Evaluating Cure of a pMDI-wood Bondline Using Spectroscopic, Calorimetric and Mechanical Methods

• Published in: The Journal of adhesion Vol. 76; no. 1; pp. 55 - 74
• Main Authors: Harper, David P., Wolcott, Michael P., Rials, Timothy G.
• Format: Journal Article
• Language: English
• Published: Basingstoke Taylor & Francis Group 01-06-2001; Taylor and Francis
• Subjects: Application fields; Applied sciences; Dielectric analysis; Differential scanning calorimetry; Exact sciences and technology; Polymer industry, paints, wood; Polymeric diphenylmethane diisocyanate; Saturated steam; Shear strength; Technology of polymers; Wood flakes; Wood-based materials; Wood. Paper. Non wovens; Organic isocyanate; Curing (adhesive); Adhesive joint; Shear strength; Hardwood; Adhesive bonding; Kinetics; Experimental study; Adhesive; Monitoring; Dielectric method; Dielectric relaxation
• ISSN: 0021-8464; 1563-518X; 1545-5823
• DOI: 10.1080/00218460108029617

The cure of polymeric diphenylmethane diisocyanate (pMDI)/wood bondline in a controlled saturated steam environment was monitored using micro-dielectric analysis (μDEA). Saturated steam environments were produced between 110°C and 140°C. The degree of cure calculated from μDEA was a basis for further spectroscopic, calorimetric, and mechanical evaluation. Interpretation of calorimetric and spectroscopic analysis revealed large consumption of isocyanate early in cure. However, mechanical strength, as revealed by lap-shear tests, did not develop until late in cure. Low lap-shear strengths and a plateau in conversion rates were detected for samples pressed at 110° and 120°C. Several components of the analysis suggest that low temperature cure may result in crystal formation, leading to diffusion controlled cure.