Thermomechanical analysis sample probes

Thermomechanical-analysis (TMA) testing is used to measure a material s expansion coefficient above and below the glass-transition temperature or Tg. Thermomechanical analysis continuously monitors the expansion of a probe on a sample as a function of temperature. The standard test method for TMA is ASTM D3386, Coefficient of Linear Thermal Expansion of Electrical Insulating Materials.In addition to the glass-transition temperature or Tg, the expansion coefficients above and below Tg are reported. 

Thermomechanical analysis (TMA), e.g. [50]. The sensitivity of TMA is comparable with that of DMT A. In contrast to DSC and DMT A, the measurement is not the average over the whole sample but an average of the properties of a certain part of the sample that is limited by the shape of the tip of the probe. Direct measurements of the expansivity are possible which give access to the free volume and the relaxation behavior of the polymer chains [93-95]. 

Dilatometry and thermomechanical analysis (TMA) are also techniques used to monitor the thermal behavior of fibers. They both employ a sensitive probe in contact with the surface of the sample, and the thermal transitions are detected either by a change in volume or modulus of the sample, respectively. In the latter case, the probe necessarily penetrates the sample surface. A variable transformer records the voltage output that is directly proportional to the degree of displacement of the probe during a thermally induced transition. TMA is a more sensitive technique than either DTA or DSC for detecting thermal transitions. 

Thermomechanical analysis (TMA) is the measurement of dimensional changes (such as expansion, contraction, flexure, extension, and calorimetric expansion and contraction) in a material. It is measured by the movement of a probe which is in contact with the sample in order to determine temperature-related mechanical behaviour in the temperature range of 180-800 °C. This occurs as the sample is heated, cooled (temperature plot), or held at a constant temperature (time plot). It also measures linear or volumetric changes in the dimensions of a sample as a function of time and force. 

In thermomechanical analysis (TMA), the change in mechanical properties is measured as a function of temperature and/or time. A probe in contact with the sample moves as the sample undergoes dimensional changes. The movement of the probe is measured with an LVDT. The sample deformations that can be measured are compression, penetration, extension, and flexure or bending. 

Thermomechanical analysis (TMA) measures the deformation of a material contacted hy a mechanical prohe, as a function of a controlled temperature program, or time at constant temperature. TMA experiments are generally conducted imder static loading with a variety of probe configurations in expansion, compression, penetration, tension, or flexime. In addition, various attachments are available to allow the instrument to operate in special modes, such as stress relaxation, creep, tensile loading of films and fibers, flexural loading, parallel-plate rheometry, and volume dilatometry. The type of probe used determines the mode of operation of the instrument, the manner in which stress is apphed to the sample, and the amount of that stress. 

Thermomechanical analysis involves measuring variations in a sample s volume or length as a function of temperature and/or time. The method is commonly used to determine thermal expansion coefficients as well as the glass-transition temperature of polymer or composite materials. A weighted probe is placed on the specimen surface, and the probe s vertical movement is monitored continuously while the sample is heated at a controlled rate. 

Thermomechanical Analysis. A schematic representation of a t3q)ical thermomechanical analyzer (tma) device is shown in Figure 13. Several such devices are available commercially. The probe and Ivdt assembly are similar to those of the dilatometer described above. The commercial units are generally fitted with a selection of sample probes so that besides thermal expansivity, sample penetration, softening point, and heat distortion under load can also be measured among other quantities. 

A series of polystyrene molecular weight standards available from the Pressure Chemical Company have been studied by Keinath et al. via thermomechanical analysis. AflYs ranged from nominal molecular weight 2,200 up to 7,200,000. Smooth glassy samples, contained in DSC pans, were prepared by fusing the as-received powdered samples. Tlje weighted probe of the DuPont 943 TMA unit was placed onto the surface of the sample and the entire assembly was heated at S C/min from room temperamre up to a point where the probe had penetrated through the whole thickness of the sample. 

Figure 10.18 Photograph of a sample of the fluoroaluminate glass 37AIF3-12BaF2-15CaF2-12MgF2-9SrF2-15Yp3 (molar %) that has undergone thermomechanical analysis (TMA) indentation viscometry with a cylindrical probe. The sample has devitrified during the indentation [35].

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