The main featured structure and usage of polypropylene

Polypropylene is available in a wide variety of melt flow rates, ranging from 0.3 to over 1000 g/10min., and it is easily recycled. It can be processed by virtually all methods, including injection mold-ing, blow molding, extrusion, blown and cast film, and thermoforming.Polypropylene is a versatile thermoplastic material, compatible with many processing techniquesand used in many different commercial applications. It is one of the fastest growing classesof commodity thermoplastics, with a market share growth of 6–7%/year, and the volume of polypro-pylene produced is exceeded only by polyethylene and polyvinyl chloride.

Many available grades with different properties make polypropylene useful in applications such as fibers, films, filaments, and injection molded parts for automobiles, rigid packaging, appliances, medi-cal equipment, food packaging, and consumer products. It is being substituted for glass, metal, and engineering plastics such as ABS, polycarbonate, polystyrene, and nylon in kitchen appliances and large appliances such as ovens, dishwashers, refrig-erators, and washing machines, and high flow grades are used in molding large housewares. Super-soft grades are replacing polyvinyl chloride in medical bags and tubing and in hospital gowns.

Based on its special and featured structure, isotactic polypropylene has the highest crystallinity, resulting in good mechanical properties such as stiffness and tensile strength. Syndiotactic polypropylene is less stiff than isotactic but has better impact strength and clarity. Due to its irregular structure, the atactic form has low crystallinity, resulting in a sticky, amorphous material used mainly for adhesives and roofing tars. Increasing the amount of atactic polypropylene in a predominantly isotactic formulation increases the room temperature impact resistance and stretchability but decreases the stiffness, haze, and color quality. The amount of atactic polypropylene in a polypropylene formulation is indicated by the level of room temperature xylene solubles; levels range from about 1–20%. Polypropylenes generally have higher tensile, flexural, and compressive strength,because of these advantages,usually it could be used as the material of producing PP woven bags, as well as other packaging such as the bulk bags,and so on.

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