Effect of refining pressure and resin viscosity and resin flow, distribution, and penetration of MDF fibers
The growth of medium density fiberboard (MDF) in North America has experienced robust growth over the past 20 years and is projected to increase by another 60 percent in the next 8 years. compounding this increase in demand for MDF is a raw material that is ever-increasingly lower in density and higher in juvenility. the dichotomous concept of increased demand witha poorer raw material requires a more fundamental understanding of the mechanisms involved in fiber-to-fiber stress transfer to better engineer a structural wood fiber-based composit. Our laboratory has been investigating several of the most important factors in the mechanics of MDF structural formation. This paper will present some background information on the effect of raw material juvenility on individual fiber and MDF panel stiffness ands strength. Addittional information will also be presented regarding the effect of refining pressures on fiber and panel properties. Quantitative fiber surface morphology as ascertained by scanning electron microscopy and atomic force microscopy will also be presented. This information will be vital to discuss resin behavior on individual fibers during application and pressing. The main focus of this paper is the resin-fiber interaction. Specifically, a low, medium, and high viscosity UF resin was applied to various fiber types to determine the difference in resin distribution for blowline-blended and labratory drum-blended fibers. Panels were also dissected to study the effect of pressing variables on resin flow. A qualitative analysis of resin flow on the fiver surfaces as well as penetration into the cell wall and lumen will be discussed. there will also be a discussion of future work that will quantify the effect of viscosity on resin distribution and flow for various viscosity resins related to fiber juvenility and refiner pressures.