Polylactide (PLA) was melt blended with either polypropylene (PP) or a polypropylene based elastomer (PBE, Vistamaxx) in an effort to improve its mechanical properties. An ethylene−glycidyl methacrylate−methyl acrylate terpolymer (PEGMMA, Lotader) was utilized as compatibilizer through coupling to the end groups of PLA. Graft copolymers formed enhanced the adhesion between PLA and polyolefin phases and lowered the interfacial tension. The morphological, mechanical, and rheological properties of the PLA/polyolefin compatibilized blends were investigated, and the blends exhibited substantial improvement in elongation at break and tensile toughness as compared to the corresponding binary blends. The remarkable efficacy of PEGMMA as a reactive compatibilizing agent allows the bridging of two immiscible but important classes of thermoplastics, polylactide and polypropylene, and the production of ductile PLA/PP blend materials.

Low molar mass (3−17 kg/mol) amino-telechelic polyethylene (ATPE) was used to reactively compatibilize poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE) via ester aminolysis of PET. A tertbutyloxycarbonyl (Boc)-protected polyethylene precursor was thermolytically deprotected during the melt-blending process to render the reactive amine termini. Spectroscopic analysis of a model reaction confirmed the presence of amide functionality in the resultant material. Through blending studies, we found that low loadings of ATPE (0.5 wt %) significantly reduced the volume of the dispersed HDPE phase particles by a factor of 8 when compared to a binary PET/HDPE blend as assessed by scanning electron microscopy (SEM). Mechanical analysis of the ATPE-compatibilized blends showed a 12fold increase in the elongation at break over the unmodified PET/HDPE blend. Ultimately, the results here offer a new approach to reactively compatibilize and toughen PET/HDPE blends and open the door for other uses of amino-telechelic polyethylene.

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.

Micromechanical deformation of polyethylene terephthalate (PET)/ethylene-stat-methyl acrylate copolymer [p­(E-s-MA)] blends was investigated for various MA contents and molar masses of p­(E-s-MA). The copolymers were synthesized by ring-opening metathesis polymerization and subsequent hydrogenation. Varying the MA content and molar mass of the copolymer alters the interfacial adhesion between the PET and the copolymer and the mechanical properties of the copolymer significantly. Transmission electron microscopy images of the blends obtained after tensile deformation reveal that the composition and the molar mass of the copolymer determine whether debonding, cavitation, both, or neither occurs during stretching. The extent of void formation associated with tensile testing was characterized by density measurements.