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In‐situ Raman spectroscopy analysis to mechanical tests were performed to investigate the deformation micromechanisms of an isotactic polypropylene‐grafted maleic anhydride (PP‐g‐MAH) depending on the crosslinking degree provided by functional polyether amine molecules. The switch from brittle to highly ductile mechanical behaviours was focused in terms of microstructure modifications in real time during stretching. From the Raman spectral analysis, crystallinity index and macromolecular chains orientation factors for both crystalline and amorphous phases were determined. A new orientation factor relative to the polyether segments was proposed. The results shown allow a more complete understanding of the proper micromechanisms of deformation involved in each phase and their interaction between one another. These results also highlight the impact of the crosslinking reaction on the material resilience improvement. [ABSTRACT FROM AUTHOR]

An isotactic polypropylene grafted by 1 wt% of maleic anhydride (iPP-g-MAH) was chemically modified to provide it with new functional abilities and improved mechanical properties. The specific additive considered in this work is a derivative of bis(aminoalkyl)-calix[4]arene. Not only this molecule serves as a cross-linking agent, but it offers grafting sites for metallic ions that confer electrolytic conductivity to the initially insulating polyolefin. Materials were synthesized by reactive extrusion, and subsequently manufactured as plates by injection molding. The three-dimensional macromolecular architecture was optimized by adjusting the NH2:MAH molar ratio in a range from 0.5:1 to 1:1. Fourier transform infrared spectroscopy revealed the amine/ anhydride chemical reactions, while gel content measurements were used to determine the degree of cross-linking. The crystalline microstructure of the different materials was characterized by two complementary methods: (a) overall crystallinity by differential scanning calorimetry; (b) lamellar thickness by thermal fractionation using the self-successive auto-nucleation procedure. Only a small decrease of the crystalline lamellae is observed. The mechanical properties were determined by a video-controlled tensile testing method and by Brillouin spectroscopy. A transition from brittle to ductile behavior was observed for increasing cross-links density. Scanning electron microscopy on fracture surfaces showed that ductile fracture was favored by the development of fibrils. [ABSTRACT FROM AUTHOR]

Hybrid composites of polypropylene (PP)/sodium montmorillonite (Na-MMT)/short polyamide fibers (PAfs) were prepared by reactive melt mixing in a Brabender plastograph. To enhance filler interactions within polypropylene, a functionalizing agent (FA) and a coupling agent were added to the Na-MMT and PAfs, respectively. An organic peroxide/sulfur mixture and tetramethylthiuram disulfide as an activator for sulfur were used to functionalize Na-MMT; on the other hand, the PAfs surface was treated using stearic acid. The aim of this study is to investigate how the morphology and the structural properties of 3, 5, and 7 wt% recycled functionalized sodium montmorillonite nanocomposites (f-Na-MMT) are affected by the presence of 5 wt% treated short polyamide fibers (t-PAfs). According to the obtained results, 5 wt% recycled f-Na-MMT/5 wt% t-PAfs/PP hybrid composite showed Na-MMT layers exfoliation. The nucleating effect of f-Na-MMT and t-PAfs was indicated by the differential scanning calorimetry (DSC) measurements. Morphological analysis of the hybrid composites was performed using scanning electron microscope (SEM) and optical polarized microscopy (POM), showing a good dispersion of the fibers with an interesting interfacial adhesion between the PP and t-PAfs phases. Hybrid composites of PP/f-Na-MMT/t-PAfs are considered for automotive industry. [ABSTRACT FROM AUTHOR]

The article proposes an experimental method for quantifying the molecular orientation of the crystalline phase of isotactic polypropylene from polarized Raman spectroscopy measurements. Raman and Wide Angle X-ray Scattering (WAXS) results obtained on postmortem test samples were compared. The method's application to follow the molecular orientation in situ during a tensile test is described. A quantitative agreement between WAXS and Raman measurements was discovered.

Abstract Ductile functionalized polypropylene is of great interest in multi-layer composites development. A capped-end triblock polyether diamine (H 2 N-PO 2 -TMO 9 -PO 3 -NH 2) was used as a linker of two different maleated isotactic polypropylenes (iPP -g- MAH, at 1 and 3 wt%) by twin-screw reactive extrusion. The molecular architecture, the semi-crystalline microstructure and the mechanical properties of the resulting polymers were analysed as a function of the molar ratio of NH 2 :MAH (0:1, 0.33:1, 0.5:1, 0.66:1, 1:1, 1.5:1, 2:1). At the molecular scale, the chemically modified polymers were characterized by FTIR and by the determination of gel content following the ASTM D2765-84 standard method. Differential Scanning Calorimetry, Wide Angle X-rays Scattering and Self Successive Auto-nucleation techniques showed the impact of the crosslinking: a decrease of the melting temperature as compared with the unmodified iPP -g- MAH polymer, as well as a decrease of the crystallinity ratio for the iPP -g- MAH at 3 wt% of MAH. Interestingly, Dynamic Mechanical Analysis and video-controlled uniaxial tensile tests showed that the polymers obtained in stoichiometric NH 2 :MAH molar ratio exhibit the best mechanical properties enlightened by a switch from brittle to ductile mechanical behaviour with few differences between the two iPP -g- MAH. Graphical abstract A slight crosslinking enables maleated isotactic polypropylenes to switch from brittle to ductile mechanical behavior with higher resilience than the most conventional one. Image 1 Highlights • A capped-end triblock polyetherdiamine is used as a linker of different iPP- g -MAH by twin-screw reactive extrusion. • The three-dimensional networks are characterized by FTIR and by the determination of gel content. • The semi-crystalline microstructure is thermally described applying the Self-Successive Auto nucleation technique. • A switch from brittle to ductile mechanical properties is observed studying the intrinsic true mechanical behaviours. [ABSTRACT FROM AUTHOR]