Relationship of Moisture Content and Flexural Properties in 25 Commercial Hardboards

Twenty-five types of commercial hardboard were studied representing ten different companies with treated and untreated boards in 1/8- and 1/4-inch thicknesses. Three manufacturing processes–wet, semidry, and dry–were represented. The hardboard specimens were conditioned at various relative humidities to an EMC condition and then subjected to a static bending test. The several types of hardboard reached different moisture content conditions. In general, the hardboard reached EMC of 50 to 60 percent that of wood for the same temperature and humidity conditions. At RH of 85 and 90 percent and 120?F. dry-bulb temperature, the hardboard reached moisture contents from 9 to 12 percent. MOR and MOE, and work to 0.2-inch deflection increased, while work to maximum load decreased as the moisture content of the boards decreased. MOR was reached between 30 percent RH and ovendrying conditions. MOE followed the same general pattern as MOR. The statistical analysis showed considerable variation in flexural properties among individual boards of the same type and demonstrated that the majority of types of hard board studied possessed directional properties. Ovendrying hardboard for extended periods of time improved flexural properties because of the baking effect.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member