Influence of cooling conditions during 3D printing on the switching temperature of a TPU with SME

Abstract

Shape memory polymers (SMP) are materials with a special structure, designed to react to a certain stimulus. Using such SMPs with 3D printing technology opens up further fields of application thus providing for the so-called 4D printing. After such a printing process it is mandatory for the SMP to still be able to form a crystalline structure, maintaining its own shape memory effects (SME). The crystalline portion or the hard section of polymers is strongly influenced by the cooling rate during the printing process. In order to evaluate the influence of the cooling on the formation of the segments, thermal measurements using Differential Scanning Calorimetry (DSC) were carried out. The test shows that the cold crystallization was evident in each case in the first heating run, but the cooling rate in the FFF (Fused Filament Fabrication) technology could not be reduced to such a level that the switching temperature changed. In order to have an influence on the melt peak, the cooling rate must be increased further. This was demonstrated in the 2nd heating run of the DSC measurements.