The Setting Chemistry of Glass Ionomer Cement

The setting chemistry of glass ionomer cement was imestigated by using mechanical determination of compressive strength at predetermined intervals,and measurement of structure changes of correspondling fracture sample by means of IR spectra and differential scanning calorimetry（DSC）.Zinc polycarboxylate cement was used as a comparison sample.The compressive strength of glass ionomer cement（GIC） increases with aging.IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied.however,no significant changes occur in the zinc polycarxyolate cement.Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging.The structure changes include the crosslink density,the ratio of complex form to ionic form,the content ratio of Al-PAA to Ca-PAA,the forming and maturing process of the interface layer comprising of silica gel.

Short-term Mechanical Properties of Glass Ionomer Cement

The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of set cement stored in silicone oil, air and distilled water respectively at different temperatures. For the set cement stored at 37 ℃, the strength of the sample in the air reached the maximum value after 24 h, then decreased to about 210 MPa and kept steady. The strength of the sample in water increased continuously and slowly, however, the increasing rate of sample stored in silicone oil was higher than that in the water. At 20 ℃, the increasing rate of compressive strength for sample in air was higher than those in silicone oil and water. The diffusion speed and maintenance of water has significant effects on the mechanical properties of glass ionomer cements.

固化玻璃离子水门汀的DSC/TG研究

目的:研究玻璃组成中磷含量对玻璃离子水门汀固化过程的影响。方法:基于SiO2-1/2Al2O3-1/2CaF2-1/2zP2O5,(z=0,1/12.5,1/6.25,1/3.125)组成,制备了不同磷含量的玻璃粉剂,采用DSC/TG热分析技术研究4种不同磷含量玻璃组成、2种市售玻璃离子水门汀和1种聚羧酸锌水门汀对照样品的热分解特点。结果:固化玻璃离子水门汀的基体分解放热峰的温度和形态随磷含量变化而变化,当磷含量增加时,由一个变为两个,且明显变宽。结论:在玻璃离子水门汀固化过程中有磷进入基体中,当磷含量较高时,可以直观地观察到它们对聚合物基体热行为的影响。

玻璃离子水门汀固化反应的红外光谱研究

用红外光谱研究了玻璃离子水门汀固化反应过程, 结果显示, 表征聚丙烯酸盐的峰强度(～1 413 cm-1)随时间延长而逐渐增加, 而硅醇基团, 即最强峰(～1 039 cm-1)上的肩峰(950 cm-1), 在所观察的周期中仍然存在. 因此, 玻璃离子水门汀抗压强度随时间延长而增加的原因在于: ①Ca2+, Al3+与聚丙烯酸的固化化学反应在一个相当长的时间内仍在进行;②因玻璃结构分解形成的硅醇基团将长期存在, 并在缩合形成硅凝胶的过程中, 改变基体与填料间的界面结构和组成, 因此对玻璃离子水门汀的长期力学性能也将产生一定的影响.

玻璃离子水门汀短期力学性能的研究

通过分析比较不同温度下,放置在硅油、水和空气中的的玻璃离子水门汀的短期抗压强度,研究了玻璃离子水门汀的固化反应过程。37℃时,放置在空气中的试样2 4h后,其强度达到最大值,然后略有下降,并保持稳定;放置在水中的试样,其抗压强度呈持续、缓慢增加的趋势;硅油中的试样则呈持续、增加的趋势,但其增加速度明显高于水中的试样。2 0℃时,无论是空气或硅油中试样的抗压强度增加速度较37℃时明显降低,放置在空气中的试样30d后达到最大值。因此,水的扩散速度和保持对玻璃离子水门汀的力学性能具有十分重要的影响。

玻璃离子粘固剂的研究现状

近２０ａ来，玻璃离子粘固剂（ｇｌａｓｓ－ｉｏｎｏｍｅｒｃｅｍｅｎｔｓ，ＧＩＣ）的研究取得了一系列进展，目前ＧＩＣ的应用日趋广泛。笔者拟就ＧＩＣ的有关研究现状进行综述。