Dynamic mechanical studies

Studies of the particle—epoxy interface and particle composition have been helphil in understanding the mbber-particle formation in epoxy resins (306). Based on extensive dynamic mechanical studies of epoxy resin cure, a mechanism was proposed for the development of a heterophase morphology in mbber-modifted epoxy resins (307). Other functionalized mbbers, such as amine-terminated butadiene—acrylonitrile copolymers (308) and -butyl acrylate—acryhc acid copolymers (309), have been used for toughening epoxy resins. 

Both tear resistance and hysteresis increase on incorporation of silica, but the effect is less pronounced as compared to the stress-strain properties. Tension set of the ZnO-neutralized m-EPDM system is low (around 20%) and incorporation of filler causes only a marginal increase in set due to chain slippage over the filler surface, as previously discussed. Measurement of physical properties reveal that there occurs an interaction between the filler surface and the polymer. Results of dynamic mechanical studies, subsequently discussed, support the conclusions derived from other physical properties. 

Multiblock polyethylene-polydimethylsiloxane copolymers were obtained by the reaction of silane terminated PDMS and hydroxyl terminated polyethylene oligomers in the presence of stannous octoate as the catalyst 254). The reactions were conducted in refluxing xylene for 24 hours. PDMS block size was kept constant at 3,200 g/mole, whereas polyethylene segment molecular weights were varied between 1,200 and 6,500 g/mole. Thermal analysis and dynamic mechanical studies of the copolymers showed the formation of two-phase structures with crystalline polyethylene segments. 

All the samples prepared were transparent and flexible. Dynamic mechanical studies indicated that a portion of the siloxane species was phase separated, while the remainder was well dispersed. The effects of reaction conditions on the dispersion of... 

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

According to a dynamic mechanical study by Saba, Sauer, and Woodward (1963) for PPO and a dilatometric study by Daane and Barker (1964) for cellulose acetate, the high-temperature relaxations of PPO, CDA, and CTA are primary relaxations which arise from segmental motion in the amorphous phase and the low-temperature relaxations are presumably ascribed to a more local motion in the amorphous phase. 

Ebdon JR, Hourston DJ, Klein PG (1986) Polyurethane-polysiloxane interpenetrating polymer networks 2. Morphological and dynamic mechanical studies. Polymer 27( 11) 1807—1814... 

A Dynamic Mechanical Study of Phase Segregation in Toluene Diisocyanate, Block Polyurethanes... 

The systematic dynamic mechanical study reported here was undertaken to gain additional insight into the molecular relaxation processes which occur in TDI polyurethanes as well as to test the generality of findings developed from investigations of other chemical classes of segmented polyurethanes. 

Finally, the NMR and the dynamic mechanical study show that two regions are present in filled silicone rubbers above the Tg, which differ significantly in local chain mobility immobilized chain units adsorbed at the filler surface and mobile chain units outside the adsorption layer. The local chain motions outside the adsorption layer are similar to those for unfilled rubbers. Chain motions in the adsorption layer however are strongly restricted. The frequency of chain motions in the adsorption layer at 300 K is comparable to the fi-equency of chain motions in a crosslinked PDMS containing 3-4 elementary chain units between network junctions [26]. 

Secondary Transitions. In addition to the anomalous glass transition in the 40°-50°C region because of the motion of large segments of the polymer chain, stratum corneum like many other polymers displays smaller secondary transitions at lower temperatures. These arise generally from the motion of side chains or the small segments of the backbone. The tan 8 behavior from dynamic mechanical studies of dry... 

Corneum of Human and Neonatal Rat II. Dynamic Mechanical Studies, Biochim. Biophys. Acta (1973) 304, 267. 

We have used X-ray methods to compare the crystallite size of RIM specimens prepared with and without use of a polyether diamine (PEDA) additive. These results are compared with differential scanning calorimetry data on the hard domain melting behavior and dynamic-mechanical studies of the extent of phase separation. Mechanical data on flexural modulus, elongation, impact strength, and heat sag behavior have been obtained for the same specimens and have been correlated with the structural analyses. 

Partially Neutralized Nafion-Cs. Dynamic mechanical studies of partially neutralized Nafion-Cs from the Nafion acid was performed by Kyu et al (58). The starting material used in their study was Nafion acid of equivalent weight 1155. The acid samples were first boiled in distilled water to ensure extensive swelling, and then Immersed in... 

The slope of the transition region was found to broaden with a decrease in (Figure 8). These results indicate that an increase in crosslink density results in the broadening of the slope, as is often observed. For example, from dynamic mechanical studies of polyesters, Shibayama and Suzuki (36) had also shown that the dispersion broadens with an increase in crosslink density. 

Interpretation of mechanical measurements in terms of molecular structure was until fairly recently confined essentially to identification of the temperatures of the major viscoelastic relaxations through extensional or torsional dynamic mechanical studies. Now, however, investigations of the elastic constants and their temperature dependence—allied with dynamic mechanical, creep and both wide and small angle X-ray diffraction— are yielding fairly detailed pictures of the interrelation of the crystalline and less well ordered regions of some oriented solid polymers. 

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