Properties of Waterborne Polyurethane Adhesives: Effect of Chain Extender and Polyol Content

Authors: Rahman, Mohammad Mizanur¹; Kim, Han-Do²; Lee, Won-Ki¹

Source: Journal of Adhesion Science and Technology, Volume 23, Number 1, 2009 , pp. 177-193(17)

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Abstract:

A series of waterborne polyurethane (WBPU) adhesives were prepared with various ratios of polyol, poly(tetramethylene oxide glycol) (PTMG), and chain extender, ethylene diamine (EDA), at a fixed content of diisocyanate, 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI) and hydrophilic agent, 2,2-dimethylol propionic acid (DMPA). WBPU adhesives were characterized by IR and ¹H-NMR spectroscopies, X-ray diffraction (XRD) and gel permeation chromatography (GPC). It was found that the extent of hydrogen bonds between hard-hard segment (i.e., hydrogen bonds between the NH and carbonyl groups) increased with increasing chain extender content (decreasing polyol content). Moreover, the disordered hydrogen bond of carbonyl group (hydrogen bond of urethane groups in the interfacial region) increased with increasing chain extender content (decreasing polyol content). The cyclic urea and allophanate group, which are attributed to the side reaction and cross-linking reaction, respectively, were found above a molar ratio 0.17 of chain extender to diisocyanate. The adhesive strength was maximum with 0.95 wt% and 63.10 wt% chain extender and soft segment (PTMG), respectively (H2 sample) at room temperature for the WBPU adhesive. However, with increasing application temperature the adhesive strength decreased for all samples.

Keywords: POLYURETHANES; HYDROGEN BOND; CHAIN EXTENDER

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156856108X344667

Affiliations: 1: Division of Chemical Engineering, Pukyong National University, Busan 608-739, Korea 2: Department of Organic Material Science & Engineering, Pusan National University, Busan 609-735, Korea

Publication date: 2009-01-01