Optimum Filler Content Research Articles

Mechanical Properties of Poly(ether ether ketone) Composites Reinforced by Carbon Nano-Platelet Chains and Nanoalumina

Carbon nanoplatelet and nanoalumina reinforced PEEK nanocomposites were fabricated by twin-screw extrusion followed by injection molding. The effect of the filler loading on mechanical properties, morphology, dielectric strength, and thermal stability of the composites has been analyzed. The mechanical properties were found to increase with nanoplatelet content up to 1% loading (optimum filler content) and after that, due to agglomeration of filler, slight decrease in properties were observed. For alumina-filled systems mechanical properties increased with increasing filler content due to the well-dispersed fillers in the composites. The modulus and toughness of alumina-filled composites were higher than platelet-filled composites.

Cellulose nanofibrils as filler for adhesives: effect on specific fracture energy of solid wood-adhesive bonds.

Cellulose nanofibrils were prepared by mechanical fibrillation of never-dried beech pulp and bacterial cellulose. To facilitate the separation of individual fibrils, one part of the wood pulp was surface-carboxylated by a catalytic oxidation using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as a catalyst. After fibrillation by a high pressure homogenizer, the obtained aqueous fibril dispersions were directly mixed with different urea–formaldehyde-(UF)-adhesives. To investigate the effect of added cellulose filler on the fracture mechanical properties of wood adhesive bonds, double cantilever beam specimens were prepared from spruce wood. While the highest fracture energy values were observed for UF-bonds filled with untreated nanofibrils prepared from wood pulp, bonds filled with TEMPO-oxidized fibrils showed less satisfying performance. It is proposed that UF-adhesive bonds can be significantly toughened by the addition of only small amounts of cellulose nanofibrils. Thereby, the optimum filler content is largely depending on the adhesive and type of cellulose filler used.

Fundamental Characterization of Engineering Properties of Gussasphalt Mixtures

Surfacing the deck of a steel bridge is costly and technically challenging and an improvement on the life of the surfacing would be of economic benefit to the bridge industry. The objective of this work was to improve both the durability and stiffness of the Gussasphalt mixture, one of the preferred surfacing materials for steel deck bridges around the world, by varying the binder types and binder and filler content to obtain the optimum mix. A three-stage characterization process was proposed for the Gussasphalt mix in this study. Fundamental characterization started with evaluation of the viscoelastic properties of binders, extended to the rheological behavior of asphalt-mineral filler mastics, and ended with investigation of the engineering properties of Gussasphalt mixture. The degree of stiffening was found to vary significantly with different types of mineral filler and bitumen. The addition of Trinidad Lake asphalt (TLA) to bitumen caused an increase in stiffness, and the stiffening effect was more pronounced at lower temperatures than at higher temperatures. The suitable concentration of TLA was found to be in the range of 20–30% by weight of the binder. The optimum filler content was determined according to the rheological properties and the formation of the critical network. The increase in moduli resulting from the addition of mineral fillers had the potential benefit of improving the resistance to rutting of the Gussasphalt mixture. This indicated the possible presence of physicochemical reinforcement between the binder and filler. Fillers that produced very significant stiffening effects, however, could result in brittle mixtures and difficulty in construction. The engineering properties of a Gussasphalt mix could be characterized by Lueer fluidity, indentation, bending, and wheel-tracking tests.

Characterization of Fly Ash Bituminous Concrete Mixes

Fly ashes were collected from 14 thermal power stations located in different parts of India and were characterized using simple tests like fineness modulus, specific gravity, Rigden voids, German filler test and methylene blue value test, and advanced tests like X-ray diffractometer, scanning electron microscope, and chemical analysis. These fly ashes were divided into four groups based on the above tests and then used as filler in bituminous concrete (BC) mixes. The stone dust, a conventional filler in India, was also used for comparing the results. Rheological properties of filler-bitumen (F/B) mastic prepared at different F/B ratios were determined from softening point test, viscosity test, and dynamic shear rheometer test. Strength and durability tests like Marshall stability, retained stability, tensile strength ratio, and static creep tests were conducted on BC mixes with five types of fillers and the results are analyzed and compared. The study indicated that all the four groups of fly ashes are suitable for use in BC mixes with fly ashes in group 4 having the best performance. The optimum filler content is 7% and properties of fly ash BC mixes are better than those of conventional mix.

Microwave absorbing properties of ternary linear low‐density polyethylene/carbonyl iron powder/carbon black composites

AbstractLinear low‐density polyethylene (LLDPE) was used as polymer matrix, carbonyl iron powder (CIP) and carbon black (CB) were used as fillers, and ternary composites with microwave absorbing properties were prepared by melt blending. Transmission electron microscopy was used to characterize the prepared samples. The absorbing ability (reflection loss) of the prepared composites was measured using the arch method, and the electromagnetic parameters of composites were determined by the transmission/reflection method. The filler contents of CIP and CB have effects on the absorbing peak positions and reflection loss, and there is the optimum filler content in composites to obtain the maximum microwave absorbing. The microwave absorption of LLDPE/CIP/CB composites comes from the combining contributions of the dielectric loss and the magnetic loss. The synergistic effects of CIP and CB effectively improve the microwave absorbing properties of polymer composites. CIP and CB are uniformly distributed in the polymer matrix. The theoretical calculation results of the absorbing ability are in agreement with the experimental results using the transmission line theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Quantitation of the reinforcement effect of silica nanoparticles in epoxy resins used in liquid composite moulding processes

Epoxy–silica nanocomposites are investigated for their suitability as a new type of matrix for fibre-reinforced polymers (FRP) using injection technology (LCM). The key focus is the determination of the processing characteristics of the nanocomposites. The silica nanoparticle content varies between 0 and 25 wt% for the high performance epoxy resin. Photon Cross Correlation Spectroscopy (PCCS) and Scanning Electron Microscopy (SEM) analysis performed on the liquid and cured epoxy–silica nanocomposites indicate a nearly homogeneous distribution of the nanoscaled silica in the epoxy matrix, even at rather high weight percentages. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with neat resin. Moreover, resin shrinkage and the thermal expansion (CTE) can be significantly reduced and the thermal conductivity increased. Concomitant the glass transition temperature remains nearly constant. The initial viscosity of the resin increases slightly depending on the nanoparticle content, while the gel-time slightly decreases. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. The optimum filler content is at approx. 25 wt% silica. Epoxy–silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.

Graphite nanoplatelet pastes vs. carbon black pastes as thermal interface materials

Comparison of graphite nanoplatelet (GNP) and carbon black (CB) pastes as thermal interface materials shows that the optimum filler content for attaining the maximum thermal contact conductance (copper proximate surfaces, roughness 15 μm) are 2.4, 15 and 2.4 vol.% for GNP, CB (Tokai) and CB (Cabot), respectively. Except for CB (Cabot), the optimum filler content is diminished when the roughness is decreased from 15 to 0.009 μm. Comparing the fillers at their respective optimum contents shows that (i) GNP is similarly effective as CB (Tokai) for rough (15 μm) surfaces, but is less effective than CB (Tokai) for smooth (0.009 μm) surfaces, and (ii) GNP is more effective than CB (Cabot) for rough surfaces, but is slightly less effective than CB (Cabot) for smooth surfaces. GNP gives higher thermal conductivity and greater bond line thickness than CB (Tokai or Cabot), whether the comparison is at the same filler content or at the respective optimum filler contents. In spite of the high thermal conductivity, the effectiveness of GNP is limited, due to the high bond line thickness. CB (Tokai) gives higher thermal conductivity than CB (Cabot), thus causing CB (Tokai) to be more effective than CB (Cabot).

Optimal Conditioning for the Preparation of HDPE-HA Composites in an Internal Mixer

ABSTRACT In the last years research and development of new materials and methods for bone repairing and substitution has been a priority in the biomedicine field. HDPE/Hydroxyapatite (HA) composites have been previously used successfully for such purposes. In this study, HDPE/HA composites prepared in an internal mixer were characterized. Mixing conditions, such as temperature and mixing rate, were optimized. Results showed that high mixing rates and lower temperatures improved the filler dispersion in the polymeric matrix. At optimal conditions composites with 10, 20, 30 pph of HA were prepared and their rheological, mechanical, thermal and thermodegradative properties were determined to establish the optimum filler content. Inclusion of HA particles decreased the melt flow index. The incorporation of HA also increased the Young's Modulus and strength at break and decreased the elongation at break due to elasticity loss. Thermal properties and initial degradation temperature were not affected with the inclusion of the filler but an enhancement in the activation energy was observed. A titanate coupling agent (Lica 12) was added to composites to improve the interfacial interactions. Lica 12 did not produce any variation in the mechanical and rheological behavior of composites. A slight decrease in composite crystallinity was detected for composites coupled with 0.5, 0.7 and 1.0% Lica 12. The thermal stability increased with the addition of the coupling agent.

Evaluation of marble waste dust in the mixture of asphaltic concrete

In the study the use of marble dust collected during the shaping process of marble blocks has been investigated in the asphalt mixtures as filler material. The samples having marble dust and limestone dust filler were prepared and optimum binder content was then determined by Marshall test procedure. Dynamic plastic deformation tests were carried out by using the indirect tensile test apparatus. Optimum filler content was then determined considering the filler/bitumen ratio and filler ratio. Test results showed that plastic deformation of marble waste is between the upper and the lower limits of grounded marbles. The study showed that marble wastes, which are in the dust form could be used as filler material in asphalt mixtures where they are available and the cost of transportation is lower than ordinary filler materials.

Tribological behaviour of UHMWPE/HDPE blends reinforced with multi-wall carbon nanotubes

This paper deals with the wear and creep resistance of a composite material consisting of ultra-high molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE) reinforced with multi-wall carbon nanotubes (MWCNTs). The CNT content was varied between 0.2 and 2 wt% to find the optimum filler content. The effect of a pre-treatment of the CNTs in boiling nitric acid on the wear resistance was studied. The wear tests were performed in a ball-on-prism tribometer against two types of polished steel (austenitic X5CrNi18-10 and martensitic 100Cr6). The static penetration of the ball into the composite material was measured beforehand. The results showed that carbon nanotubes can improve the wear performance of UHMWPE/HDPE composites. The specific wear rate of the composites decreased with increasing CNT content. The nanotubes can be dispersed in the matrix, however, nanotube aggregates also still exist. Further work is needed to improve the homogeneity of the nanotubes in the matrix.

Effect of matrix morphology on the wear and friction behavior of alumina nanoparticle/poly(ethylene) terephthalate composites

The friction and wear properties of poly(ethylene) terephthalate (PET) filled with alumina nanoparticles were studied. The nanoparticle loading was varied from 1 to 10 wt.%. The nanocomposite samples were tested in dry sliding against a steel counterface. The results show that the addition of nanoparticles can increase the wear resistance by nearly 2× over the unfilled polymer. The average coefficient of friction also decreased in many cases. The nanocomposites form a more adherent transfer film that protects the sample from the steel counterface, although the presence of an optimum filler content may be due to the development of abrasive agglomerates within the transfer films in the higher wt.% samples. This study varied both crystallinity and weight percent of filler in a PET matrix in an attempt to separate the effects of nanofillers and crystallinity on the tribology.

Characterization of nonconductive adhesives for flip-chip interconnection

For chip-level interconnection, nonconductive adhesive (NCA) is emerging as one of the promising substitutes for solder interconnection because of its inherent fine-pitch capability and environmental friendliness. The NCA interconnect relies on the mechanical connection between the contacts on the chip and corresponding contacts on the substrate enabled by the compressive stress created as the NCA epoxy cures. The degradation mechanism of NCA technology is, however, relatively less well understood compared to solder interconnects in terms of materials requirements for enhanced reliability performance. This study addresses the impact of material systems employed on the reliability of the packages. This involves characterization of NCA pastes in thermomechanical, hygroscopic swelling, and moisture diffusion properties. The reliability evaluation was carried out using electroless nickel/gold perimeter bumped test chips with daisy-chained connections. Analysis showed that interfacial delamination and open contact were the major failure modes in the NCA package. Pressure cooker test (PCT) performance was improved by using NCA with low-saturated moisture concentration, low coefficient of moisture expansion, and high adhesion. For better performance in the moisture sensitivity test (MST), the key properties required were high shear strength and low moisture diffusivity. Interestingly, filler content shows opposing behavior in the MST versus the PCT. Thus, optimum filler content must be found.

Cure Characteristics and Physicomechanical Properties of Calcium Carbonate Reinforcement Rubber Composites

Cure characteristics and physicomechanical properties of calcium carbonate, CaCO3, reinforced rubbers (NR, NBR) were studied. Minimum torque, maximumminimum torque, cure rate and the scorch and cure time of the prepared rubber compounds were assessed by using a Monsanto Oscillating Disc Rheometer (ODR100). Stress and strain at yield and at rupture before and after aging were determined by using a Zwick tensile testing machine (Model 1425). Results showed that cure time, cure rate index (CRI), maximum torque, stress and strain at yield demonstrated clearly the optimum filler content for each type of rubber. Values of the rubber-filler interaction parameter (m) were 0.585 and 0.175 for NR and NBR respectively and suggested good NR-filler interaction than that of NBR where the dilution effect of NBR becomes more significant as the filler loading is increased. The aging behavior (resistance to deterioration) of the prepared rubber compounds due to the prolonged exposure of γ-irradiation was estimated by plotting the percent-retained values of the physicomechanical properties at different γ-doses.

Limestone filler cement in low w/c concrete: A rational use of energy

The effect of limestone filler (up to 20%) on the degree of hydration, the volume of hydration products, and the optimal replacement of limestone filler in cement pastes at different w/cm ratios (0.25–0.50) were investigated by using a quadratic statistical model. The results show an increase in the degree of hydration in very low w/cm ratio paste when the limestone filler content is increased. However, the largest volume of hydration products occurs for high w/cm ratio pastes, for which the available space also increases with the limestone filler content. Finally, for a given cement, the optimum limestone filler content for different w/cm ratios can be obtained by using the gel–space ratio concept. In addition, concrete mixtures (w/cm=0.30 and 0.34) were made to determine the compressive strength. The results have shown that concretes containing limestone filler cements present a small reduction of strength at 28 days improving the hydration of clinker particles in the system. The strength of concrete depends on the gel–space ratio, which takes into account all of the effects produced by limestone filler addition: the increase of the degree of hydration, the dilution, and the increase of the effective w/c ratio.

Sorption of sulfur mustard and its oxygen analog in black and nonblack-filled butyl rubber membranes

Butyl rubber (IIR) membranes containing a 0–50% volume fraction of carbon black (GPF N660) or nonblack fillers (talc/precipitated CaCO3/fullers earth) were prepared by solution casting and evaluated for permeation resistance to the vesicant, bis(2-chloroethyl)sulfide, or sulfur mustard (SM) and its oxygen analog (OA), bis(2-chloroethyl)ether. The diffusivity of the chemicals was determined from the breakthrough time (BTT), obtained using the spot disc test and a gravimetric method. The permeation parameters, calculated from the sorption data, were used to determine an optimum filler content for maximum protection against SM. To investigate the effect of carbon loading on the permeation properties of IIR, the permeation of SM and OA in carbon-loaded black membranes was compared with nonblack membranes and interpreted in terms of the dispersion of carbon in the membranes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 503–511, 1998

The effect of carbon aspect ratio on the friction and wear of PTFE

Three carbons of differing aspect ratios were incorporated into a matrix of PTFE. Experiments were conducted to investigate the behaviour of the differing particle shapes on the friction and wear characteristics of the composites. The wear tests were conducted at a sliding velocity of 300 m min −1 and at a load of 4 kgf which corresponded to a nominal contact pressure of 2.5 × 10 5 Pa. The counterface was mild steel with a mean roughness of 0.02 μm c.l.a. and the bulk temperature of the counterface was maintained at 21 °C. The tests were conducted in air. In all cases incorporation of the graphite filler reduced the wear rate of the composite, the polar and nuclear forms being more beneficial at the same wt.% levels than the oleophilic form of graphite. It was found that an optimum filler content existed for all the carbon systems studied, above and below which the wear rate of the specimens increased.

A method for the calculation of optimum filler content in amorphous and semicrystalline polymers

A method for the calculation of optimum filler content in amorphous and semicrystalline polymers