Fabrication of Expanded Ethylene–Propylene–Butene-1 Copolymer Bead
2022
Guo, Peng | Xu, Yaohui | Lyu, Mingfu | Zhang, Shijun
Ethylene–propylene–butene-1 ternary copolymer (TPP) and ethylene–propylene copolymer (EPC) were fabricated to produce expanded polypropylene (EPP) beads through batch foaming followed by steam-chest molding. The microstructure and thermal behaviors of both TPP and EPC were investigated by nuclear magnetic resonance, gel permeation chromatography, wide-angle X-ray diffraction, analytical temperature rising elution fractionation, and differential scanning calorimetry. EPP beads made of TPP and EPC were prepared by an autoclave batch-foaming process using compressed CO₂ as the blowing agent. Polypropylene micropellets (average diameter is approximately 1 mm) were obtained with an underwater micropelletizer system, which shortens the CO₂ diffusion distance. The effects of CO₂ content on the melting temperature of two types of polypropylene were studied. A magnetic suspension balance was used to measure the solubility of CO₂ in semimolten PP. The effects of introducing comonomers on the foaming processing and cell structure of EPP beads were preliminarily investigated. The addition of 1-butene played a significant role in enhancing the mechanical properties and decreasing the energy cost during both batch foaming and steam-chest molding with reduced carbon dioxide emissions.
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