Abstract
Techniques in resin blending are simple and efficient method for improving the properties of polymers, and have been used widely in polymer modification field. However, polymer latex blends such as the combination of latexes, especially the latexes with water-soluble polymers, were rarely reported. Here, we report a core-shell composite latex synthesized using methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) and glycidyl methacrylate (GMA) as monomers and ammonium persulfate and sodium bisulfite redox system as the initiator. Two stages seeded semi-continuous emulsion polymerization were employed for constructing a core-shell structure with P(MMA-co-BA) component as the core and P(EHA-co-GMA) component as the shell. Results of Transmission Electron Microscopy (TEM) and Dynamics Light Scattering (DLS) tests confirmed that the particles obtained are indeed possessing a desired core-shell structural character. Stable reactive latex blends were prepared by adding the latex with waterborne melamine-formaldehyde resin (MF) or urea-formaldehyde resin (UF). It was found that the glass transition temperature, the mechanical strength and the hygroscopic property of films cast from the latex blends present marked enhancements under higher thermal treatment temperature. It was revealed that the physical properties of chemically reactive latexes with core-shell structure could be altered via the change of crosslinking density both from the addition of crosslinkers and the thermal treatment.
Highlights
Since the idea of “particle design” was put forward by Okubo in 1980s [1,2,3,4,5], where the control of micro-phase separated structure of latex particles via controlling the distribution of hetero-functional groups in their internal particles or on their surface were the main focus, various latex particles with different morphology, such as double or multi-layers structures, were obtained via specially macromolecular designing and emulsion polymerization techniques
Two stages seeded semi-continuous emulsion polymerization were employed for constructing a core-shell morphology with hydroxyl and epoxy groups in the shell
A seeded latex was first prepared using special formulated monomers and surfactants as the core component, and the shell component consisting of designed monomers and other surfactants was added to the reaction system to produce the composite latex
Summary
Since the idea of “particle design” was put forward by Okubo in 1980s [1,2,3,4,5], where the control of micro-phase separated structure of latex particles via controlling the distribution of hetero-functional groups in their internal particles or on their surface were the main focus, various latex particles with different morphology, such as double or multi-layers structures, were obtained via specially macromolecular designing and emulsion polymerization techniques. The physical properties of latex polymer film, such as Young’s modulus, tensile strength, elongation at break and solvent resistance, are very important criteria to determine its practical applications These physical properties are closely depending on the macromolecular structure, the molecular weight, molecular inter- and intra- chemical crosslinking network structure, the size and morphology of the latex particles [10]. There were a lot of research works concerning the syntheses and characterizations of the latexes with core-shell structures, and there exist many reports related to the blends of water soluble epoxy resin with acrylate based latexes [11,12,13,14,15,16,17] In these studies, special functional groups such as epoxy, N-methoxy-acrylamide, hydroxyl and carboxyl groups were first chemically incorporated into the main chain of acrylic polymers that can provide reactive sites for crosslinking. The paper analyses the detailed network structure formed via the crosslinking reaction and its possible molecular interaction mechanism
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