b'ASK THE EXPERTSmancefurtherthroughtheuseofVAEpolymersandtheyprovidea otherpolymerssuchasstyrene- good value point for most formula-butadiene,acrylic,andversatictions and applications.chemistries, but these are typically at a price premium to the VAEs andn The first spray-dried polymer avail-mostly valued in specialty applica- ablewasaPVA(polyvinylacetate) tions where increased performancehomopolymer. You have been famil-is a must have and tolerant to theiarwiththispolymerforyears additional cost. The vast majority ofElmersGlue.Theproblemwith tileadhesivesfunctionwellusingstraight PVA polymer is its sensitivity to water and instability in the highly alkalineenvironmentofhydrating cement. By itself, even after the PVA polymer has coalesced (dried form-ing a continuous film), exposure to water or sufficient moisture can re-emulsify the polymer resulting in loss of bond. Also, in the very alkaline, high-pHenvironmentofhydrating cement,thePVApolymerexperi-ences hydrolysis, which breaks down the polymer into the original mono-mers. Hardly any manufacturers use straight PVA polymers in their prod-ucts today. Thesecondspray-driedpolymer available was actually a copolymer (2).ItconsistedofPVA(polyvinyl acetate) with the addition of an eth-ylenemonomer.Thisproduceda copolymer that had two very good attributes. One, the PVA portion of the copolymer had very strong bond-ingcharacteristics.Thesebonding characteristics include an affinity to bond to cellulose (wood). Second, the addition of ethylene into the copoly-mer made it much more stable under thehighlyalkalineenvironmentof hydratingcement. Thisproducthas become known in the industry as an EVA(EthyleneVinylAcetate)poly-24TileLetter | August 2020'