无卤阻燃丙烯腈共聚物的制备及性能

以K₂S₂O₈-NaHSO₃ 氧化还原体系为引发剂, 采用水相沉淀自由基聚合法合成丙烯腈(AN)-醋酸乙烯酯(VAc)无规共聚物[P(AN-co-VAc)], 然后在KOH水溶液中进行P(AN-co-VAc)中VAc单元的选择性水解, 再与磷酸和尿素进行磷酰化反应, 制备无卤阻燃丙烯腈共聚物. 用核磁共振氢谱(¹H NMR)、傅里叶变换红外光谱(FTIR)、差示扫描量热(DSC)和热重分析(TGA)对聚合物结构及热性能进行表征, 用凝胶渗透色谱(GPC)测定了P(AN-co-VAc)的分子量及其分布, 并利用FTIR和扫描电子显微镜(SEM)对无卤阻燃丙烯腈共聚物的炭残渣进行分析. 结果表明, VAc与AN发生共聚反应, 制得了P(AN-co-VAc), 随着KOH水溶液pH值的增大, P(AN-co-VAc)中VAc单元迅速水解; DSC分析结果表明, 随着共聚物中VAc单元含量的增大, 共聚物的环化放热分解峰值温度(T_p)增大, 当VAc单元的质量分数为25%时, T_p最大值高达328 ℃, 而阻燃丙烯腈共聚物的T_p高达340 ℃; TGA分析结果表明, 阻燃共聚物在800 ℃时的炭残渣量高达55%以上, 远高于P(AN-co-VAc)的41%, 具有良好的成炭性; 炭残渣的FTIR及SEM结果表明, 阻燃丙烯腈共聚物的阻燃属于凝聚相阻燃.

Preparation and Properties of Halogen-free Fire Retardant Acrylonitrile Copolymer

Acrylonitrile(AN)-vinyl acetate(VAc) copolymer [P(AN-co-VAc)] was synthesized via aqueous phase precipitated radical copolymerization of AN and VAc using K₂S₂O₈-NaHSO₃ as initiator. The VAc unit of P(AN-co-VAc) was selectively hydrolyzed with KOH aqueous under different pH values. The halogen-free fire retardant AN copolymer was prepared by the phosphorylation reaction among phosphoric acid, urea and the hydrolyzed P(AN-co-VAc). The structure of AN copolymer was characterized by nuclear magnetic resonance hydrogen spectrum(¹H NMR), Fourier transform infrared spectroscope(FTIR), and the thermal property of them was studied by differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA). The number-average molecular weight(M_n) and polydisperisity index(PDI) of the obtained P(AN-co-VAc) were determined by gel permeation chromatography(GPC). The char residue of the halogen-free fire retardant AN copolymer was analyzed by FTIR and SEM. The results show that AN is really copolymerized with VAc and P(AN-co-VAc) can be synthesized successfully. VAc unit is quickly hydrolyzed with the increase of pH. DSC indicates that with the increase of mass fraction of VAc in P(AN-co-VAc), the temperature of cyclic exothermic peak(T_p) improves, and T_p reaches to 328 ℃ with the mass fraction of VAc being 25%, while T_p of fire retardant AN copolymer can be 340 ℃. TGA demonstrates that the char residue of fire retardant AN copolymer at 800 ℃ is 55%, which is higher than that of P(AN-co-VAc) being 41%, it fully proves that fire retardant AN copolymer has good char forming capability. The fire retardant mechanism of fire retardant AN copolymer belongs to condensed phase flame retardant mechanism.