Dynamic-mechanical spectroscopy

Rich and reliable viscoelastic data can be obtained from measuring the dynamic mechanical response of the polymeric liquid to a rate-of-strain X t) which is harmonically oscillatory  

The result expressed as a function of the oscillatory frequency w is often referred to as the viscoelastic spectrum. Because the polymeric liquid has both the viscous and elastic properties, the time dependence of the induced stress will not be totally either in phase or out of phase with the oscillatory rate-of-strain. Substituting Eq. (4.31) into Eq. (4.22), we obtain the stress 

As shown in Fig. 4.8, X t) (Eq. (4.31)) and a t) (Eq. (4.33)), both being sinusoidal, have a phase-angle difference. We can express these two quantities, respectively, as 

In terms of the complex viscosity 7, the phase difference between the stress and the rate-of-strain can be expressed. Generally the stress induced by the rate-of-strain given by Eq. (4.31) can be written as 

r] represents the viscous contribution to the stress, i.e. the component in phase ( = 0) with the rate-of-strain, and is related to the 

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The excellent low temperature properties of FZ have been iadicated ia Table 1. Modulus curves were obtained usiag dynamic mechanical spectroscopy to compare several elastomer types at a constant 75 durometer hardness. These curves iadicate the low temperature flexibiUty of FZ is similar to fluorosihcone and ia great contrast to that of a fluorocarbon elastomer (vinyUdene fluoride copolymer) (Fig. 3) (15). 

Since pc 1/2, we observe that Me 2Mg, as commonly observed. Mg is determined from the onset of the rubbery plateau by dynamic mechanical spectroscopy and Me is determined at the onset of the highly entangled zero-shear viscosity law, T) M. This provides a new interpretation of the critical entanglement molecular weight Mg, as the molecular weight at which entanglement percolation occurs while the dynamics changes from Rouse to reptation. It also represents the... 

From the dynamic mechanical spectroscopy, an increase of PTMO molecular weight from 650 to 2000 results in a decrease in both the modulus and the glass transition temperature of the final product. The SAXS results indicate that a correlation distance exists in the samples, and this distance increases as PTMO molecular weight increases. A cluster model is thus suggested to account for the experimental results. 

Roudaut et al. (1999a) used low-frequency pulsed-proton NMR and dielectric dynamic mechanical spectroscopies to study molecular mobility in glassy bread (<9%) as a function of temperature. Based on NMR results, they reported that some (if not all) of the water molecules were much more mobile than the polymer matrix whose relaxation time could not be measured within the 20-p,s dead time of the RF probe. 

Molecular mixing via dynamic mechanical spectroscopy. While electron microscopy yields the phase size, shape, etc., as delineated above, dynamic mechanical spectroscopy (DMS) yields the composition within each phase. The DMS measurements employed a Rheovibron direct reading viscoelastometer model DDV-II (manufactured by Toyo Measuring Instruments Co., Ltd., Tokyo, Japan). The measurements were taken over a temperature range from -120°C to 140°C using a frequency of 110 Hz and a heating rate of about 1°C/ min. Sample dimensions were about 0.03 x 0.15 x 2 cms. 

Dynamical mechanical spectroscopy and Izod impact results suggest that the glass transition temperature of the elastomer phase constitutes the most critical parameter in achieving impact resistance in these materials. 

R Musto, M. Abbate, G. Ragosta and G. Scarinzi, A smdy by Raman, near-infrared and dynamic-mechanical spectroscopies on the curing behaviour, molecular structure and viscoelastic properties of epoxy/anhydride networks, Polymer, 48, 3703-3716 (2007). 

While several experimental techniques provide Information relating to dual phase continuity, the two most important methods Involve scanning electron microscopy and dynamic mechanical spectroscopy [16,22-2A]. Donatelll, et al [1 ] performed the first mechanical study on PB/PS IPN s. Figure 5 [ 6] illustrates the fit provided by the Davies equation [22] and the Budlansky equation [25,26], both of these equations derived on the assumption of dual phase continuity. 

The first data on polymer systems were collected via (laser-) light-scattering techniques [1] and turbidity measurements, further developed by Derham et al. [2,3]. Techniques based on the glass-transition of the polymer-blend constituents were also tested, such as DSC, Dynamic Mechanical Spectroscopy, and Dielectric relaxation [4]. Films made from solutions of... 

DSC measurements showed that the crystallization ability of this interphase region was reduced by the silane modification of the glass beads. Despite an increase in the amount of amorphous material with increasing number of silane layers, a decrease in the intensity of the fourth lifetime was observed. This decrease in the free volume is in accordance with the earlier observed reduced mobility in the interphase region measured by dynamic-mechanical spectroscopy in the melt state [9,10] and creep and stress relaxation measurements in the solid state [12]. 

The latexes were cleaned by ion exchange and serum replacement, and the number and type of surface groups were determined by conductometric titration. The molecular weight distributions of the polymers were determined by gel permeation chromatography. The stability of the latexes to added electrolyte was determined by spectrophotometry. The compositional distribution was determined by dynamic mechanical spectroscopy (Rheovibron) and differential scanning calorimetry, and the sequence distribution by C13 nuclear magnetic resonance. 

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)... 

Marie et al. [49] also studied the in-situ block copolymer formation via reactive blending of functionalized homopolymers. In their work, blends were characterized by SEM, DSC and dynamic mechanical spectroscopy (DMS). It should be noted that their blends (PA-6/PDMS and PS/PDMS) were composed totally using functionalized homopolymers. The different reactions under investigation were amine(NH2)/anhydride(An), amine(NH2)/epoxy(E) and carboxylic acid(COOH)/epoxy(E) (Fig. 5). 

Dynamic Mechanical Spectroscopy. Dynamic mechanical spectroscopy was used to study the loss and storage moduli and tan 8 of the several materials from —150° to +150°C. Thus we obtained information... 

Figure 8. Dynamic mechanical spectroscopy on samptes II, 12, and 15 showing the increase in glass transition temperature with increased epoxy prereaction time...

Damping and Dynamic Mechanical Spectroscopy. Dynamical mechanical spectroscopy means data taken with cyclical deformation of the sample. Often, the... 

Figure 1. Dynamic mechanical spectroscopy of formula B This material, containing 70% EA comonomer between polymer networks I and II, displays a mechanical spectrum only slightly broader than would be expected of the corresponding random copolymer.

Figure 2. Dynamic mechanical spectroscopy of formula U. With 60% EA the transition is noticeably broader than that shown in Figure 1.

Figure 3. Dynamic mechanical spectroscopy of formula JET. Notice the broad temperature span of high tan S values. With only 30% EA comonomer, the material shows a fat tan S curve.

The relaxation properties as probed by dynamic mechanical spectroscopy (DMS) for a series of ESI are shown in Figure 26.2. In accordance with the DSC results, the tan S loss maximum or Tg for the semicrystalline ESI appears to be fairly independent of styrene content. For the essentially amorphous ESI (>45wt% S), Tg increases with increasing styrene content. When compared with the amorphous ESI, the amplitude and width of the Tg loss peak are lower in amplitude and broader, respectively, for the lower styrene ESI, as is characteristic of a semicrystalline material. The amorphous ESI exhibit an intense loss process associated with the amorphous phase Tg(ESI). The width of this loss... 

Figure 26.2 Dynamic mechanical spectroscopy (DMS) plot of tan<5 versus temperature, measured at 10rad/s, for a series of ESI with styrene incorporation ranging from 24 (ES24) to 77wt% (ES77)...

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