Preparation And Characterization Of Water-Borne Polyurethane-Acrylics Hybrid Latexes

In this paper polyurethane-acrylics (PU-AC) hybrid latexes were prepared using isophorone diisocyanate, dimethylol propanic acid (DMPA) and polypropylene oxides (PPO, DL1000 and DL2000) as main monomers for PU. Acrylic monomers included butyl acrylate, methyl methacrylate and a crosslinker, trihydroxymethyl propane triacrylates (TMPTA).In a first step, keeping hydroxyethyl acrylate (HEA) at 2% of PU, several ingredients such as surfactants, initiator, DMPA and PU/AC ratio, were varied, and their effects on latex properties were studied. Compared with surfactant free PU-AC latexes, a sharp increase in particle size was observed in latexes done with 0.1% of surfactant regardless of the nature of the surfactants used (anionic, nonionic and anionic with long chain of amphiphilic alkylphenyl polyethoxylate). Further increase in surfactant content, however, led to latexes with smaller particle size and narrower particle size distribution. When amount of the oil soluble initiator, azobisisobutyronitrile (AIBN), was increased, AC monomers conversion increased. It was observed that PPO with long propylene oxides brought about larger particle size, less charge on particle surface and lower tensile strength of films; whereas lower DMPA levels led to latexes also of larger size combined with lower tensile strength of films; AC monomer crosslinker, TMPTA, contributed to reduce particle size, lower particle surface charges and lower tensile strength of films. By increasing AC amount in PU-AC latex, latex particle size significantly increased concomitantly with a remarkable increase in particle surface charges.Secondly, with the purpose to study PU grafting efficiency, PU-AC hybrid latex was prepared using hydroxyethyl acrylate (HEA) as grafting agent. The kinetic of the reaction between OH of HEA and NCO group was studied. It was observed that the reaction between OH and NCO were a second-order reaction, and the reaction rate depended on the amount of HEA rather than on NCO content. By increasing the reaction temperature after addition of HEA, the reacted NCO amount increased and double bonds content kept at a constant value. Butylamine brought about the highest end-capping efficiency. Based on the above results, HEA amounts, soft segment component, PU and AC ratios were varied and their effects on PU-AC grating properties and PU-AC latex properties were studied. It was found that when the amount of HEA increased, the grating efficiency of PU increased accompanied with the decrease of water absorption of the film. By increasing soft segment DL1000 content, particle size of PU-AC latex increased, but PU grafting efficient had no obvious changes. The increase of AC amount contributed to lower AC monomers conversion but PU grafting efficient had no obvious changes.In addition, a new grafting agent,α-allyl glyceroether (AG), which contains two OH and one C=C, was synthesized and characterized by NMR, IR, GC and refraction index. The influence of AG on PU-AC properties was preliminarily studied.