The effects of molecular structure on the dicumyl peroxide crosslinking of two low density polyethylenes have been studied. Peroxide efficiency was determined largely by the content of terminal vinyls in the two polymers. Differences in molecular weight distribution and branch content had comparatively little influence on the gel content but hot creep resistance of the vulcanized materials was affected. Scorching was affected, also, by the presence of vinyl unsaturations in the polymer.

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Neutron activation analysis and secondary ion mass spectrometry were used to measure gallium profiles resulting from the diffusion of Ga into intrinsic silicon. The diffusion of the impurity was measured between 700 and 1100 °C. The diffusion coefficient in this wide temperature range follows the expression D=0.005 exp[−(2.70/kT)] cm2 sec−1. The possible intervention of surface effects in the diffusion kinetics is discussed. An estimate of the enthalpy of association of Ga vacancy is deduced. The solid solubility of gallium in silicon was measured in the same range and at various concentrations of donors and acceptors.

The surfaces of three polyolefin films, low-density polyethylene, high-density polyethylene, and polypropylene, were chemically modified by etching with permanganic acid, and low-density polyethylene by etching with chromic acid and by staining with chlorosulphonic acid. Polytetrafluoroethylene (Teflon) was treated with a sodium naphthalene complex in glycol ether. The surfaces were examined with a scanning electron microscope, and chemical groups identified by attenuated total reflectance infrared measurements. The surfaces were then corona charged, and the charge stability and trap distributions determined by the methods of thermally stimulated charge decay and thermally stimulated current, respectively. Scanning electron micrographs revealed a nodular surface structure in polyolefins etched with permanganic acid, a rough surface without nodules in low-density polyethylene etched with chromic acid, isolated corroded surface spots in low-density polyethylene stained with chlorosulphonic acid, and a web-like surface in etched Teflon. Permanganic acid removed amorphous and defective regions of the polymer surfaces, exposing more crystalline regions and crystalline-amorphous boundaries, both of which provided trapping sites, producing better charge storers than the virgin equivalents. Lifetimes, and hence usable temperatures in device application, were increased for both negative and positive charge. The other acids reduced the lifetimes in low-density polyethylene. Etching made Teflon as good a positive charge storer as the virgin negatively charged material, a result important to practical applications. While attenuated total reflectance measurements showed the presence of various chemical groups, charge stability seemed to depend more on surface morphology than on which active groups were added to the polymers by the etchants and staining agent.

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