The effect of compatibilizer SEBS on the mechanical, morphological and thermal properties of the polystyrene/poly (styrene-co-acrylonitrile) copolymer blends

In this study, the effect of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) as compatibilizer on polystyrene/poly(styrene-co-acrylonitrile) copolymer (PS/SAN) blends was investigated. For this purpose, blends of various compositions with different content of compatibilizer were prepared by melt blending using a co-rotating twin-screw extruder, and their physical properties, namely the mechanical properties including tensile and impact tests, thermal properties by differential scanning calorimetric (DSC) and thermal stability by thermogravimetric analysis (TGA), studied. Morphological observations using scanning electron microscope (SEM) and viscoelastic properties using dynamic mechanical thermal analysis (DMTA) were also carried out. The results revealed that the mechanical properties were highly improved due to the addition of SEBS which allowed the increase of the blend ductility by enhancing the elongation at break and impact strength. SEM micrographs revealed that the droplet-matrix microstructure was notably refined and the droplets size decreased from 6.7 μm to 2.37 μm in the presence of the compatibilizer. DSC results showed a single glass transition temperature (Tg) for the composition PS/SAN (30/70) compatibilized with 5 and 10% wt of SEBS which confirms the compatibilization of the blend for these compositions

Effect of a thermoplastic elastomer compatibilizer (sebs-g-mah) on the properties of PP/PET blends

10 pags., 9 figs., 2 tabs.Polyethylene terephthalate (PET) and polypropylene (PP) are widely used and frequently encountered in domestic and industrial plastics, especially in the soft drink bottles. In the present work, different compositions of PP/PET blends were prepared and compatibilized by various contents of SEBS-g-MAH. The compatibilizing efficiency was examined using macro- (tensile and impact strength) and micro-mechanical testing (microhardness measurement), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and melt flow index (MFI) determinations. The results show that the addition of SEBS-g-MAH improves the processability and the toughness of these blends. The changes in the melting enthalpies (ΔH) of the PP and PET components and the decrease of MFI values in the compatibilized blends indicated enhanced interactions between the discrete PET and PP phases induced by the functional compatibilizer. The DSC crystallinity of each component depended on the blend composition, and was slightly influenced by the presence of the compatibilizer. In the samples subjected to compression molding, the WAXS crystallinity of PP component slightly decreased in the presence of increasing amounts of compatibilizer.One of the authors (MEC) wishes to thank the Spanish Ministry of Science and Innovation MICINN for the financial support of this investigation (Grant MAT2009-07789).Peer Reviewe

Effect of thermal treatment on the mechanical and viscoelastic response of polypropylenes incorporating a β nucleating agent

The influence of two thermal treatments on the structure, morphology, and ultimate properties exhibited by isotactic polypropylene (iPP), synthesized by conventional Ziegler–Natta iPP (Z-iPP) or metallocene iPP (m-iPP) catalysts, has been investigated in the present work. Novelty of this research consisted in the incorporation of a β nucleating agent in two different contents to the m-iPP. Results attained are compared with those found in the Z-iPP and important differences are observed. Differential scanning calorimetry and X-ray diffraction experiments revealed that coexistence of different crystalline lattices took place depending on the type of iPP: β and α forms were found in the β nucleated Z-iPP specimens, whereas α, β, and γ polymorphs could be developed in the m-iPP with nucleating agent. On the other hand, the iPP glass transition temperature (T) did not exhibit a significant change because of the addition of β nucleant, as deduced from Dynamic Mechanical Thermal Analysis (DMTA) analysis. Moreover, the size and shape of the iPP spherulites was totally changed by the presence of the β agent. This nucleant promoted the formation of smaller spherulites in a greater amount, as demonstrated by optical microscopy. Concerning the mechanical parameters, microhardness, MH, and Young modulus, E, values were in the fast crystallized samples lower than those presented by their slowly cooled counterparts. A good balance in properties was seen for the slowly crystallized m-iPP that incorporated a 5 wt% content in β nucleating agent, this fact being ascribed to the coexistence of the three α, β, and γ polymorphs

Composites of a polypropylene random copolymer and date stone flour: Crystalline details and mechanical response

Several composites were prepared based on a polypropylene random copolymer (PPR) and different amounts of date stone flour (DSF). This cellulosic fiber was silanized beforehand in order to reduce its hydrophilicity and improve the interfacial adhesion with the polymer. Other composites were also obtained, including a sorbitol derivative as an effective nucleant. Films made from these composites were prepared using two different thermal treatments, involving slow crystallization and rapid cooling from the melt. Scanning electron microscopy was used to evaluate the morphological features and the DSF particle dispersion within the PPR matrix. X‐ray diffraction experiments and differential scanning calorimetry tests were employed to assess the crystalline characteristics and for the phase transitions, paying especial attention to the effects of the DSF and nucleating agent on PPR crystallization. An important nucleation ability was found for DSF, and evidently for the sorbitol derivative. The peak crystallization temperature upon cooling was considerably increased by the incorporation of either the nucleant or DSF. Additionally, a much higher proportion of orthorhombic crystals developed in relation to the monoclinic ones. Moreover, the mechanical responses were estimated from the microhardness experiments and significant improvements were found with increasing DSF contents. All of these findings indicate that the use of silanized DSF is a fairly good approach for the preparation of polymeric eco‐composites, taking advantage of the widespread availability of this lignocellulosic material, which is otherwise wasted.This research was funded by AEI/FEDER, UE (grant number MAT2016-79869-C2-1-P), and CSIC (grant number 2020AEP129

Toughening of Immiscible rPS/SAN Blends by SEBS Elastomers: Properties and Morphology

In this research, an attempt was made to improve compatibility in a polymer blend composed of incompatible constituents, namely, recycled polystyrene (rPS) and polystyrene-co-acrylonitrile (SAN), through the addition of a compatibilizer. The compatibilizing agent, styrene-ethylenebutadienestyrene block copolymer (SEBS), was added to the polymer blend in ratios of 5 and 10 wt%. For this purpose, blends of rPS and SAN at different ratios, without and with varying concentrations of compatibilizer, were prepared by melt blending using a co-rotating twin-screwextruder. Mechanical properties including tensile and impact strength, rheological properties (RPA), thermal behaviour (DSC) and morphological characteristics (SEM) were evaluated. According to the results obtained by complex viscosity, the blends behave as a pseudoplastic fluid. The results showed that the addition of SEBS increased the Izod impact strength and the elongation at break and decreased the tensile strength and tensile modulus. rPS/SAN blend modified with SEBS had better mechanical properties than the rPS/SAN alloy. SEM photographs revealed that the SEBS was not only distributed in the SAN phase but also distributed in rPS phase in rPS/SAN/SEBS blend. Furthermore, DSC analysis for blends of rPS/SAN gave a good indication of the improvement on miscibility for most compositions. SEM micrographs of tensile fracture surfaces indicated that the formation of the co-continuous phase and the improvement of interface adhesion are the most important reasons for the excellent tensile properties of the rPS/SAN/SEBS blends. Within the range of analysed compositions, the morphologies investigated by SEM are typical of immiscible blends.K.B. would like to thank Dr Maria del Pilar Posadas Bernal, Dr Patricia Sampe- droTejedor and Grupo de Elastomeros for their help in hosting him as a doctoral student to carry out the experimental part of his PhD thesis at the Elastomeros laboratory, Instituto de Ciencia y Tecnologia de Polimeros (ICTP-CSIC) Madrid, Spain. This research was funded by Spanish Ministry of Science and Innovation (MINECO) through the research projects RTI2018-096636-J-100 and PID2020- 119047RB-100.Peer reviewe

Prediction study of structural, electronic and optical properties of 4C16H10Br2O2 Bis (m-bromobenzoyl) methane crystals

By first-principles calculations with density functional theory and a pseudopotential approach, the structural, electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc (N°60) and P21/c (N°14) space group are investigated. All computations are determined by a generalized gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856 (1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and the minimum of the conduction band are both situated at the YA center

On a contribution to study some mechanical properties of WEEE recycled polymer blends

This research deals with the study of acrylonitrile-butadiene-styrene/polycarbonate (ABS/PC) totally derived from wastes of electrical and electronic equipment (WEEE). The aim of this study is to investigate the macroscopic use properties of 100% recycled polymers and compare them with the virgin materials. First, a preliminary work of sorting and characterization of the wastes was necessary to identify the predominant polymer components in the lots. Then, four compositions of blends (ABS/PC) were performed at laboratory using the twin-screw extruder and injection techniques. Next, a series of experimental tests were carried out to investigate the morphology of the blends, their mechanical and thermo-mechanical behavior. The experimental results highlighted the synergistic effect by blending ABS and PC wastes. In addition, the comparison with the virgin mixtures has shown a decrease in the mechanical properties of the waste blends, however, the mechanical behavior is still ductile and the blends stiffness was enhanced