TABLE OF CONTENTS The mechanical properties of polymeric materials depend on the type of polymer, molecular structure, molecular weight, crystallinity rate, polymer alloying, chemical additives, type and amount of colorant, impact modifier, fillers, and reinforcements. These properties also depend on the manufacturing process of the polymeric materials, testing methods, test procedures, and reporting of the property values. Because the quality of many ingredients is not consistent, the properties of polymeric materials are likely to be different. The basic polymer may be produced by a fully integrated resin supplier using high quality raw polymers. However, plastics compounders seldom use the highest quality resins; they purchase lower cost polymers from several suppliers. The resulting matrix polymers may have a wide range of variations; they could be second grade materials produced as fibers or other products such as cast film, or the materials could be recycled polymers from floor carpets, beverage bottles, or computer housings.
Most resin suppliers have their own proprietary product formulations. For example, to improve the impact strength of a product, some modify with ethylene vinyl acetate (low cost). Others alloy with acrylic polymers; other suppliers first extrude the impact modifier master batch (EPDM) rubber/copolymer through a secondary dispersion operation, then intensively mix the modifier and matrix polymer using a twin screw extruder (better impact properties, but higher manufacturing costs).
Minerals are used as fillers and reinforcements for polymeric materials. The quality of the minerals depends on the mine, processing, and equipment. For example, mica flake from Canada has the best...
