Effects of calcium and pH on spun fibres produced from plasma-alginate mixtures

When a solution of blood plasma and sodium alginate (protein: polysaccharide ratio 3:1) was extruded into coagulating baths of calcium chloride there was a rapid increase in shear strength of the fibre bundles with a rise in salt concentration up to 3% calcium chloride. Above this concentration no further increase in shear strength was observed. The ratio of plasma protein to alginate was between 0·84 and 1·1 in all tows produced from unbuffered calcium chloride baths. Extruding the dope into 5% calcium chloride baths of pH values between 2 and 8 indicated that fibre strength was independent of pH in the range 4 to 8. Below pH 4 the tows rapidly decreased in shear strength to a minimum at pH 3·5. Decreasing the pH further led to an increase in fibre strength as acid denaturated protein coprecipitated with the polysaccharide. The ratio of plasma to alginate in the tows was around 1·0 for pH values above 3·5, rapidly increasing to 2·8 at pH 2·0.