Polysulfide latex polymer

Monomer conversion (79) is followed by measuring the specific gravity of the emulsion. The polymerization is stopped at 91% conversion (sp gr 1.069) by adding a xylene solution of tetraethylthiuram disulfide. The emulsion is cooled to 20°C and aged at this temperature for about 8 hours to peptize the polymer. During this process, the disulfide reacts with and cleaves polysulfide chain segments. Thiuram disulfide also serves to retard formation of gel polymer in the finished dry product. After aging, the alkaline latex is acidified to pH 5.5—5.8 with 10% acetic acid. This effectively stops the peptization reaction and neutralizes the rosin soap (80). 

Each class of sealants has certain attributes inherent to the. polymer on which it is based These attributes often define the sealant s applications and limitations. Future developments are likely to feature the production of more silicone sealants that do not pick up dirt, more latex acrylic sealants that have high performance properties. Urethanes that have improved uv stability, and high performance polysulfides that are made in the United States. 

Swaab and Sutker [24] reported a modification of the foregoing procedure in which a solid, particulate, polysulfide polymer mixture is formed that is free flowing, insensitive to moisture, and redispersible in water to form a stable latex. The process involves the reaction of a Bimte salt (reaction product of sodium thiosulfate and bis(chloroethyl) ether with calcium sulfide in the presence of 5-30% of a dispersing agent [Mg(OH)2 or the sodium salt of a polyalkyl-naphthalenesulfonic acid]. 

Poly sulfide rubber was first produced in 1929, and the liquid polymers were used in sealants and as flexibilizers for epoxy adhesives around 1950. In 1952 the polysulfide sealant was introduced to the construction industry [11, p. 74]. In the 1950s the first butyl rubber caulks appeared in the construction market [11. p. 108] and latex caulks [vinyl acrylic and poly(vinyl acetate)] appeared sometime after 1956. 

CAS 1314-13-2 EINECS/ELINCS 215-222-5 Uses Pigment, vulcanizing agent in latex emulsion compds., latex rubber food-contact adhesives, resinous/polymeric coatings, paper/paperboard, closures with sealing gaskets for food containers, polysulfide polymer-polyepoxy resins, rubber defoamer in food-contact paper/paperboard... 

Polymers Resins I Butyl Rubber, Epichlorohydrin Elastomers, Ethylene Propylene Rubber, Hypalon (TM) Production, Neoprene Production, Nitrile Butadiene Rubber, Polybutadiene Rubber, Polysulfide Rubber, Styrene-Butadiene Rubber Latex 07/31/97... 

Sealants, while sharing many similarities with adhesives, tend to be made from different materials and include those based on polysulfides (often for uses in contact with fuel), silicones, polyurethanes, acrylics in both solvent-based and latex-based materials, and sealants based on butyl and fluorocarbon polymers. In addition to adhesive and sealant types, this chapter reviews methods for testing and qualifying these materials. 

---