Effects of heat during cure and elongation?
Effects of heat during cure and elongation?
(OP)
All things equal with a BPO/DMA cured vinyl ester laminate (.150" thick)60" diameter cylinder with a HDT of 220F:
1. Speed of reaction and ultimate exotherm produced will effect degree of initial cure but also can induce MORE stress into the laminate than a slower cure due to higher shrinkage?
2. Post cure ramped up to 260F - 280F within 60 minutes.
Could this level of heat beyond the HDT create micro cracking and/or reduce the elongation of the resin to the point that could later cause "in service" cracking? In other words, embrittlement?
If so, the advantages of a high elongation resin could be negated by too aggressive post cure and the result might be similar to what you would expect from a more rigid resin system.
1. Speed of reaction and ultimate exotherm produced will effect degree of initial cure but also can induce MORE stress into the laminate than a slower cure due to higher shrinkage?
2. Post cure ramped up to 260F - 280F within 60 minutes.
Could this level of heat beyond the HDT create micro cracking and/or reduce the elongation of the resin to the point that could later cause "in service" cracking? In other words, embrittlement?
If so, the advantages of a high elongation resin could be negated by too aggressive post cure and the result might be similar to what you would expect from a more rigid resin system.





RE: Effects of heat during cure and elongation?
Too high a temperature will induce chemical degradation and embrittlement.
The built in stress part of the question is a little more tricky to explain but is understood. A great treatment can be found in my friend Jakob Lange's PhD thesis from KTH in Stockholm.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Effects of heat during cure and elongation?
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry
RE: Effects of heat during cure and elongation?
The problem highlights issues that can arise when publishing generalized data on a highly focused subject such as ultimate cure and there is not enough consideration for the possible deleterious effects.
We performed a simple experiment today and it was quite clear that heat above the HDT creates significant embrittlement/cracking with only slight bending. A similar sample subjected to heat below the HDT would not crack even when bent in half but rather snapped at the breaking point.
RE: Effects of heat during cure and elongation?
If you then heat to a new temperature, higher than the original cure temperature, then cure will resume until Tg reaches the new Tcure.
Chris DeArmitt PhD FRSC CChem
www.phantomplastics.com
Consultant to the plastics industry