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This work aims at investigating the effect of two eco‐friendly chemical treatments of Agave Americana fibers (AAFs) on morphology and mechanical properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx) biocomposites prepared by melt compounding. Acid citric and sodium bicarbonate treatments are used separately to modify the fiber surface before their incorporation into PHBHHx matrix at 30 wt%. The study reveals through SEM observations that the fracture surface of untreated PHBHHx biocomposite shows a poor fiber‐matrix adhesion with the presence of many microvoids at interface and also some fibers pullout. However, less surface defects with a finer morphology are observed on the treated biocomposite samples resulting in improved tensile and flexural properties compared with neat polymer, being however, more pronounced for those modified with sodium bicarbonate. The study highlights the beneficial effect of the green treatments investigated to enhance the mechanical properties of PHBHHx biocomposites. [ABSTRACT FROM AUTHOR]

Chemical treatments are used to remove hydrophilic OH groups and surface particles from the fiber surface for increasing aspect ratio of fibers and subsequently, mechanical properties. In this paper, the effect of two eco‐friendly chemical treatments on morphology, chemical structure, and thermal stability of Agave Americana fibers (AAFs) is investigated. The first chemical treatment of AAF is based on citric acid (C6H8O7) to substitute OH groups contained in AAF by ester groups, while the second one involves sodium bicarbonate (NaHCO3) to remove the lignin and hemicellulose components with the aim to promote good fiber‐matrix adhesion. Attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) data shows that both treatments are efficient to remove hemicelluloses and a part of lignin contained in AAF resulting in a rough and clean fiber surface. Thermal stability of AAF has clearly increased by NaHCO3 treatment compared to untreated one, unlike C6H8O7, which reduces this property. The study highlights the possibility of substituting conventional polluting chemical treatments with environmentally friendly ones to modify the surface of plant fibers for polymer composites reinforcement. [ABSTRACT FROM AUTHOR]

The objective of the paper is to investigate the effect of organo‐modified sepiolite (MSep) on morphology, mechanical, and viscoelastic properties of polyamide‐11 (PA11) prepared by melt compounding at 5 wt.%. The study reveals that the addition of both unmodified sepiolite (USep) and organo‐MSep to PA11 improves the reinforcement effect of the nanocomposite materials compared to neat PA11, being however more pronounced for the organo‐modified one. Indeed, morphological analysis by transmission electron microscopy (TEM) shows a finer dispersion of organo‐MSep in PA11 matrix than the unmodified one, which is characterized by a significant presence of fibers aggregates in number and size. Further, dynamic mechanical analysis (DMA) results are in a good agreement with both tensile properties and TEM observations. [ABSTRACT FROM AUTHOR]

Given the global challenge of plastic pollution, the development of new bioplastics to replace conventional polymers has become a priority. It is therefore essential to achieve a balance in the performances of biopolymers in order to improve their commercial availability. In this topic, this study aims to investigate the morphology and properties of poly(lactic acid) (PLA)/ poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) (at a ratio of 75/25 (w/w)) blends reinforced with halloysite nanotubes (HNTs) and compatibilized with poly(lactic acid)-grafted maleic anhydride (PLA-g-MA). HNTs and PLA-g-MA were added to the polymer blend at 5 and 10 wt.%, respectively, and everything was processed via melt compounding. A scanning electron microscopy (SEM) analysis shows that HNTs are preferentially localized in PHBHHx nodules rather than in the PLA matrix due to its higher wettability. When HNTs are combined with PLA-g-MA, a finer and a more homogeneous morphology is observed, resulting in a reduction in the size of PHBHHx nodules. The presence of HNTs in the polymer blend improves the impact strength from 12.7 to 20.9 kJ/mm2. Further, with the addition of PLA-g-MA to PLA/PHBHHX/HNT nanocomposites, the tensile strength, elongation at break, and impact strength all improve significantly, rising from roughly 42 MPa, 14.5%, and 20.9 kJ/mm2 to nearly 46 MPa, 18.2%, and 31.2 kJ/mm2, respectively. This is consistent with the data obtained via dynamic mechanical analysis (DMA). The thermal stability of the compatibilized blend reinforced with HNTs is also improved compared to the non-compatibilized one. Overall, this study highlights the effectiveness of combining HNTs and PLA-g-AM for the properties enhancement of PLA/PHBHHx blends. [ABSTRACT FROM AUTHOR]

The effect of hydroxyapatite (HAp) synthesized by the chemical precipitation process on the morphology and properties of composites based on poly(lactic acid) (PLA) was investigated at various filler content ratios, i.e., 5, 10 and 15 wt%. Both neat PLA and PLA-based composites were first prepared using the solvent casting method, followed by melt compounding in an internal mixer, whereas tensile specimens were obtained by thermo-compression. The study revealed that the addition of 5 wt% of HAp into the PLA led to a slight improvement in both the thermal stability and tensile properties of the composite material in comparison with neat PLA and other composite samples. Indeed, the values of the tensile strength and modulus increased from approximately 61 MPa and 2.9 GPa for the neat PLA to almost 64 MPa and 3.057 GPa for the composite sample, respectively. Moreover, the degradation temperature at a 5 wt% mass loss also increased by almost 5 °C compared to other samples, due probably to a finer dispersion of the HAp particles in the PLA, as observed under a scanning electron microscope. Furthermore, the FT-IR spectra displayed some changes in the chemical structure of the PLA/HAp (5 wt%), indicating the occurrence of filler-matrix interactions. At a higher filler content ratio, a decrease in the properties of the PLA/HAp composites was observed, being more pronounced at 15 wt%. The PLA composite containing 5 wt% HAp presents the best compromise among the investigated properties. The study highlighted the possibility of using HAp without any prior surface treatment as a reinforcement in PLA composite materials. [ABSTRACT FROM AUTHOR]

The effects of gamma irradiation on the morphology and physical properties of various blends based on poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) and polylactide (PLA): 50/50 w/w were studied with and without PHBV- g -MA and organomodified montmorillonite used as the compatibilizer and reinforcement agent, respectively. The different blend compositions prepared by melt compounding were compression molded to thin films of an average thickness of 150 μm, and subjected to 25, 50 and 100 kGy at room temperature; the dose rate being 1.0 Gy/h. Infrared spectra analysis indicated the occurrence of some chemical modifications in the irradiated samples, in particular an absorbed dose of 100 kGy resulted in the formation of a large absorption band in the carbonyl region. Size exclusion chromatography (SEC) data showed a decrease in the average molecular weight for all irradiated samples with increasing absorbed dose due to chain scission. Nanoindentation tests showed that γ-irradiation significantly decreased both modulus and hardness of neat PHBV and neat PLA after 100 kGy, whereas no noticeable changes were observed for PHBV/PLA blends. Thermogravimetric analysis (TGA) and pyrolysis combustion flow calorimetry (PCFC) tests revealed that the organomodified clay can act as a compatibilizer and compensate for the effect of irradiation on both thermal stability and fire retardancy of PHBV/PLA blends. [ABSTRACT FROM AUTHOR]

Abstract: The paper aims to study blend properties of biodegradable polymers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) prepared by melt mixing. Blend compositions based on PHBV/PLA were investigated according to the following weight ratios, i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 wt%. The study showed through scanning electron microscopy (SEM) that blends of PHBV/PLA are not miscible. This is consistent with differential scanning calorimetry (DSC) data which indicate the presence of two distinct glass transition temperatures (Tg) and melting temperatures (Tm), attributed to the neat polymers, over all the range of blend compositions. Water and oxygen barrier properties of PHBV/PLA blends are significantly improved with increasing the PHBV content in the blend. Further, morphological analyzes indicated that increasing the PHBV content in the polymer blends results in increasing the PLA crystallinity due to the finely dispersed PHBV crystals acting as a filler and a nucleating agent for PLA. On the other hand, the addition of PLA to the blend results in a very impressive increase in the complex viscosity of PHBV. Moreover, the rheological data showed that, excluding the specific behavior of the neat polymers at low frequencies, i.e. less than 0.1 Hz, the complex viscosity of PHBV/PLA blends fits the mixing law well. [Copyright &y& Elsevier]

This work aims to study the effects of date stone flour (DSF) on morphology, thermal, and mechanical properties of polypropylene (PP) composites in the absence and presence of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) used as the compatibilizer. DSF was added to the PP matrix at loading rates of 10, 20, 30, and 40 wt %, while the amount of compatibilizer was fixed to the half of the filler content. The study showed through scanning electron microscopy analysis that EBAGMA compatibilizer improved the dispersion and the wettability of DSF in the PP matrix. Thermogravimetric analysis (TGA) indicated a slight decrease in the decomposition temperature at onset ( Tonset) for all composite materials compared to PP matrix, whereas the thermal degradation rate was slower. Differential scanning calorimetry (DSC) data revealed that the melting temperature of PP in the composite materials remained almost unchanged. The nucleating effect of DSF was however reduced by the compatibilizer. Furthermore, the incorporation of DSF resulted in the increase of stiffness of the PP composites accompanied by a significant decrease in both the stress and strain at break. The addition of EBAGMA to PP/DSF composites improved significantly the ductility due to the elastomeric effect of EBAGMA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

The paper reports some results of an experimental study on ethylene vinyl acetate (EVA) copolymer/olive husk flour (OHF) composites incorporated at various filler ratios (15, 30 and 45 wt%) in the absence and the presence of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) terpolymer used as a compatibilizer. The composite samples have been prepared by melt blending and their chemical structure, as well as morphological, mechanical and water absorption properties investigated. It is shown that the compatibility of EVA/OHF composites is improved by the addition of EBAGMA terpolymer. Indeed, FT-IR analysis shows that chemical interactions have occurred between the compatibilizer and the base blend components. Morphological results from SEM shows better dispersion of the wood particles in the EVA matrix and the resulting composite samples exhibit better tensile properties at break and lower water absorption than the uncompatibilized ones. Moreover, the results indicate that the loading concentrations of both OHF and EBAGMA have an effect on the composite properties. [ABSTRACT FROM AUTHOR]

Blends of poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) and poly(butylene succinate) (PBS) with different PHBV/PBS weight ratios (100/0, 75/25, 50/50 and 0/100) were elaborated by melt mixing. The morphological investigation of the different samples, in comparison with that of neat PHBV and neat PBS, pointed out that PHBV/PBS blends form a biphasic system over the whole composition range. Low amount of compatibilizing agent (5 wt%), obtained by grafting maleic anhydride (MA) onto PHBV, i.e. PHBV-g-MA, was used for improving the miscibility between the two components of the blend. The incorporation of a fibrous filler as the sepiolite, easily dispersible in a polymer matrix, was also investigated. The morphology of the different blends as well as the evolution of their material properties were discussed in terms of the sepiolite and compatibilizing agent contents. The dispersion of PBS in the PHBV matrix markedly became finer with incorporation of sepiolite and PHBV-g-MA, due to enhanced interactions between the components. This paper highlighted a synergistic effect induced by the presence of both compatibilizer and sepiolite leading to an improved miscibility of the two blend components. The resulting properties were correlated with the morphology observed for the different blends. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the effect of various surface treatments on Aloe Vera fibers (AVF) used as reinforcement in PHBHHx biocomposites prepared by melt compounding. AVF were subjected to various surface treatments including alkaline, organo-silanes and combined alkaline/organo-silanes treatments. Both untreated and treated AVF were added to PHBHHx at filler content of 20 wt% and the resulted biocomposites were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), water absorption test and rheological measurements. The study showed that the combined alkaline/organo-silanes treatment of AVF resulted in better morphology and properties of PHBHHx biocomposite compared to untreated AVF and those treated either with alkaline or with organosilanes. Indeed, SEM analysis of the fracture surface of PHBHHx/AVF treated with combined alkaline-organosilanes showed better fiber-matrix interactions compared to the other samples. As a result, rheological properties, i.e., complex viscosity (η∗), storage modulus (G′) and loss modulus (G″) were increased. Higher resistance to water absorption was observed for PHBHHx/AVF treated with combined alkaline-organosilanes. Whereas, the various surface fiber treatments led to no noticeable change in thermal characteristics of the biocomposites. This study highlights the effectiveness of combined alkaline/organo-silanes treatment of AVF over alkaline and organo-silanes and their applications in PHBHHx biocomposites as an interesting source of cellulosic reinforcing materials. • Effect of surface treatments on Aloe Vera fibers (AVF) used as reinforcement in PHBHHx biocomposites. • Morphological and properties characterization of AVF and PHBHHx/AVF: 80/20 (w/w) biocomposite before and after treatments. • Improvement in fiber-matrix interface achieved by the combined alkaline-organosilanes treatment of AVF. • Interesting AVF source of cellulosic reinforcement materials. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs) were functionalized by grafting styrene-ethylene-butylene-styrene (SEBS) copolymer chains after a two-step modification procedure. Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) were used to determine the grafting rate. Then, raw and functionalized halloysites were incorporated into polyamide-11(PA11)/ styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) blends (85/15 w/w). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show a good dispersion of both halloysites particles and SEBS-g-MA nodules in the PA11 matrix. In the case of functionalized halloysite, the presence of HNTs bundles surrounded with fine SEBS-g-MA nodules is observed. Atomic force microscopy (AFM) also highlighted the different blends morphologies. Incorporation of functionalized halloysite leads to an improvement of the thermal properties without affecting the PA11 crystallization. Moreover, mechanical performance, especially toughness, was highly improved in the presence of functionalized halloysite due to a good stress transfer from the matrix to the modified halloysite agglomerates surrounded by SEBS-g-MA. [ABSTRACT FROM AUTHOR]