The solubility of nonivamide in dimethyl sulfoxide, methanol, acetone, ethyl acetate, methyl tert-butyl ether, acetonitrile, n-hexane and water over the temperature range of 293.2 K to 323.2 K was measured. The results reveal that the solubility of nonivamide is greatly influenced by the hydrogen-bond basicity of solvent and increases with temperature. The experimental data were correlated with the modified Apelblat equation. The dissolution enthalpy and entropy of nonivamide in different solvents were obtained from the correlation of lnx with 1/T using the van't Hoff equation. The calculated nonivamide solubility is in good agreement with experimental data for most of the solvents.
糠醛渣是玉米芯制糠醛剩下的废渣,量大且未得到有效利用。糠醛渣主要含有纤维素和木质素,是制备乙酰丙酸的理想原料。以高温液态水为反应介质,以稀硫酸为催化剂,考察了液固比、酸浓度、反应时间和反应温度对糠醛渣降解制备乙酰丙酸的收率的影响,得到了糠醛渣制备乙酰丙酸的适宜工艺条件:固液比1:10、酸浓度2%、温度180℃、反应时间2 h,此时乙酰丙酸的收率达到66.6%。另外,以一级连串反应动力学方程对实验数据进行拟合,得到纤维素水解的表观活化能为122.7 k J×mol^(-1),葡萄糖降解生成乙酰丙酸的表观活化能为107.6 k J×mol^(-1)。
Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support and keep cells.An in-situ polymerization-modification process with esterification and polycondensation stages was performed in a 2 L batch stirred reactor using pyromellitic dianhydride(PMDA)or pentaerythritol(PENTA)as modifying monomers to obtain PETs with high melt strength.The influence of amounts of modifying monomers on the properties of modified PET was investigated.It was found that the selected modifying monomers could effectively introduce branched structures into the modified PETs and improve their melt strength.With increasing the amount of the modifying monomer,the melt strength of the modified PET increased.But when the amount of PENTA reached 0.35%or PMDA reached 0.9%,crosslinking phenomenon was observed in the modified PET.Supercritical carbon dioxide(ScCO2)was employed as physical foaming agent to evaluate the foaming ability of modified PETs.The modified PETs had good foaming properties at 14 MPa of CO2pressure with foaming temperature ranging from 265°C to 280°C.SEM micrographs demonstrated that both modified PET foams had homogeneous cellular structures,with cell diameter ranging from 35μm to 49μm for PENTA modified PETs and38μm to 57μm for PMDA modified ones.Correspondingly,the cell density had a range of 3.5×107cells·cm 3to 7×106cells·cm 3for the former and 2.8×107cells·cm 3to 5.8×106cells·cm 3for the latter.
通过高温高压磁悬浮天平(MSB)测定表观溶解度、高温高压视窗釜进行溶胀度校正的方法研究了CO2在PET熔体中的溶解度,考察了温度、压力对改性前后PET在CO2环境中的溶胀度和CO2溶解度的影响。结果表明,PET在CO2环境中的溶胀度和CO2溶解度均随温度的增加而减小,随压力增加而增加,但高压下溶胀度的增加趋势减缓并趋于某定值;与常规线性PET相比,改性PET具有较小的溶胀度和溶解度。在250～280℃,4～6MPa下,CO2在PET熔体中的溶解度具有10-2 g CO2.(g PET melt)-1的量级。1～6MPa下CO2在PET熔体中的溶解行为符合亨利定律,利用最小二乘法拟合得到了CO2在PET熔体中的溶解热。
Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of i PP and i PP/nano-CaCO_3 microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for i PP/nano-CaCO_3 composites, especially at high CO_2 concentration and back pressure, low mold temperature and injection speed, and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process, with the application of the measured ScCO_2 solubility and diffusion data for i PP and i PP/nano-Ca CO_3 composites respectively. For neat i PP, the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However, for i PP/nano-CaCO_3 composites, the correction factor for nucleation activation energy F and the pre-exponential factor of nucleation rate f_0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f_0 can be used to predict the microcellular injection molding process for i PP/nano-CaCO_3 composites by Moldex 3D.
