Influence of the third monomer component on the temperature-dependent crystallite modulus and tie chain fraction evaluated for ethylene-tetrafluoroethylene copolymers
Influence of the third monomer component on the temperature-dependent crystallite modulus and tie chain fraction evaluated for ethylene-tetrafluoroethylene copolymers
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第三单体组分对乙烯-四氟乙烯共聚物的温度依赖性微晶模量和连接链分数的影响
DOI：
10.1016/j.polymer.2011.12.024
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发表时间：
2012
期刊：
影响因子：
4.6
通讯作者：
K. Tashiro
中科院分区：
文献类型：
--
作者：
A. Funaki;K. Tashiro
在拉伸应力均匀分布的假设下，用X射线衍射法测定了含有和不含有短或长侧基第三单体组分的单轴取向乙烯-四氟乙烯（ETFE）交替共聚物的表观结晶模量Ecap沿链轴沿着的温度关系。在80 °C左右的低温相和高温相之间的相变温度区，二元交替ETFE共聚物的Ecap值显著降低。对于具有长C_4F_9侧基的第三共聚单体组分的ETFE共聚物样品，发现显示出与纯交替共聚物相似的温度依赖性，尽管Ecap值本身略低于后者。发现具有短CF 3侧基的ETFE共聚物在-50至50 °C的温度范围内显示出非常低的Ecapp值，因为在该温度范围内晶体结构已经转移到高温无序相。这些共聚物样品的体积杨氏模量，估计的动态粘弹性测量，进行了分析的基础上，一个复杂的力学模型，包括平行和系列序列的Ecture和Ea，其中Ecture和Ea是真正的模量的结晶和非晶区域，分别。通过估计Ectrueas温度的函数，成功地再现了这三个样品的体积模量的温度依赖性。ETFE双组分样品在低温下的Ectrue估计值为215 GPa，与平面锯齿形链构象理论计算的值230 GPa一致。平行结晶组分，这被认为是一种拉紧的连接链，以支持散装样品的机械韧性，被发现是人口较低的ETFE 2组分样品和较高的共聚物样品含有第三单体组分。这种趋势与实际观察到的耐应力开裂性或在熔点附近的高温区域中的机械韧性的趋势一致：ETFE <ETFE-CF 3 <ETFE-C4 F9。以这种方式，该样品具有重要的作用，以产生更高含量的拉紧系链，从而导致更高的抗应力开裂性。
Temperature dependence of apparent crystallite modulus along the chain axis Ecapphas been measured on the basis of X-ray diffraction measurement under the assumption of homogeneous tensile stress distribution for the uniaxially-oriented ethylene-tetrafluoroethylene (ETFE) alternating copolymers with and without the third monomer component of short or long side groups. The Ecappof the 2-components alternating ETFE copolymer was found to decrease remarkably in the phase transition temperature region between the low- and high-temperature phases at around 80 °C. For the ETFE copolymer sample with the third comonomer component of long C4F9side groups the Ecappwas found to show the similar temperature dependence to that of the pure alternating copolymer although the Ecappvalue itself was slightly lower than the latter. The ETFE copolymer with short CF3side groups was found to show remarkably low Ecappvalue in the temperature region from −50 to 50 °C since the crystal structure transferred already to the high-temperature disordered phase in this temperature region. The bulk Young’s moduli of these copolymer samples, estimated by the dynamic viscoelastic measurements, were analyzed on the basis of a complex mechanical model consisting of parallel and series sequences of Ectrueand Ea, where Ectrueand Eawere the true moduli of the crystalline and amorphous regions, respectively. The temperature dependences of the bulk moduli observed for these three samples were successfully reproduced by estimating the Ectrueas a function of temperature. The Ectrueestimated at a low-temperature, was 215 GPa for ETFE 2-components sample, which was consistent with the value 230 GPa calculated theoretically for the planar-zigzag chain conformation. The parallel crystalline component, which was assumed to be a kind of taut tie chain to support the mechanical toughness of the bulk sample, was found to be lower in population for ETFE 2-components sample and higher for the copolymer samples containing the third monomer component. This tendency is consistent with that of the actually-observed stress crack resistance or the mechanical toughness in a high-temperature region near the melting point: ETFE < ETFE-CF3 < ETFE-C4F9. In this way, the terpolymer sample has an important role to create the higher content of taut tie chains, resulting in the higher stress crack resistance.