Opacity of P(MMA-MAA)-PMMA Composite Latex System with Varying MAA Concentration
Gilbert U. Yu*, Jerry T. Dy, and Erwin P. Enriquez
Department of Chemistry, School of Science and Engineering,
Ateneo de Manila University, Loyola Heights, Quezon City, Philippines 1108
corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.
ABSTRACT
Polymer composites of core-shell morphology are commonly used in the paint industry as opacity enhancer. These are usually made of block copolymer systems wherein the core is formed from a polymer that swells in the presence of a solvent and surrounded by a high glass transition polymeric shell. Thus, upon drying, the swollen regions turn into voids while leaving a hard shell. Here, composites based on poly(methyl methacrylate-butyl acrylate) [P(MMA-BuA)] (seed stage), poly(methyl methacrylate-methacrylic acid) [P(MMA-MAA)] (second stage), and poly(methyl methacrylate) [PMMA] (third stage) were synthesized through a multistage sequential emulsion polymerization and their opacity was investigated. The second stage formulation of P(MMA-MAA) system was varied by changing the methyl methacrylate (MMA): methacrylic acid (MAA) mole composition, and the dried films of these composite latexes were characterized by infrared spectroscopy (IR), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). The AFM images and ammonium hydroxide (NH4OH) swelling studies confirmed the successful incorporation of the seed (first) stage with the second and third stage polymerization with PMMA. The differences in PMAA concentrations among the second stage polymer compositions were determined from the IR spectra and glass transition temperature (Tg) data. Investigations on the opacity and hiding power of these polymer composites were done using optical densitometry. The results show increasing absorbance, indicating increasing opacity, with increasing polymethacrylic acid (PMAA) concentration in the second stage composition.
INTRODUCTION
Multistage emulsion polymerization is a well-established technique used in preparing multiphase polymer composites with well-defined morphologies (Dimonie et al. 1997; El-Asser et al. 1997; Winnik 1997). Of the several polymer particles that one can formulate out of this process, core-shell polymers are highly investigated. These materials possess an architecture appealing for use in several industrial applications. Unlike blends of two or more polymers . . . . . . . . . .
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