Inclusion Of Filler Research Articles

Characterisation of Bionate polycarbonate polyurethanes for orthopaedic applications

Two polycarbonate polyurethanes, Bionate 75D and Bionate 80A, have been characterized for application in biomimetic joint replacement systems. Procedures involved measurement of the effects of compounding and moulding on molecular weight, melt rheometry, and mechanical testing using conditioned and aged specimens. The effects of compounding with hydroxyapatite and carbon fibres were also evaluated. With Bionate 75D moulding reduces the molecular weight by 30%. Passing the material through a twin screw extruder without filler has similar molecular weight reduction effects to injection moulding. Inclusion of carbon fibre has little additional effect on molecular weight, although moulding of the fibre filled compound causes some further degradation, and Mw is almost halved compared with the original value. Inclusion of hydroxyapatite reduces Mw in a moulded component to less than a quarter of the original value and some form of chemical interaction between the polymer and filler is presumed. The apparent melt viscosity of the Bionate 75D was reduced by the addition of both carbon fibres and hydroxyapatite and this is thought to arise from reduction in molecular weight during the compounding process and the development of shear planes at the polymer-filler interface. The polymer glass transition temperatures are shifted to slightly higher values by the inclusion of filler. The tensile test results show the reinforcing effect of the carbon fibres, but poor wetting and pull out of the fibres was evident. Water absorption results suggest that the materials stabilise after 2 weeks, but the tensile results indicate that property change occurred between 1 month and 5 months of exposure. However the shape of the stress-strain curves is not altered, but with extended water exposure is translated to lower stress levels.

Three‐body abrasive wear behavior of E‐glass fabric reinforced/graphite‐filled epoxy composites

AbstractThe present article summarizes an experimental study on three‐body abrasive wear behavior of glass fabric reinforced/graphite particulate‐filled epoxy composites. The wear behavior was assessed by rubber wheel abrasion tests (RWAT). The angular silica sand particle sizes in the range 200–250 μm were used as dry and loose abrasives. The tests were carried out for 270, 540, 810, and 1,080 m abrading distances at 22 and 32 N loads. The worn surfaces were examined using scanning electron microscopy (SEM). The results showed varied responses under different abrading distance due to the addition of glass fabric/graphite filler into neat epoxy. It was observed that the glass fabric reinforcement to epoxy matrix (G‐E) is not beneficial to abrasive wear resistance. Further, inclusion of graphite filler to glass fabric reinforced epoxy composite performed poorly resulting in significant deterioration in wear performance while the neat epoxy showed better wear performance. Selected mechanical properties such as hardness, ultimate tensile strength, and elongation at fracture were analyzed for investigating wear property correlations. The worn surface features were studied using SEM to give insight into the wear mechanisms. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Structural and transport properties of porous PVdF-HFP electrolyte membranes modified with an inorganic filler

Novel porous poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) copolymer membranes were prepared with zinc chloride as an additive and silica as a ceramic filler. Porosity of the membranes was determined by Scanning Electron Microscopy (SEM). Inclusion of ceramic filler decreases the crystalline character of a polymer which facilitates the movement of ions leading to an increase in the conductivity. The infra-red spectroscopic and EDX measurements revealed the presence of acid moieties in the composite membranes. The thermal stability of these blend membranes lies above 400°C, which is sufficiently high for use in DMFC. The membranes prepared for this study exhibited the ionic conductivity in the range of 10−3 to 10−2 S/cm and the methanol permeabilities ranged between 10−9 and 10−7cm2/s.

Influence of SiC Filler on Mechanical and Tribological Behavior of Glass Fabric Reinforced Epoxy Composite Systems

The performance of filled fiber reinforced polymer composites is generally determined on the basis of the interface attraction of filler, fiber, and polymer. In the present investigation, the effects of SiC particles as fillers in glass—epoxy (G—E) composite systems on the mechanical and tribological properties have been discussed. The composites employed in the present study have been fabricated using hand lay-up technique. The mechanical properties such as tensile strength, tensile modulus, elongation at break, flexural strength, and hardness have been investigated in accordance with ASTM standards. From the experimental investigation, it was found that the mechanical properties of the G—E composite increased with the inclusion of SiC filler. The dry slide wear test results of SiC-G—E composite show lower slide wear losses irrespective of the load/sliding velocity when compared to G—E composite. Some of these observations are supplemented by scanning electron microscopic (SEM) observations. Further, wear of the matrix, breakage of reinforcing fibers, matrix debris formation, and interface separation were observed. SEM microphotographs of the tensile fractured samples revealed the typical aspects of the fractured surfaces. The failure modes of the tensile fractured surfaces were evaluated and showed good agreement with the literature.

Hydrocolloid Carriers with Filler Inclusionfor Diltiazem Hydrochloride Release

Hydrocolloid beads based on agarose, alginate (both 3%, w/w), or gellan (2%, w/w) were produced to study their potential as drug carriers. The beads included various fillers: talc, kaolin, calcium carbonate, potato, or corn starch (10%, w/w). After gelation, the carriers were subjected to either freeze- or vacuum-drying. The dried carriers were spheroids. The diameters of freeze- and vacuum-dried carriers ranged from 2.4 to 4.1 mm and 1.5 to 2.8 mm, respectively. The porosity values of the freeze-dried carriers were significantly higher than those of their vacuum-dried counterparts. Scanning electron microscopy (SEM) revealed that all dried carriers included internal voids that were partially occupied by the filler particles. Upon their introduction into simulated gastric fluid (3 h), followed by 6 h in intestinal fluid, all carriers were stable and underwent swelling. Release profiles of diltiazem hydrochloride from different carriers were obtained during immersion in dissolution medium. Filler inclusion (but not the type of filler) contributed to the stability of the carriers and prolonged the time of drug release (6.5-8.5 h) relative to the faster drug release from carriers that contained no filler (3.5 h). In summary, alginate, agar, and gellan beads with filler inclusion may be useful for slow drug release.

Role of cement content in specifications for concrete durability: aggregate type influences

In this paper, the second of the series, examining the role of cement content in specifying concrete durability, the influences of aggregate characteristics are considered. As for the first paper, the reported work was carried out within a framework of mix adjustments, required to produce practical concretes, that is, with the inclusion of filler and superplasticising admixture. A total of five UK normalweight aggregates and a lightweight aggregate were examined. It is shown that, for a given w/c ratio and aggregate type, reduction in cement and water contents (and the associated mix adjustments) did not adversely affect concrete properties (fresh, bulk engineering, permeation and durability). Indeed, many aspects of concrete performance were enhanced, with the improvements with cement reduction generally being greatest for aggregates having low absorption. Furthermore, the influence of cement content at a given w/c ratio on durability was found to be less significant than that of a change in aggregate type for the range of UK materials tested. The implications of the study for concrete construction practice are discussed.

The use of Agar as a novel filler for monolithic matrices produced using hot melt extrusion

The use of filler materials in an extended release monolithic polymer matrix can lead to a vastly altered release profile for the active pharmaceutical ingredient. A range of excipients for use in monolithic matrices have been discussed in the literature. The body of work described in this research paper outlines the use of agar as a novel filler material in a hot melt extruded polymer matrix. Several batches of matrix material were prepared with Diclofenac sodium used as the active pharmaceutical ingredient (API). Agar and microcrystalline cellulose were used as the filler materials in varying ratios, to examine the effect of % filler content as well as filler type on the properties of the hot melt extruded matrix. The resultant extrudates were characterised using steady state parallel plate rheometry, differential scanning calorimetry (DSC) and dissolution testing. The rheometry analysis concluded that the fillers used resulted in an increase in the matrix viscosity. The DSC scans obtained showed negligible effects on the melting behavior of the matrix as a result of the filler inclusion. Dissolution analysis showed that the presence of the fillers resulted in a slower release rate of API than for the matrix alone. The results detailed within this paper indicate that agar is a viable filler for extended release hot melt produced dosage forms.

Mechanism of strain-induced crystallization in filled and unfilled natural rubber vulcanizates

Structure evolution during deformation of unfilled natural rubber (NR) vulcanizate and filled ones with carbon black or calcium carbonate was investigated by the synchrotron x-ray diffraction. The crystallization onset strain, α0, was found to decrease by the inclusion of the filler. However, corrected α0 values into the effective strain ratio of deformable rubber portion were almost constant between filled and unfilled samples. Accordingly, our model of strain-induced crystallization of unfilled NR vulcanizates, assuming that melting temperature is independent of network-chain length (n), was applied to the filled samples. The discrepancy between classical theories and experimental results was thought to come from the distribution of n. By the inclusion of filler, the lateral crystallite size was decreased but the orientational fluctuation increased. The lattice of the strain-induced crystallites changed almost linearly with the nominal stress. In addition, the degree of lattice deformation decreased with the filler content, especially in the carbon black-filled system. All these experimental results are consistent with the proposed model.

04/00176 Effect of filler-fiber interactions on compressive strength of fly ash and short-fiber epoxy composites: Kulkarni, S. M. Journal of Applied Polymer Science, 2003, 87, (5), 836–841

The influence of graphite filler additions on two-body abrasive wear behaviour of compression moulded carbon–epoxy (C–E) composites have been evaluated using reciprocating wear unit and pin-on-disc wear unit under single pass and multi-pass conditions respectively. The carbon fabric used in the present study is a plain one; each warp fiber pass alternately under and over each weft fiber. The fabric is symmetrical, with good stability and reasonable porosity. Abrasive wear studies were carried out under different loads/abrading distance using different grades of SiC abrasive paper (150 and 320 grit size). Graphite filler in C–E reduced the specific wear rate. Further, the wear volume loss drops significantly with increase in graphite content. Comparative wear performance of all the composites showed higher specific wear rate in two-body wear (single-pass conditions) compared to multi-pass conditions. Further, the tribo-performance of C–E indicated that the graphite filler inclusion resulted in enhancement of wear behaviour significantly. Wear mechanisms were suggested and strongly supported by worn surface morphology using scanning electron microscopy.

Structure of dried cellular alginate matrix containing fillers provides extra protection for microorganisms against UVC radiation.

Soil microorganisms in general and biocontrol agents in particular are very sensitive to UV light. The packaging of biocontrol microorganisms into cellular solids has been developed as a means of reducing loss caused by exposure to environmental UV radiation. The bacterial and fungal biocontrol agents Pantoea agglomerans and Trichoderma harzianum were immobilized in freeze-dried alginate beads containing fillers and subjected to 254 nm UV radiation (UVC). Immobilization of cells in freeze-dried alginate-glycerol beads resulted in greater survival after UV irradiation than for a free cell suspension. Adding chitin, bentonite or kaolin as fillers to the alginate-glycerol formulation significantly increased bacterial survival. Immobilization in alginate-glycerol-kaolin beads resulted in the highest levels of survival. The transmissive properties of the dried hydrocolloid cellular solid had a major influence on the amount of protection by the cell carrier. Dried alginate matrix (control) transmitted an average of 7.2% of the radiation. Filler incorporation into the matrix significantly reduced UV transmission: Alginate with kaolin, bentonite and chitin transmitted an average of 0.15, 0.38 and 3.4% of the radiation, respectively. In addition, the filler inclusion had a considerable effect on the bead's average wall thickness, resulting in a approximately 1.5- to threefold increase relative to beads based solely on alginate. These results suggest that the degree of protection of entrapped microorganisms against UVC radiation is determined by the UV-transmission properties of the dried matrix and the cellular solid's structure. It is concluded that for maximum protection against UV-radiation-induced cell loss, biocontrol microorganisms should be immobilized in alginate-glycerol beads containing kaolin.

Irregular textural features of dried alginate–filler beads

Freeze-dried hydrocolloid beads can be used as carriers for many food, non-food and biotechnological operations. Information on their shape and surface properties, how different features are produced on their outer surface as a result of technological procedures, and the influence of fillers and other ingredients on external and internal shape and texture have never been investigated in detail. These parameters are very important since the surface of the bead is the first part to come into contact with its fluid, solid or gaseous environment and together with its internal structure, will influence, if not determine, its suitability to a predetermined task. In our study, projections formed on the surface of the bead during freezing. Smaller-sized fillers (such as kaolin) gave a smoother surface; a rougher surface was achieved with a bigger-diameter filler, such as bentonite. The presence of filler and/or glycerol in the bead increased the number of mid-area ‘craters’ and reduced the number of the smaller ‘craters’ formed on the bead's dried surface. Moreover, the inclusion of glycerol had a large influence on the distribution of pores within the beads. Filler inclusion in the dried product reduced its collapse and roundness distortion during the drying process. In conclusion, the components and the method by which the dried bead was formed completely determined its weight, volume, shape and surface features. Taking these parameters into consideration provides the researcher with a useful tool for creating tailor-made dried beads for a predetermined operation, thereby increasing the probability of success. This was proven by the improved antifungal activity of entrapped Pantoae agglomerans (biocontrol agent) within alginate–glycerol–chitin beads.

Estimation of the filler content required to minimise voids ratio in concrete

This paper reports the findings of a study of the filler content required in concrete to produce a minimum voids ratio (or maximum packing density) according to particle packing models. The calculation of theoretical voids ratio shows that the filler content required to minimise voids ratio depends on the original concrete mix proportions as well as the fineness of the fillers. Concrete mixes with a high original cement content required the inclusion of finer filler to minimise the voids ratio and coarser, low-cost fillers were suitable for mixes with lower cement contents. The study shows the importance of both filler fineness and mix proportions on minimising voids ratio at a cement-sized grain level. Agglomeration of the fine particles and an effective utilisation of filler are also considered and two criteria are proposed to determine the filler content required to minimise the voids ratio in concrete.

The Effect of Viscosity and Filler on Electrospun Fiber Morphology

Electrospinning is a simple technique to create nanometer‐scale polymer fibers by application of a large static voltage to a viscous polymer solution, or spin‐dope. At polymer concentrations higher than the critical concentration, above which polymer entanglement can occur, it was found polymer fibers could be electrospun, provided the spin‐dope solution was sufficiently viscous. The requisite viscosity could be obtained by increased polymer concentration or by inclusion of insoluble filler, titanium dioxide in this case. Electrospun fibers of polyethylene oxide (PEO) were successfully fabricated that consisted of as little as 25 wt.% polymer. The remainder of the fiber weight consisted of titanium dioxide (TiO2) particles that could not be electrospun alone. We demonstrate that it is possible to create a high‐surface area structure of a material that cannot be electrospun by the inclusion of a small amount of polymer.

Metabolizable energy from dietary carbohydrates in turbot, Scophthalmus maximus (L.)

Abstract. In a feeding experiment, the metabolizability of dietary carbohydrates in diets for turbot, Scophthalmus maximus (L.), was estimated and expressed as percentage of the metabolizability of dietary lipids. Four isoenergetic and isonitrogenous dietary treatments were applied with varying percentages of non-protein energy presented as starch. In order to obtain results allowing quantitative interpretation, an experimental design was used in which effects are reflected in varying body fat depositions only. Two methods were used simultaneously to overcome practical problems associated with differences in energy density between carbohydrates and lipids. The conventional method was based on equal feeding rates combined with the inclusion of inert filler in the diets, whereas the alternative method applied different dietary nutrient percentages in combination with different feeding rates. Although similar results were obtained, the alternative method was more convenient to use than the conventional method. Because of the experimental strategy applied, no significant effects on growth and protein utilization were obtained, but lipid deposition rates were significantly reduced at increased percentages of non-protein energy presented as starch. The metabolizable fraction of the gross dietary carbohydrate energy was estimated as 67% of that of dietary lipids. This reduction does not indicate that turbot have any systematic deficiency in metabolizing dietary carbohydrates.

Some properties of dental ceramics

The rather exacting aesthetic requirements of dental restorations has largely dictated the composition of dental ceramic materials. The so-called dental porcelains have evolved from the traditional whiteware formula of feldspar, clay and quartz. One of the first variables which might be considered is that of chemical composition. It is, however, generally accepted that for ceramic materials small variations in composition are not critical. Since the early work of Watts in 1918, little interest has been expressed in the chemical composition of dental porcelain. The composition of traditional dental porcelains has evolved over a period of many years by practical trial and error, as discussed by Jones (1971). The development of dental porcelains advanced to the point where any major improvements in physical properties could only be achieved by major changes in composition and technique as advocated by McLean & Hughes (1965). The resulting alumina/glass composites which have been developed use a technique which involves the build up of an inner core which contains a high proportion of crystalline alumina (45-50 %) embedded in a glass matrix surrounded by a transparent outer veneer. This work compares the effect of such inter-related variables as composition, inclusion of filler, viscosity, texture, hardness, and strength of the fired product.