Chemical treatments for improving compressive strength of linerboard at high moisture conditions

Abstract

Various chemical treatments have been investigated at the Forest Products Laboratory for improving the compressive strength of linerboard exposed at high humidities and after water-soaking. Phenolic resins have been among the more promising chemicals studied, but they vary in performance. The low-condensed water-soluble phenolic resins have given some of the highest compressive strengths, but generally caused more embrittlement of the board, as noted by low tearing resistance and folding endurance. The medium-condensed phenolic resins gave only moderate increases in compressive strength but did not produce as great a loss in other desirable properties. For maximum efficiency, most phenolic resins required heat to cure them. Resorcinol resin added to the phenolic resin mixture accelerated the cure of the phenolic resin, but the resorcinol reduced the compressive strength of the board. Melamine resins and hydrocarbon resins also improved the compressive strength, but not as much as certain phenolic resins. No improvement was noted with the latices. Both starch and protein treatments were highly effective at low moisture conditions, but rapidly lost their effectiveness at high moisture. The addition of a low-condensed type of water-soluble phenolic resin to a starch mixture gave a treatment that was nearly as effective at 90 percent relative humidity as the medium-condensed phenolic resins. The starch-phenolic treatments, however, were not as good after water-soaking as the phenolic-resin treatments.

Citation

Fahey, D. J. 1964. Chemical treatments for improving compressive strength of linerboard at high moisture conditions. Fesearch note FPL no. 084. Madison, WI : USDA, Forest Service, Forest Products Laboratory. 12 pages.