The cure kinetics of diglycidyl ether of bisphenol A （DGEBA） with hyperbranched poly （3-hydroxyphenyl） phosphate（HHPP） as the curing agent was investigated by means of non-isothermal differential scanning calori...The cure kinetics of diglycidyl ether of bisphenol A （DGEBA） with hyperbranched poly （3-hydroxyphenyl） phosphate（HHPP） as the curing agent was investigated by means of non-isothermal differential scanning calorimetry （DSC） at various heating rates. The results were compared with the corresponding results by using 1,3-dihydroxybenzene（DHB） as a model compound. The results show that HHPP can enhance the cure reaction of DGEBA, resulting in the decrease of the peak temperature of the curing curve as well as the decrease of the activation energy because of the flexible --P--O-- groups in the backbone of HHPP. However, both the activation energy of the cured polymer and the peak temperature of the curing curve are increased with DHB as a curing agent. The cure kinetics of the DGEBA/HHPP system was calculated by using the isoconversional method given by Malek. It was found that the two-parameter autocatalytic model（Sestak-Berggren equation） is the most adequate one to describe the cure kinetics of the studied System at various heating rates. The obtained non-isothermal DSC curves from the experimental data show the results being accordant with those theoretically calculated.展开更多
Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C...Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C showed a monotonous increase of crystallization temperature compared to pure PPS. However, a further increase of curing time decreased the crystallization temperature. The change in the half-crystallization time (t1/2) was similar to the crystallization temperature. Thus, the cross-linking of PPS affected crystallization behaviors significantly. To a certain extent, crosslinks acted as nucleation agents, but excessive cross-linking hindered the crystallization. Morphologies observed by polarized optical microscopy suggested that thermal curing for as little as 1 day contributed to the spherulitic structure having a smaller size, that was not observed with pure PPS.展开更多
为了研究超临界二氧化硅/聚醚砜/二烯丙基双酚A/双酚A双烯丙基醚/双马来酰亚胺(SCE-SiO_2/PES/BBA/BBE/MBMI)复合材料的固化动力学和耐热性(BBA/BBE/MBMI以MBAE表示)。利用SEM观察材料断面形貌;利用非等温DSC(差示扫描量热)法,研究复合...为了研究超临界二氧化硅/聚醚砜/二烯丙基双酚A/双酚A双烯丙基醚/双马来酰亚胺(SCE-SiO_2/PES/BBA/BBE/MBMI)复合材料的固化动力学和耐热性(BBA/BBE/MBMI以MBAE表示)。利用SEM观察材料断面形貌;利用非等温DSC(差示扫描量热)法,研究复合材料的非等温固化动力学;利用热失重分析法(TGA)分析不同SiO_2含量对材料耐热性影响。结果表明:当SCE-SiO_2和PES含量适当时,在基体中分散均匀,且断面呈现韧性断裂;根据Kissinger方程和Ozawa方程计算出复合材料的表观活化能分别为92.78 k J/mol和96.65 k J/mol,再利用Crane方程和n级动力学模型计算出固化动力学方程为:dα/dt=4.77×10~8(1-α)0.91e(-11.39/T),确定了固化工艺。当SCE-SiO_2质量分数为2%,PES质量分数为5%时,复合材料的热稳定性最好,热分解温度为445.63℃,比掺杂前提高了5.8℃。展开更多
According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructe...According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.展开更多
文摘The cure kinetics of diglycidyl ether of bisphenol A （DGEBA） with hyperbranched poly （3-hydroxyphenyl） phosphate（HHPP） as the curing agent was investigated by means of non-isothermal differential scanning calorimetry （DSC） at various heating rates. The results were compared with the corresponding results by using 1,3-dihydroxybenzene（DHB） as a model compound. The results show that HHPP can enhance the cure reaction of DGEBA, resulting in the decrease of the peak temperature of the curing curve as well as the decrease of the activation energy because of the flexible --P--O-- groups in the backbone of HHPP. However, both the activation energy of the cured polymer and the peak temperature of the curing curve are increased with DHB as a curing agent. The cure kinetics of the DGEBA/HHPP system was calculated by using the isoconversional method given by Malek. It was found that the two-parameter autocatalytic model（Sestak-Berggren equation） is the most adequate one to describe the cure kinetics of the studied System at various heating rates. The obtained non-isothermal DSC curves from the experimental data show the results being accordant with those theoretically calculated.
文摘Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C showed a monotonous increase of crystallization temperature compared to pure PPS. However, a further increase of curing time decreased the crystallization temperature. The change in the half-crystallization time (t1/2) was similar to the crystallization temperature. Thus, the cross-linking of PPS affected crystallization behaviors significantly. To a certain extent, crosslinks acted as nucleation agents, but excessive cross-linking hindered the crystallization. Morphologies observed by polarized optical microscopy suggested that thermal curing for as little as 1 day contributed to the spherulitic structure having a smaller size, that was not observed with pure PPS.
文摘为了研究超临界二氧化硅/聚醚砜/二烯丙基双酚A/双酚A双烯丙基醚/双马来酰亚胺(SCE-SiO_2/PES/BBA/BBE/MBMI)复合材料的固化动力学和耐热性(BBA/BBE/MBMI以MBAE表示)。利用SEM观察材料断面形貌;利用非等温DSC(差示扫描量热)法,研究复合材料的非等温固化动力学;利用热失重分析法(TGA)分析不同SiO_2含量对材料耐热性影响。结果表明:当SCE-SiO_2和PES含量适当时,在基体中分散均匀,且断面呈现韧性断裂;根据Kissinger方程和Ozawa方程计算出复合材料的表观活化能分别为92.78 k J/mol和96.65 k J/mol,再利用Crane方程和n级动力学模型计算出固化动力学方程为:dα/dt=4.77×10~8(1-α)0.91e(-11.39/T),确定了固化工艺。当SCE-SiO_2质量分数为2%,PES质量分数为5%时,复合材料的热稳定性最好,热分解温度为445.63℃,比掺杂前提高了5.8℃。
基金financially supported by the National Key Basic Research Program of China(2012CB821505)the Natural Science Foundation of Shandong Province(No.JQ201016)
文摘According to the vulcanization kinetic equation of natural rubber （NR） established in the isothermal situation, the numerical computation expression of the degree of cure under non-isothermal condition is constructed by means of incremental method. The description of non-isothermal in-mold vulcanization process is carried out by the finite element method. The mold-opening time, the rubber and mold temperatures, the degree of rubber cure and its distribution characteristics are numerically analyzed, by changing the key formulas and parameters in the process including the temperature of curing medium, the concentration of 2-mercaptobenzothiazole, the heat transfer manner of mold side, and the convective heat transfer coefficient of heating boundary. The quantitative results will help engineers to design proper formulas and optimize processing conditions.
