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首页> 外文期刊>Macromolecules >EPDM/PP thermoplastic vulcanizates as studied by proton NMR relaxation: Phase composition, molecular mobility, network structure in the rubbery phase, and network heterogeneity
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EPDM/PP thermoplastic vulcanizates as studied by proton NMR relaxation: Phase composition, molecular mobility, network structure in the rubbery phase, and network heterogeneity

机译：通过质子NMR弛豫研究的EPDM / PP热塑性硫化橡胶：相组成，分子迁移率，橡胶相中的网​​络结构和网络异质性

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Proton solid-state NMR T-2 relaxation analysis is used to study model oil-extended ethylene-propylene-diene rubber (EPDM) and thermoplastic vulcanizates (TPV) composed of polypropylene (PP), EPDM and oil. It is shown that the method allows selective characterization of crystalline and amorphous phases of PP, cross-linked EPDM, and oil in TPVs. The network density in the rubbery (EPDM) phase is determined in a wide range of the TPV compositions, as well as in the oil-extended EPDM vulcanizates containing different amount of oil. The entanglement density decreases with increasing oil content in oil-extended EPDM. This decrease can be described using a scaling approach. Molecular mobility of oil molecules decreases with increasing EPDM network density and is significantly lower than that of pure oil due to physical interactions with the host matrix. It is shown that the network density in the rubbery phase of TPV is composed of chemical cross-links, physical junctions at the EPDM/PP interface, and temporary and trapped chain entanglements. The density of chemical cross-links increases with the amount of cross-linker per weight unit of EPDM. The density of the physical junctions increases with increasing PP content. Crystallinity of PP in TPV is hardly affected by the TPV composition. A small fraction of oil molecules plasticizes the amorphous phase of PP and the plasticization effect is proportional to an oil: PP mass ratio in the TPV composition. Two NMR methods for improving the selectivity of the T-2 relaxation analysis to different phases of TPV are evaluated. The methods are based on the inversion-recovery experiment and double-quantum (DQ) filtering of the decay of the transverse magnetization relaxation. The DQ filtered T-2 relaxation experiment improves the selectivity of the method and could open new possibilities for characterization of the network heterogeneity in rubbery materials. Some relationships between the TPV composition, network density, and mechanical properties are shortly discussed.
机译：质子固态NMR T-2弛豫分析用于研究模型油膨胀的乙烯-丙烯-二烯橡胶（EPDM）和由聚丙烯（PP），EPDM和油组成的热塑性硫化橡胶（TPV）。结果表明，该方法可以选择性表征PP，交联的EPDM和TPV中的油的结晶相和非晶相。橡胶状（EPDM）相中的网络密度是在各种TPV组合物以及含不同量油的充油EPDM硫化物中确定的。纠缠密度随充油EPDM中含油量的增加而降低。可以使用缩放方法来描述这种减少。油分子的分子迁移率随EPDM网络密度的增加而降低，并且由于与主体基质的物理相互作用而大大低于纯油。结果表明，TPV橡胶相中的网​​络密度由化学交联，EPDM / PP界面处的物理连接以及临时和捕获的链缠结组成。化学交联的密度随每重量单位EPDM的交联剂数量而增加。物理连接的密度随着PP含量的增加而增加。 TPV中PP的结晶度几乎不受TPV组成的影响。一小部分油分子可塑化PP的无定形相，而塑化效果与TPV组合物中的油：PP质量比成正比。评价了两种用于改善T-2弛豫分析对TPV不同相的选择性的NMR方法。该方法基于反向恢复实验和横向磁化弛豫衰减的双量子（DQ）滤波。 DQ过滤的T-2弛豫实验提高了该方法的选择性，并为表征橡胶材料中的网络异质性开辟了新的可能性。简短讨论了TPV组成，网络密度和机械性能之间的一些关系。

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