Synthesis, structure, and property relationships in gradient polymers

Initial experiments involved modification of thin poly(vinyl chloride) films with butyl methacrylate (BMA) and styrene. Synthesis involved the immersion of the substrate films into liquid monomer for predetermined diffusion times and subsequent exposure of the samples to ionizing radiation from an electron beam source. Doses of one and ten megarads were applied to each specific sample type. The synthesis method was designed to construct composite materials with com positional gradients in their structure. Infrared analysis of the modified films indicated that little polymerization had taken place in any of the PVC/styrene systems. The PVC/BMA systems, on the other hand, were seen to contain polymerized BMA in the samples which had been exposed to ten megarads.

In a subsequent set of experiments, high density polyethylene (HOPE) films and PVC films were modified with BMA liquid monomer in a manner similar to that described, using ten megarads radiation dose in all of these experiments. The major portion of the research involved the synthesis and characterization of this set of films.

Compositional variations in the films were investigated by determining the variations in mass, density, and thickness of the samples. Infrared spectroscopy was employed to semiquantitatively determine increases in new polymer content in the modified films. Attempts were made to observe morphological features of the composite films. Optical and electron microscopy were utilized for this purpose. The important mechanical properties of the films were determined by tensile testing procedures.

The PVC/BMA systems studied showed systematic variations in composition as a function of allowed diffusion times. Mechanical property evaluations indicated that modification had produced a toughening effect in these films. The HDPE/BMA showed variations in composition as indicated by infrared analysis. Mechanical properties of these films showed little variation from sample to sample.