dc.description.abstract | Abstract
Due to the need of environmental pollution control and strict legal limitation, conventional solvent-borned PU resin systems were replaced by low solvent or solvent-free aqueous PU dispersion.Water-borned PU use water as a solvent are less expensive,have excellent mechanical strengh and cause less pollution. So in the last 40 years,water-borned PU have generated interest.
From 1970,since the fous on PU was mostly from industry,most of the literature was in the form of patents with emphasis only on synthesis and particle stability. The structure and property relationship, especially the effect of ionic group on the physical and morphological behaviors, has obtained very little attentions.In past,no matter patent or litrerature, polar polyester or polyether-polyol usually are the soft segment, but water-borned PU with nonpolar soft segment was received less attention. So,HTIP(Hydroxyl terminated Polyisoprene) as Mw 2500 was synthesized as soft segment in our series nonpolar water-borned PU dispersion by prepolymer mixing processes. The hard segment content was 30,50 and 70 wt.%). Ionic content was 1.0 - 3.0 wt.% and neutralizing agent were TEA,TPA and TBA. The variables were studied by ZetaSizer,Viscosity,FTIR,TGA,DSC,DMA and mechanical properties.
The average diameter of dispersion particles become samaller with increasing hard segment content and decreasing ionic content. Successfully the series dispersion were synthesized and characterized by FTIR. The result of DSC and TEM of HTPB based WPU showed that the micro-structure of water-borned polyurethane was three-dimensional network and the density of network increased with increasing ionic content and hard segment content. The result of DMA showed that the relaxation temperature decreases with the increasing ionic content and increase with hard segment content. The relaxation temperature decreses with increasing number of carbons in various neutralizing agents. From the results of mechanical behavior,tensile strengh and initial modulus increase with increasing ionic content and hard segment content,elongation at break decrease with increasing ionic content and hard segment content. Tensile strengh and initial modulus decreases and elongation at break increases with increasing number of carbons in various neutralizing agents. | en_US |