Microlayer coextrusion of foam & film.Flat-die co-extrusion of polyolefin foam sheet reportedly can down-gauge without sacrificing tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its or adding density by alternating microlayers of foam and solid film. The material is said to resemble cork cork, in botany cork, protective, waterproof outer covering of the stems and roots of woody plants. Cork is a specialized secondary tissue produced by the cork cambium of the plant (see meristem, bark). in compressive strength Compressive strength is the capacity of a material to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g. and could theoretically make stiff foams for thermoforming or soft foams for fabric replacement. This development was first reported at the 2004 SPE SPE - Software Practice and Experience ANTEC meeting by researchers from Dow Chemical Co., Midland, Mich., and Case Western Reserve University, Cleveland. They used a feedblock and a series of layer multipliers to make 32- and 64-layer sheet of foam/solid PP. Foams were blown with azodicarbonamide (1.25% to 1.75%) and a nucleating agent (1% MgO). Cell sizes ranged from 10 to 100 microns (more layers yield smaller cells). Dow will give a second paper at next month's ANTEC in Charlotte, N.C., describing new material combinations, such as foam/solid PE and PP foam with solid PE. Case Western's lab can now extrude extrude /ex·trude/ (ek-strldbomacd´) 1. to force out, or to occupy a position distal to that normally occupied. 2. in dentistry, to occupy a position occlusal to that normally occupied. such structures in tapes up to 2 in. wide and 4 mm thick. Dow: (989) 636-3315 * PT Direct: 796ZR [ILLUSTRATION OMITTED] |
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