FURTHER-STUDIES ON THE MOISTURE-RELATED PROPERTIES OF HYDROLYZED POLY(ETHYLENE-TEREPHTHALATE)

Contact angle measurements with water indicate that the hydrophilicity of poly(ethylene terephthalate) (PET) film decreased in the order PET treated with aqueous sodium hydroxide > untreated PET > PET treated with methanolic sodium methoxide. When the sodium‐methoxidetreated polyester was hydrolyzed with caustic soda, its contact angle fell, indicating that the methyl ester groups formed during the sodium methoxide reaction by a base‐catalyzed ester interchange had been the cause of the high contact angles. Thus it appears that carboxyl groups at the surface of hydrolyzed PET play an important role in determining its hydrophilicity. It appears from adsorption experiments that there is a marked increase in the surface area of PET fibers on treatment with aqueous sodium hydroxide. The increase is attributed to the presence of the pits produced by the hydrolysis. It is suggested the higher surface area leads to increased numbers of hydrophilic groups on the fiber surface causing the greater wettability observed in the caustic hydrolyzed samples. Copyright © 1990 John Wiley & Sons, Inc.