Silicon Dioxide Coating Deposited by PDPs on PET Films and Influence on Oxygen Transmission Rate

A silicon dioxide film is deposited on the polyethyleneterephtMate （PET） by a penning discharge plasma source at ambient temperature in a high vacuum chamber. Hexamethyldisiloxane and oxygen are adopted as precursor and reactive reagent to grow a nano-scale silicon dioxide layer on polymer surfaces. For the chemical structure analysis X-ray photoelectron spectroscopy is performed to demonstrate the content of Si, 0 and C elements. It is noticed that a higher silicon concentration is contained if Ar plasma is used for pretreatment. X-ray diffraction analysis shows that a micro-crystal silicon dioxide is formed by peak patterns at 25,84° and 21.8°. The barrier properties examined by oxygen transmission rate show that the permeation parameter of the 12-μm-thick PET film drastically decreases from 135 cc/m^2 per day for the control one to O. 713 cc/m^2 per day for the as-deposited one after Ar plasma treatment. The surface morphology related to the barrier properties of SiOx-coated polymers os also investigated by scanning electron microscopy and atomic force microscopy.     

差示扫描量热法确定L-羟脯氨酸的热动力学参数

用差动热分析仪测得L_羟脯氨酸的DSC曲线 ,采用普适积分法和微分方程法通过逻辑选择确定了热分解的最可几机理函数F(α) =[-ln(1-α) ]4 ,f(α) =(1 4 ) (1-α) [-ln(1-α) ]- 3;从而计算出指前因子和活化能分别为lnA =76 9.385 17和Ea=36 6 35 4 5 .8J mol,lnA =780 .6 32 5 8和Ea=3735 377.4J mol.