Viscosity and Hydrolysis

Viscosity

Kuraray’s PVOH grades vary in viscosity, affecting adhesion strength, film forming properties, water sensitivity, and activity as a dispersing agent.

High viscosity grades have increased film and adhesive strength, better emulsion stabilizing and dispersant characteristics, less water sensitivity and higher shear viscosity in high solids coatings. These characteristics make them excellent for adhesive applications, water soluble films, and adhesives.

Hydrolysis: A Key Component for Polyvinyl Alcohol

Kuraray offers a wide range of PVOH grades that fit into four major ranges of PVOH: Partially hydrolyzed, middle hydrolyzed, fully hydrolyzed, and super hydrolyzed. PVOH that is fully or super hydrolyzed has improved water resistance compared to lower hydrolysis PVOH.  Unlike solutions of partially hydrolyzed PVOH, solutions of fully and super hydrolyzed PVOH do not foam.

The degree of hydrolysis is very important as it affects the level of water solubility or resistance, dissolving temperature, and surface tension of a solution depending on the characteristics that a customer needs.

Applications Based on Hydrolysis

Super Hydrolyzed:

water-resistant films, specialty paper applications, and adhesives

Fully Hydrolyzed:

textile finishing, paper and paperboard, adhesives, pressure-sensitive tapes, and ceramic binders

Middle Hydrolyzed:

warp-sizing for spun yarn, textile finishing, emulsifier for PVAc Emulsion and ceramic binders

Partially Hydrolyzed:

warp-sizing for spun and filament yarn, pressure sensitive, remoistening adhesive, soil stabilization, films, and emulsifier for EVA and PVAc Emulsions

KURARAY POVAL™ L Series: A Low Degree of Hydrolysis PVOH

KURARAY POVAL™ L series have a low degree of hydrolysis. However, they are completely water-soluble. At 70–80 mol% hydrolysis, viscosity in a 4% aqueous solution ranges from 5 mPas to 8 mPas. These products are very effective as protective colloids in the PVC suspension process. Kuraray also offers LM series that are completely water soluble.