Thermal expansion of the crystal lattice of novel thermoplastic polyimides
Thermal expansion of the crystal lattice of novel thermoplastic polyimides
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新型热塑性聚酰亚胺晶格的热膨胀
DOI：
10.1002/polb.1995.090330608
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
P. Cebe
中科院分区：
文献类型：
--
作者：
M. Brillhart;P. Cebe
测量了两种半结晶热塑性聚酰亚胺的晶格热膨胀系数。使用25°C至325°C的高温WAXS研究了NEW-TPI和LARC-CPI聚酰亚胺。为了检查c轴的可能变化，我们实验室开发的一种新方法用于创建高度定向的样品。在回流温度下在NMP中处理膜，洗涤，然后在约束下干燥。以这种方式处理的膜是高度取向的，c轴优先沿膜法线沿着排列。这种取向的优点是，它允许使用反射模式WAXS检查许多类型（00 l）的反射，以确定c轴的温度变化。在NEW-TPI或LARC-CPI中没有观察到c轴晶格参数作为温度的函数的系统移位。LARC-CPI的c轴热膨胀系数小于8×10 - 6/ o C，而NEW-TPI的c轴热膨胀系数可能为弱负值。根据未取向薄膜的WAXS，推导出a和B晶格参数随温度的系统变化。将温度T下的这些晶胞参数与它们在0°C下的值相关联的线性CTE为：NEW-TPI a= 7.82（1+ 93 × 10 - 6 T）B= 6.36（1+ 60 × 10 - 6 T）; LARC-CPI a= 8.06（1+ 117 × 10 - 6 T）B= 6.12（1+ 75 × 10 - 6 T）。
Measurements of the coefficient of thermal expansion (CTE) of the crystalline lattice of two semicrystalline thermoplastic polyimides are reported. NEW-TPI and LARC-CPI polyimides were studied using elevated temperature WAXS from 25°C to 325°C. To examine possible shifts in the c-axis, a novel approach developed in our lab was used to create highly oriented samples. Films were treated in NMP at the reflux temperature, washed and then dried under constraint. The films treated in this manner were highly oriented, with c-axes preferentially aligned along the film normal. The advantage of this orientation is that it allows numerous reflections of type (00l) to be examined for temperature shifts of the c-axis using reflection mode WAXS. No systematic shift of the c-axis lattice parameter as a function of temperature was observed in either NEW-TPI or LARC-CPI. The c-axis thermal expansion is concluded to be smaller than 8×10 -6 / o C for LARC-CPI, and for NEW-TPI may be weakly negative. From WAXS of unoriented films, systematic shifts in the a and b lattice parameters were deduced as a function of temperature. The linear CTEs relating these unit cell parameters at temperature T to their values at 0°C are: NEW-TPI a= 7.82(1+93x10 -6 T) b= 6.36(1+60x10 -6 T); LARC-CPI a= 8.06(1+117x10 -6 T) b= 6.12(1+75x10 -6 T).