Effects of molecular structure of aliphatic dicarboxylic ester on the properties of water-soluble polyester for warp sizing

In order to study the effects of molecular structure of aliphatic dicarboxylic ester (ADE) monomers on sizing properties and biodegradability of water-soluble polyester (WSP), pure aromatic WSP and aliphatic–aromatic water-soluble copolyesters with different ester structure using ADE monomers with various carbon chain lengths were prepared through transesterification–polycondensation. Then, the properties of the WSP were evaluated in terms of viscosity molecular weight, apparent viscosity, viscosity stability, crystallinity, adhesion to polyester fibers, tensile properties of sizing film, CODcr, and BOD5. It was found that with the decrease in carbon chain length of ADE monomers, all the sizing properties except tensile elongation of sizing film were improved, while the biodegradability of the copolyester decreased. The aliphatic–aromatic water-soluble copolyester synthesized by dimethyl malonate as ADE monomer exhibits better comprehensive application performance than any other WSP prepared and obtains the ratio of BOD5/CODcr about five times as much as the pure aromatic WSP.