The Preparation and Tensile Properties of Polyethylene Composites.

One polymer composites have been prepared using different morphologies of polyethylene as matrix and as the reinforcement. Depending on annealing conditions, the ultraoriented fibers used as reinforcement can have higher melting points approx. 139 C than the matrix made from the same conventionally-crystallized high density polyethylene approx. 132 C or from low density polyethylene approx. equal to 110 C. The optimum temperature has been assessed for bonding to occur by growth of transcrystalline regions from the melt matrix without considerable modoulus reduction of the annealed ultra-oriented and reinforcement fiber of film. Pullout tests have been used for determining the interfacial shear strength of these one polymer composites. The interfacial shear strength for the high density polyethylene films embedded in a low density polyethylene matrix is 7.5 MPa and is 17 MPa for high density polyethylene self-composites. These values are greater than the strength for glass-reinforced resins. The strength is mainly due to the unique epitaxial bonding which gives greater adhesion than the compressive and radial stresses arising from the differential shrinkage of matrix and reinforcement. The tensile modulus of composites prepared from unizxial and continuous high density polyethylene films embedded in low density polyethylene obeys the simple law of mixtures and the reinforced low density polyethylene modulus increased by a factor of ten. High strength crossply high density polyethylenelow density polyethylene laminates have also been prepared and the mechanical properties have been studied as the film orientation is varied with respect to the tensile axis. Author