Enhancing the performance of an epoxy resin using oligomeric amide additives
An antiplasticizer is any chemical that when added, reduces the free volume of a polymer thereby restricting the polymeric chain motions. This type of additive usually increases the modulus and strength but can compromise other important properties such as glass transition temperature and thermal degradation profile. Oligomeric amide additives, which when mixed with TGDDM and DDS, react to form strong hydrogen bonds and reduce the free volume in the system, were synthesized. The nonaromatic additives, especially those that have shorter methylene sequences, had low solubility in the resin, while the mixed amide oligomer additive have better solubility. The effect of these additives to enhance mechanical properties was tested by tensile testing and fracture toughness measurement. Compact tension results indicated that the additives improved the resins’ resistance to crack propagation. In general, when the additive is shorter and additive loading is lower, the material performs better. No general conclusion can be arrived at from the tensile testing due to the variablility of results caused by unavoidable imperfections incurred during specimen preparation. The cure kinetics of the resin was studied using Differential Scanning Calorimetry. Dynamic temperature scanning DSC indicated that the cure reaction was not affected significantly by these additives. However, an increase in activation energy was observed. TMA experiments on resins with nonaromatic additives indicated that the additives slightly increased the softening temperature while DMA experiments on resins with mixed amide oligomers show that the additives slightly increase the glass transition temperature. TGA experiments on resins with mixed amide oligomers indicated that the additives did not introduce significant changes in thermal stability.
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