Effects of the chemical structure on the heat resistance of thermoplastic expandable microspheres

Abstract

ABSTRACT:The effects of various additional non-nitrilecontaining monomers on the heat resistance of thermoplastic expandable microspheres containing acrylonitrile and methacrylonitrile were investigated to determine the correlation between the chemical structure and expandable properties. Thermoplastic expandable microspheres were synthesized by suspension polymerization, with acrylonitrile and methacrylonitrile as the main ingredients and seven kinds of methacrylic acid derivatives, methacrylic acid, and acrylic acid as non-nitrile-containing monomers. The expandable properties, that is, the maximum expansion temperature, the expansion start temperature, and the maximum dimension change, were measured with thermomechanical analysis.For the development of heat-resistant microspheres, polymer structures with smaller functional free volumes, higher glass-transition temperatures, and higher cohesive energy densities, such as methyl acrylic acid, were applied as nonnitrile-containing monomers. Molecular structures such as OCOOH groups with strong electrostatic interactions and hydrogen-bonding forces were found to be suitable for high heat resistance.

Uma revisão sobre os processos de polimerização em suspensão

“…Os solventes permitem que se obtenham estruturas porosas, já que as pérolas de polímero obtidas através do processo em suspensão são muito pouco porosas, apresentando área específica inferior a 0.1 m 2 /g. O uso de solventes expansíveis (por exemplo, pentano em estireno, acrilonitrila e metacrilonitrila) pode permitir a produção de espuma, fazendo-se a rápida descompressão do ambiente de reação [30,71,72] . Essa técnica é usada freqüente-mente para a produção de espumas de poliestireno [71] .…”

Suspension polymerization of thermally expandable core/shell particles

“…A dispersion of Mg(OH) 2 was prepared by mixing a NaOH solution (0.65 g NaOH (s) in deionized water (12.4 g)) with a MgCl 2 solution (2.25 g MgCl 2 $6H 2 O (s) in deionized water (12.4 g)) followed by vigorous stirring for at least 0.5 h. This dispersion, together with 0.3 g of a 1 wt% solution of sodium 2-ethylhexyl sulfate (aq) was mixed with an organic phase containing 9.6 g monomer (Tables 1 and 2), isopentane (2.4 g, 20 wt% of organic phase based on monomer and blowing agent as commonly used in thermally expandable microspheres [1,4,5,21,22]) and dilauroyl peroxide (0.19 g). The mixture was emulsified using an UltraTurrax high shear mixer for 45 s at 8000 rpm.…”

“…Even though that there are a substantial number of patents regarding thermally expandable microspheres, only a limited number of studies have been published [3,[18][19][20][21][22]. Research on similar systems as those used in this study have been performed by .…”

Increased onset temperature of expansion in thermally expandable microspheres through combination of crosslinking agents

“…Kawaguchi and Oishi 15 investigated the influence of crosslinking of the polymer shell on the expansion properties and were able to correlate the expansion properties to the gel fraction and swelling ability of the polymer shell. Kawaguchi and Oishi with coworkers 13 have also been able to improve the thermal properties of TEMS, by altering the monomer composition of the polymer shell. A paper from Kawaguchi in collaboration with Ohshima and coworkers 14 investigates the correlation between the viscoelastic properties of the polymer shell and the expansion properties of the TEMS.…”