Polypropylene general

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

Polypropylene made by free-radical polymerization is generally atactic , that is to say, there is no pattern to the stereochemistry. On the other hand, both isotactic polypropylene (in which all the stereocenters are the same) and syndiotactic polypropylene (in which the stereocenters alternate) may be made via the Ziegler-Natta process (see Chapter 18, Problem 4). Experimentally, both isotactic and syndiotactic polypropylene generally have higher melting points than atactic polypropylene. 

Hypol A process for making polypropylene, generally similar to Spheripol. Developed by Mitsui Petrochemical Company, Japan. 

Hypol [Hyosung polypropylene] Also Hypol II. A process for making polypropylene, generally similar to Spheripol. Developed by Mitsui Petrochemical Company, Japan, and Hyosung Corporation, a South Korean conglomerate. 

One of the shortcomings most adversely affecting the utilization of PP filled with flame retardant magnesium hydroxide (Mg(OH)2) is the steep reduction of subambient fracture toughness compared with that of neat polypropylene. Generally, an increase in the resistance to crack initiation and growth can be achieved... 

Unfilled polypropylene generally is not recommended for use in load-bearing applications, because the plastic creeps rapidly even under moderate stresses. Glass-reinforced grades, however, can be used in high-load applications. Polypropylene also has good unnotched and excellent notched impact strength. Polypropylene s heat resistance is much superior to that of polyethylene. 

Nylon General purpose molding Standard Epoxies Cast rigid Polypropylene General purpose Polypropylene High impact 0.3—0.5 0.4-0.5 0.45 0.45—0.48... 

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