Filled Polymer Composites Research Articles

Preparation of graphene oxide and alkali lignin nanohybrids and its application to reinforcing polymer

Lignin has been widely used as an eco-friendly and sustainable filler in polymer composites, which is a promising reuse of lignin waste. However, it suffers from a dissatisfactory reinforcing effect for polymers due to the many surface functional groups of lignin. In this work, a small quantity of graphene oxide (GO) nanosheets was employed to help form a network of alkali lignin (AL) nanoparticles to improve their hardness. The morphologies and structures of GO–AL hybrids were characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis (TGA) and Raman spectra. Taking poly(vinyl alcohol) (PVA) as a model polymer, the reinforcing effect of GO–AL hybrids was examined. Dynamic mechanical analysis results showed that the storage modulus of PVA was improved more by GO–AL hybrids than AL, especially in the high-temperature region (50–120 °C). By contrast, the tensile strength and the Young’s modulus of PVA containing 4 wt% GO–AL (1:4) were increased by 84.4% and 335.3%, respectively. TGA analysis indicated that the thermal stability of the PVA nanocomposites was improved after incorporation of nanofillers. The main observation presented here could serve as the basis for the design and preparation of lignin and other biomass-based polymer nanocomposites.

Enhanced thermal conductivity by combined fillers in polymer composites

This paper reports a new way of improving the thermal conduction property of polymer composites composed of silicone rubber and combined fillers obtained by attaching spherical alumina particles to carbon fibers using spray-drying method. The experimental results showed that the thermal conductivities of the polymer composites were 16, 28, 30, 32, and 42% higher than those of composites with untreated carbon fibers at the same content. The analysis based on effective medium theory revealed that the interface thermal resistance decreases from 1.2 × 10−6 m2 K/W to 8.5 × 10−7 m2 K/W in polymer composites. It demonstrates that the combined fillers could decrease the interface thermal resistance to improve the thermal conduction property of polymer composites, and thus are promising for the development of high-performance thermally conductive products.

Structure, mechanical and thermal properties of polypropylene based hybrid composites with banana fiber and fly ash

Polypropylene (PP)-Flyash (FA) composites containing natural banana fiber (NF) treated by Maleic anhydride and NaOH are reported here. Mechanical properties such asflexural modulus and impact strength were improved considerably which were maximum for 20% fly ash filled PP-NF treated composites. There is extensive nucleation of theα crystalline phase of PP in presence of the additives. This changed to mixed α phase with slight β content in presence of FA and treated NF as confirmed by XRD and DSC. The results on the mechanical properties have been explained on the basis of structure development of PP in presence of fly ash and treated NF. The results have also been analyzed with the help of different models for filled polymer composites and using rule of mixtures of two composites to form final ternary hybrid composite. Some agreement is found if a factor is introduced for redistribution of fibers due to added FA as third component. However, the synergistic behavior at certain composition can be explained on the basis of crystalline structure and nucleation due to the additives.

Thermal and electrical characterization of composite metal oxides particles from periwinkle shell for dielectric application

Rather than synthesizing metal oxides through chemical processes as fillers in polymer composites, metal oxides from natural sources (waste) could provide a cheaper and environmentally friendly alternative. In this work, a fine powder prepared from properly cleaned periwinkle shells was examined for its use as filler for polymer composites for high-voltage application. The powder was characterized using scanning electron microscopy (SEM), X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, thermal conductivity set-up and a programmable LCR Bridge. The SEM image of the powder revealed a range of particle sizes that vary from 2 to 34 μm. The chemical analysis shows that CaO is the dominant metal oxide in the powder with 81.8 wt%. The dielectric constant and the electrical conductivity of the powder are 11.08 and 1.5876 × 10−8 S m−1, respectively, at the frequency of 200 Hz. The electrical conductivity of the powder is lower than the conductivity of pure CaO, while the thermal conductivity is slightly higher than that of pure CaO. This could be due to the influence of the other constituent metal oxides. The is an indication that periwinkle shell powder if properly processed to micro- and even nano-sized particles can be a good candidate as a filler in polymer composites to produce polymeric insulation with good insulating and thermal conducting properties.

Thermal and mechanical behavior of thermoplastic composites reinforced with fibers enzymatically extracted from Ampelodesmos mauritanicus

This work investigates the morphology, the thermal, and mechanical properties of technical fibers extracted from the Ampelodesmos mauritanicus (Diss) grass using a process that combines mechanical, mild chemical, and enzymatic steps. The structure and the thermal stability of Diss fibers make them suitable as a reinforcing filler in polymer composites, which was assessed by manufacturing biocomposites with improved stiffness and a tensile strength not degraded by Diss fibers when compared to those of a commodity polymer and a biodegradable one, namely polypropylene and poly(lactic acid). This work confirms that enzyme mixtures obtained from commercially available products of relatively low cost can represent a simple and environmentally friendly means to extract less common natural fibers. POLYM. ENG. SCI., 59:2418–2428, 2019. © 2019 Society of Plastics Engineers

Polymer-derived SiCN ceramics as fillers for polymer composites with high dielectric constants

High-dielectric-constant (high-e) ceramic/polymer composites are an important class of advanced functional materials due to their applications in energy storage fields, such as embedded capacitors. Here, we synthesized novel polymer-derived silicon carbonitride (SiCN)-filled polyvinylidene fluoride (PVDF) composites by the tape-casting method. For comparison, commercial BaTiO3-filled PVDF composites were synthesized following the same process. The SiCN/PVDF composites showed much higher e than the BaTiO3/PVDF composites over a broad frequency range (10−1–106 Hz). Furthermore, the SiCN/PVDF composites showed ultrahigh e at low frequencies. The e of the 40 vol% SiCN/PVDF composite was as high as 2600 at 10−1 Hz. Although the dielectric breakdown strengths of the SiCN/PVDF composites were slightly lower than those of the BT/PVDF composites, the calculated maximum energy storage density of the 40 vol% SiCN/PVDF composites (17.5 J cm−3) was much higher than that of 40 vol% BT/PVDF (0.773 J cm−3) at 10−1 Hz. This is the first report on the use of polymer-derived ceramics as a component of ceramic/polymer composites. The results indicate that the polymer-derived SiCN ceramics can serve as promising ceramic fillers for high-e composites and that the obtained SiCN-filled composites have promising applications in energy storage fields.

Tailoring graphene reinforced thermoset and biothermoset composites

Abstract The surge of knowledge among researchers pertaining to the excellent properties of graphene has led to the utilisation of graphene as a reinforced filler in polymer composites. Different methods of graphene preparation, either bottom-up or top-down methods, are important requirements of starting materials in producing reinforced properties in the composites. The starting graphene material produced is either further functionalised or directly used as a filler in thermoset polymer matrixes. An effective interaction between graphene and polymer matrixes is important and can be achieved by incorporating graphene into a thermoset polymer matrix through melt mixing, solution mixing or in situ polymerisation processes. In addition, by taking into consideration the importance of green and sustainable composites, the details of previous work on graphene reinforced bio-thermoset polymer matrixes is discussed. The resultant mechanical and thermal properties of the composites were associated to the chemical interaction between the graphene filler and a thermoset matrix. Exploration for further variations of graphene polymer composites are discussed by taking the reinforcement properties in graphene composite as a starting point.

Study the influence of size and shape of silica fillers in polymer composites on the tribolayer formation

Study the influence of size and shape of silica fillers in polymer composites on the tribolayer formation

Filler shape and volume fraction effect on dynamic compression behaviour of glass filler reinforced epoxy composites

The effect of filler shape and volume fraction on the dynamic compression behaviour of low volume fraction rigid particle filled polymer composites is demonstrated by performing experiments using s...

A Unified Approach to Determining the Effective Physicomechanical Characteristics of Filled Polymer Composites Based on Variational Principles

An approach to solving the known problem on determination of the effective physical and mechanical properties of dispersedly filled compositions is presented. The solution is based on the formulation and numerical implementation of boundary-value problems based on the fundamental equations of the theories of elasticity, thermal conductivity, electrostatics, and electrical conductivity. The general concept is to obtain detailed parameters of state of the composition under external actions with account of the real structure of the material. Averaging procedures are used to determine the effective properties of the compositions. The formulation and solution of boundary-value problems, in all cases, is reduced to the formulation of corresponding variational principles and their implementation by the methods of computational mechanics, in particular, by the finite element method. The effective characteristics of the composite under mechanical, thermal, and electromagnetic actions are calculated on the basis of energy considerations: the stored energy of a structurally inhomogeneous body is equal to the energy of a homogeneous comparison body under various actions. A comparison of calculated and experimental values of the effective characteristics attests to the applicability of the models proposed and the methods of their implementation.

Melt Flow Index and Flammability of Alumina, Zinc Oxide and Organoclay Nanoparticles Filled Cross-Linked Polyethyelene Nanocomposites

Abstract Nanofiller filled polymer composites have been the subject of intense research, development and commercialization. In this study, we report three types of nanofiller filled cross-linked polyethylene (XLPE) at different filler loadings (0.5, 1.0, 1.5 and 2 wt.%). Nanofillers composed of alumina, zinc oxide and organoclay were embedded in cross-linked polyethylene (XLPE). Several formulations containing nanofillers and XLPE were prepared using an internal mixer and were molded using a compression mold to form test samples. Flammability properties and melt flow index (MFI) of different types of XLPE nanocomposites were determined. The addition of 0.5 wt. % organoclay drastically decreased the MFI values. However, no significant change in MFI values is observed for alumina and zinc oxide. Further addition of organoclay nanofillers up to 2 wt. % decreases the MFI values of the XLPE nanocomposites. The flammability of alumina, zinc oxide and organoclay filled XLPE nanocomposites were investigated by horizontal burning test. The results show that zinc oxide filled XLPE nanocomposites has lower burning rate compared to alumina and organoclay.

Dynamic compression behavior of glass filled epoxy composites: Influence of filler shape and exposure to high temperature

The effect of filler shape, volume fraction and high temperature cycle on the dynamic compression behavior of rigid particle filled polymer composite is demonstrated by performing experiments using split-Hopkinson pressure bar (SHPB) setup. Two glass filler variants, spherical particles and milled fibers, are reinforced into epoxy matrix upto 10% volume fraction. Two sets of test specimens are prepared; room temperature cured (RTC) and high temperature exposed (HTE) - the ones prepared by subjecting RTC composites to a temperature cycle beyond their glass transition temperature (Tg). The yield stress of milled fiber composites which are consistently higher in HTE cases increases with increasing filler volume fraction whereas it remains nearly constant in all spherical particle composites. While RTC materials exhibit strain softening characteristics, the post-yield strain hardening behavior of HTE composites is attributed to the increased cross-link density of epoxy matrix. Debonded fillers and their foot-prints on the crushed surfaces of HTE composites indicate the relaxation of residual stresses, developed at the filler/matrix interface during curing process. Computational analyses suggest that the average matrix stress in composites remains unaffected by the shape of the inclusions whereas comparatively higher inclusion stresses indicate that slender fillers provide better resistance to deformation when compared to the circular ones. Near constant stresses in circular inclusions at low volume fractions is attributed to the large inter-particle separation. Computational results complement experimental observations where the milled fiber composites consistently exhibited higher yield stress when compared the spherical particle counterparts.

Effect of ionomer interfacial compatibilization on highly filled HDPE/Al2O3/ionomer composites: Morphology and rheological behavior

Highly filled high-density polyethylene/alumina (HDPE/Al2O3) composites were fabricated by melt mixing with direct incorporation of poly(ethylene-co-methacrylic)-based ionomer (EMAA-Na) as an interfacial compatibilizer. SEM and EDX micrographs indicate EMAA-Na interfacial adhesion on the Al2O3 spheres. Under low EMAA-Na content conditions, the FT-IR characterization and an EMAA-Na neutralization degree analysis revealed the priority of the melt neutralization interaction between the acid groups of the ionomer and the Al2O3 spheres in the composite. Under high EMAA-Na content conditions, an AFM phase characterization revealed the formation of an EMAA-Na ionomer spherical domain (∼300 nm) dispersed in an HDPE matrix due to the microphase separation of ionic chains. Capillary and dynamic rheology measurements were also conducted to investigate the phase morphology evolution. The polymeric adhesion on the Al2O3 sphere surfaces contributed to the increase of the melt viscosity and gradual elongation thickening behavior of the composite melts. The formed spherical domain structure of EMAA-Na of the composite melts contributed to the shear thickening, elongation thickening and yield behavior. Three rheology criteria plots indicate large complex formation in the composite melts. The EMAA-Na incorporation in the highly filled HDPE/Al2O3 composite matrix not only improved the strength and toughness performance, with a 27% improvement in the elongation at break (EMAA-Na content 1 wt.%) and 21% improvement in the tensile strength (EMAA-Na content 10 wt.%), but also preserved the good thermal conductivity (∼1.5 W/(m·K)). This study reveals the potential application of the EMAA-Na ionomer to resolve the challenge of the strength and toughness performance degradation in highly filled polymer composites.

Армирующие наполнители для полимерных композитов из нетканных органических материалов

Армирующие наполнители для полимерных композитов из нетканных органических материалов

A Thermal Protective Compound Elastic at Negative Temperatures

A compound based on polyether urethane rubber with end epoxy urethane groups and epoxy oligomers for the protection of products made of highly filled polymer compositions subject to the effect of positive and negative temperatures was developed. Its curing regularities and mechanical properties were studied. It was shown that the compound retains elasticity at the temperatures of up to –40°C and surpasses the currently used compound in terms of mechanical characteristics.

PRODUCTION AND CHARACTERIZATION OF GREEN POLYMER COMPOSITE WITH NATURAL FILLERS

Nowadays, development of environment friendly (green), high efficiency and low cost engineering materials is the main focus of researchers, where composite is at the central point. In this regard, natural fiber reinforced polymer composites have gained much attention because of their light weight, ease of fabrication, biodegradability, etc. A large amount of sand/clay mineral is also widely used as fillers for polymer composites. This paper deals with the effects of jute fiber and river based sand particle on the tensile strength and biodegradability of polyester matrix composites. At first, composites were developed and half of samples were kept under wet soil for six months to evaluate their biodegradability. Tensile tests of all samples were done by tensile testing machine. Experimental results revealed that addition of jute fiber enhances the biodegradability, but reduces the strength of the polymer, whereas, fine sand particles help regain the strength of the composite without adding any remarkable change in biodegradability. Article DOI: https://dx.doi.org/10.20319/mijst.2018.42.137148 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Forestry wastes filled polymer composites for agricultural use

Two kinds of polymer composites were prepared using poly (vinyl alcohol) as binder and forestry or wood processing wastes as fillers. In one kind of the composites pine needle meal was used as filler while the other kind of the composites was filled with pine bark meal. Glycerol and oleic acid were used for the modification of mechanical, sorption properties and solubility of the composites. The films of the composites were fabricated and their mechanical, viscoelastic and antifungal properties as well as water absorption and solubility in water were studied. Mathematical experiment design was used to evaluate influence and importance of both glycerol and oleic acid content on of mechanical properties, solubility and water absorption of the composite films filled with pine bark meal. The second order polynomial models were developed in order to find out optimal content of both glycerol and oleic acid in compositions. Exploitation properties of the composite pots prepared from the composites were studied and vegetation tests were performed. It was shown that evaporation rate of water through the walls of the composite pots was by 45% lower and the temperature of substrate in the composite pots was by 3–4 °C higher as compared with the corresponding characteristics of peat pots. Plants cultivated in the composite pots had better developed root system relative to those cultivated in peat pots.

Fabrication of epoxy functionalized MWCNTs reinforced PVDF nanocomposites with high dielectric permittivity, low dielectric loss and high electrical conductivity

Nanocomposites of Polyvinylidene Flouride (PVDF) with Multi-walled Carbon Nanotubes (MWCNTs) possess excellent thermal, piezoelectric and conductive behaviors. However, the potential of MWCNTs as filler in polymer composites is hampered by their poor dispersion into the matrix, corresponding to the strong inter-tubular and weak inter tubular-polymer chain interactions. This issue is successfully overcome by utilizing di-glycidyl ether of bisphenol-A (DGEBA) grafted MWCNTs (DG-MWCNTs) as reinforcement in PVDF matrix. To synthesize the desired nanocomposites, the easier to manipulate, solution casting technique was employed. The resulting PVDF/DG-MWCNTs nanocomposites have different loadings of filler ranging from 1.0 wt% to 10 wt%, and have shown variation in the phase transformation from α-phase to β-phase along with improvements in thermal and dielectrical behaviors. It was revealed by the impedance spectroscopy (IS) that the reinforcement of PVDF with DG-MWCNTs leads to an increase in the dielectric permittivity. This increase was found higher enough to reach up to ∼5288 (at ∼100 Hz) and 214 (at ∼102 Hz) for filler loading of 10 wt %. The increase is several hundreds of magnitude i.e., ∼204 at ∼102 Hz higher than the PVDF matrix, while retaining a low level conductivity (4.18 × 10−6 S/cm). This enhancement in the dielectric permittivity is attributed to the strong interfacial interaction between PVDF and DG-MWCNTs, and was explained by the Maxwell-Wagner-Sillar (MWS) effect.

Theoretical and empirical thermal conductivity models of red mud filled polymer composites

The present paper deals with the prediction capability of theoretical and empirical models on thermal conductivity coefficient (TCC) of red mud/polypropylene composites. Red mud is known as an industrial waste material occurs during the production of alumina by Bayer’s process. The characterization analyses of the red mud particulates have been carried out by XRF, XRD, and SEM. Experimental TCC measurements for the red mud/polypropylene composites are given and the results are compared with the predicted values based on Russell, Maxwell-Eucken, Bruggeman, Cheng-Vachon, Hamilton-Crosser, Agari, Nielsen, Mixed empirical and Percolation micro-models. It is shown that red mud waste material having hybrid structures can be used to obtain relatively high TCC up to 50% volume fraction, successfully. The results obtained on TCC of red mud/PP particulate composites as a cheaper and waste material (red mud) encourage the researchers for its potential applications.

Seaweeds as Renewable Sources for Biopolymers and its Composites: A Review

Background: The rising environmental awareness has driven efforts for the development of renewable materials for various end-use applications. The trend of using biopolymer in combination with organic or non-organic filler has increased rapidly in recent years. Seaweed is a versatile organism that produces various kinds of polysaccharides i.e. agar, carrageenan and alginate that are extensively used in the development of biopolymer. Biopolymers derived from seaweed polysaccharides possess promising features as they are renewable, biodegradable, biocompatible, and environment-friendly. The aims of this paper are to review research related to the seaweed and its biopolymers for various applications. Methods: Research articles related to the seaweed and its biopolymers are reviewed. The summary of seaweed composites and seaweed biopolymers modification are provided. Results: Seaweed has been used for various applications ranging from food, thickening agent, natural medicine, biofuel, biosorbent material, etc. Seaweed was also used as reinforcement to improve the mechanical properties of polymer composites. Various modifications have been done on seaweed biopolymer to improve the properties of the materials such as blending with other polymers, the addition of compatibilizer, and reinforcement with other materials. The potential of seaweed polymers i.e. agar, carrageenan, and alginate in various applications such as packaging and pharmaceutical show promising characteristics for applications. Conclusion: Seaweed is a highly potential source for renewable biopolymers. These biopolymers have shown great characteristics for various applications due to their unique film-forming ability and excellent mechanical properties. These properties can be further improved following various modification techniques i.e. reinforcement and blending. The potential of seaweed as filler in polymer composites provides evidence to improve the thermal, physical, and mechanical properties of the synthetic polymer matrix. It can be concluded that seaweed is a highly potential renewable resource for the development of biocompatible and environmentally friendly materials.