Polypropylene modified

In view of the poor impact resistance of polypropylene at low temperatures, poor weather resistance, poor surface decoration, and the gap between its functionality and actual needs in terms of electricity, magnetism, light, heat, combustion, etc., polypropylene was modified to become At present, plastic processing is the most active area of development and has achieved the most fruitful results.
PP chemical modification
Through copolymerization modification, cross-linking modification, graft modification, adding nucleating agents, etc., the polymer components and macromolecular structure or crystal configuration of polypropylene are changed to improve its mechanical properties, heat resistance, and aging resistance. and other properties, improve its comprehensive performance and expand its application fields.
(1) Copolymerization modification
Copolymerization modification is a modification carried out in the propylene monomer synthesis stage using catalysts such as metallocenes. When the monomers are polymerized, the added olefin monomers are copolymerized with them to obtain random copolymers, block copolymers, alternating copolymers, etc. The mechanical properties, transparency and processing fluidity of homopolymer PP are improved. . The complex formed by the metallocene catalyst uses a transition state with an irregular shape and certain restrictions as a single active center to achieve precise control of the relative molecular weight and distribution, comonomer content, distribution on the main chain and polymer crystal form. structure.
(2) Graft modification
PP (polypropylene) resin molecules have a non-polar crystalline linear structure, low surface activity and non-polarity. There are shortcomings such as poor surface printability, poor coating adhesion, difficulty in blending with polar polymers, and difficulty in compatibility with polar reinforcing fibers and fillers. Graft modification is to introduce polar groups into its macromolecular chain to improve the blending, compatibility and adhesion of PP and overcome the shortcomings of difficulty in blending, compatibility and adhesion. Under the action of the initiator, the grafting monomer undergoes a grafting reaction during melting and mixing. The initiator decomposes to generate active free radicals when heated, melted, and heated. When the active free radicals encounter the unsaturated carboxylic acid monomer, the unsaturated carboxylic acid monomer is After the unstable bond of the acid monomer is opened, it reacts with the active free radicals of PP to form graft free radicals, which are subsequently terminated through a molecular chain transfer reaction. Common graft modification methods of PP include: melt method, solution method, solid phase method, suspension method, etc. The hydrogen atoms in the graft-modified PP molecular chain are replaced and become more polar. These polar groups enhance the compatibility of PP and greatly improve its heat resistance and mechanical properties.
(3) Cross-linking modification
Cross-linking modification mainly involves modifying linear or dendritic polymers into polymers with a network structure through cross-linking. Cross-linking modification of PP (polypropylene) can improve its mechanical properties, heat resistance and morphological stability, and shorten the molding cycle. The main methods of cross-linking modification of polypropylene include chemical cross-linking modification and radiation cross-linking modification. The main differences between them are different cross-linking mechanisms and different active sources; chemical cross-linking modification is achieved by adding cross-linking auxiliaries to polypropylene. Modification, radiation cross-linking modification is mainly achieved through strong radiation or strong light. Due to the requirements on the thickness of PP for radiation cross-linking modification, it is difficult to popularize this method. At present, the silane graft cross-linking method is developing rapidly because it can produce materials with excellent properties. The PP produced by the silane graft cross-linking method has high strength, good heat resistance, high melt strength, strong chemical stability, and corrosion resistance. good.
PP physical modification
During the mixing and kneading process, organic or inorganic additives are added to the PP (polypropylene) matrix to obtain PP composite materials with excellent performance, which mainly include: filling modification, blending modification, etc.