Crosslinking and stabilization of high fractional free volume polymers for gas separation

Crosslinkable poly(4-methyl-2-pentyne) (PMP) membranes were cast from carbon tetrachloride solutions containing PMP and either 4,4′-diazidobenzophenone or 4,4′-(hexafluoroisopropylidene)diphenyl azide. The composite membranes were transparent and homogeneous and were crosslinked by UV irradiation at room temperature or thermal treatment at 180 °C. Low levels of the bis(aryl azide) (1–4.5 wt%) were effective in rendering the membranes insoluble in cyclohexane and carbon tetrachloride, both are good solvents for PMP, thus PMP can easily be converted to mechanically stable membranes with permeabilities and selectivities comparable or higher than those of the well-known poly(dimethylsiloxane) (PDMS). The permeabilities of O₂, N₂, H₂, CH₄ and CO₂ were measured. Compared to pure PMP, the crosslinked membranes containing bis(aryl azide) had lower permeabilities and higher selectivities, consistent with a reduction in free volume.     

Valorization of regenerated LDPE by blending with EPDM in the presence of peroxide

The present work aims to the valorization of regenerated low density polyethylene (LDPE) by blending with small quantities of ethylene-propylene-diene monomer (EPDM). Three types of regenerated LDPE (rLDPE) from different waste sources (greenhouses, milk pouches,...) were characterized in terms of physico-chemical (density, melt flow index, water absorption, melting temperature and structure by Fourier transform infrared (FTIR) spectroscopy) and mechanical properties (tensile properties and hardness). The optimization of the peroxide content required for the crosslinking of the LDPE/EPDM blends was due by measuring torque and tensile strength. Once the peroxide content was optimized, different blends were obtained by varying the EPDM content. Then they were characterized physically (density, water absorption) and mechanically (tensile properties and hardness). Finally, the blends behavior under the conjugated effect of heat and water was determined at 70 °C for 7 days. The obtained results showed that this kind of blending has contributed in improving the performance of regenerated LDPE.