Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): David Harper; Michael P. Wolcott; Timothy Rials
    Date: 1999
    Source: Proceedings of the second European panel products Symposium; 1998 October 21-22; Llandudno, Wales, UK.Gwynedd, Wales, UK: 193-204.
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (204 KB)

    Description

    The cure of polymeric 4-4? diphenylmethane diisocyanate, PMDl, in wood composite manufacturing has been the subject of much research. The exact contribution of polyurethane, polyurea, and polyurete formation to PMDI/wood bonding is still debated. This study foregoes the mechanism controversy and studies the cure from a panel consolidation process. Micro-dielectric analysis, mDEA, was utilized to monitor the cure of PMDI in a controlled environment of heat, steam, and pressure simulating those encountered during wood composite manufacturing. A small steam-generating chamber was mounted to a universal testing machine that produced saturated steam environments between 110° and 140°C. The degree of conversion calculated from mDEA provided a basis for further spectroscopic, calorimetric, and lap-shear analysis. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a large consumption of isocyanate early in cure. However, lap-shear analysis showed that mechanical strength did not develop until late in cure. Low ultimate lap-shear strengths and a plateau in conversion rates were detected for bondlines cured at 110° and 120°C. These characteristics may indicate a transition to diffusion-controlled reaction resulting from a vitrification effect such as crystallization. A phenomenological approach to composite cure kinetics was applied to model isothermal mDEA and dynamic DSC data. Models successfully predicted cure that followed analytical results. Higher activation energies were obtained for mDEA than were generated from DSC methods. The observed differences in activation energy are interpreted in terms of differing mechanisms in the progression of chemical and physical cure.

    Publication Notes

    • You may send email to pubrequest@fs.fed.us to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Harper, David; Wolcott, Michael P.; Rials, Timothy. 1999. Chemical and physical interpretation of MDI cure in saturated steam environments. Proceedings of the second European panel products Symposium; 1998 October 21-22; Llandudno, Wales, UK.Gwynedd, Wales, UK: 193-204.

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page
https://www.fs.usda.gov/treesearch/pubs/1089