Testing methods dynamic mechanical analysis

ASTM E 1640-99, ASTM Book of Standards 2002. Standard Test Method for Assignment of the Glass Transition Temperature by Dynamic Mechanical Analysis . ASTM International, Conshohocken, PA. 

A convenient method for determining transition times and transition temperatures of polymeric materials is dynamic mechanical analysis. One type of instrument which is particularly suitable for polymeric solids is the freely oscillating torsion pendulum (TP). Advantages of the TP include its simplicity, sensitivity, relatively low frequency ( 1 Hz) which permits direct correlation of transition temperatures with static nonmechanical methods (e.g., dilatometry and calorimetry), and its high resolution of transitions A major disadvantage of the conventional TP is that test temperatures are limited by the inability of materials to support their own weight near load-limiting transition temperatures. 

Glass transition temperature, Tg, and storage modulus, E , were measured to explore how the pigment dispersion affects the material (i.e. cross-link density) and mechanical properties. Both Tg and E were determined from dynamic mechanical analysis method using a dynamic mechanical thermal analyzer (DMTA, TA Instruments RSA III) equipped with transient testing capability. A minimum of 3 to 4 specimens were analyzed from each sample. The estimated uncertainties of data are one-standard deviation. 

Pellicle and tea-immersed pellicle were analyzed using nanoDMA (dynamic mechanical analysis) to see if the tannins had an effect on the viscoelasticity of the pellicle. NanoDMA is a technique used to study and characterize mechanical properties in viscoelastic materials. The method is an extension of nanoindentation testing [58, 59], An analysis of the nanoindentation load-depth curve gives the hardness (H) and reduced elastic modulus (E ), provided the area of contact, A, between the indenter tip and the sample is known [ 13]. By... 

While TMA is one of the older and simpler forms of thermal analysis, its importance is in no way diminished by its age. Advances in DSC technology and the appearance of dynamic mechanical analysis (DMA) as a common analytical tool have decreased the use of it for measuring glass transitions, but nothing else allows the measurement of CTE as readily as TMA. In addition, the ability to run standardized material test methods at elevated temperatures easily makes TMA a reasonable alternative to larger mechanical testers. As the electronic, biomedical, and aerospace industries continue to push the operating limits of polymers and their composites, this information will become even more important. During the last 5 years a major renewed interest in dilatometry and volumetric expansion has been seen. Other thermomechanical techniques will also likely be developed or modernized as new problems arise. 

Probably the most convenient and most widely used methods arc specific heat using DSC (see Section 2 in this chapter and Section 5 in Chapter 24) and dynamic mechanical analysis (see Chapter 21). However, a range of methods have been tried and reported on in the literature, from volume change to refractive index. For rubbers a measure can be obtained from the low temperature tests discussed in Section 5, Practically, the glass... 

It is important when conducting expensive test programmes that the constituents be checked for quality prior to use and that the fabricated materials be checked after manufacture, or on receipt if already fabricated. The techniques used vary from the Barcol hardness test (see below) to the more rigorous DMA (dynamic mechanical analysis ISO 6721 (ten parts) [14]) or DSC [differential scanning calorimetry ISO 11,357 (7 parts) [15]) test methods. There is some concern that these tests do not give the same values due to subtle variations between different manufacturers equipment. 

E 1640 (1999) Test method for assignment of the glass transition temperature by dynamic mechanical analysis E 1641 (1999) Test method for decomposition kinetics by thermogravimetry... 

Dynamic-mechanical analysis (DMA) is a versatile method for measuring viscoelastic values over a wide frequency range commonly the modulus of elasticity and the damping values are determined. Moreover the testing method is used to investigate material behaviour as a function of temperature (e.g. for determine the glass transition temperature). 

ASTM (1994) E1640-94. Standard Test Method for Assignment of the Glass Transition Temperature by Dynamic Mechanical Analysis, American Society for Testing and Materials, Philadelphia, PA. Tomblin, )., Salah, L., and Ng, Y. (2001) Determination of Temperature/Moisture Sensitive Composite Properties. DOT-FAA Report DOT/FAA/AR-01/40, Office of Aviation Research, Washington, DC. Bai, Y., Post, N.L, Lesko, J.J., and Keller, T. (2008) Experimental investigations on temperature-dependent thermophysical and mechanical properties of pultmded GFRP composites. Thermochim. Acta, 469, 28-35. 

Composition profiles generated by interdiffusion in the concentrated regime between polyphenylene oxide-polystyrene blend pairs were experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (dynamic mechanical analysis (DMA)) were used to determine interphase composition profiles. Confocal micro-Raman spectroscopy was also used to measure local compositions along a direction which was perpendicular to the original interface. The study included some limiting cases to test accuracy, precision and flexibility of the DMA method. 4 refs. 

Other test methods for interface adhesion include short-beam shear and dynamic mechanical analysis (88,113,114). 

Treny and Duperray [32] have pointed out that issues of human comfort relating to noise and vibration are one of the major priorities for materials structural research and development in the field of transportation. Dynamic mechanical analysis (DMA) testing provides a way to characterise in an accurate manner the viscoelastic properties of all the material used in vehicle interiors. Using a unique database software allowed easy material selection according to their viscoelastic properties. An approach for the optimisation of materials through the combination of selective database software and specific numerical calculation methods, to predict the final acoustic behaviour during the materials selection and systems development period are presented. 

Two manifestations of linear viscoelasticity are creep and stress relaxation-, the respective two testing methods are known as transient tests. One can also apply sinusoidal load, an increasingly more used method of study of viscoelasticity by dynamic mechanical analysis (qv) (DMA). We shall now briefly discuss each of these three approaches. 

There are three fundamental test methods for characterization of the viscoelastic behavior of polymers creep, stress relaxation, and dynamic mechanical analysis. Although the primary focus for this chapter is DMA, it is useful first to discuss the fundamentals of creep and stress relaxation, not only because they are conceptually simpler but because most DMA instruments also are capable of operating in either a creep or stress relaxation mode. All three of the methods are related, and numerical techniques are available for calculating creep and stress relaxation data from dynamic mechanical data (Ferry 1980). 

Lu, X., and Isacsson, U., Characterization of Styrene-Butadiene-Styrene Polymer Modified Bitumens-Comparison of Conventional Methods and Dynamic Mechanical Analysis, J. Testing and Evaluation, JTEVA, 25(4) 383-390 (1997)... 

While pressure sensitive adhesive performance at various temperatures can be determined by practical tests, as described above, it is also possible to predict the temperature performance of pressure sensitive adhesives. The polymers used in pressure sensitive adhesives will have a variety of glass transition temperatures (Tg), and for a pressure sensitive adhesive to be effective, the formulated mass must have a Tg of between 50°C and 70°C below the temperature at which the adhesive is to be used. At the same time, however, the Tg cannot be so low that the adhesive mass is so soft that it fails cohesively even at room temperature. A variety of analytical techniques used to determine the Tg of the adhesive mass include Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA), and Dynamic Mechanical Analysis (DMA). Of these, the most commonly used method is DMA. DMA will measure the bulk properties of the adhesive mass, which will include the base polymer and any additives in it. It does not take into consideration any interfacial relationships between the adhesive and the surfaces to which it is bonded. 

---