Solid mechanics measurement techniques

It is through the solid state characteristics of polymers that we - as users - primarily interact with them. For convenience, we can divide the principal properties of polymers into five categories mechanical, optical, surface contact, barrier, and electrical. Weather resistance is a sixth category that can influence each of the other five categories. In order to understand these properties we must be able to quantify them. In this chapter we shall concentrate on measurement techniques, since it is through these methods that we learn how a polymer will behave during use. 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

In an attempt to understand the combustion mechanism of catalyzed double-base propellants, several investigators have conducted experiments to measure the burning rates of strands of liquid nitrate esters. The various measurement techniques were very similar to that employed in a conventional solid propellant strand burner. The liquid esters were placed in a tubular container, and the liquid surface regression speeds were measured by optical methods or by the fuse-wire method used in solid-propeUant strand burners. The only important difference between the solid and the liquid strand burning-rate measurements is that the liquid strand burning speed is very much dependent on the diameter of the container. 

Any motion occurring within any polymer system leads to a change of the dynamic mechanical behaviour, in particular its mechanical loss. This makes the dynamic mechanical measurements the most appropriate technique for studying solid-state transitions. However, in order to assign the molecular motions involved in the considered transition from only the dynamic mechanical results, it is necessary to perform systematic studies on a large series of compounds with gradual modification of their chemical structure. Such an approach has been used in some cases, but it requires lots of effort in synthesising the various compounds. 

In another paper in this issue [1], the molecular motions involved in secondary transitions of many amorphous polymers of quite different chemical structures have been analysed in detail by using a large set of experimental techniques (dynamic mechanical measurements, dielectric relaxation, H, 2H and 13C solid state NMR), as well as atomistic modelling. 

Both liquid and solid material can be suspended in a gas by a variety of mechanisms. Aerosols produced under laboratory conditions or by specific generating devices may have very uniform properties that can be investigated relatively easily by physical and chemical instrumentation. Natural aerosols found in the atmosphere are mixtures of materials from many sources that are highly heterogeneous in composition and physical properties. Their characterization has required the application of a variety of measurement techniques and has been a major activity in modern aerosol science. 

Measurement techniques of the elastic moduli, 388 Mechanical behaviour and failure, 819 Mechanical comfort, 879 Mechanical properties of solid polymers, 383 various materials, 389 Melt/Melting, 167, 700 elasticity, 316 expansion, 97 flow index, 801, 802 flow rate diagram, 801 fracture, 578 number, 579 strength, 799, 812 Merkel number, 59 Mesogenic groups, 34 in the main chain, 177 side-chain, 179 Mesogenic polymers, 172... 

A detailed physical chemical interpretation of permeation mechanisms in microporous membranes is possible if the specific surface of the membrane is determined. Such a determination is mostly done by measuring gas adsorption in the solid although microscopic techniques such as scanning electron micros-... 

In present study, thermo-chemical-induced crosslinking of PTFE has been demonstrated by using fluorinated-compound without any other catalyst materials. Characterization of crosslinked PTFE, which was obtained by radiation and chemical crosslinking, has been studied by various measurement techniques, such as thermal analysis (DSC, TGA), mechanical test, solid-state 19F-NMR spectroscopy, and so on. 

If the idealized concept of fluid film failure proposed above is to have any significance in the world of experimental mechanics and engineering, we must find a basis for its validity and utility. The study of fluid film failure in a practical sense then becomes the study of the behavior of the boundary surfaces of the solids and of the intervening fluid lubricant as the thickness of the lubricant film approaches zero. An important aspect is the reliability of the measurement technique for very thin films. We must be careful not to think of fluid film failure as rupture or breakdown by exceeding the intrinsic strength of the lubricant material. Bulk liquid films do not behave in that way. We know by hydrodynamic theory that the pressure a film of fluid is able to... 

In micro- and nanoscale fluid mechanics, measurements of mass transport and fluid velocity are used to probe fundamental physical phenomena and evaluate the performance of microfluidic devices. Evanescent wave illumination has been combined with several other diagnostic techniques to make such measurements within a few hundred nanometers of fluid—solid interfaces with a resolution as small as several nanometers. Laser Doppler velocimetry has been applied to measure single-point tracer particle velocities in the boundary layer of a fluid within 1 pm of a wall. By seeding fluid with fluorescent dye, total internal reflection fluorescence recovery after photobleaching (FRAP) has been used to measure near-wall diffusion coefficients and velocity (for a summary of early applications, see Zettner and Yoda [2]). 

The NMR techniques were also used to analyze different structural, surface reactions, reaction mechanisms, and other aspects related to the surface chemistry of silicas. For instance. Brunet et al. (2008) studied the electron irradiation effects on controlled-pore borosilicate glasses (CPGs at 8 and 50 nm in pore size, 96% Si02 and 3% B2O3) using multinuclear solid-state NMR technique. H MAS NMR was used to study the surface proton sites. They showed that the irradiation leads to a dehydration of the material. The observed variation of the Q4, Q3, and Q2 species from H- Si CPM AS spectra showed an increase of the surface polymerization under irradiation, implying in majority a Q2 to Q3/Q4 conversion mechanism, and CPMAS measurements exhibited an increase in... 

In siammary, the preliminary results presented in this contribution already demonstrate that time resolving polarization spectroscopy offers a number of favourable and new features for direct observation of fast evolving events on a femtosecond time scale and detection of oscillations up to the THz-range. The described technique can be applied to free atoms, liquids and solids to measure coherent transients in groimd and excited states. Since the observed beats result from an atomic interference effect, narrow structures which may be hidden by inhomogeneous broadening mechanisms can still be resolved. 

P.R. Williams, R.L. Williams, R. Jones, A. Al-Hussany, S. Ravji, New techniques in sol-gel characterisation—mechanical measurements and fractal characteristics. J. Non-Cryst. Solids 293-295, 731-745 (2001). doi 10.1016/S0022-3093(01)00852-3 A. Wittmar, D. Ruiz-Abad, M. Ulbricht, Dispersions of silica nanoparticles in ionic liquids investigated with advanced rheology. J. Nanopart. Res. 14, 651 (2012). doi 10.1007/sll051-011-0651-1... 

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