Dynamic mechanical analysis curves

Dynamic mechanical analysis curve Graphical representation of the data collected by a dynamic mechanical analyser, where the dynamic loss modulus, dynamic storage modulus and tan 5 are plotted as a function of temperature (scanning mode) or time (isothermal mode). 

The effect of larger increases in modulus for low modulus materials can be seen in dynamic mechanical analysis curves. The typical modulus increase seen in these curves below the Jg, on a percentage of starting modulus, is substantially lower than that seen above the Tg. This observation makes the large increases in HTD observed in nylon quite easy to rationalize. 

Figure 8.1 Dynamic mechanical analysis curve for PEI, PEIS, and PEEK modulus versus temperature.

Fig. 6.25. Dynamic mechanical analysis curves of PpPTA (Twaron HM) and PBO fibers, obtained in nitrogen atmosphere, frequency 72 Hz filled symbols are for PpPTA and open symbols for PBO.

In a similar fashion. Thermally Stimulated Current spectrometry (TSC) makes use of an appHed d-c potential that acts as the stress to orient dipoles. The temperature is then lowered to trap these dipoles, and small electrical currents are measured during heating as the dipoles relax. The resulting relaxation maps have been related to G and G" curves obtained by dynamic mechanical analysis (244—246). This technique, long carried out only in laboratory-built instmments, is available as a commercial TSC spectrometer from Thermold Partners L.P., formerly Solomat Instmments (247). 

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. 

In an NMR analysis of the effects of /-irradiation induced degradation on a specific polyurethane (PU) elastomer system, Maxwell and co-workers [87] used a combination of both H and 13C NMR techniques, and correlated these with mechanical properties derived from dynamic mechanical analysis (DMA). 1H NMR was used to determine spin-echo decay curves for three samples, which consisted of a control and two samples exposed to different levels of /-irradiation in air. These results were deconvoluted into three T2 components that represented T2 values which could be attributed to an interfacial domain between hard and soft segments of the PU, the PU soft segment, and the sol... 

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

Pellicle and tea-immersed pellicle were analyzed using nanoDMA (dynamic mechanical analysis) to see if the tannins had an effect on the viscoelasticity of the pellicle. NanoDMA is a technique used to study and characterize mechanical properties in viscoelastic materials. The method is an extension of nanoindentation testing [58, 59], An analysis of the nanoindentation load-depth curve gives the hardness (H) and reduced elastic modulus (E ), provided the area of contact, A, between the indenter tip and the sample is known [ 13]. By... 

Thermal mechanical analysis (Dupont 990/942 IMA), and dynamic mechanical analysis (Dupont 1090/982 DMA) curves for a designed set of model formulations were evaluated for CTE and tensile storage modulus as a function of filler level and elastomer additive type and level. Fifteen formulations were prepared with 68-75% filler, 0-4% silicone elastomer A, 0-4% non-silicone elastomer B and the balance 17-32%. Both elastomers have Tg s below room temperature. An extreme vertices formulation design was generated by computer (Table I). 

Figure 9. Results of dynamic mechanical analysis, showing loss factor as a function of temperature for unmodified epoxy (dashed curve), epoxy containing 28 wt% ETBN (dotted curve), epoxy containing 28 wt% PPU (dotted-dashed curve), and epoxy containing a blend of 14 wt% ETBN and 14 wt% PPU (solid curve). Epoxy formulation 100 parts ofbisphenol A diglycidyl ether (5.4 mol epoxy/kg), 5 parts of butane-1,4-dioldiglycidyl ether, 5 parts of dicyandiamide, 0.5 part of chlorotolurone accelerator, and 1 part of pyrogenic silica (Aeorosil 380). Cure 1 h at 140 °C, 1 h at 160 °C.

Figure 22 Dynamic mechanical analysis of acrylic fibres in air, water and solutions of benzyl alcohol. Measurements performed in tension at a frequency of I Hz, heating rate 1°C min. Curves shown offset for clarity...

Dynamic Mechanical Analysis and Stress Relaxation Behavior. Samples were compression molded into bars of the dimensions 38.xl2.5x0.78 0.007 mm and 65.x9.7xl.7 0.007 mm in a Carver laboratory hot press model C. A TA Instruments 983 DMA, which was operated in the fixed frequency mode, was used to characterize the storage and loss moduli as a function of temperature. Samples were scanned at fi-equencies from 0.05 to 10.0 Hz over a temperature range from -150 C to above the glass transition temperature. The displacement was 0.4 - 0.6 mm. Stress relaxation curves were determined for the same size samples at a constant strain. The sample was displaced for 10.0 minutes and then allowed to recover for 10.0 minutes. The stress data were taken in five degree increments. A microprocessor controlled Liquid Nitrogen Cooling Accessory (LNCA) was used for sub-ambient operations. 

The term thermal analysis (TA) is frequently used to describe analytical experimental techniques which investigate the behaviour of a sample as a function of temperature. This definition is too broad to be of practical use. In this book, TA refers to conventional TA techniques such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermogravimetry (TG), thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA). A selection of representative TA curves is presented in Figure 1.1. 

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... 

Tangent modulus n. The slope of the curve at any point on a static stress-strain graph (dcr/ds) expressed in pascals per imit of strain. This slope is the tangent modulus in whatever mode of stress the curve has arisen from — tension compression, or shear. [Since strain is dimensionless, the unit given for modulus is normally just stress (Pa)]. Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York. 

HDT 0.45 MPa and 1.8 MPa (66 and 264) and Vicat softening temperatme Modulus versus temperature curve obtained from dynamic mechanical analysis (DMA)... 

Sichina [71] has discussed the applications of the dynamic mechanical analysis (DMA) to the prediction of polymer lifetimes and long-term performances, e.g., creep in gaskets, stress relaxation in snap-fit parts, modulus decay in composite structural beams, creep in bolted plates and heat deformation frequencies in structural parts. The ability of this system to generate master curves makes the prediction of product... 

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