METHOCEL™ cellulose ethers are used in PVC polymerization as primary and secondary suspension agents.
Generally low-viscosity grades of METHOCEL™ hydroxypropyl methylcellulose (HPMC) polymers are used for PVC suspension processing.
This in-depth review of the performance of METHOCEL™ in PVC processing includes a review of PVC particle morphology, the chemistry of the ethers, solution preparation guidelines, polymerization process factors and additional literature references.
A powerful combination of thermal gelling and IFT reduction
Aqueous solutions of METHOCEL™ reduce the interfacial tension (IFT) of the vinyl chloride monomer, facilitating dispersion and yielding smaller droplets. The ethers form a skin at the interface, preventing the droplets from coalescing. They then dehydrate on heating, forming a gel that strengthens the protective film further.
Compatibility, flexibility and control
Vinyl chloride monomer polymerization using METHOCEL™ alone allows the production of many PVC polymer grades of various grain sizes, porosities and morphologies. METHOCEL™ cellulose ethers can also be combined with secondary suspending agents such as hydroxypropyl cellulose or polyvinyl alcohols with low hydrolysis levels, to increase grain porosity.
Combinations with polyvinyl alcohols yield recipes with excellent grain size control over a wide range of shear profiles.