Glass transition modulus-temperature relations

Modulus-temperature relations for amorphous polymers in static test reveal a sharp drop of modulus in the glass-to-rubber transition region (see Figure 1.19). Since the storage modulus G (oj) behaves like a modulus measured in a static test, it decreases in the glass transition region. However, the loss modulus G"((jj) and tan 6 go through a maximum under the same conditions. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

Tackifying resins enhance the adhesion of non-polar elastomers by improving wettability, increasing polarity and altering the viscoelastic properties. Dahlquist [31 ] established the first evidence of the modification of the viscoelastic properties of an elastomer by adding resins, and demonstrated that the performance of pressure-sensitive adhesives was related to the creep compliance. Later, Aubrey and Sherriff [32] demonstrated that a relationship between peel strength and viscoelasticity in natural rubber-low molecular resins blends existed. Class and Chu [33] used the dynamic mechanical measurements to demonstrate that compatible resins with an elastomer produced a decrease in the elastic modulus at room temperature and an increase in the tan <5 peak (which indicated the glass transition temperature of the resin-elastomer blend). Resins which are incompatible with an elastomer caused an increase in the elastic modulus at room temperature and showed two distinct maxima in the tan <5 curve. 

Measurements of heat capacity jumps at the glass-transition temperatures, Tg, in the matrix material and the composites, carried out from heat-capacity experiments, were intimately related to the extent of the mesophase thickness. Further accurate measurements of the overall longitudinal elastic modulus of the composites and the... 

Glass transition temperature is one of the most important parameters used to determine the application scope of a polymeric material. Properties of PVDF such as modulus, thermal expansion coefficient, dielectric constant and loss, heat capacity, refractive index, and hardness change drastically helow and above the glass transition temperature. A compatible polymer blend has properties intermediate between those of its constituents. The change of glass transition temperature has been a widely used method to study the compatibility of polymer blends. Normally, the glass transition temperatme of a compatible polymer blend can be predicted by the Gordon-Taylor relation ... 

Cyclopentene is readily available as a byproduct in the ethylene production. Norbornene 2-ethylhexyl carboxylate is obtained by the Diels-Alder reaction of 2-ethylhexyl acrylate with cyclopenta-diene (5). Norbornene isobornyl carboxylate, norbornene phen-oxyethyl carboxylate, and other related monomers are synthesized according to the same route. Polymers obtained from these esters exhibit excellent properties in terms of controlling the crosslinking density, the associated product modulus, and the glass transition temperature (Tg), thus allowing tailoring the properties of elastomers, plastics and composites. Other suitable monomers are summarized in Table 1.1 and sketched in Figure 1.2. 

Hartmann already pointed out that the reducing parameter B0 is equal to the compression modulus or bulk modulus K, extrapolated to zero temperature and pressure and that T0 is related to the glass transition temperature. 

Desirable properties of elastomers include elasticity, abrasion resistance, tensile strength, elongation, modulus, and processibiUty. These properties are related to and dependent on the average molecular weight and mol wt distribution, polymer macro- and microstmcture, branching, gel (cross-linking), and glass-transition temperature (Ip (see Elastomers, synthetic). 

CdO and smaller amounts of CdCU, YF3 and LaFs). The modulus relaxation spectrum has been fitted to stretched exponential function and it has been found that p has a roughly constant value in the glassy state and above Tg, it decreases rapidly. Since decoupling index also decreases rapidly above the glass transition temperature, it is suggestive of an implicit relation between and / . It is also noted that Rr Tg itself is inversely correlated to the corresponding p values and P decreases linearly with log at Tg (also see Hunt, 1994)... 

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