Rubber latex shrinkage

This paper discusses the properties of polymer-modified mortars with silica fume. The polymer-modified mortars using a styrene-butadiene rubber latex and an ethylene-vinyl acetate emulsion are prepared with various polymer-cement ratios and silica fume contents, and tested for flexural and compressive strengths, adhesion, water absorption and permeation, water resistance, drying shrinkage, carbonation and chloride ion penetration. The effects of the polymer-cement ratio and silica fume content on the properties of the polymer-modified mortars are e>amined. In conclusion, the addition of the silica fume causes improvements i- the compressive strength, resistance to water permeation and chloride ion penetration. However, the adhesion, resistance to water absorption and carbonation and drying shrinkage are not improved by silica fume addition. 

A modified type of natural mbber which has many processing advantages over normal sheet and crepe rubbers. It shows reduced shrinkage, reduced die swell and much better retention of dimensions especially in complicated extrusions. It is made by adding a quantity of vulcanised latex to normal latex before coagulating. See PA 80. 

These admixtures are used to increase the bond strength in repair applications, to decrease shrinkage, increase tensile strength, etc. The polymers used include latexes, redispersible polymer powders, water-soluble polymers, liquid resins, and monomers. In practieal applications, styrene butadiene rubber, polyacrylic ester and polyvinylidene chloride-vinyl chloride, methylcellulose, etc., have been used. 

A special variation of SBR latex containing terpolymerized vinyl pyridine is used in the tire industry to provide adhesion of organic fiber tire cords to rubber stock. The vinyl pyridine SBR latex is combined with resins and coated on the fiber by a dipping process, followed by a controlled temperature and tension process to set the adhesive as well as to control the shrinkage properties of the cord. 

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