Preparation of Well-Compatibilized PP/PC Blends and Foams Thereof

The performance of polypropylene-poly(ethylene brassylate) block and graft copolymers and a polypropylene-polycaprolactone graft copolymer as compatibilizers for polypropylene-rich polypropylene/bisphenol A polycarbonate (PP/PC, 80/20 wt/wt) blends was elucidated. The copolymers were synthesized either by metal-catalyzed ring-opening polymerization or transesterification of a presynthesized polyester, initiated by hydroxyl-functionalized PPs, which themselves were obtained by catalytic routes or reactive extrusion, respectively. Spectroscopic fingerprints of the copolymers from liquid-state nuclear magnetic resonance (NMR) in combination with scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA), and rheology analyses of the blends indicated that the compatibilizers spontaneously organize at the interface of the two immiscible polymers leading to the formation of uniform, stable, nanophase morphologies. The effect of the compatibilizers on the performance of the PP/PC blends was evaluated, and well-compatibilized PP/PC blends showed improved melt strength and strain hardening when compared to pure PP. This was verified by the successful foam extrusion using isobutane as a blowing agent of well-compatibilized PP/PC blends to low-density PP-based foams, for which normally long-chain branched PP is required

iPP/HDPE blends compatibilized by a polyester:An unconventional concept to valuable products

Polyolefins are the most widely used plastics accounting for a large fraction of the polymer waste stream. Although reusing polyolefins seems to be a logical choice, their recycling level remains disappointingly low. This is mainly due to the lack of large-scale availability of efficient and inexpensive compatibilizers for mixed polyolefin waste, typically consisting of high-density polyethylene (HDPE) and isotactic polypropylene (iPP) that, despite their similar chemical hydrocarbon structure, are immiscible. Here, we describe an unconventional approach of using polypentadecalactone, a straightforward and simple-to-produce aliphatic polyester, as a compatibilizer for iPP/HDPE blends, especially the brittle iPP-rich ones. The unexpectedly effective compatibilizer transforms brittle iPP/HDPE blends into unexpectedly tough materials that even outperform the reference HDPE and iPP materials. This simple approach creates opportunities for upcycling polymer waste into valuable products.</p

Unprecedented Adhesive Performance of Propylene-Based Hydroxyl-Functionalized Terpolymers

The synthesis of hydroxyl-functionalized propylene-based terpolymers and their performance as hot melt adhesives were investigated. The products comprise uniformly distributed butyl and 4-hydroxyl-butyl branches along the polypropylene backbone. Despite the low hydroxyl-functionality level of ≤ 0.5 mol %, hydroxyl-functionalized terpolymers show formidable adhesion to aluminum and steel, providing an adhesive strength exceeding 16 MPa, whereas the nonfunctionalized congeners hardly adhere to these metals. As evidenced by rheological measurements, the functional groups form dynamic crosslinks based on hydrogen bonding and electrostatic interactions with aluminum oxide hydroxide residues, remaining in the product after polymerization. At the industrial application temperature of 180 °C, nondeashed and deashed samples of polymers having 0.1 or 0.5 mol % incorporated 5-hexen-1-ol gave, upon cooling to room temperature, comparable adhesive strengths. Deashing and increasing the functionality level lead to a significant improvement of the adhesion strength at a lower application temperature (130 °C), allowing application of the hydroxyl-functionalized propylene-based terpolymers as high-strength hot melt adhesives for combinations of polypropylene and metals