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Semi-crystalline polylactide (PLA)/polyolefin multi-component blends were used as precursors for the generation of a new class of micro-cellular polymers. Either a polypropylene-based elastomer (PBE) or polypropylene (PP) homopolymer were utilized as dispersed phases at the 10 wt% level. An epoxy-functionalized terpolymer (PEGMMA) was introduced (1 wt%) as a reactive compatibilizer to reduce the dispersed phase droplet size and provide sufficient adhesion between the matrix and dispersed phase. In addition, a polyalkylene glycol liquid (PAG) was added to the blend (4 wt%) to serve as a PLA plasticizer and interfacial modifier. The multicomponent blends exhibited significant increases in strain at break as compared to neat PLA and were subjected to a range of uniaxial strains (10–90%) at room temperature. These cold drawn materials exhibited nearly constant cross-sectional area and fine micro-cellular structures, as revealed by scanning electron microscopy. Distinct different voiding mechanisms observed for the PBE- and PP-containing blends were ascribed to the differences in the dispersed phase elastic moduli and deformability. The material density of cold drawn blends was reduced by up to 34% when compared to the precursor blends without a noticeable change in cross-sectional area. The novel low-density microcellular PLA blends demonstrated outstanding mechanical properties such as high strength, high modulus, substantial ductility, and a 14-fold increase in impact resistance as compared to PLA homopolymer.
Bibliographical noteFunding Information:
The authors would like to acknowledge the Kimberly-Clark Corporation for funding support, providing polymer blends, and assistance in the notched Charpy impact tests and modelling work. We also acknowledge the Center for Sustainable Polymers at the University of Minnesota, a National Science Foundation supported Center for Chemical Innovation ( CHE-1413862 ). S.A.S acknowledges the NSF GRFP for funding. Parts of this work were carried out in the Characterization Facility, University of Minnesota, a member of the NSF-funded Materials Research Facilities Network ( www.mrfn.org ) via the MRSEC program.
- Lightweight polymer
- Polymer blend
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 3