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首页> 外文期刊>Journal of Applied Polymer Science >Effect of the Molecular Weight between Crosslinks of Thermally Cured Epoxy Resins on the CO_2-Bubble Nucleation in a Batch Physical Foaming Process
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Effect of the Molecular Weight between Crosslinks of Thermally Cured Epoxy Resins on the CO_2-Bubble Nucleation in a Batch Physical Foaming Process

机译：分批物理发泡过程中热固化环氧树脂交联之间分子量对CO_2气泡成核的影响

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摘要

Epoxy resins (bisphenol A type epoxy resins/2-ethyl-4-methylimidazole) consisting of oligomers with different molecular weights were foamed using a temperature-quench physical foaming method with CO_2. The resulting cell morphologies could be classified into four types: non-foamed structure, cracked structure, star-shaped structure, and sphere-shaped structure. The effects of the gel fraction and molecular weight between crosslinks (M_C) on the cell morphology were investigated for the preparation of microcellular epoxy foams. M_C was calculated by measuring the plateau rubber modulus of the rheological properties and the weight uptake of acetone. By varying the molecular weight of the epoxy oligomers and the cure time, the MC of the epoxy was controlled to modulate the cell morphology. The experiments elucidated the threshold M_C value that permits CO_2-bubble nucleation: CO_2-bubble nucleation in the epoxy resin could be induced when the distance between the crosslinking points exceeded the critical size of bubble nucleus. Based on this information, the microcellular epoxy foam was prepared by maintaining MC above 10~4g mol~(-1) and the complex modulus above 6 × 10~8 Pa.
机译：使用温度猝灭物理发泡法，将具有不同分子量的低聚物组成的环氧树脂（双酚A型环氧树脂/ 2-乙基-4-甲基咪唑）发泡。所得的细胞形态可分为四种类型：非泡沫结构，破裂结构，星形结构和球形结构。研究了凝胶分数和交联之间的分子量（M_C）对细胞形态的影响，以制备微孔环氧泡沫。通过测量高原橡胶的流变性质和丙酮的重量吸收率来计算M_C。通过改变环氧低聚物的分子量和固化时间，可以控制环氧的MC来调节细胞形态。实验阐明了允许CO_2气泡成核的阈值M_C值：当交联点之间的距离超过气泡核的临界尺寸时，可以在环氧树脂中诱导CO_2气泡成核。根据这些信息，通过保持MC在10〜4g mol〜（-1）以上和复数模量在6×10〜8 Pa以上，制备了微孔环氧泡沫塑料。

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