Atai Mohammad, Watts David C
Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965/115, Tehran, Iran.
Dent Mater. 2006 Aug;22(8):785-91. doi: 10.1016/j.dental.2006.02.009. Epub 2006 Mar 15.
The aim of the study was to develop a new kinetic model for the shrinkage-strain rates of dental resin composites. The effect of filler content on the shrinkage-strain kinetics and degree of conversion of dental composites was also investigated.
A resin matrix containing 65 wt.% Bis-GMA and 35 wt.% TEGDMA was prepared. 0.5 wt.% camphorquinone and 0.5 wt.% dimethyl aminoethyl methacrylate were dissolved in the resin as photo-initiator system. Silanized glass fillers were added in different percentages to the resin-monomers. The shrinkage-strain of the specimens photopolymerized at circa 550 mW/cm2 was measured using the bonded-disc technique at 23, 37 and 45 degrees C for the matrix monomers and 23 degrees C for the composites. Initial shrinkage-strain rates were obtained by numerical differentiation of shrinkage-strain data with respect to time. Degree-of-conversion of the composites containing different filler contents was measured using FTIR spectroscopy.
A new kinetic model was developed for the shrinkage-strain rate using the autocatalytic model of Kamal [Kamal MR, Sourour S. Kinetic and thermal characterization of thermoset cure. Polym Eng Sci 1973;13(1):59-64], which is used to describe the reaction kinetics of thermoset resins. The model predictions were in good agreement with the experimental data. The results also showed a linear correlation between the shrinkage-strain (and shrinkage-strain rate) and filler-volume fraction. The filler fraction did not affect the degree-of-conversion of the composites.
The rate of polymerization, determined via the shrinkage, being invariant with filler-fraction, suggests that only a relatively high filler-surface area, as may be obtained with nano-fillers, will affect the network-forming kinetics of the resin matrix.
本研究旨在建立一种用于牙科树脂复合材料收缩应变率的新动力学模型。同时还研究了填料含量对牙科复合材料收缩应变动力学和转化率的影响。
制备了一种含有65 wt.%双酚A双甲基丙烯酸缩水甘油酯（Bis-GMA）和35 wt.%三乙二醇二甲基丙烯酸酯（TEGDMA）的树脂基体。将0.5 wt.%的樟脑醌和0.5 wt.%的甲基丙烯酸二甲氨基乙酯溶解在树脂中作为光引发体系。将不同百分比的硅烷化玻璃填料添加到树脂单体中。使用粘结圆盘技术在23、37和45摄氏度下测量在约550 mW/cm2光照下光聚合的试样的收缩应变，基体单体在23摄氏度下测量，复合材料在23摄氏度下测量。通过对收缩应变数据进行时间的数值微分获得初始收缩应变率。使用傅里叶变换红外光谱法测量含有不同填料含量的复合材料的转化率。
利用Kamal的自催化模型[Kamal MR, Sourour S. Kinetic and thermal characterization of thermoset cure. Polym Eng Sci 1973;13(1):59-64]建立了一种用于收缩应变率的新动力学模型，该模型用于描述热固性树脂的反应动力学。模型预测与实验数据吻合良好。结果还表明收缩应变（和收缩应变率）与填料体积分数之间存在线性相关性。填料分数不影响复合材料的转化率。
通过收缩确定的聚合速率与填料分数无关，这表明只有纳米填料可能获得的相对较高的填料表面积才会影响树脂基体的网络形成动力学。
