Effects of short fibers and processing additives on HDPE composites properties reinforced with Pinus and Eucalyptus fibers

This work aimed to investigate the effect of adding short fibers of Pinus and Eucalyptus, in different granulometry (24 and 200 mesh) and concentration (0–20 m/m), combined with processing aid Struktol TPW104 (S) in obtaining of high-density polyethylene (HDPE) composites. Overall, obtaining composites from short fibers caused relevant changes in the HDPE matrix, such as thermal stability, moisture barrier. In comparison to pure HDPE, the composites incorporated with 20% m/m of fibers, regardless of the type, decreased the melting temperature to 128°C and a wider crystallization temperature range. Another significant observation was the improvement of composites mechanical profile after adding the additive, the highest values were obtained for composites HDPEL20PS (35%—TS e 651%—EM) and HDPEL20ES (42%—TS e 681%—EM), showing good interaction and compatibility, according to scanning electron microscopy (SEM) images. The same was verified with the mechanical results of flexion and impact. Therefore, the use of short fibers and processing aid was successful providing augmented mechanical properties and thermal stability, without negatively affecting their essential properties for industrial applications.     

Effect of acetylation on the properties of microfibrillated cellulose‐LDPE composites

Solvent‐free acetylation of microfibrillated cellulose was carried out in order to improve their hydrophobicity. All the samples were filled with low‐density polyethylene. The morphology, mechanical properties, and water uptake of the ensuing composites were investigated. An excessive reaction time leads to degradation of the fibers, which was observed by scanning electron microscopy and fiber quality analysis. The acetylation treatment did not improve the mechanical properties of composites but extensively decreased the moisture absorption of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44933.     

Mechanical performance and moisture absorption of various natural fiber reinforced thermoplastic composites

Natural fibers are seeing increased use in composite applications due to their reduced cost, low density, and environmental benefits (more sustainable and lower carbon footprint). Although many natural fiber systems have been examined over the last decade, there have been relatively few studies which have compared a variety of fiber types and processing methods directly in the same experimental set. In this study, natural fiber composites made from low density polyethylene (LDPE) and a variety of Canadian based fiber feedstocks were examined including hemp bast, flax bast, chemically pulped wood, wood chips, wheat straw, and mechanically pulped triticale. The effect of fiber type, fiber fraction and maleic anhydride polyethylene (MAPE) coupling agent on the mechanical properties and long‐term moisture absorption behavior was quantified. In general, addition of natural fiber to LDPE results in an increase in modulus (stiffness) with a corresponding loss of material elongation and impact toughness. Of the fiber types tested, composites made from chemically pulped wood had the best mechanical properties and the least moisture absorption. However, the use of MAPE coupling agent was found to significantly increase the mechanical performance and reduce moisture absorption for all other natural fiber types. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 969‐980, 2013     

Alfa fiber/polypropylene composites: Influence of fiber extraction method and chemical treatments

Alfa fiber/polypropylene composites were manufactured using twin-screw extrusion. Fibers were extracted using alkaline and steam explosion methods. Three chemical treatments were also applied to the alkaline-extracted fibers: stearic acid (SA), and potassium permanganate dissolved in water (KW) and in acetone (KA). Finally, thermal annealing was applied to the composites. The results indicate that composites with steam-exploded fibers had a significantly higher melt flow index than composites with alkaline-extracted fibers. Moreover, the incorporation of fibers into the matrix increased the Young's modulus, where the optimum results were obtained utilizing the alkaline-extracted fibers. Both extraction methods also significantly decreased the water uptake, especially the steam explosion. The three chemical treatments increased the melt flow index and conversely decreased the tensile strength and Young's modulus. In addition, KW treatment decreased the water uptake. Finally, thermal annealing increased the tensile strength and Young's modulus of composites with SA-treated fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47392.     

Torrefied biomass‐polypropylene composites

Torrefied almond shells and wood chips were incorporated into polypropylene as fillers to produce torrefied biomass‐polymer composites. The composites were prepared by extrusion and injection molding. Response surface methodology was used to examine the effects of filler concentration, filler size, and lignin factor (relative lignin to cellulose concentration) on the material properties of the composites. The heat distortion temperatures, thermal properties, and tensile properties of the composites were characterized by thermomechanical analysis, differential scanning calorimetry, and tensile tests, respectively. The torrefied biomass composites had heat distortion temperatures of 8–24°C higher than that of neat polypropylene. This was due to the torrefied biomass restricting mobility of polypropylene chains, leading to higher temperatures for deformation. The incorporation of torrefied biomass generally resulted in an increase in glass transition temperature, but did not affect melting temperature. Also, the composites had lower tensile strength and elongation at break values than those of neat polypropylene, indicating weak adhesion between torrefied biomass and polypropylene. However, scanning electron microscopy results did indicate some adhesion between torrefied biomass and polypropylene. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41582.     

Optimization of the silane treatment of cellulosic fibers from eucalyptus wood using response surface methodology

Viscose cellulosic fibers from eucalyptus wood were treated with organosilanes to introduce specific functionalities on the fibers and enhance their wettability and adhesion with phenolic matrices in composites. Modeling procedures were employed to optimize the conditions of the treatments of the fibers with the silanes (3‐aminopropyl) trimethoxysilane (APS) and 3‐(2‐aminoethylamino) propyltrimethoxysilane (AAPS). The analyzed responses were relative intensities of the bands 1565/897 and 1120/897 cm⁻¹, measured by Fourier transform infrared spectroscopy, and the silicon amount incorporated into the cellulosic fibers, which was determined by energy dispersive X‐ray analysis. In addition, surface morphology of the silane treated fibers was observed using scanning electron microscopy. The treatments of the cellulosic fibers with 2.2% APS for 120 min and 1.5% AAPS for 100 min were selected as optimums. According to contact angle measurements, both treatments enhanced the wettability between the fibers and a resol‐type phenolic resin, revealing the possible use of the silane treated fibers as reinforcement in phenolic composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42157.     

A comparative study on the effects of material blending method on the physico‐mechanical properties of WPCs made from MDF dust

The present study was carried out to investigate the effect of material ‐ blending method and filler content on the physical and mechanical properties of medium density fiberboard (MDF) dust/PP composites. In the sample tests preparation, 40, 50, and 60 wt % of MDF dust were used as lignocellulosic material. Test samples were made to measure the influence of material ‐ blending method and MDF dust content on water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), modulus of rupture (MOR), tensile strength, tensile modulus, and withdrawal strengths of fasteners. The mechanical properties of the test panels significantly decreased with increasing MDF dust contents due to the reduction of interface bond between the fiber and polymer matrix. The WA and TS values also increased by increasing the amount of MDF dust. So with the increase in the MDF dust content, there are more water residence (high hydroxyl groups (? OH) of cellulose and hemicelluloses) sites, thus more water is absorbed, so it can reduce mechanical strength. Furthermore, the results indicated that the physical and mechanical properties of samples made with melt ‐ blend method were more acceptable than those of dry ‐ blend method. Field emission scanning electron microscopy micrographs also showed that the polymer and the filler phase mixed better in the melt ‐ blend method. On the basis of the findings of this research, it appears evident that certain amount of MDF dust material with suitable material ‐ blending method can be used in manufacturing of wood–plastic composites for providing good physical and mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40513.     

Extraction of fibers from saccharum munja grass and its application in composites

With growing environmental awareness, ecological concerns and new legislations, natural fiber‐reinforced plastic composites have received increasing attention during the recent decades. The natural fiber composites have many advantages over traditional glass fiber composites, including lower cost, lighter weight, environmental friendliness, and recyclability. This article reports the findings of the studies done on a new fiber, hitherto unexplored, extracted from Saccharum munja grass. The extracted fibers were further treated using sodium hydroxide to improve its performance in composites. Both treated and untreated fiber‐reinforced composites were prepared by hand lay‐up process using unsaturated polyester resin. Mechanical properties and thermal behavior of the composites were evaluated. The improvement in properties was found for alkali‐treated fiber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40829.     

Processing of wood plastic composites: The influence of feeding method and polymer melt flow rate on particle degradation

Spruce wood particle (WP)/polypropylene (PP) compounds were prepared in an internal mixer using different rotor speeds. To analyze the effect of feeding method on particle degradation, WP and PP were either fed as dry‐blend or WP was fed into the PP melt. To prevent melt freezing, pre‐heated WP were used as comparison to cold WP. In addition, WPs were compounded with different grades of PP or high‐density polyethylene (HDPE) to analyze the effect of polymer matrix melt flow rate (MFR) on particle degradation. Mixing behavior of compounds containing 30% and 70% (w/w) WP depended on feeding method, represented by a changing relation of final torque values. Feeding as dry‐blend and using pre‐heated particles led to stronger WP degradation. Degradation decreased with increasing polymer MFR. For PP compounds, particle degradation was stronger when containing 70% WP, for HDPE the difference due to WP content was only marginal. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43231.     

Resistance of paper mill sludge/wood fiber/high‐density polyethylene composites to water immersion and thermotreatment

The disposal of paper mill sludge (PMS) is a difficult environmental problem. Thus, PMS has been used as a substitute for wood fiber (WF) to reinforce high‐density polyethylene (HDPE). In this study, we compared PMS–WF–HDPE composites with composites without PMS after water immersion and thermal treatment. Water immersion and thermal treatment were conducted at 25 and 70°C, respectively. The results show that the composites with PMS absorbed less water but lost more of their original flexural properties after immersion; thereby, their strength was compromised. These reduced mechanical properties could be partially restored after redrying. After the thermotreatment, the composites with added PMS lost their weight and flexural properties, whereas the composites without PMS gained flexural strength. The results show that the thermotreatment improved the impact strength of the composites when no more than one‐third of WF was replaced with PMS. Fourier transform infrared spectroscopy and energy‐dispersive X‐ray energy‐dispersive spectroscopy showed that the wood index of the PMS composite decreased more than the index of the non‐PMS composite, whereas the carbonyl index increased more. However, the PMS composite showed a lower increase in the total oxygen/carbon weight ratio. This study suggested that limited amounts of WF could be substituted with PMS to reinforce HDPE. However, WF–PMS–HDPE composites should not be used in hot, humid environments for long periods. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41655.     

Preparation,structure, and property of wood flour incorporated polypropylene composites prepared by a solid‐state mechanochemical method

In this article, a solid‐state mechanochemical method based on a pan‐mill equipment was used to prepare 60 wt % loading of wood flour (WF) incorporated polypropylene (PP) wood–plastic composite (WPC) with good comprehensive performance. The particle size distribution, crystallization, microstructure, and properties of the prepared WPC were accordingly investigated. The results show that under co‐effects of the strong shear force field of pan milling and the compatibilization of PP grafted maleic anhydride (PP‐g‐MAH), the mixture of PP and WF is effectively pulverized and homogeneously mixed. Meanwhile, the WF particles are adequately activated by exposure of their characteristic functional groups, which is beneficial to the interfacial mechanochemical reaction. PP‐g‐MAH and PP prove to be in situ grafted onto WF particles surface during pan milling, thus resulting in the substantial enhancement in both the dispersion of the added WF fillers in PP matrix and the interfacial bonding. The mechanochemical effects of pan milling could also remarkably promote the heterogeneous nucleation effect of WF particles on PP crystallization and influence the dynamic mechanical behavior of composite. Compared with the unmilled and uncompatibilized composite, the milled and compatibilized WPC material possesses greatly enhanced mechanical performance and shows good application prospects. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43108.     

Plasma treatment of wood–polymer composites: A comparison of three different discharge types and their effect on surface properties

Three different discharge types, based on the principle of a dielectric barrier discharge at atmospheric pressure, were investigated with regard to their influence on the adhesion properties of a series of wood–polymer composites. Wood flour (Picea abies L.) filled polypropylene and various proportions of polyethylene were manufactured either through extrusion or injection molding. The composites’ surfaces were activated by coplanar surface barrier discharge, remote plasma, and direct dielectric barrier discharge. The changes in wettability due to the pretreatment were investigated by contact angle measurement using the sessile drop method and calculation of surface free energy (SFE). It could be shown that wettability was improved by all three types of discharge, the contact angle decreased and the SFE correspondingly increased. X‐ray photoelectron spectroscopy revealed an increase in the O/C ratio at the material's surface. An improvement in coating adhesion was demonstrated by crosscut and pulloff tests. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43376.     

Thermoplastic composites of polyamide‐12 reinforced by cellulose nanofibers with cationic surface modification

Cellulose nanofibers (CNFs) have many useful properties, including high strength and low thermal expansion, and are also environmentally friendly, readily renewable, safe, and biodegradable. The focus of this study was the development of lightweight thermoplastic polymer composites with good mechanical properties based on the incorporation of CNFs that have undergone surface pretreatment with a cationic reagent. The polyamide (PA12) was mixed with surface‐treated CNFs using a twin screw extruder and the resulting pellets were injection molded. The Izod impact strength without notch of CNF‐based composites exceeded that of composites incorporating organophilic montmorillonite (OMMT), a representative nanocomposite material. When the Izod impact test without notch, the impact hammer was stopped by the specimen with incorporation of surface treated CNF. Furthermore, the bending modulus and strength were equal to or greater than that of OMMT composites. The heat distortion temperature was improved as 33°C from neat PA12, and moreover improved as 29°C from OMMT composites. Cationic pretreatment of the CNF surfaces was found to increase the dispersion of the fibers and also to greatly improve the mechanical and thermal properties of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40920.     

Syndiotactic polypropylene/microfibrous cellulose composites: Effect of filler size on tensile properties

Syndiotactic polypropylene (SPP)/ethanol swelled microfibrous cellulose (MFC) composite was prepared by a melting mixer, and its morphology and tensile properties were studied. The scanning electron microscope microphotograph did not show the aggregated MFC part up to the 40 wt % MFC loading content, and the Young's modulus was exponentially increasing with the increase of the MFC loading content. These results suggested that the MFC was well‐dispersed in the SPP matrix by an ethanol surfactant work. The Young's modulus was much higher than that of the composite with commonly used fibrous cellulose and moreover, exceeded the theoretical one obtained from the Halpin‐Tsai equation. The differential scanning calorimetry and wide‐angle X‐ray diffraction measurements showed that the MFC acted as a good α‐nucleation agent for SPP. It was found that the excessive Young's modulus of the MFC composite was originated from an increase of that of the SPP matrix induced by the α‐nucleation effect. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Processing–formulation–performance relationships of polypropylene/short flax fiber composites

This work is a comprehensive study of the effect of extrusion process parameters and formulation on the properties of polypropylene (PP)/short flax fiber composites. The parameters that were varied during the twin‐screw extrusion process were screw configuration, revolutions per minute (rpm), extrusion temperature, and flow rate. The effect of the feeding zone location of cellulosic fiber was also considered. This study investigates the effect of the formulation, cellulosic fiber content, the presence of a coupling agent, and of a reactive additive on composite performance. The composites were characterized in terms of morphology and microstructure, fiber length, rheological, thermal, and mechanical properties. Sensibility to humidity and recyclability were also considered. When compared with as‐received PP, the tensile strength of injection‐molded parts increased with cellulosic content by up to 40 vol %, and the tensile modulus increased 3.5 times when a combination of coupling and reactive agents was used. Exposed to controlled humidity of 50% during 1 year, these composites exhibited a very low level of humidity uptake around 0.85 wt %. The processability of these materials using a cast film line and the mechanical properties of extruded sheets are also presented. Furthermore, these materials demonstrate a good recyclability using injection molding by keeping the integrality of their mechanical properties after five reprocessing cycles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41528.     

Wood‐based composites with thermoplastic polyurethane as matrix polymer

This research reports the influence of the mechanical properties of thermoplastic polyurethane (TPU) as a function of wood filler percentage. Wood flour was mixed with two different chemically based TPUs. Also, moisture content during compounding process as well as the origin of moisture (wood or TPU) were studied. All experimental designs and statistical analysis were done with the software Design Expert Version 10. Composite preparation took place in a multi‐stage process. The results showed that 70% wood filler can be incorporated in the composite manufacture. The properties of the composite were mainly influenced by the proportion of wood and TPU. Wood flour increased the density, hardness, water absorption, and tensile modulus with a decrease in impact resistance and abrasion resistance of the composite. Tensile strength exhibited a decrease up to ～35% wood content, but an increase with further addition of wood. Moisture content had only a minor influence on the mechanical and water absorption properties despite the noted severe moisture sensitivity of TPU, which usually leads to decline in mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46344.     

Melt processing of nanocomposites of cellulose nanocrystals with biobased thermoplastic polyurethane

Nanocomposites of thermoplastic polyurethane (TPU) with cellulose nanocrystals (CNC) without and with surface treatment are obtained by melt processing. Nanocomposites are obtained with nanofiller weight content near of the theoretical percolation threshold (3.9 wt%). Visual observation of CNC agglomerates is sufficient to prove the inefficiency of the mixing in systems with untreated CNC. The crystallization kinetics of the TPU changes with the addition of CNC and this is confirmed by differential scanning calorimetry analysis. Thermogravimetric analysis prove that the addition of CNC increases the thermal stability of the TPU. From the rheological analysis it is possible to verify the absence of percolation and an intermediate state of sol–gel transition in the nanocomposites. CNC/TPU nanocomposites with 5 wt% of treated CNC present better mechanical performance than de neat TPU and the other processed nanocomposites and display around 130% increase in Young's modulus while retaining significant values of toughness, tensile strength and elongation at break.     

Thermal and mechanical properties of wood‐plastic composites filled with multiwalled carbon nanotubes

Wood plastic composites (WPCs) are a new generation of green composites which can come mostly from recycled materials. This study focuses on the thermal conductivity and mechanical properties of WPCs filled multiwalled carbon nanotubes (MWCNTs). The thermal conductivity increases with increasing amount of MWCNTs and decreases with increasing temperature. By comparing the temperature changes of specimens during heating and cooling processes, WPCs with higher MWCNTs contents presents higher average temperature when heated until equilibrium temperature. From differential scanning calorimeter test, the melting temperatures of MWNTs reinforced WPCs change slightly, but the crystallinity is reduced with the increasing amount of MWCNTs. Based on a series of laboratory experiments carried out to investigate the mechanical performance, it can be concluded that the addition of the MWCNTs decreases the mechanical properties of WPCs due to the decohesion between thermoplastic matrix and MWCNTs particles under stress. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46308.     

Polypropylene–wood fiber composites: Effect of treatment and mixing conditions on mechanical properties

Polypropylene/wood fiber composites were prepared at three different temperatures: 170°C, 180°C, and 190°C. The surface of wood fibers was modified through the use of silane coupling agents and/or coating with polypropylene or maleated polypropylene. The fiber coating was performed by propylene polymerization in the presence of wood fibers or by immersion in an o-dichlorobenzene polypropylene (or maleated polypropylene) solution. Tensile and three-point bending tests were performed in order to evaluate the adhesion between matrix and wood fibers. Evidence shows that 180°C is the best mixing temperature, while the use of vinyl-tris (2-methoxy ethoxy) silane with or without maleated polypropylene coating is the best surface treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1227–1235, 1997     

Effect of bio‐oil and epoxidized linseed oil on physical,mechanical, and biological properties of treated wood

In this article, the effects of bio‐oil and epoxidized linseed oil (ELO) on water absorption, tangential swelling, decay and insect resistance, thermo‐gravimetric analysis, and mechanical properties of treated wood samples were studied. The bio‐oil used in this article was by‐product of ThermoWood thermal modification process. Linseed oil and hydrogen peroxide were used to prepare ELO. The results indicated that the samples treated with bio‐oil had lower water absorption than that of the control group. The second treatment with ELO significantly reduced further the water absorption. The decay resistance of treated wood samples with 20% of bio‐oil against brown (Coniophora puteana) and white rot (Trametes versicolor) fungi was very high. According to the insect test results, increasing bio‐oil concentration from 10% to 20% significantly decreased surviving rate of Hylotrupes bajulus. Thermo‐gravimetric analysis showed that all treated samples had higher initial deterioration temperature than that of the control group. Regarding the wood strength, the impregnated bio‐oil generally reduced the mechanical properties of wood except modulus of elasticity (MOE). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1562–1569, 2013