Carbon black/polystyrene composites as candidates for gas sensing materials

Amorphous polymer-based composites consisting of polystyrene and carbon black were developed in the current work as candidates for gas sensing materials. With the help of polymerization filling, i.e., in-situ polymerization of styrene in the presence of carbon black, the composites were provided with low percolation threshold. The experimental results indicated that the composites have selective sensitivity as characterized by high electrical responsivity to the vapors of non-polar and low polar solvents, and low responsivity to high polar solvent vapors as well. Besides conductivity of the composites, absorption characteristics of both the matrix and the fillers exert importance influence on the gas sensitivity of the composites. Therefore, composites’ performance can be tailored by changing filler concentration, molecular weight and molecular weight distribution of matrix polymer, etc. In regard to the fact that most conducting polymer composites as vapor sensing materials are based on crystalline polymer matrices, the approach reported by this paper provides another feasible way to develop new candidates.     

The effect of multiscale hybridization on the mechanical properties of natural fiber-reinforced composites

The main objective of this work was to investigate the effect of reinforcements at different scales on the mechanical properties of natural fiber-reinforced composites. Pure jute and interlaminar hybrid jute/glass fiber-reinforced polymer composites were fabricated. Different types of fillers in two weight fractions (1 and 3 wt. %) were used as second reinforcements in the hybrid jute/glass composites. Tensile, flexural, and impact tests were performed. It was found that the macroscale inter-play hybridization significantly improved the mechanical properties of the pure jute fiber based composites. When the fillers are used as second hybridization, the modified composites presented higher mechanical properties when compared to pure jute composites. However, the effect of fillers on the mechanical properties of the hybrid composites presented various trends due to the interaction between several factors (i.e., particle scale, content, and nature), which cannot always be separated. Increasing the synthetic filler content improved the tensile properties of the filled hybrid composites, while increasing the natural filler content worsen the tensile properties. The flexural strength of the multiscale hybrid composites was improved, while the impact properties were negatively affected.     

Photopolymerization of Pollen Based Biosourced Composites and Applications in 3D and 4D Printing

Pollen have the potential to be effective plant-based biorenewable reinforcing fillers for polymers due to their chemical stability and unique micro- or nano-structured surfaces. Pollen-polymer composites can form the basis for a new class of light-weight and sustainable materials if compatible polymer-filler systems can be engineered through photopolymerization, but this idea is previously unexplored. The first demonstration of photopolymerization and 3D printing with the incorporation of pine pollen as filler in poly(ethylene glycol) diacrylate are presented. The filler properties affecting the related depth of cure and the mechanical, thermal, and functional properties are examined in detail. In addition, the lithography technique is applied to the photocomposites for the production of 3D patterns. 4D printing behavior is also possible through the water swelling and dehydration induced actuation of the 3D printed composites with spatial resolution features. This work is expected to provide a new way to a field for photopolymerization reactions in natural material-resin composites and thereby to expand potential applications in 3D and 4D printing.     

Mechanism of filler action in reducing the wear of PTFE polymer by differential scanning calorimetry

Two types of representative nanometer materials, i.e., fibroid nanometer attapulgite and approximate spherical ultrafine diamond, were selected as fillers of polytetrafluoroethylene (PTFE) to study the mechanism of the wear‐reducing actions of the fillers in PTFE composites. The friction and wear tests were performed on a block‐on‐ring wear tester under dry sliding conditions. Differential scanning calorimetry (DSC) was used to investigate material microstructure and to examine modes of failure. No significant change in coefficient of friction was found, but the wear rate of PTFE composites was orders of magnitude less than that of pure PTFE. DSC analysis revealed that nanometer attapulgite and ultrafine diamond played a heterogeneous nucleation role in PTFE matrix and consequently resulted in increasing the crystallinity of PTFE composites. Moreover, the PTFE composite with higher heat absorption capacity and crystallinity exhibited improved wear resistance. A propositional “sea‐frusta” frictional model explained the wear mechanism of filler action in reducing the wear of PTFE polymer, i.e., fillers in the PTFE matrix effectively reduced the size of frictional broken units for PTFE composites and restrained the flowability of the units, as well as supporting the applied load. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical properties of particulate‐filler/woven‐glass‐fabric‐filled vinyl ester composites

Studies of the effect of particulate fillers on specific mechanical properties of vinyl ester epoxy (VE) reinforced with woven glass fiber composites were carried out with different filler types and particulate filler contents (1%, 3%, and 5% by weight). Two types of particulate filler were used, i.e., calcium carbonate (CC) and phenolic hollow microspheres (PHMS). The composites were prepared by using a hand lay‐up and vacuum bagging method. Woven glass fabric composites filled with particulate PHMS were observed to have better specific flexural strength and specific impact strength, as well as lower density, than those filled with particulate CC. Morphological features determined by scanning electron microscope (SEM) proved that the PHMS filler experienced good bonding in the VE matrix, a feature which contributed to the improvement in the properties of the composites. The incorporation of particulate fillers into the composites also influenced the storage modulus with a minimal effect on T_g. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

A review of conductive polymer composites filled with low melting point metal alloys

Metal alloys with low melting temperatures may be blended into polymers to improve their electrical conductivity. We review the preparation, morphology, and electrical conductivity of polymer composites based on low melting point metal alloys, with or without additional filler particles. Since such alloys can be liquid under melt processing conditions, the composite morphology is determined by phenomena such as coalescence of liquid metal drops, orientation of the liquid metal phase, or selective wetting of a second filler by the liquid metal. None of these phenomena appear in conductive composites based on more common conductive fillers such as carbon black, carbon nanotubes, or metal particles. The published literature suggests that composites based on low melting metal alloys, with or without additional non‐melting filler particles, can have much higher percolation thresholds and much higher electrical conductivity (～1,000 S/m) than those based on fillers such as carbon black or carbon nanotubes. Changes in other properties such as rheological or mechanical properties are also discussed. POLYM. ENG. SCI., 58:1010–1019, 2018. © 2017 Society of Plastics Engineers     

Nano-BN/Nano-TiO2 and micro Mg(OH)2 loaded hybrid ethylene propylene diene monomer elastomer composites for outdoor high-voltage insulation application

This work deals with the synthesis, characterization of hybrid ethylene propylene diene monomer (EPDM) composites loaded with nano-boron nitride (nano-BN)/nano-titanium dioxide (nano-TiO₂) and micro Mg(OH)₂ particles for its suitability towards high-voltage insulation application. The elastomer samples were prepared by carefully dispersing the micro and nano fillers during the mastication process of EPDM polymer using a two roll mill, followed by vulcanization. The samples were characterized for mechanical, morphological, thermal, and electrical insulation properties. The highest tensile strength among the composite samples was noted for 1 phr nanoparticles loaded samples. Fourier Transform Infrared (FTIR) results show no change in the chemical moiety upon addition of nano-BN/nano-TiO₂ in EPDM composites. Enhancement in hydrophobicity is observed for 3 phr nano-TiO₂ loaded composites, which shows a maximum static contact angle of 110°. Meanwhile remarkable enhancement in the thermal conductivity and volume resistance of the composites are contributed to the addition of nano-BN, thereby achieving maximum dielectric breakdown voltage (i.e., ~21 kV/mm for EMB3). Scanning electron microscope images and atomic force microscopy (AFM) topography highlight that low concentration (i.e., 1 phr) based composites have homogeneous dispersion in matrix and excessive nano filler addition deteriorates properties by forming filler aggregates and increasing surface roughness.     

Impact of thiourethane filler surface functionalization on composite properties

Thiourethane oligomers added to methacrylate matrices improve fracture toughness and reduce polymerization stress. In this study, the oligomers are added to the surface of inorganic fillers in the formulation of resin composites. Systematically varied fillers treated either with the thiourethane or a methacrylate silane control are tested. Thiourethane reduces the rate of polymerization of light-cured composites but does not affect the final degree of conversion. Filler functionalization with thiourethane increases the depth of polymerization, in filler type-dependent fashion. Thiourethane reduces the polymerization stress for all fillers. The findings suggest that this approach results in the same general effects with the addition of thiourethanes directly to the matrix. This is accomplished with a lower overall concentration of thiourethane, and with no prejudice to the handling characteristics of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47687.     

Development of a Zeolite/Polymer-Based Hydrogel Composite through Photopolymerization for 3D Printing Application

In recent years, hydrogels have been widely applied in daily life and industry. More and more fillers have been combined with hydrogel to broaden their fields of application and improve their mechanical properties. However, there are few works about zeolite-based hydrogel composites via photopolymerization. Hence, in this work, it is reported that the fabrication of hydrogel composites containing zeolite (FAU-13X ≈ 40 wt%) under mild photopolymerization conditions (visible LED light irradiation, at room temperature, under air, and without any monomer purification). Markedly, compared to pure hydrogel, the elastic modulus (G′) of hydrogel composite contains 10% FAU-13X increased by more than 100%. When the zeolite content reached 40%, the water swelling ratio in mass reached 120%, and that in volume remained at 150%. In addition, 3D patterns with flat surface are obtained through direct laser write as a lithography technique. This means these hydrogel composites can be applied in the field of water absorption materials and 3D printing.     

Effect of chemical treatments on the mechanical,flow, and morphological properties of talc‐ and kaolin‐filled polypropylene hybrid composites

This study was performed with commercially available phenyl trimethoxysilane (PTMS) and neoalkoxytitanate [i.e., neopentyl(diallyl)oxytri(dioctyl)phosphato titanate (LICA 12)] as coupling agents. PTMS and LICA 12 were used to treat talc and kaolin to compare their effects with untreated fillers upon incorporation into polypropylene (PP). Single‐filler PP composites (containing either talc or kaolin) and hybrid‐filler composites (containing a mix of both talc and kaolin) were compounded in a twin‐screw extruder and subsequently injection‐molded into dumbbells. The incorporation of PTMS and LICA 12 slightly decreased the tensile and flexural properties in terms of modulus and strength but increased the elongation at break for both single‐filler and hybrid‐filler composites. There was also a significant improvement in the impact strength of the composites, particularly those treated with LICA 12. The hybrid composites, through the synergistic coalescence of positive characteristics from talc and kaolin with the aid from chemical treatment provided an economically advantageous material with mechanical properties comparable to those of the single‐filler‐filled PP composites. Further investigations on flow and morphological properties were also done to correlate the mechanical properties of the single‐ and hybrid‐filler‐filled PP composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Degree of conversion and mechanical properties studies of UDMA based materials for producing dental posts

Nanocomposites are a relatively new material in producing fiber re‐enforced dental posts. The mechanical properties of nanocomposites, which strongly associate with the resin matrix, nanoparticles, and the interface between inorganic fillers and organic matrix, play an important role in determining the quality of dental posts. This work was to investigate the effect of degree of conversion (DC) and silanization of fillers on the mechanical properties of nanocomposties. Experimental Urethane dimethacrylate (UDMA) based dental composites containing unsilanized and silanized SiO₂ filler and various amount of triethylene glycol dimethacrylate (TEGDMA) were prepared at the first step. The DC of composites at different ratios of UDMA/TEGDMA, cure temperature and cure time was measured by Fourier transform infrared spectroscopy. The results showed that DC increases with the increase of TEGDMA content in resin matrix. Both increase of the cure temperature and cure time can cause the increase of DC. The incorporation of fillers, either silanized, or unsilanized filler, caused the decrease of DC. However, composites reinforced with silanized silica showed relatively lower DC, and DC decreased with the increase of silanized filler content. The effect of incorporation of fillers on the mechanical properties was investigated. Silanized silica can effectively improved the flexural strength and flexural modulus of material, and these properties increased with the increase of silica content. Thermomechanical analysis (DMA) provided the similar results to the static property measurements. SEM images of fracture surfaces of specimens from flexural testing revealed the surface morphology is strongly related to the quality of interface between inorganic fillers and organic matrix. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Polymer/Graphite Nanocomposites: Physical Features,Fabrication and Current Relevance

Advancement from graphite to functional polymer/graphite nanocomposite is presented in this review article. These materials are comprised of graphite as filler, i.e., carbon-based thermodynamically stable, pseudo–-two-dimensional (2D), planar and layered solid material. Graphite and its modified forms propose unique properties to composites as high surface area, thermal and electrical conductivity as well as mechanical and barrier properties compared to neat polymers. Fine dispersion of graphitic fillers depends on selection of the appropriate fabrication technique including solution mixing; melt blending and in-situ polymerization. The corresponding significance of polymer/graphite-based nanomaterials, challenges, exploitation and future aspects of the materials is overviewed.     

A study of localized curing of glass‐filled composites using microhardness measurements

Extent of cure of hybrid composite systems is examined by conducting hardness measurements at different stages of the photopolymerization reaction and obtaining kinetic parameters that matched the experimental data. The materials are commercial dental composites based on bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]propane resins with different photoinitiator concentrations as well as filler particle sizes and combinations. Samples (five per group) were made using nylon molds (2.5 × 5 mm) of the tested composites. The samples were light cured with a constant‐power light source for durations up to 20 s. After curing, all samples underwent Vicker's hardness testing of top and bottom surfaces. While there are significant differences in the polymerization behavior between the top and bottom locations for the tested composites, the corresponding growth exponent n, a kinetic parameter in the kinetic theory, is very close in all cases. For the tested materials the coefficient factor k is much lower for the bottom surfaces compared with the top surfaces. This reduction in the value of k is more severe for the material with a higher concentration of the photoinitiator as well as a higher percentage of glass filler particles in the wavelength range affecting the photopolymerization. It is argued that a relationship between k and the irradiation intensity can be used to quantify the decay of irradiated light with its penetration into the composites. The comparisons can be used to draw preliminary conclusions on the parameters controlling the effective depth of cure in a hybrid composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 426–431, 2005     

聚合填充型超高分子质量聚乙烯复合材料的结构与性能

介绍了采用聚合填充工艺,分别以硅藻土、高岭土为填料,制成的超高分子质量聚乙烯复合材料。结构形态研究表明,该复合材料中填料粒子与聚合物基体之间界面结合力以及填料粒子的分散性均好于共混型材料。该复合材料不但保持了超高分子质量聚乙烯的绝大多数优点,还大大弥补了它的一些不足。     

Polymerization of styrene using N-(p-tolyl)-N′,N′-diethyldithiocarbamoylacetamide as photoiniferter

N-(p-Tolyl)-N′,N′-diethyldithiocarbamoylacetamide was prepared and used as a new photoiniferter for polymerization of styrene in bulk under UV light. This photopolymerization showed some specific character, i.e., molecular weights of resulting polymers increase with reaction time and monomer conversion, respectively. The reversible reaction between growing radical and dormant species was confirmed by electron spin resonance using 2-methyl-2-nitrosopropane as a spin trapping agent. Thus, the end functionalized polymer, N,N-diethyldithiocarbamoyl-terminated polystyrene, reinitiated photopolymerization of methyl methacrylate and vinyl acetate to form block copolymers. The molecular weight distribution about 2.7 indicated that the polymerization is not a strictly living radical polymerization. © 1996 John Wiley & Sons, Inc.     

Reinforcement effects in fractal-structure-filled rubber

A quantitative morphological analysis has been performed using AFM and SAXS measurements in order to determine the spatial distribution of fillers in silica SBR composites. The proportion of fillers in agglomerates or aggregates of silica has thus been separated. Additional measurements have been carried out to quantify the amount of modified polymer in the vicinity of the filler surface, i.e. the bound rubber. It is shown that the reinforcing phase, constituting both silica particles and bound rubber, can be considered either as the dispersed or the continuous phase depending on the filler content.The linear dynamic mechanical properties of composites are then analysed. The variations of the shear modulus as a function of the filler content are then related to either the reinforcement effect induced by fillers or the development of specific additional interactions between phases, i.e. the interface effects. To separate the respective contribution of these effects from the overall dynamic behaviour of composites, micromechanical modelling is then performed. In a first step, the viscoelasticity of composites reinforced by 5.7 vol% of silica is predicted with the help of Christensen and Lo's model. For composites filled with 10 and 15 vol% of silica, self-consistent modelling, applied in a reverse mode, confirmed that the reinforcing phase, i.e. silica particles and bound rubber, acts as the continuous phase, in agreement with the morphological analysis. From the predicted dynamic mechanical properties of the reinforcing phase, the bound rubber behaviour is thus extracted as a function of the filler content and compared to that of unfilled SBR.     

Physicochemical characterization of the filler–matrix interface in elastomer‐encapsulated fly ash/polyester particulate composites

An attempt was made to improve the toughness of fly ash (FA)/general‐purpose unsaturated polyester resin (GPR) composites. Elastomer [styrene–butadiene rubber (SBR) or acrylic copolymer (AC)]‐encapsulated fillers (FA or CaCO₃) were made through the coagulation of the emulsified elastomer containing the filler with constant stirring. The elastomer‐encapsulated fillers were added to GPR at concentrations as high as 15 wt % to make FA/SBR or AC/GPR composites. The mechanical properties (i.e., the tensile strength, tensile modulus, tensile elongation, flexural strength, flexural modulus, impact strength, and hardness) of FA/GPR, FA/SBR/GPR, and FA/AC/GPR composites were studied. The tensile‐fractured surfaces of all the composites were studied with scanning electron microscopy. The thermal stability was studied with thermogravimetric analysis. An analysis of the results indicate that this modification technique is rather easy and more economical than the chemical modification of filler surfaces with functional silane coupling agents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 171–184, 2005     

Correlated electrical conductivity and mechanical property analysis of high-density polyethylene filled with graphite and carbon fiber

The development of conductive polymer composites remains an important endeavor in light of growing energy concerns. In the present work, graphite (G), carbon fiber (CF) and G/CF mixtures are added to high-density polyethylene (HDPE) to discern if mixed fillers afford appreciable advantages over single fillers. The effects of filler type and composition on electrical conductivity, composite morphology and mechanical properties have been examined and correlated to establish structure-property relationships. The threshold loading levels required for G and CF to achieve measurable conductivity in HDPE have been identified. Addition of CF to HDPE/G composites is found to increase the conductivity relative to that of HDPE/G composites at the same filler concentration. This observed increase depends on CF length and becomes more pronounced at and beyond the threshold loading of the HDPE/G composite. Scanning electron microscopy is employed to elucidate the morphology of these multicomponent composites, whereas dynamic mechanical analysis reveals that filler concentration, composition and CF length impact both the magnitude and temperature dependence of the dynamic storage modulus.     

Comparative study of aluminum diethylphosphinate and aluminum methylethylphosphinate‐filled epoxy flame‐retardant composites

Epoxy resin (EP) is one of the main polymers in electrical and electronic applications. In this work, flame‐retardant epoxy resin composites based on aluminum diethylphosphinate (Al(DEP)) and aluminum methylethylphosphinate (Al(MEP) were prepared using aromatic amine 4, 4‐diaminodiphenylmethane as curing agent. The flammability, thermal degradation, flexural properties, and morphologies of composites were investigated with respect to the filler loading and filler type. Results showed that both Al(MEP) and Al(DEP) were efficient flame retardants for EP and a low dosage (15 wt%) is enough to achieve the important criterion UL 94 V‐0. Limiting oxygen index (LOI) of composites is increased with filler loading (phosphorus content) and reached of 32.2% for 15 wt% of Al(MEP) and 29.8 for 15 wt% of Al(DEP). The char formation and flexural modulus of composites are also improved by adding the two fillers. However, the flexural strength of all the composites decreased with increasing filler loading. In comparison with Al(DEP)/EP, Al(MEP)/EP provides a higher flammability, better thermal stability and char formation but inferior flexural properties. Scanning electron microscopy revealed that the dispersion of Al(DEP) filler in the EP matrix is more uniform and exhibits better compatibility with EP matrix, which in turn generates better flexural strength and higher modulus when compared with Al(MEP)‐filled EP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Extrinsic conducting and superconducting polymer systems. III. Electrical properties of PVDF/PS blends containing copper,carbon black,and YBaCuO fillers

In this work, the electrical characterization of three extrinsic polymeric conducting systems was carried out using complex impedance spectroscopy. These systems were obtained by the incorporation of conducting fillers (carbon black and metallic copper), on the one hand, and, on the other hand, by blending with a superconducting ceramic (YBaCuO). The experimental results prove that the electrical characteristics of these systems vary as a function of the nature of the filler added. In the case of metallic copper, the resulting composites posses a conductivity which is intermediate between insulating materials and semiconductors. When carbon black is incorporated in concentration above 10%, the composites may be considered as metalliclike from the point of view of conductivity. Finally, when the filler is YBaCuO, the low conductivity values obtained are indicative of insulating materials regardless of their composition. © 1996 John Wiley & Sons, Inc.