RESEARCH
from Dr. Tore E. Timell's and Dr. 0. P. J. Glaudemans' study of white birch, a typical hardwood. ► Birch Breakdown. Most common material (about 40(.< ) in white birch is cellulose with a molecular weight of 1.5 million. Main hemicellulose is a 4 - 0 methylglucuronoxylan. It accounts for more than 3 3 f \ of the wood. The framework of the hemicellulose is a beta-1,4 linked xylan which contains groups of 4-0-mcth\ lglneuronic acid distributed along the1 chains, one for every 10 xylose units on the average. In addition, xylan from white birch also contains acetyl groups located mainly in the 3 position of the anhydroxylose units, Dr. Timell told the Division of (Cellulose Chemistry. Little is known about the small per centage of glucomannans that occur in hardwoods. But Dr. Timell says they've come up with a reasonably com plete isolation of hardwood glucoman nans. A glucomannan from white birch, say the McCill researchers, con tains about 70 beta-1,4 linked glucose and mannose residues in the ratio of 1 to 1. In comparison, softwood glu comannans contain three times as much mannose as glucose. Extractive-free inner bark of white bi-i-h contains 4 to or't pectic acid, 37'!< cellulose, and 28 r /' of a neutral unsubstituted beta-1,4 linked xylan, say the researchers. T h e remaining mixture of polysaccharides (about 4 io 5'r ) hasn't yet been studied.
Du Ponf Explores New Polymers G l y c i d y l methacrylate co polymers h a v e a w i d e r a n g e of physical properties
1 3 8 ACS NATIONAL MEETING Paint, Plastics, and Printing Ink Chemistry
A superior appliance finish . . . an easy-to-cure rubber . . . a solventresistant film . . who knows what new product may result from new polymers now being studied at Du Pont. This much is certain: These poly mers—made by copolymerizing glycidyl methacrylate ( G M A ) with vinyl and acrylate monomers—offer a variety of
BLACKBOARD SESSION. Du P o n t s Dr. J. A. Simms (right) and Dr. A. E. Brachman discuss the chemistry of glycidyl methacrylate copolymers. GMA is copolymerized with vinyl and acrylate monomers to yield a variety of multi functional epoxides which overcome limitations of conventional epoxide resins multifunctional epoxides which over come limitations found in conventional epoxide resins. Dr. J. A. Simms, Du P o n t s fabrics and finishes department, told the Division of Paint, Plastics, and Printing Ink Chemistry that the CM A copolymers have a wide range of physi cal properties, have good resistance to yellowing, are soluble in nonpolar sol vents, and can be easily prepared with molecular weights from 5000 to several million. In the free radical-catalyzed copolymerization of GMA, the epoxide groups are not affected, thus giving rise to vinyl and acrylate polymers with lat eral epoxypropyl substitution, Dr. Simms points out. The polymers can be prepared by solution, emulsion, or suspension processes. Since GMA is similar to methyl methacrylate in its copolymerization properties, Dr. Simms claims that epoxide functional copoly mers can be made with styrene, the acrylate and methacrylate esters, acrylonitrile, vinylidene chloride, and vinyl chloride. GMA copolymers are crosslinked by the same materials (dibasic acids, anhydrides, mineral acids, and amines) that are used with conventional epoxide resins. Similar curing condi tions and reactant stoichiometry also can be used, says Dr. Simms. A styrene/GMA (85/15% by weight) copolymer cross-linked with phosphoric acid is the basis of an appli
ance finish which is superior to alkyd urea-formaldehyde resin systems in hardness and resistance to discolora tion and staining, says Dr. Simms. An elastomer which can be vulcan ized with amines or dibasic acids is promised by an ethyl acrylate GMA (97 3) copolymer. Prepared in an emulsion system, the copolymer can be cured with trimene base (triethyltrimethylcnetriamine) in 30 minutes at 150' C , according to Dr. Simms. The initial tensile properties of this copoly mer, and a like (94 6) product, are similar to the values found for a com mercial acrylate rubber. Accelerated aging tests have not been made as yet. And Dr. Simms maintains that a room temperature curing film-forming system can be based on a methyl methacrylate GMA (70 30) copolymer cross-linked with aliphatic amines. The 30 r r-solids copolymer solution has a pot life of four to 24 hours, depending on the amine used. The films, says Dr. Simms, de velop excellent resistance to toluene in one week. Dr. Simms makes clear that these products are not ready for the market, but only show the wide range of possi bilities that can be achieved by copoly merizing glycidyl methacrylate with vinyl and acrylate monomers. GMA is now available in developmental quan tities, he adds. SEPT.
2 8,
1959
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