Characterization of composite materials based on LDPE loaded with agricultural tunisian waste

This study investigated the use of an available agricultural Tunisian vine stem waste as a filler material. Composites of green materials were prepared using vine stems as filler and low density polyethylene (LDPE) as a matrix. A series of composite films was prepared by different loadings of the vine stem waste with 10–50% of the filler in 10% intervals. The ensuing materials were characterized by several techniques. The morphology of the composites was investigated using scanning electron microscopy (SEM). The thermal and mechanical properties were studied using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), respectively. The results indicated that vine‐stem based particles enhanced the thermo‐mechanical properties of the thermoplastic matrix and demonstrated that this available lignocellulosic biomass of vine stems can be considered to be a promising filler material. However, the obtained result of water absorption indicated that the maximum limit of the filler content should not exceed 30% of vine stems. POLYM. COMPOS., 36:817–824, 2015. © 2014 Society of Plastics Engineers     

Valorization of waste thermoset material as a filler in thermoplastic: Mechanical properties of phenolic molding compound waste‐filled PP composites

As most thermoset material, phenolic molding compound (PMC) wastes are an environmental problem. Very few recycling solutions have been proposed so far for this type of material. A mechanical recycling method to valorize these materials is proposed in this work. It relies on the use of phenolic waste as filler in thermoplastic. Such phenolic filler can increase mechanical properties (tensile, flexural) of the matrix, and be used in substitution of traditional particulate fillers such as calcium carbonate or talc. In this study, several morphological parameters influencing the final mechanical properties of a PMC‐filled polypropylene (PP) micro‐composite are studied, such as filler loading rate, particles size distribution of the filler, and interfacial adhesion between the filler and the matrix. Some structural parameters are also studied and linked with mechanical properties, such as dispersion of the filler and crystallinity of the matrix. Finally, the properties of PMC‐filled PP are compared with CaCO₃‐ and talc‐filled PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45849.     

Effect of different fillers on physical,mechanical, and optical properties of styrenic‐based thermoplastic elastomers

The effects of different fillers on physical, mechanical, and optical properties of styrenic‐based thermoplastic elastomers were investigated by experimental study. Poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] block copolymer (SEBS)‐based thermoplastic elastomer composites were prepared in a co‐rotating intermeshing twin‐screw extruder, using silica and calcite as filler materials with three different particle sizes. The loading ratios in the composites were varied. Hardness, density, tensile strength, tear strength, compression set, wear resistance, transmittance, and haze measurements were performed. Thermal properties and morphological structure were investigated by differential scanning calorimeter (DSC) and scanning electron microscopy (SEM), respectively. The results show that, an interaction between silica and the polymer matrix exists, whereas calcite does not show any interaction with the polymer. Therefore, it is concluded that, calcium carbonate can be used in the composite as filler for cost efficiency, whereas silica can be used as reinforcing material in SEBS‐based thermoplastic elastomer composites, when optical properties are also concerned. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effect of surface treatment on the physicomechanical and thermal properties of high‐density polyethylene/olive husk flour composites

In this study, a particular interest was focused on the recovery of lignocellulosic waste of olive husk flour (OHF) by its incorporation as filler in manufacturing composite materials based on high‐density polyethylene (HDPE) matrix with various filler contents (10, 20, and 30 wt %). The problem of incompatibility between the hydrophilic filler and the hydrophobic matrix was treated with two methods: the first method consists of using maleic anhydride‐grafted polyethylene (MAPE) as compatibilizer in HDPE/OHF composites. The second method, was focused on the chemical modification of OHF by vinyl‐triacetoxy‐silane (VTAS). Fourier transform infrared spectroscopy is used to analyze both grafting and silanization reactions involved. Scanning electron microscopy was used to show the morphology of the flour surface. Furthermore, the physicomechanical and thermal characteristics of the various composite samples were investigated as a function of filler contents and treatment types. The results showed that the properties of the composite materials are positively affected by the silanization treatment of OHF and also by MAPE addition. However, better mechanical and thermal properties with less moisture absorption were obtained for the composite materials compatibilized with MAPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Elastic moduli of particulate composites with graded filler‐matrix interfaces

The elastic response of plane‐array models of composites reinforced by particles or aligned fibers having graded interfaces with the matrix is analyzed. Such microstructure is representative of a new class of polymer matrix composite materials in which the filler is nanometer‐sized. In such materials, the polymer chains in the matrix are preferentially oriented close to the interface with the relatively rigid fillers, this leading to a graded interfacial layer about each inclusion. The composite elastic moduli are determined based on the properties and geometry of the interfacial graded layer as well as on the moduli of the filler and the matrix, and the volume fraction of filler. Conversion curves are constructed allowing for an equivalence to be established between the present case and that of similar composites without graded interfaces. Based on these conversion curves, standard homogenization algorithms can be applied to determine the overall elastic properties of such composite. The fillers are considered to be stiffer than the matrix, both rigid and of finite stiffness. Results for both sliding and bonded interfaces are presented. The effect of anisotropic material properties in the graded region on the composite moduli is also investigated. The results of the model are compared with published experimental data.     

Electrical and Mechanical Properties of Thermoplastic Polyurethane and Polytetrafluoroethylene Powder Composites

To determine the possibility of using polytetrafluoroethylene (PTFE) powder as reinforcing filler in the thermoplastic matrix, the thermoplastic polyurethane (TPU) as the matrix and PTFE powder as reinforcing filler were used to prepare a particulate reinforced composite, in order to determine testing data for electrical and mechanical properties of the composites according to the filler loading in respect to TPU polymer matrix. The TPU and PTFE powder composites were prepared by the milling TPU with 2.5, 5, 7.5, and 10 wt% of PTFE powder in a two roll mill and the milled material is compression moulded to make sheets. From the sheets, the test specimens were made and tested for electrical properties—dielectric strength, dielectric constant, surface, and volume resistivity; fire resistance—rate of burning; mechanical properties—tensile strength and elongation, impact strength, hardness; density and melt flow index. The incorporation of PTFE powder has significantly improved the electrical properties—dielectric strength, dielectric constant, surface and volume resistivity; and fire resistance—rate of burning of thermoplastic polyurethane. However, the tensile strength decreased from 24.91 to 14.71 MPa and tensile elongation increased from 620 to 772 percentage.     

Electrical conductivity and rheology of carbon‐filled liquid crystal polymer composites

One emerging market for electrically conductive resins is for bipolar plates for use in fuel cells. Adding carbon fillers to thermoplastic resins increases composite electrical conductivity and viscosity. Current technology often adds as much of a single type of carbon filler as possible to achieve the desired conductivity, while still allowing the carbon‐filled thermoplastic matrix material to be extruded and molded into a bipolar plate. In this study, varying amounts of two different types of carbon, one carbon black and one synthetic graphite, were added to Vectra A950RX liquid crystal polymer. The resulting single filler composites were then tested for electrical conductivity and rheological properties. The electrical conductivity followed that typically seen in polymer composites with a percolation threshold at 4 vol % for carbon black and at 15 vol % for synthetic graphite. Over the range of shear rates studied, the viscosity followed a shear‐thinning power law model with power‐law exponent (n ? 1) = ?0.5 for neat Vectra A950RX and (n ? 1) = ?0.7 for highly filled composite materials. Viscosity increased with increasing filler volume fraction for all shear rates. The viscosity–enhancement effect was more rapid for the composites containing carbon black when compared with those containing synthetic graphite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2680–2688, 2006     

Inverse gas chromatography for the determination of the dispersive surface free energy and acid–base interactions of a sheet molding compound. I. Matrix material and glass

Sheet molding compound is a material composed of a polyester thermosetting matrix with a thermoplastic, an inorganic filler, a metal oxide, reinforcement fibers, and material performance enhancers embedded in the crosslinked matrix. To achieve the optimum mechanical properties required for the composite material, the surface free energy of the polyester composite needs to be understood. In this study, the composite matrix and glass reinforcement fibers are compared with respect to their surface free energy and acid–base characteristics on the basis of inverse gas chromatography measurements. The inverse gas chromatography results for the matrix and glass are compared to previous results found for sized and unsized cellulosic fibers. The inverse gas chromatography data are used to assess chemical modifications performed on the biobased fibers to predict improvements in the fiber/matrix interaction, and this provides inferences on the overall composite cohesion. Our results show first that any fiber reinforcement system for the polyester composite material has to be acidic to promote good adhesion as the matrix system is very basic and second that the individual dispersive surface energies of the components of the matrix interact in a weighted average to determine the overall surface energy of the composite. Also, a commercial glass reinforcement sized for polyester has been found to have a lower interaction parameter than literature values for cellulosic fibers. This finding suggests that cellulosic fibers might have an advantage in competing with a conventional glass‐fiber reinforcement system in fiber/matrix bonding for sheet molding compound composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Lignocellulosic Flour from Cladodes of Opuntia ficus‐indica Reinforced Poly(propylene) Composites

Summary: A lignocellulosic flour was obtained by grinding dried cladodes of Opuntia ficus‐indica. It was used as low cost natural filler in PP and the effect of the treatment of the filler with MAPP was also investigated. The morphology and thermal properties of these composites were evaluated by SEM and DSC, respectively. MAPP coating resulted in a better adhesion between the filler and the matrix and higher homogeneity of the material. A decrease of the degree of crystallinity of the PP matrix in presence of the untreated filler was observed. Dynamic mechanical analysis and tensile properties were also studied. High‐strain tensile properties display enhanced mechanical properties for MAPP treated‐based composites only. When conditioned in highly moist atmosphere (98% RH), both the water uptake and water diffusion coefficient decrease when the filler was treated. These effects were ascribed to the promoting interfacial adhesion induced by the coating treatment. In liquid water, this increased adhesion between the filler and the matrix results in a higher weight loss of the material. It is due to the removal of the grafted polymer from the material during the dissolution of part of the filler.

SEMs of freshly fractured surface for a PP film filled with 10 wt.‐% of MAPP treated OFI cladode (top) and calcium oxalate crystallite within the PP matrix for a 3 wt.‐% filled composite (bottom).     

Lignin nanoparticles by ultrasonication and their incorporation in waterborne polymer nanocomposites

Lignin nanoparticles (nanolignin, NL) were prepared in this work by ultrasonic treatment of softwood kraft lignin to obtain lignin‐water dispersions with excellent colloidal stability. A thorough characterization of the chemical, physical, and morphological properties of the new NL particles allowed for direct comparisons with the untreated parent material. Such NL particles were incorporated into a waterborne thermoplastic polyurethane matrix at different concentrations to yield bio‐based nanocomposite materials. The effect of the bio‐filler type (NL vs. untreated lignin) and loading on the chemical, physical, thermal, and morphological characteristics of the resulting nanocomposites was extensively investigated. In addition, tensile tests carried out on these systems highlighted the superior mechanical properties of NL‐based nanocomposites compared to composite materials incorporating untreated lignin. The results of this study provide a direct demonstration of an easy and environmentally friendly approach to obtain waterborne polyurethane‐based nanocomposites reinforced with NL in a relatively straightforward and accessible way and clearly evidence the potential of lignin nanoparticles as fully bioderived fillers for advanced nanocomposite applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45318.     

Mechanical behavior of cold plasma–treated sisal and high‐density polyethylene composites

Sisal fibers and finely powdered high‐density polyethylene were surface functionalized with dichlorosilane on a RF(radio frequency)‐plasma reactor. Composites made from sisal and high‐density polyethylene were compounded using a thermokinetic mixer. The discharged mass was cooled, granulated, and injected molded into composite specimens for testing. The mechanical behaviors (tensile, impact and thermal dynamical mechanical properties) of composites made from cold plasma‐treated and untreated components are compared and discussed. The best mechanical performance was generally obtained for composites where only the inert thermoplastic matrix was plasma‐functionalized. Plasma treatment of lignocellulosic fibers seems to induce decomposition processes of the surface layers structures exposed to the plasma that generally does not contribute to significant improvement on the mechanical behavior of the composite.     

High dielectric constant SU8 composite photoresist for embedded capacitors

A novel, photodefinable, high dielectric constant (high‐k) nanocomposite material was developed for embedded capacitor applications. It consists of SU8 as the polymer matrix and barium titanate (BT) nanoparticles as the filler. The UV absorption characteristics of BT nanoparticles were studied with a UV‐Vis spectrophotometer. The effects of BT nanoparticle size, filler loading, and UV irradiation dose on SU8 photopolymerization were systematically investigated. The dielectric properties of the photodefined SU8 nanocomposites were characterized. Embedded capacitors using the novel high dielectric constant SU8 composite photoresist were demonstrated on a flexible polyimide substrate by the UV lithography method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1523–1528, 2007     

Weatherability of conventional and nanocomposites of LDPE and Zinc Oxide

LDPE thermoplastic composites prepared using 1–4 wt% of conventional filler‐grade ZnO and nanoscale ZnO were investigated to determine whether the presence of either grade of filler affected the weatherability of the composite material. Outdoor exposure (natural weathering) studies and accelerated weathering was performed and tensile properties were used to assess the weather‐induced damage. Weatherability under outdoor exposure and under laboratory‐ accelerated conditions, primarily quantified using tensile properties, were found to be the same for composites with conventional and nanoscale ZnO filler. POLYM. COMPOS., 38:341–348, 2017. © 2015 Society of Plastics Engineers     

Effect of viscosity on the electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture

The viscosity of thermoplastics above T_g was found to greatly affect the room temperature electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture, while the mechanical properties are essentially not affected. The electrical resistivity decreased and the electromagnetic interference shielding effectiveness increased with increasing viscosity, as shown by using (i) the same filler, namely nickel particles, in polyimidesiloxane and polyether sulfone, and (ii) the same filler and matrix at different composite molding temperatures. This effect is attributed to the flow of the low viscosity thermoplastic particles during composite fabrication tending to disturb the connectivity of the filler particles achieved prior to heating.     

Biodegradability,mechanical, and thermal properties of thermoplastic starch/cuttlebone composites

This work focused on improvements to the properties of thermoplastic starch (TPS) by using cuttlebone (CB) as the bio‐filler. The effect of CB on the properties of TPS was compared to that of commercial calcium carbonate (CC). The good adhesion achieved between the TPS matrix and the cuttlebone powder produced improvements in the tensile strength of their composites, whereas the tensile strength of TPS/CC composite was lower due to the presence of filler agglomerates. The biodegradation of the TPS and the composites were analyzed by the soil burial test. This showed that cuttlebone decreased the biodegradation rate. The thermal degradation temperatures of TPS, a TPS/CC composite and a TPS/CB composite showed very similar behavior. POLYM. COMPOS., 36:1401–1406, 2015. © 2014 Society of Plastics Engineers     

Lignocellulosic flour‐reinforced poly(hydroxybutyrate‐co‐valerate) composites

Residual lignocellulosic flour from spruce and ground olive stone was used as a natural filler in poly(hydroxybutyrate‐co‐valerate) (PHBV)‐based composites. The morphology and the thermal properties of these composites were investigated by scanning electron microscopy and differential scanning calorimetry, respectively. Lignocellulosic fillers acted as nucleating sites for the crystallization of PHBV and strongly enhanced its degree of crystallinity. Dynamic mechanical analysis and tensile properties of these materials were also studied. A significant reinforcing effect was displayed by dynamic mechanical analysis at temperatures higher than the glass–rubber transition of the matrix. In addition, for low‐particle‐size spruce, a stabilization of the modulus was observed up to 500 K. High‐strain tensile properties did not show any reinforcing effect. This apparent disagreement was explained by the poor adhesion between the hydrophilic lignocellulosic filler and the hydrophobic polymeric matrix. To validate this hypothesis, the experimental data were compared with predicted data involving the percolation concept. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1302–1315, 2003     

POLYSTYRENE-BENZOYLATED EFB REINFORCED COMPOSITES

Reinforced thermoplastics generally are produced by incorporation of reinforcement agents or fillers into thermoplastic resins. The utilization of lignocellulosic material as filler with reinforcement in polymer matrix has received much interest due to its lower price and other properties. A composite of polystyrene reinforced with oil palm empty fruit bunches (EFB) and chemically treated EFB with benzoyl chloride (EFB-benzoylated) as a function of loading and fiber surface modification were prepared. The chemically treated fibers were analyzed with FT-IR to observe the extent of chemical reaction with EFB fiber. The sharp peak at 710 cm^?1 appeared on the spectra, which indicated that the mono-substituted benzene ring has taken place. The strong peak at 1720 cm^?1 has indicated the presence of ester group treated fiber. The flexural test was performed using Instron 4301 testing machine to study flexural properties of the composites with various fiber sizes. The results showed that the flexural properties increased with particle size. The flexural strength of EFB-benzoylated composites was observed to be stronger than untreated EFB fiber. Scanning electron microscope was used to investigate the morphological structure of the fiber surface, fiber pull out, fracture surface, and fiber–matrix interface. The untreated EFB composites showed hole and fiber end, which indicated that most of the fiber have pulled out breaking during the fracture of composites; however, the treated EFB-benzoylated showed a good adhesion between fiber and matrix.     

Polypropylene cellulose‐based composites: The effect of bagasse reinforcement and polybutadiene isocyanate treatment on the mechanical properties

Using bagasse fiber as the reinforcing filler and polypropylene as the thermoplastic matrix polymer, a reinforced composite was prepared, and its mechanical properties examined as a function of the amount of compatibilizing agents used. In the sample preparation, four levels of fiber loading (10, 20, 30, and 40 wt %), three levels of polybutadiene isocyanate (PBNCO) content (0, 2, and 4 wt %) and two levels of maleated polypropylenes (MAPP) content (0 and 3 wt %) as compatibilizing agents were used. The tensile properties of the composites improved as the fiber loading and the compatibilizing agents increased, but the impact strength was significantly decreased. The mechanical study revealed that the positive effect of compatibilizing agents on interfacial bonding. The composites treated with PBNCO showed superior tensile and impact properties than those without treatment. The findings indicated that bagasse as agro‐waste material is a valuable renewable natural resource for composite production and could be utilized as a substitute for wood in composite industries. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrical conductivity and rheology of carbon fiber/liquid crystal polymer composites

One emerging market for electrically conductive resins is for bipolar plates for use in fuel cells. Adding carbon fillers to thermoplastic resins increases composite electrical conductivity and viscosity. Current technology often adds as much of a single type of carbon filler as possible to achieve the desired conductivity, while still allowing the material to be extruded and molded into a bipolar plate. In this study, varying amounts of two different types of polyacrylonitrile (PAN) based carbon fiber (Fortafil 243 and Panex 30) were added to Vectra A950RX liquid crystal polymer. The resulting single fiber composites were then tested for electrical conductivity and rheological properties. The electrical conductivity followed the behavior typically seen in composites with a percolation threshold at 5 vol% for Fortafil 243 and at 13 vol% for Panex 30. Viscosity increased with increasing filler volume fraction for all shear rates, but was more rapid for the Fortafil 243 composites. Over the range of shear rates studied, the viscosity followed a shear‐thinning power law model with power‐law exponent (n – 1) = –0.5 for neat Vectra A950RX. Panex 30 had no effect on the power‐law exponent and Fortafil 243 changed (n – 1) to −0.6. POLYM. COMPOS., 28:168–174, 2007. © 2007 Society of Plastics Engineers     

High performance wood composites from highly filled polybenzoxazine

Highly filled systems prepared by compression molding of Hevea brasiliensis woodflour filled polybenzoxazine composites with high mechanical properties and reduced water uptake has been developed. The effects of percent filler content and particle size of woodflour on the obtained composite's properties were examined. The low melt viscosity of BA‐a type polybenzoxazine allows substantial amount of woodflour to be easily incorporated into the composites. The results showed that mechanical properties from dynamic mechanical analysis and flexural test at filler content below the optimum filler packing show approximately linear relationship with filler loading. The outstanding compatibility between the woodflour and the polybenzoxazine matrix is evidently seen from the large improvement in the composite's T_g and char yield. Scanning electron micrographs of the composite also reveals substantially strong interface between the woodflour filler and the polybenzoxazine matrix. Water absorption of the composites is greatly reduced with increasing the amount of polybenzoxazine due to the inherent low water absorption of the matrix. The polybenzoxazine is; therefore, a highly attractive candidate as high performance lignocellulosic binder or adhesive and other related applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1240–1253, 2006