Stampaggio a compressione di capsule in PLA: influenza dei parametri di processo su proprietà chimico-fisiche e performance

Coffee capsules are single-dose devices that have the purpose of protecting coffee from oxygen and moisture and allowing the coffee to be dispensed in a coffee machine. The capsules can be made of aluminum or polyolefin or bio-based plastic material. Several Nespresso compatible capsules based on PLA (biodegradable and compostable whose monomer is obtained from renewable sources) were produced using the continuous compression molding technique to reduce the operating temperature (necessary to reduce the degradation of PLA). The formulation of the capsules includes PLA (1: Ingeo™ biopolymer 3260HP; or 2: Ingeo™ biopolymer 3100HP), “AM” as mineral additive to increase the thermal and stiffness resistance as well as the oxygen impermeability and an organic additive “AO” to allow the separation of the capsules from the mold. Some process parameters were changed during the internship, like capsule geometry, composition, mold temperature (Tcav./Tpun.), cycle time (tc) and storage conditions to check theirs effects on the performance in the dispensing machine evaluated using a proposed Capsule Index. Indeed, in principle these parameters can affect the degree of crystallinity and the barrier properties (evaluated with MOCON) and it was necessary to find out which set of parameters would have led to best performances. The only parameter that had effects on the barrier properties was found to be AM because an increase in its concentration led to a decrease in the OTR value. Capsule of group 15 was found to be the best performing capsule, due to the optimal parameters chosen, and was characterized by DSC and DMA tests (temperature ramp and stress/strain curves). We also looked for an alternative method to the DSC for determining the degree of crystallinity (due to “long analysis time”). Correlation tests between FT-IR ATR, Mohr Balance and DSC showed that it would be more useful continuing with the DSC method.