Penetration probes

The sample sandwich described above is placed in the TMS, the screw cap is closed and the closed tube is flushed with nitrogen via small inlet and outlet ports. Next the transducer shaft is lowered till it touches the upper plate. A thin, flat ended TMS penetration probe was used as the transducer shaft throughout the experiments. 

The structure Is an NPNN transistor. The lowest plot was done several years ago with 20 gram penetrating probes the middle plot shows the Improvement obtained at that time by using a... 

Figure 5. Spreading resistance profiles of an NPHIT transistor structure, as measured with penetrating probes and with controlled low penetration probes. Reproduced with permission from Ref. 5. Copyright 1984 American Society for Testing and Materials.

TMA s were run over a temperature range of -20°C to 210°C on a Perkin Elmer Thermomechanical Analyzer IMS-1. They were run with a 40 mil diameter penetration probe loaded with 200 grgms to give a pressure of 394 psi. The program rate was lOC/min. under a helium atmosphere and the Y-axis sensitivity... 

Tdec), the temperatures for maximum degradation rate (Tmax), and char yield at 545 °C (CY) measured using the thermogravimetric analyses (TGA), and by the Tg measured using a thermomechanical analyzer (TMA) with a penetration probe. Tdec is noted as the point where the extrapolations of the two slopes in the TGA curve intersect. The Tg was measured using a thermomechanical analyzer (TMA) with a penetration probe. 

Man, P, Montagner, C., Vitrac, H., et al. (2011) Accessibility changes within diphtheria toxin T domain upon membrane penetration probed by hydrogen exchange tmd mass spectrometry. Journal of Molecular Biology, 414 (1), 123-134. 

TMA consists of a quartz probe which rests on top of a flat sample (a few mm square) in a temperature controlled chamber. When set up in neutral buoyancy then as the temperature is increased the probe rises in direct response to the expansion of the sample yielding thermal expansion coefficient versus temperature scans. Alternatively, with a penetration probe under dead loading a thermal softening profile is obtained (penetration distance versus temperature). Although this is a simple and versatile experiment, it gives only a semi-quantitative indication of mechanical modulus versus temperature. 

Figure 4.59 TMA curves for (I) PE, (II) PP and (III) nylon obtained using a penetration probe (79). Load, 10 g heating rate, 5 C min ...

A temperature calibration procedure for TMA has been proposed (53-55) and subsequently included as an ASTM method (Test Method for Temperature Calibration of Thermomechanical Analyzers, E1363-90). It uses a penetration probe and the melting temperature of one or more standard materials. Pure metals with sharp melting points are the standards often used. An open DSC pan may be used to contain the calibrant material. Another potential material would be the selected shape memory alloy, reported to be reproducible to 1°C (56). Several reviews on temperature calibration for TMA have been published based on ASTM efforts in this area (54,55). Sircar (26) suggests that, when used for elastomer evaluation, temperature calibration for TMA should be conducted with low melting liquids as in DSC. For calibration of the expansion, one manufacturer s manual (TA Instruments) recommends aluminum for calibrating the linear expansion parameter. Other calibration standards suggested for the linear coefficient of thermal expansion (CTE) are lead (57) and copper (58). 

Penetration Mode. TMA in the penetration mode can be used to evaluate the degree of cure of thermoset materials (64). A large load (typically, 10-100 g or 0.1-1.0 N) is employed for these experiments. The probe measures the softening associated with the large decrease in modulus as the temperature approaches Tg. The softening point correlates well with Tg (65,66). The penetration probe referred to in Figure 28 is a small-radius (0.48 mm) hemispherical probe. The... 

Fig. 30. Evaluation of the degree of cure of an elastomer by TMA penetration probe sample is a carbon black filled rubber stopper (69).

In a similar attempt, Hatano and Ishida (1986) studied the particle gas mass transfer coefficient in a three-dimensional fluidized bed of nonadsorbing glass beads with = 0.18 mm using optical fiber probes. Tracer gas concentrations in and around rising single bubbles was measured continuously by the penetrative probes, while the bubble boundary and the zone with the prominent particle movement were detected by... 

Flat bulk sample significant load Penetration probe Significant load Linear displacement (depth of Temperature Softening and melting... 

Figure 4.11. Results for a TMA penetration-mode experiment on a multilayer film. Total film thickness was 114 pm. A heating rate of 5 CYmin was used, and a penetration probe was employed under 0.1 N loading. (TA-108,TA Instrnments Thermal Analysis Application Notes, courtesy of of TA Instruments).

Figure 10.7 Schematic presentation of the Perkin-Elmer thermal mechanical analyser (top). Bottom left expansion probe for measurement of linear thermal expansion coefficient. Bottom right penetration probe for measurement of stiffness.

Thermal expansion coefficients are determined by thermomechanical analysis using a dilatation-penetration probe for adhesive pastes and an extension probe for self-standing films. The output of the thermal analyzer equipped with a dilatation probe is a curve plotting the variation of adhesive thickness as a function of the temperature. 

Olive, P. L. Durand, R. E. Characterization of a carbocyanine derivative as a fluorescent penetration probe. Cytometry 1987, 8, 571-575. 

Figure 10. TMA curves of a PPy/p-TS film, penetration probe with 5 g load, heating rate 5 C/min (a) initial heating (b) reheat of (a) after overnight ambient exposure.

Thermal mechanical analysis can be used to assess the glass transition of a thin film system. The sample is placed in a temperature-controlled chamber for analysis. Two different probes can be used with thermal mechanical analysis (TMA) a flat probe or a penetration probe. The flat probe measures the thermal expansion of the polymer as the temperature is increased. Very little load is applied, so an accurate measure of change in dimension can be reported. Conversely, the penetration probe can have up to 1.0 N of force placed on the sample. The probe pushes into the sample as it softens to give a crude modulus (or compliance) value or a temperature associated with a... 

As the system was heated, it expanded giving a constant increase in probe position. At the onset of the glass transition, the penetration probe should depress into the softening polymer. This depression appears to the instrument as if it observed a... 

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