SYNOPSISHigh-density polyethylene (HDPE) was compounded with untreated and surface-treated mica (10,20,40 wt %) and composites were injection-molded. The composites were radiation crosslinked (100, 300, 700 kGy) and hydrocarbon permeability, tensile impact strength, and tensile strength at 25 and 80°C of the composites were examined. The permeability of HDPE decreased from 7 to 3.6 g/(d X m2) by compounding the polymer with 20 wt % mica, and the permeability was additionally reduced to 1.3 g/(d X m2) by irradiation of the compounds (700 kGy). When surface-treated mica was used, the permeability of the composite furthermore decreased to about 1.0 g/(d X m'). Upon irradiation, the E modulus measured at 25°C increased 5% when the dose was 300 kGy. At 8OoC, the corresponding increase was 40%. The tensile impact strength of an unfilled polymer increased more than three times by an irradiation dose of 700 kGy, and for a polymer with 10 wt % mica, the tensile impact strength was twice the level of an unirradiated composite. 0 1996 John Wiley & Sons, Inc.

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This publication is based on research work done on functional phenolmodified polypropylenes (PPs) as adhesion promoters in glass fiber-reinforced PP composites. The glass fiber roving was first impregnated with different combinations of functional polymers and polypropylene in a melt impregnation die attached to an extruder to obtain prepreg. The prepreg was then tested in many ways both macro-and micromechanically. The tests included notched tensile tests, optical and electron microscopy, and DMTA (dynamic mechanical thermal analyzer) and DSC (differential scanning calorimetry) analyses as well as determination of the glass content. The tests were run on prepregs containing pure PP, PP with a commercial adhesion promoter, and PP with a number of functional, mostly phenol-based, polymers. Also, single-fiber tests were performed on individual glass fibers to test the level of adhesion with the above-mentioned material combinations. With these tests it could be seen that some of the phenol-based functional polymers provided the prepreg with better adhesion between the fibers and the matrix than did the commercial adhesion promoter. Optical and electron microscopy also were used in determining the level of adhesion as well as the deformation and fracture mechanisms of the prepreg.

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