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Effect of sonication on thermal, mechanical, and thermomechanical properties of epoxy resinSharma, Bed Prasad 01 December 2009 (has links)
Epoxy resin is an important engineering material in many industries such as electronics, automotive, aerospace, etc not only because it is an excellent adhesive but also because the materials based on it provide outstanding mechanical, thermal, and electrical properties. Epoxy resin has been proved to be an excellent matrix material for the nanocomposites when including another phase such as inorganic nanofillers. The properties of a nanocomposite material, in general, are a hybrid between the properties of matrix material and the nanofillers. In this sense, the thermal, mechanical, and electrical properties of a nanocomposite may be affected by the corresponding properties of matrix material. When the sonication is used to disperse the nanofillers in the polymer matrix, with the dispersal of the nanofillers, there comes some modification in the matrix as well and it finally affects the properties of nanocomposites. In this regard, we attempted to study the thermal, mechanical, and dynamic properties of EPON 862 epoxy resin where ultrasonic processing was taken as the effect causing variable. Uncured epoxy was subjected to thermal behavior studies before and after ultrasonic treatment and the cured epoxies with amine hardener EPICURE 3223 (diethylenetriamine) after sonications were tested for mechanical and dynamic properties. We monitored the ultrasonic processing effect in fictive temperature, enthalpy, and specific heat capacity using differential scanning calorimetry. Fictive temperature decreased whereas enthalpy and specific heat capacity were found to increase with the increased ultrasonic processing time. Cured epoxy rectangular solid strips were used to study the mechanical and dynamic properties. Flexural strength at 3% strain value measured with Dillon universal testing machine under 3-point bending method was found to degrade with the ultrasonic processing. The storage modulus and damping properties were studied for the two samples sonicated for 60 minutes and 120 minutes. Our study showed that the 60 minutes sonicated sample has higher damping or loss modulus than 120 minutes sonicated sample.
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A Combined Rheological and Thermomechanical Analysis Approach for the Assessment of Pharmaceutical Polymer BlendsIsreb, Mohammad, Chalkia, Marianiki, Gough, Tim, Forbes, Robert T., Timmins, Peter 08 September 2022 (has links)
Yes / The viscoelastic nature of polymeric formulations utilised in drug products imparts unique thermomechanical attributes during manufacturing and over the shelf life of the product. Nevertheless, it adds to the challenge of understanding the precise mechanistic behaviour of the product at the microscopic and macroscopic level during each step of the process. Current thermomechanical and rheological characterisation techniques are limited to assessing polymer performance to a single phase and are especially hindered when the polymers are undergoing thermomechanical transitions. Since pharmaceutical processing can occur at these transition conditions, this study successfully proposes a thermomechanical characterisation approach combining both mechanical and rheological data to construct a comprehensive profiling of polymeric materials spanning both glassy and rubbery phases. This approach has been used in this study to assess the mechanical and rheological behaviour of heterogenous polymer blends of hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) over a shearing rate range of 0.1–100 s−1 and a temperature range of 30–200 °C. The results indicate that HPC and HPMC do not appear to interact when mixing and that their mixture exhibits the mechanistic properties of the two individual polymers in accordance with their ratio in the mixture. The ability to characterise the behaviour of the polymers and their mixtures before, throughout, and after the glassy to rubbery phase transition by application of the combined techniques provides a unique insight towards a quality-by-design approach to this and other polymer-based solid dosage forms, designed with the potential to accelerate their formulation process through obviating the need for multiple formulation trials.
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