Synthesis And Modification Of Phenolphthalein Benzoxazine And Bisphenol A Benzoxazine Containing Phenol Hydroxyl Group

The work in this paper included:1. New kind of benzoxazine was synthesized by choosing appropriate raw material.Novel benzoxazine(PT-ala resin) was synthesized by using phenolphthalein, allylamineand paraformaldehyde in the molar ratio of1:2:4. The curing behavior of PT-ala wasstudied by DSC and the chemical structure of PT-ala was characterized byFT-IR,1H-NMR. The thermal properties of PT-ala was studied by methods of Kissinger,Ozawa and Coats-Redfern: The thermal cure of the allyl group started at214℃and thering-opening of oxazine ring started at248℃, the thermal cure of the allyl groupincreased the crosslinking density of the resin; The thermal degradation activationenergies of PPT-ala were189.65kJ/mol and215.11kJ/mol，respectively，The results ofCoats-Redfern showed that the apparent degradation reaction order of PPT-ala is1in N2;The initial decomposition temperature of PPT-ala was about300℃, thus this resin hadgood resistance.2. We blended benzoxazine with polyurethane prepolymer to modify benzoxazine.Polyurethane prepolymers was synthesized by3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate(IPDI) and polyether polyol(PPG-1000) with a molar ratio of2:1, then we blended benzoxazine with polyurethaneprepolymer to prepare polymer blends. The chemical structure of blends wascharacterized by FT-IR. The curing behavior of blends was studied by DSC, the resultshowed that the curing temperature of the allyl group was at210℃, the ring-opening ofthe oxazine ring happened at250℃, thus blends also had high crosslink density. Thethermal properties of blends were studied by TG: The initial decomposition temperatureof PPT-ala, blends which is composed of PPT-ala and polyurethane prepolymer in themass ratio of8.5:1.5, blends which is composed of PPT-ala and polyurethaneprepolymer in the mass ratio of6:4were280℃,305℃and250℃, respectively. Thechar yield of three kinds of resin was40%,30%and20%, respectively, the result showed that appropriate content of polyurethane prepolymers could improve the thermaldecomposition temperature of benzoxazine.3. We used a macromonomer technique which copolymered polybenzoxazines withother conventional polymers to modify benzoxazine. A novel benzoxazine precursorcontaining phenol hydroxyl groups was synthesized from bisphenol A, aniline, andformaldehyde with a molar ratio of1:1:2. The chemical structure and the curingbehavior of the novel benzoxazine were characterized by FT-IR,1H-NMR and DSC, thethermal properties of this novel benzoxazine was studied by TG. The results showed thatthis novel exhibited a lower curing temperature which started at about120℃. The initialdecomposition temperature of this novel benzoxazine was at about270℃, the char yieldof the novel benzoxazine was36%, the result showed that this resin had good thermalperformance. A copolymer was synthesized by reactng a novel benzoxazine containingphenolic hydroxyl with polyurethane prepolymer which was composed of IPDI andPPG-1000. The chemical structure and the curing behavior of this compolymer wascharactered by FT-IR. The glass transition temperature of novel benzoxazine containingphenolic hydroxyl and the compolymer was charactered by DSC, the result showed theywere135℃and77℃, respectively, the results showed that this compolymer had goodflexibility. The thermal properties of novel benzoxazine containing phenolic hydroxyland the compolymer was studied by TG: The initial decomposition temperature of novelbenzoxazine containing phenolic hydroxyl and the compolymer was260℃and250℃,respectively.The char yield of novel benzoxazine containing phenolic hydroxyland the compolymer was35%and19%, respectively, the result showed that thiscopolymer also had good thermal performance.