Dynamic Mechanical Characterization

The Tg determination, while not a thermodynamic criteria for misdbility, is an easy and effective method for determination of the phase behavior. The author, having conducted literally thousands of these measurements (primarily by dynamical mechanical methods), has found this to be a viable screening method that is highly reliable. In the borderline cases (xu 0), the experimental protocol is critical and with proper consideration of the experimental details, exceptions to these observations are rare. In the cases of specific interactions xn 0), the literature is even clearer as glass transition measurements agree well with the results of other characterization methods, including those which meet the criteria of thermodynamic misdbility. 

One of the most common methods utilized to characterize the phase behavior of polymer blends employs low amplitude cyclic deformation studies to obtain the elastic and viscoelastic properties. This method, termed dynamic mechanical characterization, yields high resolution of polymer transitions including secondary relaxation processes, crystalline melting transitions and of primary importance, the glass transition. This method maps the data over a broad temperature range to ascertain the phase behavior. 

E and G are the in-phase components and E and G are the out-of-phase components of their respective complex moduli. A parameter termed the damping coefficient or loss factor is defined as 

Plots of tan S, E or G versus temperature yield peak values that correspond to various transitions including the glass transition. 

Free vibration and forced vibration methods have been employed to determine the respective data. Free vibration was common earlier in polymer blend studies, but forced vibration data is much more common today due to the availability of more sophisticated testing equipment. Free vibration methods include the torsion pendulum, the vibrating reed and the torsional braid analyzer. The torsion pendulum is comprised of an inertial source (disk or rod), which can freely vibrate and is attached to a specimen, which is rigidly fixed at one end. Upon angular deformation of the inertial source and releasing, a damped sinusoidal curve depicts the resultant deformation of the sample [18,19]. Tan S can be calculated from 

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Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

Dynamic mechanical characterization of rubber-modified polystyrenes or styrene copolymers can reveal some of the variables in the structure of the rubber phase. The tan<5 peak at lower temperature, which can be considered as representative of the rubber a relaxation, was shown to be affected by the volume fraction of the rubbery phase, , in both HIPS [54] and ABS [55]. 

A torsion pendulum interfaced with a desktop computer form an automated instrument for dynamic mechanical characterization of polymeric materials. The computer controls the initiation of the oscillations, collects the digitized data and calculates the shear modulus and loss modulus from the damped oscillations, utilizing one of four methods of analysis ... 

Characterization. Opacity of a sample was determined from its absorption at 700 nm. Dynamic mechanical characterization was carried out with an automated Rheovibron DDV-IIC (IMASS) in the tensile mode with a heating rate cf 1.5°/min data taken at 11 Hz are reported here. The same sample was used for the entire temperature range of -100° to 150°C. Because of the magnitude of the load cell compliance, properties of our samples in the glassy region below about -40°C were not viewed in any quantitative sense. 

A. Shabeer, A. Garg, S. Sundararaman, K. Chandrashekhara, V. Flanigan and S. Kapila, Dynamic mechanical characterization of a soy-based epoxy resin system , J Appl Polym Sci, 2005,98,1772-80. 

Jenkins SD, Emmerson GT, McGrail PT, Robinson RM, J Adhesion, 45(1-4), 15-27, 1994. Labronici M, Ishida H, Dynamic mechanical characterization of PMR polyimide/carbon fiber composites modified by fiber coating with silicones. Composite Interfaces, 5(3), 257-275,1998. Labronici M, Ishida H, Effect of the silicone interlayer on mechanical properties of carbon fiber reinforced PMR-15 polyimide composites. Composite Interfaces, 5(2), 87-116, 1998. 

Barick, A.K., Tripathy, D.K. Thramal and dynamic mechanical characterization of thermoplastic polyurethane/organoclay nanocomposites inepared by melt compounding. Mater. Sci. Eng. A 527, 812-823 (2010)... 

Holmes, G. A. Letton, A., Bisphenol-A Bimodal Epoxy Resins. Part I The Dynamic Mechanical Characterization of a 6300 (340/22,500) Weight Average Molecular Weight System. Polym. Eng. Sci. 1994, 34,1635-1642. 

Nazhat, S.N., Kellomaki, M., Tormala, P., Tanner, K.E., Bonfield, W., 2001. Dynamic mechanical characterization of biodegradable composites of hydroxyapatite and polylactides. s.L Journal of Biomedical Materials Research 58 (4), 335—343. 

Nazhat SN, Joseph R, Wang M et al (2000) Dynamic mechanical characterization of hydroxyapatite reinforced polyethylene effect of particle size. J Mater Sci Mater Med 11 621-628... 

Rich J, Tuominen J, Kylmii J, Seppala J, Nazhat SN, Tanner KE. Lactic acid based PEU/HA and PEU/BCP composites dynamic mechanical characterization of hydrolysis. / Biomed Mater Res (Appl Biomater) 2002 63 346-353. 

Elias, M. B., R. Machado and S. V. Canevarolo. (2000). Thermal and dynamic-mechanical characterization of uni-and biaxially oriented polypropylene films. Journal of Thermal Analysis and Calorimetry, 59 143-155. 

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