Abstract: Exploratory experiments on irradiation of mixtures of polyethylene and organo-montmorillonites with gamma rays indicated that the polyethylene became crosslinked to the organoclays. Subsequently, 264 samples of 1:1 clay-polyethylene compositions were irradiated with 2 MeV electrons and tested for tensile strength and weight fraction extractable in toluene at 110°C. From statistical analysis of the variables of clay lattice, clay surface, polyethylene type and radiation dose it is concluded that: (1) polyethylene can be bonded directly to the clay surface by ionizing radiation, and (2) at least one organoclay bearing a “polyethylenelike” chain, polyvinyl alcohol, is more effective than wholly inorganic clay for the purpose of radiatively linking polyethylene to clay surface. The data below show the markedly increased solvent resistance of polyethylene radiatively bonded to clay over that of equivalently irradiated pure polyethylene.
Clay Clay surface Type of polyethylene Electron dose, Mrad Weight % of sample not dissolved* (Pure polyethylene) None Linear 55 12.8 Montmorillonite 4-Vinyl pyridinium Linear 55 94.8 (Pure polyethylene) None Linear 100 24.4 Montmorillonite Hexamethylene-diammonium Linear 100 96.6 Montmorillonite Polyvinyl alcohol Linear 100 98.2 (Pure polyethylene) None Branched 100 37.4 Kaolinite Proton Branched 100 97.1 Montmorillonite Polyvinyl alcohol Branched 100 99.2 * After 7 weeks.