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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]

Polymer blends based on plastic waste and natural biodegradable polymers is an interesting strategy in view of environmental and technical concerns. This article investigates the structure, thermal and physical properties of virgin and post‐industrial polymethyl methacrylate (PMMA) waste/pristine chitosan (Cs) bio‐blends. Waste PMMA was generated by an extrusion process for the manufacturing of sheets. The results of gel permeation chromatography analysis (GPC) show a slight decrease (about 8%) in the average molecular weight of PMMA after extrusion. Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR‐ATR) spectra do not reveal changes in the chemical structure of post‐industrial PMMA/Cs blends compared to virgin PMMA/Cs samples, indicating that chain scission reactions are the dominant degradation mechanism of PMMA during processing. Dynamic mechanical analysis (DMA) results reveal a single glass transition temperature (Tg) for the blends, implying miscibility of the components. Post‐industrial PMMA/Cs samples exhibit slightly lower values of Tg compared to virgin PMMA/Cs blends. The post‐industrial PMMA waste slightly reduces nano‐mechanical properties and thermal stability of the blends relative to those from virgin PMMA. In contrast, it increases the water uptake of the bio‐blends compared with virgin PMMA. Highlights: Chain scission is the dominant degradation mechanism of PMMA during extrusion.Miscibility between the homopolymers within the blends.PMMA waste slightly reduced the nano‐mechanical properties of the bio‐blends.Post‐industrial PMMA waste increased the water uptake of the bio‐blends.Possibility of using post‐industrial PMMA waste by blending with chitosan. [ABSTRACT FROM AUTHOR]

Accelerated photooxidation under ultraviolet (UV) test of polyamide 11 (PA11) films filled with unmodified vermiculite clay at 5 wt% was investigated up to 600 h. Film samples of ~60-[micro]m thick were prepared by melt compounding using a cast extruder and exposed to UV light irradiation at [lambda] > 295 nm. Fourier transform infrared (FTIR) spectra indicated similar structural changes occurring in both PA11 and PA11 /unmodified vermiculite nanoclay (UVMC) nanocomposite along the photooxidation process, resulting in imides and carboxylic acids as the main carbonyl products. It was however observed that the formation rate of carbonyls in the PA11 /UVMC nanocomposite was slower than neat PA11. This behavior is consistent with the yellowing index evolution determined by ultraviolet-visible (UV-vis) spectroscopy. Further, the photooxidation stability of the samples was also evaluated by the onset oxidation temperature determined by differential scanning calorimetry. The results indicated a better stability of the nanocomposite film than neat PA11, corroborating well the data obtained by FTIR and UV-vis techniques., INTRODUCTION Polyamide 11 (PA11) is a bio-based engineering thermoplastic derived from a renewable resource (castor oil) [1]. It is biocompatible and has the advantage of being less hydrophilic than the [...]

Halloysite nanotubes (HNTs) were successfully incorporated as flame retardants in polyamide-11 (PA11) after their modification with methyl phosphonic acid. Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry were used to evidence the functionalization of the clay. Raw and modified HNTs were then incorporated by melt mixing in PA11 at 20 wt%. Compositions containing both ammonium polyphosphate (APP) and HNTs were also prepared. TGA and pyrolysis combustion flow calorimeter exhibited enhancement in thermal stability upon incorporation of both raw and modified halloysite nanotubes while APP causes degradation at lower temperature. Cone calorimeter data showed that modified halloysite acts by forming an insulating barrier during the combustion, which limits heat and mass transfers. Moreover, elemental analysis of sample residues after cone test evidenced that a part of the phosphorus of the modified halloysite was transferred to the gaseous phase. These results suggest the full potential of halloysite as fire retardant agent for polyamides., INTRODUCTION Polyamide-11 (PA11) is a biocompatible commercial aliphatic polymer with excellent characteristics such as good oil resistance or low coefficient of friction and has the advantage to be less hydrophilic [...]

This paper is a follow-up to a previous work where we defined and generated the set of all possible compromises of multilevel multiobjective linear programming problems (ML-MOLPP). We introduce a new algorithm to solve ML-MOLPP in which the adaptive method of linear programming is nested. First, we start by generating the set of all possible compromises (set of all non-dominated solutions). After that, an algorithm based on the adaptive method of linear programming is developed to select the best compromise among all the possible settlements achieved. This method will allow us to transform the initial multilevel problem into an ML-MOLPP with bonded variables. Then, apply the adaptive method which is the most efficient to solve all the multiobjective linear programming problems involved in the resolution process instead of the simplex method. Finally, all the construction stages are carefully checked and illustrated with a numerical example. [ABSTRACT FROM AUTHOR]

The effect of gamma irradiation on neat Polyamide-11 (PA11) and PA11 filled with 3 wt% of halloysite nanotubes (HNTs) was investigated at various doses up to 100 kGy in air and at room temperature. The irradiation test was conducted on sample films prepared by a twin-screw extruder in the first step then cast extrusion. The study showed the formation of a maximum of gel fraction up to 10 and 20 kGy for neat PA11 and PA11/HNTs, respectively. Furthermore, the results indicated the occurrence of crosslinking at low irradiation dose, whereas chain scission took place at higher ones. Additionally, the results revealed that the presence of HNTs limits the impacts of gamma irradiation through a barrier effect. An optimum irradiation dose was found for thermal and mechanical properties, corresponding to the dose for maximum gel formation. Moreover, experimental design was implemented to highlight the main incidences and interactions of both halloysite incorporation and radiation dose on some relevant effects of gamma irradiation. [ABSTRACT FROM AUTHOR]

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) with different PHBV/PLA weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) were prepared by melt compounding. To improve the miscibility between the two components of the blend, low amount of compatibilizing agent (5 wt%), obtained by grafting maleic anhydride onto PHBV, was used. When compared with the uncompatibilized blends, the compatibilizer presence induces a greater interfacial adhesion. The effect of Cloisite 30B (C30B) on the blend morphology and the blend properties was also investigated. The morphology of the different blends as well as the evolution of their material properties were discussed in terms of the nanoclay and compatibilizing agent contents. A synergistic effect of compatibilizer and C30B was highlighted leading to an improved miscibility of the two blend components. The resulting properties were correlated with the morphology observed for the different blends., INTRODUCTION During this last decade, much attention has been focused on both biodegradable polymers that can be produced from renewable resources and polymer layered silicate nanocomposites [1-3]. Among all these [...]