Flame retarded self‐reinforced polypropylene composites prepared by injection moulding

A method was elaborated to prepare flame retarded self‐reinforced polypropylene composites by injection moulding. The effect of intumescent flame retardant (FR) loading was comprehensively investigated on the morphology, flammability, and mechanical properties of the self‐reinforced polypropylene composites and compared with non‐reinforced counterparts of identical additive contents. Homogeneous distribution of both the reinforcing polypropylene fibres and the FR additive was achieved endowing significantly improved strength and stiffness accompanied with increased fire resistance. At 10% FR content, 37% reduction of peak of heat release rate, UL94 V‐2 rating, and LOI of 24.5 vol% were achieved without compromising the improved mechanical performance of the injection moulded self‐reinforced composites, ie, a 4‐fold increase of tensile strength and a 7‐fold increase of tensile modulus were reached compared with the non‐reinforced counterpart. At higher loading (15% FR), the FR properties improved further (LOI of 29.5 vol% was reached); however, due to the abrasive effect of the FR particles in the matrix, the structure of the reinforcing fibres tends to get damaged during the thermo‐mechanical processing, and thus their reinforcing efficacy deteriorated. It is demonstrated that the combination of polymer fibre reinforcement with other fillers (such as FRs) is advantageous and feasible even by injection moulding, but the balance between the individual attributed properties needs to be found.     

A review on potential development of flame retardant kenaf fibers reinforced polymer composites

Kenaf fibers have been extensively explored from the past few decades in polymer composites industries owing to its extensive adaptations, excellent properties together with its comparable mechanical properties to traditional glass fibers polymer composites. The combustibility or lowered flame retardancy hampered the diverse applications of kenaf fibers reinforced polymer composites, as it affects the mechanical strength and stiffness of composites during fire. Current review article intended to be a comprehensive source of published literature involving the flame retardants (FRs), types and applications of FRs and the fabrication of kenaf fibers reinforced polymer composites. This article will also provide a perfect data on the recent development of the FR kenaf fibers polymer composites with different FRs and explored its structural and semi‐structural industrial application for performing further research in this topic. Copyright © 2016 John Wiley & Sons, Ltd.     

Nanofibrillated cellulose: surface modification and potential applications

Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent.     

Role,effect, and influences of micro and nano‐fillers on various properties of polymer matrix composites for microelectronics: A review

Ever since the discovery of polymer composites, its potential has been anticipated for numerous applications in various fields such as microelectronics, automobiles, and industrial applications. In this paper, we review filler reinforced polymer composites for its enormous potential in microelectronic applications. The interface and compatibility between matrix and filler have a significant role in property alteration of a polymer nanocomposites. Ceramic reinforced polymeric nanocomposites are promising candidate dielectric materials for several micro‐ and nano‐electronic devices. Because of its synergistic effect like high thermal conductivity, low thermal expansion, and dielectric constant of ceramic fillers with the polymer matrix, the resultant nanocomposites have high dielectric breakdown strength. The thermal and dielectric properties are discussed in the view of filler alignment techniques and its effect on the composites. Furthermore, the effect of various surface modified filler materials in polymer matrix, concepts of network forming using filler, and benefits of filler alignment are also discussed in this work. As a whole, this review article addresses the overall view to novice researchers on various properties such as thermal and dielectric properties of polymer matrix composites and direction for future research to be carried out.     

Surface treatment of Basalt fiber for use in automotive composites

Balancing the performance, durability and safety requirements of automotive systems with the regulatory landscape in an environment of climate change has accelerated the search for sustainable fiber reinforced polymer composites for automobile structures. Glass fiber reinforced thermoplastic polymer composites (GFRP) are widely used in certain structures like front end modules and liftgate; However, they cannot be used in more demanding applications due to their low mechanical properties. Carbon fiber reinforced thermoplastic polymer composites (CFRP) are promising candidates for applications like bonnet, but their use is constrained by cost. Basalt fiber reinforced thermoplastic polymer composites (BFRP) are sustainable materials that can be positioned between GFRP and CFRP in terms of performance and cost-effectiveness. The mechanical performance of the BFRP depend on the quality of the fiber-matrix interface that aids in efficient load transfer from the matrix to the fiber. Typically, basalt fibers are inert in nature and need treatments to improve its adhesion to polymeric matrices. The major chemical treatments that are reviewed in this article include matrix functionalization, silane treatment, functionalized nanomaterial coating and plasma polymerization. The physical treatments reviewed include plasma treatment and milling. It is evident that chemically treating the basalt fiber with a functionalized nanomaterial yields BFRP with a good stiffness – toughness balance that can be used for challenging metal replacements as also in new emerging areas like sensing and 3D printing.     

Effects of polylactic acid and rPET minor components on phase evolution,tensile and thermal properties of polyethylene‐based composite fibers

High mechanical performance and partially biodegradable PE‐composite fibers modified with polylactic acid (PLA) and recycled polyethylene terephthalate (rPET) minor components were prepared using melt extrusion and hot drawing process. Rheological properties, morphology, tensile, and thermal properties were investigated. All blends exhibited shear thinning behavior except for starting PLA and rPET. PLA and rPET dispersed phases appeared as droplets in as‐extruded strand, and PLA droplets were mostly larger than those of rPET. The fibrillation of both PLA and rPET domains was achieved after further hot drawing as the fiber. The morphology and tensile properties of the fibers mainly depended on the types and contents of dispersed phases including draw ratios. The ultimate strength of the polymer fibers at draw ratio of 20 was more than 600 times higher than that of the as‐spun sample of the same composition. Remarkable improvement in secant modulus and ultimate strength was found for PE‐30PLA, but the drawing process of this composition encountered some difficulties and rough surface of the fiber was observed. The stiffness and tensile stress for PE‐10PLA‐10rPET fiber were clearly improved when compared with PE and PE‐10PLA. A decrease in thermal stability of PE/PLA composites was observed with increasing PLA content whereas additional presence of rPET significantly increased the stability of the composites both in nitrogen and in air. PE/PLA/rPET fiber possessing high stiffness with good thermal stability prepared in this work has high potential for being utilized as structural parts for load‐bearing applications.     

The use of zinc dimethacrylate functionalized graphene as a reinforcement in rubber composites

Zinc dimethacrylate functionalized graphene (Z‐GE), as reinforcing nanofiller for natural rubber (NR), was synthesized by liquid‐phase exfoliation and in situ method. The morphology and structure of Z‐GE were characterized to confirm the exfoliation and functionalization of GE. The NR/Z‐GE composites were prepared and investigated by mechanical analysis, crosslinked network analysis and the analysis of thermal conductivity. The results showed that the tensile strength, tear strength and modulus at 300% strain of NR/Z‐GE‐20 composites (contents 1.400 phr GE) were increased by 142%, 76% and 231% as compared with the pure NR, respectively. And the thermal conductivity of NR/Z‐GE‐30 composites is enhanced by 39% as that of the pure NR. This significant improvement is attributed to the formation of covalent crosslinked network and ionic crosslinked network and efficient interfacial interaction between GE and NR matrix. This method provides a new insight into the fabrication of multifunctional GE composites and enlarges its potential applications in high performance GE‐based rubber composites. Copyright © 2015 John Wiley & Sons, Ltd.     

Polylactide (PLA) and Highly Filled PLA - Calcium Sulfate Composites with Improved Impact Properties

Summary: Starting from gypsum as by-product of lactic acid fabrication process, novel high performance composites have been produced by melt-blending PLA and this filler after a previous specific dehydration performed at 500 °C for min. 1h. Due to PLA sensitivity towards hydrolysis, the utilization of β-anhydrite II (AII) as filler is a prerequisite. Characterized by attractive mechanical and thermal properties due to good filler dispersion throughout the polyester matrix, these composites are interesting in biodegradable rigid packaging or technical applications. Interestingly, tensile strength of PLA – AII composites proved remarkably high, e.g. higher than 35 MPa at 50 wt-% filler content. However a decrease of impact properties has been recorded. To increase the toughness of these composites while preserving high stiffness an impact modifier based on ethylene copolymer has been mixed with both the polymer matrix and AII by melt-compounding. The effectiveness of the impact modifier was confirmed in both neat PLA and AII-based composites. Addition of 5-10 wt-% impact modifier into highly filled composites (30 to 40 wt-% filler) leads to an attractively threefold increase of impact strength with respect to the compositions without modifier, remarkable thermo-mechanical performances and good filler dispersion.     

Microstructural design for enhanced mechanical property and shape memory behavior of polyurethane nanocomposites: Role of carbon nanotube,montmorillonite, and their hybrid fillers

The recent rapid development of technology has demanded smart materials with tailoring a bridge between macro properties and sophisticated micro and nano characteristic. Principally, shape memory polymers (SMPs) will come to play as an indispensable part of numerous aspects of human activity. Nevertheless, the low mechanical strength and thermal conductivity of SMPs have primarily restricted their applications. To impart shape memory behaviour and mechanical properties, we fabricated a series of composites by a feasible and commercial melt-mixing method. Thus, a series of fast heat-actuated shape memory polymer composite with greatly enhanced stretch-ability, mechanical stiffness, dynamic-modulus, rheological qualities, recovery and fixity ratio was prepared by incorporating multi-walled carbon nanotubes (CNT), montmorillonite (MMT) and CNT:MMT hybrid into thermoplastic polyurethane (TPU). Noteworthy, CNT-based specimens exhibited superior mechanical properties than those of MMT-based samples, and interestingly, the hybrid composites featured a synergistic effect due to the sacrificial role of MMT nanoplatelets for adjusting the dispersion of CNT nanotubes. Microstructural observations indicated that the crystallization percentages of the composites were generally higher than that of pristine TPU; therefore, the shape-memory performance of the specimens improved notably in the case of the hybrid composites owing to creating more interfacial zone with CNT:MMT nanoparticles as compared to other simple composites. This study proved that the simultaneous incorporation of CNT and MMT nanoparticles not only granted outstanding mechanical properties, but also improved the overall shape memory behaviour of the composites by systematical localization of the nanoparticles without any functionalization or modification.     

Biodegradable polyesters reinforced with surface-modified vegetable fibers

Flax fibers are investigated as reinforcing agents for biodegradable polyesters (Bionolle and poly(lactic acid) plasticized with 15 wt.-% of acetyltributyl citrate, p-PLLA). The composites are obtained either by high temperature compression molding fiber mats sandwiched between polymer films, or by batch mixing fibers with the molten polymer. Fibers in composites obtained by the latter method are much shorter (140-200 microm) than those of the mats (5,000 microm). Flax fibers are found to reinforce both p-PLLA and Bionolle (i.e. tensile modulus and strength increase) when composites based on fiber mats are investigated. Conversely, analogous composites obtained by batch mixing show poor mechanical properties. The observed behavior is attributed to the combined effect of fiber length and fiber-matrix adhesion. If flax fibers with a modified surface chemistry are used, the strength of short fiber composites is seen to improve significantly because the interface strengthens and load is more efficiently transferred. Appropriate surface modifications are performed by heterogeneous acylation reactions or by grafting poly(ethylene glycol) chains (PEG, molecular weight 350 and 750). The highest tensile strength of p-PLLA composites is reached when PEG-grafted flax fibers are used, whereas in the case of Bionolle the best performance is observed with acylated fibers.     

In situ latex synthesis of magnetic polymer nanocomposites for application in magnetorheological materials

A new magnetic polymer nanocomposite based on Fe₃O₄ nanoparticles and nature rubber was prepared by the in situ latex method. This process was fast, versatile, reliable, safe, environmentally friendly, and inexpensive. The magnetorheological effect and mechanical properties of magnetic polymer nanocomposites were investigated in detail. The tensile strength of magnetic polymer nanocomposites without other reinforcing fillers was about 14.6 MPa. At the same time, the relative and absolute magnetorheological effect was about 365.0% and 3.64 MPa, respectively, which were almost 10 times with respect to other magnetic polymer nanocomposites based on nature rubber. Furthermore, the relationships between microstructure and mechanical behavior of magnetic polymer nanocomposites were simulated and discussed by the numerical treatment of a new theoretical model associated with finite element analysis for explaining the micro‐mechanism of magnetic polymer nanocomposites with high performance. The work did not only provide a universal route for the rational design and preparation of magnetic polymer nanocomposites with simultaneously high magnetic sensitivity and mechanical properties for various applications but also propose a new method to improve dispersion of magnetic particles in nature rubber for various applications.     

Nanoarchitectured Graphene‐Based Supercapacitors for Next‐Generation Energy‐Storage Applications

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high‐energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy‐storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double‐layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene‐based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene‐based asymmetric supercapacitors. The challenges and prospects of graphene‐based supercapacitors are also discussed.     

Nanoclay modified silica phenolic composites: mechanical properties and thermal response under simulated atmospheric re‐entry conditions

Ablative nanocomposites based on nanoclay‐dispersed addition curable propargylated phenolic novolac (ACPR) resin, reinforced with chopped silica fiber, were investigated for their thermal response behavior under simulated heat flux conditions corresponding to typical atmospheric re‐entry conditions. Organically modified nanoclay (Cloisite 30B) was incorporated to different extents (1–10%) in the ACPR resin matrix containing silica fiber to form the composite. The composites displayed optimum mechanical properties at around 3 wt% of nanoclay loading. The resultant composites were evaluated for their ablative characteristics as well as mechanical, thermal and thermo‐physical properties. The reinforcing effect of nanoclay was established and correlated to the composition. The mechanical properties of the composites and its pyrolysed product improved at moderate nanoclay incorporation. Plasma arc jet studies revealed that front wall temperature is lowered by 20°C and that at backwall by 10–13°C for the 3 wt% nanoclay‐incorporated composites due to impedance by nanoclay for the heat conduction. Nanoclay diminished the coefficient of thermal expansion by almost 50% and also reduced the flammability of the composites. The trend in mechanical properties was correlated to the microstructural morphology of the composites. The nanomodification conferred better strength to the pyrolysed composites. Copyright © 2014 John Wiley & Sons, Ltd.     

The role of organoclay on the properties of Polymethylsilsesquioxane: A systematic study

In this study, an attempt is made to improve the properties of PMSQ, an organosilicone polymer which possesses distinguished properties, through an easy and facile route by the inclusion of organically modified montmorillonite clay. PMSQ-clay composites were prepared by solution blending of the components initially and then heat curing under load. The effect of clay content, varied at 5–40 wt.%, on mechanical, thermal and dynamic mechanical properties was evaluated and the optimum was obtained for 20%. Morphology investigation as well as microstructure analysis revealed intercalated to exfoliated morphology of PMSQ-clay composite. An appreciable improvement in mechanical properties of PMSQ, compressive strength and impact strength in particular, was achieved by clay inclusion up to 20%. The properties declined at ≥ 30% clay loading. The composites showed increased thermal stability compared to unmodified PMSQ up to 400 °C. Also, increase in clay content accelerated conversion to ceramic SiOC. PMSQ-clay composites exhibited good visco-elastic characteristics with higher T_g probably due to enhanced polymer-clay interactions. Thus, a simple and viable method to enhance the mechanical and thermal characteristics of PMSQ by way of preparing its composite with the reinforcing filler organoclay is demonstrated here.     

Nanomechanical properties of silica-coated multiwall carbon nanotubes-poly(methyl methacrylate) composites

The mechanical properties of polymer composites, reinforced with silica-coated multiwall carbon nanotubes (MWNTs), have been studied using the nanoindentation technique. The hardness and the Young's modulus have been found to increase strongly with the increasing content of these nanotubes in the polymer matrix. Similar experiments conducted on thin films containing MWNTs, but without a silica shell, revealed that the presence of these nanotubes does not affect the nanomechanical properties of the composites. While carbon nanotubes (CNTs) have a very high tensile strength due to the nanotube stiffness, composites fabricated with CNTs may exhibit inferior toughness. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4 wt % of the silica-coated MWNTs, display a maximum hardness of 120 +/- 20 MPa, and a Young's modulus of 9 +/- 1 GPa. These are respectively 2 and 3 times higher than those for the polymeric matrix. Here, we describe a method for the silica coating of MWNTs. This is a simple and efficient technique, adaptable to large-scale production, and might lead to new advanced polymer based materials, with very high axial and bending strength.     

The addition of clay on the mechanical properties of surface‐treated CF‐filled PA66 composites

Polyamide 66 (PA66) composites filled with clay and carbon fiber (CF) were prepared by twin‐screw extruder in order to study the influence of nanoparticle reinforcing effect on the mechanical behavior of the PA66 composites (CF/PA66). The mechanical property tests of the composites with and without clay were performed, and the fracture surface morphology was analyzed. The results show that the fracture surface area of the clay‐filled CF/PA66 composite was far smoother than that of the CF/PA66 composite, and there formed a tense interface on the CF surface after the addition of clay. The tensile and flexural strength of CF/PA66 composites with clay was improved. The impact strength decreased because of the high interfacial adhesion. In conclusion, the addition of clay favored the improvement of the higher interface strength and so had good effect on improving the tensile and flexural properties of the composites. Copyright © 2017 John Wiley & Sons, Ltd.     

Study on the evaluation of mechanical and thermal properties of natural sisal fiber/general polymer composites reinforced with nanoclay

Composite materials, made by replacing traditional materials, are used because of their capability to produce tailor-made, desirable properties such as high tensile strength, low thermal expansion, and high strength to weight ratio. The need for the development of new materials is essential and growing day by day. The natural sisal/general polymer (GP) reinforced with nanoclay composites has become more attractive due to its high specific strength, light weight, and biodegradability. In this study, sisal–nanoclay composite is developed and its mechanical properties such as tensile strength, flexural strength, and impact strength are evaluated. The interfacial properties, internal cracks, and internal structure of the fractured surface are evaluated using scanning electron microscope. The thermal disintegration of composites are evaluated by thermogravimetric analysis. The results indicate that the incorporation of nanoclay in sisal fiber/GP can improve its properties and can be used as a substitute material for glass fiber-reinforced polymer composites.     

Radar transparent glass fabric reinforced polyetherimide/Cloisite 30B nanocomposites

High performance radar transparent materials (RTMs) are important materials for the fabrication of radomes, nosecones, etc. of high velocity aerospace vehicles. RTMs with good mechanical performance and temperature capability are required for such applications. Toward this, fabric reinforced nano‐reinforced matrix composites (FRNCs), using reinforcing E‐glass fabric in Cloisite 30B reinforced polyetherimide (PEI) nanocomposite matrix (GNRPEI), was prepared. The properties of GNRPEI were evaluated and compared with E‐glass fabric reinforced PEI composites (GRPEI) with special reference to their radar transparent character for aerospace applications. Tensile and flexural properties along with interlaminar shear strength of GRPEI were observed to be lower than those of GNRPEI. Thermal behavior of both the composites was similar in differential scanning calorimetry and thermal gravimetric analysis. But, in dynamic mechanical analysis, an increase in storage modulus and decrease in loss tangent were observed in GNRPEI compared to GRPEI. The values of dielectric constant and loss tangent of GNRPEI were lesser than those of GRPEI, but no significant difference was observed in the values of transmission and reflection losses for both the composites at 8–12 GHz frequency. FRNCs, based on organoclay reinforced PEI matrix, hold good promise as high performance RTMs. Copyright © 2010 John Wiley & Sons, Ltd.     

Biomimetic chitosan‐treated clay–elastomer composites with water‐responsive mechanically dynamic properties

Biomimetic hydrophobic polymer composites with water‐responsive mechanically adaptive behaviors were successfully prepared using hydrophilic chitosan‐treated clay (chi‐clay) as the water‐activated, pH‐sensitive and reinforcing phase and elastomeric thermoplastic polyurethane (TPU) as the matrix. Structural characterization, swelling tests in three representative solutions with different pH values, and dynamic mechanical analysis under wet and dry conditions were performed on the resultant chi‐clay‐TPU composites with varying chi‐clay contents. The results showed that the equilibrium swelling degree of TPU increased significantly with increasing chi‐clay content and that water transportation in all the composites followed Fickian diffusion mechanism. The presence of chi‐clay provided remarkable enhancement of the storage modulus of TPU and offered water‐responsive changes of the modulus. Such changes increased with chi‐clay content and were pH‐sensitive, with the acidic condition rendering the largest modulus difference. These water‐responsive polymer composites may find potential applications in biomedical fields and beyond. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 55–62     

刚性微粒填充高聚物的宏观本构关系

用微观力学和统计方法研究了含损伤过程的刚性粒子填充高聚物的非线性本构关系．在材料的变形过程中，粒子与基体间界面的开裂引发微孔洞的成核与长大，这虽然弱化了材料的宏观力学性能，但是带来了宏观本构的非线性效应，这为材料的增韧奠定了基础．该文分析了刚性粒子对材料的强化作用和微孔洞演化对材料的弱化作用，以及这两种竞争机制的耦合效应对宏观本构关系的影响，并从理论上给出了界面强度，粒径分散度，平均粒径等参量对材料宏观力学行为影响的定量分析结果．