Shrinkage during heating

In tension-mode experiments, essentially zero force should be applied to the sample (such as films or fibers) to measure the tensile properties. However, a small initial force (<2mN) may be applied to the film or fiber sample to keep the sample straight. Care should be taken not to apply more than the necessary initial force, because this can cause creep and sometimes unnecessary orientation. Too high a load may also reduce the level of shrinkage during heating. 

The coke at this stage is called "green" because it still contams 5 to 15 wt% volatile matter. If the coke is to be used as a filler in anode and electrode manufacturing, this high level of volatile matter is considered unacceptable because it contnbutes to shrinkage during subsequent heat treatment and fabrication... 

Thermal conductivity also helps to improve heat transfer during cure. This reduces exothermic temperatures and extends pot life, particularly at high filler loadings. Shrinkage during cure is also reduced, as explained in the sections above. 

Figure 12. Linear shrinkage and skeletal density of a multicomponent borosilicate xerogel during heating in air at 2 °C/min. Skeletal densification accounts for all the shrinkage observed between 250 and 550 °C. (Reproduced with permission from reference 84. Copyright 1986.)...

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