Cocontinuous polymer blends are microstructured polymers created by melt mixing that consist of two or more immiscible polymers that each form interpenetrated and continuous phases. Cocontinuous blends of polyethylene (PE) and polylactic acid (PLA) were prepared using different long-chain branching architectures to vary extensional rheological properties while keeping shear rheological properties nearly identical. Porous PE was then made by extracting the continuous PLA phase with chloroform. The porosity can be tuned by the volume fraction of PLA extracted from the blend, and the range of achievable porosity was controlled by the blend compositions that resulted in cocontinuity. For blends of linear polymers, the range of PE porosity was narrow (39-59 vol%), while in moderately branched blending systems, the range of PE porosity was significantly widened (25-76 vol%). This broadening effect was explained by the strain hardening behavior of the branched polymers. The pore size can be controlled by quiescent annealing and reactive compatibilization. Pore size was characterized using laser scanning confocal microscope and 3-D reconstruction of the porous structure. The pore size of non-compatibilized PE/PLA blends was on the order of 5 �m, and quiescent annealing could increase this up to hundreds of microns over time. When maleic anhydride grafted PE (PE-g-MA) was blended with PLA, the pore size decreased to 1.2 �m as a result of reactive compatibilization, and the pore size did not significantly increase during annealing. This is presumably from a reaction between the maleic anhydride groups on the PE-g-MA chains and the hydroxyl end group of PLA, which forms graft copolymers and reduces interfacial tension.

Controlling pore structure of macroporous polyethylene derived from cocontinuous polyethylene/polylactic acid blends

248th National Meeting (2014)

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