Search

This study explores the effect of internal gas pressure (P) on closed-cell natural rubber (NR) foams. Three key factors are analyzed using a 3D model during uniaxial compression: (1) the initial gas pressure (P0 = 1, 2, and 3 atm) inside the cells, (2) different cell sizes (D = 0.1, 0.2, 0.3, and 0.4 mm in diameter), and (3) the presence of defects (holes in the cell walls) in terms of their sizes (d = 0.07 to 0.1 mm). The findings reveal a negative relationship between the initial gas pressure and the relative internal gas pressure (α = P/P0) and a direct correlation with stress during compression. For instance, a change from 1 to 3 atm of the initial internal gas pressure results in a 158% decrease in α with only a 3% increase in stress. Larger cell sizes contribute to higher α but lower stress levels during compression. Changing the cell size from 0.1 to 0.4 mm generates a 27% increase in α but a 45% drop in stress. An analysis of hole sizes (cell connection) indicates that larger holes result in higher relative internal gas pressure, while smaller holes lead to higher stress levels because of more flow restriction. For example, increasing the hole size from 0.07 to 0.1 mm leads to an 8% higher α but a 32% stress reduction. These findings highlight the significant effect of the internal gas pressure inside the cells in determining the mechanical properties of rubber foams, which are generally neglected. The results also provide useful insights for better material design and different industrial applications. This study also generates predictive models to understand the relationships between stress, strain, initial gas pressure, cell size, and defects (holes/connections), enabling the production of tailor-made rubber foams by controlling their mechanical behavior. [ABSTRACT FROM AUTHOR]

This study presents the effect of iron chloride addition on the production of nanocarbon fibers from softwood Organosolv lignin. It was shown that adding 2% FeCl3 to the lignin solution before electrospinning to produce lignin nanofibers increased the thermal resistance of lignin fibers during stabilization. FTIR and XPS analyses of the lignin fibers stabilized with and without FeCl3 revealed that the temperature rate could be increased in the presence of FeCl3 from 1 to 3 °C/min. The optimal temperature to stabilize the lignin fibers was found to be 250 °C, as higher temperatures led to thermal degradation. Also, carbon fibers were successfully produced from pure softwood Organosolv lignin fibers. Carbonization tests were conducted under nitrogen and the best parameters were determined to be a ramp of 10 °C/min until 600 °C with a holding time of 2 h. Furthermore, the effect of 2% FeCl3 addition in the lignin solution was investigated during these processes. XPS analysis showed a 93% carbon content for fibers carbonized with and without FeCl3 addition, while SEM images revealed some surface roughness in fibers with FeCl3 after carbonization. These results confirm that FeCl3 addition influences the carbon nanofiber production. [ABSTRACT FROM AUTHOR]

Agave Tequilana Weber (ATW) is the base ingredient for preparing tequila liquor; tequila production yields tons of waste rich in cellulose representing environmental issues. Cellulose nanocrystals (CNC), the crystalline regions extracted from cellulose microcrystals, were obtained from the waste of ATW as an attractive alternative to reinforce polymeric materials. CNC were grafted with (poly (2-ethyl hexyl acrylate) to improve compatibility with hydrophobic polymers. The CNC pristine (CNCP) and grafted (CNCG) were dispersed in PLA (0.5, 1 and 2 wt.%), employing several melt processing stages. CNC distribution within PLA matrix was followed using SEM and TEM. Also, thermal properties were characterized through differential scanning calorimetry and thermogravimetric analysis. Thermal stability of nanocomposites increased with CNC, CNCG nanocomposites showed better results (Td ~ 370 °C) than CNCP nanocomposites (Td ~ 366 °C). The degree of crystallinity showed for CNCG (25.1%) was higher than for CNCP (21.1%) nanocomposites. The tensile properties were improved with CNCP (0.44 MPa) and CNCG (2.11 MPa) content. The CNC increased the shear properties of PLA melt and exhibited a strain-hardening behavior during elongational rheology test. The CNC and CNCG are an interesting alternative to modify the melt rheological behavior and the mechanical behavior in the solid-state of low melt strength polymers, which could be thermally degraded during processing. Composites could be used to produce films for the food industry through blow-extrusion processing. [ABSTRACT FROM AUTHOR]

Three poly (lactic acid) (PLA) resins with molecular weight (Mw) equal to 55 (3251D), 125 (L105) and 163 (LX175) kg/mol were characterized in terms of capillary viscosity, mechanical and thermal properties and used to produce blown films. The effect of temperature, extrusion rate, stretching (TUR) and blow-up (BUR) ratios were evaluated to determine the optimum processing conditions for blown films based on the bubble stability and to determine their final tensile properties. As expected, the processing temperature was the most critical parameter on the film stability. The lower Mw PLA showed limited processing stability. Stable conditions were found at higher temperature (200°C) for higher Mw. These results correlate with the PLA viscosity (melt strength). Finally, the PLA film tensile strength (TS) strongly depended on their processability. For example, 3251D and L105 required high stretching (TUR = 3.4 and 7) for maximum TS (30 and 64 MPa) with a low blow-up ratio (BUR = 1.02–1.15). However, a moderate increase in BUR (10% at TUR = 3) led to a substantial drop in TS (from 29 MPa to 21 MPa for PLA 3251D and 44 MPa–34 MPa for L105). Overall, LX175 was the most interesting resin with 49 MPa TS which was independent of the BUR and TUR used in this investigation. [ABSTRACT FROM AUTHOR]

This work investigates the properties of different types of regenerated recycled rubbers (RR1 and RR2) to produce thermoplastic elastomers (TPE) based on recycled high-density polyethylene (RHD) as the matrix. The higher regeneration degree of RR2 (24%) compared to RR1 (15%) was able to better restore the plasticity and processability of the ground tire rubber (GTR). So better entanglement between RR2 free chains and the thermoplastic macromolecules was obtained inducing stronger interfacial interaction leading to higher elongation at break (159%) and impact strength (342 J/m) of the blends filled with 80 wt.% RR2. To further improve the adhesion and achieve rubber-like properties, ethylene vinyl acetate (EVA) was used as a compatibilizer. The microstructure analysis showed that uniform dispersion of the particles and ground tire rubber encapsulation by EVA increased the resistance to crack propagation and failure of the compatibilized blends. The swelling, mechanical and physical properties of the ternary blends (RHD/GTR/EVA) showed that EVA improved the interfacial interactions between GTR and RHD which was confirmed by enhanced elongation at break (203%) and impact strength (379 J/m) by the addition of 10 wt.% EVA. [ABSTRACT FROM AUTHOR]

During recent decades, rubber foams have found their way into several areas of the modern world because these materials have interesting properties such as high flexibility, elasticity, deformability (especially at low temperature), resistance to abrasion and energy absorption (damping properties). Therefore, they are widely used in automobiles, aeronautics, packaging, medicine, construction, etc. In general, the mechanical, physical and thermal properties are related to the foam's structural features, including porosity, cell size, cell shape and cell density. To control these morphological properties, several parameters related to the formulation and processing conditions are important, including foaming agents, matrix, nanofillers, temperature and pressure. In this review, the morphological, physical and mechanical properties of rubber foams are discussed and compared based on recent studies to present a basic overview of these materials depending on their final application. Openings for future developments are also presented. [ABSTRACT FROM AUTHOR]

This article reviews the main developments associated with density graded polymer composite foams. After a short introduction, a discussion is made on both density graded polymer-based composites and foams separately to better understand the challenges when both structures are combined together to produce composite foams. In all cases, the basic concepts, fabrication methods, main properties and general applications are presented. Opening for future works are also presented to conclude. [ABSTRACT FROM AUTHOR]

This work investigated the static and fatigue behavior of sisal fiber-reinforced foam concrete under flexural loading. In particular, the effect of fiber content (0–0.3 vol.%) was determined by measuring the strains at two positions (mid-span and near the support of the beam) to relate with the flexural stiffness. The results showed that under static loading, sisal fiber can increase the flexural strength and decrease the flexural stiffness of the foam concrete when the specimen broke, especially, as the sisal fiber content was taken as 0.15%. Under cyclic loading, the flexural stiffness of the plain foam concrete decreased rapidly at the beginning, sisal fiber can delay the stiffness degradation of composites. When the sisal fiber content is below 0.05%, a linear relationship between the flexural stiffness and the logarithmic fatigue life of the composite was found. But for fiber content above 0.05%, another linear relationship was obtained when the fatigue life was used. It was also found that the flexural stiffness obtained from two positions was linearly correlated. If the slopes of the fitting lines were fixed as 2, a mathematical model between the flexural stiffness at the mid-span and the flexural stiffness near the support was obtained. [ABSTRACT FROM AUTHOR]

Fully biobased polylactide (PLA)/polyamide-11 (PA11) blends were prepared by melt mixing with an elastomer intermediate phase to address the low elasticity and brittleness of PLA blends. The incorporation of a biobased elastomer made of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene oxide (PEO) copolymers was found to change the rigid interface between PLA and PA11 into a much more elastic/deformable one as well as promote interfacial compatibility. The interfacial tension of the polymer pairs and spreading coefficients revealed a high tendency of PEO to spread at the PLA/PA11 interface, resulting in a complete wetting regime (interfacial tension of 0.56 mN/m). A fully percolated rubbery phase (PEO) layer at the PLA/PA11 interface with enhanced interfacial interactions and PLA chain mobility contributed to a better distribution of the stress around the dispersed phase, leading to shear yielding of the matrix. The results also show that both the morphological modification and improved compatibility upon PEO addition (up to 20 wt %) contributed to the improved elongation at break (up to 104%) and impact strength (up to 292%) of the ternary PLA/PA11/PEO blends to obtain a super-tough multiphase system. [ABSTRACT FROM AUTHOR]

Waste tire textile fibers (WTTF), as a by-product (10–15% by weight of tires) of end-of-life tires (ELT) mechanical recycling (grinding), are classified as hazardous wastes and traditionally burnt (thermal recycling) or buried (landfilling), leading to several environmental and ecological issues. Thus, WTTF still represent an important challenge in today's material recycling streams. It is vital to provide practical and economical solutions to convert WTTF into a source of inexpensive and valuable raw materials. In recent years, tire textile fibers have attracted significant attention to be used as a promising substitute to the commonly used natural/synthetic reinforcement fibers in geotechnical engineering applications, construction/civil structures, insulation materials, and polymer composites. However, the results available in the literature are limited, and practical aspects such as fiber contamination (~65% rubber particles) remain unsolved, limiting WTTF as an inexpensive reinforcement. This study provides a comprehensive review on WTTF treatments to separate rubber and impurities and discusses potential applications in expansive soils, cement and concrete, asphalt mixtures, rubber aerogels and polymer composites. [ABSTRACT FROM AUTHOR]

In this study, we focused on the synergistic effect between carbon black (CB) and graphene nanoplatelets (GNPs) of various aspect ratios and specific surface areas as hybrid fillers in natural rubber (NR) nanocomposites. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM) were carried out to characterize the GNPs properties, while dynamic mechanical analysis (DMA), tensile properties, hardness, thermal conductivity, swelling behavior in toluene and SEM were performed on the NR nanocomposites. The results showed the positive effect of GNPs on the thermal and mechanical properties, which was attributed to the high surface area and aspect ratio of the GNPs playing a vital role in producing a conductive GNPs/CB hybrid fillers' network. Among the three GNPs investigated, the sample having the highest lateral dimension (25 µm) led to a denser and more thermally conductive network. On the other hand, the GNPs/CB hybrid fillers' synergy increased with increasing concentration inside the NR nanocomposites up to 5 phr due to their good dispersion as confirmed via SEM. [ABSTRACT FROM AUTHOR]

In this work, an efficient technique was used to produce porous membranes for different applications. Polyethylene (PE) was selected for the matrix, while corn starch (CS) was used to create the porous structure via leaching. The membranes were produced by continuous extrusion (blending)–calendering (forming) followed by CS leaching in a 20% aqueous acetic acid solution at 80 °C. A complete characterization of the resulting membranes was performed including morphological and mechanical properties. After process optimization, the gas transport properties through the membranes were determined on the basis of pure gas permeation including CH4, CO2, O2, and N2 for two specific applications: biogas sweetening (CH4/CO2) and oxygen-enriched air (O2/N2). The gas separation results for ideal permeability and selectivity at 25 °C and 1.17 bar (17 psi) show that these membranes are a good starting point for industrial applications since they are low-cost, easy to produce, and can be further optimized. [ABSTRACT FROM AUTHOR]

The effect of interfacial interaction and processing methods (one-step and two-step) on the structure–property relationships of ternary blends was investigated. The addition of ethylene-vinyl acetate (EVA) and ethylene octene copolymer (POE) resulted in homogeneous structure and greatly improved rubber-like properties of recycled high-density polyethylene (rHDPE) and regenerated tire rubber (RR) blends. Interfacial tension calculations revealed a high tendency of POE to encapsulate rubber particles (complete wetting). The two-step processing contributed to perfect encapsulation of the rubber phase via a soft/thick POE interface resulting in uniform RR particle dispersion, high elongation at break (138.5%), and impact strength (394 J/m) of rHDPE/(RR/POE) (20/80) ternary blend. [ABSTRACT FROM AUTHOR]

In this work, recycled high density polyethylene (rHDPE) was compounded with regenerated tire rubber (RR) (35–80 wt.%) and reinforced with recycled tire textile fiber (RTF) (20 wt.%) as a first step. The materials were compounded by melt extrusion, injection molded, and characterized in terms of morphological, mechanical, physical, and thermal properties. Although, replacement of the rubber phase with RTF compensated for tensile/flexural moduli losses of rHDPE/RR/RTF blends because of the more rigid nature of fibers increasing the composites stiffness, the impact strength substantially decreased. So, a new approach is proposed for impact modification by adding a blend of maleic anhydride grafted polyethylene (MAPE)/RR (70/30) into a fiber-reinforced rubberized composite. As in this case, a more homogeneous distribution of the fillers was observed due to better compatibility between MAPE, rHDPE, and RR. The tensile properties were improved as the elongation at break increased up to 173% because of better interfacial adhesion. Impact modification of the resulting thermoplastic elastomer (TPE) composites based on rHDPE/(RR/MAPE)/RTF was successfully performed (improved toughness by 60%) via encapsulation of the rubber phase by MAPE forming a thick/soft interphase decreasing interfacial stress concentration slowing down fracture. Finally, the thermal stability of rubberized fiber-reinforced TPE also revealed the positive effect of MAPE addition on molecular entanglements and strong bonding yielding lower weight loss, while the microstructure and crystallinity degree did not significantly change up to 60 wt.% RR/MAPE (70/30). [ABSTRACT FROM AUTHOR]

In this study, foamed recycled high density polyethylene (rHDPE) parts were produced by rotational molding using different concentration (0 to 1% wt.) of a chemical blowing agent (CBA) based on azodicarbonamide. From the samples produced, a complete morphological, thermal and mechanical characterization was performed. The morphological analysis showed a gradual increase in the average cell size, while the cell density firstly increased and then decreased with increasing CBA content. As expected, increasing the CBA content decreased the foam density as well as the thermal conductivity. Although increasing the CBA content decreased both tensile and flexural properties, the impact strength showed a similar trend as the cell density with an optimum CBA content around 0.1% wt. Finally, neat rHDPE samples were also produced by compression molding. The results showed negligible differences between the rotomolded and compression molded properties indicating that optimal rotomolding conditions were selected. These results confirm the possibility of using 100% recycled polymers to produce rotomolded foam parts. [ABSTRACT FROM AUTHOR]

The objective of this study was to produce and characterize gelatin films produced by thermo-compression, a technique that requires less processing time and space, making it appropriate for the development of commercial biodegradable protein-based films. A control film of gelatin with glycerol and water (M1) was compared with three films reinforced with Agave angustifolia Haw microfibers (MF) (M2–M4), three films reinforced with bentonite nanoclay (BN) (M5–M7), and three films reinforced with both MF and BN (M8–M10). The surface and cross-section morphology of the films showed some roughness with pores and inhomogeneities as the MF and BN concentration increased. The X-ray diffraction analysis confirmed the nanoclay intercalation. The films thickness was a function of the glycerol content, and all films had an apparent density slightly higher than unity. The films appearance was measured via the CIELab scale where the parameter a* was found to increase toward a reddish color, while b* showed an increasingly yellowish color. The presence of both MF and BN led to increased tortuosity inside the films, thus affecting the permeability of water molecules. Particles addition increased the tensile strength and elasticity, while the elongation at break decreased. The thermal stability improved with particles addition, especially for BN due to its inorganic nature. All the results could be related to a high level of interaction between the components and the protein matrix as observed via Fourier transform infrared spectroscopy, showing proper compatibility and a synergy among the materials. Due to the properties obtained, biomaterials can have good mechanical and high barrier properties combined with short life, disposable and environmentally friendly for food packaging and biomedical applications. [ABSTRACT FROM AUTHOR]

In this work, polypropylene (PP) was foamed via rotational molding using a chemical blowing agent (CBA) based on azodicarbonamide over a range of concentration (0 to 0.5% wt.). The samples were then analyzed in terms of morphological, thermal and mechanical properties. The morphological analysis showed a continuous increase in the average cell size and cell density with increasing CBA content. Increasing the CBA content also led to lower foam density and thermal conductivity. Similarly, all the mechanical properties (tension, flexion and impact) were found to decrease with increasing CBA content. Finally, the efficiency of the rotomolding process was assessed by producing neat PP samples via compression molding. The results showed negligible differences between the rotomolded and compression molded properties at low deformation and rate of deformation indicating that optimal rotomolding conditions were selected. [ABSTRACT FROM AUTHOR]

To simulate macroscopic properties at the molecular level, interfaces must be represented the most efficiently. In the study reported in this article, we use molecular dynamics (MD) simulation to reveal the impact of the environment around nanocrystals constituted of alkane chains on the melting temperature. The Gibbs-Thomson law was used to compare different simulated systems and experimental data. Based on thermodynamics argument, this law discloses the linear relationships between the melting, or crystallisation, temperature and the inverse of the crystal thickness. The crystal edges of simulated nanocrystals and the alkane chain length have been varied. For each nanocrystal, a simulated melting temperature (Tm) was obtained and reported with respect to the crystal thickness. The simulated enthalpy of fusion (Δhm), surface (σe) and lateral (σ) free energies were thus extracted. All these properties have been compared to experimental data, and to properties stemming from nanocrystals in empty space. It is shown that nanocrystals surrounded by amorphous chains lead to values that agree better experimental data showing the great improvement in the model. [ABSTRACT FROM AUTHOR]

In this work, composites based on linear low-density polyethylene and maple wood fibers with and without surface treatment with maleated polyethylene (MAPE) were prepared by dry blending, followed by rotomolding to study the effect of particle size, fiber content, and surface treatment. From the samples produced, a complete characterization of the morphological and mechanical properties was performed. The results obtained showed that MAPE surface treatment improved the fiber–matrix interface quality, which improved the homogeneity, the thermal stability, and the mechanical properties of the composites. The results showed that the effect of particle size was significant as the tensile modulus increased by 7%, 40%, and 73% for 125–250, 250–355, and 355–500 µm at 30 wt% of maple fibers. The tensile strength also increased by 114% at the same fiber loading (30 wt%) when the particle size increased from 125–250 µm to 355–500 μm. Finally, the impact strength with 355–500 µm particles was 52% higher than for 125–250 µm particles at 30 wt% [ABSTRACT FROM AUTHOR]

In this work, multi-wall carbon nanotubes (MWCNT) are added (0–0.5 wt%) into a cement matrix to improve the flexural performance of the resulting nanocomposites. Under static testing, the compressive and flexural strengths were found to increase with MWCNT content with an optimum content of 0.2% and 0.1%, respectively, before decreasing because of dispersion problems (agglomeration). But it was observed that increasing the mixing time and adding silica fume improved the MWCNT dispersion. Under fatigue testing, similar trends were obtained with respect to MWCNT content as the maximum fatigue life was observed at 0.2%. A comparison between nano-silica and MWCNT reinforced concrete is also made showing that MWCNT provides better improvement at lower content. The MWCNT reinforced cement-based composite results were well fitted using linear regressions. Finally, a morphological analysis via scanning electron microscopy (SEM) was performed to explain the results based on the micro-mechanical mechanism of MWCNT reinforced composites. [ABSTRACT FROM AUTHOR]

As consumers become more aware of their health and environment, food manufacturers have begun to incorporate more sustainable nutritional ingredients into their products. Agricultural wastes present a well-established source of highly nutritive and functional ingredients, such as dietary fibers (DF). In order to promote the use of agro-waste DFs as food ingredients, we investigated the physicochemical, technological, and in vitro bioactive properties of seven waste DFs (wheat, bamboo, sugarcane, oat, pea, cocoa, and apple). The results showed these DFs mainly consist of IDF, which was over 90% in wheat, bamboo, sugarcane, and oat fibers. DFs from cocoa, apple, and pea had the highest SDF content, while those from oat, sugarcane, bamboo, and wheat showed negligible SDF content. The highest water-holding and swelling capacities were found in materials with high fiber content, especially insoluble fiber fractions (wheat, bamboo, and sugarcane). In addition to fiber composition, other chemical components of DFs, such as starch in the pea fiber, affect their hydration properties. Insoluble fractions had high porosity, which allowed them to hold more water, leading to increased viscosity. Fibers with low porosity and high soluble fractions (apple and cocoa) had the lowest water-holding and swelling capacities. This study found a positive correlation between the oil-holding capacity and porosity. The adsorption of glucose by the DFs was affected by their viscosity, which was associated with their ability to hold water and sugar molecules. Along with viscosity, cholesterol adsorption capacity was influenced by soluble and insoluble fiber fractions. The functional groups in the DF composition can affect their antioxidant activity and cation exchange capacity. A mapping tool was designed based on the relationship between DF properties and food functions. Using this tool, food manufacturers can select the most promising agro-waste DFs based on their intended applications. [ABSTRACT FROM AUTHOR]

Finite element method (FEM) is used to analyze the mechanical properties of carbon nanotubes (CNTs) reinforced polypropylene (PP) composites. Firstly, polypropylene is assumed as a viscoelastic material, while carbon nanotubes are assumed as linear elastic materials to study the effect of temperature on the mechanical properties of neat PP and CNT/PP nanocomposites. Secondly, to compare the viscoelastic properties of neat PP and CNT/PP nanocomposites, the relaxation time at a specific temperature is used to investigate the relaxation of the nanocomposites for fixed tensile displacements. Thirdly, the effect of CNT volume fraction on the viscoelastic properties of nanocomposites is studied at different temperatures. Finally, to better understand the stress distribution along the CNT axial direction, a single carbon nanotube is isolated in the matrix to compare the stress distribution with nonisolated CNTs. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of cathodic alkaline electro-activation (EA) treatment on the flow behavior and gelling properties of canola proteins and the mixture of sweet whey/canola proteins. Canola proteins alone (C) and whey/canola proteins mixed suspensions (CW) were treated in an alkalinizing electro-activation reactor and then naturalized to neutral pH. The alkaline EA treatment resulted in the production of small aggregates crosslinked by disulfide and covalent bonds. The gelation experiments showed that the EA-treated canola proteins and whey/canola protein samples had a superior capacity to develop an integrated gel structure with higher mechanical and rheological properties and improved water holding capacity compared to the untreated samples. Characterization of interactions involved in the gel network structure suggested that the strong covalent interactions played a prominent role in the network of these EA-treated samples. The SDS-PAGE pattern of the gels made from EA-treated canola proteins and EA whey/canola proteins samples confirmed the presence of intensive protein polymerization through covalent crosslinking in these gels. The results of this study suggest that the alkaline EA treatment is an effective tool for improving the gelation properties of canola proteins and producing whey/canola proteins composite gels with improved functionality. [Display omitted] • Impact of EA on gelation capacity of canola and whey/canola protein were studied. • EA enhanced gelation capacity of canola and whey/canola protein solutions. • Gels made from EA-treated samples showed higher elasticity and mechanical strength. • Gels made from EA-treated samples had more uniform and integrated microstructure. • WHC of the gels prepared from EA-treated samples was higher. [ABSTRACT FROM AUTHOR]

The effect of polyester recycled tire fibers (RTFs) mixed with ground tire rubber (GTR) in linear low-density polyethylene (LLDPE) with and without styrene-ethylene-butylene-styrene-grafted maleic anhydride was studied. In particular, different RTF contents (10, 25, and 50 wt%) and compounding screw speed (110, 180, and 250 r min-1), as well as temperature profiles (extrusion and injection molding) were used to optimize the processing conditions. In this first part, a complete physical and morphological analysis for the RTF fibers and GTR particles was performed. The results show that the compatibilized compounds have lower RTF length and GTR particle size but better distribution of rubber particles in the LLDPE matrix. Overall, lower processing temperatures used in both extrusion and injection molding showed better interfacial adhesion between the components due to higher shear and mechanical energy imparted on the different particles. [ABSTRACT FROM AUTHOR]

In this study, the morphological, physical, and mechanical properties of maple fiber self‐hybrid composites reinforced linear low‐density polyethylene (LLDPE) have been investigated for different concentration (10, 20, and 30%) and ratio (100/0, 75/25, 50/50, 25/75, and 0/100) of short (125–250 μm), medium (250–355 μm), and long (355–500 μm) fibers. Maple surface treatment with a coupling agent (maleated polyethylene, MAPE) was also investigated. The results show that surface treatment increased the tensile modulus and strength, and impact strength. Finally, the self‐hybrid composites gave better properties than single size fibers since a positive deviation from the linear law of mixture was observed, especially at 20% wt. For example, a 75/25 ratio of medium/short or long/short fibers produced a tensile modulus and tensile strength between 13% and 33% higher than composites formulated with a single fiber size. POLYM. COMPOS., 39:4094–4103, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This work reports on the mechanical (tension, flexion, and impact) and physical (density and hardness) properties of polyester recycled tire fibers (RTFs) mixed with ground tire rubber and linear low-density polyethylene with and without styrene-ethylene-butylene-styrene grafted maleic anhydride as a compatibilizer. In particular, the effect of RTF content (10, 25, and 50 wt%), extruder screw speed (110, 180, and 250 r/min), and temperature profiles (extrusion and injection molding) was studied. The results showed that the best properties were obtained at the highest RTF content (50%) and extruder screw speed (250 r/min) combined with the lowest temperature profile in both extrusion and injection molding when the compatibilizer was added. [ABSTRACT FROM AUTHOR]

ABSTRACT: This work reports on the preparation and properties of polydimethylsiloxane (PDMS)/low‐density polyethylene (LDPE) multilayer composite polymer membranes (MCPM) for gas separation applications. The membranes were produced by combining sequential coating with melt‐extrusion/salt leaching techniques. In particular, the gas sorption and permeation properties at different pressure (40–90 psig) and temperature (27–55 °C) are reported with morphology and thermogravimetric properties. The results show that a 20 μm PDMS layer was able to penetrate the microporous LDPE surface layer substrate leading to improved interfacial adhesion. Based on the different gases (CO2, CH4, and C3H8) solubility, permeability, and diffusivity obtained, these membranes are seen as good candidates for industrial gas separations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1045–1052 [ABSTRACT FROM AUTHOR]

A fast and non-invasive near-infrared (NIR) imaging system is proposed to characterize biodegradable polylactic acid (PLA) films containing talc, and produced by extrusion film-blowing for packaging applications. The ultimate goal is to use the system on-line for quality control and after a post-processing thermal treatment (annealing). A set of PLA-talc films with different talc contents (0–3% wt.) were produced and annealed under different conditions. NIR images of the films were collected after which the samples were characterized for their physical, mechanical, and gas barrier properties. Multivariate imaging techniques were then applied on the hyperspectral images. The results showed that the films with various talc loadings can be discriminated, and the information contained in the NIR spectra allowed predicting the annealed film crystallinity and O 2 permeability with good accuracy. [ABSTRACT FROM AUTHOR]

In this work, injection molding was used to produce polylactic acid foams using azodicarbonamide as a chemical foaming agent and to study the effect of wood flour concentration (15, 25, and 40% wt.) on morphology (scanning electron microscopy), density (gas pycnometry), as well as mechanical (tensile, flexural, and impact) and thermal (differential scanning calorimetry) properties. In particular, density reduction was controlled by the amount of material injected (shot size). The results showed that polylactic acid properties increased with wood content, but decreased with density reduction. Nevertheless, specific flexural modulus (per unit weight) always increased with foaming. Foaming was also shown to significantly increase polylactic acid crystallinity. [ABSTRACT FROM AUTHOR]

In this work, a simple method is presented to produce ground tire rubber (GTR) - linear low density polyethylene (LLDPE) compounds and foams via rotational molding. In particular, different GTR concentrations (0 to 50% wt.) were dry-blended with different chemical blowing agent (CBA) content (0 to 1% wt.). From the samples produced, a complete set of characterization was performed in terms of mechanical properties (tensile, flexural and impact), density and morphological properties. The results show that increasing GTR content or CBA content not only decreased both tensile and flexural moduli, but decreased ultimate strength and strain at break. As expected, increasing blowing agent content decreased density. Besides, with respect to impact strength, the value of all samples decreased with the addition of GTR or CBA except for 0.2% wt. CBA of GTR-LLDPE composite foams, which nearly remain at the same level. [ABSTRACT FROM AUTHOR]

Typical preparation of mixed matrix membranes (MMM), where the pre-synthesized polymer and filler are simply mixed together in a suitable solvent before casting, often suffer from poor polymer-filler adhesion. This study introduces a novel generation of MMM where the fillers are covalently linked with the polymer matrix, hence generating defect-free membranes. To do so, a metal-organic framework (MOF) bearing polymerizable groups (UiO-66-NH2) was in-situ linked with a polymer of intrinsic microporosity (PIM-1) during the polymer synthesis. The PIM-MOF chemical cross interface linking was confirmed by combined analytical technics including 1H-NMR, 13C-MAS NMR, FTIR, SEM, XRD and contact angle. Compared with traditional non-crosslinked MMMs, the in-situ derived MMMs showed a significantly higher permeability and ideal selectivity for all the gases tested (CO2, CH4, N2 and O2). These improvements are highly related to the degree of cross interface linking between PIM-1 and UiO-66-NH2. For the same filler loading of 20 wt.%, the CO2/CH4 selectivity increases from 19.1 to 31.9 as the in-situ polymerization time is extended from 12 to 72 h. The physical aging was also effectively controlled for the in-situ crosslinked MMMs where gas permeability remained up to 80% of its initial value after 400 days of storage at ambient conditions. [ABSTRACT FROM AUTHOR]

In this study, short glass fibers (SGF) reinforced acrylonitrile‐butadiene‐styrene (ABS) composites were compounded with different amounts of polyamide 6 (PA6). The composites were produced by twin‐screw extrusion followed by injection molding to study the effect of SGF concentration (0–30 wt%) and PA6/SGF ratio (25 and 50%) on the morphological, mechanical and rheological behavior of these composites. Both composites were mechanically characterized in tensile mode by quasi‐static and dynamic mechanical tests. The morphology of the cro‐fractured surface was analyzed. The quasi‐static tensile tests revealed that the Young's modulus is significantly increased by using Short glass fiber (a gain of 20 and 13%). From all the results obtained, it was concluded that PA6 can act as a coupling agent between SGF and ABS which was confirmed by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and rheological analyses. Although more work is needed to further optimize the properties of these ternary compounds, the results obtained may open new avenues for applications like automotive, sporting goods and electronics. POLYM. COMPOS., 39:14–21, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This work investigated the effect of maple fiber size and content on the auto-hybridization of linear low density polyethylene (LLDPE) composites. The samples were compounded by twin-screw extrusion and molded by compression molding. Different fiber loadings (5 to 20% wt.), fiber sizes (0-425 microns) and size ratios (30/70, 50/50, 70/30 of short, medium, and long fibers) were used to prepare the auto-hybrid composites with 3% of coupling agent (maleated polyethylene). Micrographs and impact strength results showed that the fracture in auto-hybrid composites is mostly dependent on the longer fibers. At 10% wt. the optimum ratio was 30/70 of shorter/longer fibers, which improved tensile strength (20%), tensile modulus (20%), and impact strength (13%) compared with composites with a single fiber size. But at 20% wt., tensile modulus increased by 30% and torsion modulus by 40% above the rule of hybrid mixtures (RoHM) at a 70/30 ratio of shorter/longer fibers. [ABSTRACT FROM AUTHOR]

Polymeric foam applications have rapidly increased over the years and most of them are submitted to cyclic loading conditions. Therefore, their fatigue behavior is highly important to ensure safe operation for which limited information is available compared to compact materials like asphalt, concrete, and metals. Starting with an understanding of the main parameters controlling the mechanical properties of polymer foams, this literature review further presents a broad overview of the information available to understand the relations between loading conditions and fatigue lifetime, including damage level development. The review is composed into three main classes of polymers: thermoplastics, thermosets, and elastomers. The effect of loading conditions, including stress/strain amplitude, loading ratio (R, r), frequency (f), moisture content, type of deformation and temperature (T) is presented and discussed. Finally, the effect of foam morphology in terms of cell size (d) and density (ρ) on the fatigue performance is included to make a link between Paris' law and crack propagation. A conclusion is also provided with openings for future development. [ABSTRACT FROM AUTHOR]

Nanocomposite foams based on Nylon 6 and nanocrystalline cellulose were prepared via extrusion and injection molding to study the effect of nanocrystalline cellulose concentration (0 to 5%), chemical foaming agent content (0, 1%, and 2%), and mold temperature (30℃ and 80℃) on the morphological, physical, and mechanical properties of the samples. Nanocrystalline cellulose content, especially between 1 and 3 wt%, was very effective in reducing the cell size and increasing the cell density of the foam structure. Nanocrystalline cellulose addition (0-5%) was found to increase density (4% for composites and 20% for foams), tensile strength (10% for composite and 13% for foams), tensile modulus (20% for composites and 34% for foams), and flexural modulus (37% for composites and 29% for foams), but decreased the impact strength (35-40% for composites and 20-40% for foams). Foaming agent addition (1%) was able to improve the specific tensile (10%) and flexural (12%) moduli, tensile strength (14%), elongation at break (6%), and impact strength (27%). Finally, higher mold temperature decreased skin thickness and, consequently, decreased the mechanical properties, mostly tensile strength of the foam samples (1% for composites and 18% for foams). [ABSTRACT FROM AUTHOR]

This work presents a simple and efficient method to produce a flat sheet composite membrane (FSCM) with minimum resistance in the support layer. The process is also low cost and uses a limited amount of solvent (water). In particular, a series of polydimethylsiloxane/low-density polyethylene (PDMS/LDPE) FSCM were produced by coating an active PDMS layer on a microporous LDPE support via continuous extrusion and salt leaching (68% wt. NaCl) using immersion in hot water (50 °C). The membranes were then characterized before and after leaching in terms of morphology, porosity, and pore size distribution, as well as thermal properties. The results showed that the microporous structure is highly correlated to the salt used and the amount leached out from the polymer structure. The resulting FSCM were finally used for gas separation of C3H8 from CO2, CH4, N2, and H2 in terms of permeability, solubility, and diffusivity. The results show that for an upstream pressure of 120 psi, the FSCM is about 6, 16, 23, and 53 times more permeable to C3H8 than CO2, CH4, H2, and N2, respectively, confirming the outstanding separation performance of these membranes for industrial applications. [ABSTRACT FROM AUTHOR]

The properties of recycled styrene-butadiene rubber (SBR) blended with virgin polystyrene (PS) have been investigated over a wide range of concentrations (0-94% wt. SBR). The compounds were prepared by twin-screw extrusion followed by injection molding. A pre-treatment in solution (toluene) was also performed to improve the compatibility between the phases. Extraction tests and thermogravimetry were used to determine the amount of PS inserted in the SBR particles. Morphological analysis (SEM) coupled with physical (density and hardness) and mechanical (tension, flexion, torsion and impact) measurements were performed to assess the final behavior of the mixtures. The results show that the proposed treatment can improve the properties, especially at SBR concentrations greater than 50% wt. [ABSTRACT FROM AUTHOR]

In this study, nanocomposites based on Nylon 6 and nanocrystalline cellulose (NCC) were prepared by melt compounding. Then, morphological, thermal, and mechanical properties were analyzed for NCC content between 0 and 7 wt%. Morphological analyses showed different roughness in fractured surface of neat Nylon and its nanocomposites caused by the presence of NCC. Mechanical results showed that the optimum properties were obtained at 3% NCC which could be related to relatively good NCC dispersion at low concentrations with good Nylon-NCC bonding. Overall, flexural (41%) and tensile (23%) moduli, as well as tensile strength (11%) were increased up to 3% of NCC. However, elongation at break and impact strength decreased with NCC addition. Finally, density and hardness showed only a small increase of 5 and 3%, respectively. POLYM. COMPOS., 37:1473-1479, 2016. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Using the beam element to simulate single wall carbon nanotube (SWCNT) and nanocrystalline cellulose (NCC), finite element method is adopted to perform multi-axial numerical tests to compare SWCNT and NCC reinforced polypropylene (PP). As a first step, SWCNT and NCC are assumed to be isotropic and linear elastic materials, while PP is assumed to be linear elastic or elastic-plastic. Using the same reinforcement volume fraction, the elastic and elastic-plastic properties of the nanocomposites are compared under biaxial and triaxial loading conditions. Then, the effect of particle volume fraction and particle size is presented. When NCC and SWCNT have equal particle length and number but different particle diameter, both can produce similar improvement on biaxial mechanical properties. Finally, NCC and SWCNT are compared from an economic point of view to get similar mechanical performance (biaxial properties). The results show that NCC is about 646 times cheaper than SWCNT and is an interesting prospect for future work. [ABSTRACT FROM AUTHOR]

The development of new processing methods is required in order to meet the continuous demand for thinner films with excellent barrier properties for food packaging and other applications. In this study, rice husk organosolv lignin nanoparticles were prepared using the electrospray method, which were applied to produce polylactic acid (PLA)-based films for food packaging. The effect of the following electrospray parameters has been investigated: lignin concentration (LC) ranging from 5–50 mg/mL, flow rate (FR) from 0.5–1 mL/min, applied voltage from 10–30 kV, and tip-to-collector distance (TCD) from 10–25 cm, on the morphology, size, polydispersity index (PDI), and Zeta potential (ZP) of lignin nanoparticles (LNPs). The response surface methodology with a Box-Behnken design was applied to optimize these parameters, while dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses were used to characterize the controlled LNPs. The results showed that the LNPs shape and sizes represent a balance between the solvent evaporation, LC, applied voltage, TCD and FR. The application of optimal electrospray conditions resulted in the production of LNPs with a spherical shape and a minimal size of 260 ± 10 nm, a PDI of 0.257 ± 0.02, and a ZP of −35.2 ± 4.1 mV. The optimal conditions were achieved at LC = 49.1 mg/mL and FR = 0.5 mL/h under an applied voltage of 25.4 kV and TCD = 22 cm. Then, the optimized LNPs were used to improve the properties of PLA-based films. Three types of PLA-lignin blend films were casted, namely lignin/PLA, LNPs/PLA and PLA-grafted LNPs. PLA-grafted LNPs exhibited a more uniform dispersion in PLA for lignin contents of up to 10% than other composite samples. Increasing the lignin content from 5% to 10% in PLA-grafted LNPs resulted in a significant increase in elongation at break (up to four times higher than neat PLA). The presence of PLA-grafted lignin led to a substantial reduction in optical transmittance in the UV range, dropping from 58.7 ± 3.0% to 1.10 ± 0.01%, while maintaining excellent transparency to visible light compared to blends containing lignin or LNPs. Although the antioxidant capacity of unmodified lignin is well-known, a substantial increase in antioxidant capacity was observed in LNPs and PLA-grafted LNP films, with values exceeding 10 times and 12 times that of neat PLA, respectively. These results confirm the significant potential of using studied films in food packaging applications. [ABSTRACT FROM AUTHOR]

Using beam and tetrahedron elements to simulate nanocrystalline cellulose (NCC), single wall carbon nanotube (SWCNT) and polypropylene (PP), finite element method (FEM) is used to predict the mechanical properties of nano-composites. The bending, shear and torsion behaviors of nano-composites are especially investigated due to the limited amount of information in the present literature. First, mixed method (MM) and FEM are used to compare the bending stiffness of NCC/PP and SWCNT/PP composites. Second, based on mechanics of materials, the shear moduli of both types of nano-composites are obtained. Finally, fixing the number of fibers and for different volume contents, four NCC lengths are used to determine the mechanical properties of the composites. The bending and shearing performances are also compared between NCC and SWCNT based composites. In all cases, the elastic–plastic analyses are carried out and the stress or strain distributions for specific regions are also investigated. From all the results obtained, an economic analysis shows that NCC is more interesting than SWCNT to reinforce PP. [ABSTRACT FROM AUTHOR]

The potential and effectiveness of near-infrared (NIR) hyperspectral imaging was investigated for rapid and nondestructive spectral-spatial inspection of functional multilayer films. A series of film samples having different combinations of layers were used to demonstrate the sensor performance. Multivariate Image Analysis (MIA) was applied to NIR hyperspectral images of unprinted multilayer films with different compositions to distinguish them regarding absence/presence of particular layers. Since printing of commercial brands on the films may interfere with product inspection, the ability of MIA to detect the presence of the functional layer (barrier) in spite of film surface printing was also assessed. The results show that the proposed MIA approach is successful at classifying multilayer films, even in the presence of printing. [ABSTRACT FROM AUTHOR]

Blends of maleated polypropylene (MAPP) with high contents of waste rubber powder, namely ground tire rubber and waste ethylene propylene diene monomer (EPDM) powder, were used as impact modifiers for polypropylene (PP) based composites with different reinforcements (hemp, talc, and milled glass fiber). Adding reinforcements led to increase in modulus (tensile, flexural, and torsion moduli) of PP, while its impact strength decreased noticeably. Impact modification of PP-based composites was successfully performed via inclusion of MAPP/waste rubber compounds, especially compounds containing waste EPDM powder. Inclusion of such impact modifiers increased impact strength of composites over 80%. The effects of impact modification were more significant for hemp- and glass-filled composites compared to composites containing talc. However, slight decrease in tensile, flexural, and torsion moduli (up to 30%) of the composites was also observed after inclusion of impact modifiers. POLYM. COMPOS., 35:2280-2289, 2014. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The effect of particle characteristics such as size and shape on the reinforcing efficiency of nano-particles is investigated. Nanocomposites based on ethylene vinyl acetate (EVA) copolymer containing five different nano-particles including clay, multiwall carbon nanotube (CNT), CaCO3, talc, and nano-crystalline cellulose (NCC) were produced. The analyses are performed in the melt and solid states. The highest property changes were obtained for clay and CNT, followed by talc, NCC, and CaCO3. By using morphological analyses, mechanical properties, and rheological data, the results were correlated to the amount of available surface area between the particles and polymer. Finally, the particles were compared using a material cost over mechanical performance ratio where the optimum was obtained for talc followed by clay, NCC, CNT and CaCO3. [ABSTRACT FROM AUTHOR]

In this work, different concentrations (0, 35, 50 and 65%wt.) of recycled rubber (ethylene-propylene diene, EPDM) were blended with virgin polypropylene (PP) to produce thermoplastic elastomer resins via twin-screw extrusion. Then, the samples were pelletized and foamed by injection molding using a chemical blowing agent (azodicarbonamide, ADC). In particular, the molding process was optimized to determine the effect of processing parameters like blowing agent content, mold temperature, and injection conditions (pressure, velocity, etc.). From the samples obtained, a complete morphological (skin thickness, cell size and cell density) and mechanical characterization was performed including density and hardness. The results obtained showed that it is more difficult to produce a good foam structure with increasing recycled rubber content. [ABSTRACT FROM AUTHOR]

[Display omitted] • Water cement ratio affects mechanical strength of cement based composites. • Relationships between mechanical strength and the curing age are investigated. • Weibull parameters of strengths at the curing age of 28 days are estimated. • Proportional coefficients between flexural and compressive strength are determined. In this work, the effect of multiwall carbon nanotube (MWCNT) content (0.05 to 0.70 wt%) on the flexural and compressive strengths of cement-based composites was investigated as a function of time. Using linear regression analyses, relationships between the mechanical strengths and the curing time were proposed and discussed. The results showed different trends before (short time) and after (long time) 28 days. In particular, the values at 28 days were found to follow a Weibull distribution function and the corresponding parameters were compared and discussed. Relationships between the flexural and compressive strengths are also proposed and compared with the European design code. Finally, the effect of the water/cement ratio is discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] SWCNT orientation has significant effect on mechanical properties for angle less than 30°. [•] SWCNT content has significant effect on mechanical properties for volume fraction higher than 1%. [•] With increasing strain rate, nano-composites can undertake more stresses. [•] The shear stresses at the interface are higher in SWCNT than in polypropylene. [•] In general, with increasing SWCNT content, the shear stress at particle midpoint decreases. [ABSTRACT FROM AUTHOR]