The glass transition temperature (Tg) regions of polymers and composites were studied using static force thermomechanometry and modulated temperature thermomechanometry (mT-TM). Modulated temperature allowed measurement of linear thermal expansion coefficient and glass transition as reversing phenomena, independent of any residual cure and relaxations that are non-reversing in nature. The reversing dimension change curves were well defined with continuous expansion that increased after Tg, though sensitivity decreased with crosslinking and fibre content. The non-reversing dimension change curves showed the maximum variation and revealed complex changes, and the non-reversing characteristics were confirmed by repeated scans, both upon cooling or re-heating. Non-reversing curves showed contractions with increasing temperature. Lissajous figures demonstrated that temperature modulation deviated significantly from linear response in the temperature range below Tg, and during the Tg range, steady state was not maintained. Measurements made in mT-TM mode were compared with modulated force TM where Tg was revealed as a peak in loss modulus or tan(δ), whilst reversing events were consistent with changes in storage modulus.
1. Van Assche, G, Van Hemelrijck, A, Rahier, H, Van Mele, B. Modulated differential scanning calorimetry: non-isothermal cure, vitrification, and devitrification of thermosetting systems. Thermochim Acta. 1996;286:209–224. .
2. Dao, B, Hodgkin, J, Krstina, J, Mardel, J, Tian, WJ. Accelerated aging versus realistic aging in aerospace composite materials. V. The effects of hot/wet aging in a structural epoxy composite. Appl Polym Sci. 2010;115:901–910. .
3. Gahleitner, M, Grein, C, Bernreitner, K, Knogler, B, Hebesberger, E. The use of DMTA for predicting standard mechanical properties of developmental polyolefins. J Thermal Anal Cal. 2009;98:623–628. .
4. Xie, M, Zhang, Z, Gu, Y, Li, M, Su, Y. A new method to characterize the cure state of epoxy prepreg by dynamic mechanical analysis. Thermochim Acta. 2009;487:8–17. .
5. Shepard, DD, Twombly, B. Simultaneous dynamic mechanical analysis and dielectric analysis of polymers. Thermochim Acta. 1996;272:125–129. .
6. Hutchinson, J. Determination of the glass transition temperature. J Therm Anal Cal. 2009;98:579–589. .
7. Yazdi, M, Lee-Sullivan, P. Determination of dual glass transition temperatures of a PC/ABS blend using two TMA modes. J Therm Anal Cal. 2009;96:7–14. .
8. Price DM . Method and apparatus for modulated-temperature thermomechanical analysis, TA Instruments, New Castle. US Patent 6,007,240;1999.
9. Price DM . Modulated temperature thermomechanical measurements. In: Riga AT, Judovits LH, editors. Materials characterization by dynamic and modulated thermal analytical techniques, ASTM STP 1402. 2001: 103–114.
10. Lange, J, Manson, J-AE, Hult, A. Build-up of structure and viscoelastic properties in epoxy and acrylate resins cured below their ultimate glass transition temperature. Polymer. 1996;37:5859–5868. .
11. Kim, YK, White, SR. Stress relaxation behavior of 3501–6 epoxy resin during cure. Polym Eng Sci. 1996;36:2852–2862. .
12. Price, DM. Modulated-temperature thermomechanical analysis. Thermochim Acta. 2000;357–358:23–29. .
13. Wurm, A, Merzlyakov, M, Schick, C. Temperature modulated dynamic mechanical analysis. Thermochim Acta. 1999;330:121–130. .
14. Takegawa, K, Fukao, K, Saruyama, Y. Aging effects on the thermal expansion coefficient and the heat capacity of glassy polystyrene studied with simultaneous measurement using temperature modulation technique. Thermchimica Acta. 2007;461:67–71. .
15. Kociba, K. Temperature calibration of TMAs using modulated temperature and Curie temperature reference standards. J Therm Anal Cal. 2000;60:779–784. .
16. Li, G, Lee-Sullivan, P, Thring, RW. Determination of activation energy for glass transition of an epoxy adhesive using dynamic mechanical analysis. J Therm Anal Cal. 2000;60:377–390. .