Gregory Von White Ii

Parylene C Aging Studies

Parylene C is used in a device because of its conformable deposition and other advantages. Techniques to study Parylene C aging were developed, and %22lessons learned%22 that could be utilized for future studies are the result of this initial study. Differential Scanning Calorimetry yielded temperature ranges for Parylene C aging as well as post-deposition treatment. Post-deposition techniques are suggested to improve Parylene C performance. Sample preparation was critical to aging regimen. Short-term (~40 days) aging experiments with free standing and ceramic-supported Parylene C films highlighted %22lessons learned%22 which stressed further investigations in order to refine sample preparation (film thickness, single sided uniform coating, machine versus laser cutting, annealing time, temperature) and testing issues (%22necking%22) for robust accelerated aging of Parylene C.

Shelf Life Assessment of Poly(ethylene-co-vinyl acetate) and Polyester Polyol Resins Used as Adhesives

The thermal stability and ageing properties of Vinamul 3161 poly(ethylene-co-vinyl acetate) and AS1160 polyester polyol resins have been investigated in support of shelf life assessment and also to identify storage conditions that may extend product life. These resins are typically used in the production of adhesives for specialised applications either as binders for filler particles or to minimise the relative movement of materials in multi-material assemblies. Our studies confirm that both these resins are susceptible to moisture and hydrolysis chemistry which potentially limits shelf life. The EVA resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which increases both the acidity (pH) and volatile outgassing characteristics of the material. The temperature sensitivity of pH combined with Arrhenius kinetics was used to identify a useful shelf life for EVA in conditions representative of normal storage conditions. In a separate set of experiments, relatively short-term thermally accelerated ageing studies have been carried out on AS1160 polyester polyol to investigate sensitivity to humidity, temperature and open/close ageing conditions. This material is hygroscopic, readily accumulates moisture and is susceptible to chain scission with molecular weight changes linked to the hydrolysis-esterification equilibrium. These changes do not however adversely impact adhesive bond strength allowing the resin to be potentially used significantly beyond the manufacturer recommended shelf life limit.

Multi-Method Characterization of Compression Set in Fluorosilicone O-Rings

Fluorosilicone o-rings with varying levels of compression set were investigated with a variety of methods. Low field NMR experiments were able to elucidate if the sample had taken a compression set; however, this technique did not have the sensitivity to quantify the relative level of compression set of the o-ring. Water sorption isotherms probe the interior void structure through void space occupation and while complex, the sorption isotherms indicate a systematic loss of void volume with increasing compression set. Similarly, variable temperature 129Xe NMR experiments indicate an elimination of macroscopic void space with increasing compression. The NMR techniques, being noninvasive, have a unique ability to assess the service status of an o-ring in real time.

Neutron and gamma irradiation damage to organic materials.

This document discusses open literature reports which investigate the damage effects of neutron and gamma irradiation on polymers and/or epoxies - damage refers to reduced physical chemical, and electrical properties. Based on the literature, correlations are made for an SNL developed epoxy (Epon 828-1031/DDS) with an expected total fast-neutron fluence of {approx}10{sup 12} n/cm{sup 2} and a {gamma} dosage of {approx}500 Gy received over {approx}30 years at < 200 C. In short, there are no gamma and neutron irradiation concerns for Epon 828-1031/DDS. To enhance the fidelity of our hypotheses, in regards to radiation damage, we propose future work consisting of simultaneous thermal/irradiation (neutron and gamma) experiments that will help elucidate any damage concerns at these specified environmental conditions.