You should be able to determine glass transition (Tg) of your specimen by using Differential Scanning Calorimetry (DSC). However due to your mixing ratio and cured at room temperature, I suspect your specimen is under cured. So, your specimen Tg might still at sub-zero region.

For confirmation, take approximately 5 to 10 mg of cured sample to run a heat cool heat cycle using DSC. First heating cycle start from -80°C to 200°C. Then cool down to 20°C for second heating cycle from 20°C to 200°C. You should get three information from this test.

1. Specimen Tg should be observed from first heating cycle at the region between sub-zero to room temperature. In case you observed relaxation, high chance your Tg signal been masked. This is quite often happen in tropical country where specimen are exposed to moisture during long curing time at ambient. If relaxation observed, use modulated DSC to separate the Tg from relaxation because the former is reversible reaction while the latter is non-reversible reaction [1]. If conventional DSC is used, more steps required but still able to measure Tg after eliminate relaxation. Just carefully not to postcure the sample.

2. Residue cure can be observed as exothermic enthalpy at latter region of the first heating cycle. In this case, your sample is postcuring at the temperature where the exothermic heat flow observed. If residue cure is observed, degree of cure can be calculated by repeat another DSC on freshly mixed resin to obtain total enthalpy of the system [1]. Please take note if mixing ratio changed, the total enthalpy will change and make sure same ramp rate to be used for degree of cure calculation.

3. Full cured Tg can be determined from second heating cycle. This is the Tg of the fully cured system. However, the value is usually lower than freshly mixed sample. If residue cure observed in second heating cycle, the sample is not fully cured. Assuming nothing wrong with the mixing ratio to fully cure the sample, increase final temperature of first heating cycle but be careful not to char the sample. Alternatively, use slower ramp rate to allow enough time for the sample to cure.

Hope explanation above could help you.

Tan

Reference:

[1] Liu et al (2013), Heat transfer analysis and cure modelling of composite repairs for pipelines, Journal of Reinforced Plastics and Composites 2014, Vol. 33(6) 586–597 DOI: 10.1177/0731684413514124

Hi

The Tv will be fall around 63C to maximum of 70C. I have done dsc for many time in this material it gave me this range of Tg only.

Best

@V R Arun Prakash. Can you give me the cure schedule ? Can I cure in room temperature , currently I did so for one week.