Thermal degradation of epoxy/silica composites monitored via dynamic mechanical thermal analysis
ABSTRACT A dynamic mechanical thermal analyzer (DMTA) was used to monitor changes of dynamic mechanical properties during thermal degradation of two types of epoxy/silica composites, both of which are used as electrical insulation in power apparatus. It was found that the peak value of the dynamic loss factor (tan δ), glass transition temperature (Tg), and dynamic storage modulus (E′) above Tg changed considerably with increasing thermal degradation, while E′ at the glassy state only underwent a moderate change with increased thermal degradation. It is concluded that the DMTA technique is very sensitive to the structural changes in the investigated epoxy composites due to the thermal degradation. It is also confirmed by DMTA tests that further cross-linking and loss of dangling chains are occurring slowly during the stage prior to the onset of the severe degradation. © 1992 John Wiley & Sons, Inc.
- SourceAvailable from: dspace.library.iitb.ac.in
[Show abstract] [Hide abstract]
- "DMA is a widely used technique to detect weak glass transitions easily and precisely due to its higher sensitivity as compared to DSC. Hence, it is widely used to investigate relaxation of polymer segments , polymer miscibility  and thermal degradation behaviour  in polymer blends and polymer composites. "
ABSTRACT: High performance polymer matrix composites based on poly(ether–ether–ketone) (PEEK) as matrix and aluminum nitride particle (AlNp) as filler were prepared. The effect of AlNp on the storage modulus, loss modulus, mechanical loss factor, and glass transition were investigated. The AlNp reinforcement is more pronounced above glass transition temperature (Tg). Composite containing 70 wt.% AlNp exhibit about 100% increase in storage modulus at 50 °C and about 500% increase at 250 °C, and 19 °C increase in glass transition temperature as compared to pure PEEK. Peak height of tan δ for composites was decreased to one sixth of the pure PEEK. It is probably due to improved crystallinity of PEEK and strong interaction between the AlNp and PEEK matrix. SEM reveals excellent distribution of AlNp in PEEK matrix and good interaction between AlNp and PEEK matrix.Composites Part A Applied Science and Manufacturing 02/2007; 38(2-38):516-524. DOI:10.1016/j.compositesa.2006.02.017 · 3.01 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Samples of cast bisphenol-A and cycloaliphatic epoxy insulation were quenched from a temperature above T<sub>g</sub> (170°C) to room temperature. Variations in dielectric, thermal and mechanical properties were examined during subsequent sub-T<sub>g</sub> annealing (physical aging). It was found that the impact strength of the epoxy insulation decreased considerably with physical aging. Moisture intake and subsequent dielectric loss at room temperature were also found to decrease with physical aging. Glass transition temperature and excess enthalpy measured by DSC demonstrated significant increase with increased sub-T<sub>g</sub> annealing. On the other hand, dielectric properties showed different changing patterns during sub-T<sub>g</sub> annealing in different epoxy systems. It is concluded that epoxy insulating materials should be properly annealed before assessing their dielectric and other physical properties because of the possibility of unknown rapid cooling historiesIEEE Transactions on Dielectrics and Electrical Insulation 03/1994; 1(1-1):9 - 17. DOI:10.1109/94.300227 · 1.23 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Mechanical behaviour play an important role in the election of an epoxidic formulation of well determined properties as it has a marked influence on both structural and external factors. Temperature and time strongly act on polymers properties owing to their viscoelastic nature. Knowledge of the dynamic moduli and properties of polymeric materials is indispensable for the design of this materials. At the same time, the influence of the temperature on polymers behaviour may be studied once the activation energy is known. In this paper the different dynamic moduli and activation energy are measured using a Perkin Elmer DMA 7. The relationships between the dynamic mechanical properties and the molecular weight of the polymers make possible the calculation of the molecular weight. Results reasonably agree with literature values.Journal of Thermal Analysis and Calorimetry 06/1994; 41(6):1543-1550. DOI:10.1007/BF02549952 · 2.21 Impact Factor