Dynamic Mechanical Analysis, rubber

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

Abbreviations y x AFM AIBN BuMA Ca DCP DMA DMS DSC EGDMA EMA EPDM FT-IR HDPE HTV IPN LDPE LLDPE MA MAA MDI MMA PA PAC PB PBT PBuMA PDMS PDMS-NH2 interfacial tension viscosity ratio atomic force microscopy 2,2 -azobis(isobutyronitrile) butyl methacrylate capillary number dicumyl peroxide dynamic mechanical analysis dynamic mechanical spectroscopy differential scanning calorimetry ethylene glycol dimethacrylate ethyl methacrylate ethylene-propylene-diene rubber Fourier transform-infra-red high density polyethylene high temperature vulcanization interpenetrating polymer network low density polyethylene linear low density polyethylene maleic anhydride methacrylic acid 4,4 -diphenylmethanediisocyanate methyl methacrylate poly( amide) poly( acrylate) poly(butadiene) poly(butylene terephtalate) poly(butyl methacrylate) poly(dimethylsiloxane) amino-terminated poly(dimethylsiloxane)... 

The mechanical behavior of the hydrogels can be described by the theories of rubber elasticity and viscoelasticity, which are based on time-independent and time-dependent recovery of the chain orientation and structure, respectively. Mechanical properties due to rubber elastic behavior of hydrogels can be determined by tensile measurements, while the viscoelastic behavior can be determined through dynamic mechanical analysis. 

Dynamic mechanical analysis of filled systems confirms analytical observations. The thickness of the restricted mobility region in carbon filled rubber is proportional to the activity of the carbon black. 

Figure 4. Variation of Tg with rubber content, as determined from dynamic mechanical analysis. The temperature at which tan 8 reached a maximum value was taken as Tg. The experiment was conducted in the tensile mode at a heating rate of 2 °C/min at 5 Hz.

Analytical Techniques. The cloud point of the blends was determined with a light-transmission device (21). Once the blend was cloudy, the test tube was taken out and chilled in ice, so that the time and conversion at the cloud point, tc and a could be obtained. The Tg value and conversion were measured by DSC (Mettfer TA3000 microcalorimeter) (22). The gel time, fge], of rubber-cyanate blends was determined as the time at which insolubles appeared in tetrahydrofu-ran (THF). That of PES-cyanate was determined by dynamic mechanical analysis (Rheometrics RDA700). 

Amorphous phase transition effects Dynamic mechanical analysis (DMA) on both a cold (20°C) compressed powder sample and a compression moulded (240°C) sheet sample was used to investigate the relaxation processes i.e. especially the glass-rubber transition, of the amorphous phase of PK terpolymer. 

Other systems investigated by this group are butyl rubber, - natural rubber sensitized with acrylates,chloroprene, chlorobutyl rubber and nitrile rubber.More recently, Perera has examined the relationship between chemical changes in radiation-grafted natural rubber, determined using MAS NMR, and mechanical properties measured using dynamic mechanical analysis. 

Probably the most convenient and most widely used methods arc specific heat using DSC (see Section 2 in this chapter and Section 5 in Chapter 24) and dynamic mechanical analysis (see Chapter 21). However, a range of methods have been tried and reported on in the literature, from volume change to refractive index. For rubbers a measure can be obtained from the low temperature tests discussed in Section 5, Practically, the glass... 

The dynamic mechanical analysis shows that both pressure-sensitive materials are heterogeneous blends, i.e., they consist of a gum-r ich phase which coexists with a resin-rich phase of resin and gum. In this respect, they are similar to other pressure-sensitive adhesives containing other resins and rubbers. 

The effect of EOMt, as already mentioned above, on the properties of different rubbers/Mt composites were studied and reported by Das et A good correlation, which is shown in Figure 8.13, was observed between the area of the (001) basal reflections and the area of the tan 5-temperature curve from dynamic mechanical analysis (DMA) study. A small basal reflection was related... 

Butadiene Rubber Calcium Carbonate Conventional Vulcanizing systems Dynamic Mechanical Analysis Elongation at Break Ground CaCOa... 

Crosslinked NR nanocomposites were prepared with montmorillonite. Morphology was characterized using transmission electron microscopy (TEM), wide-angle X-ray scattering (WAXS), and dynamic mechanical analysis (DMA). X-ray scattering patterns revealed clay intercalation and TEM showed dispersion with partial delamination. The loss modulus peak broadened with clay content, while Tg remain constant. Montmorillonite reinforced the rubber. The DMA exhibited non-linear behaviour typified as a Payne effect (see Section 20.11) that increased with clay content and was more pronounced for this type of nanocomposite. Viscoelastic behaviour was observed under large strains via recovery and stress relaxation. ... 

M. Jacob, B. Francis, S. Thomas, and K.T. Varughese, Dynamical mechanical analysis of sisal/oil palm hybrid fiber-reinforced natural rubber composites. Polym. Compos. 21,671-680 (2006). 

The EB treatment of the GTR containing LDPE and EVA matrix blends showed significant benefits. The 200 kGy EB absorbed dose (in air) resulted in a better tensile strength and increased elongation at break, without changing the tensile modulus, which provides more rubber-Uke properties [142]. The modest change in hardness proves the cross-linking effect caused by the EB treatment in all cases. The dynamic mechanical analysis confirmed the compatibilization effect of EVA and... 

AFM, atomic force microscopy DMA, dynamic mechanical analysis DSC, differential scanning calorimetry flVR, oxidized natural rubber FTIR, Fourier transform infrared spectroscopy NR, natural rubber PLA, poly(lactic acid) QP, quaternary phosphonium salt TGA, thermogravimetric anal is TPU, thermoplastic polyurethane XPCL, end-carboxylated teledielic... 

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