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

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

Study and characterization of composites materials based on polypropylene loaded with olive husk flour

In Algeria, a significant quantities of olive husk are rejected to nature causing by the way major nuisances to environment, to give us a reason for which our work is focused on the valorization of this waste by its incorporation in a polypropylene matrix. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymeric matrix. To improve interfacial adhesion, two modes of chemical treatments were done using vinyltriacetoxysilane (VTAS) and maleic‐anhydride‐polypropylene (PPMA) compatibilisant agent. Several formulations of PP filled with 10 and 20% by mass of olive husk flour treated (OHFT) and untreated (OHFUT) were prepared. The chemical modification of olive husk flour was studied by Fourier transform infrared (FTIR) spectroscopy. The tensile properties, the water‐absorption behavior, the thermal degradation properties, and crystallinity of the composites were investigated. It was found that, the incorporation of the treated and untreated OHF improves the thermal stability of the composites. However, the use of the compatibilizer agent PPMA leads to a better thermal stability compared with the treatment of the OHF by the VTAS and the OHFUT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Viscoelastic behavior in a hydroxyl‐terminated polybutadiene gum and its highly filled composites: Effect of the type of filler on the relaxation processes

Investigations have been ongoing to learn the rheological and/or mechanical behavior of composite solid propellants based on hydroxyl‐terminated polybutadiene (HTPB). The mechanical properties of these materials are related to the macromolecular structure of the binder as well as to the content and nature of the fillers. The viscoelastic behavior of an HTPB binder and its composites with different types of fillers was surveyed by dynamic mechanical analysis over a wide range of temperatures. This technique has clearly demonstrated a two‐phase morphology developed in these systems. The temperature location, intensity, and apparent activation energy of the distinct relaxations are discussed. The dependency of the relaxation processes on filler content in a series of composites has elucidated the interactions between the filler particles and the existing hard‐ and soft‐segment domains within the polyurethane matrix. It was observed that the nature of the filler significantly affects the relaxation process associated with the hard‐segment domains of the polymeric structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1705–1712, 2003     

The influence of structural order of anthracite fillers on the curing behavior,morphology, and dynamic mechanical thermal properties of epoxy composites

This article concerns the study of polymer composites with anthracite fillers of various structural order. Raw Svierdlovski anthracite of turbostratic structure and the anthracite thermally treated at 2,000°C of graphite‐like structure were used as fillers of low‐molecular‐weight diglycidyl ether of bisphenol A cross‐linked with aliphatic amine. Two anthracites of extremely different structures were compared to natural graphite that is composed of well‐ordered graphene sheets. Systematic studies of the influence of the structure of anthracite filler on the curing behavior, morphology, dynamic mechanical thermal properties, and thermal stability of epoxy composite were performed. It was found that the structure of anthracite filler affects the cross‐linking reactions of the epoxy matrix as well as the morphology of the composites and their viscoelastic properties. Raw anthracite added to epoxy matrix had a visible effect on the activation energy and differential scanning calorimeter parameters of the curing process, in contrast to the epoxy matrix modified with anthracite heated at 2,000°C. On the contrary, the effect of anthracite on dynamic mechanical behavior of composites is more evident when the anthracite prepared at 2,000°C was used as a filler. POLYM. COMPOS., 36:336–347, 2015. © 2014 Society of Plastics Engineers     

An investigation on the mechanical and dynamic rheological properties of single and hybrid filler/polypropylene composites based on talc and calcium carbonate

Some results of experiments on the mechanical and rheological properties of mineral filled polypropylene were presented. Single filler and hybrid filler composites of talc and calcium carbonate (CaCO₃) were prepared in a co‐rotating twin‐screw extruder. The effect of filler type, filler content, and coupling agent on the mechanical and rheological properties of the polypropylene were studied. The coupling agent was maleic anhydride‐grafted polypropylene (PP‐g‐MA). It was found that the mechanical properties are affected by filler type, filler concentration, and the interaction between filler and matrix. The tensile strength of the composite is more affected by the talc while the impact strength is influenced mostly by CaCO₃ content. The elongation at break of PP/CaCO₃ composites was higher than that of PP/talc composites. The incorporation of coupling agent into PP/mineral filler composites increased the mechanical properties. Rheological properties indicated that the complex viscosity and storage modulus of talc filled samples were higher than those of calcium carbonate filled samples while the tan δ was lower. The rheological properties of hybrid‐filler filled sample were more affected by the talc than calcium carbonate. The PP‐g‐MA increased the complex viscosity and storage modulus of both single and hybrid composites. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Prediction of viscoelastic behavior of interphase in polypropylene‐chopped rice husk composites for β‐relaxation domain

The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin‐screw extruder, with maleic anhydride‐grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E′) was found to be increased progressively, whereas the mechanical loss factor (tan δ) decreased in a nonlinear manner. A self‐consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three‐phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of filler loading and coconut oil coupling agent on properties of low‐density polyethylene and palm kernel shell eco‐composites

Palm kernel shell (PKS), a waste from the oil palm industry, has been utilized as filler in low‐density polyethylene (LDPE) eco‐composites in the present work. The effect of PKS content and coconut oil coupling agent (COCA) on tensile properties, water absorption, and morphological and thermal properties of LDPE/PKS eco‐composites was investigated. The results show the increase of PKS content decreased the tensile strength and elongation at break, but increased the tensile modulus, crystallinity, and water absorption of eco‐composites. The presence of COCA as coupling agent improved the filler‐matrix adhesion yield to increase the tensile strength, tensile modulus, crystallinity, and reduced water absorption of eco‐composites. The better interfacial adhesion between PKS and LDPE with the addition of COCA was also evidenced by scanning electron microscopy studies. J. VINYL ADDIT. TECHNOL., 22:200–205, 2016. © 2014 Society of Plastics Engineers     

Studies on High Density Polyethylene Reinforced with Phosphate Ore Particles: Thermal,Rheological, Mechanical and Morphological Properties

Calcareous phosphate ore can be utilized as a cost-effective alternate to other inorganic fillers for polymer-based composites. In this study, composites of high-density polyethylene and phosphate rock ore particles were prepared by melt blending and injection-molding techniques. The thermomechanical, rheological, and mechanical properties of these composites were studied to investigate the effect of filler loading on their functionality. The reduction in the crystallinity of phosphate ore/high-density polyethylene composites was observed compared to that of the neat high-density polyethylene. The relative crystallinity of the neat high-density polyethylene decreases from 53 to 30% by the addition of 2.5–15 wt% of ore, respectively. Comparison of the linear dynamic viscoelasticity for the neat high-density polyethylene and the ore-filled composites shows t a monotonic increase in both storage modulus and loss modulus with the increasing frequency. The viscoelastic behavior at high frequencies remains unaffected. However, at lower frequencies, both G′ and G″ exhibit diminished frequency dependence. It was also observed that higher filler content decreased the tensile and impact strength, whereas the Young's modulus of the composites increased. The morphological analysis shows relatively weak interaction between the fillers and the matrix because of agglomeration which in turn adversely affects the mechanical properties of the composites.     

Preparation and properties of bio‐nanoreinforced composites from biodegradable polymer matrix and cellulose whiskers

Crystalline cellulose was extracted from one of the cheapest source; grass by alkali, acid, and mechanical treatments. To evaluate the reinforcing effect of this filler, biodegradable polymer matrix, polylactic acid (PLA) was used and samples were prepared at different concentrations. The modified whiskers were also used as filler to examine the effect on mechanical properties. Crystallinity, thermal behavior, surface morphology and functional group variation was monitored through, XRD, TGA, SEM, and FTIR respectively. The properties were largely depending on the concentration of filler whereas; modification of hydroxyl groups did not exhibit remarkable change in mechanical properties. Thermal resistance was decreased in comparison of neat matrix and reduction in crystallinity was also observed for composites, regardless of filler nature. It was thought that the hydrophilicity of cellulose could be altered by modifying its hydroxyl groups, thereby promoting dispersion. However, the possibility of phase separation was increased, and the thermal stability of the composites gradually decreased with increasing filler load in the matrix. In the examined systems, it was observed that improvement of reinforcing capacity may not only depend on the chemical compatibility between matrixes but also some compositional and physical parameters may be responsible for variation in properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sugar palm fiber/polyester nanocomposites: Influence of adding nanoclay fillers on thermal,dynamic mechanical,and physical properties

In this research, nanoclay used as filler in sugar palm‐reinforced composites was investigated by the physical, thermal, and dynamic mechanical properties. Various concentrations of nanoclay were used to fabricate composites by using hand lay‐up technique, followed by hot compression molding with naturally woven sugar palm fiber‐reinforced in polyester matrix. Among various weight concentrations such as 1–5% of nanoclay, it was found that 2% nanoclay‐filled composite (NC) demonstrated the best balance of thermomechanical properties and significantly enhanced the composite. DMA demonstrated that 2% nanoclay content resulted in improved viscoelastic behavior and higher glass transition temperature (T_g) of the composites. TGA also showed improvement in properties, whereas 3% nanoclay‐filled composite showed superior onset temperature, and 5% nanoclay‐filled composite exhibited highest remaining residue. The nanoclay filler was very effective to fill the porous structure and maintain the thickness stability. The thickness swelling was reduced with increasing amount of nanoclay in composites. Overall, the addition of nano clay improved thermal and physical properties of sugar palm‐reinforced polyester composite. J. VINYL ADDIT. TECHNOL., 26:236–243, 2020. © 2019 Society of Plastics Engineers     

Influence of incorporating CaCO3 into room temperature vulcanized silicone sealant on its mechanical and dynamic rheological properties

Silicone sealants with low modulus and high elongation were prepared by using ketoxime silane as chain extender agent, and a novel silane coupling agent acting as adhesion promoting agent was synthesized. Mechanical properties of vulcanized polydimethylsiloxane (PDMS) filled with large amounts of carbonate calcium (CaCO₃) and dynamic viscoelastic properties of unvulcanized samples were investigated through electronic multifunctional tensile tests, dynamic mechanical analyzers, and dynamic rheological measurements. The results of mechanical tests indicate that diminishing the particle diameter size, narrowing the particle diameter distribution, and increasing the filler amount lead to a relative high tensile strength and modulus at 100% elongation, but a relative low elongation at break. The reasons for these are believed to be the evolution of molecular interactions and the formation of additional physical crosslinking induced by the filler network. Compared to virgin PDMS, there is a significant elevation of glass transition temperature with filler addition. On the other hand, the results of dynamic rheological measurements reveal that as filler amount increases, the span of the linear viscoelastic region in which dynamic storage modulus (G′) is constant in low strain amplitude narrows. However, a characteristic plateau phenomenon appears in low frequency regions together with increasing the width and height of the modulus plateau. This phenomenon is also ascribed to the formation of a filler network due to filler–polymer and filler–filler interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2027–2035, 2007     

Preparation and characterization of polypropylene/solid‐state organomodified montmorillonite nanocomposites

A novel organomodified montmorillonite prepared by solid‐state method and its nanocomposites with polypropylene were studied. The interaction between modifying agent and montmorillonite was investigated by X‐ray diffraction (XRD) analysis, contact angle determination, and Fourier‐transform infrared spectroscopy. The results showed that the modifying agent behaves as an effective intercalating agent, enlarging the interlayer spacing of montmorillonite and making montmorillonite more hydrophobic. Polypropylene/solid‐state organomodified montmorillonite composites were prepared by melt‐mixing method. The dispersion of the silicates was investigated by XRD analysis and transmission electron microscopy. It was found that the nanocomposites are formed with solid‐state organomodified montmorillonite and polypropylene. The thermogravimetric analysis and differential scanning calorimetry results showed that the organoclay could enhance the thermal stability and decrease the relative crystallinity of polypropylene. Mechanical and rheological tests indicated that the organoclay improves the mechanical properties but has no obvious effect on rheological properties of polypropylene. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Studies on fly‐ash‐filled natural rubber modified with cardanol derivatives: Processability,mechanical properties,fracture morphology,and thermal decomposition characteristics

Fly ash, a by‐product of thermal power stations, was used as a filler in natural rubber (NR) in presence of 5–10 phr of phosphorylated cardanol prepolymer (PCP) and hexamethylene tetramine cured PCP (PCPHM). The compositions modified with the cardanol‐based resins showed lower power consumption for mixing, lower cure time, improved tensile properties and tear strength, and higher thermal stability. Scanning electron microscopy of the fracture surfaces of the tensile‐failed specimens showed finer and more uniformly distributed filler particles in the rubber matrix in the presence of PCP/PCPHM. The cardanol‐based resins are expected to function as a coupling agent between the filler and rubber leading to the improvement in mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4801–4808, 2006     

Toughening linear low‐density polyethylene with halloysite nanotubes

Linear low‐density polyethylene (LLDPE)‐based composites were prepared through melt compounding and hot pressing using both untreated and treated halloysite nanotubes (HNT) up to filler contents of 8 wt% to assess the role of the filler exfoliation and surface treatment on the thermal, mechanical, and rheological properties of the resulting composites. The addition of treated nanoparticles resulted in a better dispersion of the filler within the matrix, as confirmed by observations conducted at scanning and transmission electron microscopies. A decrease in both complex viscosity and shear storage modulus was recorded for all LLDPE‐HNT nanocomposites in the molten state. Differential scanning calorimetry analysis evidenced that HNT addition produced an increase of the crystallization peak temperature, while thermogravimetric analysis showed a remarkable improvement of the thermal stability with the nanofiller content. The addition of treated HNT nanoparticles induced better improvements in elastic modulus and tensile properties at break without significant loss in ductility. The fracture toughness, evaluated by the essential work of fracture approach, showed remarkable improvements (up to a factor of 2) with addition of treated HNT. Conversely, incorporation of untreated HNT produced an adverse effect on the fracture toughness when considering the nanocomposite filled with 8 wt% HNT. Both creep tests and dynamic mechanical analyses showed an overall enhancement of the viscoelastic properties due to addition of HNT, revealing higher improvements in nanocomposites added with treated HNT. POLYM. COMPOS., 36:869–883, 2015. © 2014 Society of Plastics Engineers     

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     

Mechanical,thermal, and rheological behavior of ethylene methyl acrylate‐MWNT nanocomposites

Mechanical, thermal, and rheological properties of ethylene methyl acrylate (EMA) composites reinforced with multiwalled carbon nanotubes (MWNTs) have been reported here. Morphological analyses revealed that MWNTs are more uniformly dispersed in EMA upto 3.5 wt% MWNTs loading. Uniform dispersion of MWNTs in EMA matrix leads to decreased crystallinity and increased crystallite size. These are reflected in the mechanical and thermal properties of the composites. The storage moduli of the composites significantly increase by the incorporation of MWNTs, particularly at higher temperatures. The nanocomposites register a slightly higher viscosity than that of neat EMA depending on the contents of MWNTs. Storage modulus (in dynamic shear) increases especially at higher frequency levels due to increased polymer–filler interactions. Dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of the nanocomposites. The morphology correlates well with the dynamic rheological characteristics of these nanocomposites. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Graphene nanoplatelet‐reinforced semi‐crystal poly(arylene ether nitrile) nanocomposites prepared by the twin‐screw extrusion

Graphene nanoplatelet reinforced semi‐crystal poly(arylene ether nitrile) (PEN/GN) nanocomposites were prepared by an economically and environmentally friendly method of twin‐screw extrusion technique. The feasibility of using PEN/GN nanocomposites was investigated by evaluating their thermal behaviors, mechanical, and morphological properties. Thermal studies revealed that GN could act as nucleating agents but decreased the whole crystallinity in/of PEN/GN nanocomposites. Mechanical investigation manifested that GN had both strengthening effect (increase in flexural modulus and strength) and toughening effect (rise in the elongation and impact strength) on the mechanical performance of semi‐crystal PEN nanocomposites. Heat treatment can further increase their mechanical performances due to the increased crystallinity and release of inner stress. With the small addition of GN (<5 wt%), the morphology of PEN was changed from brittle to ductile, and GN showed good dispersion and adhesion in/to the PEN matrix. This work shows that in the semi‐crystal polymer/filler systems, besides the dispersion states of fillers and interactions between fillers and polymer matrices, the crystallinity of the nanocomposites affected by the existence of filler and the residual stress are also two key factors determining the mechanical properties. POLYM. COMPOS., 35:404–411, 2014. © 2013 Society of Plastics Engineers     

Effects of a titanate coupling agent on the mechanical and thermo‐physical properties of talc‐reinforced polyethylene compounds

An experimental study was carried out to investigate the effects of a titanate coupling agent on the mechanical properties, moisture absorption, and thermal conductivity of talc‐filled high‐density polyethylene (HDPE). Talc (0–35 wt %) was used as reinforcement particulate filler in an HDPE matrix and samples were prepared in a micro‐compounder and an injection molding machine. Isopropyl tri(dioctyl)phosphate titanate (0.5 wt %) was used as coupling agent. Composites with and without coupling agent were evaluated for changes in mechanical and thermo‐physical properties, morphology, and void content. Addition of the titanate coupling agent most often resulted in an increase in stiffness and tensile strength. Furthermore, both the void content and the elongation at break of composites were reduced. Results also showed that the coupling agent had no effects on the thermal conductivity, thermal diffusivity, and specific heat capacity of the composites. In addition, it was observed that the coupling agent was more effective at low concentrations of filler. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40449.     

Effect of filler geometry on viscoelastic damping of graphite/aramid and carbon short fiber‐filled SBR composites: A new insight

An investigation on the effect of filler geometry/shape on the dynamic mechanical properties of polymers was conducted. The viscoelastic damping matrix chosen was SBR and the fillers chosen were graphite, aramid, and carbon short fibers. The study was conducted by taking a control base compound of 20 parts N330 carbon black‐filled styrene butadiene rubber (SBR). Dynamic mechanical thermal analyzer was used to investigate the viscoelastic damping of the rubber composites at low dynamic strain levels. Compressive hysterisis at moderate degree of strain were evaluated for all the composite samples to probe into their high strain static damping properties. SEM was used to investigate the matrix‐fiber interaction and distribution of the fillers. Investigations demonstrated that the matrix‐filler interface plays a major role in energy dissipation. The amount of interface was analyzed by considering the half height width of tan δ peak. Fiber matrix interaction parameter was calculated from the tan δ_max values for matrix and composite. It was observed the interaction parameter and the low strain tensile stress values register similar trend. Aramid short fibers were most effective in more energy dissipation than other fillers under consideration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The role of m‐phenylenebismaleimide (BMI) in reactive processing of poly(propylene)/magnesium hydroxide composites, 3. Analysis of interphase structure development

In the first and second parts of this series, the effect of m‐phenylenebismaleimide (BMI), processing temperature and a lubricant (a fatty acid ester/amide blend) on the mechanical and rheological properties of poly(propylene) (PP)/magnesium hydroxide composites was investigated. The third part focuses on interactions between BMI and the magnesium hydroxide and between the BMI and PP matrix. It has been shown that interaction between BMI and the filler is via an amide carboxylate together with possible polymerisation at the filler surface. Interaction of BMI with the PP matrix is via addition of PP macro‐radicals, produced via thermo‐mechanical degradation, to the maleimide alkenes of BMI. Greater crosslink density in the interphase region than in the bulk matrix is considered to result in a reduction of crystallinity within this region. This is manifested as a significant improvement in composite toughness relative to the equivalent unmodified composite.