Mechanical properties of polymers and composites-Nielsen Episode 14 pptx

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

... Tg value of poly(vinyl acetate) at the rate of 0.,22 K'MPa (0.22C/atm). The' Tg value of polyfvinyl chloride) increases by 0 .14 K/MPn (f).( )14 fi C/atm). while the rate of increase ... copolymers. the distribution of A A. BB and AB sequences is important in determining Tg ( 1 0 3 . 1 0 5 . 1 0 9 ) . Random copoly mers generally do not have the same Tg values as c...

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

... 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, ... density of the material making up the beam of total mass m, P the period of the oscillation, f H the frequency of the vibrations in hertz or cycles per second, and / the r...

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

... used. When the stresses and strains become large and the stress-strain curve becomes nonlinear, simple descriptions of the response and interconversions between creep and relaxation become increasingly ... 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 viscosi...

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