Crystalline Dynamic mechanical properties

The dynamic mechanical properties of PTFE have been measured at frequencies from 0.033 to 90 Uz. Abmpt changes in the distribution of relaxation times are associated with the crystalline transitions at 19 and 30°C (75). The activation energies are 102.5 kj/mol (24.5 kcal/mol) below 19°C, 510.4 kJ/mol (122 kcal/mol) between the transitions, and 31.4 kJ/mol (7.5 kcal/mol) above 30°C. 

The dynamic mechanical properties of VDC—VC copolymers have been studied in detail. The incorporation of VC units in the polymer results in a drop in dynamic modulus because of the reduction in crystallinity. However, the glass-transition temperature is raised therefore, the softening effect observed at room temperature is accompanied by increased brittleness at lower temperatures. These copolymers are normally plasticized in order to avoid this. Small amounts of plasticizer (2—10 wt %) depress T significantly without loss of strength at room temperature. At higher levels of VC, the T of the copolymer is above room temperature and the modulus rises again. A minimum in modulus or maximum in softness is usually observed in copolymers in which T is above room temperature. A thermomechanical analysis of VDC—AN (acrylonitrile) and VDC—MMA (methyl methacrylate) copolymer systems shows a minimum in softening point at 79.4 and 68.1 mol % VDC, respectively (86). 

The stereoregularity—i.e., distribution of the stereosequence length in these polymers—has a marked effect on the crystallization rates and the morphology of the crystalline aggregates. These differences, in turn, influence the dynamic mechanical properties and the temperature dependence of the dynamic mechanical properties. In order to interpret any differences in the dynamic mechanical properties of polymers and copolymers of propylene oxide made with different catalysts, it was interesting to study the differences in the stereosequence length in the propylene oxide polymers made with a few representative catalysts. 

The effect of additives, others than plasticizers, on the dynamic mechanical properties of styrene polymers have attracted little attention from researchers. Flame retardants such as l,2-bis(tetrabromophthalimide)ethane, crystalline decabromodiphenyl oxide (DBDPO) and antimony trioxide (Sb203) do not affect the a relaxation of aPS [38,39]. 

It is well known that the third components, although small in quantity, might also bring about other significant changes such as changes in crystalline behavior, morphology, and dynamic mechanical properties, which influence the blend properties for end use. Table III lists the data obtained by DSC for iPS-fc-iPP-iPS-iPP ternary blends. The results indicate that PP crystallization... 

We have reported previously the sulfonation of a polypentenamer (PP) under reaction conditions that preclude the formation of covalent cross-links (J). The sulfonated materials are isolated in the form of sodium salts to give ion-containing elastomers. The thermal and dynamic mechanical properties of the sulfonated PP s indicate the existence of phase-separated ionic clusters above a sulfonate concentration of roughly 10 mol % (2). It has been shown (J) that the unsaturation in the sulfonated PP s can be removed by a diimide hydrogenation reaction to yield a material that is essentially linear polyethylene with pendant sulfonate groups. In this manner the effect of backbone crystallinity on... 

Although the dynamic mechanical properties and the stress-strain behavior iV of block copolymers have been studied extensively, very little creep data are available on these materials (1-17). A number of block copolymers are now commercially available as thermoplastic elastomers to replace crosslinked rubber formulations and other plastics (16). For applications in which the finished object must bear loads for extended periods of time, it is important to know how these new materials compare with conventional crosslinked rubbers and more rigid plastics in dimensional stability or creep behavior. The creep of five commercial block polymers was measured as a function of temperature and molding conditions. Four of the polymers had crystalline hard blocks, and one had a glassy polystyrene hard block. The soft blocks were various kinds of elastomeric materials. The creep of the block polymers was also compared with that of a normal, crosslinked natural rubber and crystalline poly(tetra-methylene terephthalate) (PTMT). 

The miscibility of olefin copolymers such as ethylene-a-olefin copolymers was found to be controlled by the structural composition and the primary strucmre of the copolymers. Using these copolymers, binary blends with various compatibilities were prepared and the effects of compatibihty on mechanical properties in the binary blends were investigated. The tensile properties in binary blends of iPP with rubbery olefin copolymers are considerably influenced by the miscibility between iPP and the copolymers. The miscibility of iPP with other polyolefins is described in detail based on the dynamic mechanical properties, morphology observation, and solidification process. It is found that EBR, EHR, and EOR having more than 50 mol% of a-olefin are miscible with iPP in the molten state. In the solid state, the miscible copolymers are dissolved in the amorphous region of iPP, although the copolymers are excluded from crystalhne lattice of iPP. The isotactic propylene sequence in the EP copolymers with a propylene-unit content of more than 84 mol% participates in the crystallization process of iPP, resulting that a part of the EP copolymers is included in the crystalline lattice of iPP. 

X.-B. Yu, C. Wei, and F.-A. Zhang. Studies on the mechanical and dynamic mechanical properties of thermotropic liquid crystalline polymer/unsaturated polyester/glass fiber in situ hybrid composites. Polym. Adv. Tech., 17 534-539, 2006. 

S. Saikrasun and T. Amomsakchai. Isothermal decomposition behavior and dynamic mechanical properties of in situ-reinforcing elastomer composites based on thermoplastic elastomers and thermotropic liquid crystalline polymer. / Appl. Polym. ScL, 103 917-927, 2007. 

ATR-FTIR, solid state C-NMR and XRD results showed the composition of the fibre surface and the relationship of its characteristic with thermal resistance. The crystalline content of the natural fibre remarkably increased after chemical treatment, which was confirmed by XRD and solid-state C-NMR. HCIO4 is the most efficient chemical in terms of wax and fatty acid residue removal in our work. Hence, the dynamic mechanical properties of the natural fibre after HCIO4 treatment were improved. It was reported that the acidolysis lignins were isolated from sugar cane bagasse and curaua fibres by adding a mixture of dioxane and 0.1 N aqueous HCl (8.5 1.5, v/v) at 100 °C for 2 h under N2. ATR-FTIR and TGA of the oxidized lignins revealed a decrease in... 

Solid-state polymerization of crystalline monomer without any intermediate loss of order. The topotactic oligomers have been produced, but the order is lost as the polymerization progresses beyond a low degree of polymerization. Test equipment used for determining the dynamic mechanical properties of plastics. 

The thermal transition behaviour of the blends was consistent with the above observations. For the compatible blends (with SAN-8 to SAN-24) the dynamic mechanical properties showed, at high SAN contents where there is no PCL crystallinity, a single shifted Tg consistent with plasticization of SAN by admixing with PCL. Pure SAN copolymers had TgS from 116 °C (SAN-8) to 124 °C (SAN-28). At higher PCL contents, where there is PCL crystallinity, the shifted Tg overlapped with PCL melting to give a complex relaxation peak the P-relaxation of PCL was seen at -120 °C [20]. 

In a very extensive study of both stress relaxation and dynamic mechanical properties in simple extension, on single crystal mats of fractions of linear polyethylene, Takayanagi and collaborators were able to combine data at different temperatures by reduced variables over most of the range from 16°C up to the temperature of crystallization and also to show that the dynamic and transient data corresponded fairly closely, provided the latter were corrected for nonlinear behavior by an extrapolation procedure to zero strain. It is characteristic of crystalline polymers that departures from linear viscoelastic behavior appear at very small strains, and are sometimes significant in stress relaxation even at a tensile strain of = 0.001. In dynamic measurements, the strains are usually small enough to fall within the linear range. 

Davies, G.R. and Ward, I.M. (1988) Structure and properties of oriented thermotropic liquid crystal polymers in the solid state, in High Modulus Polymers (eds A.E. Zachariades and R.S. Porter), Marcel Dekker, New York, Chap. 2 Troughton, M.J., Davies, G.R. and Ward, I.M. (1989) Dynamic mechanical properties of random copolyesters of 4-hydroxybenzoic acid and 2-hydroxy 6-naphthoic acid. Polymer, 30, 58 Green, D.I., Unwin, A.P., Davies, G.R. and Ward, I.M. (1990) An aggregate model for random liquid crystalline copolyesters. Polymer, 31, 579. 

The static- and dynamic-mechanical properties and parameters grouped in Table 1 refer to crystalline PO below the melting temperature, but some of them characterize the corresponding PO in the molten (viscoelastic) state, too. 

Ferry J D (1970) Viscoelastic Properties of Polymers, 2nd ed., Wiley, New York. Galeski A (2002) Dynamic mechanical properties of crystalline polymer blends. The influence of interfaces and orientation, e-Polymers 026 1-29. 

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