erial, which the Laboratory has named compreg, is manufactured by four companies to the extent of about a million board feet per year. It is used for electrical insulators, handles for tableware, gears, jigs, and fixtures for machine tooling operations.

A modified wood containing no resin but which is densified to a high degree has also been developed. Such material does not have the limensional stability of compreg, but does have the improved mehanical properties and, if properly made, the improved properties are permanent. This material is called "staypak." A commercial firm is experimenting with a procedure for imparting the increased density merely to the external one-sixteenth inch. Such a material, with an overall density not appreciably higher than that of normal wood, has the high surface density necessary for increased hardness. The method appears promising and should prove useful where good bearing surfaces are desired.

The Forest Products Laboratory has also developed procedures for obtaining dimensional stability by impregnating wood with certain water-soluble materials. The method is generally effective where the treated wood will not come in contact with liquid water which, of course, would dissolve the deposited material in the wood. Numerous small-volume uses are already developing, such as stabilization of gunstocks. This procedure, if properly used, also permits the drying out of old, water-logged wood items of historic interest.

In another modified wood, acetylated wood, the appearance is unchanged, but the natural affinity for moisture has been largely eliminated by destroying the moisture-adsorbing sites within wood. The surface modifications of wood or the modification of the outer plies of plywood results in greatly improved performance of painted or unpainted surfaces exposed to the weather. One commercial firm is now marketing the material.

Future potential

Several processes are available for reducing the intrinsic affinity of wood for moisture. As yet, the methods are expensive and time consuming because of the need to bring reacting chemicals deep into the wood. Further research will be aimed at developing cheaper and improved methods of stabilization that will be useful in improving the performance of a wide range of wood products.

References

1. Stamm, A. J. Modified Woods. Forest Products Laboratory Report No. 2192, 1960.

2. Stamm, A. J., and Seborg, R. M. Forest Products Laboratory Resin-Treated Wood (Impreg). Forest Products Laboratory Report No. 1380, 1960.

3. Stamm, A. J., and Seborg, R. M. Forest Products Laboratory Pesin-Treated, Laminated, Compressed Wood (Compreg). Forest Rroducts Laboratory Report No. 1381, 1960.

4. Seborg, R. M., Millett, M. A., and Stamm, A. J. Heat-Stabilized Compressed Wood (Staypak). Forest Products Laboratory Report No. 1580, 1956.

5. Stamm, A. J. Effect of Polyethylene Glycol on the Dimensional Stability of Wood. Forest Products Journal, volume 9, No. 10, 1959. 6. Tarkow, Harold, Stamm, A. J., and Erickson, E. C. O. Acetylated Wood. Forest Products Laboratory Report No. 1593, 1960.

FLAME-RESISTANT LIGHTWEIGHT PAPERS

Description and use

Resistance to flame spread is an important criterion, in many applications, for wall and ceiling surfaces. This property could be improved by the use of flame-resistant paper on, say, the surface of boards for dry-wall construction or on the surface of decorative laminates.

Flame-resistant paperboards have been produced for some time. Chemicals have been available which, although sensitive to elevated temperatures, can be applied to the board after the drying operation. Lightweight papers that absorb sufficient chemical contain such a high moisture content that they must be partially dried before they can be handled and used. During this drying operation, the flame-retardant chemicals often are lost as the water is being removed. As a result of recent research, a flame-resistant paper was produced that involves the use of an effective fire-retardant chemical to which has been added a suppressor to raise the decomposition temperature. Future potential

Plywood paneling is sometimes ruled out for use in public buildings unless at least the outer ply is fireproofed. Perhaps a thin flameproofed tissue could be applied to the outer ply surface to provide resistance to flame spread, but still not detracting from the desirable appearance of the wood.

PAPER REPLACEMENTS FOR YARNS AND THREADS

Description and use

A few twisted-paper products have been made from narrow strips of lightweight tough paper twisted to form yarns. These have been woven into seat covers, open-mesh vegetable bags, and wrappers for cotton bales.

Future potential

A number of other products can be made from twisted paper yarns, such as snow fences, sandbags, and covers for sloping areas to prevent soil erosion but permit plant growth. To increase the use of twisted paper products, research is necessary to produce a stronger and more flexible paper. Studies being conducted at the Forest Products Labortory on the reasons for paper stiffness and strength will help to improve the desirable properties of twisting papers.

PAPER SUBSTITUTES FOR TEXTILE PRODUCTS

Description and use

Woodpulp papers, because of their inherent stiffness, lack the drape characteristics of textiles and therefore, as such, are not direct substitutes. Attempts by paper manufacturers to overcome these disadvantages have directed attention toward laminated products made, for example, from two outer layers of creped tissue with an inner reinforcing layer of a suitable scrim material. These are bound together with various types of flexible water-resistant adhesives such as latices and resins. These have found limited use as bedsheets,

lay tents, and overgarments, the latter to prevent soiling of clothing. The main drawback is that the present materials lack the toughness nd wearing qualities for widespread use.

Future potential

There is a wide market for substitutes for woven textile products, uch as disposable clothing, tent materials, sleeping bags, hospital owns and sheeting, windbreaks for winter construction, and curing aats for concrete.

Research is necessary in this field to improve the strength of lightweight flexible papers. Current research at the Forest Products Laboratory on the nature and strength of fibers and fiber-to-fiber onds, as well as investigations involving the incorporation of chemials to impart both strength and flexibility, will be of substantial help n solving many of the present problems.

PULP AND PAPER FOR SOIL STABILIZATION

Description and use

The stabilization of soil on slopes in highway cuts, earthfill dams, and the like presents a difficult problem, but recently developed procelures using pulp and paper products appear well suited to a problem solution.

One newly developed product is a blanket laid on the soil. The blanket consists of several layers, including a protective layer to prevent erosion, a layer of seed, fertilizer, and germinating media; a protective layer of paper is also included that will later disintegrate and permit the seed layer to come in contact with the soil. Thus, the soil is stabilized while the vegetative cover takes root. The blanket comes in rolls that can be applied by machine.

Hydraulic equipment is already in use to apply lime, fertilizer, and grass seed. Mechanical mulch blowers are widely used for applying combinations of hay, straw, and asphalt tiedown. A recent development permits a one-step application of all components.

In this development, a slurry of wood fiber, fertilizer, and seed is hydraulically applied to the surface. The wood fiber forms a protective cover that protects against massive erosion but still permits rain to filter through. It is reported that the slurry can be applied in high winds that would interfere with the machine application of hay or straw. It is reported also that, after application, the mulch is not easily moved by wind or traffic drafts. A color, usually green, is incorporated into the slurry to aid in uniform distribution of the slurry. Future potential

Soil stabilization is important in many public works areas besides those mentioned. Faster, more economical methods of temporary stabilization and seeding will become increasingly important.

References

1. Nicar, Raymond L., and Blaser, R. E. The Use of Wood Cellulose Mulch. American Road Builder. March 1962.

2. Harper, Rex S. The Use of Wood Cellulose Fiber Mulch in Grass Seeding. Twentieth Short Course on Roadside Development Proceedings, Columbus, Ohio, 1961.

escription and use

CHEMICALS FROM WOOD

By their very nature, most public works projects-highways, public uildings, dams, and the like-make more direct use of construction aterials such as wood than of chemicals. Some chemicals, including ose from wood, do find use in direct form and indirectly, as industrial hemicals, are of great importance. These indirect uses include such road fields as the manufacture of plastics, adhesives, wood preservaves, paints, and other finishes. A few of the direct uses of chemicals btained from wood are outlines below.

Spent sulfite liquor, a byproduct of the paper industry, has been sed since the early 1900's to settle dust on unpaved roads. More ecently this material has found extensive use as a stabilizer for base ourses used in construction of highways and airport runways. This pent liquor has also found some use as a soil modifier and to some egree as a fertilizer.

Lignosulfonates, which are derived from spent liquor, have found an important new use as a additive to well-drilling muds. They lso find use in portland cement for concrete as an air-entraining agent. Entrained air in concrete greatly improves resistance to surface scaling of pavements from the use of salts to melt ice coatings. Air entrainment also reduces bleeding and segregation and increases workability, homogeneity, and yield of concrete.

Activated carbon is used in the treatment of water supplies.

Future potential

Chemicals from wood will continue to have uses such as those described. As the full potential of a wood-based chemical industry develops, additional uses will be found.

References

1. Pearl, I. A., and Rowe, J. W. Review of Chemical Utilization. Forest Products Journal, volume 10, No. 2, 1960.