Wood‐thermoplastic composites from wood flour and high‐density polyethylene

High‐density polyethylene/wood flour (HDPE/WF) composites were prepared by a twin‐screw extruder. The effects of WF, silane coupling agents, polymer compatibilizers, and their content on the comprehensive properties of the WF/HDPE composites have been studied in detail, including the mechanical, thermal, and rheological properties and microstructure. The results showed that both silane coupling agents and polymer compatibilizers could improve the interfacial adhesion between WF and HDPE, and further improve the properties of WF/HDPE composites, especially with AX8900 as a compatibilizer giving higher impact strength, and with HDPE‐g‐MAH as a compatibilizer giving the best tensile and flexural properties. The resultant composite has higher strength (tensile strength = 51.03 MPa) and better heat deflection temperature (63.1°C). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of m‐isopropenyl‐α,α‐dimethylbenzyl isocyanate grafted polypropylene on the interfacial interaction of wood‐flour/polypropylene composites

In this article, the effects of m‐isopropenyl‐α,α‐dimethylbenzyl isocyanate grafted polypropylene (m‐TMI‐PP) on the interfacial interaction of wood‐flour/polypropylene (WF/PP) were investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry, dynamic rheological analysis, and mechanical properties tests. The experimental results demonstrated that m‐TMI‐PP greatly improved the interfacial interaction between WF and PP. According to the DSC results, m‐TMI‐PP made the crystallization temperature and the crystallization degree of PP in WF/m‐TMI‐PP/PP decrease when compared with WF/PP composite without m‐TMI‐PP, but it was still higher than pure PP. These results demonstrated that WF presented the nucleate effect for the crystallization of PP and m‐TMI‐PP improved the interfacial adhesive, which restrained the mobility of PP chain. The rheological analysis indicated that the complex viscosity, storage, and loss modular of WF/PP composite increased, and the tan δ decreased with the addition of m‐TMI‐PP. This was attributed to the strong improvement effects of m‐TMI‐PP on the interfacial interaction of the composites, and was further confirmed by the mechanical properties tests and SEM analysis of the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Modified polyaniline and its effects on the microstructure and antistatic properties of PP/PANI‐APP/CPP composites

Polypropylene (PP) composites that contain poly(aniline) (PANI) and ammonium polyphosphate crystalline form II (APP‐II) have both antistatic and flame‐retardant properties. In the present study, double anti‐functional PANI was prepared via in situ polymerization in the presence of APP‐II. Analysis of the Fourier transform infrared spectra demonstrated that PANI was synthesized successfully with APP‐II and that modified PANI (PANI‐APP) was obtained. Next, PP/PANI‐APP/chlorinated poly(propylene) (CPP) and PP/PANI/CPP composites were prepared. The results showed that the volume resistivity of the PP/PANI‐APP/CPP composite was at least 100 times less than that of the PP/PANI/CPP composite. The microstructures of the corresponding composites were investigated carefully by scanning electron microscopy and wide angle X‐ray diffraction. The areas of the conductive regions and the percentage crystallinity of PP in the PP/PANI‐APP/CPP composite were distinctly higher than those in the PP/PANI/CPP composite, i.e., by about 10% and 7%, respectively. In addition, experimental analyses of the limiting oxygen index and thermogravimetry showed that the PP/PANI‐APP/CPP composite had advantages compared with PP in terms of its flame‐retardant properties thermal stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40732.     

Shear‐induced crystallization of injection molded vetiver grass‐polypropylene composites

Vetiver grass was used as an alternative filler in polypropylene (PP) composites in this study. Chemical treatment of vetiver grass by alkalization was carried out to obtain alkali‐treated vetiver grass. It was shown that alkali‐treated vetiver grass exhibited higher thermal stability than untreated vetiver grass. Injection molding was used to prepare the composites. The microstructure of injection molded samples showed a distinct skin layer due to shear‐induced crystallization. It was found that normalized thickness of shear‐induced crystallization layer of the composite was lower than that of neat PP. The effect of vetiver particle sizes on shear‐induced crystallization and physical properties of the composites were elucidated. Furthermore, the effect of processing conditions on shear‐induced crystallization, degree of crystallinity, gapwise crystallinity distribution, and mechanical properties of the composite were investigated. It was shown that injection speed and mold temperature affected the normalized thickness of shear‐induced crystallization layer and degree of crystallinity of the composites. However, processing conditions showed insignificant effect on the mechanical properties of vetiver fiber‐PP composites. The degree of crystallinity showed no distribution throughout the thickness direction of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic crystallization of polypropylene and wood‐based composites

Thermoplastic composites made of an isotactic polypropylene (iPP) matrix and woodflour (WF) were prepared by melt‐blending, using twin‐screw extrusion and injection molding. Up to 20 wt % of the composite was composed of WF. The incorporation of an interfacial agent made of an ethylene/methacrylic acid copolymer to iPP and WF, PP/WF, binary blends causes a compatibilization effect that becomes evident due to a reduction in the crystallization temperature of PP. In both the binary composites and the compatibilized or ternary composites, the PP adopts an α or monoclinic structure when crystallization occurs from the melt under dynamic conditions at cooling rates between 1 and 20°C min^?1. On the other hand, X‐ray diffraction analysis using synchrotron radiation of the injection‐molded samples demonstrates the existence of a β or trigonal form in the binary as well as the ternary PP/WF composites. They reach k_β levels between 0.18 and 0.25, which can be interpreted as the co‐operation between a reduction of the crystallization rate and the shear effect induced during the injection. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6028–6036, 2006     

Morphological,mechanical, and physical properties of composites made with wood flour‐reinforced polypropylene/recycled poly(ethylene terephthalate) blends

Wood flour (WF)‐filled composites based on a polypropylene (PP)/recycled polyethylene terephthalate (r‐PET) matrix were prepared using two‐step extrusion. Maleic anhydride grafted polypropylene (MAPP) was added to improve the compatibility between polymer matrices and WF. The effects of filler and MAPP compatibilization on the water absorption, mechanical properties, and morphological features of PP/r‐PET/WF composites were investigated. The addition of MAPP significantly improved mechanical properties such as tensile strength, flexural strength, tensile modulus, and flexural modulus compared with uncompatibilized composites, but decreased elongation at break. Scanning electron microscopic images of fracture surface specimens revealed better interfacial interaction between WF and polymer matrix for MAPP‐compatibilized PP/r‐PET/WF composites. MAPP‐compatibilized PP/r‐PET/WF composites also showed reduced water absorption due to improved interfacial bonding, which limited the amount of absorbable water molecules. These results indicated that MAPP acts as an effective compatibilizer in PP/r‐PET/WF composites. POLYM. COMPOS., 38:1749–1755, 2017. © 2015 Society of Plastics Engineers     

Flammability and mechanical properties of wood flour‐filled polypropylene composites

Polypropylene (PP) composites filled with wood flour (WF) were prepared with a twin‐screw extruder and an injection‐molding machine. Three types of ecologically friendly flame retardants (FRs) based on ammonium polyphosphate were used to improve the FR properties of the composites. The flame retardancy of the PP/WF composites was characterized with thermogravimetric analysis (TGA), vertical burn testing (UL94‐V), and limiting oxygen index (LOI) measurements. The TGA data showed that all three types of FRs could enhance the thermal stability of the PP/WF/FR systems at high temperatures and effectively increase the char residue formation. The FRs could effectively reduce the flammability of the PP/WF/FR composites by achieving V‐0 UL94‐V classification. The increased LOI also showed that the flammability of the PP/WF/FR composites was reduced with the addition of FRs. The mechanical property study revealed that, with the incorporation of FRs, the tensile strength and flexural strength were decreased, but the tensile and flexural moduli were increased in all cases. The presence of maleic anhydride grafted polypropylene (MAPP) resulted in an improvement of the filler–matrix bonding between the WF/intumescent FR and PP, and this consequently enhanced the overall mechanical properties of the composites. Morphological studies carried out with scanning electron microscopy revealed clear evidence that the adhesion at the interfacial region was enhanced with the addition of MAPP to the PP/WF/FR composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of compatibilizers and processing temperature on microcellular injection‐molded polypropylene/(waste tire powder) composites

Nowadays the economic recycling of waste tires has become a global challenge. The use of waste tire powder as a dispersed elastomeric phase in a polypropylene (PP) matrix offers an interesting opportunity for recycling of waste tire rubber. Compatibilized PP/(waste tire powder) composites are microcellularly processed to create a new class of materials with unique properties. Recent studies have demonstrated the feasibility of developing microcellular structures in PP/waste ground rubber tire (WGRT) composites. Microcellular PP/WGRT composites are prepared by an injection‐molding process using a chemical blowing agent. In this study, cell sizes, cell density, void fraction, and mechanical properties of the composite foams were measured, as well as the shear viscosity of the unfoamed composites. The influence of various compatibilizers and processing temperatures on cell morphology and the mechanical properties of injection‐molded PP/WGRT composites were investigated. It was seen that the addition of maleic anhydride‐grafted styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) increased the shear viscosity of the composites. The void fraction and cell density of the PP/WGRT composites increased with addition of compatibilizers, whereas the average cell sizes decreased. A processing temperature range of 180–195°C gave finer microcellular structure and regular cell distribution. The SEBS‐g‐MA enhanced the elongation properties and acted as an effective compatibilizer in this particular system. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Static and dynamic mechanical properties of a kenaf fiber–wood flour/polypropylene hybrid composite

A natural fiber hybrid composite containing equal proportions of kenaf fibers (KFs) and wood flour (WF) as the reinforcements and polypropylene (PP) as the polymer matrix was prepared, and its static and dynamic mechanical properties were compared with KF/PP and WF/PP composites. Static tensile and flexural tests and dynamic mechanical analysis (DMA) were carried out. The hybrid composite exhibited tensile and flexural moduli and strength values closer to those of the KF composite, which indicated a higher reinforcing efficiency of KFs compared with WF. DMA revealed that although the glass‐transition temperature remained unchanged by the replacement of half of the WF by KFs, the α‐transition temperature of the hybrid composite was identical to that of WF composite. The magnitudes of both the α and β (glass) transitions of the hybrid composite were comparable to that of the WF/PP composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 665–672, 2005     

Comparative study for the talc and two kinds of moroccan clay as reinforcements in polypropylene‐SEBS‐g‐MA matrix

Polypropylene (PP) or modified PP is one of the most commonly used synthetic polymers for the development of materials in construction, automotive, packaging, and other applications. However, improvements of inherent mechanical, thermal, and morphological properties are required to transfer its potential into reality. In this context, some comparative study with talc and Moroccan clay were performed to improve the inherent properties of modified PP i.e., PP‐SEBS‐g‐MA matrix composite of PP‐SEBS‐g‐MA with different loadings of talc and Moroccan clays. All the composites samples were prepared by melt mixing method. Thermal and Mechanical properties of the composite sample were higher than unreinforced samples. Improvement of crystalinity, thermal stability, and rigidity was observed in the composite samples due to incorporation of the filler. Highest young modulus was observed in case of talc filled PP composites. It's observed from Tsai‐pagano model results that the young's modulus of talc still higher than that of both clay particles, but using the density of fillers, the results in terms of specific properties shown that the specific rigidity is comparable. In summary, it was examined the ability of Moroccan clay particles, as an alternative filler for PP composite compared with the traditional commercial reinforcements such as talc and mineral calcium carbonate. POLYM. COMPOS., 36:675–684, 2015. © 2014 Society of Plastics Engineers     

Influence of ammonium polyphosphate modified with 3‐(methylacryloxyl) propyltrimethoxy silane on mechanical and thermal properties of wood flour–polypropylene composites

In this article, the influence of ammonium polyphosphate (APP) and ammonium polyphosphate modified with 3‐(Methylacryloxyl) propyltrimethoxy silane (M‐APP) on mechanical properties, flame retardancy, and thermal degradation of wood flour–polypropylene composites (WF/PP composites) have been investigated. Polypropylene grafted with m‐isopropenyl‐α,α‐dimethylbenzyl‐isocyanate (m‐TMI‐g‐PP) was used to improve the adhesion of WF/PP composites. APP and M‐APP were used as flame retardants. The experimental results demonstrated that addition of M‐APP obviously enhanced mechanical properties of WF/PP composites. According to cone calorimetry results, M‐APP is also an effective flame retardant for WF/PP composites, compared to that of APP. It was also found that M‐APP decreased the 1% weight loss temperature and increased char residue. The thermal degradation of wood flour based upon the first peak temperature of wood decreased from 329.3 to 322.9°C and the thermal degradation of PP based upon the second peak temperature of PP improve from 518.0 to 519.6°C, when M‐APP was added to the WF/PP composites. From SEM results the char layer of the 25% M‐APP systems is much more intumescent than that of the 25% APP systems, indicating that 3‐(Methylacryloxyl) propyltrimethoxy silane can improve the char‐forming ability of WF/PP composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of maleated polypropylene as a compatibilizer and hyperbranched polyester as a processing aid on polypropylene‐wood flour biocomposites

This work focused on two difficulties associated with preparation of polypropylene/wood flour (PP/WF) composites, viz. the compatibility of PP with WF and processing of the composites with high melt viscosity. Maleic anhydride‐grafted polypropylene (MAPP) was used in the preparation of PP composites to provide the compatibility between polymer and filler. Hyperbranched polyester (HBPE) was incorporated to check feasibility of it as a processing aid in the same. The PP/WF composites were formulated by melt compounding on a Brabender Plastograph EC. Blending effect of compatibilizer and processing aid HBPE on PP/WF biocomposites have been carried out on the basis of torque analysis, mechanical properties, morphology, and thermal stability. The investigation showed that HBPE improves the processibility of PP/WF composites than MAPP with respective to torque value. The mechanical and thermal properties slightly vary with change in relative proportion of MAPP and HBPE. J. VINYL ADDIT. TECHNOL., 24:179–184, 2018. © 2016 Society of Plastics Engineers     

The effect of poly[styrene‐b‐(ethylene‐co‐butylene)‐ b‐styrene] on dielectric,thermal, and morphological characteristics of polypropylene/silica nanocomposites

The effect of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) copolymer on the thermal and dielectric properties of polypropylene (PP)—nanosilica (NS) composites in relation with morphological aspects revealed by atomic force microscopy (AFM) was investigated in this article. SEBS hindered the crystallization process of PP in PP/NS composites, leading to a smaller degree of crystallinity and lower perfection of crystalline structure. Broader lamellar thickness distribution was obtained in nanocomposites containing SEBS. Almost two times higher dielectric loss as compared to PP reference and two relaxation processes were detected in ε_r ^′′(f) curves of nanocomposites. The first peak, in the same frequency domain as for the references, was assigned to α‐relaxation of polymer components together with interfacial polarization. The relaxation time follows the Arrhenius law with an activation energy of 80–90 kJ/mol. For the second process, the temperature dependence of the relaxation times obeyed the VFT equation. The dielectric changes following the incorporation of SEBS support its tendency to hinder the motional processes in PP, in accordance with DSC results. A smooth transition from a phase rich in SEBS to one containing mainly PP was detected in the AFM image of the composite with the larger amount of SEBS, emphasizing the good compatibility at the PP/SEBS interface. POLYM. ENG. SCI., 53:2081–2092, 2013. © 2013 Society of Plastics Engineers     

Properties and nanoscale structure of polypropylene‐layered double hydroxide composites prepared by compatibilizer‐free way

Polypropylene (PP) is the second most widespread commodity polyolefin. Even a small quantity of inorganic component is sufficient to achieve significant improvement of stiffness, strength, thermal stability, biodegradability, etc. The major drawback of inorgano‐organic composite materials is insufficient compatibility of the PP matrix with inorganic filler. A suitable choice of the layered double hydroxide‐modifying anion opens a possibility to obtain PP‐inorganic nanocomposites without a need to use compatibilizers like maleic anhydride grafted PP. The nanocomposites were prepared by melt blending in a twin‐screw mini‐extruder and characterized by dynamic mechanical thermal analysis, and electron microscopy. Nonpolar PP matrix mix uniformly with clay organophilized with functionalized surfactant acids, giving rise to composites with improved thermo‐mechanical properties. Influences of the anionic modifier and the filler content (2 or 5% w/w) on mechanical properties and nanoscale structure of the composites are discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2429–2438, 2013     

Characterization of melt‐compounded and masterbatch‐diluted polypropylene composites filled with several fillers

The effect of various fillers on the mechanical, barrier, and flammability properties of polypropylene (PP) was studied. PP was filled with 4 wt% of nano‐sized calcium carbonate, titanium dioxide, organoclay, and multiwalled carbon nanotube (MWCNT). For comparison, micron‐sized calcium carbonate was also studied. Two‐step masterbatch dilution approach of the composites suggested no or only minor improvements in Young's modulus and tensile yield strength, whereas their ductility decreased compared to coupling agent‐modified PP matrix. The water vapor transmission results of filled films showed increased permeability compared to their coupling agent‐modified counterpart. Oxygen permeability, however, decreased for the composites. The MWCNT‐filled matrix showed the highest barrier and fire performance, attributed mainly to its higher filler volume content, but also other reasons such as the effect of filler dispersion, composite's thermal stability, and polymer crystallinity were discussed.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Effects of the accelerated freeze‐thaw cycling on physical and mechanical properties of wood flour‐recycled thermoplastic composites

This study investigated durability performance of wood‐plastic composites (WPCs) that were exposed to accelerated cycling of water immersion followed by freeze thaw (FT). The WPCs used in this study were made of high‐density polyethylene (HDPE) or polypropylene (PP) with radiata pine (Pinus radiata) wood flour using hot‐press molding. These two types of plastics included both recycled and virgin forms in the formulation. In the experiments, surface color, flexural properties, and dimensional stability properties (water absorption and thickness swelling) were measured for the FT cycled composites and the control samples. Interface microstructures and thermal properties of the composites were also investigated. The results show that the water absorption and the thickness swelling of the composites increased with the FT weathering. In the meantime, the flexural strength and stiffness decreased. Scanning electron microscopy (SEM) images of the fractured surfaces confirmed a loss of interface bonding between the wood flour and the polymer matrix. Differential scanning calorimetry (DSC) showed a decrease in crystallization enthalpy and crystallinity of the wood flour‐plastic composites as compared with the neat PP and HDPE samples. The crystallinity of the FT cycled composites using the virgin plastics (vPP and vHDPE) increased; however, the composites with the recycled plastics decreased in comparison with corresponding control samples. In general, the properties of the composites were degraded significantly after the accelerated FT cycling. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

All‐wood biocomposites by partial dissolution of wood flour in 1‐butyl‐3‐methylimidazolium chloride

After cedar‐derived wood flour (WF) and bark flour (BF) were mixed with 1‐butyl‐3‐methylimidazolium chloride (BMIC) at 100°C, the obtained compounds with BMIC content 40 wt % were compression‐molded at 210°C to give WF/BMIC and BF/BMIC composites, respectively. The BMIC contained in the composites was twice extracted with ethanol at 60°C to afford WF/BMIC‐E and BF/BMIC‐E biocomposites, which were subsequently annealed at 200°C for 24 h to produce WF/BMIC‐A and BF/BMIC‐A biocomposites. The Fourier transform infrared spectroscopic analysis revealed that WF has a higher content of cellulose and a lower content of lignin than BF does, and that the BMIC content diminished by the extraction process. The scanning electron microscopy analysis showed that woody particles joined together by the compression molding of WF/BMIC and BF/BMIC compounds, and that the extraction of BMIC roughened the surface and the annealing again smoothed the surface due to the fusion of the residual BMIC and woody particles. The XRD measurements indicated that the annealing enhanced the crystallinity of cellulose component. The tensile properties and 5% weight loss temperature of the biocomposites were considerably improved by the extraction of BMIC and further by the annealing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of compatibilizer on morphology,thermal, and rheological properties of polypropylene/functionalized multi‐walled carbon nanotubes composite

Multi‐walled carbon nanotubes (MWCNTs) filled polypropylene (PP) composites were prepared by a corotating intermeshing twin screw extruder. To improve the dispersion of MWCNTs, the surface of MWCNT was modified with 1,10‐diaminodecane, and maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizer. Micrographs of well dispersed functionalized MWCNTs (diamine‐MWCNT) were observed due to the reaction between MA‐g‐PP and diamine‐MWCNT in PP/MA‐g‐PP/diamine‐MWCNTs composites. The different behaviors in crystallization and melting temperatures of PP/MA‐g‐PP/diamine‐MWCNTs composite were observed compared to PP and PP/neat‐MWCNT. Especially, the decomposition temperature of the composite was increased by 50°C compared to PP. PP/MA‐g‐PP/diamine‐MWCNTs composite showed the highest complex viscosity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

Effect of fiber pretreatment condition on the interfacial strength and mechanical properties of wood fiber/PP composites

The effect of fiber surface pretreatment on the interfacial strength and mechanical properties of wood fiber/polypropylene (WF/PP) composites are investigated. The results demonstrate that fiber surface conditions significantly influence the fiber–matrix interfacial bond, which, in turn, determines the mechanical properties of the composites. The WF/PP composite containing fibers pretreated with an acid–silane aqueous solution exhibits the highest tensile properties among the materials studied. This observation is a direct result of the strong interfacial bond caused by the acid/water condition used in the fiber pretreatment. Evidence from coupling chemistry, rheological and electron microscopic studies support the above conclusion. When SEBS‐g‐MA copolymer is used, a synergistic toughening effect between the wood fiber and the copolymer is observed. The V‐notch Charpy impact strength of the WF/PP/SEBS‐g‐MA composite is substantially higher than that of the WF/PP composite. The synergistic toughening mechanisms are discussed with respect to the interfacial bond strength, fiber‐matrix debonding, and matrix plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1000–1010, 2000