Abstract
The aim of this research was to ascertain the influences of electrolytes and hydroxypropylsulfonation on paste stabilities of cassava starch/polyvinyl alcohol blend sizes. The hydroxypropylsulfonated cassava starch was prepared via hydroxypropylsulfonation of hydrolyzed cassava starch with 3-chloro-2-hydroxypropyl sulfonic acid sodium in an aqueous medium. The stability was evaluated by measuring the initial demixing time. Before and after the addition of the electrolytes such as NaH2PO4, Na2SO4, and NaCl, the initial demixing time was 24, 20, 18, and 15 min for hydroxypropylsulfonated cassava starch/PVA1799 paste and 21, 17, 15, and 14 min for hydrolyzed cassava starch/PVA1799 one. This showed that the electrolytes accelerated the separation rates of hydroxypropylsulfonated cassava starch/polyvinyl alcohol blend pastes and hydrolyzed cassava starch/polyvinyl alcohol ones, thereby reducing the stability, and the acceleration followed the order: NaH2PO4 > Na2SO4 > NaCl. Increasing the concentration of electrolyte accelerated the separation rate and lowered the stability. The hydroxypropylsulfonation was able to reduce the separation rate and enhance paste stability. When the weight percentage of starch was fixed, with the rise in the degree of substitution from 0.011 to 0.029, the initial demixing time gradually increased, indicating the gradual decreases in the separation rates, thereby promoting the enhancement in the stability. Moreover, PVA0588 was lower than PVA1799 and PVA1788 in affecting the separation rate, which implied that polyvinyl alcohol with a lower degree of polymerization favored to promote the stability.
Highlights
Starch, due to its low cost,[1,2] renewability,[3] biodegradability, and so forth, has been widely adopted in textile sizing and paper making as a sizing agent.[4,5] Polyvinyl alcohol (PVA) is very useful in textile industry as a sizing agent.[6]
There are no visible fissures on the surfaces of hydrolyzed cassava starch (HS) granules, whereas there has been visible damage on the surfaces of hydroxypropylsulfonated cassava starch (HPSS) granules, indicating the alkaline condition and the reaction of starch hydroxyls with the chloro2-hydroxy-1-propanesulfonic acid sodium salt (CHPS-Na) reagent on the granular surfaces might be the main reason of leading to the change in the surface topology of the granules
It could be noted that blending HPSS with PVA that had a lower degree of polymerization was capable of exhibiting a stronger paste stability
Summary
Due to its low cost,[1,2] renewability,[3] biodegradability, and so forth, has been widely adopted in textile sizing and paper making as a sizing agent.[4,5] Polyvinyl alcohol (PVA) is very useful in textile industry as a sizing agent.[6] Starch and PVA are usually used in a form of blended paste for sizing cellulose/synthetic blend spun yarns.[7] the hydroxyl groups in starch molecules tend to associate with each other, and the same is the hydroxyls in PVA molecules.
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