Synthesis And Properties Of Dimer Fatty Acid Modified Unsaturated Poiyester Resin

Unsaturated polyester resins (UPR) are by far the most widely used thermosettingmaterials. Because they have excellent properties, they have been widely applied in manyfields such as industrial, agriculture, national defense and so on. However, their applicationsare seriously limited by their poor resistance to low impact strength and small elongation atbreak, i.e., they are inherently brittle. So it is necessary to modify unsaturated polyester toimprove its applied performance.Dimer fatty acid has been chosen as a raw material because of low cost, abundancereproducible resource in china. In this thesis, modified unsaturated polyester was synthesizedby melting method, using C36dimer fatty acid (DA), cis-butenedioic anhydride (cBA) andpropylene glycol (PG) as main materials. By researching synthesis reaction conditions, therelationship between structure and properties of UPR had extremely versatile in properties,more efficient and lower cost modified UPR. These results of the thesis are extremelyimportant to extend synthesis and more excellent properties of UPR.The main research content are stated as follows:Researching synthesis process and prescription of modified unsaturated polyester resin.The structure of polymer was characterized by infrared spectrum and gel permeationchromatography. The optimum reaction conditions of polyester were as follows: the first stepreaction went through2hour in170℃, the second step reaction went through3.5hour in170℃, the preferable catalyst is p-toluene sulfonic acid and the amount is1.0%of the mass ofmaterials.The performance of modified unsaturated polyester resin which was influenced byproportion of styrene, proportion of benzoyl peroxide, curing time and curing temperaturewas studied. By researching and analysesing properties of modified unsaturated polyesterresin, the experimental results showed that, the appreciate methanol/oil mole ratio2.4:1. Theoptimum cure conditions of modified UPR were determined as follows,styrene/cis-butenedioic anhydride mole ratio is3.5:1, the amount of benzoyl peroxide is1.0%of the mass of polyester, curing time is4h, curing temperature of80℃.IR, the mechanical properties, alkali resistance, water resistance, flame resistance andthermogravimetry analysis of castings of the modified UPR were measured. Themicrostructures of modified unsaturated polyester resin were characterized using scanning electron microscopy. The results indicated that: analyses to IR chart indicated modified UPRhas similar structure to commodity UPR; with the introducing of dimer fatty acid, thetoughness of unsaturated polyester was improved. The impact fracture section of modifiedunsaturated polyester showed ductile failure. The comprehensive properties of modified UPRcontaining16.04%DFA were optimal. The elongation at break was increased from2.0%to41.5%, the impact strength was increased from5.990kJ/m2to28.356kJ/m2when the molefraction of DFA was about16.04%. Alkali resistance, water resistance and the thermalstability of dimer fatty acid modified UPR were better than the unmodified unsaturatedpolyester resin.