Meng Frank H, Schricker Scott R, Brantley William A, Mendel Deborah A, Rashid Robert G, Fields Henry W, Vig Katherine W L, Alapati Satish B
Section of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH 43218, USA.
Dent Mater. 2007 Dec;23(12):1492-9. doi: 10.1016/j.dental.2007.01.006. Epub 2007 Apr 6.
Employ differential scanning calorimetry (DSC) and temperature-modulated DSC (TMDSC) to investigate thermal transformations in three mouthguard materials and provide insight into their previously investigated energy absorption.
Samples (13-21mg) were obtained from (a) conventional ethylene vinyl acetate (EVA), (b) Pro-form, another EVA polymer, and (c) PolyShok, an EVA polymer containing polyurethane. Conventional DSC (n=5) was first performed from -80 to 150 degrees C at a heating rate of 10 degrees C/min to determine the temperature range for structural transformations. Subsequently, TMDSC (n=5) was performed from -20 to 150 degrees C at a heating rate of 1 degrees C/min. Onset and peak temperatures were compared using ANOVA and the Tukey-Kramer HSD test. Other samples were coated with a gold-palladium film and examined with an SEM.
DSC and TMDSC curves were similar for both conventional EVA and Pro-form, showing two endothermic peaks suggestive of melting processes, with crystallization after the higher-temperature peak. Evidence for crystallization and the second endothermic peak were much less prominent for PolyShok, which had no peaks associated with the polyurethane constituent. The onset of the lower-temperature endothermic transformation is near body temperature. No glass transitions were observed in the materials. SEM examination revealed different surface morphology and possible cushioning effect for PolyShok, compared to Pro-form and EVA.
The difference in thermal behavior for PolyShok is tentatively attributed to disruption of EVA crystal formation, which may contribute to its superior impact resistance. The lower-temperature endothermic peak suggests that impact testing of these materials should be performed at 37 degrees C.
采用差示扫描量热法（DSC）和温度调制差示扫描量热法（TMDSC）研究三种护齿材料的热转变，并深入了解其先前研究的能量吸收情况。
从以下材料中获取样品（13 - 21毫克）：（a）传统乙烯 - 醋酸乙烯酯（EVA），（b）另一种EVA聚合物Pro - form，以及（c）含聚氨酯的EVA聚合物PolyShok。首先在 - 80至150摄氏度以10摄氏度/分钟的升温速率进行传统DSC（n = 5），以确定结构转变的温度范围。随后，在 - 20至150摄氏度以1摄氏度/分钟的升温速率进行TMDSC（n = 5）。使用方差分析和Tukey - Kramer HSD检验比较起始温度和峰值温度。其他样品用金钯膜涂层并用扫描电子显微镜检查。
传统EVA和Pro - form的DSC和TMDSC曲线相似，显示出两个吸热峰，表明存在熔化过程，在较高温度峰之后有结晶现象。PolyShok的结晶证据和第二个吸热峰则不那么明显，且没有与聚氨酯成分相关的峰。较低温度吸热转变的起始温度接近体温。在这些材料中未观察到玻璃化转变。扫描电子显微镜检查显示，与Pro - form和EVA相比，PolyShok具有不同的表面形态和可能的缓冲作用。
PolyShok热行为的差异初步归因于EVA晶体形成的破坏，这可能有助于其卓越的抗冲击性。较低温度的吸热峰表明这些材料的冲击测试应在37摄氏度下进行。
