I'm confused by the terms manufacturers use to describe some of the admixtures in their "modified" cementitious repair mortars. I've heard the terms polymer-modified, latex-modified, acrylic-polymer, and epoxy-modified. What are the differences between these admixtures?
All the mortars you mention fall under the general category of polymer-modified. The primary benefits of polymer modifiers are increased bond strength, reduced permeability, increased resistance to freezing and thawing, and increased flexural strength. The most common types of polymer modifiers are latexes. Although not a specific polymer, a latex is a polymer system consisting of very small spherical particles of high-molecular-weight polymers held in suspension in water by the use of surfactants. The most common polymers used in latexes for portland cement concrete are styrene butadiene, acrylics, and vinyl acetate copolymers. Styrene butadiene has been used extensively as an admixture in bridge and parking deck overlays. Acrylics and vinyl acetate copolymers often are used in manufacturers' prepackaged mortars. Epoxy emulsions, although not classified as latexes, can be mixed with portland cement concrete to provide similar benefits. Epoxy emulsions are more expensive than most latex polymers but are gaining popularity as an admixture in cementitious bonding agents and rebar coatings. Reference ACI 548.3R-95, Guide for the Use of Polymers in Concrete, American Concrete Institute, 1994.