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首页> 外文期刊>Journal of Applied Polymer Science >Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)
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Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)

机译：模型聚（醚氨基甲酸酯脲）和聚（酯氨基甲酸酯脲）的耐水解性

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Poly(ester urethane ureas) (PesURUs) and poly(ether urethane ureas) (PetURUs) synthesized from diphenylmethane-4,4'-diisocyanate and poly(butylene adipate) diol, and poly(tetramethylene oxide) diol or poly(propylene oxide) diol, respectively, were hydrolyzed at 70 degrees C for various periods up to 16 weeks. Differences in thermal and mechanical properties of as-received dry samples are correlated with the number and strength of hydrogen bonds formed between urea/urethane groups of hard segments and polyester or polyether groups of soft, segments. Gel permeation chromatography measurements show that the molar mass of linear PesURUs markedly decreases with the hydrolysis time, whereas that of linear PetURUs remains almost unaffected. PesURU crosslinked by polymeric isocyanate has lower crystallinity, but shows somewhat better resistance to hydrolysis than its linear counterpart because of its more stable three-dimensional molecular structure. Water uptake at 37 degrees C, dynamic mechanical thermal analysis, and differential scanning calorimetry thermograms determined for redried hydrolyzed specimens concurrently show that advancing hydrolysis accounts for decrease in the crystallinity (if any) of soft polyester segments, in the efficacy of hydrogen bonding and in crosslinking density. Experimental data indicate that hydrolytic resistance of PetURUs is primarily determined by (1) the hydrolytic stability of individual types of present groups, (2) steric hindrances affecting the access of water molecules to these groups, and (3) the hydrophilicity of backbones. (C) 1998 John Wiley & Sons, Inc. [References: 38]
机译：由二苯基甲烷-4,4'-二异氰酸酯和聚己二酸丁二酯二醇，聚四甲撑环氧乙烷二醇或聚环氧丙烷合成的聚酯（酯氨基甲酸酯尿素）（PesURU）和聚（醚氨基甲酸酯尿素）（PetURU）二醇分别在70摄氏度下水解16星期。干燥样品的热力学性能差异与硬链段的尿素/氨基甲酸酯基团和软链段的聚酯或聚醚基团之间形成的氢键数量和强度相关。凝胶渗透色谱法测量表明，线性PesURUs的摩尔质量随水解时间而显着降低，而线性PetURUs的摩尔质量几乎不受影响。通过聚合物异氰酸酯交联的PesURU具有较低的结晶度，但由于其更稳定的三维分子结构，因此与线性对应物相比，显示出更好的耐水解性。同时测定了在37摄氏度下的吸水率，动态机械热分析和差示扫描量热法热分析图（针对重干的水解样品），表明进行水解会导致软质聚酯链段的结晶度（如果有）降低，氢键作用和交联密度。实验数据表明，PetURUs的抗水解性主要由以下因素决定：（1）各个类型本基团的水解稳定性，（2）影响水分子进入这些基团的空间位阻以及（3）骨架的亲水性。 （C）1998 John Wiley＆Sons，Inc. [参考：38]

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