Recently in working on establishing the correct Tg of the SMP material, it was found that the previous paper used for the mixing formula had calculated the mixing ratios in error. Therefore, I have cited the original paper here and present the newly calculated volume mix ratios to obtain the desired Tg value. The shape memory polymer I am using is mixing three materials Epon 826, Jeffamine D230, and Neopentyl glycol diglycidyl ether (NGDE). The proper mix ratios for these substances is given in the table below as used by Xie et. al. (1).
In order to determine the volume mix ratios the molecular weights given in (2) and the density of each material given in (3)-(5) are used. These values are listed below:
- Epon 826: 364.055 g/mole, 1.16 g/ml
- Jeffamine D230: 230 g/mole, 0.948 g/ml
- NGDE: 216 g/mole, 1.04 g/ml
Note that the molecular weight of the Epon 826 is calculated from the chemical structure seen above. Therefore, the new mix ratio for each formulation is given as:
NGDE1: 4.7 ml Epon 826/2.43 ml Jeffamine/1 ml NGDE
NGDE2: 3.14 ml Epon 826/2.43 ml Jeffamine/2.08 ml NGDE
NGDE3: 1.57 ml Epon 826/2.43 ml Jeffamine/3.12 ml NGDE
NGDE4: 0 ml Epon 826/2.43 ml Jeffamine/4.15 ml NGDE
The Tg for each of the mix ratios is determined by DSC in Xie et. al. (1) whose results are given below:
This paper suggests to heat the Epon 826 at 70 C in a oven to melt it for 15 minutes. Then place the appropriate amounts of Jeffamine D230 and NGDE into the bottle and shake vigorously for 10 seconds. Pour the mixture into the mold and cure at 100 C for 1.5 h and post cured at 130 C for 1 h. Then cool and demold the samples.
The next step in my research is to try to modify this new procedure to properly incorporate nano fibers into the polymer matrix and see the change in mechanical properties.
1. Xie, T., Roussea, K., Facile tailoring of thermal transition temperatures of epoxy shape memory polymers, Polymers, 2009, 50, 1852-1856.