The thermal degradation of polyoxymethylene produced by the solid‐state polymerization of trioxane crystals has been studied. Changes in small‐angle and wide‐angle x‐ray patterns, weight loss, and density have been measured in specimens heated in air at 175°C, 185°C, and 195°C. The polyoxymethylene contained material in two different crystallographic orientations, which behaved differently. Material in the so‐called “twin” orientation melted preferentially at 185°C and 195°C, and at 185°C resolidified on cooling in parallel to the main orientation, in a lamellar structure. At 195°C, randomly oriented material was produced on resolidification. At 175°C, there was no evidence of melting or the formation of a lamellar structure, but the twin material was preferentially degraded so that only material in the main orientation remained after a time of 1500 min. The more rapid loss by degradation of the twin material was attributed to its having a lower molecular weight than the material in the main orientation.
Recently, in many industrial fields, there has been a drive to replace traditional metallic components with high strength polymer composites in the interest of reducing weight. Polyamide 6,6 (PA66) is a high strength thermoplastic and the behavior can be further enhanced by the addition of reinforcing fillers. Here, PA66 matrix has been reinforced with chopped glass fiber as well as hybrid composites containing both glass fiber and rubber particles. First, a baseline characterization of the mechanical properties is presented followed by a report on the thermal transitions, melting, crystallization, and glass transition, for the composite and pure materials. It is found that the filled samples show lower degree of crystallization and that the glass filled samples show lower crystallization and melting temperatures. Additionally, it was found that the glass reinforced samples led to a decrease in the glass transition temperature (Tg) while higher testing frequencies corresponded to an increase in Tg. Finally, it was demonstrated that the glass filled compounds were able to better retain their mechanical properties at high temperatures relative to the unreinforced materials. POLYM. COMPOS., 40:3960-3970, 2019.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.