Effect of SEBS and OBC on the Impact Strength of Recycled Polypropylene/Talc Composites

In this paper, we report a study on the use of a linear triblock copolymer based on styrene and ethylene/butylene (SEBS) and a polypropylene (PP)-based olefin block copolymer (OBC) for improving the impact strength of a recycled polypropylene (PP) from packaging waste. Talc was used as a reinforcing filler in order to prepare a material suitable for being used in the automotive sector. The composite mixtures were prepared by melt extrusion, and the samples were manufactured by injection molding. Impact strength was evaluated by Izod tests, and a morphological study of the produced fractures was performed. As a result, a composite with substantially improved impact properties was prepared, with a two-fold increase of the impact strength in the case of unnotched specimens, while only a limited positive effect was produced on notched specimens. Since talc-filled PP is a typical material used in the automotive sector, the obtained results demonstrate that post-consumer PP coming from the municipal waste collection of plastic packaging can be successfully used in car components with no compromise in terms of mechanical requirements.

Nanofiller Dispersion, Morphology, Mechanical Behavior, and Electrical Properties of Nanostructured Styrene-Butadiene-Based Triblock Copolymer/CNT Composites

A nanostructured linear triblock copolymer based on styrene and butadiene with lamellar morphology is filled with multiwalled carbon nanotubes (MWCNTs) of up to 1 wt% by melt compounding. This study deals with the dispersability of the MWCNTs within the nanostructured matrix and its consequent impact on block copolymer (BCP) morphology, deformation behavior, and the electrical conductivity of composites. By adjusting the processing parameters during melt mixing, the dispersion of the MWCNTs within the BCP matrix are optimized. In this study, the morphology and glass transition temperatures (Tg) of the hard and soft phase are not significantly influenced by the incorporation of MWCNTs. However, processing-induced orientation effects of the BCP structure are reduced by the addition of MWCNT accompanied by a decrease in lamella size. The stress-strain behavior of the triblock copolymer/MWCNT composites indicate higher Young’s modulus and pronounced yield point while retaining high ductility (strain at break ~ 400%). At a MWCNT content of 1 wt%, the nanocomposites are electrically conductive, exhibiting a volume resistivity below 3 × 103 Ω·cm. Accordingly, the study offers approaches for the development of mechanically flexible functional materials while maintaining a remarkable structural property profile.

Mechanical and thermal properties of PP/PBT blends compatibilized with triblock thermoplastic elastomer

A linear triblock copolymer, poly(styrene-b-etylene/butylene-b-styrene)(SEBS) thermoplastic elastomer (TPE) grafted with maleic anhydride was used for compatibilization of PP/PBT blends. PP/PBT blends of different mass ratios 60/40, 50/50, 40/60 were mixed with 2.5, 5.0 and 7.5 wt.% of SEBS copolymer in a twin screw extruder. Differential scanning calorimetry and dynamic mechanical analysis were performed to define the phase structure of PP/PBT blends. TPE with a rubbery mid-block shifted the glass transition of PP/PBT blend towards lower temperatures, and significant decrease the crystallization temperature of a crystalline phase of PP component was observed. The influence of the amount of compatibilizer and the blend composition on the mechanical properties (tensile and flexural strengths, toughness and moduli) was determined. Addition of 5 wt.% of a triblock TPE led to a three-fold increase of PP/PBT toughness. A significant increase of impact properties was observed for all materials compatibilized with the highest amount of SEBS copolymer.

Synthesis and Characterization of Amphiphilic Multiwalled Carbon Nanotubes Based on Linear Triblock Copolymer

Amphiphilic multiwalled carbon nanotubes PMAA-g-MWCNT-g-PSt were prepared by grafting linear triblock copolymer PtBMA100-b-PGMA19-b-PSt101 onto the carboxyl multiwalled carbon nanotubes surface with an oxirane cleavage reaction. The ratio of intensity between D band and G band and the shifting of these bands in Raman spectroscopy showed good agreement with fourier transform infrared spectroscopy especially the appearance of the characteristic group of benzene ring at 673 cm-1 for PMAA-g-MWCNT-g-PSt. Thermogravimetric analysis showed that the contents of polymer grafted on the surface of carboxyl multiwalled carbon nanotubes were 36 % and 55 % for PMAA-g-MWCNT-g-PSt and PtBMA-g-MWCNTs-g-PDMAEMA, respectively. The introduction of the cinnamic group into PtBMA100-b-PGMA19-b-PSt101 induced the activation energy of PMAA-g-MWCNT-g-PSt much higher than that of PtBMA-g-MWCNTs-g-PDMAEMA after 238 oC during their thermal decompositions.

Synthesis and Characterization of Novel Multiarm-Star Polyisobutylene-Polystyrene Thermoplastic Elastomers

New multiarm-star block copolymers of polyisobutylene (PIB) and polystyrene (PS) were synthesized by living carbocationic polymerization using a novel hexafunctional initiator in conjunction with TiCl4. The new initiator, hexaepoxy squalane (HES) was prepared by a simple epoxidation (RT, 5 min) of commercial squalene. The homopolymerization of isobutylene (IB) initiated by HES is living, demonstrated by linear ln([M]o/[M]t) vs time and Mn vs conversion plots and relatively narrow molecular weight distributions (MWD=1.2). The branched nature of the PIBs was proven directly by diphenyl ethylene end capping, and indirectly by kinetic analysis and size exclusion chromatography (SEC). Subsequent blocking of PIB with PS was demonstrated by triple detection SEC: refractive index (RI), multiangle laser light scatering (MALLS) and ultraviolet (UV). A new multiarm-star and a conventionally prepared linear triblock copolymer sample were subjected to supercritical fluid (SCF) fractionation and the fractions were analyzed by SEC and 1H NMR. Analysis of the fractions indicated living conditions for the PS blocking in the star-block. Interestingly, the linear triblock showed bimodal distribution in terms of PS content and molecular weight.