Halloysite nanotubes as a stabilizer: fabrication of thermally expandable microcapsules via Pickering suspension polymerization

Abstract

Core-shell thermally expandable microcapsules were prepared via Pickering suspension polymerization. Acrylonitrile (AN) and methyl methacrylate (MMA) were used as the comonomers and the halloysite nanotubes (HNTs) were used as the Pickering emulsifier. The influence of the HNT concentration, AN/MMA ratio, and types of hydrocarbon was investigated. When the HNT concentration was 0.6 wt%, the microcapsules exhibited a core-shell morphology that contained approximately 35 wt% of the blowing agents with an average particle size of 232.0 μm. Increasing the MMA contents resulted in a larger particle size and lower thermal stability. Core-shell microcapsules could be synthesized using iso-hexane, iso-octane, and n-octane, but microcapsules could not be fabricated with n-pentane. At 1 and 3 bar, the contents of the encapsulated blowing agents were 10 %, whereas the contents of the encapsulated blowing agents were approximately 35 and 60 % at 1.5 and 2 bar, respectively.

Fabrication of thermally expandable core–shell microcapsules using organic and inorganic stabilizers and their application

“…Kim et al . reported that adding a small amount of hydroquinone would minimize this effect . It can be seen from the SEM images that the TEMs were not spherical in shape, probably due to the liquid hydrocarbon in the core.…”

“…The prepared TEMs with two different type of stabilizer were tested for use as blowing agents during injection molding, in order to determine the difference between the final products. It is noted that halloysite nanotubes have not been used as steric stabilizers for TEMs …”

Simple method for preparation of thermally expandable microspheres of PMMA encapsulating NaHCO3via thermally induced phase separation

“…also prepared relatively uniform particle sizes consisting of a n ‐octane/poly(acrylonitrile‐ co ‐methyl methacrylate) core–shell structure using low‐temperature initiators by suspension polymerization. Kim et al . used halloysite nanotubes as a stabilizer to fabricate thermally expandable microcapsules via suspension polymerization.…”

Polymeric nanocapsules containing methylcyclohexane for improving thermally induced debonding of thin adhesive films

“…These thermally expandable capsules were expanded by the evaporation of blowing materials in the core through thermal treatment at temperatures above the glass transition temperature ( T g ) . The capsules were mainly synthesized using suspension polymerization to make use of polymer barrier properties for effective expansion . The physical properties of the aforementioned capsules depend on the constituent polymer; for example, polyacrylonitrile and poly(methacrylonitrile) can effectively prevent gas release and are frequently used as capsule shell components .…”