Local melting kinetics of folded chain polymer crystals

The structure of semicrystalline polymers is very complex due to the existence of entanglements in the equilibrated melt and the fact that the length of a molecule is significantly larger than the characteristic dimension of the crystals. The consequence is the formation of non-ideal folding crystals and an increased entanglement concentration in the remaining disordered regions. This is the reason for specific phenomena such as the formation of a rigid amorphous fraction which is not involved in the glass transition, reorganization during heating, the high tendency on superheating and relaxation processes in the melt. Such processes could have a retarding effect on melting. Various models for melting kinetics are developed and discussed, which consider the different influences of the retarding effects on the time dependence of the melting rate. These models are tested by measurement of the complex heat capacity of various polymers. The measurements are performed using temperature-modulated DSC. The experimental requirement for the measurement conditions are discussed. • Retarding effects for melting in the metastable structure of polymers are discussed • Kinetic models of the local melting of polymer crystals are derived • The complex heat capacity is sensitive to these local processes • Three different scenarios are discussed and could be verified. • Experimental requirements for temperature modulated DSC during melting are given