Lauric acid coated fly ash as a reinforcement in recycled polymer matrix composites

Sustainable composites were developed from fly ash (FA) and recycled polypropylene (R) with lauric acid (LA) as the coupling agent. The FA particles were surface‐coated with 1, 2, 3, and 5 wt % LA, and the coating on the FA particles was verified by transmission electron microscopy and Fourier transform infrared spectroscopy. R and LA‐coated FA particles were melt‐mixed in a 1:1 weight ratio to achieve a high‐filler‐loaded composite. The flexural, impact, nanoindentation, and fracture surface analyses were carried out to examine the properties of the composites. The flexural strength and modulus values increased in the 2 wt % LA‐coated FA/R composites by 6 and 50%, respectively, compared to the values of the uncoated FA/R composites, whereas the impact strength increased considerably by 119% in the 1 wt % LA‐coated composites. Nanoindentation tests also showed an increase in the mechanical properties in the case of the 1 and 2 wt % LA‐coated composites in comparison to the uncoated ones. Fracture surface studies done by scanning electron microscopy revealed improved interfacial interactions between the filler and matrix in the presence of the LA coupling agent. X‐ray diffraction (XRD) studies indicated reorientations of the polymer chains in the presence of different concentrations of the LA coupling agent; this resulted into different crystallinities and crystallite sizes. Differential scanning calorimetry showed a significant difference in the crystalline peaks of the composites, and this corroborated well with the XRD observations. LA, thus, significantly influenced the structural properties of the composites, and this, in turn, influenced their mechanical and thermal properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41586.     

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.     

Light‐weight polypropylene composites reinforced with whole chicken feathers

Light‐weight composites reinforced with whole chicken feathers have better flexural strength than composites reinforced with feather fibers (barbs) and nearly thrice higher tensile strength and seven times higher tensile modulus than composites reinforced with powdered chicken feather quill. Chicken feathers are not only inexpensive and abundantly available but also have unique properties such as low density and hollow centers that make them preferable as reinforcement materials, especially for light‐weight composites. However, the traditional methods of developing composites do not provide the flexibility of using feathers in their native form as reinforcement. So far, the components in feathers such as barbs or quills have been used separately and/or feathers have been mechanically processed to destroy their native form in order to use feathers as reinforcement in composites. A new method of making composites using nonwoven webs as matrix allows the incorporation of reinforcing materials in their native form such as whole chicken feathers to develop composites. This research shows that whole chicken feathers can be used as reinforcement in composites with better flexural, tensile, and acoustic properties than composites made from processed chicken feathers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and open hole tensile properties of self‐reinforced PET composites with recycled PET fiber reinforcement

The tensile strength of notched composites is an important factor for composite structural design. However, no literature is available on the notch sensitivity of self‐reinforced polymer composites. In this study, self‐reinforced recycled poly (ethylene terephthalate) (srrPET) composites were produced by film stacking from fabrics composed of double covered uncommingled yarns (DCUY). Composite specimens were subjected to uniaxial tensile, flexural, and Izod impact tests and the related results compared with earlier ones achieved on srPET composites reinforced with nonrecycled technical PET fibers. Effects of open circular holes on the tensile strength of srrPETs were studied at various width‐to‐hole diameter (W/D) ratios of the specimens. In the open hole tensile (OHT) measurements bilinear (yielding followed by post‐yield hardening) stress–strain curves were recorded. The srrPET composites had extremely high yield strength retention (up to 142%) and high breaking strength retention (up to 81%) due to the superior ductile nature of the srrPETs, which induces plastic yielding near the hole thereby reducing the stress concentration effect. The results proved that srrPET composites are tough, ductile notch‐insensitive materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43682.     

Reusing textile waste as reinforcements in composites

Polyester (PET) has wide applications in textile industries as textile fiber and its share continues to grow. Substantial quantities of cotton/polyester blend fabrics are disposed every year due to technical challenges, which pose a big environmental and waste‐dumping problem. The aim of this study is to evaluate the potential of discarded cotton/PET fabrics as raw materials for composites. If their inherent reinforcement properties can be used in composites, an ecological footprint issue can be solved. In this study, we investigate three concepts for reuse of cotton/PET fabrics for composites: compression molding above the T_m of PETs, use of a matrix derived from renewable soybean oil, use of thermoplastic copolyester/polyester bi‐component fibers as matrix. All three concepts have been explored to make them available for wider applications. The effects of processing parameters such as compression temperature, time and pressure are considered in all three cases. The third concept gives the most appealing properties, which combine good tensile properties with toughness; more than four times better tensile strength than the first concept; and 2.2 times better than the second concept. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40687.     

Green and self-lubricating polyoxymethylene composites filled with low-density polyethylene and rice husk flour

Polyoxymethylene (POM) composites filled with low-density polyethylene (LDPE) and rice husk flour (RHF) were prepared by injection molding. The POM/5 wt % LDPE/7.5 wt % RHF composite exhibited the lowest wear rate, whereas the coefficient of friction remained low, and the POM/5 wt % LDPE/5 wt % RHF composite had the best mechanical properties. X-ray diffraction analysis was carried out, and the worn surfaces were examined with scanning electron microscopy. The results showed that the addition of the filler reduced the crystallinity degree of the POM composites. The main wear mechanism for unfilled POM was adhesion, whereas for the POM composites, wear seemed to occur mainly by fatigue and abrasion. It was experimentally confirmed that the POM composite filled with LDPE and RHF, which is well-performing, low-cost, and environmentally friendly, could be a potential material for tribological applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Computer simulation of the damage evolution of fiber‐reinforced polypropylene‐matrix composites with matrix defects

The damage evolution of fiber‐reinforced polypropylene‐matrix composites with matrix defects was studied via a Monte Carlo technique combined with a finite element method. A finite element model was constructed to predict the effects of various matrix defect shapes on the stress distributions. The results indicated that a small matrix defect had almost no effect on fiber stress distributions other than interfacial shear stress distributions. Then, a finite element model with a statistical distribution of the fiber strength was constructed to investigate the influences of the spatial distribution and the volume fraction of matrix defects on composite failure. The results showed that it was accurate to use the shear‐lag models and Green's function methods to predict the tensile strength of composites even though the axial stresses in the matrix were neglected. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 64–71, 2007     

短碳纤维增强铝基复合材料

通过化学镀再电镀的方法,在碳纤维表面镀上Cu镀层,制备C/Cu复合丝,并在硼酸的保护下,利用非真空条件下的液态机械搅拌法制备短碳纤维增强铝基复合材料,研究了碳纤维在复合材料中的分散程度,铜镀层存在状态及C/Al复合材料的拉伸性能.实验结果表明：在硼酸存在下,大大降低了铜的氧化程度,碳纤维分散均匀且没有损伤,少量硼酸的加入,对复合材料的力学性能没有影响,该复合材料的抗拉强度随碳纤维含量的增加而增加,其抗拉强度较基体材料提高50%以上,但塑性指标却明显下降.     

High shear melt‐processing of fiberglass‐reinforced poly(trimethylene) terephthalate composites

As the demand for polymer‐matrix composites (PMC) expands in order to replace traditional materials, processing of the PMC is increasingly vital, as the morphology and properties are processing dependent. Typically, thermoplastic PMCs are processed in at least two heat‐intensive steps, including a pre‐compounding step in order to achieve good mixing followed by a part fabrication step. The key aim of this study is to prepare a fiberglass‐reinforced poly (trimethylene terephthalate) (FG‐PTT) composite using a one‐step, high shear melt‐processing method that achieves both compounding and part fabrication. The morphology, thermal properties, and mechanical properties are characterized to determine the effect of FG reinforcement on this renewable biopolymer. This novel method produces a FG‐PTT composite with superior mixing and tensile strength, as well as enhanced toughness, in one processing step, reducing polymer degradation and fiber attrition, as well as, time, energy, and cost requirements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42714.     

Recycling carbon fiber composites using microwave irradiation: Reinforcement study of the recycled fiber in new composites

With increasing use of carbon fiber reinforced polymer (CFRP) composites in transportation, sports, and many other industries, recycling of the scrap and end‐of‐life composites has presented both great challenges and opportunities. In this work, we report our study on reclaiming carbon fibers from CFRP using energy efficient microwave irradiation. Different irradiation conditions were used and the optimal conditions were determined based on the surface morphology of the recycled fiber. Polypropylene (PP) and Nylon, representing nonpolar and polar polymers, respectively, were reinforced using the recycled fiber through extrusion and injection molding. For comparison, PP and Nylon reinforced by virgin carbon fiber were also prepared using the same processing conditions. Tensile, flexural, and impact test results showed that, while both carbon fibers could improve these properties, they exhibited different reinforcing effects on the two polymers. The recycled fiber outperformed the virgin fiber in reinforcing PP whereas the virgin fiber performed better in Nylon. This was due to the differences in surface roughness, surface bonding, and fiber aspect ratio between the two fibers. This study shows the great potential of recycled carbon fiber and microwave irradiation as an effective recycling technique. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42658.     

Dynamic mechanical behavior of vinylester matrix composites reinforced by Luffa cylindrica modified fibers

Currently, there is a demand for new engineering materials presenting a combination of strength, low density, processing easiness, and reduced costs. In this context, polymer matrix composites reinforced by natural fibers have been studied in recent years due to their ecological and economic advantages. Some fibers are still little explored in literature despite presenting a great potential as reinforcement like Luffa cylindrica. The present work aims at the preparation and characterization of a vinylester thermoset matrix composite material reinforced by fibers of the natural L. cylindrica fruit after modification treatments. In this study, extraction treatments in organic solvents, mercerization, and a quite new esterification with BTDA dianhydrides were used and the results showed that in all cases, the composite materials reinforced by Luffa fibers have showed improvements in mechanical and thermal properties compared to the vinylester matrix. As an example, 50% tensile increase was obtained for the composite reinforced by fibers esterified with benzophenone tetracarboxylic dianhydride when compared with thermoset matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Temperature‐dependent tensile strength model for 2D woven fiber reinforced ceramic matrix composites

This paper presents a temperature‐dependent model for predicting the tensile strength of 2D woven fiber reinforced ceramic matrix composites. The model takes into account the combined effects of temperature, temperature‐dependent residual thermal stress, temperature‐dependent matrix strength, and fibers strength on the tensile strength of composites. To verify the model, the tensile strengths of 2D woven fiber reinforced ceramic matrix composites available are predicted at different temperatures. The model predictions agree well with the experimental data. This work could provide a practical technical means for predicting the temperature‐dependent tensile strength of 2D woven fiber reinforced ceramic matrix composites and uncovering the dominated mechanisms leading to the change of tensile strength and their evolution with temperature.     

Mechanical and thermal characterization of compression moulded polylactic acid natural fiber composites reinforced with hemp and lyocell fibers

This research evaluates the effects of PLA/PP blend ratio and Lyocell/hemp mixture ratio on the morphology, water absorption, mechanical and thermal properties of PLA‐based composites. The composites were fabricated with 30 mass % hemp using compression moulding. As a reference composites made from PP were also studied. Combining of hemp and Lyocell in PLA composite leads to the reduction of moisture absorption and can improve the impact, tensile, flexural properties when compared with PLA/hemp. Composite based on the PLA/PP blend‐matrix could not improve the tensile and flexural properties compared with PLA/hemp, however; the lighter composite with better impact properties was obtained. The crystallization temperature of the PLA‐PP/hemp increased compared with pure PLA. This result was also confirmed by the SEM micrographs. The moisture absorption of PLA‐PP/hemp was higher than PLA/hemp. Based on theoretical analysis of DMTA data, there was favorable adhesion in all composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40534.     

Preparation of fine fiberglass‐resin powders from waste printed circuit boards by different milling methods for reinforcing polypropylene composites

In this study, different milling methods were used to prepare fine fiberglass‐resin powders (FRP) from waste printed circuit boards for the sake of obtaining high‐performance polypropylene (PP)/FRP composite. The processability and appearance of composites can be greatly improved through further milling of FRP; smaller average particle size and narrower particle size distribution can be obtained by pan milling as compared with jet milling and planetary ball milling. Mechanical test results showed that fine FRP prepared by pan milling could be used as reinforcing fillers in the PP composites and possessed better mechanical properties than other two milling methods. The mechanical properties was also confirmed by scanning electron microscopy studies which indicated that the dispersion of FRP and interfacial adhesion between fiberglass and PP matrix was much better by pan milling. Meanwhile, the heterogeneous nucleation effect of FRP by pan milling was more obvious. The above results indicate that solid‐state shear is a new method for producing fine FRP and high‐performance PP composites filled with FRP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42494.     

Effect of thermal fatigue on the mechanical properties of epoxy matrix composites reinforced with olive pits powder

This study is focused on the investigation of the effect of thermal shock cycling on the mechanical properties of cellulose based reinforced polymer composites. Polymer composites reinforced with olive pits powder at different filler‐volume fractions were manufactured. An increase in the bending modulus on the order of 48% was achieved. On the other hand, results showed that the bending strength remained almost unaffected from the amount of filler introduced. Next, the effect of thermal shock cycling on the mechanical behaviour of the thus manufactured composites was investigated. Theoretical predictions for both the properties variation with number of thermal shock cycles applied as well as with filler‐volume fraction were derived using the residual properties model (RPM) and the modulus predictive model (MPM), respectively. Predicted values were compared with respective experimental results. In all cases, a fair agreement between experimental findings and theoretical predictions was found. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Composition,tensile properties,and dispersion of polypropylene composites reinforced with viscose fibers

The reinforcement mechanics of viscose‐fiber‐reinforced polypropylene (PP) composites were studied. The effect of the coupling agent, maleated polypropylene (MAPP), was of special interest. The fibers, coupling agent, and PP were extruded and injection‐molded. The composition, mechanical properties, fracture morphology, and dispersion of the composites were examined. Thermogravimetric analysis showed that the fiber content in the tensile specimens varied slightly with the sample location; however, the differences in the values were within 1.0%. Scanning electron microscopy images of the fracture surfaces of the composites showed that the surfaces of the composites without MAPP were covered with fibers pulled out from the matrix. A lack of adhesion further appeared as a cracked matrix–fiber interface. A new scanning thermal microscopy method, microthermal analysis, was used to study the dispersion of the fibers in the composites. Local thermal analyses gave further information about the location of the fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2676–2684, 2004     

Graft copolymers of lignin as hydrophobic agents for plastic (wood‐filled) composites

Poly[lignin‐g‐(1‐phenylethylene)] graft copolymers synthesized by free‐radical, graft copolymerization on lignin and verified by fractionation, infrared spectroscopy, and solubility change possess macromolecular surface activity as indicated by their capacity to form stable emulsions between incompatible fluid phases, to adhesively bond to wood surfaces, and to change the contact angle of water on coated wood. The surface activity of the copolymer changes with its composition. As the weight percent lignin in the copolymerization reaction product increases beyond 20 wt %, the amount of the emulsion phase formed in a water–benzene mixture decreases. Maple wood flour could be solvent‐coated with a copolymer and both coated and uncoated maple flour could be extruded through a stranding plate into a wood‐filled composite with polystyrene. Physical property tests show that composite control samples are about 3% stiffer and less deformable than are the copolymer composites when dry and about 5 or more percent more deformable than are the copolymer composites when wet, showing that the copolymer coating increased the wet strength. The copolymer samples are always denser than are the controls. Copolymer coating on wood filler decreases the swelling in the composite, the partial molar volume of the imbibed water, and the dimensional change in the solid. These effects cause increase in the density of the copolymer composite upon imbibition of water. Coating the wood component of the composite with a copolymer creates a hydrophobic barrier that produces a decrease in water imbibition into the composite, which will not disappear in 20 or more years of water immersion. Expansion in water is highly dependent on the direction of extrusion. The length expands about 1%, the width expands about five times as much, and the thickness expands over 10 times as much as does the length. This differential expansion may be due to the 22% reduction in the width and a 71% reduction in the thickness of the melt as it passes through the die and the alignment of the long axis of the fiber with the direction of flow through the die. The reaction product is a thermoplastic solid stable below 200°C and thermoformable at between 150 and 180°C. Products which contain between 10 and 50 wt % lignin are heterogeneous solids. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1266–1276, 2003     

Damage analysis of composites reinforced with Alfa fibers: Viscoelastic behavior and debonding at the fiber/matrix interface

In this article, we first review state‐of‐the‐art experimental techniques and measurements to characterize the mechanical properties of anisotropic vegetal alfa fibers, epoxy‐resin, and the behavior of the interphase between the matrix and alfa fibers. Second, we conduct experimental tests to determine the mechanical properties of fibers, resin, and the interphase. Third, we carry out a series of finite element simulations to predict damage initiation and to estimate crack propagation in alfa‐fiber/epoxy‐resin (AFER) composites. Different tests to determine the longitudinal Young's modulus of alfa fibers and epoxy resin as well as nanoindentation tests to obtain the transverse stiffness of the fibers are presented. Experimental results from the characterization are introduced in a micromechanical model to estimate, using the concept of the energy release rate (ERR), the matrix crack, and its interaction with interfacial debonding. The wettability problems in the preparation of vegetable composites and their effect on fiber‐matrix interfacial debonding are also addressed. The analysis of the damage behavior of AFER composites demonstrates that under load transverse to the fiber axis, a crack initiated in the matrix is propagated perpendicular to the direction of the load. Near the interface, the ERR decreases and this energy is higher in the presence of interfacial debonding areas generated by problems of fiber wettability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43760.     

Natural rubber composites reinforced with sisal/oil palm hybrid fibers: Tensile and cure characteristics

Natural rubber was reinforced with untreated sisal and oil palm fibers chopped to different fiber lengths. The influence of fiber length on the mechanical properties of the hybrid composites was determined. Increasing the fiber length resulted in a decrease in the properties. The effects of concentration on the rubber composites reinforced with sisal/oil palm hybrid fibers were studied. Increasing the concentration of fibers resulted in a reduction in the tensile strength properties and tear strength but an increase in the modulus of the composites. Fiber breakage analysis was evaluated. The vulcanization parameters, processability characteristics, and stress–strain properties of these composites were analyzed. The extent of fiber alignment and the strength of the fiber–rubber interface adhesion were analyzed from the anisotropic swelling measurements. Scanning electron microscopy studies were performed to analyze the fiber/matrix interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2305–2312, 2004     

Optimal formulation of rice husk reinforced polyethylene composites for mechanical performance: A mixture design approach

Rice husk (RH) and linear medium density polyethylene (LMDPE) were used along with maleic anhydride grafted polyethylene (MAPE) to study the effects of component composition on the mechanical properties of the composites. Ten different blends along with four replicated blends were prepared with different selected percentages of RH, MAPE and LMDPE using mixture design approach. Trace and contour plots were used to examine the effects of RH, MAPE and LMDPE on the mechanical properties of the manufactured composites. Regression coefficients were also estimated for each fitted response (mechanical property). The results show that tensile and flexural properties of the composites improved with an increase in amount of RH, whereas Charpy impact strength decreased with increasing fibre loading. Tensile strength, flexural strength and Charpy impact strength increased with an increase in MAPE loading up to a certain percentage of MAPE, beyond which any further increase decreased these properties. The effect of MAPE on tensile and flexural modulus was not significant. The fitted models were used to optimise formulation of RH, MAPE and LMDPE for multiple responses for overall “best” mechanical properties. The optimal formulation for the overall “best” mechanical properties were found to be 50 wt% for RH, 4.1 wt% for MAPE and 45.9 wt% for LMDPE. The mechanical properties of the composite manufactured with this formulation closely matched the values predicted by the models. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40647.