Study on Effect laws of Additives on Suspension stability of Water-base Casting Coatings
Effect laws of additives on the suspension stability of water-base casting coatings were studied.In test coating formulations,the neutral bauxite was used as the aggregate,sodium tripolyphosphate and polyvinyl acetate latex as binders.When sodium bentonite of 3% was contained in coatings,with the increase of carboxy methyl cellulose(CMC),the suspension rate of coatings did not be basically improved.The amount of sodium bentonite at 5%,the rate of coating suspension was gradually rising with an increase in CMC.Adding sodium bentonite of 9%,a downward trend in the rate of coating suspension would appear with the CMC increased.Using sodium silicate as binder,if CMC had a very low dosage in coatings,an increase in the amount of sodium bentonite could not effectively heighten the suspension rate of coatings.But with an increase in the amount of adding CMC,suspension rate of coatings had risen dramatically,which indicate CMC can effectively improve the suspension stability of sodium bentonite-sodium silicate coating system.There was sodium bentonite dosage of 6 to 8% in coatings,with the CMC/sodium bentonite ratio increased from 0.025 to 0.075,coating suspension rate was rising rapidly,when the ratio from the 0.075 to 0.125,the raising of the suspension rate would be slow.