By copolymerization modification, cross-linking modification, graft modification, addition of nucleating agent, etc., the PP (polypropylene) polymer component and macromolecular structure or crystal configuration are changed to improve its mechanical properties, heat resistance, Performance such as aging resistance improves its overall performance and expands its application areas. [11]
(1) Copolymerization modification
The copolymerization modification is a modification carried out in a synthesis stage of a propylene monomer using a catalyst such as a metallocene. When the monomer is polymerized, the added olefin monomer is copolymerized with it to obtain a random copolymer, a block copolymer and an alternating copolymer, etc., and the mechanical properties, transparency and processing fluidity of the homopolymer PP are improved. . The complex formed by the metallocene catalyst is a single active center in a transition state in which the irregular shape is restricted, to precisely control the relative molecular mass and its distribution, the comonomer content, the distribution on the main chain, and the high polymer crystal form. structure.
Cross-linking modification
Cross-linking modification is mainly to modify a linear or dendritic polymer into a network of polymers by cross-linking. PP (polypropylene) cross-linking modification can improve the mechanical properties, heat resistance and morphological stability, and shorten the molding cycle. The main methods of polypropylene cross-linking modification include chemical cross-linking modification and radiation cross-linking modification. The main difference is that the cross-linking mechanism is different and the active source is different. Chemical cross-linking modification is to realize polypropylene by adding cross-linking aid. Modification, radiation crosslinking modification is mainly achieved by strong radiation or strong light, which is difficult to popularize due to the requirement of PP cross-linking modification for PP thickness. At present, the silane graft crosslinking method is rapidly developed due to its ability to prepare materials with excellent properties. The PP produced by the silane graft crosslinking method has high strength, good heat resistance, high melt strength, strong chemical stability and corrosion resistance. it is good. [11]
PP physical modification
In the mixing and kneading process, an organic or inorganic auxiliary agent is added to a PP (polypropylene) matrix to obtain a PP composite material having excellent properties, mainly including: filling modification, blending modification, and the like. [11]
