composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 10-30 parts of alkali-treated bamboo fibers, 0.2-0.5 parts of graphene oxide, 5-8 parts of polypropylene grafted maleic anhydride, and 4-8 parts of modified trimer quaternary ammonium salt. The application constructs a soft fiber-hard particle system, increases the compatibility of the soft fiber, the hard particle and the organic matrix by using active polar groups, and further improves the mechanical properties of the polypropylene composite material. The antibacterial properties are improved by using the quaternary ammonium salt antibacterial structure and the graphene structure. The polypropylene composite material prepared by the application has good heat resistance, antibacterial properties and mechanical properties, and has wide use value in the field of sealing heads.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a modified polypropylene composite material for end caps and its preparation method. Background Technology

[0002] In the engineering field (especially in pressure vessel manufacturing), an end cap is a molded end cap used to seal the end of a pipe or container. Its main function is to create a closed pressure space inside the container, while effectively withstanding internal or external pressure loads. They are widely used in pressure vessels, reactors, storage tanks, heat exchangers, and other equipment in fields such as petrochemicals, food and pharmaceuticals, water treatment, environmental protection, and nuclear power. Traditional end caps are mostly made of metal materials, such as carbon steel and stainless steel, which have disadvantages such as poor corrosion resistance, heavy weight, and high cost.

[0003] Polypropylene is an inert material with excellent corrosion resistance, light weight, and easy processing and molding. However, ordinary polypropylene materials have poor temperature resistance. They will soften and deform at high temperatures and become brittle and have reduced impact resistance at low temperatures. Therefore, if traditional polypropylene materials are directly applied to the end cap field, they will soften and deform under high temperatures in summer, which may easily cause safety problems. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a modified polypropylene composite material for end caps and its preparation method, which exhibits good heat resistance, mechanical properties, and antibacterial properties.

[0006] (II) Technical Solution

[0007] A modified polypropylene composite material for end caps, wherein the modified polypropylene composite material for end caps is composed of the following raw materials in parts by weight: 100 parts polypropylene resin, 10-30 parts alkali-treated bamboo fiber, 0.2-0.5 parts graphene oxide, 5-8 parts polypropylene grafted maleic anhydride, and 4-8 parts modified trimerium ammonium salt.

[0008] As a preferred embodiment, the method for preparing the alkali-treated bamboo fiber is as follows: the bamboo fiber is washed with deionized water 4-5 times to remove water-soluble impurities on the surface, dried, and then soaked in a 0.5wt% sodium hydroxide solution for 2-4 hours with stirring. After the treatment, it is washed with deionized water and dried to obtain the alkali-treated bamboo fiber.

[0009] In this step, alkali treatment removes impurities from the surface of bamboo fibers, exposing the hydroxyl-rich fiber body and improving the chemical reactivity of the fibers. Specifically, the active hydroxyl groups of bamboo fibers enhance the hydrogen bonds formed with other polar structures in the polypropylene matrix, thereby increasing interfacial compatibility and improving the overall performance of the composite material.

[0010] As a preferred embodiment, the modified trimeric quaternary ammonium salt is prepared by:

[0011] (1) Add 4-aminobenzyl alcohol and formaldehyde to chloroform and stir for 20-30 min to disperse. Then add 4,4',4''-methylenetriphenol and reflux for 20-24 h. After the reaction is complete, cool to room temperature and wash with 0.1 mol / L sodium hydroxide aqueous solution and deionized water until pH 7. Rotary evaporate and dry to obtain the target product 1. The molar ratio of 1,4-aminobenzyl alcohol, formaldehyde and 4,4',4''-methylenetriphenol is 3-3.2:6.5-7:1. In this reaction, the phenolic hydroxyl group contained in 4,4',4''-methylenetriphenol reacts with formaldehyde and 4-aminobenzyl alcohol to react with manniene, introducing a heat-resistant benzene ring structure and a benzoxazine structure. The reaction synthesis route is as follows:

[0012] .

[0013] (2) Potassium hydroxide and target product 1 were added to deionized water and mechanically stirred at room temperature for 1-2 hours. Then epichlorohydrin was added and the reaction was continued for 20-24 hours. After the reaction was completed, deionized water was added, the mixture was extracted with ethyl acetate, the organic phase was dried, filtered, and then distilled under reduced pressure to obtain target product 2. The molar ratio of potassium hydroxide, target product 1, and epichlorohydrin was 3.2-3.5:1:3.2-3.5. In this reaction, target product 2 was synthesized from target product 1 and epichlorohydrin through an etherification reaction. The reaction synthesis route is as follows:

[0014] .

[0015] (3) Add the alkyl tertiary amine to deionized water, stir and disperse, then add a 36% hydrochloric acid aqueous solution, control the temperature at 50-70℃, acidify for 10-20 min, then add the target product 2, control the temperature at 75-85℃, stir and react for 6-8 h. After the reaction is complete, wash with deionized water and dry to obtain the modified trimeric ammonium salt. The molar ratio of alkyl tertiary amine to target product 2 is 3.2-3.5:1. In this reaction, the epoxy group contained in target product 2 is used to quaternize the alkyl tertiary amine to obtain the modified trimeric ammonium salt. That is, through this step, not only a long-chain alkyl structure is introduced, but also an antibacterial structure and an active hydroxyl structure of quaternary ammonium salt are introduced. The reaction synthesis route is as follows:

[0016] , Where R=C n H 2n+1 n=14, 16, 18.

[0017] Preferably, the alkyl tertiary amine is one of N,N-dimethyltetradecyl tertiary amine, N,N-dimethylhexadecyl tertiary amine, and N,N-dimethyloctadecyl tertiary amine. The modified trimeric quaternary ammonium salt prepared by this invention uses a long-chain tertiary amine structure and is added to a polypropylene matrix. The long-chain alkane structure therein has good compatibility with the polypropylene matrix, thereby improving the interfacial adhesion between the modified trimeric quaternary ammonium salt and the polypropylene matrix, allowing it to penetrate into the polypropylene matrix and form a tightly cross-linked network structure. When the polypropylene matrix is ​​subjected to external force, the stress can be dispersed along the tightly cross-linked network structure, thereby improving the mechanical properties of the composite material. The hydroxyl structure contained therein can be combined with maleic anhydride grafted onto polypropylene through chemical bonds and hydrogen bonds, limiting the migration of the modified trimeric quaternary ammonium salt and improving the antibacterial durability.

[0018] The preparation method of the modified polypropylene composite material for end caps of the present invention includes the following steps:

[0019] Polypropylene resin, alkali-treated bamboo fiber, graphene oxide, polypropylene grafted maleic anhydride, and modified triquaternary ammonium salt are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended using a twin-screw extruder and injection molded in an injection molding machine to obtain a modified polypropylene composite material for end caps.

[0020] In this step, a soft fiber-hard particle system is constructed using bamboo fiber and graphene oxide as raw materials. Specifically, when the material is subjected to external force, the soft fiber acts as a bridge, dispersing the stress to the hard particles, while the hard particles can bear most of the load, reducing the burden on the matrix. When the stress increases and cracks appear in the material, the soft fibers spanning both sides of the crack "bridge" the crack, applying a closing stress to the crack surface to prevent further crack propagation. This graded energy dissipation mechanism enables the polypropylene composite material to absorb far more energy than its individual components before failure. Therefore, constructing a soft fiber-hard particle system can effectively improve the mechanical properties of the material.

[0021] (iii) Beneficial technical effects

[0022] This invention uses polypropylene as the matrix and maleic anhydride grafted onto polypropylene as a compatibilizer. Alkali-treated bamboo fiber (containing hydroxyl groups on its surface) and graphene oxide (containing polar structures such as amino and carboxyl groups on its surface) form hydrogen bonds with the polar structures (such as hydroxyl and maleic anhydride structures) contained in the polypropylene grafted with maleic anhydride and modified triquaternary ammonium salt. This improves the compatibility of graphene oxide, alkali-treated bamboo fiber, and the polypropylene matrix, enhances the interfacial adhesion between fibers, particles, and resin, reduces interfacial defects, and facilitates stress transfer, thus exhibiting high-performance characteristics. Furthermore, the two-dimensional layered structure of graphene oxide can act as a barrier to prevent corrosive media from passing through the substrate, and uniformly dispersed graphene oxide reduces defects caused by resin voids compared to agglomerated graphene, improving corrosion resistance.

[0023] The polypropylene composite material prepared by this invention not only contains heat-resistant rigid benzene ring structures and benzoxazine structures (when heated, the benzoxazine structures absorb heat and open the ring to form a dense network structure), but also contains inorganic heat-resistant particles such as graphene oxide. Therefore, introducing it into the polypropylene composite material can effectively improve the heat resistance of the material.

[0024] The polypropylene composite material of the present invention has an antibacterial quaternary ammonium salt structure, which can be adsorbed onto the negatively charged cell membrane surface through electrostatic attraction, thereby destroying the bacterial cell membrane and causing the contents of the bacterial cell membrane to flow out, thus killing the bacteria; the nanosheets of graphene oxide contained therein have sharp edges, which can also destroy the cell membrane when in contact with the bacterial cell membrane, causing the contents of the cell to flow out, thus achieving the purpose of sterilization. Detailed Implementation

[0025] The technical solution and effects of the present invention will be further described below with reference to the embodiments. However, the specific methods, formulas and descriptions used are not intended to limit the present invention.

[0026] Preparation method of graphene oxide: Add 46 mL of concentrated sulfuric acid, 1 g of sodium nitrate and 2 g of graphite to a beaker, control the temperature at 10 °C, add 6 g of potassium permanganate and react for 2 h, raise the temperature to 35 °C and react for 2 h, add 96 mL of deionized water, raise the temperature to 95 °C and react for 30 min, then add 30% hydrogen peroxide until the solution turns bright yellow, filter, wash with deionized water until neutral, centrifuge and dry to obtain graphene oxide.

[0027] Example 1

[0028] (1) 20g of bamboo fiber was washed 5 times with deionized water to remove water-soluble impurities on the surface, dried, and then soaked in a 0.5wt% sodium hydroxide solution for 3 hours with stirring. After the treatment, it was washed with deionized water and dried to obtain alkali-treated bamboo fiber.

[0029] (2) 0.3 mol of 4-aminobenzyl alcohol and 0.65 mol of formaldehyde were added to chloroform and stirred for 30 min to disperse. Then 0.1 mol of 4,4',4''-methylenetriphenol was added and the mixture was heated to reflux for 24 h. After the reaction was completed, the mixture was cooled to room temperature and washed with 0.1 mol / L sodium hydroxide aqueous solution and deionized water until the pH was 7. The mixture was then rotary evaporated and dried to obtain the target product 1.

[0030] (3) Add 0.27 mol of potassium hydroxide and 0.08 mol of target product 1 to deionized water, stir mechanically at room temperature for 2 h, then add 0.26 mol of epichlorohydrin, continue stirring for 20 h, after the reaction is complete, add deionized water, extract with ethyl acetate, dry the organic phase, filter, distill under reduced pressure, and dry to obtain target product 2.

[0031] (4) Add 0.16 mol of N,N-dimethylhexadecyl tertiary amine to deionized water, stir and disperse, then add 36% hydrochloric acid aqueous solution, control the temperature at 70℃, acidify for 10 min, then add 0.05 mol of target product 2, control the temperature at 75℃, stir and react for 8 h, after the reaction is completed, wash with deionized water and dry to obtain modified triquaternary ammonium salt.

[0032] (5) By weight, 100 parts of polypropylene resin, 10 parts of alkali-treated bamboo fiber, 0.2 parts of graphene oxide, 5 parts of polypropylene grafted maleic anhydride, and 4 parts of modified triquaternary ammonium salt are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended using a twin-screw extruder with temperatures of 170°C, 180°C, and 175°C in each zone and a screw speed of 100 r / min. The mixture is then injection molded in an injection molding machine with an injection temperature of 180°C to obtain a modified polypropylene composite material for end caps.

[0033] Example 2

[0034] (1) 20g of bamboo fiber was washed 4 times with deionized water to remove water-soluble impurities on the surface, dried, and then soaked in a 0.5wt% sodium hydroxide solution for 4 hours with stirring. After the treatment, it was washed with deionized water and dried to obtain alkali-treated bamboo fiber.

[0035] (2) 0.32 mol of 4-aminobenzyl alcohol and 0.7 mol of formaldehyde were added to chloroform and stirred for 20 min to disperse. Then 0.1 mol of 4,4',4''-methylenetriphenol was added and the mixture was heated to reflux for 20 h. After the reaction was completed, the mixture was cooled to room temperature and washed with 0.1 mol / L sodium hydroxide aqueous solution and deionized water until the pH was 7. The mixture was then rotary evaporated and dried to obtain the target product 1.

[0036] (3) Add 0.28 mol of potassium hydroxide and 0.08 mol of target product 1 to deionized water, stir mechanically at room temperature for 1 h, then add 0.28 mol of epichlorohydrin, continue stirring for 22 h, after the reaction is complete, add deionized water, extract with ethyl acetate, dry the organic phase, filter, distill under reduced pressure, and dry to obtain target product 2.

[0037] (4) Add 0.175 mol of N,N-dimethyltetradecyl tertiary amine to deionized water, stir and disperse, then add 36% hydrochloric acid aqueous solution, control the temperature at 50℃, acidify for 20 min, then add 0.05 mol of target product 2, control the temperature at 80℃, stir and react for 6 h, after the reaction is completed, wash with deionized water and dry to obtain modified trimeric quaternary ammonium salt.

[0038] (5) By weight, 100 parts of polypropylene resin, 20 parts of alkali-treated bamboo fiber, 0.3 parts of graphene oxide, 7 parts of polypropylene grafted maleic anhydride, and 6 parts of modified triquaternary ammonium salt are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended using a twin-screw extruder with temperatures of 170°C, 180°C, and 175°C in each zone and a screw speed of 100 r / min. The mixture is then injection molded in an injection molding machine with an injection temperature of 180°C to obtain a modified polypropylene composite material for end caps.

[0039] Example 3

[0040] (1) 20g of bamboo fiber was washed 5 times with deionized water to remove water-soluble impurities on the surface, dried, and then soaked in a 0.5wt% sodium hydroxide solution for 2 hours with stirring. After the treatment, it was washed with deionized water and dried to obtain alkali-treated bamboo fiber.

[0041] (2) 0.32 mol of 4-aminobenzyl alcohol and 0.68 mol of formaldehyde were added to chloroform and stirred for 25 min to disperse. Then 0.1 mol of 4,4',4''-methylenetriphenol was added and the mixture was heated to reflux for 24 h. After the reaction was completed, the mixture was cooled to room temperature and washed with 0.1 mol / L sodium hydroxide aqueous solution and deionized water until the pH was 7. The mixture was then rotary evaporated and dried to obtain the target product 1.

[0042] (3) Add 0.256 mol of potassium hydroxide and 0.08 mol of target product 1 to deionized water, stir mechanically at room temperature for 2 h, then add 0.256 mol of epichlorohydrin, continue stirring for 20 h, after the reaction is complete, add deionized water, extract with ethyl acetate, dry the organic phase, filter, distill under reduced pressure, and dry to obtain target product 2.

[0043] (4) Add 0.17 mol of N,N-dimethyloctadecyl tertiary amine to deionized water, stir and disperse, then add 36% hydrochloric acid aqueous solution, control the temperature at 60℃, acidify for 20 min, then add 0.05 mol of target product 2, control the temperature at 85℃, stir and react for 8 h, after the reaction is completed, wash with deionized water and dry to obtain modified trimeric quaternary ammonium salt.

[0044] (5) By weight, 100 parts of polypropylene resin, 30 parts of alkali-treated bamboo fiber, 0.5 parts of graphene oxide, 8 parts of polypropylene grafted maleic anhydride, and 8 parts of modified triquaternary ammonium salt are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended using a twin-screw extruder with temperatures of 170°C, 180°C, and 175°C in each zone and a screw speed of 100 r / min. The mixture is then injection molded in an injection molding machine with an injection temperature of 180°C to obtain a modified polypropylene composite material for end caps.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that in step (5), untreated bamboo fiber is used instead of alkali-treated bamboo fiber.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Example 1 is that step (5) does not contain modified triquaternary ammonium salt.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that step (5) does not contain graphene oxide.

[0051] Tensile strength was tested using a universal testing machine.

[0052] The notched impact strength is tested using an impact testing machine.

[0053] Table 1:

[0054] Tensile strength / MPa <![CDATA[Notched impact strength / (kJ·m -2 )]]> Example 1 48.9 7.5 Example 2 51.3 8.1 Example 3 53.7 8.4 Comparative Example 1 42.4 5.4 Comparative Example 2 45.6 6.8

[0055] As shown in Table 1, the mechanical properties of Comparative Examples 1-2 are inferior to those of the Example. This is because the bamboo fiber used in Comparative Example 1 is untreated bamboo fiber, and its surface contains other impurities, resulting in poor interfacial compatibility with the polypropylene matrix. The interfacial bonding strength affects the load transfer efficiency between the fiber and the matrix. When the interfacial bonding is weak, stress concentration and microcracks are easily generated at the interface of the composite material under external force, affecting the overall performance of the composite material. Therefore, the mechanical properties of Comparative Example 1 are inferior to those of the Example. Comparative Example 2 does not contain modified triquaternary ammonium salt. Firstly, modified triquaternary ammonium salt can increase the compatibility of alkali-treated bamboo fiber and graphene oxide with the matrix, thereby increasing the overall performance of the matrix material. Secondly, the alkyl long chains and polar structures contained in the modified triquaternary ammonium salt can form a large and dense cross-linked network structure with the matrix. This network structure can improve the mechanical properties of the material. However, Comparative Example 2 does not contain modified triquaternary ammonium salt, therefore its mechanical properties are inferior to those of the Example.

[0056] The Vicat softening temperature was tested using a Vicat softening point tester.

[0057] The antibacterial properties were tested according to GB / T31402-2015, and the test strain was Escherichia coli.

[0058] Table 2:

[0059] Vicat softening temperature / °C Antibacterial rate / % Example 1 154.7 90.3 Example 2 155.8 97.6 Example 3 156.3 99.9 Comparative Example 2 151.6 58.7 Comparative Example 3 152.4 76.2

[0060] The higher the Vicat softening temperature, the better the heat resistance. As shown in Table 2, the heat resistance of the examples containing both graphene oxide and modified triquaternary ammonium salt is better than that of the comparative examples containing only graphene oxide or modified triquaternary ammonium salt. This is because the heat-resistant structures (benzene ring structure and benzoxazine structure) contained in graphene oxide and modified triquaternary ammonium salt can synergistically improve the heat resistance.

[0061] As shown in Table 2, the polypropylene composite material prepared by this invention has good antibacterial properties, with an antibacterial rate of up to 99.9%.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified polypropylene composite material for end caps, characterized in that, The modified polypropylene composite material for the end cap is composed of the following raw materials in parts by weight: 100 parts polypropylene resin, 10-30 parts alkali-treated bamboo fiber, 0.2-0.5 parts graphene oxide, 5-8 parts polypropylene grafted maleic anhydride, and 4-8 parts modified triquaternary ammonium salt. The structural formula of the modified trimeric quaternary ammonium salt is: ， in ; The preparation method of the modified trimeric quaternary ammonium salt is as follows: (1) Add 4-aminobenzyl alcohol and formaldehyde to chloroform and stir for 20-30 min to disperse. Then add 4,4',4''-methylenetriphenol and reflux for 20-24 h. After the reaction is complete, cool to room temperature and wash with 0.1 mol / L sodium hydroxide aqueous solution and deionized water until pH is 7. Rotary evaporate and dry to obtain target product 1. (2) Add potassium hydroxide and target product 1 to deionized water and stir mechanically at room temperature for 1-2 hours. Then add epichlorohydrin and continue stirring for 20-24 hours. After the reaction is complete, add deionized water, extract with ethyl acetate, dry the organic phase, filter, distill under reduced pressure, and dry to obtain target product 2. (3) Add the alkyl tertiary amine to deionized water, stir and disperse, then add 36% hydrochloric acid aqueous solution, control the temperature at 50-70℃, acidify for 10-20 min, then add target product 2, control the temperature at 75-85℃, stir and react for 6-8 h, after the reaction is completed, wash with deionized water and dry to obtain modified trimeric quaternary ammonium salt.

2. The modified polypropylene composite material for end caps according to claim 1, characterized in that, The method for preparing alkali-treated bamboo fiber is as follows: the bamboo fiber is washed with deionized water 4-5 times to remove water-soluble impurities on the surface, dried, and then soaked in a 0.5wt% sodium hydroxide solution for 2-4 hours with stirring. After the treatment, it is washed with deionized water and dried to obtain alkali-treated bamboo fiber.

3. The modified polypropylene composite material for end caps according to claim 1, characterized in that, In (1), the molar ratio of 4-aminobenzyl alcohol, formaldehyde, and 4,4',4''-methylenetriphenol is 3-3.2:6.5-7:

1.

4. The modified polypropylene composite material for end caps according to claim 1, characterized in that, In step (2), the molar ratio of potassium hydroxide, target product 1, and epichlorohydrin is 3.2-3.5:1:3.2-3.

5.

5. The modified polypropylene composite material for end caps according to claim 1, characterized in that, In step (3), the molar ratio of alkyl tertiary amine to target product 2 is 3.2-3.5:

1.

6. The modified polypropylene composite material for end caps according to claim 1, characterized in that, In (3), the alkyl tertiary amine is one of N,N-dimethyltetradecyl tertiary amine, N,N-dimethylhexadecyl tertiary amine, and N,N-dimethyloctadecyl tertiary amine.

7. The method for preparing the modified polypropylene composite material for end caps according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: Polypropylene resin, alkali-treated bamboo fiber, graphene oxide, polypropylene grafted maleic anhydride, and modified triquaternary ammonium salt are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended using a twin-screw extruder and injection molded in an injection molding machine to obtain a modified polypropylene composite material for end caps.

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