Investigation In Performance Improvment Of Waterborne Polyurethane

The aim of this article was to improve mechanical properties and hydrophobicity of WPU through incorporating dodecafluoroheptyl methacrylate(MBFA-12) and nanocrystalline cellulose (NCC) into WPU.NCC was prepared from microcrystalline cellulose (MCC) by acid hydrolysis and high-speed shearing method, and its structure, morphology and performance were investigated using TEM, FESEM, XRD and TG in detail. The results showed that the NCC, fabricated by acid hydrolysis method, exhibited the20-60nm in diameter, higher crystallinity and better dispersibility. However, the high-speed shearing method caused NCC presented a big diameter (100nm) and lower crystallinity.A series of fluorinated waterborne polyurethane were synthesized based on isophorone diisocyanate (IPDI), poly-caprolacloneglycol (PCL),2,2-dihydromethylpropionic acid (DMPA), acrylic hydroxyl ethyl ester (HEA) and the MBFA-12. The results showed that MBFA-12could effectively improve the water resistence of WPU due to the low interface energy of fluroine:the water contact angle of WPU-F film was elevated to113.0°when the content of MBFA-12increased to40%, also, the water absorption decreased to minimum value of1.54%. In addition, it was found that the optimal tensile strength of WPU film was obtained to be13.09MPa at10%of MBFA-12, increasing by947.2%compared with non-modified WPU film.The NCC (acid hydrolysis) was used as reinforcing agent to prepare high-performance WPU. The results showed that the viscosity, particle size of emulsion, the hardness and wear resistance of WPU film were improved, when the content of NCC increased, the optimal tensile strength of WPU film appeared at5%of NCC and achieved to13.43MPa. Rheological experimental results confirmed that NCC-WPU emulsion was a pseudoplastic fluid with the shear thinned characteristic; The linear viscoelastic region was within the strain scope of0.01%-10%; With the increasing of frequency, the storage modulus and loss modulus of NCC-WPU emulsion increased, but the complex viscosity and loss coefficient decreased. TG analysis showed that the initial decomposition temperature(Ti) of NCC-WPU film, T30%,T50%and the temperature of the largest weightlessness rate (Tmax) were increased with the increasing of the content of NCC. Meanwhile, the two stage of weight loss process had a wider temperature range, indicative of improvemeng in thermal stability.