Increase In Filler Loading Research Articles

Thermal Conductivity of UltemTM/Carbon Nanofiller Blends

In an effort to improve polymer thermal conductivity (TC), UltemTM 1000 was compounded with nano-fillers of carbon allotropes. As-received and modified multiwalled carbon nanotubes (MWCNTs), vapor-grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Functionalization of MWCNTs was performed to improve the TC compatibility between the resin and MWCNTs. It was postulated that this may provide an improved interface between the MWCNT and the polymer which would result in enhanced TC. The nano-fillers were mixed with UltemTM 1000 inthemeltandinsolution at concentrations ranging from 5 to 40 wt.%. Ribbons were extruded from the blends to form samples where the nano-fillers were aligned to some degree in the extrusion direction. Samples were also fabricated by compression molding resulting in random orientation of the nano-fillers. Thermal properties of the samples were evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TGA). Tensile properties of aligned samples were determined at room temperature. As expected, increased filler loading led to increased modulus and decreased elongation with respect to the neat polymer. The degree of dispersion and alignment of the nano-fillers was determined by high-resolution scanning electron microscopy (HRSEM). The HRSEM of the ribbons revealed that the MWCNTs and CNFs were predominantly aligned in the flow direction. The TC of the samples was measured using a NanoflashTM instrument. Since the MWCNTs and CNF are anisotropic, the TC was expected to be different in the longitudinal (parallel to the nanotube and fiber axis) and transverse (perpendicular to the nanotube and fiber axis) directions. The largest TC improvement was achieved for aligned samples when the measurement was performed in the direction of MWCNT and CNF alignment (i.e. longitudinal axis). Unaligned samples also showed a significant improvement in TC and may be potentially useful in applications when it is not possible to align the nano-filler. The results of this study will be presented.

AC impedance analysis and EMI shielding effectiveness of conductive SBR composites

Flexible conductive polymer composites were prepared using styrene–butadiene rubber (SBR) as a matrix and conductive carbon black as filler. The filler loading was varied from 10 to 60 phr. The complex AC impedance and electromagnetic interference shielding effectiveness (EMI SE) of the composites were measured at the microwave frequencies of 7.8–12.4 GHz. The effect of variation in filler concentration and measurement frequency on the AC impedance and EMI SE of the composites were investigated. Equivalent circuits describing the conduction behavior of the composites were determined by means of Nyquist plots. The complex electric modulus of the composites was also determined. Increase in the filler loading increased the capacitive nature of the materials. The composites were better defined by a parallel resistor–capacitor circuit in series with a resistor. The EMI SE was found to pass through a maximum with increase in frequency. However, with the increase in filler loading and sample thickness of the material, the EMI SE was found to increase continuously. POLYM. ENG. SCI., 46:1342–1349, 2006. © 2006 Society of Plastics Engineers.

Kinetics of thermal degradation and thermo-oxidative degradation of conductive styrene-butadiene rubber-carbon black composites

The kinetics of the thermal degradation and thermo-oxidative degradation of conductive styrene-butadiene rubber (SBR)-carbon black composites were investigated using thermogravimetric analysis both in nitrogen and oxygen atmospheres. Experiments were carried out at heating rates of 5, 10, 15 and 20 °C/min in both the atmospheres. Friedman method, Kissinger method, Flynn–Wall–Ozawa method and Coats–Redfern method have been used to determine the activation energies of degradation. The invariant kinetic parameters using the IKP method were also determined. The results showed that the thermal stability of the composites in pure nitrogen is higher than that in air atmosphere and the increase in filler loading was found to increase the thermal stability in nitrogen atmosphere. The probable degradation mechanisms of the polymer in both the atmospheres were evaluated based on Fourier Transform Infra Red Spectroscopy (FT-IR) studies.

Study and characterization on the nanocomposite underfill for flip chip applications

The nanosilica filled composite is a promising material for the no-flow underfill in flip-chip application. However, as the filler size decreases into the nano length scale, the rheological, mechanical, and thermal mechanical properties of the composite change significantly. The filler-filler and filler-polymer interactions have a profound impact on the material properties. The purpose of this paper is to achieve an in-depth understanding of the effect of the filler size and surface treatment on material properties and therefore to design a nanocomposite formulation with desirable material properties for no-flow underfill applications. Mono-dispersed nanosilica filler of 100nm in size were used in this study. An epoxy/anhydride mixture was used as the base resin formulation. The nanosilica fillers were incorporated into the resin mixture to different filler loadings from 5wt% to 40wt% with or without silane coupling agents as the surface treatment. UV-Visible spectroscopy showed that the underfills with nano-size filler were transparent in the visible region even at high filler loading. The curing behavior and the Tg of the nanocomposite were studied using a modulated differential scanning calorimerter. It was found that the presence of the nanosilica could hinder the curing reaction, especially at the late stage of cure. The Tgs of the nanocomposites with untreated silica were found to decrease with the increasing filler loading. The measurement of the dynamic moduli from dynamic mechanical analyzer indicated that there was a secondary relaxation related to the filler-polymer interface. The coefficient of thermal expansion of the nanocomposite was measured using a thermal mechanical analyzer. The rheology of the nanocomposite was studied using a stress rheometer. It was found that the filler treatment could significantly reduce the viscosity of the nanocomposite and improve the processing capability of the underfill. Density measurements and moisture absorption experiments both indicated that the addition of nanosilica could increase the free volume of materials. The dispersion of the nanosilica in the cured composite materials was observed using scanning electron microscopy. Control samples with micron-size silica fillers were formulated and characterized for comparison.

Physico-mechanical, dynamic mechanical, and swelling properties of sodium chloride filled chlorobutyl vulcanizates

The effect of addition of rigid, nonreinforcing, and noninteracting filler viz. finely ground NaCl in chlorobutyl vulcanizates on properties such as physicomechanical, dynamic mechanical, and swelling has been studied. The nonreinforcing effect of NaCl in the system was studied by Russel and Cunnenn analysis and Kraus plots. Mechanical measurements of stress and strain at the break of filled and unfilled samples showed no appreciable change in the mechanical behavior of the system. The dynamic mechanical analysis showed that there is no change at all in the glass transition temperature with addition of NaCl filler. The damping properties showed an increase with increase in filler loading because of the filler–filler friction. The swelling behavior of NaCl-filled CIIR was studied for a period of 60 days in four different solvents of varying chemical energy potential viz. water, chloroform, acetone, and tetrahydrofuran (THF). The degree of swelling was found to increase continuously with time in water, which is a good solvent for the filler, and in THF, which is a good solvent for the polymer matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 707–714, 2006

Maleated natural rubber as a coupling agent for paper sludge filled natural rubber composites

Paper sludge filled natural rubber composites were prepared by incorporation of different loadings (10–40 phr) of paper sludge fillers. Two series of composites were studied, i.e. composites with and without maleic anhydride grafted natural rubber (MANR). Grafting of maleic anhydride onto the natural rubber was done prior to compounding using an internal mixer. The curing characteristics, dynamic properties and tensile properties of the composites were studied. Results indicate that the scorch time and cure time decrease with increasing filler loading whereas the maximum torque, viscous torque and tan delta exhibit an increasing trend. Increasing paper sludge content also increases the tensile modulus but the tensile strength and elongation at break decrease slightly. As the filler loading increases, the rubber–filler interactions of the composites decrease. The interfacial interaction of paper sludge filler and natural rubber matrix was enhanced by the addition of MANR, as exhibited by the tensile fracture surfaces of the composites using a Scanning Electron Microscope (SEM) and rubber–filler interaction studies. The presence of MANR has prolonged the curing time and scorch time and enhanced the tensile properties. The viscous torque and tan delta values also decrease with the addition of MANR.

Effect of Nanoclay on the Dynamic Mechanical Properties of Styrene Butadiene and Acrylonitrile Butadiene Rubber Vulcanizates

Abstract Nanocomposites based on Styrene Butadiene Rubber (SBR) and Acrylonitrile Butadiene Rubber (NBR) with varying acrylonitrile contents (19%, 34% and 50%, respectively) and octadecyl amine modified and unmodified Na-Montmorillonite clays were prepared. Dynamic mechanical thermal analysis (DMTA) was performed on these composites over a range of temperatures (−80 °C to +80 °C), frequencies (0.032 Hz to 32 Hz) and strains (0.001% to 10%). The results showed that there were significant changes in tan delta peak temperature and height and storage modulus with the addition of small amount (4 phr) of the modified and the unmodified fillers. These were magnified with the increase of filler loading. The tan delta peak heights decreased and the storage modulus increased in general. With increasing strain, the nanocomposites showed lowering of storage modulus, because of the breakdown of the agglomerated structures. The torage modulus increased with increasing frequency, and the modified filler loaded samples registered higher E' values compared to those of the gum rubber.

Tensile properties of polyethylene-layered silicate nanocomposites

The sodium ions of clays with different cation exchange capacities (CEC) have been exchanged with alkyl ammonium ions, in which 1–4 octadecyl chains are attached to the nitrogen atom. Due to the different cation cross-sectional area to available area per cation ratio, the resulting organo-montmorillonites (OMs) have different organic surface coverage and alkyl chain packing density. Nanocomposites of these OMs and HDPE were prepared and the influence of the organic monolayer structure on the exfoliation of montmorillonite and the tensile properties of the composites was studied. A high cation cross-sectional area to available area ratio led to complete surface coverage and large d-spacing, favoring the dispersion of the filler. In spite of the identical chemical structure of the polymer and the organic monolayer, complete exfoliation was not attained. Partial exfoliation was achieved without a compatiblizer, which often adversely affect the mechanical properties of the composites. Enhanced exfoliation increased the elastic modulus and yield stress but decreased the yield strain and stress at break of the nanocomposites. Increased filler loading enhanced the elastic modulus but decreased all other tensile properties. The tensile properties were correlated to the volume fraction of the inorganic part of the OMs and not to the total volume of the OM. Fitting the elastic modulus data to the Halpin-Tsai equation showed that the fitting parameter in this equation is not only related to the aspect ratio of the inclusions.

A Comparison of the Mechanical Properties and Water Absorption Behavior of White Rice Husk Ash and Silica Filled Polypropylene Composites

This paper compares the processability, mechanical properties, and water absorption behavior of polypropylene (PP) composites filled with white rice husk ash (WRHA) and silica. It is shown that preparation of WRHA filled composites requires less energy than silica filled composites. WRHA-PP composites exhibit better impact properties while other mechanical properties are better in silica filled composites. WRHA-PP composites also showed a better resistance to the water absorption in comparison to silica composites. An increase in water uptake with increase in filler loading was observed for both fillers although the difference is not significant for WRHA-PP composites. The study further shows that the area of the specimen cut edges influences the water uptake. The effect of water uptake on tensile properties was also briefly examined.

Melt strength and extensibility of talc‐filled polypropylene

AbstractPolypropylene homopolymer melts containing up to 50 percent by weight of talc filler (24 vol%) were tested on a Gottfert Rheotens melt strength testing unit. Melt strength and drawability parameters were measured from these tests to evaluate changes in the extensional behavior of the melt induced by filler addition. It was found that the melt strength of the polypropylene was decreased for talc additions of less than 40 wt% (17.5 vol%) under all test conditions. Addition of 50 wt% talc improved the melt strength under all testing conditions. Drawability, defined as the stretch ratio at strand break, decreased with increased filler loading. The melt strength of all materials was found to decrease with increased temperature within the range 180°C to 210°C. The melt strength of all melts showed dependence on the test extrusion rate, and this dependence was well described by an exponential relationship. Highest dependencies were seen for the unfilled and 50 wt% talc‐filled polymer. While it was found that addition of 50 wt% talc provided improvement in melt strength, high melt strength alone was a poor indicator of the melt processability, as drawability was also regarded as an important consideration.

Rheological and mechanical properties of natural rubber reinforced with agricultural byproduct

AbstractCocoa pod powdered (CP) and Carbonized Cocoa pod powdered (CCP) sieved through 150 μm mesh were characterized in terms of loss on ignition, surface area, moisture content, and oil absorption and used as filler in compounding natural rubber and vulcanized using efficient vulcanization system. The processing and curing characteristics of the compound mixes were determined on a Monsanto Rheometer. Physical‐mechanical properties of the vulcanizates were measured as a function of filler loading. It was found that vulcanizates with 40–50% filler loading showed maximum tensile strength of 8.4 MPa for CP, and 9.5 MPa for CCP. Hardness showed increased with increased filler loading for all the compounds. The reinforcing ability of the cocoa pod husk is not much inferior when compared to Carbon Black, N330. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3718–3722, 2003

Mechanical Properties of Kenaf–Thermoplastic Natural Rubber Composites

Kenaf–thermoplastic natural rubber (Kenaf–TPNR) composites were developed and evaluated in this study. The kenaf was blended with TPNR and maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer in an internal mixer (Brabender). The mechanical properties of the composites were investigated by tensile, impact, flexural, and morphologic properties by scanning electron microscope (SEM). The incorporation of the kenaf fiber into the TPNR matrix resulted in an improvement in the tensile strength and Young's modulus. However, the maximum strain and impact strength decreased with increased filler loading. The better performance was attributed to the addition of MAPP due to improvements in the wetting of the filler surface. The addition of MAPP produced composites with improved tensile strength, Young's modulus, and flexural stiffness. SEM was employed to investigate the fiber surface, fiber pullout, and fiber–matrix interaction of composites.

Rheological behavior of brominated isobutylene‐co‐paramethylstyrene: Effect of fillers, oil and blending with EPDM

AbstractThe melt flow properties of unfilled and filled brominated isobutylene‐co‐paramethylstyrene (BIMS) were measured by means of a capillary viscometer at three different temperatures (90°C, 110°C and 130°C) and four different shear rates (61, 122, 245 and 306 s−1). The effect of addition of EPDM rubber on melt flow properties of unfilled BIMS was also studied. Evaluation of the processability was done by measuring the extrudate roughness (ER) of the extrudates obtained from the MPT. The viscosity of the systems decreased with the shear rate, indicating their pseudoplastic or shear thinning nature. As expected, the viscosity of BIMS increased with the addition of fillers and decreased with the addition of oil. For the neat systems, viscosity increased with the addition of EPDM, and the blends showed a positive deviation, indicating interdiffusion of the polymer chains across the phase boundaries. The activation energy of the filled systems at constant filler loading increased with increasing filler surface area (N330 > N550 > N774, each at 30 phr loading), and filler loading (50 > 30 > 10 phr, for N330) and decreased with the addition of oil (2.5 > 5.0 > 7.5 phr, for system containing 30 phr of N330). The silica filled system showed a higher activation energy and ER than the carbon black‐filled systems. With addition of N330 and N550 carbon blacks to BIMS, the extrudate roughness (ER) decreased, whereas it increased with the addition of N774 carbon black. With an increase in filler loading, ER initially increased and then decreased as compared to the neat system. For the filled systems, ER initially decreased up to 5 phr of oil, beyond which it increased.

Electromagnetic Interference Shielding Effectiveness of Hybrid Conductive Polymer Composite

Electromagnetic interference (EMI) shielding characteristics of ethylene vinyl acetate (EVA) and ethylene propylene diene (EPDM) and their 50: 50 blend filled with conductive carbon black and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100-2000 MHz and 8-12 GHz (X-band range). The return loss and the loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with increasing frequency. The SE also increases with the increase in filler loading. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composites. The SCF-filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results suggest that the fibre-filled (20 phr) composites can be used for the EMI shielding, as well as for some microwave applications.

THE COMPARISON PROPERTIES OF RECYCLE RUBBER POWDER, CARBON BLACK, AND CALCIUM CARBONATE FILLED NATURAL RUBBER COMPOUNDS

The effects of filler loading on the curing characteristics, swelling behavior, and mechanical properties of natural rubber compounds were studied using a conventional vulcanization system. Recycle rubber powder (RRP), carbon black (CB) (N550), and calcium carbonate (CaCO3) were used as fillers and the loading range was from 0 to 50 phr. Results show that the scorch time, t 2, and cure time, t 90, decrease with increase in filler loading. At a similar filler loading, RRP shows shortest t 2 and t 90 followed by CB and calcium carbonate. The tensile strength, tensile modulus, and hardness increase with increase in CB loading, whereas elongation at break, resilience, and swelling properties show opposite trend. For RRP and calcium carbonate filled natural rubber compounds, the tensile strength increases up to 10 phr and starts to deteriorate at higher filler loading. The other properties such as tensile modulus, hardness, elongation at break, resilience, and swelling percentage show a small change (increase or decrease) with increase in RRP and calcium carbonate loading in natural rubber compounds. Overall results indicate that RRP can be used as a cheapener to replace calcium carbonate in natural rubber compounds where improved mechanical properties are not critical.

Comparison of the mechanical properties of rice husk powder filled polypropylene composites with talc filled polypropylene composites

Unmodified and ground talc and rice husk (RHP) fillers were compounded with polypropylene (PP) separately in a Brabender plasticorder internal mixer at 180 °C and 50 rpm in order to obtain composites, which contain 0–60% php (per 100 part of polymer) of filler at 15% intervals. The Brabender torque development and the mechanical properties of the composites with reference to filler type and filler loading were investigated. In terms of mechanical properties, Young’s modulus and flexural modulus increased, whereas yield strength and elongation at break decreased with the increase in filler loading for both types of composite. Of these PP composites, the RHP composites exhibited lower yield strength, Young’s modulus, flexural modulus, and higher elongation at break than talc composites. Scanning electron microscopy (SEM) was used to examine the structure of the fracture surface and to justify the variation of the measured mechanical properties.

Nanocomposite Fibers

ABSTRACTNanocomposite fibers involve the concept of integrally dispersing nanosized particles of the second phase inorganic material into fiber forming polymers such as nylon or polyester. The material goal involves obtaining bi-phasic fibers with high mechanical stiffness and strength, electrical conductivity and/or enhanced other features such as thermal stability. Thus far, the main difficulties toward achieving nanocomposite fibers are: (1) the inability of obtaining large quantities of nanoparticles in a pure, un-agglomerated state and (2) obtaining a uniform, intimate dispersion of single entity nanoparticles in a fiber polymer matrix. These problems have been approached in the context of studying the properties of experimentally prepared nano-silica reinforced fibers and attempts to prepare carbon nanotube, CNT, containing fiber material. Modulus and tenacity tests on experimentally prepared nanosilica filled PET (polyethyleneterephthalate) fibers showed the silica nanoparticles reduced the modulus and tenacity (tensile strength) of the filled PET fiber materials. DSC and shrinkage studies on nano-silica/PET fiber show that polymer crystallinity is influenced by the presence of the silica nano-particles. Heats of melting are found to increase as the filler loading increases. In further shrinkage studies, the “shrinkage modulus” of these nanosilica/PET fibers was found to increase by the addition of silica nanoparticles. Attempts to prepare nylon reinforced CNTs (multi-wall) from a commercially available CNT/nylon resin “concentrate” failed due to the poor melt dispersion processing of the blended polymer. Only very weak CNT reinforced nylon fibers could be prepared.

WHITE RICE HUSK ASH FILLED ETHYLENE-PROPYLENE-DIENE TERPOLYMER/POLYPROPYLENE BLENDS: EFFECT OF DYNAMIC VULCANIZATION AND FILLER LOADING

The effect of dynamic vulcanization and influence of filler loading of white rice husk ash filled elastomer rich ethylenepropylene diene terpolymer and propylene blends were investigated. Blends with filler loading ranging from 0 to 60 php (Parts per hundred of total polymer by weight) were prepared in a Brabender plasticorder at 180°C and a rotor speed of 50 rpm followed by compression molding. The Brabender torque was used to investigate mixing progress. The mechanical properties of vulcanized blend systems were compared with those of the unvulcanized counterparts. The mechanical properties of the blends as a function of filler loading were also studied for both blend systems. Processability and recyclability of the blends were carried out to assess the thermoplastic characteristics of the blends. Brabender torque studies showed that dynamic vulcanization has a more significant effect on melt rheology than filler loading. It was also found that unvulcanized blends exhibited poor tensile properties, low hardness and high compression set. However, dynamically vulcanized blends exhibit mechanical properties, which are superior to those of unvulcanized blends. As filler loading increases, the hardness of the blends slightly increases whereas tensile properties, tear strength, and compression set deteriorates. Processability and the possibility of recycling of dynamically vulcanized blends with high elongation and low compression set indicate that dynamic vulcanization confers thermoplastic elastomeric properties to the blends. The study further revealed that white rice husk ash filled blends can also be dynamically vulcanized to achieve enhanced properties in a similar manner to the unfilled blends.

Integral passives for next generation of electronic packaging: application of epoxy/ceramic nanocomposites as integral capacitors

The consumer demand for product miniaturization with increased functionality and reliability is ever growing in the electronic industry. Integral passive is a novel emerging technology which is perceived as a possible alternative to discretes in fulfilling the next generation of packaging needs. Although, integral passive technology has been proven to be a viable option, there are several barriers for implementing this technology such as efficient circuit design with increased component density, qualification of new materials for integral passive components and substrates, time-to-market a new product, technology transfer and product scale up toward commercialization, and most importantly cost competitiveness. Integration of passive components on substrates imposes a major design and fabrication challenge and has been a subject of increasing interest in the packaging community today. In this paper, we address materials and processes for integral capacitors and their co-integration with integral resistors and inductors. Dielectric constant values in the range of 3.5–50 with increase in filler loading up to 50vol% are achieved in the epoxy nanocomposite system where the dielectric constant of the host polymer is limited to ∼3.5. The capacitors are relatively stable up to a frequency range of 120Hz to 100kHz. Feasibility of integration of capacitor components has been demonstrated through fabrication of several industrial prototype circuits. Materials and process issues for passive elements such as resistors, capacitors, and inductors and the need for developing alternative substrate materials have also been addressed in this paper.

Electromagnetic interference shielding effectiveness of carbon black and carbon fibre filled EVA and NR based composites

Abstract Electromagnetic interference (EMI) shielding characteristics of natural rubber and ethylene vinyl acetate filled with conductive carbon black (Vulcan XC-72) and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100–2000 MHz and 8–12 GHz (X-band range). The return loss and loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with the increasing frequency. The SE also increases with the increase in filler loading. The SCF filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results indicate that the composites having higher fibre loading (≥20 phr) can be used for the purpose of EMI shielding, as well as for some microwave applications.