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Polymers (Basel). 2019 Aug 12;11(8). pii: E1338. doi: 10.3390/polym11081338.

In Situ Modification of Polyisoprene by Organo-Nanoclay during Emulsion Polymerization for Reinforcing Natural Rubber Thin Films.

Author information

1
Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai Campus, Songkhla 90110, Thailand.
2
School of Science and Technology, University of New England, Armidale, NSW 2351, Australia. w.kaewsakul@utwente.nl.
3
Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai Campus, Songkhla 90110, Thailand. cfellows@une.edu.au.
4
Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, 7522 NB Enschede, The Netherlands. cfellows@une.edu.au.

Abstract

Nanoclay-modified polyisoprene latexes were prepared and then used as a reinforcing component in natural rubber (NR) thin films. Starve-fed emulsion (SFE) polymerization gives a higher conversion than the batch emulsion (BE), while the gel and coagulation contents from both systems are comparable. This is attributed to the SFE that provides a smaller average polymer particle size which in turn results in a greater polymerization locus, promoting the reaction rate. The addition of organo-nanoclay during synthesizing polyisoprene significantly lessens the polymerization efficiency because the nanoclay has a potential to suppress nucleation process of the reaction. It also intervenes the stabilizing efficiency of the surfactant-SDS or sodium dodecyl sulfate, giving enlarged average sizes of the polymer particles suspended in the latexes. TEM images show that nanoclay particles are attached on and/or inserted in the polymer particles. XRD and thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)) analyses were employed to assess the d-spacing of nanoclay structure in NR nanocomposite films, respectively. Based on the overall results, 5 wt% of nanoclay relative to the monomer content utilized to alter the polyisoprene during emulsion polymerization is an optimum amount since the silicate plates of nanoclay in the composite exhibit the largest d-spacing which maximizes the extent of immobilized polymer constituent, giving the highest mechanical properties to the films. The excessive amounts of nanoclay used, i.e., 7 and 10 wt% relative to the monomer content, reduce the reinforcing power because of the re-agglomeration effect.

KEYWORDS:

elastomer; filler; latex; nanocomposite; reinforcement

PMID:
31409053
DOI:
10.3390/polym11081338
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