Polyphosphazene Toughened PMR-type Thermosets

Two new polyphosphazenes, poly(4-maleimidophenoxy/phenoxy)phosphazene and poly(4-phthalimidophenoxy/phenoxy)phosphazene, were prepared and used to toughen a PMR polyimide designated LaRCTMRP46. These toughened polyimides were evaluated as thin films with a 0–40 wt% range of polyphosphazene to polyimide. The structure–property relationships of these inorganic/organic polymeric matrices were studied and evaluated in terms of fracture toughness, thermo-oxidative stability, and thermal, mechanical, and tensile properties. The hybrid systems revealed an increase in fracture toughness up to 20 wt% polyphosphazene load without any substantial loss in tensile properties. With 5 wt% poly(4-phthalimidophenoxy/phenoxy)phosphazene loading, the fracture toughness of the semi-interpenetrating network was increased by 124%. When 10 wt% poly(4- maleimidophenoxy/phenoxy)phosphazene loading was used, the fracture toughness of the grafted copolymer was improved by 217%. In addition, substantial enhancement in thermo-oxidative stability was also observed.

Effects of helium-neon laser irradiation on skin resistance and pain in patients with trigger points in the neck or back

The purpose of this double-blind study was to ascertain the effects of helium-neon (He-Ne) laser irradiation on skin resistance and pain in patients with trigger points in the neck or low back. This study entailed a partial replication of a previous study by Snyder-Mackler and associates that determined the use of the He-Ne laser increased skin resistance overlying a trigger point. Twenty-four patients were randomly assigned to either a treatment or a control group and received three 20-second applications of laser irradiation or placebo "stimulation," respectively. Pretreatment and posttreatment skin resistance and pain measurements (via visual analog scale) were taken during each session. Results indicated a statistically significant increase in skin resistance (p less than .001) and a decrease in pain (p less than .005) following laser treatment. There was not a significant correlation between skin resistance and pain across subjects. These data substantiate the previous findings of Snyder-Mackler and associates and demonstrate a reduction in pain. Helium-neon laser treatment, therefore, may be an effective adjunct to conventional physical therapy of these patients.