Synthesis And Characterization Of Aromatic Polyester Based Polyurethane Dispersion Adhesive

Polyurethane dispersion(PUD) adhesive is a new type of polyurethane system with water as the dispersion medium and it is non-toxic and environmentally friendly. PUD adhesive has properties of good adhesion, flexibility, impact resistance, chemical resistance, low temperature resistance and excellent abrasive resistance. It’s widely used in footwear, automotive, textile, furniture, packaging and other industries. Compared with foreign high-quality PUD adhesives, domestic PUD adhesives have problems of low solid content, slow drying rate, poor water resistance and low initial adhesion. Sulfonate type PUD adhesive with high solid content has became a research hotspot in recent years. However, the polyols are mostly aliphatic polyols and the water resistance and initial adhesion are not so good.To solve the above problems, PUD adhesives based on aromatic polyester polyol were synthesized, expecting to improve the water resistance and bonding strength. Aromatic polyester based PUDs with about 50% solid content were synthesized using polyether diol containing sulfonate(SPPG), poly1,6-hexanediol phthalic anhydride(PHPA), hexamethylene diisocyanate(HDI) and ethylene diamine(EDA) by the acetone method. Effect of hydrophilic group content(HGC), R value(NCO/OH molar ratio) and chain extension on the properties of PUDs, PUD films and PUD adhesives were surveyed.The properties of PUDs were measured by Laser particle size analyzer, TEM analysis and Brookfield viscosity. The surface tension of PUD were in the range of 34~45 m N/m, which displayed good wettability. The average particle sizes of PUD were mostly in the range of 100~250 nm and the particle size distributions of PUD were mostly in the range of 50~200 nm, which displayed excellent stabilization. The average particle sizes, viscosity, particle size distributions and surface tension changed regularly with HGC, R value and chain extension. TEM analysis showed spherical shapes of the particles with different sizes and bimodal distribution. PUDs were pseudoplastic fluid.The properties of the films were characterized by Fourier transform infrared spectroscopy(FT-IR), differential scanning calorimetry(DSC), dynamic thermomechanical analysis(DMA) and thermo gravimetric analyzer(TGA). The research result showed the PUD films were soft, Shore A hardness were in the range of 35~56 and the elongation were longer than 2700%. The glass transition temperatures of PUD films were increased with the increase of R values. The degradation of PUD films started at 300 ℃ and finished at 500 ℃, which showed good thermal stability. The PUD films had excellent water resistance for the water absorption was between 0.85%~2.10%.As the activation temperature increased, T-peel strength values of the PUD adhesives increased initially and then decreased. The activation temperature of PUD adhesives were mostly in the range of 80 ℃~100 ℃ and the optimum activation temperature was 90 ℃. The T-peel strength values and heat tolerance changed with R value(NCO/OH molar ratio) and chain extension. When the R value was 1.4, T-peel strength test yielded a maximum value of 145.6 N/25 mm and heat tolerance was the best.