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To meet the expectations of European consumers, who prioritize agro-environmental factors and local resources, the substitution of fats (palm, coconut, shea) and achieving a balanced fatty acid profile in spreadable fats are gaining more attention. The crystallization at 4 °C of a lipid blend composed of rapeseed oil, anhydrous dairy fats, and emulsifiers was studied using a multi-scale approach (DSC and X-ray diffraction techniques) to understand the emergence of polymorphic structures. Although the addition of PUFA from rapeseed oil reduces the atherogenicity and thrombogenicity indices in the blend, controlling the cooling kinetics influences the shapes (needles and spherulites) and sizes of the crystalline structures (small crystals form at a cooling rate of 1 °C min−1, while larger crystals form at higher rates of 5 and 10 °C min−1). The crystallization behavior revealed differences in polymorphic forms at 4 °C in the blend, with a transition to different forms occurring more rapidly compared to dairy fat (stop-and-return method). The study shows crystalline coexistence (α, β′, and β) in a 2L lamellar structure, with the β′ form being predominant. This structure is ideal for formulating a spreadable product, offering good spreadability (SFC < 32% at 10 °C), mouthfeel, and nutritional benefits compared to butter. [ABSTRACT FROM AUTHOR]

This study investigates the thermal behavior of polyethylene 2,5‐furandicarboxylate using Raman spectroscopy. The study finds that multiple changes in the Raman spectrum at two different heating rates of 1 and 0.5 K/min provide different information about the thermal behavior of the sample. The study also shows that the derivative of the half‐width of the band at 1737 cm−1, which characterizes the stretching of the C=O double bond of the ester group, allows us to trace back to the DSC thermogram. The crystallinity was followed with quite a good precision and using two different spectral zones around 1029 and 1737 cm−1. The calculated crystallinity rate could be compared with the crystallinity rates obtained by integrating the total heat flow by DSC and that obtained by wide angle X‐ray scattering (WAXS). As a result, this study also allows us to understand the conformational changes that take place during heating, and especially those responsible for crystallization, which is the great advantage of Raman spectroscopy compared with other standard methods. [ABSTRACT FROM AUTHOR]

Tracking the Raman scattering bands of polyethylene terephthalate (PET) during thermal heating has allowed to establish criteria for monitoring the crystallinity ratio within a few seconds. The existing criteria, based on Raman bands at 998 cm−1 and at 1096 cm−1, present certain disparities from the crystallinity ratio given by the total heat flow in differential scanning calorimetry (DSC). Based on the evolution of the Raman bands, a newfound method allowing the effective calculation of crystallinity ratio is proposed. For the same, the band at 1727 cm−1, which is characteristic of the C=O carbonyl bonds of the ester group of PET, is used. The new criterion, designated r1727,2, was compared and validated by DSC and XRD. This novel approach also provides access to information on the various conformational states of the bonds under study, that is, their proportions and positions with respect to the plane of the macromolecule aromatic rings. Evidently, this allows to reveal the characteristic thermal behavior of the PET microstructure such as the glass transition, crystallization, and melting. This method can be useful for the close detection, quantification, understanding, and tracing of the micromechanisms involved at the macromolecular conformations scale during thermal cycles. [ABSTRACT FROM AUTHOR]

Graphene materials exhibit extraordinary properties, but are difficult to produce. The present work describes the possibility of using a plasma process to exfoliate and functionalize graphite flakes. An impulse plasma phase is generated at a liquid surface to produce chemical species and shock waves in order to modify the reactive liquid as well as the graphite flakes. With this process, industrial graphite was treated. 20% thickness diminution was observed, and the formation of a random turbostratic structure. The exfoliation occurs with small amount of functionalization of the surface. Even after treatment, the graphite flakes present a low defect density compared with other treated graphite obtained by more conventional chemical treatments. This process is a new way to exfoliate graphite and to produce functionalized graphenic materials. [ABSTRACT FROM AUTHOR]

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]

Weathering of LDPE films was performed in a sub-Saharan facility in Laghouat, Algeria. Ageing led to a rapid change of the physicochemical properties resulting from the alteration of the material's microstructure. XRD revealed the progressive increase of the crystallinity ratio and the thickness of the crystalline lamellae as well. SEM revealed the presence of white particles, which look like crystalline phase emerging from the surface of the film. The oxidation and crystallinity varied according to a concentration gradient across the thickness. The impact of the microstructural changes on the mechanical properties was highlighted based on the essential work of fracture (EWF) method. There was a progressive decrease of the total energy of fracture and a lowering of the net stress (σnet) and the (βwp) term. Nevertheless, this loss of the mechanical properties was characterized by a rapid transition from a ductile mode of failure to a very brittle mode. [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]

ABSTRACT EVA copolymer foils are widely used as encapsulants for photovoltaic (PV) cells in PV modules. These foils need to be crosslinked during module manufacturing, to enhance their properties. Accurate and reliable methods for the determination of their crosslinking degree are thus very important. In this work, two semi-empirical calorimetric methods are considered and compared to a scientifically sound rheological method used as a reference. The main purpose of this work is to reveal the chemical and physical fundamentals on which the two calorimetric methods are based, to allow for a scientific understanding of their advantages, and limitations. For one of these calorimetric methods, the so-called 'Melt-Freeze' method, we have sought for a deeper understanding of the underlying crystallization physics through the use of successive self-nucleation and annealing experiments, which give access to the crystallite size distribution of EVA, and to the influence of crosslinking upon it. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 866-876 [ABSTRACT FROM AUTHOR]

Background: Arterial bypass surgery of small-caliber vessels using synthetic vascular prostheses remains inefficient as they promote thrombosis probably due to a low or non-functionalization of their internal surface(1). As a potential therapeutic alternative, we have developed a human cellularized TEVG (tissue-engineered vascular graft) whose components are all derived from the umbilical cord. Methods: Decellularized umbilical arteries were coated at their luminal surface with an extracellular matrix extracted from Wharton's jelly and then cellularized by mesenchymal stromal cells derived also from WJ. The luminal coating and cellularization were optimized by an innovative "inside-out" method allowing easy access to the luminal surface. TEVG hemocompatibility (Thrombin Generation Assay) and mechanical properties (burst pressure test, stress rupture test, dynamic mechanical analysis) were evaluated. Preliminary in vivo implantations were conducted in pigs for coronary or femoral arterial bypass. Results: The "inside-out" method, which did not impact mechanical properties of the TEVG, allowed a homogeneous cellularization of arteries luminal surface confirming its adaptability to a vascular context. Hemocompatibility assays showed that the TEVG behaves as a native blood vessel due to full cell covering of the luminal surface. The TEVG was successfully implanted in a coronary artery bypass model (n = 1), and was well tolerated, colonized and remain patent for 2 weeks post-implantation in a femoral replacement model (n = 1). Conclusion: Our TEVG is an allogeneic therapeutic solution offering a ready-to-use graft that may supply a tissue bank and which can be grafted by minimally invasive robotic techniques avoiding an invasive surgery, having beneficial societal and economic impacts. [ABSTRACT FROM AUTHOR]

The possibilities of applications of vibrational spectroscopy techniques (Raman spectroscopy) in the analysis and characterization of polymers are more and more used and accurate. In this paper, our purpose is to characterize Low Density Poly(Ethylene) (LDPE) grades by Raman spectroscopy and in particular with CH2 Raman vibration modes. With temperature measurements, we determine different amorphous and crystalline Raman assignments. From these results and on the basis of the evolution of CH2 bending Raman vibration modes, we develop a phenomenological model in correlation with Differential Scanning Calorimetry and in particular with crystalline lamella thickness determination. [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.

The structure of self-reinforced composites (SRCs) based on ultra-high molecular weight polyethylene (UHMWPE) was studied by means of Wide-Angle X-ray Scattering (WAXS), X-ray tomography, Raman spectroscopy, Scanning Electron Microscopy (SEM) and in situ tensile testing in combination with advanced processing tools to determine the correlation between the processing conditions, on one hand, and the molecular structure and mechanical properties, on the other. SRCs were fabricated by hot compaction of UHMWPE fibers at different pressure and temperature combinations without addition of polymer matrix or softener. It was found by WAXS that higher compaction temperatures led to more extensive melting of fibers with the corresponding reduction of the Herman's factor reflecting the degree of molecular orientation, while the increase of hot compaction pressure suppressed the melting of fibers within SRCs at a given temperature. X-ray tomography proved the absence of porosity while polarized light Raman spectroscopy measurements for both longitudinal and perpendicular fiber orientations showed qualitatively the anisotropy of SRC samples. SEM revealed that the matrix was formed by interlayers of molten polymer entrapped between fibers in SRCs. Moreover, in situ tensile tests demonstrated the increase of Young's modulus and tensile strength with increasing temperature. [ABSTRACT FROM AUTHOR]