中和度对水性硅溶胶/聚氨酯杂化树脂交联性能的影响

水性聚氨酯/无机复合材料兼具有机物和无机物的优点，是一类非常有发展前景的复合材料。然而，有机物与无机物之间的差异使两相相容性不好，不仅限制了无机材料在聚合物基体中的作用而且导致复合材料结构不均，综合性能下降。因此，保证无机粒子在聚氨酯基体中的均匀分散是制备性能优异的水性聚氨酯/无机复合材料的关键。本文将高支化度的水性硅溶胶（KS560）添加到3–氨基丙基三乙氧基硅烷（APTES）封端的WPU乳液中，通过sol-gel反应制备了均一的水性聚氨酯/SiO₂复合乳液（WPU/SiO₂）。体系的中和度（DN）由三乙胺/2,2–二羟甲基丙酸（TEA/DMPA）的摩尔比控制。研究了体系DN值对复合乳液结构和性能的影响。通过²⁹Si NMR及流变实验证实WPU与KS560之间的化学交联结构。随着DN值增加，这种化学交联程度增大，使得流变的储能模量值降低。SEM照片发现KS560的加入可分散转移成膜过程中产生的应力，并阻止裂纹的形成。而DN值增加有利于改善复合胶膜表面的平整度。同时，KS560为WPU引入了聚硅氧烷网络结构，使复合材料热稳定性，耐水性及力学性能均得到提高。当DN为80%时，复合材料的吸水率达到最低值4%。另外，随DN值增加，KS560与WPU之间的界面强度，KS560之间的缩合程度增加，这使复合材料的拉伸强度及模量值均增加。因此，DN值为80%时可制备综合性能优异的WPU/SiO₂复合材料。

Effect of the Degree of Neutralization on the Crosslinking of the Aqueous Silica Sol/WPU Composite Polymer

WPU/inorganic composite material has been taken as a kind of promising materials,since it has both advantages of organic and inorganic materials.However,the structural difference between organic and inorganic materials resulted in bad compatibility.The bad compatibility not only restricted the function of inorganic particles in polymer,but also caused the inhomogeneous structure as well as inferior properties of composite materials.Thus,good dispersity of inorganic particles in polyurethane was the key factor for obtaining WPU/inorganic composite with excellent properties.The WPU/SiO₂ composite emulsion was prepared by sol-gel process,which consisted of an aqueous silica sol with highly branched structure (KS560) and (3–aminopropyl) triethoxylsilane (APTES)-terminated waterborne polyurethane (WPU).The degree of neutralization (DN) of composite emulsion was controlled by the mole ratio of Triethylamine (TEA)/2,2–Dimethylolpropionic acid (DMPA),and the effect of DN value on structure and properties of WPU/SiO₂ composite was investigated.The chemical crosslinking between WPU and KS560 was confirmed by ²⁹Si NMR and rheological test.In rheological test,the storage modulus of composite emulsion reduced with increasing the DN value,since it increased the crosslinking efficiency of WPU and KS560.SEM images found that the addition of KS560 could transfer the stress and prevent cracks in film formation.The smooth of composite film also improved with increasing DN value.Moreover,the polysiloxane network was introduced into WPU by KS560,which would improve the thermal stability,water resistance and mechanical properties of the WPU/SiO₂ composite.When the DN value was 80%,the minimum water absorption of composite was reached to 4%.In addition,an increase in DN value could promote the interaction between WPU and KS560,KS560 and KS560,thus the tensile stress and modulus of WPU/SiO₂ composite were improved.