| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 106 === Adhesives were prepared by using ethoxylated bisphenol-A dimethacrylate (BisEMA) and triethylene glycol dimethacrylate (TEGDMA) of different weight ratios, 60/40 and 80/20, in feed, with camphorquinone (CQ) and diphenylphosphine oxide (DPPO) as the photoinitiators. We added zinc oxide nanoparticles in various contents of feed and cured BisEMA and TEGDMA with visible light and the photoinitiator. We used the different photocuring times (2~6 mins) of visible light. We examined the effects of BisEMA/TEGDMA weight ratios in feed, contents of zinc oxide nanoparticles and photocuring times on conversion of reaction, network structure, thermodynamic and mechanical properties.
According to FTIR analysis, the conversions of double bonds from aliphatics of two monomers increase as the contents of BisEMA increase or the photocuring time increases. But it decreases as the contents of zinc oxide nanoparticles increase. The order of propagation (n) and rate parameter (k) were calculated by the Avrami equation. As the contents of zinc oxide nanoparticles increase, the n values decreases but k values increases.
The equilibrium water contents of polymers decrease as the contents of BisEMA increase or the photocuring time increases. This is because BisEMA is a hydrophobic molecule and the longer the photocuring times will cause the higher the crosslinking degree of the resin. In addition, adding different ZnO nanoparticles contents in polymers, the equilibrium water contents will be affected by the hydrophilicity of ZnO nanoparticles after ZnO nanoparticles were irradiated and the active reaction position factor caused by ZnO. Both of compressive modulus and crosslinking density increase with increasing the contents of BisEMA in feed and photocuring times. The density of physical entanglement（Ns）was greater than density of physical entanglement（Ns）. It showed that physical cross-linking has more effect on the degree of viscoelasticity of the swelled network. And Ns / Nc ratios are almost constant (1.47~1.64). In addition, we observed the addition of an appropriate amount of ZnO helps to offset the internal stress in the composite resin. The interaction parameters of water and polymers in adhesives (χ) were calculated by crosslinking densities and equilibrium water contents. As crosslinking density increases, the mesh size of the composite resin was smaller. Then the χ values increases and the equilibrium water contents decrease.
According to DMA analysis, as the photocuring time increases, the storage modulus (G ꞌ) and the glass transition temperature (Tg) will increase. The glass transition temperature was increased by increasing crosslink density. It indicated that the proper addition of zinc oxide nanoparticles helps the resin to have better mechanical properties at high temperatures.
Experimental results showed that when we varied BisEMA/TEGDMA ratios in feed, contents of zinc oxide nanoparticles and photocuring times, that will influence the conversions of double bonds from aliphatics of two monomers, network structure of polymer and crosslink density. And there by affecting the compressive modulus and interactions between water and polymers in swollen resins, as well as affecting glass transition temperature, storage modulus and loss modulus of dry resins.
|
|---|
