Mechanical properties of polymers and composites-Nielsen Episode 11 doc

... state and the steady-state compliance, but the star polymers also decrease the rate of stress relaxation (and creep) compared to a linear polymer (169). The decrease in creep and relaxation rate of star-shaped ... entanglements because of the many long branches, or the effect can be due to the suppression of reptation of the branches. Linear polymers can reptate, but the bu...

Ngày tải lên: 13/08/2014, 16:21

... all of the major mechanical properties of polymers: l_ Molecular weight 2. Cross-linking and branching 3. Crystallinity and crystal morphology 4. Copolymerization (random, block, and ... 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 and determ...

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

... unsymmetrical polymers. Thus syndiotactic and isoitactic poly( methyl methacrylate) have Tg values of 115 and 45 C respectively. The flexibility and cohesive energy density or polarity of each ... empirical constant of Mechanieal Tests and Polymer Transitions 15 Other Tests There are many other type's of mechanical tests in common use. One of the most import t...

Ngày tải lên: 13/08/2014, 16:21

... 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 possibilities. The nature of the mechanical ... 1948. 3. J I), Ferry. Viscoelastic properties of Polymers, 3rd ed., Wiley. New York, 1980. 4. I , n, Nielsen. Mechanical Properties of Polymers. Van N...

Ngày tải lên: 13/08/2014, 16:21

... V is measured and the Young's mod- ulus E is calculated as follows: where C and D are the width and thickness of the specimen (11, 12). This flexure test often gives values of the Young's ... 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...

Ngày tải lên: 13/08/2014, 16:21

... weight and molecular weight distribution, degree of cross-linking, and of Plasticization. For two-phase and multiphase systems such as semi- crystalline polymers and polymer blends, morphology and ... comparisons of the responses of a set of polymers (7,16,54-56). These frequency/time response curves serve to delineate the effects of changes in backbone structure (i....

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

... 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, change in the shapes of the ... unit, which consists of a Hookean spring and a Newtonian dashpot in series as shown in the insert in Figure 1. The modulus or stiffness of the spring is E, and the viscosity of...

Ngày tải lên: 13/08/2014, 16:21

... 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 expansion coefficients and ... 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...

Ngày tải lên: 13/08/2014, 16:21