Research On Polyorganosiloxane/Polyurethane Prepolymer Modified Alkyd Resin Coatings

Alkyd coatings with the good qualities of application property, excellent fullness andflexibility,are widely used in the decoration and protection of steel structure;But alkyd resincoatings exist some obvious disadvantages,such as: slow film drying time、low hardness、lowwater resistance and poor outdoor weathering resistance.It has a relatively short lifespan in thecorrosion resistance of outdoor steel structure and cannot satisfy harsh performancerequirements of the outdoor heavy-duty coating.In order to improve the comprehensive performance of alkyd coatings,the new method tomodify the alkyd is to untilize hydroxyl terminated polydimethylsiloxane (HTPDMS) andpolyurethane (PU),and HTPDMS and PU chains grafted in the alkyd chains.This paintcombined with excellent properties of polydimethylsiloxane and polyurethane. This waymakes alkyd coatings has obvious advantages,such as excellent water resistance, weatherresistance, durability and high adhesion,which broadens the application fields of alkydcoatings in the heavy anti-corrosion of outdoor steel structure.In this thesis, alkyd resin coatings used to carry out formula design experiments andformula optimization experiments to determine the best alkyd resin coatings formula,influence of the pigment to binder ratio(P/B) and pigment volume concentration(PVC) on theperformance of paint is discussed.The experimental results showed that: alkyd resin coatingswere prepared with excellent comprehensive properties through coating formulationoptimization experiments.The optimum addition dosage of alkyd resin is50%, pigments andfillers is20%,driers is2.5%;The film has the best comprehensive performance when theextent of the pigment to binder ratio is0.6:1～0.8:1.The-NCO terminated polyorganosiloxane prepolymer was synthesized with toluenediisocya-nate(TDI) and HTPDMS.This paper discussed the influence of the types of rawmaterials、Synthesis process、reaction temperature and time、the ratio of monomer、catalyston prepolymer,using FTIR to analyze and characterize them.The experimental resultsshowed that:the raw materials required strict water treatment before the synthesis to preventthe occurrence of side effects.The optimal synthesis process and formula is: n（-NCO/-OH） 3:2, catalyst2.5%, the reaction temperature80℃, reaction time4h.We can add a certainamount of phosphoric acid to effectively prevent the gel phenomenon of prepolymer andimprove storage stability.The infrared spectral analysis showed that the-NCO groups of TDIand-OH groups of the HTPDMS occured the addition polymerization.This paper successfully prepared the polyorganosiloxane/polyurethane prepolymermodified alkyd resin coatings,using-NCO terminated polyorganosiloxane prepolymer (Acomponent) to modify alkyd coatings (B component). We do research on configuation craft,the mole ratio of-NCO to-OH, the curing mechanism of film; Through the FTIR and SEMto characterize and analyze the performance of film. The experimental results showed that:the film has the best comprehensive properties when the mole ratio of A component to Bcomponent is1:1. The results of FTIR indicated that: a chemical reaction occured when the-NCO groups of B component comes into contact with-OH groups of A component.Successful introduced-NCO groups、Si-O-Si to alkyd resin molecular chain segment. Theresults of the scanning electron microscope (SEM) analysis showed that:-NCO terminatedpolyorganosiloxane prepolymer can effectively improve the compatibility of organic siliconeand alkyd resin,formed a interpenetrative and fusional organic whole. At the intersection oftwo phase interface,the matrix appeared a continuous and mutual crosslinking interpenetratingnetwork structure (IPN).