The Synthesis Of IPDI-Based Waterborne Polyurethane And Its Application On Fabric Coating

Waterborne polyurethanes (WPUs) are versatile environmentally friendly materials, made of the flexible soft chain segment (soft segment) and rigid hard chain segment (hard segment), can incorporate of hydrophilic functional groups into the polymer such as-O-, CO-、-OH, or -NH2, and as the coating agent capable of forming a dense film on the surface of the fabric, thus impart clothes many features, waterproof, breathable, warm and so on. Isophorone diisocyanate (IPDI), with two different isocyanate groups as one of them is directly bonded to the cycle (secondary NCO), whereas the second one is bonded to a methylene group (primary NCO), result in a different reactivity of two NCO groups, easily produced the prepolymer with a high molecular weight, narrow molecular weight distribution and low viscosity, is bound to become one of the main direction of development waterborne polyurethane. This article is intended to diisocyanate, polyols, dimethylol butanoic acid (DMBA), trimethylol propane (TMP), chain extender as main materials, add ethylene diamine chain extender after emulsive, finally a series of water-based polyurethane emulsion were prepared by acetone method. This thesis attempts to prepare WPU emulsions with different properties, hoping to meet the requirements of fabric coating agent in different environmental, and provide certain instructive significance to industrial production.(1) Effects of soft segment on the properties of waterborne polyurethanesThis thesis respectively used (PTMG,2000), polyester glycol (PEA, PBA, PHA,2000) and PBA (with molecular weight of 1000,2000,3000,4000) as soft segment polyether glycol, focuses on the effects of the glycol types and different molecular weight on the emulsions, film and morphology, water vapor permeability(WVP), water resistance(WP) of coated fabric.The result displays that as PTMG for soft segment has the smallest average particle size, largest contact angle, with a good degree of micro-phase separation than others, the surface of coated fabric is flatter, highest WVP and WP. Compared with PTMG, polyester PBA lack of an ether linkage in the molecular structure lead to poor micro-phase separation, performance followed. The carbon chain of PEA and PHA is is too short or too long, the property is far worse than the PBA. AS resin with different molecular weight, molecular weight of 2000, poor mechanical properties, waterproof is not high; for 1000, higher hard segment content, the moisture permeability is not good; for 4000, prepolymer of higher viscosity cause large particle size. In short, for 3000, optimal matching among heat resistance, mechanical properties, WP and WVP.(2) Effects of hard segment on the properties of waterborne polyurethanesIn this dissertation has selected common small molecule chain extender diethylene glycol, neopentyl glycol, ethylene glycol,1,4-butanediol,1,6-hexanediol, by studying the types of chain extender, IPDI content, NCO/OH molar ratio, DMBA content, TMP content, degree of EDA chain extension on the emulsions, film and morphology, water vapor permeability, water resistance of coated fabric.The result shows that NPG has two methyl side chain with lower regularity, formation of smaller particle size, poor heat resistance and mechanical properties of film. Considering to EG, BD and HD coatings, the length of the chain extender increase, result in certain changes in the degree of micro-phase separation,1,4-butanediol best of them. Diethylene glycol has additional ether bond than 1,4-butanediol, better micro-phase separation cause better results. IPDI content of 30%to 35%, morphology of coated fabric is better, have higher WVP and WP. NCO/OH molar ratio of 1.6, the better performance of coated fabric. When DMBA content increased, the particle size of the emulsion is reduced, WVP increased, but WP increased maximum and then decreased. After joining TMP, the molecular chains cross-linked into a network structure, improve mechanical property and WP, however, as the content of TMP more than 0.8%, degree of crosslinking is too high, reduce the WP. After emulsification, ethylene diamine reacted with remaining-NCO of prepolymer generated a strong polar urea group, lead to a better micro-phase separation, WVP and WP increased, when the degree of chain extension is greater than 60%, again reacted with urethane in molecular chain and resulted in excessive crosslinking, coated fabric feel worse.