Study On The Preparation And Properties Of Waterborne Alkyd Resin Modified By Polydimethylsiloxane And Polyurethane

Alkyd resin has long been one of the largest amount of synthetic resin in China, and accounted for about 90% of the total amount of synthetic resin in the early time. Alkyd coatings has the advantage of using renewable and rich source of raw materials, having high gloss of the film, mature synthesis process, good compatibility with other resins easily, good controllability of the recipe. It’s one of the most widely used industrial and architectural coatings. However, waterborne alkyd resin has the disadvantage of the poor drying ability, low hardness, poor water resistance and weather resistance, poor storage stability. This paper aims to prepare waterborne alkyd resin with good drying properties, storage stability, hardness, mechanical properties, surface properties and thermal stability. To this end, we have carried out the following several aspects of research:(1) A alkyd resin doil(AR-doil) was prepared by alcoholysis and esterification reaction between soybean oil(SO), trimethylolpropane(TMP) and phthalic anhydride(PA). Waterborne polyurethane modified alkyd resin(WPAU) was prepared by the reaction among AR-doil, isophorone diisocyanate(IPDI), 1,4-butanediol(BDO) and dimethylol propane(DMPA).(2) The effect of different AR-doil on the properties of WPAU were investigated. The results showed that the mechanical properties of linseed oil based WPAU film decreased greatly as excessive self-crosslinking of unsaturated double bond. Palm oil based WPAU has poor drying and mechanical properties because its iodine value is not enough. Soybean oil based WPAU film showed good overall properties. When TMP / SO molar ratio was too high, the mechanical properties of WPAU film decrease because of the hign branched AR-doil. When the excess alcohol was too high, WPAU film became hard and brittle. When the acid value was too high, the stability of WPAU emulsion was poor. When TMP / SO molar ratio, excess alcohol, acid value were 2.05, 20%, 5~7 mg KOH·g-1, respectively, the WPAU has the good emulsion stability, mechanical properties and surface properties.(3) The effect of the content of DMPA, n(NCO) / n(OH), EDA, on the properties of WPAU were investigated. The results showed that as the DMPA content increased, the WPAU emulsion has better stability but poorer drying properties and water resistance. As the n(NCO) / n(OH) decreased, the water absorption and mechanical strength of the films decreased. When EDA content was too high, WPAU has poor emulsion stability and poor adhesion but hign hardness. When the content of DMPA, n(NCO) / n(OH), EDA were 5%, 1.15, 1.6%, the WPAU has the better emulsion stability, mechanical properties and surface properties.(4) Polydimethylsiloxane(PDMS) was used to modify the WPAU emulsion. Firstly, the effect of feeding order of PMDS on the stability of WPAU emulsion were investigated. Then the effect of the type of PDMS on the properties of PDMS-WPAU were investigated. The results showed that hydroxy-PDMS has poor compatibility with WPAU. Although the surface properties of the modified WPAU was good, the mechanical properties was too bad because of the excessive micro-phase separation. Because there are too much hydrophilic group ester bond(-C-O-C-) in hydroxy polyether-PDMS, the water absorption of the modified WPAU was too high. Hydroxypropyl-PDMS has good compatibility with WPAU, and it promoted appropriate micro-phase separation in WPAU. So the mechanical properties, water resistance, stain resistance of the modified WPAU was good. The particle size, tensile strength, elongation at break, water absorption, water contact angle, surface free energy of the modified WPAU were 106 nm, 8.1MPa, 356%, 4.3%, 104°, 24.2m N·m-1, respectively.(5) The effect of the hydroxypropyl-PDMS content on the properties of PDMS-WPAU were investigated. The results showed that when the PDMS content was too high, it made excessive micro-phase separation in PDMS-WPAU, so its emulsion stability and mechanical properties decreased greatly. The optimized PDMS content was 6%. The thermal stability of PDMS-WAPU film increased greatly with the PDMS content increased, and the thermal stability of the hard segment increased much more than the soft segment.(6) The morphology of the fracture surface of the modified WPAU film were investigated. The results showed that WPAU modified by hydroxy-PDMS or PDMS, which has higher molecular weight, showed a greater degree of micro-phase separation.