Polypropylene thermoplatsic resins are produced from propylene gas, a by-product of petroleum refining. The natural resin is semitranslucent and milky white in color and has excellent colorability.
Most propylene parts are produced by injection molding, blow-molding, or extrusion of either unmodified or reinforced compounds. Other applicable processes for polypropylenes are structural- foam molding and solid phase and hot flow stamping of glass reinforced sheet stock. Molding and extruding resins can be pigmented by any conventional method.
Polypropylene is a low-density resin that offers a good balance of thermal, chemical, and electrical properties, along with moderate strength. Strength properties are increased significantly with glass fibre reinforcement. Increased toughness is provided in special, high-molecular weight, rubber modified grades.
Electrical properties of polypropylene are affected to varying degrees of service temperature. Dielectric constant is essentially unchanged, but dielectric strength increases and volume resistivity decreases with increased temperature.
Polypropylene has limited heat resistance, but heat-stabilized grades are available for applications requiring prolonged use at elevated temperatures. Useful life or parts molded from such grades may be as long as five years at 250 degrees F, ten years at 230 degrees F, or for 20 years at 210 degrees F.
Polypropylene resins are inherently unstable in the presence of oxidated conditions with UV radiation. While all grades are stabilized to some extent, specific stabilization systems are often used to suit formulation for a particular environment. Polypropylenes resist chemical attack and staining and are unaffected by aqueous solutions of inorganic salts or mineral acids and gases, even at high temperatures. They are not attacked by most organic chemicals, and there is no solvent for the resin at room temperature. The resins are attacked, however, by halogens, fuming nitric acid and other active oxidizing agents, and by aromatic and chlorinated hydrocarbons at high temperatures.
Unreinforced polypropylene is used for packaging applications such as blow-molded pharmaceutical, medical, cosmetic, and food containers. Structural-foam grades are used for furniture and for automotive seatbacks.
Both reinforced and unreinforced grades are used in automotive, appliance, and electrical applications. Examples are:
Automotive Battery
Cases
Fan Blades
Lamp Housings
Vegetable Bins
Blower Wheels Sole support for:
Fan Shrouds
Current-carrying Electrical Parts
Fender Liners
Coil Bobbins
Glove Boxes
Cable Covers
Appliance Pumps
TV Yokes and Insulators
Blower Housings
