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OCR for page 160

OCR for page 160
R O G E R P. K A M B O U R 1932–2008 Elected in 1992 “For pioneering investigations of the structure of crazes in glassy polymers and discovery of their importance in polymer fracture.” BY WILLIAM J. WARD ROGER KAMBOUR was a chemist at the General Electric Research and Development Center and a research professor at the University of Massachusetts. His pioneering work on crazing and fracture of glasslike thermoplastics laid the foundations for our current understanding of fracture resistance in rigid polymers. He was born April 1, 1932, in Winchester, Massachusetts, and was raised in nearby Wilmington, 17 miles north northwest of Boston. His father was a math teacher, his mother a music teacher. He was educated at Wilmington High School (where his father was principal), Amherst College (B.A., cum laude, 1954), and the University of New Hampshire (Ph.D., 1960). In August 1960, immediately after receiving his Ph.D., he joined General Electric’s Corporate R&D Center at Schenectady, New York, where he worked until his retirement some 34 years later. Throughout a long career, he remained dedicated to research and continued to publish articles in learned polymer journals, the last of them appearing in Macromolecules in 2000. From 1962 to 1980, his publications were almost exclusively about crazing and fracture. Thereafter, his output became more diverse; while still including occasional papers on crazing, it also covered flammability, polymer-polymer miscibility, stress relaxation, mobility of diluents, and polymerization of cyclic 161

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162 MEMORIAL TRIBUTES oligomers. These studies reflected both his original training as a physical chemist and his commitment to industrially relevant research. Another factor was his close collaboration with leading figures in the academic world. He spent a month at Imperial College in 1981, in a collaboration that involved the application of neutron scattering to fundamental questions concerning the miscibility of polystyrene with poly (1,4-dimethyl-2,6-phenylene ether), a topic of direct relevance to General Electric’s plastics business. Roger spent a four-month sabbatical at the Massachusetts Institute of Technology in 1991 as a visiting professor and eight months at the National Institute of Standards and Technology in 1993 as a visiting scientist. In 1994 he officially retired from General Electric, but he retained an office there and served as a research professor at the University of Massachusetts. Roger’s work on crazing had a profound effect on polymer physics. For a long time, crazes were regarded simply as small noncritical cracks. To the naked eye that is exactly what they looked like, and the words “cracking” and “crazing” were used interchangeably, especially in the terms “solvent stress-cracking” and “solvent-crazing,” which refer to craze formation in the presence of organic liquids. This phenomenon was a problem for General Electric, as a producer of both electrical appliances and Lexan polycarbonate, hence the decision to recruit a staff member to investigate it. In a 1999 publication, Roger recalled his despondency at being asked to work on a topic that appeared to be more of a trouble-shooting exercise than serious scientific research. However, his doubts were dispelled within 12 months, first by news that Spurr and Niegisch had observed solid matter inside crazes, which meant that they were not true cracks, and then by his own definitive experiments, which demonstrated that crazes are porous, load-bearing structures. By measuring the critical angle for total internal reflection from alcohol-induced crazes formed in polycarbonate under tensile stress, Roger was able to show that they consisted of 50 percent polymer and 50 percent ethanol, by volume. Furthermore, when the alcohol evaporated (quite quickly) with the specimen at constant strain, it was replaced

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163 ROGER P. KAMBOUR with 50 percent air. These tests showed that the voids were all interconnected and that craze material is homogeneous under visible light. He later showed that tensile stresses are sustained by threads only a few molecules in thickness and that crazes invariably form ahead of a crack tip in glassy polymers. Establishing a connection between fracture behavior and crazing (which could now be recognized as an energy- absorbing deformation micromechanism) represented a major advance in our understanding of mechanical properties. On reading Roger’s 1964 article on the subject, researchers in England looked for evidence of crazing in rubber-toughened polystyrene and showed that large numbers of crazes form around a loaded crack tip in this commercially important class of polymer blends, thereby explaining how adding 8 percent rubber could transform brittle PS into the “high-impact” grade known as HIPS and opening up the whole subject of toughening mechanisms in polymer blends. The formation of craze fibrils also helped explain why chain length (and therefore molecular weight) is so important in thermoplastics. Other developments included measurements of natural draw ratios for craze fibrils and their correlation with contour lengths between entanglements, studies on craze healing at elevated temperatures, and Roger’s own studies on solubility parameters as a guide to critical strains for solvent crazing. Turning from materials science to pure engineering, crack- tip crazes were soon recognized by the fracture mechanics community as ideal examples of Dugdale plastic “line zones.” Crazing is now a standard topic in textbooks on polymer science, perhaps the highest form of recognition for any scientist. Roger received a number of awards for his work. He was awarded a Coolidge fellowship, the highest award of the General Electric Research and Development Center, in 1979. He was a fellow of the American Physical Society (APS), and he won the Union Carbide Award from the American Chemical Society and the Ford Prize for Polymer Physics (jointly with E. J. Kramer) from APS. He was elected to the National Academy of Engineering in 1992.

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164 MEMORIAL TRIBUTES Perhaps the most notable mark of recognition that Roger received was an invitation from APS to contribute a short autobiographical note to one of its publications. The occasion was the centenary of APS in 1999, which the Polymer Physics Division decided to mark by collecting contributions from a select group of eminent scientists whose research had shaped polymer physics over the previous half century. The resulting article, which appeared in the Journal of Polymer Science (Part B) in 1999, contains two-page historical notes from 14 internationally renowned physicists, each a leader in his field. Roger’s name rightfully appears in this unique roll of honor. In his leisure time, Roger was a skilled cook, an enthusiastic member of several choral societies (including Amici Cantorum), and a passionate supporter of Amherst College. He was a skillful downhill skier who took his turn in the Hickory Hill Ski Patrol in New York State during the 1980s. During the summer he enjoyed sailing and canoeing. He was also active in a variety of civic activities. In all his activities, Roger displayed a well-developed sense of humor, combining serious intent with a sociable personality and a wide range of intellectual interests. Above all, Roger’s primary passion was his family. Whether attending various concerts, sporting events, or family reunions, he cheered his children and family in their achievements. Roger died on December 20, 2008. He is survived by his wife, Barbara Vivier; his daughter, Annaliese; and sons Christian and Joshua.

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