文档介绍：pp分类(PP classification)
PP homopolymer
Polypropylene (PP), a thermoplastic polymer, mercial production in 1957 and is the first of the kind of isotactic polymers. Its historical significance is that it has been the fastest growing major thermoplastic, and in 1991 the world's total output reached 24 billion pounds. It has a wide range of applications in the field of thermoplastic plastics, especially in the fiber and filament, film extrusion, injection molding processing, etc..
Chemistry and properties
PP is a anic structured catalyst (Ziegler - Natta), which can synthesize propylene monomer under controlled temperature and pressure. Due to the different catalysts and polymerization processes, the molecular structure of the polymers has three different types of stereochemistry, and the number is also different. These three structures refer to isotactic polymers, syndiotactic polymers and atactic polymers. In isotactic polypropylene (the mon form modity), the methyl group is located on the same side of the polymer skeleton, which is easy to form crystalline structure. The crystallinity of the isotactic form gives it excellent solvent resistance and thermal resistance. In the first ten years, the catalyst technology enables the production of non uniform isomers to a minimum, eliminating the need for separation of worthless ponents and simplifying the production steps.
There are two main processes for producing polypropylene: one is gas phase method, and the other is liquid propylene slurry process. In addition, there are also some old slurry process units that use a liquid saturated hydrocarbon as the reaction medium. The properties of typical isotactic polypropylene homopolymer are shown in table 1.
parison, high density and low density polyethylene both have higher density, lower melting point and lower flexural modulus, . stiffness. These performance differences lead to different end uses. Stiffness and ease of orientation make polypropylene homopolymer sui