Impact Plastics has refined the art and technology of olefin extrusion to provide our customers with a high efficiency, precision gauge extruded polypropylene sheet designed to optimize thermoforming processes for critical applications.
Polypropylene (PP) is a semi-crystalline polymer that is hazy in its natural state. This material is generally characterized as having a higher stiffness at a lower density, resistance to higher temperatures, and an excellent strength to weight ratio. There are three main grades of PP resin which allow for improvement of specific properties as determined by the composition of the polymer chain.
Homopolymer PP can be considered the most ‘basic’ grade of PP resin. This grade of PP resin is more rigid and has good resistance to high temperatures, making it particularly suitable for high-heat applications such as hot fill and microwave applications or steam sterilization applications. However, the tradeoff to this is lower impact resistance, particularly at low temperatures.
Additional characteristics of this grade of PP resin include a high melting point leading to excellent stiffness, superior scratch resistance, and good chemical resistance against most inorganic acids, alkalis and salts. In addition, this grade of PP resin provides strong resistance to environmental stress cracking when in contact with alcohols, esters, detergents or polar hydrocarbons.
Clarified Grades of homopolymer PP are available from Impact Plastics.
Random Copolymer PP
Random copolymer PP resins are created by modifying the PP polymer chain through the addition of random chains of ethylene among the PP units. Due to the presence of ethylene, the rigidity characteristic of homopolymer resins is somewhat sacrificed, however, this results in improved impact strength and a softer feel. Additional benefits to this include improved heat sealability, lower melting point, resistance to envitonmental stress cracking and improved clarity. Random Copolymer PP resins also exhibit good chemical resistance against most inorganic acids, alkalis and salts. Clarified grades of random copolymer PP are available from Impact Plastics.
Block Copolymer PP
Similar to random copolymers, block (or impact) copolymer PP resins are derived through copolymerization with ethylene, but with this grade the ethylene content is much higher. This results in a much tougher material with excellent impact strength even at low temperatures. For this reason, block copolymer PP resins are particularly suitable for freezer and freezer-to-microwave applications. This comes with a tradeoff on transparency as traditional block copolymers cannot be clarified, even through the use of additives
With continued advancements in technology, both on the resin production side and the extrusion side, traditional differences in the primary grades of PP resin have blurred. Custom grades polypropylene and specialty formulations are available from Impact Plastics upon request. Impact Plastics recommends testing of the material for every new application and custom tailors PP formulations to meet the customers ultimate goals for their project.
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