No abstract

Wood could provide better service in some applications if it were harder and more dimensionally stable. In this study, wood-polymer composites (WPC) made with different chemical combinations were evaluated for dimensional stability, ability to exclude water vapor and liquid water, and hardness. Pine, maple, and oak solid wood were combined with different combinations of hexanediol diacrylate, hydroxyethyl methacrylate, hexamethylene diisocyanate, and maleic anhydride. Treatment slowed the rates of water vapor and liquid water absorption. Although the resultant dimensional stability was not permanent, the rate of swelling of WPC specimens was less than that of unmodified wood specimens. In addition, WPC were harder than unmodified wood. The chemical combination of hexanediol diacrylate, hydroxyethyl methacrylate, and hexamethylene diisocyanate greatly decreased wetting and penetration of water into the wood. This chemical combination also gave the hardest and most dimensionally stable WPC. In general, WPC prepared using hydroxyethyl methacrylate were harder than specimens made without hydroxyethyl methacrylate and excluded water and moisture more effectively.

No abstract

Wood-polymer composites (WPC) are made from wood and monomers that are polymerized inside the wood. Combining wood with polymer enhances the physical properties of the wood, allowing the composite to be tailored to specific applications. This paper reviews the processes and monomers used to make WPC, physical properties of WPC, and actual and potential applications. The characteristics of traditional monomers (methyl methacrylate and styrene) and new monomers are described, as are WPC surface hardness, water repellency, dimensional stability, abrasion resistance, and fire resistance. Current and potential uses for WPC range from hardwood flooring to furniture, sports equipment, parts for musical instruments, industrial applications, and construction materials.

The effects of training by whole task, forward chaining, and backward chaining methods were examined in teaching vocational rehabilitation clients the construction of three assembly tasks. Clients learned to assemble a bicycle brake, a meat grinder, and a carburetor on three successive days by the three training methods in a counterbalanced design. The percentage of responses that were errors was, on the average, more than twice as great for subjects in the whole task method as for subjects in either chaining method (which did not differ). Total time to criterion did not differ among chaining and whole methods. Slower learning subjects benefited substantially from the systematic chaining procedures.

These articles are intended to serve the readers of this Journal by calling attention to new developments in the theory, design, or availability of chemical laboratory instrumentation, or by presenting useful insights and explanations of topics that are of practical importance to those who use, or leach the use of, modern instrumentation and instrumental techniques. The editor invites correspondence from prospective contributors.

No abstract

No abstract