Effect of single‐mineral filler and hybrid‐mineral filler additives on the properties of polypropylene composites

The present study was carried out to determine the filler characteristics and to investigate the effects of three types of mineral fillers (CaCO₃, silica, and mica) and filler loadings (10–40 wt%) on the properties of polypropylene (PP) composites. The characteristics of the particulate fillers, such as mean particle size, particle size distribution, aspect ratio, shape, and degree of crystallinity were identified. In terms of mechanical properties, for all of the filled PP composites, Young's modulus increased, whereas tensile strength and strain at break decreased as the filler loading increased. However, 10 wt% of mica in a PP composite showed a tensile strength comparable with that of unfilled PP. Greater tensile strength of mica/PP composites compared to that of the other composites was observed because of lower percentages of voids and a higher aspect ratio of the filler. Mica/PP also exhibited a lower coefficient of thermal expansion (CTE) compared to that of the other composites. This difference was due to a lower degree of crystallinity of the filler and the CTE value of the mica filler. Scanning electron microscopy was used to examine the structure of fracture surfaces, and there was a gradual change in tensile fracture behavior from ductile to brittle as the filler loading increased. The nucleating ability of the fillers was studied with differential scanning calorimetry, and a drop in crystallinity of the composites was observed with the addition of mineral filler. Studies on the hybridization effect of different (silica and mica) filler ratios on the properties of PP hybrid composites showed that the addition of mica to silica‐PP composites enhanced their tensile strength and modulus. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Mechanical and Thermal Properties Modeling,Sorption Characteristics of Multiscale (Multiwalled Carbon Nanotubes/Glass Fiber) Filler Reinforced Polypropylene Composites

The present work was aimed to investigate the individual and hybrid reinforcement effect of multiscale fillers [glass fibers (GF)/multiwalled carbon nanotubes (MWCNTs)] in polypropylene (PP) matrix. The MWCNT content in the hybrid composites was varied from 0.5 to 5 wt%, and glass fiber fraction was fixed as 20 wt%. The morphology of nano and hybrid composite revealed reasonable dispersion of MWCNTs and glass fibers in the matrix. At a MWCNT content of 3 wt%, the optimum tensile properties for the hybrid composites were achieved and beyond which it declined due to agglomeration effects as revealed by transmission electron microscopy. A comparative study of the experimental and predicted values of moduli of nano, micro, and hybrid composites using various micromechanical models was conducted. The simultaneous incorporation of MWCNTs and glass fibers in PP restricted the mobility of polymer chains as indicated by the increase in storage modulus and rise in glass transition temperature obtained by dynamic mechanical analysis. The differential scanning calorimetry studies indicated that the inclusion of 2 wt% of MWCNTs increased the crystallinity of PP from 58.2 to 69.1% in hybrid composites. The Avrami and Mo models were used to explore nonisothermal crystallization kinetics, and Mo model was in close agreement with the experimental results. The sorption behavior of the composites revealed that the formation of immobilized regions developed by the simultaneous inclusion of micro and nano fillers delayed the transport of the solvent. J. VINYL ADDIT. TECHNOL., 25:E94–E107, 2019. © 2019 Society of Plastics Engineers     

Preparation of flexible transparent acryl/alumina nano-hybrid materials exhibiting low thermal expansion coefficient

In this study, flexible transparent hybrid films with low thermal expansion coefficient were prepared by combination of alumina fillers and polymerizable/non-polymerizable surface modifiers with carboxyl group. Four types of alumina fillers with different shape and size were used in this study, and could modify with surface modifiers containing carboxyl groups by electrostatic interaction and disperse homogeneously in resulting hybrid films regardless of the shape and size. So the hybrid films obtained showed high transmittance around 90%T, and it was considered, from transmission electron microscopic analysis, alumina fillers were dispersed at near original filler size, without aggregation. Moreover, thermal mechanical analysis cleared that the use of pillar or fiber type filler is more effective to reduce CTE compared with plate type fillers, especially CTE of hybrid film prepared with fiber type filler was drastically decreased to 17 ppm/K, while the influence by the difference of filler shape/size was not observed on tensile properties, surface hardness. By use of fiber type alumina filler and combination of polymerizable surface modifier and non-polymerizable surface modifier which seems to interact with matrix, for optimizing of the crosslink density, it was possible to reduce CTE, while the good mechanical properties was kept. Finally, hybrid film indicating low CTE value as 19 ppm/K, high flexibility (windable against 0.4 mm radius steel bar), and good tensile properties and surface hardness which were equal to or higher than those of matrix could prepared.     

Investigation of the dynamic mechanical behavior of polypropylene/(wood flour)/(kenaf fiber) hybrid composites

Polypropylene/(wood flour)/(kenaf fiber) hybrid composites were prepared in an internal mixer. Kenaf was considered as a fibrous filler and wood flour as a particulate filler. The lignocellulosic loading used was 50%. Dynamic mechanical thermal analysis properties such as storage modulus (E′), loss modulus (E″), damping factor (tan δ), and adhesion factor were evaluated. It was found that the adhesion factor could interpret the interfacial adhesion between lignocellulosic fillers and the plastic matrix macroscopically. This factor was affected by the type of filler used and the coupling agent concentration. The variation of storage modulus was affected more by the shape of the filler and the coupling agent concentration at higher temperatures than at temperatures below the glass transition. Owing to a higher probability of agglomeration in a sample containing 50 wt% of wood flour, the storage modulus and complex viscosity of this sample were higher than those of other samples. Cole‐Cole diagrams showed that the homogeneity of samples containing a higher amount of coupling agent was higher than that of samples with a lower concentration. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

3D printing of copper particles and poly(methyl methacrylate) beads containing poly(lactic acid) composites for enhancing thermomechanical properties

Poly(lactic acid) (PLA) composite filaments with different copper (Cu) contents as high as 40 and 20 wt% of poly(methyl methacrylate) (PMMA) beads have been fabricated by twin-screw extruder for 3D printing. A fused-deposition modeling (FDM) 3D printing technology has been used to print the PLA composites containing hybrid fillers of Cu particles and PMMA beads. The morphology, mechanical, and thermal properties of the printed PLA composites were investigated. The tensile strength was slightly decreased, but storage modulus and thermal conductivity of PLA composites were significantly improved by adding Cu particles in the presence of PMMA beads. The PLA composites with hybrid fillers of 40 wt% of Cu particles and 20 wt% of PMMA beads resulted in thermal conductivity of 0.49 W m⁻¹ K⁻¹ which was three times higher than that of the bare PLA resin. The facilitation of the segregated network of high-thermally conductive Cu particles with the PMMA beads in PLA matrix provided thermally conductive pathways and resulted in a remarkable enhancement in thermal conductivity.     

Single and hybrid mineral fillers (talc/silica and talc/calcium carbonate)‐filled polypropylene composites: Effects of filler loading and ratios

Properties of single and hybrid fillers with polypropylene (PP) composites were studied in this research work. The effect of filler loadings of three types of mineral fillers, namely talc, silica, and CaCO₃, was investigated. In hybrid composites systems, the effect of silica/talc (SI/T) and CaCO₃/talc (CC/T) filler ratios at 40 wt% was determined. Generally, the results demonstrated that SI/T has higher modulus than CC/T but both hybrids did not have a significant effect on PP strength. In thermal properties, both hybrids have a nucleating ability as they increase the crystallization temperature and onset of crystallization temperature of PP. Results of analysis by TGA revealed that SI/T increased thermal stability of PP composites more than CC/T. Better flammability of the SI/T system is exhibited by lower burning rates of SI/T than CC/T, which indicates better thermal stability of the hybrid system. J. VINYL ADDIT. TECHNOL., 20:160–167, 2014. © 2014 Society of Plastics Engineers     

Aluminum oxide particles/silicon carbide whiskers’ synergistic effect on thermal conductivity of high-density polyethylene composites

Aluminum oxide (Al₂O₃) particles and silicon carbide (SiC) whiskers improved the thermal conductivity of high-density polyethylene (HDPE). To improve the dispersion of inorganic fillers in the matrix, 5 wt% of maleic anhydride-modified polyethylene was added into HDPE as a compatibilizer, and the hybrid matrix was denoted as mHDPE. The thermal conductivity, heat resistance, and tensile properties of resulting HDPE composites were characterized. The results showed that the thermal conductivity reached its maximum value of 0.8876 W/(m K) at 1/4 weight ratio of Al₂O₃/SiC, which was 110.3, 54.8, and 8.8% higher than that of pure HDPE, mHDPE/Al₂O₃, and mHDPE/SiC composites, in the order given, indicating that hybrid fillers have synergistic effect on the thermal conductivity of HDPE composites. Moreover, they also have a synergistic effect on the heat resistance and Young’s modulus. As the SiC content increases, the heat resistance of the composites increases at first and then falls, and the maximum VST is reached at an Al₂O₃/SiC weight ratio of 3/2, which is 5.4 °C higher than that of HDPE. The maximum Young’s modulus of the composites (1160 MPa) is obtained at an Al₂O₃/SiC weight ratio of 1/4, and the yield strength increases gradually as the SiC whiskers’ content increases.     

Effect of Particle Size of Mica on the Properties of Poly[Ether Ether Ketone] Composites

A study on high performance PEEK composites prepared by incorporating with three different particle sizes of mica was fabricated by compression molding. The effects of particle size of mica on the mechanical, thermal and morphological properties were studied. The incorporation of mica increased tensile modulus. The percentage crystallinity of PEEK mica composites was studied by using modulated DSC. The storage modulus changed significantly with the variation of the mica particle size and content in the PEEK matrix. Composite containing 20 wt% mica exhibited about a 79% increase in the storage modulus at 50°C and about a 68% increase at 250°C.     

Influences of nanoparticle content on electrical and thermal performances of micro-nano hybrid composites for packaging materials

This paper presents electrical and thermal properties of a novel type of micro-nano hybrid composites to be potential for packaging. The micro-nano hybrid composites contain 20 wt% of micro-aluminium nitride (AlN) with 1, 3, and 5 wt% of nano-AlN, respectively. Electrical measurement and thermal analysis are used to analyze the performances. The results show that the nano-AlN in the hybrid composites can suppress the space charge accumulation near the cathode and facilitate the conversion of hetero charge into the homo-charge accumulations near the anode. No apparent electric field distortion can be observed in the M20N3 sample, whereas it exhibits a minimum electrical conductivity and highest thermal conductivity amongst all samples. Furthermore, the nano-filler addition can enhance the DC breakdown strength and the thermal stability of the hybrid composites. The thermal and electrical conduction mechanism of the micro and nano fillers in the hybrid composites is also elucidated.     

Studies on Mechanical,Thermal, and Flame Retarding Properties of Polybutadiene Rubber (PBR) Nanocomposites

An effect of nanosize CaCO₃ on physical, mechanical, thermal and flame retarding properties of PBR was compared with commercial CaCO₃ and fly ash filled PBR. CaCO₃ at the rate of 9, 15, and 21 nm were added in polybutadiene rubber (PBR) at 4, 8 and 12 wt.% separately. Properties such as swelling index, specific gravity, tensile strength, Young's modulus, elongation at break, modulus at 300% elongation, glass transition temperature, decomposition temperature, flame retardency, hardness, and abrasion resistances were determined. The swelling index decreased and specific gravity increased with reduction in particle size of fillers in PBR composites. There was significant improvement in physical, mechanical, thermal and flame-retarding properties of PBR composites due to a reduction in the particle size of fillers. Maximum improvement in mechanical and flame retarding properties was observed at 8 wt.% of filler loading. This increment in properties was more pronounced in 9 nm size CaCO₃. The results were not appreciable above 8 wt.% loading of nano fillers because of agglomeration of nanoparticles. In addition, an attempt was made to consider some thermodynamically aspects of resulting system. The cross-linkage density has been assessed by Flory-Rehner equation in which free energy was increased with increase in filler content.     

A Novel Polymeric Coating with High Thermal Conductivity

A novel polymeric coating with high thermal conductivity was prepared using a hydroxyl-terminated polydimethylsiloxane-modified epoxy resin and hybrid aluminum nitride (AlN) particles with various sizes. It was found that the coating exhibited a maximum thermal conductivity of 1.78 W/m K at 50 wt% filler content and a preferable mass ratio. This was a result of the synergistic effect of hybrid fillers giving rise to a better heat conduction capability as opposed to a coating without fillers. Furthermore, thermogravimetric analysis revealed that the coating exhibited an excellent high temperature resistance owing to the modified matrix and interaction between filler and matrix; and a dielectric study demonstrated that the dielectric constant, volume resistivity and dielectric strength of the coating at 50 wt% filler concentration were 5.6, 8.2 × 10¹³ Ω·cm and 12 kV/mm, respectively. In addition, the mechanical properties declined obviously with filler content.     

Dynamic mechanical analysis and morphological studies of fly ash/mica reinforced poly(ether‐ether‐ketone)‐based hybrid composites

Hybrid composites based on poly(ether‐ether‐ketone) (PEEK) were fabricated with fly ash and mica. Nearly 5, 10, and 15 wt% of fly ash were replaced by mica of the optimized fly ash reinforced composites and were subjected to dynamical mechanical analysis to determine the dynamic properties as a function of temperature. The storage modulus E′ was found to decrease with the increase of weight fraction of mica. Loss modulus was also found to decrease with loading while the damping property was found to increase marginally. Peak height of tan δ for hybrid composites were decreased by varying combinations of fly ash with mica. It is probably due to improved crystallinity of PEEK and strong interaction between the fillers and PEEK matrix. Cole–Cole analysis was made to understand the phase behavior of the composite samples. Kubat parameter was calculated to study the adhesion between matrix and filler of the fabricated composites. Without surface modification for inorganic fillers, the distribution of two different shape filler particles appears to be reasonably uniform. The use and limitation of various theoretical equations to predict the tan δ and storage modulus of filler reinforced composites have been discussed. Addition of both fillers opens up new opportunities for development of high‐performance multifunctional materials suitable for industrial applications. Scanning electron micrographs of tensile fracture surfaces of composites demonstrated filler–matrix bonding. POLYM. COMPOS., 35:68–78, 2014. © 2013 Society of Plastics Engineers     

Melt-reprocessable linear low-density polyethylene/cyclic olefin copolymer blends with low dielectric constant and low thermal expansion

Insulation materials with low dielectric constants, low coefficients of thermal expansion (CTE), low densities, renewability, and low cost are urgently needed in the fields of communication, control and signal cables. Here we report that combining cyclic olefin copolymer (COC) with linear low-density polyethylene (LLDPE) by melt blending achieves the above goals. The dielectric constant and CTE of LLDPE/COC blends are minimized at 20 wt% COC content, reaching a value of 2.23 at 1000 Hz and 1.21 × 10⁻⁴ K⁻¹, respectively. The density of the blend increases by only 1.6% compared with LLDPE, whereas the tensile modulus increases by 56%, which is conducive to the blends to improve mechanical strength while preserving lightweight. The rheological tests show that the zero-shear viscosity, storage modulus, and loss modulus of the LLDPE/COC blends do not change much compared with pristine LLDPE, maintaining their good melt processability at 160°C. The cyclic rigid structure of COC causes a decrease in CTE, and the increase in free volume between molecular chains is responsible for the reduced dielectric constant. The present work provides a promising route to the design and fabrication of melt-reprocessable polymer composites with low dielectric constant and low thermal expansion.     

Synergistic effect of boron nitride and tetrapod‐shaped zinc oxide whisker hybrid fillers on filler networks in thermal conductive HDPE composites

In this paper, in order to investigate and predict the synergistic effect of the tetra‐needle‐shaped zinc oxide whisker (T‐ZnO) and boron nitride (BN) hybrid fillers in the thermal conductive high‐density polyethylene (HDPE) composites, the filler networks were studied through dynamic rheological measurement. Moreover, the crystallinity of the HDPE in the composites, and the thermal and electrical conductivity of the composites were also investigated. It was found that when the ratio of the BN and T‐ZnO in hybrid fillers was 20:10, the HDPE/hybrid fillers composite not only had the highest thermal conductivity but also can maintain the electrically insulating. Furthermore, the gel point of the HDPE/hybrid fillers composites was 11.2 wt%, and it was close to the 10 wt%. Therefore, the synergistic effect of the T‐ZnO and BN hybrid fillers in the HDPE/hybrid fillers composites can be successfully predicted through dynamic rheology date. Simultaneously, the Scanning electron microscope results showed that the T‐ZnO and BN particles can contact each other to form the thermal conductive paths so that the thermal conductivity of the HDPE can be enhanced through addition of the hybrid fillers. In addition, it was also found that the improved thermal conductivity of the HDPE/hybrid fillers composites was not because of a change in the crystallinity of the HDPE in the HDPE/hybrid fillers composites. POLYM. COMPOS., 38:1902–1909, 2017. © 2015 Society of Plastics Engineers     

Investigation of non-isothermal crystallization,dynamic mechanical and dielectric properties of poly(ether-ketone) matrix composites

ABSTRACT

Poly(ether-ketone)/hexagonal boron nitride (h-BN) composites reinforced with micrometer-sized h-BN particles were investigated. The composites exhibited glass transition temperature (T_g) and thermal stability over 160°C and 560°C, respectively. The melting point and peak crystallization temperatures of the composites decreased up to 17°C and 12°C, respectively. The linear CTE of the composites decreased both below and above the T_g. The storage modulus increased with increasing h-BN content at all temperatures (50–250°C). The composites possessed excellent dielectric properties with insignificant dispersion with increasing frequency. Thus, resultant composites are promising candidates for the printed circuit boards/electronic substrates.     

Preparation of nano‐reinforced thermal conductive natural rubber composites

Natural rubber (NR) composites highly filled with nano‐α‐alumina (nano‐α‐Al₂O₃) modified in situ by the silane coupling agent bis‐(3‐triethoxysilylpropyl)‐tetrasulfide (Si69) were prepared. The effects of various modification conditions and filler loading on the properties of the nano‐α‐Al₂O₃/NR composites were investigated. The results indicated that the preparation conditions for optimum mechanical (both static and dynamic) properties and thermal conductivity were as follows: 100 phr of nano‐α‐Al₂O₃, 6 phr of Si69, heat‐treatment time of 5 min at 150°C. Furthermore, two other types of fillers were also investigated as thermally conductive reinforcing fillers for the NR systems: (1) hybrid fillers composed of 100 phr of nano‐α‐Al₂O₃ and various amounts of the carbon black (CB) N330 and (2) nano‐γ‐Al₂O₃, the particles of which are smaller than those of nano‐α‐Al₂O₃. The hybrid fillers had better mechanical properties and dynamic performance with higher thermal conductivity, which means that it can be expected to endow the rubber products serving under dynamic conditions with much longer service life. The smaller sized nano‐γ‐Al₂O₃ particles performed better than the larger‐sized nano‐α‐Al₂O₃ particles in reinforcing NR. However, the composites filled with nano‐γ‐Al₂O₃ had lower thermal conductivity than those filled with nano‐α‐Al₂O₃ and badly deteriorated dynamic properties at loadings higher than 50 phr, both indicating that nano‐γ‐Al₂O₃ is not a good candidate for novel thermally conductive reinforcing filler. POLYM. COMPOS., 37:771–781, 2016. © 2014 Society of Plastics Engineers     

Noticeable viscosity reduction of polycarbonate melts caused jointly by nano‐silica filling and TLCP fibrillation

Nano‐SiO₂ was introduced into in‐situ composites of polycarbonate (PC) and a thermotropic liquid crystalline polymer (TLCP) using a twin‐screw extruder. The rheology of these composites was characterized with capillary rheometry, and the morphology of the dispersed TLCP observed with scanning electron microscopy. The rheological data revealed that the viscosity decrease of PC melts by only the addition up to 20 wt% TLCP remained smaller than 30%, while it became ～48% upon further addition of only about 1 wt% nano‐SiO₂ and larger than 60% upon ～9 wt% nano‐SiO₂ filling, in contrast to a 50% viscosity increase of PC melts with increase in nanosilica loading up to ～9 wt%. These silica‐filled composites exhibited markedly low viscosity, especially at relatively high shear rates. The morphology of TLCP extracted from unfilled and silica‐filled composites indicated that the largest viscosity reduction was correlated well with the fibrillation of TLCP droplets enhanced by nano‐SiO₂. The TLCP/SiO₂/PC composites exhibited rheological hybrid effect with fillers at nanometer scale. POLYM. ENG. SCI., 47:757–764, 2007. © 2007 Society of Plastics Engineers     

Glass fiber/carbon nanotubes/epoxy three‐component composites as radar absorbing materials

The use of micro or nano‐fillers to optimize the properties of epoxy resins has become a common practice. The Carbon nanotubes (CNT) are considered excellent fillers because of their strength, stiffness, thermal conductivity, electrical capacity, and thermal stability, along with large electromagnetic wave absorption capability in the microwave range. In this work, electromagnetic absorption properties and dynamic‐mechanical response obtained with the incorporation of CNT into glass fiber/epoxy composites have been studied. A novel procedure to disperse and deposit CNT onto glass fiber fabrics has been developed to reach high overall content of CNT in the composite (4.15 wt%). Storage modulus increased with the incorporation of CNT, especially when they had also been incorporated into the epoxy, and for higher frequency (3 Hz). The response of the composites to electromagnetic radiation has shown an increasing trend for higher CNT content (up to 2 wt%), reaching an excellent attenuation value of up to −18.3 dB (98.5% of absorption). POLYM. COMPOS., 37:2277–2284, 2016. © 2015 Society of Plastics Engineers     

Polyetheretherketone composites reinforced with surface modified mica

Mica fillers reinforced polyetheretherketone (PEEK) composites were fabricated using compression molding technique. To improve embedding of the mica within the PEEK matrix, the mica surface was chemically modified using vinyl trimethoxysilane (VTMO), at variable concentration (0–1.5 wt%). The performance characteristics and treated mica PEEK at mica loading of 20 wt% composites were examined in terms of scanning electron microscopy, dynamic mechanical thermal analysis, and modulated differential scanning calorimetry. The tensile strength and modulus improved to the tune of 81 and 44% with treated mica‐filled PEEK composites. Mechanical tests revealed improved properties of VTMO‐treated mica/PEEK composites, which confirmed improved interfacial adhesion with chemical treatment. The increment of the dynamic modulus for the treated mica PEEK composites was also noticed to 82% as compared with untreated counterpart, at elevated temperatures of 250°C, indicating apparent improvement of high‐temperature mechanical properties. POLYM. COMPOS., 31:2121–2128, 2010. © 2010 Society of Plastics Engineers     

Mechanical,thermal, and dielectric properties of aluminum nitride/glass fiber/epoxy resin composites

The treated hybrid fillers of aluminum nitride/glass fibers (AlN/GF) were performed to prepare the AlN/GF/epoxy composites by casting method. Results showed that the flexural and impact strength of the composites were increased firstly, but decreased with the excessive addition of AlN. The mechanical properties were optimal with 5 wt% treated AlN. The thermal conductivities of the composites were improved with the increasing content of AlN, and the thermal conductive coefficient λ was 1.412 W/mK with 70 wt% treated AlN, about seven times higher than that of pure epoxy resin. The dielectric constant and dielectric loss of the composites were increased with the increasing content of AlN. For a given AlN/GF hybrid fillers loading, the surface treatment of AlN/GF hybrid fillers exhibited a positive effect on the mechanical properties and thermal conductivities of the composites. POLYM. COMPOS., 35:381–385, 2014. © 2013 Society of Plastics Engineers