Mechanical properties of polymers and composites-Nielsen Episode 6 doc

... Thus the length of the rubbery plateau is a function of the number of entanglements per molecule, MIM e (10.54. 56. 64 ,65 ). A more appropriate picture (66 -71) considers that a randomly coiled chain ... weight and molecular weight distribution, degree of cross-linking, and of Plasticization. For two-phase and multiphase systems such as semi- crystalline polymers and poly...

Ngày tải lên: 13/08/2014, 16:21

... tests: Rigid polymers 249 E. Effect of temperature 253 F. Rale of testing and the failure envelope 2 56 G. Effect of hydrostatic pressure 2t?3 H. Effect of molecular weight and branching 265 I. Effect of ... t h e mechanical properties of polymers very complex if it were not for some general phenomena and principles that underlie all of these various properties...

Ngày tải lên: 13/08/2014, 16:21

... bewildering number of mechanical tests and testing instru- m ents. Most of these tests are very specialized and have not been officially recognized as standardized tests. Some of these tests, however, ... variety of units are used in reporting values of mechanical tests. Stresses, moduli of elasticity, and other properties are given in such units as MK.S (SI), cgs,...

Ngày tải lên: 13/08/2014, 16:21

... empirical rule and by the pressure dependence of Tg The empirical rule is (63 .64 ) where ai and ag arc (he volume coefficients of thermal expansion above and below Tg, respectively, and (he term ... expansion coefficient of the free volume. Pressure increases Tg (3 .65 -69 ). O'Reilly (65 ) found that pressure increases the Tg value of poly(vinyl acetate) at the rat...

Ngày tải lên: 13/08/2014, 16:21

... 10, 1351 (1 966 ). 23. ASTM Standards, 31, 1099 (1 969 ). ASTM STP 463 . 249 (1970). 24. ASTM Standards D648- 56, D/535 -65 T, and D 163 7 -61 , American Society for Testing and Materials, Philadelphia. ... behavior of polymers, and since these factors can be varied over a wide range, the mechani- cal properties of crystalline polymers take on a bewildering array of possi...

Ngày tải lên: 13/08/2014, 16:21

... all directions. Unoriented amorphous polymers and annealed glasses are examples of such materials. They have only one of each of the three kinds of moduli, and since the moduli are interrelated, ... applied, and L o the unstretched length of the specimen. Equation (6) also applies to and gives one of the moduli of anisotropic materials if the applied stress is paralle...

Ngày tải lên: 13/08/2014, 16:21

... effect of any change in £ ()jr Copolymers and plasticized materials often show another effect—a broadening of the transition region with a decrease in the slope of the modulus curve in the region of ... plateau. Plasticizers and Copolymerization also shift the glass transition responses of the amorphous phase of crystalline polymers. In addition, the degree of Crystallinity...

Ngày tải lên: 13/08/2014, 16:21

... elongation of the model equal to aJE x . The equation for subsequent creep recovery is where Creep and Stress Relaxation 67 Creep and Stress Relaxation 65 teresting changes occur in about one decade of ... amount of viscous creep, and in curve 111, viscous flow is a prominent part of the total creep. The same data were used in Figures 5 and 6, but notice the dramatic, cha...

Ngày tải lên: 13/08/2014, 16:21

... ratio of a viscosity to a modulus, as in the spring-dashpot model of Figure 1, but each sprint! has the same (shear) modulus, and the steady-flow viscosity T] of equation ( 16) is the sum of the ... amorphous polymers is or. less accurately, using the average value of Au from many polymers, of 4.S x H) ' K \ is the difference between the liquid and glassy volumetric ex...

Ngày tải lên: 13/08/2014, 16:21

... independence of strain and time, for SBR (up to very large strains) and a polyurethanc rubber, llavsky and Prins (60 ) and co-workers have presented similar explicit results for a series of polyurethanc ... minutes at arc postponed to Chapter 5, (61 ,66 ). Further discussions of since describes the shape of the stress-strain curve and we are dealing here with creep and st...

Ngày tải lên: 13/08/2014, 16:21