Gas permeability modification of polyolefin films induced by d-limonene swelling

Gas permeability (H2, O2, N2, CO2, C2H4, and C3H6) and permselectivity against nitrogen in the polyolefin films (LDPE, HDPE, Metallocene PE, EVA5, PP, and PMP) strongly influenced by the swelling of d-limonene (DL) absorption, were studied. All the gas permeability obtained in these films were commonly increased by increasing the amount of d-limonene absorbed in the films (CDL: cm3 STP/cm3), which indicated an especially drastic enhancement of CO2 permeability in low density polyethylene (LDPE) from 15.2 to 67.8 Barrer (1 Barrer=(×10−10) cm3 STP cm/cm2 cmHg s) at CDL=2.3. Based on experimental evidences that gas permeability was proportionally increased with increasing CDL, whereas the film crystallinity of LDPE evaluated with method of a wide-angle XRD decreased, it was concluded that the gas permeability enhancement was caused by the film crystallinity decay due to d-limonene sorption. On the permselectivity against nitrogen obtained for all the gases, CO2, C3H6 and C2H4 were characterized by a positive enhancement, and H2 and O2 a slight negative enhancement. The effect of d-limonene absorption into the polyolefin films on the CO2 permeation was interestingly characterized by a simultaneous enhancement of permeability (P) and CO2/N2 permselectivity (αCO2), typically indicating from P=15.2 to 67.8 Barrer and from αCO2=19 to 26.1 for LDPE.