Thermomechanical analyzers

Fig. 39. Schematic of the TA Instmments model 2940 thermomechanical analyzer. LVDT = linear variable differential transducer.

To measure the thermal expansion coefficients, a 0.125 in. thick sample was taken from the cured plates. The Increase in length with temperatures was measured by use of a Dupont 941 Thermomechanical Analyzer (TMA), with a heating rate of 5°C/min. The instrument was calibrated with an aluminum standard. Three runs were made for each sample and standard deviations calculated. 

A TMS-2 Thermomechanical Analyzer (Perkin-Elmer) was used to determine the glass transition temperatures of t e ionomer pseudo-IPNs at temperatures ranging from -100°C to +100°C and 0.01 mm of penetration range, 80g of penetrating weight, and a heating rate of 10°C/min. 

A du Pont model 940 thermomechanical analyzer was employed for the Tg measurements on the PEMA/PVdF polyblends by the TMA technique. The sample specimens were cut from 30-mil, melt pressed sheets of the respective blends and examined by heating from —60° to 100°C at a rate of 5°C/minute. Sharp, unambiguous transitions were observed. 

Figure 1. The Ferkin-Elmer laboratory for thermal analysis. From left to right the DSC-1B differential scanning calorimeter with evolved gas analyzer, the TGS-1 thermobalance (top to bottom), the recorder chart control, model UU-1 temperature programmer control, and model TMS-1 control unit. At right is the model TMS-1 thermomechanical analyzer.

The apparent melting temperature obtained for various acylated wood prepared by both the TFAA and the Chloride methods by using the thermomechanical analyzer under a pressure of 3 Kg/cm are shown in Table IV. The acylated wood samples prepared by the TFAA method show somewhat lower apparent melting temperatures compared with those prepared by the Chloride method. 

Thermal analysis on a DuPont 900 thermomechanical analyzer provided additional information on transition temperatures. A blunt-end expansion probe was used with heating rates in the range of 5°-10°C/min. 

Using a thermomechanical analyzer (TMA) as the parallel-plate rheometer, the neat resin was laminated under identical conditions as did the prepreg to deteraiine the viscosity history. Throughout this study, the quartz probe (0.145 in. in diameter) which is attached to a linear variable differential transfomier for thickness monitoring exerted a constant force of 2... 

Table I gives the summary of CTE measurements made on neat and filled XYDAR molded parts. These CTE measurements were performed in a temperature range from 0-150 °C using a DuPont 942 thermomechanical analyzer (TMA). The CTE s shown in Table I are measured in the flow, transverse, and thickness directions for the formulation and part geometry specified. In a part of center-gated geometry, the radial direction is the flow direction and the circumferential direction is the width direction. All of the TMA testing was performed on aB-molded samples (no annealing).

For softer, rubbery polymers, a different experimental procedure gives better results. For these experiments we have measured directly the penetration distance of a tiny weighted probe into the cross-sectioned surface of polymer samples. For this purpose we have made use of a Perkin-Elmer Thermomechanical Analyzer equipped with a tip modified to be small enough to provide measurements of the desired resolution. (We are currently using a conical diamond phonograph needle having a tip angle of 60°.)... 

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. 

The Mettler TMA 40 thermomechanical analyzer is illustrated in Figure 11.3. A measuring sensor applies a user-definable force to the sample of -0.05-0.5 N. The position of the sensor is continuously monitored by a LVDT. TMA measurements can be made in the temperature range -100-1000 C. This module is part of the Mettler TA 3000 thermal analysis system. 

Thermomechanical Analysis. A thermomechanical analyzer (Perkln-Elmer TMS 2) was used to measure glass transition temperature (Tg) and coefficient of thermal expansion (a ) of completely cured samples In the penetration and expansion modes respectively. Experimental conditions are listed In Table I. 

There are currently no standards tests for measuring the thermal expansion of plastics in ISO or in BS 2782. In ASTM, test method D696 [124] uses a relatively thick test piece, which is placed in a chamber whose temperature can be controlled. This is shown schematically in Fig. 23. The expansion of the sample is transmitted to a remote dial gauge via a quartz rod that has a very low expansion coefficient. This same technique is applied in modern thermomechanical analyzers (TMA). but the dial gauge is replaced by linear displacement transducers or other electronic devices capable of detecting smaller dimensional changes. In turn this allows thinner specimens to be tested and permits wider temperature ranges to be examined. There are developments wnthin the ISO to provide a standard for these types of instruments. 

Figure 1 Percentage swelling of a 5 mm x 8 mm x 5 mm oven dry block of aspen wood immersed in liquid pMDI, measured at 24.3 0.4°C in air, in the tangential direction using a thermomechanical analyzer. The inset shows the initial 30 min. 

Figure 12 shows the use of the IMS-2 Thermomechanical System with an expansion probe to establish the average coefficient of linear expansion of the Process 1 residue in the temperature range from 60°C to 140°C. As is shown in the figure, the expansion coefficient was calculated to be 4.56 X 10". An exploratory run using the expansion probe in the TMS-2 Thermomechanical Analyzer... 

The glass transition temperatures were estimated from deformation tests performed on the very same pellets which were used for x-ray studies. The tests were made by means of a Perkin-Elmer Thermomechanical analyzer TMS-l, calibrated with polystyrene and polymethylmethacrylate. C-13 NMR Spectra were run in deu-terated chloroform at 10wt% concentration and at 450C. A JEOL PFT-100 spectrometer was used (resolution ... 

A schematic diagram illustrating a typical thermomechanical analyzer is shown in Fig. 4.146. This instrument was produced by the Perkin-Elmer Co. Temperature is controlled through a heater and the coolant at the bottom. Atmosphere control is possible through the sample tube. The heavy black probe measures the position of the... 

Thermomechanical analyzers are available for temperatures from as low as 100 K to as high as 2,500 K. Basic instruments may go from 100 to 1,000 K with one or two furnaces and special equipment for liquid Nj cooling. For higher temperatures. 

Some of the cured materials were examined with a Perkin-Elmer 621 Grating Infrared Spectrophotometer to monitor the curing characteristics of the maleimide/meth-acrylate monomer mixtures. Thermal analysis was also performed with a Perkin-Elmer DSC-2 Differential Scanning Calorimeter and a Perkin-Elmer TMS-2 Thermomechanical Analyzer. 

---