Synthesis of natural rubber based cationic waterborne polyurethane dispersion for adhesive applications

Abstract : Novel cationic waterborne polyurethane (cWPU) based on natural rubber (NR) have been prepared by the polymerization reaction of hydroxyl telechelic natural rubber (HTNR), toluene-2,4-diisocyanate (TDI), N-methyl diethanol amine (NMDEA, as emulsifier), and ethylene glycol (EG, chain extender). The polyol structures have been developed as alternative to produce cWPUs derived from a renewable resource. The effects of five parameters were studied – amount of NMDEA (0 – 2.25 mole), amount of EG (0 – 3 mole), molecular weight of HTNR (~1000 – 3000 g/mole), NCO index (100 – 150), and epoxide content on eHTNR soft segment (0 – 30%). The appearance of cWPU dispersion was milky-blue with long shelf life time, more than 10 months. Particle of prepared cWPU were spherical shape in the nano range size. The adhesive properties of cWPUs on the real leather surface, taking into account of the different molecular weights of HTNR and different degree of epoxide content on HTNR, were tested by lap shear test and 180 degree peel test and compared with commercial adhesives. Overall, to balance the stability and adhesive strength, the best conditions for preparing cWPU adhesive for leather application in this study was from the composition of HTNR3000 with epoxide content of 10%, NMDEA 5.67%wt, NCO index of 100 and 1 mole of EG. in condition of curing at 70 °C. In comparison to non-solvent based and solvent based commercial adhesives, the adhesive strengths of these synthesized cWPU adhesive were superior.
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Nathapong Sukhawipat. Synthesis of natural rubber based cationic waterborne polyurethane dispersion for adhesive applications. Chemical engineering. Université du Maine; Prince of Songkla University, 2018. English. ⟨NNT : 2018LEMA1013⟩. ⟨tel-02105401⟩

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