Polymers 2023 , 15 , 2876
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to 2.5% (14 to 50 lb/t) of the weight of the fabric. The spray test method of the American Association of Textile Chemists and Colorists A.S.T.M. Designation: D583-54 was used to evaluate water repellency. There was no mention of esterification reaction nor covalent bonding in the claim. In addition, the ASA application is like wax application to textile fiber for hydrophobicity, as claimed in patent 2,759,851 in 1956 by Fluck, Pluckemin, and Logan [21]. In 1963, Wurzburg and Mazzarella [1] mixed ASA with different derivatives of starch to form an emulsion. It was claimed that the application of the ASA emulsion on fiber made the sheet hydrophobic. The patent demonstrated the sizing process with the use of the ASA emulsion and the addition of alum, aluminum chloride, long chain fatty amines, sodium aluminate, polyacrylamide, animal glue, polyamide polymers, primary amine starch derivatives, secondary amine starch derivatives, tertiary amine starch derivatives, and quaternary amine starch derivatives. The author recommended to use 0.5 to 2 parts by weight of cationic starch per 1 part of the sizing agent to obtain adequate results. Different dosages from 0.25% to 2% (5 to 40 lb/t) of the sizing agent were used in 14 different examples to support the claim. Uranine dye and ink dip tests were used to prove the hydrophobicity of the sheets. There was no disclosure of covalent or ester bonding between ASA and cellulose in the patent document. Cuculo [22] at NC State University tried to esterify succinic anhydride with cellulose in 1971. First, successful results were obtained from the reaction between viscose rayon cellulose and succinamic acid. The samples were baked in succinamic acid at 136 ◦ C, 183 ◦ C, and207 ◦ C, water-washed, and then treated with 3% sodium sulfate to form sodium cellulose-hemisuccinate. The degree of substitutions for the reactions were, respectively, 0.03, 0.24, and 0.25. The author concluded that the degree of the substitution of reaction depends strongly on the reaction temperature. Second, when succinic anhydride in water was used under comparable conditions to those of the succinamic acid, the author stated that there was no evidence of ester formation. The reported reaction yield with succinamic acid was 36%, and the author mentioned that ammonia copiously evolved during the reaction. The recommended temperature using the succinamic acid is above 150 ◦ C. McCarthy and Stratton [23] studied the reaction between cotton linters pulp and ASA in 1986. In one study, the cotton linters and ASA were reacted in N,N-dimethyl formamide with triethyl amine as a catalyst. In another study, the cotton linter pulp (washed in chloroform-ethanol solution for 48 h and air dry for several hours) and a high concentration of ASA (1.5% or 30 lb/ton) were reacted. Poly(1,2-dimethyl-5-vinylpyridinium bromide), or DMVPB, was used as ASA retention aid. In both studies, FTIR data showed the formation of ester bonds, however the efficiency of these reactions was not reported. In McCarthy’s thesis in 1987 [24], the author showed by FTIR that ASA reacted with ethanol to form ester bonds. It is not known if part of the ASA formed ester bonds with ethanol rather than cellulose since the pulp was washed 48 h with chloroform-ethanol solution. Wan [25] studied the mechanism of ASA sizing in 1988 using C 14-labelled tetrade- cenyl succinic anhydride (TDSA) and tetradecenyl succinic acid (TDSAcid). TDSA and TDSAcid emulsions were made using starch as an emulsifier at a 1:3 ratio. The emulsions containing 1.3% total solid was charged to the pulp to make 60 g/m 2 hand-sheets. The C14- labelled technique was used to quantify the ASA component in the sheets after chloroform extraction. The results showed that unreacted ASA is predominantly found in the sheet and about 25% of ASA can produce sizing and is not extractable with chloroform. According to the author, the retained ASA could be explained by covalent bonding due to three reasons. First, the continuous increasing in sizing at room temperature suggests the reduction in moisture allows the ASA to react with the hydroxyls of cellulose. Second, the ASA molecule, which is under constant reorientation during the sizing process, would undergo hydrolysis if at any time the hydrophilic part of the molecule is exposed to moisture. The retained molecule can be assumed to be held by stronger irreversible bond forces. Third, the inability of the ASAcid (hydrolyzed form of ASA in the dicarboxylic acid form) to size hand-sheets demonstrates that hydrogen bonding is not the mechanism of
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