Construction of a thread coater and use of azocasein release to characterize the sealant coat porosity of fibers coated with latex biocatalytic coatings

A single-stage annular fiber coating method with co-current dry-air drying at 30 degrees C has been developed for multilayer coating of 128 mu m diame ter polyester thread (yarn) with latex films as a model for enzyme immobili zation and development of a filament biocatalytic filter. Acrylic vinyl ace tate polymer coatings were sequentially metered onto the fibers by the comb ination of a flexible squeegee and a red rubber annulus. The thread coater can operate over a range of 0.07-1.37 m/min thread velocities while deliver ing a nearly constant and reproducible polymer loading of 30.8 +/- 1.3 mg/m . A 100% polyester, 278.9 denier thread was precoated with latex to generat e an approximately 369 denier sealed filament. The filament was then coated with a latex + sulfanilamide-azocasein mixture and sealed with a polymer t op coat. The permeability of the polymer sealant top coat was characterized using entrapped azocasein as a tracer molecule and monitoring the azocasei n release upon rehydration of the coated threads. Azocasein release rate de creased with curing time at 30 degrees C until 2 days and was invariant aft er 2-3 days of curing. A 282 mOsm rehydrating solution was sufficient to su ppress increased azocasein release due to top coat blistering. No enhanceme nt in the permeability of the top coat was observed when high molecular wei ght water soluble polymers (WSPs) were used as fillers. This probably resul ts from the low WSP to latex ratio used (0.05-0.1) and the slow rate of WSP leaching compared to the release of azocasein. A method using 60-120 mesh silica was also developed to study the effect of mechanical abrasion of the coated threads as measured by azocasein release kinetics.