Effects Of Soft Segment Chain Structure On The Properties Of Waterborne Polyurethane

Polyurethane is the shortened form of carbamate which has the advantages of good abrasion resistance, water resistance, solvent resistance and good elastic-city. The waterborne polyurethane refers to the introduction of hydrophilic groups to the main chain or side chain of polyurethane, or adding emulsifier which can be dispersed in water to form the aqueous polyurethane dispersions. In the preparation of waterborne polyurethane without solvent, it has the advantage of non-toxic, no pollution to the environment when compared with the traditional solvent based polyurethane. This paper mainly focuses on the soft segment structure of waterborne polyurethane to probe its effect on the properties of waterborne polyurethane. Different waterborne polyurethanes were synthesized, and discussed the effects of polyester type, the polyester average molecular weight and the different adipate series polyester on the properties of waterborne polyurethanes. The stability and the particle size of the emulsions, the mechanical and heat resistance properties of the films and its peeling strength were studied.(1) Effects of different structure type polyester diol on properties of waterborne polyurethaneA series of waterborne polyurethanes were synthesised based on polycarbonate diol (PCDL), polybutylene glyool adipate(PBA), phthalic acid polyester diol(PPA), dimer fatty acids based polyester polyol(PDFA), polycaprolactone(PCL), diethylene glycol(DEG), dihydromethyl propionic acid (DMPA),isophorone diisocyanate(IPDI) and the molecular weight of polyesterdiol is 2000.The emulsion stability, particle sizes, thermal and mechanical properties and water absorption of films had been tested.The 24h film water absorption indicated that PDFA-PU and PCDL-PU have a perfect water resistance; the emulsions have smaller particle size, well stability and appearance. Film thermo gravimetric analysis (TGA) shows that heat-resistance of properties PCDL-PU is the best but PCL-PU is the most poor. Mechanical strength test shows that the PCDL-PU has the best mechanical properties, and tensile strength reaches 49.78 MPa. The PPA-PU film is soft and has poor mechanical properties. The PBA-PU has the best crystal which T-peel strength was 24.5N/cm.(2) The effect of molecular weight of soft segment on the properties of waterborne polyurethaneA series of waterborne polyurethanes were synthesised based on different molecular weight of PBA (600,1000,2000,3000, and 4000) as soft segment, dihydromethyl propionic acid (DMPA), diethylene glycol (DEG), isophorone diisocyanate (IPDI). The emulsion stability, particle sizes, thermal and mechanical properties and water absorption of films had been tested. A lot of testing methods like Infrared spectroscopy, particle size analyzer, Thermogravimetric analysis, DSC analysis, mechanical properties testing, and T-peel strength test were used to discuss the effects of molecular weight on waterborne polyurethane properties.The Emulsion stability test and particle size test showed that this series of waterborne polyurethane have good stability, and solid content did not change significantly. The water resistance test of films showed that with the increasing of PBA molecular weight, the water resistance improved. TG test showed that heat resistance of this series polyurethane films gradually decreaseed with the increasing of PBA molecular weight. DSC test showed that with the increasing of PBA molecular weight, the crystallinity of films increaseed obviously. Mechanical properties test showed that when PBA molecular weight was 4000, the tensile strength of the film reached the maximum at 28.5MPa; When the PBA molecular weight was 1000, the elongation at break was the largest at 282.5%. T-Peel strength of different soft segments showed that the T-peel strength increaseed gradually with the increasing of PBA molecular weight.(3) Property studies of different type of adipic acid polyester polyol waterborne polyurethaneA series of waterborne polyurethanes were synthesised based on polyethylene glycol adipate diol (PEA), polybutylene glycol adipate diol (PBA), polyhexylene glycol adipate diol (PHA), polyneopentyl glycol adipate diol (PNA), polytrimethylpentanediol adipate diol (PTPDA) as soft segment, dihydromethyl propionic acid (DMPA), diethylene glycol (DEG), isophorone diisocyanate (IPDI). The emulsion stability, particle sizes, thermal and mechanical properties and water absorption of films had been tested. A lot of testing methods like Infrared spectroscopy, particle size analyzer, DSC analysis, mechanical properties testing, and T- peel strength test were used to discuss the effects of molecular weight on waterborne polyurethane properties.Results showed that all waterborne polyurethane emulsions were stability, straight chain structure of polyester type waterborne polyurethane gave good strength and T-peel strength, and increaseed with increasing of chain length. The mechanical strength of the branched polyester diol structure was relatively small but with high elongation at break. T-Peel strength showed that straight chain type polyester diol with crystallinity gave good T-Peel strength and increased with the increasing chain length. In the mixed soft segment, while PTPDA/PBA ratio was 1:2, it had better tensile strength and T-peel strength.