Response of mat conditions and flakeboard properties to steam- injection variables

Abstract

Mat conditions of temperature and gas pressure were measured in three locations for one conventional and four steam-injection press schedules used in the laboratory scale manufacture of aspen (Populus grandidentata and Populus tremuloides) flakeboard. Two resins, phenol formaldehyde and polymeric MDI, were used. Steam-injection press schedules varied from low steam input to high steam input by adjusting steam pressure, steam time, and the density range for steam-injection during press closing. Steam-injection rapidly raises mat core temperatures as compared to conventional pressing. Temperature and gas pressure were positively correlated with the amount of steam input.

Flakeboard strength and dimensional stability properties were tested. Steam-injection pressing produced panels with superior dimensional stability as compared to conventional pressing. The high steam press schedule produced internal bond and shear strengths equal to the conventional press schedule for phenol formaldehyde. Medium steam press schedules produced superior internal bond and shear strengths to the conventional press schedule for polymeric MDI. The conventional press schedule produced superior static bending MOR strengths for both resins.

A fluorescence microscope was interfaced with a digitizing image analysis system to measure resin penetration area on flakes recovered from inside of the mat. Wood anatomy was found to be the dominating factor in creating high variablity in resin penetration area measurements, as differences could not be detected due to the press schedules or resin type.