Flame-retarded biocomposites of poly(lactic acid), distiller’s dried grains with solubles and resorcinol di(phenyl phosphate)

The distiller’s dried grains with solubles (DDGS) were treated by smashing and water washing processes. The treatment effects on DDGS were analyzed, and the results showed that the thermal stability and the hydrophobicity of DDGS were improved by the treatment processes. The flame retarded biocomposites of poly(lactic acid) (PLA) with DDGS and degradable polymeric flame retardant resorcinol di(phenyl phosphate) (RDP) were prepared. The prepared biocomposites had good mechanical properties and the tensile strength of the biocomposite containing 15 wt% RDP and 15 wt% DDGS reached approximately 53 MPa. Meanwhile, using the limited oxygen index (LOI) and the underwriters laboratory (UL-94) tests, for the biocomposite, the LOI value was approximately 27.5% and V-0 rating in UL-94 was attained. Furthermore, the peak heat release rate of this biocomposite was reduced to 275 kW/m² compared with 310 kW/m² for pure PLA. After burning of the biocomposites, compact and coherent charred layer was formed and the char residues were analyzed in detail.     

Mechanical,thermal and morphological properties of durian skin fibre reinforced PLA biocomposites

Durian skin waste generated by durian fruit or Durio zibethinus Murray show potential as a new reinforcement based-natural fibre. Similar to other lignocellulosic fibre, durian skin fibre (DSF) is capable in reinforcing polylactic acid (PLA) through extrusion and injection moulding processes for various applications. In current study, the effects of fibre content and pre-treatment using 4% sodium hydroxide (NaOH) on DSF were investigated on impact and thermal properties of PLA biocomposites. Treated DSF significantly enhanced the properties of PLA biocomposites as compared to untreated biocomposite. PLA can be replaced by 30 wt% DSF for similar impact performance. Thermogravimetry analysis (TGA) demonstrated that pre-treated DSF improved the thermal stability of PLA biocomposite. Differential scanning calorimetry (DSC) showed the presence of pre-treated DSF minimally enhanced the glass transition temperature (T_g), crystallization temperature (T_c) and melting temperature (T_m) relative to untreated DSF which suggests on better reinforcement with NaOH pre-treatment.     

Thermal and dynamic mechanical properties of grafted kenaf filled poly (vinyl chloride)/ethylene vinyl acetate composites

The effects of kenaf and poly (methyl methacrylate grafted kenaf on the thermal and dynamic mechanical properties of poly (vinyl chloride), PVC and ethylene vinyl acetate, EVA blends were investigated. The PVC/EVA/kenaf composites were prepared by mixing the grafted and ungrafted kenaf fiber and PVC/EVA blend using HAAKE Rheomixer at a temperature of 150 °C and the rotor speed at 50 rpm for 20 min. The composites were subjected to Differential Scanning Calorimetric (DSC), Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) and Scanning Electron Microscopy (SEM) studies. The DSC data revealed that the crystallinity of the EVA decreased with the addition of 30% grafted and ungrafted kenaf fibers. TGA and derivative thermogravimetric (DTG) curves displayed an increase in the thermal stability of the composites upon grafting of the fiber. Studies on DMA indicate that the T_g of the PVC and EVA in the PVC/EVA/kenaf composites has been shifted to higher temperature with the addition of the kenaf fiber. The presence of PMMA on the surface of grafted kenaf fiber was further confirmed by the analytical results from FTIR. The morphology of fractured surfaces of the composites, which was examined by a scanning electron microscope, showed the adhesion between the kenaf fiber and the PVC/EVA matrix was improved upon grafting of the kenaf fiber.     

The effect of alkaline treatment on mechanical properties of kenaf fibers and their epoxy composites

In this work, kenaf fibers were pre-treated in a NaOH solution (6% in weight) at room temperature for two different periods (48 and 144 h). The chemical treatment of kenaf fibers for 48 h allowed to clean their surface removing each impurity whereas 144 h of immersion time had detrimental effect on the fibers surface and, consequently, on their mechanical properties.Untreated and NaOH treated kenaf fibers (i.e. for 48 h) were also used as reinforcing agent of epoxy resin composites. The effect of the stacking sequence (i.e. using unidirectional long fibers or randomly oriented short fibers) and the chemical treatment on the static mechanical properties was evaluated showing that the composites exhibit higher moduli in comparison to the neat resin. As regards the strength properties, only the composites reinforced with unidirectional layers show higher strength than the neat resin. Moreover, the alkali treatment increased the mechanical properties of the composites, due to the improvement of fiber–matrix compatibility.The dynamic mechanical analysis showed that the storage and the loss moduli are mainly influenced by the alkali treatment above the glass transition temperature. Moreover, the alkali treatment led to a notable reduction of tan δ peaks in addition to significant shifts of tan δ peaks to higher temperatures whereas the stacking sequence did not influence the trends of storage modulus, loss modulus and damping of the composites.     

The effect of alkaline and silane treatments on mechanical properties and breakage of sisal fibers and poly(lactic acid)/sisal fiber composites

The main goals of this work were to study the effect of different chemical treatments on sisal fiber bundles tensile properties as well as on tensile properties of composites based on poly(lactic acid) (PLA) matrix and sisal fibers. For this purpose, sisal fibers were treated with different chemical treatments. After treating sisal fibers the tensile strength values decreased respect to untreated fiber ones, especially when the combination of NaOH + silane treatment was used. Taking into account fiber tensile properties and fiber/PLA adhesion values, composites based on silane treated fibers would show the highest tensile strength value. However, composites based on alkali treated and NaOH + silane treated fibers showed the highest tensile strength values. Finally, experimental tensile strength values of composites were compared with those values obtained using micromechanical models.     

Mechanical properties of poly(butylene succinate) (PBS) biocomposites reinforced with surface modified jute fibre

A biocomposite was originally fabricated with biodegradable polymer PBS and jute fibre, and the effects of fibre surface modification on characteristics of jute fibre and mechanical properties of the biocomposite were evaluated in this paper. The experimental results show that surface modification can remove surface impurities and reduce diameter of jute fibres. Regarding the mechanical properties of biocomposites, it is observed that the biocomposites with jute fibres treated by 2% NaOH, 2 + 5% NaOH or coupling agent, respectively, an optimum in mechanical properties can obtain at fibre content of 20 wt.%, which exhibit an obvious enhancement in mechanical strength and modulus compared to the ones with untreated jute fibre. Furthermore, surface modification also exhibits less effects on flexural properties compared to tensile properties and more on flexural or tensile modulus than on the strength.     

Characterization of untreated and treated male and female date palm leaves

This paper describes the characterization of male and female date palm leaves from two different cultivars, Sheshi female and unknown male leaves. Characterization was done for both untreated and NaOH treated date palm leaves by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopic techniques. To our knowledge, the difference in specious reaction to the treatment type of date palm fiber has not been investigated earlier. These leaves were treated with different concentrations of NaOH, 0.5%, 1%, 2% and 5% (w/w). The results from this investigation indicate that female leaves have better tensile properties which deteriorate with the increase of the alkali. The male leaves have lower tensile properties than female leaves and their mechanical properties are improved slightly by NaOH treatment. Female leaves have more pores than male leaves, this was proved and calculated by image analysis. Untreated female leaves have higher thermal stability (353 °C) than male leaves (343 °C). Both can be used as reinforcements in thermoplastic matrix materials whose processing temperatures are below 300 °C.     

Chemical treatment of sisal fiber using alkali and clay method

In this study the chemical treatment of sisal fiber using the combined alkali (NaOH) and clay is discussed. The purpose of this fiber treatment is to improve the fiber–matrix compatibility, interface strength, mechanical, thermal and water barrier properties. The phase change due to chemical treatment of raw sisal fiber was examined by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) methods. The result shows the presence of about 20 wt.% clays in NaOH–clay treated sisal fiber with 2.6× reduced water uptake and also with improved mechanical and thermal properties. Subsequently the treated and untreated fibers were reinforced in polypropylene (PP) matrix and the mechanical and thermal properties were examined. The result indicates that the fiber–matrix interface strength, adhesion, glass transition temperature and tensile properties of composites were improved in NaOH–clay treated fiber composites.     

Innovative flax tapes reinforced Acrodur biocomposites: A new alternative for automotive applications

Flax Acrodur biocomposites are elaborated with an innovative flax reinforcement consisting of long technical fibers unidirectionally arranged without any weft and twist. The fibers cohesion is performed by using a new process consisting by reactivating the pectin cement. A polyester thermoset matrix (Acrodur) is used to impregnate the flax reinforcement and to produce unidirectional (UD) laminates. The relationship between the main process variables (drying, fibers content, densification and curing parameters) and the properties of the biocomposites is investigated. The optimized biocomposites have an elastic modulus of 18 ± 1 GPa with 55% wt.% flax fiber content and a low density of 0.93 g/cm³. The thermal stability of the developed biocomposites is also investigated by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). DMA results show a slight change of the storage modulus in a range of temperature from 23 °C to 160 °C. The appropriate processing parameters for the biocomposites are established. The developed flax tapes reinforced Acrodur biocomposites have a potential to be integrated for automotive applications thanks to their high stiffness/weight ratio and environmental advantages.     

Strong and optically transparent biocomposites reinforced with cellulose nanofibers isolated from peanut shell

Cellulose nanofibers–reinforced PVA biocomposites were prepared from peanut shell by chemical–mechanical treatments and impregnation method. The composite films were optically transparent and flexible, showed high mechanical and thermal properties. FE-SEM images showed that the isolated fibrous fragments had highly uniform diameters in the range of 15–50 nm and formed fine network structure, which is a guarantee of the transparency of biocomposites. Compared to that of pure PVA resin, the modulus and tensile strength of prepared nanocomposites increased from 0.6 GPa to 6.0 GPa and from 31 MPa to 125 MPa respectively with the fiber content as high as 80 wt%, while the light transmission of the composite only decreased 7% at a 600 nm wavelength. Furthermore, the composites exhibited excellent thermal properties with CTE as low as 19.1 ppm/K. These favorable properties indicated the high reinforcing efficiency of the cellulose nanofibers isolated from peanut shell in PVA composites.     

Multi-scale hybrid biocomposite: Processing and mechanical characterization of bamboo fiber reinforced PLA with microfibrillated cellulose

In this research we develop novel hybrid biocomposites based upon a biodegradable poly(lactic acid) (PLA) matrix reinforced with microfibrillated cellulose (MFC) and bamboo fiber bundles. Due to the relative difference in scale between microfibrillated cellulose and bamboo, a hierarchy of reinforcement is created where bamboo fiber bundles are the primary load-carrying reinforcement and cellulose creates an interphase in the polymer matrix around the bamboo fiber that prevents sudden crack growth. The influence of MFC dispersion on the properties of the PLA matrix was investigated and substantial improvements in the strain energy until fracture observed. By adding just 1 wt% of MFC with a high degree of dispersion an increase in fracture energy of nearly 200% was obtained. In the hybrid bamboo/MFC/PLA composites there is also a dramatic change in the fracture morphology around the bamboo fiber bundles.     

Improvement of physico-mechanical properties of coir-polypropylene biocomposites by fiber chemical treatment

In preparing polymer–matrix composites, natural fibers are widely used as “reinforcing agents” because of their biodegradable characteristic. In present research, coir fiber reinforced polypropylene biocomposites were manufactured using hot press method. In order to increase the compatibility between the coir fiber and polypropylene matrix, raw coir fiber was chemically treated with basic chromium sulfate and sodium bicarbonate salt in acidic media. Both raw and treated coir at different fiber loading (10, 15 and 20 wt%) were utilized during composite manufacturing. During chemical treatment, hydrophilic –OH groups in the raw coir cellulose were converted to hydrophobic –OH−Cr groups. Microstructural analysis and mechanical tests were conducted. Scanning electron microscopic analysis indicates improvement in interfacial adhesion between the coir and polypropylene matrix upon treatment. Chemically treated specimens yielded the best set of mechanical properties. On the basis of fiber loading, 20% fiber reinforced composites had the optimum set of mechanical properties among all composites manufactured.     

Nanodiamond/poly (lactic acid) nanocomposites: Effect of nanodiamond on structure and properties of poly (lactic acid)

Nanodiamond (ND)/poly (lactic acid) (PLA) nanocomposites with potential for biological and biomedical applications were prepared by using melting compound methods. By means of transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyses (TGA), Dynamic mechanical analyses (DMA), Differential scanning calorimetry (DSC) and Tensile test, the ND/PLA nanocomposites were investigated, and thus the effect of ND on the structural, thermal and mechanical properties of polymer matrix was demonstrated for the first time. Experimental results showed that the mechanical properties and thermal stability of PLA matrix were significantly improved, as ND was incorporated into the PLA matrix. For example, the storage modulus (E′) of 3 wt% ND/PLA nanocomposites was 0.7 GPa at 130 °C which was 75% higher than that of neat PLA, and the initial thermal decomposition was delayed 10.1 °C for 1 wt% ND/PLA nanocomposites compared with the neat PLA. These improvements could be ascribed to the outstanding physical properties of ND, homogeneous dispersion of ND nanoclusters, unique ND bridge morphology and good adhesion between PLA matrix and ND in the ND/PLA nanocomposites.     

Characteristics of continuous unidirectional kenaf fiber reinforced epoxy composites

Kenaf fibers generally has some advantages such as eco-friendly, biodegradability, renewable nature and lighter than synthetic fibers. The aims of the study are to characterize and evaluate the physical and mechanical properties of continuous unidirectional kenaf fiber epoxy composites with various fiber volume fractions. The composites materials and sampling were prepared in the laboratory by using the hand lay-up method with a proper fabricating procedure and quality control. Samples were prepared based on ASTM: D3039-08 for tensile test and the scanning electron microscopy (SEM) was employed for microstructure analysis to observe the failure mechanisms in the fracture planes. A total of 40 samples were tested for the study. Results from the study showed that the rule of mixture (ROM) analytical model has a close agreement to predict the physical and tensile properties of unidirectional kenaf fiber reinforced epoxy composites. It was also observed that the tensile strength, tensile modulus, ultimate strain and Poisson’s ratio of 40% fiber volume content of unidirectional kenaf fiber epoxy composite were 164 MPa, 18150 MPa, 0.9% and 0.32, respectively. Due to the test results, increasing the fiber volume fraction in the composite caused the increment in the tensile modulus and reduction in the ultimate tensile strain of composite.     

Effects of thermal treatment on the mechanical properties of poly(p-phenylene benzobisoxazole) fiber reinforced phenolic resin composite materials

Thermal degradation behaviors of the poly(p-phenylene benzobisoxazole) (PBO) fiber and phenolic resin matrix were investigated. The unidirectional PBO fiber reinforced phenolic resin composite material laminates were fabricated and exposed in a muffle furnace of 300 °C, 550 °C, 700 °C, and 800 °C for 5 min, respectively, to study the effects of thermal treatment on mechanical properties of the composites. After undergone thermal treatments at 300 °C, 550 °C and 700 °C for 5 min, the flexural strength was reduced by 17%, 37% and 80%, respectively, the flexural modulus was decreased by 5%, 14% and 48%, respectively, and the interlaminar shear strength (ILSS) was lowered by 12%, 48% and 80%, respectively. Thermal treatment at 300 °C, the phenolic resin began to pyrolyze and shrink resulted in the irreversible damage of the composites. After 550 °C thermal treatment, the phenolic resin pyrolyzed mostly but the PBO fiber had no obvious pyrolyze, the interface had sever broken. After 700 °C thermal treatment, the phenolic resin formed amorphous carbonaceous and PBO fiber pyrolyzed mostly so the mechanical properties dropped dramatically. At being heated at 800 °C for 5 min, the fiber was nearly totally pyrolyzed and and kept fibrous carbonaceous although the specimen became too brittle to stand any load thereon.     

Influence of alkali treatment on the interfacial and physico-mechanical properties of industrial hemp fibre reinforced polylactic acid composites

The focus of this work was to produce short (random and aligned) and long (aligned) industrial hemp fibre reinforced polylactic acid (PLA) composites by compression moulding. Fibres were treated with alkali to improve bonding with PLA. The percentage crystallinity of PLA in composites was found to be higher than that for neat PLA and increased with alkali treatment of fibres which is believed to be due to the nucleating ability of the fibres. Interfacial shear strength (IFSS) results demonstrated that interfacial bonding was also increased by alkali treatment of fibres which also lead to improved composite mechanical properties. The best overall properties were achieved with 30 wt.% long aligned alkali treated fibre/PLA composites produced by film stacking technique leading to a tensile strength of 82.9 MPa, Young’s modulus of 10.9 GPa, flexural strength of 142.5 MPa, flexural modulus of 6.5 GPa, impact strength of 9 kJ/m², and a fracture toughness of 3 MPa m^1/2.     

Chemical and physical modifications of rice husks for use as composite panels

Modifications of rice husks surfaces by steam and sodium hydroxide (NaOH) were carried out in order to study the effects of these on the surface functional groups properties and performances of the composite panels bonded with phenol formaldehyde (PF) resin. Comparison was made between untreated and ground rice husks. The removal of carbonyl and silica groups as observed by ATR-FTIR improved the rice husk-resin interfacial bonding as revealed by an increase in the modulus of elasticity to 2.76 ± 0.28 GPa, which is above the minimum value of 2.1 GPa recommended in EN 312-3 standard. On the other hand, steam treatment did not lead to any change in the outer surface chemical functional groups. Still, an increase in the mechanical properties of the composite with increase in steam temperature was observed. This showed that other mechanisms than changes in the surface chemical groups led to improved mechanical properties. TGA thermographs of unmodified and NaOH treated rice husks indicated that untreated rice husks exhibited higher thermal stability compared to rice husks treated with NaOH. The decrease in thermal stability of NaOH treated rice husks is an indication of possible degradation of rice husks by the concentrated NaOH used. This study has shown that the use of complementary testing techniques provides useful structure–property relationship in the understanding of the performance of materials.     

Influence of cryogenic thermal cycling treatment on the thermophysical properties of carbon/carbon composites between room temperature and 1900 °C

Influence of cryogenic thermal cycling treatment (from ?120 °C to 120 °C at 1.3 × 10^?3 Pa) on the thermophysical properties including thermal conductivity (TC), thermal diffusivity (TD), specific heat (SH) and coefficient of thermal expansion (CTE) ranging from room temperature to 1900 °C of carbon/carbon (C/C) composites in x-y and z directions were studied. Test results showed that fiber/matrix interfacial debonding, fiber pull-out and microcracks occurred after the cryogenic thermal treatment and they increased significantly with the cycle number increasing, while cycled more than 30 times, the space of microdefects reduced obviously due to the accumulation of cyclic thermal stress. TC, TD, SH and CTE of the cryogenic thermal cycling treated C/C composites were first decreased and then increased in both directions (x-y and z directions) with the increase of thermal cycles. A model regarding the heat conduction in cryogenic thermal cycling treated C/C composites was proposed.     

The effect of crystallization of PLA on the thermal and mechanical properties of microfibrillated cellulose-reinforced PLA composites

This paper describes the thermal and mechanical properties of nanocomposites based on polylactic acid (PLA) and microfibrillated cellulose (MFC). The primary objective of this study was to improve the storage modulus of PLA at a high temperature. MFC and PLA were mixed in an organic solvent with various fiber contents up to 20 wt%, followed by drying, kneading and hot pressing into sheets. The nanocomposites were prepared in two different states, fully amorphous and crystallized. Differential scanning calorimetry (DSC) measurements revealed that the presence of MFC accelerates the crystallization of PLA. The tensile modulus and strength of neat PLA were improved with an increase of MFC content in both amorphous and crystallized states. The addition of 20 wt% of MFC in PLA improved the storage modulus of crystallized PLA at a high temperature (120 °C) from 293 MPa to 1034 MPa.     

Ablation,mechanical and thermal conductivity properties of vapor grown carbon fiber/phenolic matrix composites

The ablation, mechanical and thermal properties of vapor grown carbon fiber (VGCF) (Pyrograf III™ Applied Sciences, Inc.)/phenolic resin (SC-1008, Borden Chemical, Inc.) composites were evaluated to determine the potential of using this material in solid rocket motor nozzles. Composite specimens with varying VGCF loadings (30–50% wt.) including one sample with ex-rayon carbon fiber plies were prepared and exposed to a plasma torch for 20 s with a heat flux of 16.5 MW/m² at approximately 1650°C. Low erosion rates and little char formation were observed, confirming that these materials were promising for rocket motor nozzle materials. When fiber loadings increased, mechanical properties and ablative properties improved. The VGCF composites had low thermal conductivities (approximately 0.56 W/m-K) indicating they were good insulating materials. If a 65% fiber loading in VGCF composite could be achieved, then ablative properties are projected to be comparable to or better than the composite material currently used on the Space Shuttle Reusable Solid Rocket Motor (RSRM).