The intrinsic viscosity [η], Huggins constant （Ku）, [η]0, α^3 and flow activation energy values of nylon 6 have been measured in wateηm-cresol （0/100-20/80） systems at different temperatures （20-60℃）. It ha...The intrinsic viscosity [η], Huggins constant （Ku）, [η]0, α^3 and flow activation energy values of nylon 6 have been measured in wateηm-cresol （0/100-20/80） systems at different temperatures （20-60℃）. It has been found that the intrinsic viscosity, [η]0 and α^3 increase with the increase in water contents in m-cresol up to 15% and then decrease. They increase with the increase in temperature irrespective of solvent composition. It has been noted that the percent increase of α^3 is the highest at 60℃ and the lowest at 20℃ for a particular solvent system. The intrinsic viscosity data obey Arrhenius equation over the considered conditions. The activation energy and the KH values decrease very sharply with the addition of water, giving a minimum value at 15% of water and then increase slowly. The variation of all the parameters has been explained in terms of variation in thermodynamic quality of solvent with the addition of water to m-cresol and change in temperature, resulting in the change of conformational and orientational properties of polymer molecules. This change of solvent quality also results in variation of selective sorption of solvent over the polymer, such as hydrogen bonding, etc.展开更多
磷素饱和度(Degree of phosphorus saturation,DPS)能够有效评估土壤磷素的流失潜能及地表水磷富营养化问题,可用于评价土壤磷素环境风险。DPS值通常由酸性草酸钱提取态磷(PQ与提取态铁铝(FemAlQ的摩尔质量比除以校正常数(Corrected con...磷素饱和度(Degree of phosphorus saturation,DPS)能够有效评估土壤磷素的流失潜能及地表水磷富营养化问题,可用于评价土壤磷素环境风险。DPS值通常由酸性草酸钱提取态磷(PQ与提取态铁铝(FemAlQ的摩尔质量比除以校正常数(Corrected constant,a)计算得到,而a是通过建立土壤饱和吸磷量与影响土壤磷吸附的土壤特征值间的相关关系而计算得到的数值;a的取值大小(常取0.5)会直接影响到DPS的准确估算。因此,本文以中国科学院红壤生态实验站(28。04,~28。37取,116°4 r^117。09馆)为依托,以长期施肥(1988-2014年)的旱地红壤为研究材料,通过两种计算方法得到了土壤的DPS值,分析了校正常数a=0.5在长期施肥的旱地红壤DPS计算中的适用性,并确定了长期施肥旱地红壤DPS计算中a的适用性阈值。研究结果表明:校正常数a=0.5虽适用于长期施肥旱地红壤DPS的估算,但易导致旱地红壤DPS的过高估算;对比计算发现,长期施肥旱地红壤DPS计算时,校正常数a的最适取值范围为0.71-0.81。但是,不同环境背景下旱地红壤DPS计算公式中校正常数a的适应性阈值仍需进一步校正与验证,从而提高红壤区土壤磷素环境风险评估的准确性。展开更多
文摘The intrinsic viscosity [η], Huggins constant （Ku）, [η]0, α^3 and flow activation energy values of nylon 6 have been measured in wateηm-cresol （0/100-20/80） systems at different temperatures （20-60℃）. It has been found that the intrinsic viscosity, [η]0 and α^3 increase with the increase in water contents in m-cresol up to 15% and then decrease. They increase with the increase in temperature irrespective of solvent composition. It has been noted that the percent increase of α^3 is the highest at 60℃ and the lowest at 20℃ for a particular solvent system. The intrinsic viscosity data obey Arrhenius equation over the considered conditions. The activation energy and the KH values decrease very sharply with the addition of water, giving a minimum value at 15% of water and then increase slowly. The variation of all the parameters has been explained in terms of variation in thermodynamic quality of solvent with the addition of water to m-cresol and change in temperature, resulting in the change of conformational and orientational properties of polymer molecules. This change of solvent quality also results in variation of selective sorption of solvent over the polymer, such as hydrogen bonding, etc.
