Lightweight Polymer Composites Research Articles

Mechanical properties and microstructure of lightweight polymer composites containing mono and hybrid fillers sourced from recycled solid wastes

This paper presents the development of lightweight polymer composites containing various solid wastes as fillers. This research is conducted to formulate mix proportions of polymer composite using unsaturated polyester resin as binder and waste tyre rubber crumb, recycled polyethylene terephthalate (PET) flakes and fly ash as fillers. Effects of various volume fractions of rubber crumb, PET flakes and fly ash and their combinations on 3 days compressive strength and density of the polymer composites are studied and a number of optimum mixes are selected for further study. Compressive strength, flexural strength and toughness of the above optimum mixes are measured at 3, 14 and 28 days. The effect of jute fabric as reinforcing layer on flexural strength and toughness of polymer composite is also studied. Microstructure analysis is conducted to investigate the polymer matrix and matrix-fillers interface of the composites. The optimum mix proportions are developed based on usage of least binder and high volume of filling materials, having lightweight and appreciable compressive strength. Results show that the 28-day density and compression strength of polymer composites are in the range of 1072 to 1616 kg/m3 and 15 to 62 MPa, respectively. These values are well below the American Concrete Institute (ACI)’s lightweight concrete density of 1850 kg/m3 and compressive strength of 17.5 MPa. The combined use of fly ash with rubber crumb or PET flakes improved the compressive and flexural strengths of polymer composites compared to the use of rubber crumb or PET flakes alone. The use of jute fabric increased the flexural strength and toughness of polymer composites. Microstructural analysis revels no additional substance besides binder and fillers, indicating no reaction of fillers with the resin in the composite.

Synthesis and characterization of natural fiber reinforced laminated thermoplastic composite

As increase in the use of eco-friendly, natural fibers are used for the reinforcement of polymer composites which has the light weight and low-cost polymer composites with better mechanical properties which offers exceptional properties over glass fiber. In this work, Basalt fiber reinforced Polypropylene (PP) laminated composite was manufactured by the compression moulding process. The variations of impact, flexural and compression strength and modules of the composite according to the number of basalt fiber layers were investigated. Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX) conducted on the surface of the composite reveal the superior interfacial linkage between the basalt fiber and PP matrix. Hence, this offers a comprehensive discussion on synthesis and characterization of basalt fiber with polypropylene reinforced laminated thermoplastic composite.

Constructing nanopores in poly(oxymethylene)/multi-wall carbon nanotube nanocomposites via poly(l-lactide) assisting for improving electromagnetic interference shielding

Lightweight and high-performance conductive polymer composites (CPCs) have attracted much attention for electromagnetic interference (EMI) shielding. Herein, the porous structure was constructed in poly(oxymethylene)/multi-wall carbon nanotube (POM/MWCNT) nanocomposites via assisting by poly(l-lactide) (PLLA). First, the POM/PLLA/MWCNT (S-PMLNT) nanocomposites were obtained by melt mixing and compression molding. Second, the nanoporous POM/MWCNT (P-PMNT) nanocomposites were fabricated by selectively dissolving PLLA, solvent exchanging and freeze-drying. Because of well miscible between PLLA and POM, the homogeneous nanopores could be successfully fabricated in the P-PMNT composites by removing the PLLA phase. The multiple reflections and scattering of microwaves happened on the walls of these nanopores, which endowed the P-PMNT nanocomposites having higher EMI shielding effectiveness (SE) in comparison of the S-PMLNT nanocomposites, although the P-PMNT nanocomposites exhibited the lower electrical conductivity. For example, the S-PMLNT samples with 10 wt% MWCNTs showed an EMI SE of 48.1 dB and an electrical conductivity of 333 S/m, which changed to 58.6 dB in EMI SE and 125 S/m in electrical conductivity after removing PLLA phase. Furthermore, the P-PMNT10 nanocomposites had outstanding the EMI normal SE (SE/d) of 29.3 dB mm−1 and the EMI specific shielding effectiveness (SSE/d) of 344.4 dB cm2 g−1 because of their low density. In addition, the P-PMNT nanocomposites maintained high compression and tensile strength simultaneously.

Characterization of untreated and alkali treated natural fibers extracted from the stem of Catharanthus roseus

The present investigation deals with the study of untreated and alkali treated natural fibers extracted from the stem of Catharanthus roseus. The physical, chemical, crystallinity, mechanical, wettability, thermal, and surface characteristics were analyzed for untreated and alkali treated Catharanthus roseus fibers (CRFs). The results showed that chemical treatment removed excess amorphous contents such as hemicellulose, lignin and wax contents thereby there was an enhancement in tensile strength, crystalline index, and surface roughness. The char residue upon thermogravimetric analysis got increased from 25.2% to 39.6% for untreated and alkali treated CRFs respectively. The alkali treated CRF showed lesser contact angle which proved its improved wettability in the liquid phase. Thus the improvement in the characteristics of the alkali treated CRF can make it useful for developing lightweight polymer composites.

Mechanical and Tribological Properties of Polyimide Composites for Reducing Weight of Ultrasonic Motors

The travelling waves ultrasonic motors (TWUM) with nonmagnetic, large torque, high precision and simple structure was driven by frictional force, which had been applied aerospace, intelligent and precise instruments. In order to reduce the total weight of TWUM, the phosphor bronze stator with the biggest density among the all parts of TWUM (8.89 g/cm3) were substituted with light weight polymer or polymer composites. This study designed and prepared one types of low density polyimide (PI) composite (1.41g/cm3) reinforced with carbon fibers (CF) which can reduce the weight of stator over 85%. Importantly, this PI composite can meet the main requirements of TWUM, such as high elastic modulus, wear resistance, and suitable friction coefficient. The output stalling torque of TWUM with CF/PI stator still have 0.22 N·m (18.3% compared with TWUM with phosphor bronze stator). Moreover, this study systematically investigated the mechanical and tribological properties of CF/PI composite. For comparison, the pure PI, polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) were also analyzed to reveal the wear mechanisms. The experimental results indicated that CF/PI had better wear resistance and lower friction coefficient than other polymer sliding against Si3N4. This light weight polymer composites would be an ideal candidate to reduce the weight of TWUM, which can broaden the lightweight application in the field of aerospace.

Mesoporous Highly-Deformable Composite Polymer for a Gapless Triboelectric Nanogenerator via a One-Step Metal Oxidation Process.

The oxidation of metal microparticles (MPs) in a polymer film yields a mesoporous highly-deformable composite polymer for enhancing performance and creating a gapless structure of triboelectric nanogenerators (TENGs). This is a one-step scalable synthesis for developing large-scale, cost-effective, and light-weight mesoporous polymer composites. We demonstrate mesoporous aluminum oxide (Al2O3) polydimethylsiloxane (PDMS) composites with a nano-flake structure on the surface of Al2O3 MPs in pores. The porosity of mesoporous Al2O3-PDMS films reaches 71.35% as the concentration of Al MPs increases to 15%. As a result, the film capacitance is enhanced 1.8 times, and TENG output performance is 6.67-times greater at 33.3 kPa and 4 Hz. The pressure sensitivity of 6.71 V/kPa and 0.18 μA/kPa is determined under the pressure range of 5.5–33.3 kPa. Based on these structures, we apply mesoporous Al2O3-PDMS film to a gapless TENG structure and obtain a linear pressure sensitivity of 1.00 V/kPa and 0.02 μA/kPa, respectively. Finally, we demonstrate self-powered safety cushion sensors for monitoring human sitting position by using gapless TENGs, which are developed with a large-scale and highly-deformable mesoporous Al2O3-PDMS film with dimensions of 6 × 5 pixels (33 × 27 cm2).

Effect of Hollow Glass Microspheres on the Morphology, Rheology and Crystallinity of Short Bamboo Fiber-Reinforced Hybrid Polypropylene Composite

Light-weight and high-strength polymer composites have attracted the special attention of automotive and aerospace sectors since they offer advantages such as less fuel consumption and higher fuel efficiency. In the present study, an effort has been made to prepare such polymer composites using natural fiber and very low-density hollow inorganic particles. The use of hollow glass microspheres (HGM) as a potential filler particle for making light-weight hybrid polymer composites was investigated. Polypropylene (PP) and maleic anhydride-grafted-polypropylene (in 9:1 ratio) constituted the base matrix (BM). For strength reinforcement, alkali-treated short bamboo fibers (SBF) were employed, while for making the composite material light in weight, HGM were incorporated. Silane treatment of HGM by (3-aminopropyl)triethoxysilane was performed to enhance interfacial adhesion with BM. Adequate wetting of HGM and SBF was evident from the SEM images of cryo-fractured samples. A 14% increase in tensile strength was observed in comparison to virgin PP for the composite with 5 wt.% HGM, and a desirable decrease in density was observed for all the composite samples with increasing HGM content. Improvement in hardness but a marginal decrease in impact strength due to HGM fillers was observed. Rheological analysis of the composite melt samples showed an apparent increase in the complex modulus with increasing HGM content. Thermal analysis of the composites revealed a significant impact of hybrid fillers on the crystallinity, with SBF showing a minimal effect while HGM reducing it significantly. Wide-angle x-ray diffraction spectra showed changes in the crystal structure of the composite with noticeable β-form peaks.

Ricinus communis fiber as potential reinforcement for lightweight polymer composites

In this work, a natural fiber extracted from the barks of Ricinus communis plant has been demonstrated as a promising reinforcement for polymer composites. The natural fibers are principally composed of cellulose (65.5%) with a fraction of lignin (5.56%), as confirmed by chemical composition analysis and Fourier transform infrared spectroscopy. Such fibers were reinforced in polyester matrix by varying its orientations and content (by weight %) to form composite materials. The impact strengths of composite materials were tested as per the ASTM D256–06 standards and found the maximum value of 41.4 kJ m−2 for the composite having 40% of fiber content in longitudinal orientation. To establish structure-property relationship between the fiber and composites, fractography were studied using scanning electron microscopy. In fact, a rough surface of the fiber facilitates the mechanical interlocking with the polyester matrix. The results suggest that the Ricinus communis fiber reinforced composites are a potential lightweight and high strength material suitable for industrial applications.

Wool-Ball-Type Core-Dual-Shell FeCo@SiO2@MWCNTs Microcubes for Screening Electromagnetic Interference

Engineered nanostructure-reinforced lightweight polymer composites with superior electromagnetic (EM) shielding effectiveness (SET) are widely employed in high-end applications such as aerospace and microelectronic devices. Recently, carbon nanotube-based three-dimensional nanostructures have shown enormous potential due to unmatched processability, mechanical, and electronic properties. In this study, we present for the first time, highly permeable FeCo-based core-double shell wool-ball-type microcubes chemically enclosed by dielectric silica and conducting multiwalled carbon nanotubes (MWCNTs) sequentially; the resulting reinforced nanocomposites with low filler loading produced superior SET of −35 dB at 18 GHz for a specimen of 3 mm thickness. The excellent dispersion of microstructures in the soft matrix owing to the encapsulation of hard FeCo magnets by MWCNTs ensures low density and excellent flexibility for high-precision applications. The nanoengineered core-dual shell strategy for fabricating mag...

Density-tunable lightweight polymer composites with dual-functional ability of efficient EMI shielding and heat dissipation.

Lightweight dual-functional materials with high EMI shielding performance and thermal conductivity are of great importance in modern cutting-edge applications, such as mobile electronics, automotive, aerospace, and military. Unfortunately, a clear material solution has not emerged yet. Herein, we demonstrate a simple and effective way to fabricate lightweight metal-based polymer composites with dual-functional ability of excellent EMI shielding effectiveness and thermal conductivity using expandable polymer bead-templated Cu hollow beads. The low-density Cu hollow beads (ρ ∼ 0.44 g cm-3) were fabricated through electroless plating of Cu on the expanded polymer beads with ultralow density (ρ ∼ 0.02 g cm-3). The resulting composites that formed a continuous 3D Cu network with a very small Cu content (∼9.8 vol%) exhibited excellent EMI shielding (110.7 dB at 7 GHz) and thermal conductivity (7.0 W m-1 K-1) with isotropic features. Moreover, the densities of the composites are tunable from 1.28 to 0.59 g cm-3 in accordance with the purpose of their applications. To the best of our knowledge, the resulting composites are the best lightweight dual-functional materials with exceptionally high EMI SE and thermal conductivity performance among synthetic polymer composites.

Investigation on Acoustical and Physical Characteristics of Kenaf Intermix with Natural Rubber

Natural fibres are significantly used as reinforcements in manufacturing low-cost and lightweight polymer composites; other advantages include being innoxious to human, easily obtained, and having a higher capacity of biodegradability. Therefore, researchers divert their attentions to finding sustainable and eco-friendly materials such as natural fibres to be an alternative sound absorber. This paper discusses the use of natural fibre from the Kenaf fibre (Hibiscus Cannabinus), which qualifies as an acoustical material to control undesired noise. This selected natural fibre is famous in South East Asia countries and has a wide plantation. Sound absorption properties of this natural fibre have been investigated. During the processing stage, Kenaf fibres are treated with alkaline treatment; 2% individually and boundwith various percentages of natural rubber (latex). The thickness of each sample is kept constant at 50mm only. Their acoustic performance was evaluated by using an impedance tube instrument. The result shows that Kenaf reaches the maximum absorption coefficient value towards low frequency when the fibre samples are bound with natural rubber. Fibres without the binder reach a high-frequency range of 4000 Hz and above. The physical characteristics of Kenaf fibres such as density, porosity, and flow resistivity were also tested. The results demonstrate that this selected natural fibre is a promising light and environmental-friendly sound absorption material.

Molybdenum disilicide-silicon nitride bushing nozzles tailor-made for basalt fibers production

A carefully comparative study of several ceramics compounds allowed the identification of MoSi2 blended with Si3N4 as a suitable material for the realization of bushing nozzles, specifically designed for basalt fibers production. Degradation static tests were developed and performed to demonstrate the high resistance to oxidation at operating temperature of MoSi2-Si3N4 composites with respect to alumina, zirconia stabilized with magnesia or yttria, pure MoSi2, pure Si3N4, and MoSi2 englobing SiC. Moreover, the MoSi2-Si3N4 composites resulted resistant to corrosion and chemical inert with respect to oxidizing components present in basalt melts.Bushings in MoSi2-Si3N4 were obtained by using hot isostatic pressing and were processed through mechanical drilling. The basalt fibers produced with the MoSi2-Si3N4 bushing showed a constant diameter and a regular surface morphology. The bushing was recovered intact without defects or fractures demonstrating the efficiency of the selected material. Replacing platinum-rhodium bushings with ceramic ones could greatly reduce costs of basaltic fibers production and could encourage the use of these eco-friendly, natural fibers as reinforcement in lightweight polymer composites.

Electrically conductive polycarbonate/carbon nanotube composites toughened with micron-scale voids

Electrically conductive polycarbonate (PC)/carbon nanotube (CNT) composites were prepared by melt compounding. Well-controlled voids were introduced into the PC/CNT composites by supercritical CO2 foaming technique. The dispersion of CNTs and the cellular morphology of the PC composite foams were characterized with transmission electron microscopy and scanning electron microscopy, respectively. The results reveal that the well-dispersed CNTs optimize the cellular structure of the PC foams due to their heterogeneous nucleation effect. The introduction of numerous voids endows the PC composites with comparable or even higher electrical conductivity and electromagnetic interference shielding properties. Interestingly, the presence of the voids makes the brittle PC/CNT composites tough, evidenced by the greatly improved tensile toughness and notched impact strength. The highest specific toughness for PC/1wt% CNT composite foam is 35.3(kJ/m2)/(g/cm3), 435% higher than that of neat PC, and 667% higher than its bulk counterpart. This work provides an efficient approach for the preparation of lightweight, tough and functional polymer composites. The influences of porosity, loading of CNTs, and cellular structure on the notched impact strength of the composites are investigated and the toughening mechanisms are discussed.

Assessing the life cycle costs and environmental performance of lightweight materials in automobile applications

Life cycle assessment (LCA) and manufacturing focused life cycle costing are used to evaluate the potential advantages of composites in automotive applications. The life cycle costs and environmental performance of several suitable lightweight polymer composites are quantified and compared against magnesium and steel for a representative component. The results indicate that weight reduction will not always lead to improved environmental performance. Materials offering high weight savings such as carbon fibres and magnesium have been shown to give limited or negative environmental benefits over their life cycles due to increased environmental burdens associated with their production. Lower performance materials such as sheet moulding compounds were found to perform better from a life cycle perspective despite not being recycled. Lighter weight vehicle components were found to be always more costly; however their use did lead to reduced costs for the consumer through lower fuel consumption.

Correlation of mechanical and tribological properties of organosilane modified cenosphere filled high density polyethylene

Flyash cenosphere obtained as industrial waste from thermal power plants is an effective cost and weight reducing filler for developing lightweight polymer composites. Cenospheres as fillers also help in improving the mechanical properties of base polymer matrices. However, the desired enhancement depends on homogeneous dispersion of cenospheres and excellent compatibility between cenospheres and polymer matrix. In the present work, this was achieved by modifying the surface of cenospheres using silane treatment and incorporating them in a versatile thermoplastic high density polyethylene. The silane treatment resulted in considerable improvement in the impact strength and density of the composites which ultimately translated into better wear performance of composites even in severe abrasive conditions. Lancaster–Ratner correlation between mechanical properties and wear resistance was found to be almost linear for the silane treated cenospheres filled composites unlike the untreated cenospheres filled composites. Scanning electron microscopy was used to understand the wear modes and mechanisms and supported using X-ray diffractograms.

B4C‐Nanowires/Carbon‐Microfiber Hybrid Structures and Composites from Cotton T‐shirts

Nanocomposites, where nanoscale inclusions are embedded in a matrix material, have attracted increasing research attention in recent years. Here, we limit our focus to polymer nanocomposites. Nano-reinforcements (for instance, nanoparticles, nanowires, and nanotubes) have largely disappointed us in manufacturing lightweight, high-strength, and high-toughness polymer composites because of their agglomeration in the matrix—one of the major drawbacks limiting their reinforcing effect. Dispersion of nano-reinforcements is not trivial and often requires expensive facilities and/or processing procedures. It has proven difficult to disperse nano-reinforcements in the matrix via conventional chemical, mechanical, and physical methods. To date, a perfect dispersion of nanoreinforcements in a matrix material has not been achieved. Despite considerable efforts, the mechanical properties of polymer nanocomposites are still far below their theoretically predicted potential. On the other hand, nano-reinforcements and their composites produced through the currently available methods are usually too expensive for use in large-scale industrial applications. To solve these two critical problems, we turned our attention to investigate new concepts for nano-reinforcement dispersion and new synthesis techniques that enable low-cost, high-throughput manufacturing of nanocomposites. Boron carbide (B4C), a lightweight refractory semiconductor, is the third hardest material known to man at room temperature and becomes the hardest above 1100 8C. It has many unique properties such as low density (2.5 g cm ), a small thermal extension coefficient (5.73 10 6 K ), a high melting point (>2400 8C), high resistance to chemical attacks, high thermal stability, a high Seebeck coefficient, and a large neutron absorption cross-section. The combination of these superior properties gives rise to numerous applications, especially under extreme conditions, for example, lightweight body armor, aircraft armor, abrasive wear-resistant materials, solid-state neutron detectors, and, potentially, power generation in deep-space flight applications. Recently, 1D B4C nanostructures, including nanowires and nanorods, have attracted significant attention. To synthesize B4C nanowires, the carbon source is essential. Among most of the available synthesis methods for 1D B4C nanostructures, artificial materials such as carbon black, carbon nanotubes, and activate carbon are selected as carbon source. A stepwise synthetic procedure was usually adopted: metal-catalyst nanoparticles were first synthesized and subsequently added to the precursors as the catalyst. Cotton has been used by mankind for at least 7000 years. It is the oldest and most commonly used nanoporous material, which is constructed from polysaccharide chains arranged into amorphous and crystalline regions. Today, the world production of cotton is approximately 20 million tons per annum, mainly for clothing, paper, and medical uses. In this work, a commercial cotton T-shirt was used as both the template and the carbon source to synthesize large quantities of radially aligned B4C nanowires on carbon microfibers. The as-synthesized B4C-nanowire/carbon-microfiber hybrid structures were then simply dipped in an epoxy resin bath to achieve a high dispersion of B4C nanowires in the matrix and highthroughput manufacturing of laminated polymer nanocomposites. A digital camera image of the 100% cotton T-shirt is shown in Figure 1a. A striking and extremely useful feature of cotton is its ability of absorbing large quantities of liquids, particularly water. Figure 1b is a representative digital camera image of a piece of the cotton T-shirt after the absorption of a solution with Ni(NO3)2 6H2O and amorphous boron powders. Figure 1c shows 6 pieces of final textiles. A typical scanning electron microscopy (SEM) image of carbon microfibers covered with B4C nanowires is shown in Figure 1d. The B4C nanowires, with a diameter ranging from 80 to 200 nm and a length greater than 4mm, grew radially on the entire length of the carbon microfiber (Fig. 1e). The SEM image (Fig. 1f) and transmission electron microscopy (TEM) image (Fig. 1g) together reveal a catalyst particle on the tip of each nanowire. Most of the catalyst particles were spherical and had a diameter distribution of 90 to 250 nm. TEM image (Fig. 1g) also shows that the diameter of the catalyst is larger than that of the corresponding B4C nanowire. Energy dispersive spectroscopy (EDS) reveals that the catalyst particle on the nanowire tip is nickel boride. This suggests that a catalyst is essential for growing such B4C nanowires. Our experimental results proved that most of the catalyst particles can be easily removed by acid treatment (HNO3þHF or HNO3). The B4C

Thermoelectric Behavior of Segregated-Network Polymer Nanocomposites

Segregated-network carbon nanotube (CNT)-polymer composites were prepared, and their thermoelectric properties were measured as a function of CNT concentration at room temperature. This study shows that electrical conductivity can be dramatically increased by creating a network of CNTs in the composite, while the thermal conductivity and thermopower remain relatively insensitive to the filler concentration. This behavior results from thermally disconnected, but electrically connected, junctions in the nanotube network, which makes it feasible to tune the properties in favor of a higher thermoelectric figure of merit. With a CNT concentration of 20 wt %, these composites exhibit an electrical conductivity of 4800 S/m, thermal conductivity of 0.34 W/m x K and a thermoelectric figure of merit (ZT) greater than 0.006 at room temperature. This study suggests that polymeric thermoelectrics are possible and provides the basis for further development of lightweight, low-cost, and nontoxic polymer composites for thermoelectric applications in the future.

Processing and properties of new high‐temperature, lightweight composites based on foam polyimide binder

AbstractWe report a method for making novel, lightweight (ρ = 0.3–1.1 kg/dm3) polymer composites based on high‐temperature foam polyimide binder, carbon fibers, and organic fibers. The density and mechanical properties of the foam composite can be varied over a relatively wide range, depending on the volume contents of the fiber and air pores. The resin's high glass transition temperature of 260°C, coupled with the high thermal stability of carbon or polyimide fibers, contributes to its excellent retention of mechanical properties at elevated temperatures. The temperature at the beginning of weight loss is not lower than 570°C and depends on the kind of fiber felt. The combination of excellent thermal and specific mechanical properties of foam composites together with exceptional thermal stability and processability on conventional molding equipment can provide unusual performance for the new design of advanced materials and structures.

Versatile Lightweight Polymer Composites

Abstract Knowledge of polymer composites goes back to antiquity, yet their most spectacular boom, from a scientific point of view, began during the 1960s when their microstructure was studied as it relates to their properties. Modern technology demands newer materials in place of conventional engineering materials. Although concrete is an excellent building material, its use is subject to certain limitations. These include its relatively low tensile strength, a tendency to crack with changes in temperature coupled with moisture absorption, and deterioration due to chemical and physical attack under various environmental conditions. Polymer composites, on the other hand, have outstanding strength and durability which offer several advantages over those of conventional materials.

Lightweight Polymer Composites from Waste Materials: A Solution to Environmental Pollution

Abstract Several new lightweight polymer concretes derived from industrial, agricultural, and naturally occurring waste materials were investigated. Various physicomechanical properties of these materials were studied. Such inexpensive and lightweight polymer composites, which have properties superior to ordinary reinforced cement concrete, may find wide applications in building technology and related areas and may serve as better substitutes for cement. Furthermore, recycling of such wastes from various sources may help to solve the present environmental pollution problems.