The thermal behavior of eight dental acrylic resin powders was studied using differential scanning calorimetry (DSC). In addition, high performance liquid chromatography was performed to supplement the DSC analysis. The HPLC analysis revealed that the contents of residual monomers and benzoyl peroxide (BPO) in the powders were 0.01-0.97mass% and 0.25-1.28 mass%, respectively. All the resin powders produced one broad exothermic peak, while a mixture of BPO and PMMA powders generated two peaks. One peak pattern was assigned to the decomposition of BPO included within the polymer particles. The results suggested that BPO was present inside the particles and little BPO was mixed into the resin powders. Moreover, the present study demonstrated a unique useability of DSC in characterizing resin powders.
Thin films of p‐hexadecylstyrene (C16Sty) are prepared by an ion‐assisted deposition (IAD) and an electron‐assisted deposition (EAD) methods. The IAD enhances polymerization of C16Sty molecules by irradiating argon ions on the substrate surface, while the EAD initiates radical polymerization by irradiating electrons to the C16Sty vapor. The polymerization by these methods renders the films to be amorphous, whereas the conventional vapor deposition produces polycrystalline films consisting of C16Sty monomers. Upon thermal stress, the amorphous polymer films by IAD and EAD undergo morphological change at temperatures lower than that observed for the vapor‐deposited polycrystalline film. However, the polymer films retain smooth structure without coagulation upon heating. The deposited films have surface energy lower than that of polyethylene. Especially, the films deposited by EAD have a surface energy comparable to that of a normal alkane. The IAD and EAD of C16Sty are promising methods for preparing inert surfaces by dry processes.
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