Thermally insulating low-density structural wooden composite

Abstract

Wood-based composites, and methods for their manufacture, are provided. The composites include oriented wooden strands and cured bonding resin connecting adjacent strands. The composites are relatively low-density, having an average dry density of the wooden composites of about 15-28 pounds per cubic foot (pcf). The unique composition of the composites provide improved structural and insulating (thermal and acoustic) properties when compared to traditional engineered wood products (e.g., oriented strandboard).

The embodiments in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A composite having a thickness dimension, comprising:
 a compressed plurality of wooden strands, each having length, width, and thickness dimensions, wherein the wooden strands are oriented such that the length and width dimensions are each orthogonal to the thickness dimension of the composite; and   cured bonding resin structurally connecting the plurality of wooden strands;   wherein the average dry density of the wooden composite is from about 15 to about 28 pounds per cubic foot.   
     
     
         2 . The composite of  claim 1 , wherein the composite consists essentially of the wooden strands and the cured bonding resin. 
     
     
         3 . The composite of  claim 1 , wherein the wooden strands are selected from the group consisting of alder, aspen, basswood, eastern cottonwood, hemlock, black poplar, yellow poplar, lodgepole pine, red pine, sugar pine, white pine, juvenile southern yellow pine, fir, and combinations thereof. 
     
     
         4 . The composite of  claim 1 , wherein the wooden strands have a thickness of from about 0.010 inches to about 0.150 inches. 
     
     
         5 . The composite of  claim 1 , wherein the wooden strands have a thickness of from about 0.015 inches to about 0.050 inches. 
     
     
         6 . The composite of  claim 1 , wherein the length of the wooden strands is from about 0.25 inches to about 8.0 feet. 
     
     
         7 . The composite of  claim 1 , wherein the length of the wooden strands is from about 0.25 inches to about 7.0 inches. 
     
     
         8 . The composite of  claim 1 , wherein the width of the wooden strands is from about 0.100 inches to about 2.0 inches. 
     
     
         9 . The composite of  claim 1 , wherein the width of the wooden strands is from about 0.25 inches to about 1.50 inches. 
     
     
         10 . The composite of  claim 1 , wherein the width and length of the wooden strands are each at least ten times greater than the thickness of the wooden strands. 
     
     
         11 . The composite of  claim 1 , wherein the length of the wooden strands are greater than the width of the wooden strands. 
     
     
         12 . The composite of  claim 1 , wherein the cured bonding resin is selected from the group consisting of cured resins of phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, epoxy, polyurea, polyurethane, and combinations thereof. 
     
     
         13 . The composite of  claim 1 , wherein the cured bonding resin is from about 1.0 wt % to about 20.0 wt % of the composite. 
     
     
         14 . The composite of  claim 1 , wherein the thickness of the composite is at least five times smaller than each of a width dimension and a length dimension of the composite. 
     
     
         15 . The composite of  claim 1 , wherein the thickness of the composite is from about 0.1 inches to about 5.5 inches. 
     
     
         16 . The composite of  claim 1 , wherein the composite has a thermal resistance value in the thickness dimension of greater than 0.9 h·ft 2 F/BTU with a corresponding dry strand basis weight of about 1.5 lb/ft 2 . 
     
     
         17 . The composite of  claim 1 , wherein the composite has an internal bond strength of greater than about 20 PSI. 
     
     
         18 . The composite of  claim 1 , wherein the composite has a dry specific gravity of about 0.45 or less. 
     
     
         19 . The composite of  claim 1 , wherein the composite is an oriented strandboard. 
     
     
         20 . The composite of  claim 1 , wherein the composite is one layer in an assembly comprising a plurality of layers of composites formed from wooden strands and cured bonding resin, wherein at least two of the plurality of layers differ in composition in at least one characteristic selected from the group consisting of wooden strand type, wooden strand dimension, wooden strand orientation, bonding resin type, bonding resin amount, ratio of wooden strand to bonding resin, presence of an additive, and type of additive. 
     
     
         21 . The composite of  claim 1 , wherein the average dry density of the wooden strands within the composite is from about 15 to about 26 pounds per cubic foot. 
     
     
         22 . The composite of  claim 1 , wherein at least 50% the wooden strands are selected from the group consisting of alder, aspen, basswood, eastern cottonwood, hemlock, black poplar, yellow poplar, lodgepole pine, red pine, sugar pine, white pine, juvenile southern yellow pine, fir, and combinations thereof.