Styrene-butyl Acrylate Copolymers Research Articles

Crosslinking ability of styrene—butyl acrylate copolymer latices functionalized with glycidyl methacrylate

Styrene—butyl acrylate copolymers functionalized with glycidyl methacrylate have been produced by emulsion polymerization using either a batch terpolymerization process or a semi-continous process, in some cases with delayed addition of the glycidyl monomer. The location of the epoxy groups has been studied by surface analysis using soap adsorption methods, and also by kinetic analysis of the results of titration with HCl. It has thus been possible to analyse the distribution of the epoxy groups inside the particle. The crosslinking reaction was carried out with hexamethylene diamine introduced into the latex just before use; film formation was by simple water evaporation and was followed by maturing of the films for up to 6 weeks at room temperature or by thermal treatment for 12 h at 100 °C. The crosslinking process was followed by swelling experiments or by measurement of the mechanical properties. These mechanical properties are very dependent upon the radial distribution of the glycidyl monomer units, which is itself governed by the polymerization process. The material may be viewed as a highly crosslinked network with soft, poorly crosslinked, inclusions.

Structure-property relationships in styrene-butyl acrylate emulsion copolymers: 2. Viscoelastic properties of latex films-experimental results and simulation

Dynamic mechanical properties as a function of temperature (−100 to 130°C) have been investigated on films made from styrene-butyl acrylate copolymer latexes prepared by emulsion polymerization using three different processes and various comonomer compositions ( 25 75 , 50 50 , 75 25 ) so as to obtain different particle morphologies. With the homogeneous copolymers, it was found that the variation of the viscoelastic properties vs. the composition can be modelled with a linear law, which shows the similarity, at a molecular level, between a two-phase composite and a homogeneous copolymer. In the case of core-shell or multilayered latex particles, thermomechanical analysis of the corresponding films suggests that two or three phases exist; the nature and the composition of the matrix and inclusion phases were deduced from the simulation of the experimental data using a self-consistent composite model based on Kerner's equation adpated by Dickie for a strain model.

Chain Conformation and Surface Characteristics of Polymers

Abstract Films of styrene-butyl acrylate copolymers when pre-conditioned in polar or non-polar media, have been used for measurements of critical surface tension, for retention volume measurements by inverse gas chromatography, and as adhesives in joints with aluminium sheet. It has been shown that large variations in surface tension, and particularly in the non-dispersive force contribution, are generated by exposing the polymer to diverse media. Specific retention volumes indicate that the copolymer surface becomes enriched in polar groups when exposed to polar media including water and formamide. The peel strength of Al-polymer joints can be roughly doubled when the polymer surface is pre-conditioned in polar rather than in non-polar media. The magnitude of property variations diminishes with increasing content of the acrylic moiety in the polymer. The results are interpreted as showing that the surface conformation of polymer chains is such as to diminish or enrich the surface concentration of polar moieties, depending on whether the polymer is in contact with polar or non-polar media. The proposed surface re-conformation appears to be reversible, and to proceed by diffusion-dependent rate processes. This evidence elaborates on the importance of attenuated responses in macromolecules to physico-chemical forces, and on the consequences of these responses to bulk as well as surface and interfacial properties of the polymer.

Effect of synthesis conditions on the rheological properties of styrene butyl acrylate copolymers

AbstractThe chemical and physical properties of synthetic polymers depend strongly on the polymerization process. This fact is even more determinant when dealing with copolymers. Styrene/butyl acrylate copolymers were synthesized using an emulsion copolymerization process. The amount of initiator, emulsifier, and transfer agent were varied in a systematic way in order to establish the relationship between polymerization conditions and rheological properties of the molten copolymers. Rheological and molecular weight results show that the different polymerization conditions have important effects on the properties of the final copolymers mainly through the development of different sequence distributions of the monomeric units in the copolymer chain. These results have been interpreted in terms of the kinetic mechanisms that explain the emulsion copolymerization processes. Furthermore, the rheological characterization is used as an additional tool in establishing the different structure of the resulting copolymers.

Nonuniformity in Thin Polymer Films

Abstract Thin polymer films solidified from solutions can display a broad range of barrier and mechanical properties, depending on the quality of the solvent and the initial polymer concentration. These findings apply specifically to polymers containing polar groups, exemplified in this work by polymethyl methacrylate and a styrene-butyl acrylate copolymer, but not to polymers like polystyrene. In the former two cases it has also been shown that very different surface tensions exist at the air and the substrate interface, provided the films were solidified against high surface energy solids. These observations have been attributed to the ability of polar-group-containing polymers to adopt various chain conformations at and near interfaces, these conformations reflecting interactions between polymer and solvents and between polymer and substrate. An additional contribution is attributed to the degree of chain entanglement persisting in solutions. The measured properties often pertain to metastable states of the films, and the findings thus indicate the existence of a thermodynamic driving force for the time-dependent change (aging) in properties of protective films.

The size analysis of polymer latices by electron microscopy using freeze‐etched preparations

AbstractA range of styrene–butyl acrylate copolymer latices has been studied in the electron microscope, using the freeze‐etching method of specimen preparation. This involves the rapid freezing of a small specimen, fracture of the frozen block, followed by replication of the fracture surface. The process of freezing rapidly to liquid air temperatures minimizes deformation of “soft” latex particles and allows their size to be determined. Certain latices were also investigated using a conventional method of specimen preparation, involving size measurements on dried, deformed particles. The particles observed in freeze‐etched preparations appeared to have slightly smaller diameters.