Thermomechanical Testing of Plastics for Environmental Resistance

Dynamic mechanical analysis (DMA) is the technique of applying a stress or strain to a sample and analyzing the response to obtain phase angle and deformation data. These data allow the calculation of the damping or tan δ; the storage, loss, and complex modulus; as well as complex viscosity and complex compliance. Two approaches are used: (i) forced frequency, where the signal is applied at a set frequency and (ii) free resonance, where the material is perturbed and allowed to exhibit free resonance decay. Most modern DMA instruments are of the forced resonance type. In both approaches, the technique is very sensitive to the motions of the polymer chains and it is a powerful tool for measuring transitions in polymers. It is estimated to be 100 times more sensitive to the glass transition than differential scanning calorimetry (DSC) and resolves other more localized transitions not detected in DSC. In addition, the technique allows the rapid scanning of a material's modulus and viscosity as a function of temperature or frequency. DMA may also be referred to as dynamic mechanical thermal analysis (DMTA), dynamic mechanical spectroscopy (DMS), or dynamic thermomechanical analysis (DTMA).

Dynamic Mechanical Analysis of Polymers and Rubbers

Menard¹,

Bilyeu²

2008

Dynamic Mechanical Analysis

Menard

2017

Fundamental aspects of biomineralization may be important in order to understand and improve calcification onto the surface of biomaterials. The biomineralization process is mainly followed in vitro by assessing the evolution of the apatite layer that is formed upon immersion of the material in Simulated Body Fluid (SBF). In this work we propose an innovative methodology to monitor apatite deposition by looking at the evolution of the mechanical/viscoelastic properties of the sample while immersed in SBF, using non-conventional dynamic mechanical analysis (DMA) performed under distinct displacement amplitudes (d). The biomimetic biomineralization process in composite membranes of chitosan (CTS) with Bioglass® (BG) was followed by measuring the change of the storage modulus, E′, and the loss factor, tan δ, at 37°C and in SBF, both online (d = 10 μm and d = 30 μm) and offline (d = 0 μm). The online experiments revealed that the E′ decreased continuously up in the first hours of immersion in SBF that should be related to the dissolution of BG particles. After that, an increase of the stiffness was verified due to the apatite deposition. SEM/EDS observations upon 24 h of immersion in SBF showed higher development of apatite deposition with increasing displacement amplitude.

Dynamic Mechanical Analysis

Ménard

Menard

2023

Dynamic mechanical analysis ( DMA ) is applying a stress or strain to a sample at controlled frequencies and analyzing the response to obtain phase angle and deformation data. These data allow the calculation of the damping or tan delta (δ) as well as complex modulus and viscosity data. Two approaches are used: (i) forced frequency, where the signal is applied at a set frequency, and (ii) free resonance, where the material is perturbed and allowed to exhibit free resonance decay. Most DMAs are of the former type, while the torsional braid analyzer ( TBA ) is of the latter type. In both approaches, the technique is very sensitive to the motions of the polymer chains, and it is a powerful tool for measuring transitions in polymers. More specialized techniques, such as the use of ultrasonics and laser pulses, do exist in specialized markets. It is estimated to be 100 times more sensitive to the glass transition than differential scanning calorimetry ( DSC ), and it resolves other more localized transitions, such as side chain movements that are not detected in the DSC. In addition, the technique allows the rapid scanning of a material's modulus and viscosity as a function of temperature, strain, or frequency. DMA may also be referred to as dynamic mechanical, thermal analysis ( DMTA ), dynamic mechanical spectroscopy ( DMS ), or dynamic thermomechanical analysis ( DTMA ).