Effect of molecular weight of PEI on the strength and hydrophobic performance of fiber-based papers via PEI-KH560 surface sizing.

In recent years, researchers have put much attention on the improvements and upgrades of novel wet strength agent in the papermaking fields, especially in the usage of household paper. Herein, PEI M -KH560 by polyethyleneimine (PEI) and γ-glycidyl ether propyl trimethoxysilane (KH560) was synthesized with five molecular weights (Mw) of PEI at 600, 1800, 10,000, 70,000 and 750,000. Results showed that the molecular weight greatly influenced the physicochemical properties of PEI-KH560, such as the size and thermal stability. The intrinsic cationic charge of PEI-KH560 provided the bonding sites with the paper fibers, forming strengthened fiber-fiber joints. It was shown that the dry, wet strength and hydrophobicity of cellulosic paper sheets were obviously improved. When the m (PEI):m(KH560) is 1:2, the strength of papers after sizing by Mw of PEI at 600 and 1800 is the most obvious, with the dry strength increased by 227.9 % and 187.5 %, and the wet strength increased by 183.8 % and 207.8 %, respectively. The maximum hydrophobicity was found at the PEI 1800 -KH560 with the contact angle value of 130.6°. The resultant environmental-friendly agent (PEI-KH560) obtained in this work provides valuable significance for the preparation of household and food packaging paper. • Chlorine-free agents were prepared by different molecular weight of PEI and KH560. • The size and carbon residue content of PEI-KH560 were related with Mw of PEI. • PEI-KH560 significantly enhanced the wet strength of papers after surface sizing. • Mw of PEI influenced the strength and hydrophobicity of sized papers obviously. • The tensile strength was most effective at PEI M w of 600 with an increase of 227 %. [ABSTRACT FROM AUTHOR]