Tham khảo tài liệu 'materials handbook 15th ed - g. brady_ h. clauser_ j. vaccari (mcgraw-hill_ 2011) ww part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 490 INDIGO dense board with a specific gravity of and a tensile strength of 45 000 lb in2 310 MPa . Still another type of building board Dylite of Koppers Co. has a core of polystyrene plastic jacketed on both sides with plywood or gypsum. The material developed by . Forest Products Laboratory under the name Staypak is made by compressing veneered softwood containing no resin except that used to bond the veneers. It has a smooth satiny finish a specific gravity of to and about double the tensile and flexural strengths of birch. The color is darker than the original wood because of the flow of lignin. Hiden of Parkwood Corp. is a synthetic hardwood of about the same density and hardness as lignum vitae. It is made of birch veneers impregnated with phenolic resin and compressed to 30 of the original thickness and cured. The boards are used for tabletops cutlery handles sheet-metal forming dies and textile picker sticks. Wood impregnated with polyethylene glycol is known as Peg. This treatment is used for walnut gunstocks for high-quality rifles and for tabletops. This impregnant can be used to reduce checking of green wood during drying. Wood can also be vacuum-impregnated with certain liquid vinyl monomers and then treated by radiation or catalyst heat systems which transform the vinyl to a plastic. Methyl methacrylate or acrylic is a common resin used to produce this type of product known as wood-plastic combinations or WPCs. A principal commercial use of this modified wood is as parquet flooring and for sporting goods such as archery bows. It is produced in squares about in 14 cm on a side from strips about in cm wide and in cm thick. It has a specific gravity of . WPC material resists indentation from rolling concentrated and impact loads better than white oak. This is largely due to improved hardness which is increased 40 . Abrasion resistance is no better than that of white oak. INDIGO. Once the most important of all
