Expansion Properties and Diffusion of Blowing Agent for Vinylidene Chloride Copolymer Thermally Expandable Microspheres.

Guiming Xie,Yongzhong Bao,Zhiyang Wang

doi:10.3390/ma13173673

Guiming Xie, Yongzhong Bao + Show 1 more

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https://doi.org/10.3390/ma13173673

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Abstract

Vinylidene chloride copolymer microspheres were synthesized by in situ suspension copolymerization of vinylidene chloride (VDC), methyl methacrylate (MMA), and/or acrylonitrile (AN) in the presence of a paraffin blowing agent. The effects of shell polymer properties including compositions, glass transition temperature (Tg), crosslinking degree, blowing agent type, and encapsulation ratio (Er) on the expansion properties of copolymer microspheres were investigated. Moreover, the diffusion properties of blowing agent in copolymer microspheres were studied. The results show that VDC-MMA-AN copolymer microspheres exhibited excellent expansion properties, and the volume expansion ratio (Ev) and the apparent density were decreased over 40 times, but it was difficult to expand for the VDC-MMA copolymer microspheres. In addition, the moderately crosslinked inside of the polymer shell enhanced the Ev more than 30 and the stable expansion temperature range (Tr) was about 30 °C by adding 0.2–0.4 wt% of divinyl benzene. The Tg of the shell polymer must be higher than the boiling point of the blowing agent as a prerequisite; the lower the boiling point of the blowing agent, the higher the internal gas pressure driven microsphere expansion, and the wider the Tr. By increasing the Er of blowing agent improved the Ev of the microspheres. The diffusion of pentane blowing agent in VDC-MMA-AN copolymer microspheres were divided into Fick diffusion and non-Fick diffusion.

Highlights

IntroductionExpandable microsphere is a polymer particle with blowing agent (low boiling point liquid paraffin or other compounds) as a core and thermoplastic polymer as a shell
Expandable microsphere is a polymer particle with blowing agent as a core and thermoplastic polymer as a shell
There were a few number of the vinylidene chloride (VDC)-methyl methacrylate (MMA) copolymer microspheres with the feeding mass ratio of 60/40 exhibiting expandable behavior

Summary

Introduction

Expandable microsphere is a polymer particle with blowing agent (low boiling point liquid paraffin or other compounds) as a core and thermoplastic polymer as a shell. Expandable microspheres are widely used in packaging, insulation, coating, decoration, etc., which can reduce the weight of products and save amount of main materials. They have been used for making a variety of foaming materials as well. A foaming agent in plastic or rubber, reduces the product density, and endows products with sound insulation or heat insulation [4,5,6,7] When they were added to coating, printing ink, the three-dimensional effect was generated or the surface characteristics of products was strengthened [8]. When they are applied in Materials 2020, 13, 3673; doi:10.3390/ma13173673 www.mdpi.com/journal/materials

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