Synthesis, Properties Of Rosin/Oil Based Diacid And Its Polyamide Curing Agents

A rosin/oil based diacid was synthesized by Diels-Alder reaction using industrial fattyacid and renewable resource rosin as materials; then, three kinds of reactive polyamides asepoxy resin curing agents were synthesized by amidation reaction between this self-made noveloil/rosin-based diacid and three kinds of aliphatic polyamines, and the performances of thecured products of epoxy resin128/these three polyamides were tested respectively; Took one ofthe polyamides which had the superior comprehensive performance as an example for thermaldecomposition kinetic investigation, and the cure kinetics of the polyamide with epoxy resinwere determined using n order reaction and the autocatalytic model respectively, in order toprovide theoretical guidance for industrial applications of this novel polyamide curing agents.Firstly, A novel rosin/oil based diacid with fused ring structure was synthesized byDiels-Alder reaction using industrial fatty acid and rosin. The optimal synthesis conditionsindicated by single factor analysis were as follows: based on the mass of industrial fatty acid,the amount of manganese acetate catalyst is1%, the mass fraction of rosin is20%, reactiontime is5h, reaction temperature is240℃and reaction pressure is0.5Mpa, Under theoptimal synthesis conditions, The colour（iron cobalt colorimetry）of the product is14～15，the acid value is193.9mg/g, the iodine value is136.8mg/g, the viscosity is320mPa·s at40℃,and51.03%mass fraction of dimer acids was detected in the product by GPC. The productwas characterized by UV spectrum, GPC and1H-NMR.Secondly, three kinds of polyamides curing agents with different amine value weresynthesized by amidation reaction between this self-made diacid and diethylenetriamine,triethylenetetramine and tetraethylenepentamine respectively. The cured products of epoxyresin with polyamide curing agents were characterized by FT-IR spectra. and the mechanicalproperties of the cured products were tested by tensile machine、impact testing machine、SEMand so on, then the glass transition temperatures (Tg) were measured by DSC. Compared to thecured product of polyamide650prepared from traditional C36dimer acid, the cured productsof the novel polyamides curing agents had higer tensile shear strength、tensile strength、tensilemodulus、bending strength、flexural modulus、compression strength and hardness exceptslightly lower breaking elongation and impact strength. the glass transition temperatures were73.46℃、87.36℃、88.40℃, respectively, which are at least30℃higher than that of the cured product of polyamide650. Took the polyamide synthesized with triethylenetetramine and the novel diacid which had the superior comprehensive performance as an example for thermal decomposition behaviors investigation by non-isothermal thermogravimetric analysis (TGA). The thermal degrade of the cured product was first order reaction by Coats-Redfern method; the activation energy Ea of the thermal degrade of the cured product was134.85kJ/mol by Kissinger peak maximum technique; using Ozawa isoconversional procedure method, the activation energy Ea was increased from157.03kJ/mol to27.29kJ/mol, the frequency factor ln A was increased from34.99min-1to46.56min-1with increase of weight loss rate from20%to80%. the activation energy Ea above is higher than that of the cured product of polyamide651prepared from traditional C36dimer acid, so the thermal stability of the novel cured products was better.At the same time, the curing process of the novel curing reaction systerm above was studied by non-isothermal DSC technique, The apparent activation energy calculated by Kissinger and Ozawa equations was55.62kJ/mol、59.08kJ/mol, respectively, the frequency factor A was1.95×107s-1, the reaction order of curing reaction was0.869determined based on Crane formula, and we got the n order kinetic equation: but the n order model deviated significantly from experimental data and could not predict curing process. By T-β extrapolation, we could get that the gelation temperature Tgel、the curing temperature Tcure and the post treatment temperature Ttreat of the curing process were65.57℃、100.37℃and136.06℃, respectively. The average value of the Ea calculated by the Malek isoconversional method was35.43kJ/mol when the degree of curing reaction a is among from0.2to0.8, and the reactivity of the novel polyamide is higher. With autocatalytic mechanism model we could get the kinetic equation: compared to n order kinetic equation, the DSC curves got from the autocatalytic model could well agree with that of experiment at the lower heating rate of10K/min.