The pyrolysis behaviors of foam patterns have critical influences on fluid morphology and defect formation in Lost Foam Casting(LFC). The pyrolysis behaviors of expanded polystyrene(EPS) and styrenemethyl methacrylate...The pyrolysis behaviors of foam patterns have critical influences on fluid morphology and defect formation in Lost Foam Casting(LFC). The pyrolysis behaviors of expanded polystyrene(EPS) and styrenemethyl methacrylate(St-MMA) foams were compared using synchronous thermal analysis(STA), which was performed under argon atmosphere at different heating rates(from 10 to 40 K·min^(^(-1))). The degradation heat was calculated by integrating DSC curves. Results show that the calculated degradation heat of St-MMA(605.28 J·g^(-1)) was significantly lower than that of EPS(706.71 J·g^(-1)). Furthermore, the non-isothermal iso-conversional method was used to determine the pyrolysis apparent activation energies of EPS and St-MMA, and results show that the activation energy of St-MMA(200.36 kJ·mol^(-1)) was apparently higher than that of EPS(167.92 kJ·mol^(-1)). These calculated results indicate that the weight loss rate of EPS is greater than St-MMA in the pyrolysis process. In addition, the apparent activation energies at various pyrolysis stages demonstrate that the pyrolysis reactions of EPS and St-MMA may involve physical and chemical changes in the decomposition layer of the LFC process.展开更多
在氮气保护下,将三异丙氧基稀土(RE(OPri) 3,RE为铕、铽、钐、镝)直接掺杂到含0 1% (质量分数)AIBN的甲基丙烯酸甲酯(MMA)和苯乙烯(St)混合单体,形成凝胶后,在一定温度下原位聚合制备了P(MMA co St) /RE(OPri) 3复合材料,用动态机械热...在氮气保护下,将三异丙氧基稀土(RE(OPri) 3,RE为铕、铽、钐、镝)直接掺杂到含0 1% (质量分数)AIBN的甲基丙烯酸甲酯(MMA)和苯乙烯(St)混合单体,形成凝胶后,在一定温度下原位聚合制备了P(MMA co St) /RE(OPri) 3复合材料,用动态机械热分析(DMTA)、热重分析(TG)、荧光分析(FS)和环境扫描电镜(ESEM )对其进行表征。结果表明,与P(MMA co St)相比,P(MMA co St) /RE(OPri) 3的性质和微观形貌均有较大的变化。掺稀土后,共聚物的玻璃化转变温度大多稍有下降,但玻璃化前后的贮能模量、耐热性能均有不同程度的提高,动态力学曲线呈现出类似交联结构的特征,同时其微观形貌也呈现交联网络结构;FS表明,P(MMA co St)中的羰基与稀土离子的配位,导致其特征荧光红移,同时掺铕、铽的共聚物呈现铕、铽稀土离子特征荧光。展开更多
文摘The pyrolysis behaviors of foam patterns have critical influences on fluid morphology and defect formation in Lost Foam Casting(LFC). The pyrolysis behaviors of expanded polystyrene(EPS) and styrenemethyl methacrylate(St-MMA) foams were compared using synchronous thermal analysis(STA), which was performed under argon atmosphere at different heating rates(from 10 to 40 K·min^(^(-1))). The degradation heat was calculated by integrating DSC curves. Results show that the calculated degradation heat of St-MMA(605.28 J·g^(-1)) was significantly lower than that of EPS(706.71 J·g^(-1)). Furthermore, the non-isothermal iso-conversional method was used to determine the pyrolysis apparent activation energies of EPS and St-MMA, and results show that the activation energy of St-MMA(200.36 kJ·mol^(-1)) was apparently higher than that of EPS(167.92 kJ·mol^(-1)). These calculated results indicate that the weight loss rate of EPS is greater than St-MMA in the pyrolysis process. In addition, the apparent activation energies at various pyrolysis stages demonstrate that the pyrolysis reactions of EPS and St-MMA may involve physical and chemical changes in the decomposition layer of the LFC process.
文摘在氮气保护下,将三异丙氧基稀土(RE(OPri) 3,RE为铕、铽、钐、镝)直接掺杂到含0 1% (质量分数)AIBN的甲基丙烯酸甲酯(MMA)和苯乙烯(St)混合单体,形成凝胶后,在一定温度下原位聚合制备了P(MMA co St) /RE(OPri) 3复合材料,用动态机械热分析(DMTA)、热重分析(TG)、荧光分析(FS)和环境扫描电镜(ESEM )对其进行表征。结果表明,与P(MMA co St)相比,P(MMA co St) /RE(OPri) 3的性质和微观形貌均有较大的变化。掺稀土后,共聚物的玻璃化转变温度大多稍有下降,但玻璃化前后的贮能模量、耐热性能均有不同程度的提高,动态力学曲线呈现出类似交联结构的特征,同时其微观形貌也呈现交联网络结构;FS表明,P(MMA co St)中的羰基与稀土离子的配位,导致其特征荧光红移,同时掺铕、铽的共聚物呈现铕、铽稀土离子特征荧光。
