Relaxation behavior, mechanical

Aside from ion content, a wide range of properties is available in ionomers by control of various processing variables, such as degree of conversion (neutralization), type of counterion, plasticizer content and thermal treatment. Various examples illustrating possible effects of these variables on mechanical relaxation behavior and on such mechanical properties as stiffness, strength, and time- or energy-to-fracture have been given. 

Sadanobu, J. and Tsukioka, M., Mechanical relaxation behaviors for homolog poly(alkylenenaphthalate)s, in Proceedings of the 55th SPE ANTEC 97 Conference, May 5-8, 1997, Toronto, ON, Canada, Society of Plastics Engineers, Brookfield, CT, 1997, Vol. 2, pp. 1567-1571. 

As a general comment about the dynamic mechanical relaxational behavior of this polymer, the results are consistent with dielectric data [210] and with the fact that no glass transition phenomenon is observed, at least in the range of temperature studied. This is striking in an amorphous polymer. It is likely that the residual part of the molecule mechanically active above the temperature of the ft relaxation is only a small one, and this is the reason for the low loss observed in the a zone. 

Baer, E., Kohn, R., Papir, Y., Mechanical Relaxation Behavior of Collagen,... 

Mechanical relaxation behavior of poly(n-butyl acrylate) was studied using a freely oscillating torsional pendulum at frequencies of about 1 cycle/sec in the temperature range of 100 to 300 K. Two damping measurements were made every 5°. 

Our approach has been to synthesize the dleplsulflde resin corresponding to the normal blsphenol A type dlepoxlde resins. A polyamide type curing agent (Versamlde 140) was used because of our particular Interest In orthopedic adhesives, l.e. "bone cement". Some of the properties were therefore tailored to be optimum near body temperature. We have found very little prior literature on dleplsulflde resins. As prepared, the dleplsulflde resin analog of DGEBA Is a crystalline solid which must be heated above Its melting temperature for reaction. Charlesworth (2) has reported mechanical relaxation behavior of epoxy-episulfide poly-... 

M.E. De Rosa, W.W. Adams, T.J. Bumring, H. Shi, S.H. Chen, Dynamic mechanical relaxation behavior of low molecular weight side chain cyclic liquid crystalline compormds near the glass transition temperatare. Macromolecules 29, 5650-5657 (1996)... 

Attempts to improve the mechanical properties have focused on biocompatible plasticizers. Blending with PEG, the conventional name for low molecular weight (<20 000) PEG, improves elongation at break and softness of PLA. At ambient temperature, the desired mechanical properties are achieved by blending PLA with 30 wt% PEG Table 4.2 shows the effect of PEG content on the thermal and mechanical properties of quenched PLA/PEG blends. However, there is evidence that the blend is not stable and the attractive mechanical properties are lost over time. The dynamic mechanical relaxation behavior and tensile stress-strain behavior of PLA and PLA/PEG blends are shown in Figs. 4.19 and Fig. 4.20 respectively. 

MECHANICAL RELAXATION BEHAVIOR OF HYDROGENATED METALLIC GLASSES... 

Dynamic mechanical analysis (DMA) was performed to determine the influence of the polymer constitution on tensile modulus and mechanical relaxation behavior. For this purpose, a Perkin Elmer DMA-7 was run in tensile mode at an oscillation frequency of 1 Hz with a static stress level of 5 x lO Pa and a superposed oscillatory stress of 4 x 10 Pa. With this stress controlled instrument, the strain and phase difference between stress and strain are the measured outputs. Typically, the resulting strain levels ranged from 0.05% to 0.2% when the sample dimensions were 8 mm x 2 mm x 0.1 mm. A gaseous helium purge and a heating rate of 3°C min" were employed. The temperature scale was calibrated with indium, and the force and compliance calibrations were performed according to conventional methods. 

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