Dynamic mechanical thermal analysis results

Mijovic et al. analyzed the annealed blends from melts using dynamic mechanical thermal analysis and achieved similar results after an adjustment for shifting factors, AT s, as shown in Figure 7.3. The results were extended to include blends having a PVDF concentration greater than 80 wt %. It can be observed that the glass transition temperatures of the annealed blends reduce rapidly when the PVDF concentrations are above 80 wt %. 

Dynamic mechanical thermal analysis, a non-sample-destructive technique in which an oscillatory stress is applied to the sample and the resultant strain determined as a function of both frequency and temperature. Examples of this technique include thermal-ramped oscillatory rheometry and conventional dynamic thermal mechanical analysis. 

Dynamic mechanical thermal analysis of several of the norbornene functional organic resins and the silicone resins gave relatively unremarkable results. The maximum for tan 5 peaks were in good agreement with Tg detamiined by DSC. The silicone elastomer (with 35% fumed silica as reinforcing filler) exhibited a Tg of ca. -90°C and a Tm at ca. -30 C which is typical for this type of polymer. 

A more common mechanical method is dynamic mechanical thermal analysis (DMTA). DMTA is also called dynamic mechanical analysis (DMA) or dynamic thermomechanical analysis. An oscillating force is applied to a sample of material and the resulting displacement of the sample is measured. From this the stiffness of the sample can be determined, and the sample modulus can be calculated. A plot of loss modulus as a function of temperature shows a maximum at Tg as shown in Figure 1.35. Figure 1.35 shows a series of blends of high-impact styrene (HIPS) and PPO. As the amount of PPO is increased, Tg increases. The single Tg indicates that these blends are miscible. 

The Dynamic Mechanical Thermal Analysis (DMTA) technique when used to explore the thermal stability properties of the TPUs gives the results shown in Figs 9.4-9.12 (taken from Hepburn, 1987). 

Dynamical mechanical thermal analysis (DMTA) results also indicate that the effective rubber volume fraction is greater in the blends containing maleic anhydride grafted rubber. 

Thiraphattaraphun and coworkers also reported the thermal transition phenomena of the natural rubber-gru/i -methyl methacrylic acid obtained by the dynamic mechanical thermal analysis method. In the transition region, increasing the temperature resulted in a decrease in the storage modulus due to the increase in the chain stiffness of the polymer. Increasing the amount of... 

The viscoelastic properties of the blends were analysed using dynamic mechanical thermal analysis. The plot of tan 5 versus temperature showed a single relaxation peak around 130 °C, corresponding to the Tg of the epoxy-rich phase for the unmodified epoxy network and for the blends. On further examination, a relaxation peak of very low amplitude at around —65 °C (called p-relaxation), for both modified and neat epoxy matrices, is found, which is attributed to the motions of glycidyl units in the network. The Tg of the rubbery phase seems to be overlapped with p-relaxation and the Tg of the epoxy-rich phase slightly shifts toward the low-temperature side with the addition of the rubber. The decrease in Tg of the epoxy phase can be attributed to a dilution effect by the addition of the rubber phase, and may also result... 

Natural rubber based-blends and IPNs have been developed to improve the physical and chemical properties of conventional natural rubber for applications in many industrial products. They can provide different materials that express various improved properties by blending with several types of polymer such as thermoplastics, thermosets, synthetic rubbers, and biopolymers, and may also adding some compatibilizers. However, the level of these blends also directly affects their mechanical and viscoelastic properties. The mechanical properties of these polymer blended materials can be determined by several mechanical instruments such as tensile machine and Shore durometer. In addition, the viscoelastic properties can mostly be determined by some thermal analyser such as dynamic mechanical thermal analysis and dynamic mechanical analysis to provide the glass transition temperature values of polymer blends. For most of these natural rubber blends and IPNs, increasing the level of polymer and compatibilizer blends resulted in an increase of the mechanical properties until reached an optimum level, and then their values decreased. On the other hand, the viscoelastic behaviours mainly depended on the intermolecular forces of each material blend that can be used to investigate the miscibility of them. Therefore, the natural rubber blends and IPNs with different components should be specifically investigated in their mechanical and viscoelastic properties to obtain the optimum blended materials for use in several applications. 

Dynamic mechanical thermal analysis (DMTA) or Dynamic mechanical analysis (DMA) measures the response of a given material to an oscillatory deformation as a function of temperature. DMA results are composed of three parameters (a) the storage modulus (E ), corresponding to the elastic response to the deformation, (b) the loss modulus (E")> the plastic response to the deformation and (c) tan 8 the ratio (E"/E ), a measure of the damping behaviour which is useful for determining the occurrence of molecular mobility transitions, such as the glass transition temperature (Tg). DMA can provide reliable information over the relaxation behaviour of the materials. 

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