Influence of resin content and pulping temperature on the formaldehyde release from medium density fibreboards (MDF)

E Roffael

doi:10.1007/s00107-012-0614-y

Abstract

Increasing the binder content from 12 % to 20 % in medium density fibreboards (MDF) using a slightly melamine modified (3 % melamine) UF-resin of a molar ratio F:U of 1:1 causes a decrease in the formaldehyde release from the boards prepared under the same conditions. The formaldehyde emanation was measured using the perforator (EN120) and the flask method (EN 717-3) after a reaction period of 3 h and 24 h. The results apply for boards made from thermo-mechanical pulps (TMP) prepared by pulping wood at 140 °C and 175 °C. The pulping temperature of wood also impacts the formaldehyde release from MDF prepared therefrom. Ascending the pulping temperature from 140 °C to 175 °C has a positive, but less significant influence on the formaldehyde release compared to that of increasing the binder content from 12 % to 20 %. Insofar, it becomes evident from the results that the conclusions drawn in the literature pertaining to the influence of resin content in case of high molar ratio resins do not necessarily apply to low molar ratio resins.

Highlights

Urea formaldehyde resins (UF-resins) are the main binders used in the wood-based panels industry
The results clearly indicate that by using high molar ratio resins of F:U 1.6:1 increasing the binder content between 5 % and 12 % leads to a remarkably higher perforator value; by using F:U resins of 1.4:1 the influence of resin level, was found to be too insignificant over the range of binder content between 5 % and 12 %
Efforts were in vain to find literature systematically covering the influence of resin content on the formaldehyde release in particle- or fibreboards bonded with very low formaldehyde UF-resins of molar ratio F:U of 1:1 or lower

Summary

Introduction

Urea formaldehyde resins (UF-resins) are the main binders used in the wood-based panels industry. Increased awareness of ecology and clean indoor requirement boosted research activity to reduce the formaldehyde emanation from wood-based composites and resulted in the development of UF-resins of extremely low molar ratio (F:U) to be used as a bonding agent. The results clearly indicate that by using high molar ratio resins of F:U 1.6:1 increasing the binder content between 5 % and 12 % leads to a remarkably higher perforator value; by using F:U resins of 1.4:1 the influence of resin level, was found to be too insignificant over the range of binder content between 5 % and 12 %. Efforts were in vain to find literature systematically covering the influence of resin content on the formaldehyde release in particle- or fibreboards bonded with very low formaldehyde UF-resins of molar ratio F:U of 1:1 or lower

Experimental work

Results and discussion

Conclusion