M.S. Forestry Seminar: Marina Hornus, Maj. Prof, Dr. Brian Via

Title: Hemicelluloses extraction and nanocellulose addition as a partial replacement for non-renewable adhesives in oriented strand board

Location: Conference Hall, Room 1101A

Date: Monday, April 8, 2019

Time: 2:30 p.m.

Abstract:

Wood composites are an alternative for satisfying the increased demand for building products and there are several advantages over solid wood. This research focused on oriented strand board (OSB), which has, like other wood composites, the disadvantage of moisture absorption in the environment. Therefore, the application of wood-composite materials are mainly limited by their irreversible thickness swelling. In order to make wood-based panels usable for exterior applications, it is necessary to improve their dimensional stability in high relative humidity conditions. Thus, this work proposed a pre-treatment of wood strands to increase dimensional stability. The hypothesis was that the reduction of hemicelluloses in the wood strand, by pressurized hot water extraction, would increase the dimensional stability of the final OSB. Three different conditions were tested (120, 140, and 160 ºC at 45 min). After wood strand pre-treatment, OSB panels were manufactured and static bending, internal bond, thickness swelling, and water absorption properties were tested using the ASTM D1037 procedures. Results have shown that removal of hemicelluloses increases the dimensional stability of the final wood composite. This is attributed to less available hydroxyl groups associated with the presence of hemicelluloses. The pre-treatment at 160 °C resulted in the maximum amount of hemicelluloses extraction and, OSB produced with this pre-treated material had the best dimensional stability.

As second way to improve dimensional stability of OSB, this research investigated the use of cellulose nanofibrils (CNF) as a partial replacement for polymeric methylene diphenyl diisocyanate (pMDI), which is a non-renewable adhesive. CNF has a high modulus of elasticity; therefore, it could be an opportunity not to only partially replace pMDI, but also to reinforce it. Two experimental designs were conducted to find the optimal condition of partial replacement of pMDI with CNF. Static bending, internal bond, thickness swelling, and water absorption properties were tested using the ASTM D1037 procedures. It was found that the addition of CNF may improve thickness swell while not negatively affecting most other properties.  However, the addition of CNF did reduce internal bond and this may be acceptable for a manufacturer if the performance is still above specification. Future research is recommended to reverse the impact of water based CNF on internal bond.