Southern pine bark

Interest in pine bark as a source of adhesive components began to accelerate following the oil crisis of 1973. Sodium hydroxide extracts of southern pine bark were successfully used in replacing up to 40% of the phenolic resin for bonding of particleboards, oriented strandboards, and composites with a flakeboard core and veneer facing (50f51). Similar results were obtained with extracts from patula pine (52). Encouraged by results of this type, the New Zealand Forest Products Ltd. Corporation expanded their radiata pine bark tannin pilot plant to full-scale operation in 1981 to produce an extract trademarked Tannaphen. This material was crosslinked with paraformaldehyde and used as an adhesive... 

Selection of the End-Joint Profile. Because the purpose of this work was to determine whether a portion of the phenol-resorcinol-formaldehyde adhesive used in structural end-joints could be replaced by tannin extracts from southern pine bark, it was necessary to use a structural end-joint profile design. The profile chosen was the design used by many U.S. plants for the manufacture of structural end-joints. A reproduction in natural size with a drawing showing the exact dimensions is shown in Figure 1. 

Extracts from southern pine bark obtained by extracting finely ground bark with 4.0% sodium sulfite and 0.4% sodium carbonate at 100 °C can be used to replace 50% of the PRF resin in a honeymoon system forbonding exterior quality structural end-joints in lodgepole pine or Douglas-fir. 

Use of southern pine bark extracts as 50% of the reactive phenolics in endjointing adhesives applied in a honeymoon system has good commercial potential. With proper plant layout and design, the installation, operation, and maintenance of radio-frequency units and their resulting high costs can be avoided. 

This work was funded by the USDA Small Business Innovation Research Grant No. 86-SBIR-8-0126. The authors thank Mr. Gary Smith for his assistance in testing specimens. Weyerhaeuser Company kindly made the end-joint test unit and provide laboratory space available. The Borden Chemical Company provided the PRF resin LT-75 and the hardener FM-260. The Chembond Company provided the resin RF-900. Boise Cascade Corporation kindly provided southern pine bark from its plywood plant at Oakdale, Louisiana. 

Four types of condensed tannins were studied in the adhesive dips 1) extracts from pecan nut pith obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, 2) purified tannins from southern pine bark, 3) extracts from southern pine bark obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, and 4) tannins extracted with acetone-water solutions from peanut skins. 

Table II. Elemental Composition and Carbohydrate Content of Sulfite Extracts from Pecan Nut Pith and Southern Pine Bark...

Authors Hamed and Chung are grateful to the Southern Forest Experiment Station, USDA Forest Service, for a cooperative grant (19-86-037) supporting this work. We thank Boise Cascade Corporation for supplies of southern pine bark, the Robertson Corporation for supplies of pecan nut pith, Associates Research Management Corporation for peanut skins, and Gen Corporation for resins and cord materials. 

Labosky P 1979 Chemical constituents of four southern pine barks. Wood Sci 12 80-85... 

Martin R E 1969 Characterization of southern pine barks. For Prod J 19(8) 23-30... 

Hemingway R W 1978 Adhesives from southern pine bark. A review of past and current approaches to resin formulation problems. In Proc Complete Tree Util Southern Pines. For Prod Res Soc Madison WI, 443-457... 

Hemingway R W, McGraw G W 1977 Southern pine bark polyflavonoids structure, reactivity, use in wood adhesives. In Proc 1977 TAPPI Forest Biol/Wood Chem Symp. TAPPI Atlanta, 261 -269... 

Southern pine bark, oak bark, pecan nut pith, and peanut hulls were selected as candidate materials in the study. Not only is there reason to believe that these may contain useful and extractable... 

Control Resin, B), Copolymer Resin of Southern Pine Bark Extracts, C), Copolymer Resin of Peanut Hull Extracts No. 1, D), Copol3mier Resin of Peanut Hull Extracts No. 2, E), Copolymer Resin of Pecan Nut Pith Extr. No. 1, and F), Copol3nner Resin of Pecan Nut Pith Extracts No. 2,... 

R. W. Hemingway, Adhesives from southern pine bark. Proceeding at Symp. on complete free utilization of southern pine. For. Prod. Res. Soc. (1978). 

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