No abstract

No abstract

A series of low molecular weight linear polyester polyols were synthesized by using various diacids, neopentyl glycol, as a diol, and a trimethylol propane, as a branching monomer. Polyurethane dispersions were prepared primarily from isophorone diisocyanate, polyester polyol, and dimethylol propionic acid, as potential ionic center for water dispersibility, and were subsequently chain extended with ethylene diamine. The effect of polyester polyols based on variable diacids, on the physico-chemical and thermal properties of polyurethane dispersions were evaluated by hardness, flexibility, impact resistance, solvent resistance, thermogravimetric analysis, and differential scanning calorimetry. Particle size was evaluated by particle size analyzer. It was observed that the number of alkylene groups present in the polyester polyol soft segment in addition to its molecular weight had a pronounced effect on the particle size, physico-chemical, and thermal properties. With a proper selection of the soft segment, it is possible to fine-tune properties of aqueous polyurethane dispersion coatings with respect to the final application.

Purpose -The aim of this paper is to synthesise polyester/silica hybrid resins and their hybrid polyurethanes via in situ (IS) and blending (BL) methods and to evaluate the effect of preparation method, interaction type and silica content on the physico-chemical and thermal properties of polyurethane/ silica (PU/Silica) hybrid coatings. Design/methodology/approach -Silica particle-containing silica sol was prepared according to Stö ber method using tetraethylorthosilicate as the precursor and then introduced into polyester matrix by in situ and direct blending method. The modified polyester/silica resin was further crosslinked with TMP-TDI adduct to synthesise PU/Silica hybrid coatings and studied for thermo-mechanical, physico-chemical properties. Findings -It was found IS polymerisation caused more polyester segments to chemically bond onto the surface of silica particles than BL process. Results also reveal that due to stronger interaction between silica particles and PU matrix, hybrid resins prepared by IS method confers better properties than BL method and exhibit optimal properties at the critical concentration of 8 wt% silica. Research limitations/implications -In the present study, silica particles are used to modify properties of polyurethane resins. Many other countless combinations in terms of inorganic filler or organic matrices can be explored to obtain a wide range of interesting properties and applications. Practical implications -The results obtained in this study will be extremely useful to enhance the understanding of this class of hybrid materials. Originality/value -Hybrid organic-inorganic networks offer a new area of material science that has extraordinary implications for developing novel materials that exhibit a diverse range of multi-functional properties.

Purpose -The purpose of this paper is to synthesise polyurethane/polyacrylate (PU/AC) core-shell hybrid latex by emulsion polymerisation (PUA) and interpenetrating hybrid latex by soap-free emulsion polymerisation techniques latex interpenetrating polymer networks (LIPN) and to compare their physico-chemical and thermo-mechanical properties. Design/methodology/approach -The interactions between the PU and AC components in hybrid coatings were studied with infrared spectroscopy. Mechanical properties were determined by measuring Shore A hardness, pencil hardness and flexibility of dried films. A particle size analyser and scanning electron microscopy were used to investigate the morphology of hybrid resins. Differential scanning calorimetry and thermogravimetric analysis were performed to investigate the thermal stability of polymeric films. Findings -The core-shell hybrids had better physico-chemical and thermo-mechanical properties than LIPN hybrids, attributing better interpenetration and entanglement between PU/AC in emulsion polymerisation.Research limitations/implications -The syntheses of hybrid polymers can be extended for various combinations of acrylate monomers with crosslinkers, as well as for different types of PU ionomers. Practical implications -The comparative study provides a simple and practical solution to improve performance characteristics of PU/AC hybrid coatings, which also proves to be cost effective. Originality/value -The findings are of interest to those in surface coatings and adhesive applications.