Melt blowing is a melt extrusion process that allows us to start with a material in resin form and obtain a final web product in one step. The fine fibers that are characteristic of this process are in the 0.1 to 15 micron range in diameter. This process was first described in the literature by Wente of the Naval Research Laboratory in 1956 [1] and the purpose of the work was to investigate the feasibility of making ultrafine fibers for evaluation as a filtermedia. Since then melt blowing has been one of the fastest growing technologies in the non-wovens area as evidenced by the numerous articles in the literature and the number of issued patents. For example, an article by McCulloch and Graham [2] illustrated the diverse use of melt blown webs which are also referred to as Blown Micro Fiber(BMF) webs.

Sandwich composites find increasing use as flexural load bearing lightweight sub-elements in air / space vehicles, rail / ground transportation, marine and sporting goods. The core materials in these applications is usually balsa, foam or honeycombs, while laminated carbon or glass are used as facesheets. A limitation of traditional sandwich configurations is that the space in the core becomes inaccessible once the facesheets are bonded in place. Significant multi-functional benefits can be obtained by making either the facesheets or the core, space accessible. Multi-functionality is generally referred to as value added to the structure that enhances functions beyond traditional load bearing. Such functions may include sound / vibration damping, ability to route wires or embed sensors. The present work considers traditional core materials of nomex and aluminum honeycombs that possess functional space accessible facesheets, and their low velocity impact (LVI) response.

Demand for special fibres produced from natural polymers such as alginate, chitin or chitosan, starch, keratin or biosynthesised cellulose is a function of their unique properties and growing areas of application. Two types of fibres made from chitosan and alginate are discussed in this paper. The wet-spinning method was applied for their manufacture using modified spinning solutions of the polymers. The properties and some of the application areas of chitosan and alginate fibres are discussed.

Recent progress in the crystallization of amorphous mullite (3Al2O3•2SiO2) and yttrium aluminate (Y3Al5O12, 5Al2O3•3Y2O3 or “YAG”) beads and fibers is reviewed. Studies were made by differential thermal analyses, (DTA, DSC), synchrotron X-ray diffraction and Rietveld profile fitting, HREM, EDS and SEM. Crystallization kinetics, activation energies and microstructures were determined, leading to temperature-time-transformation (T-T-T) curves. The crystallization of mullite from the solid state proceeds by formation of large-grained, pseudo-tetragonal mullite of composition 70 mol% Al2O3, which is highly strained and which contains <10 nm silica-containing inclusions. During further heat treatments, the inclusions react with the first-formed mullite yielding single phase, orthorhombic mullite of 60 mol% Al2O3. Recrystallization also occurs on further heating with a significant reduction of grain size, in a manner similar to recrystallization in brass. These observations (using more modern and sensitive characterization techniques) suggest the presence of a peritectic-like, syntectic or syntectoidal invariant reaction in the Al2O3-SiO2 phase diagram. Further work needs to be done to ascertain whether the reaction is an equilibrium or non-equilibrium phenomenon.

The predominate substrate for multilayer printed wiring boards is laminate constructed from epoxy resin reinforced with fiber glass fabrics. This combination of materials dominates the segment of the electronics market where dimensional stability of the substrate is critical. The rapid development of high speed digital and analog electronic systems has challenged the predominance of fiber glass as the reinforcement of choice. As systems move to the GHz frequency range, there is a need for lower dielectric constant of the substrate to insure integrity and speed of signals. A lower dissipation factor of the substrate is desired for the wireless communication applications of printed wiring boards. A review is presented of materials competing as substrates for the high speed application of the printed wiring board market.

Motivated by the high level of strength and toughness of spider silk and its multifunctional nature, this paper reports on the engineering properties of individual fibers from Nephila Clavipes spider drag line under uniaxial tension, transverse compression and torsional deformation. The tensile properties were compared to the Argiope Aurentia spider silk and show different ultimate strength but similar traits of the unusual combination of strength and toughness characterized by a sigmoidal stress-strain curve. A high level of torsional stability is demonstrated. comparing favorably to other aramid fibers (including Kevlar fibers).

Two polyols were prepared from soybean oil, one by epoxidation route and the other via hydroformylation. The polyol obtained by epoxidation has secondary groups and has a gel time of more than one hour when reacted with crude MDI to produce polyurethanes. Hydroformylated polyol has a gel time with MDI of several minutes and is more suitable for reinforced reaction injection molding (RRIM). The first group of polyurethanes had a glass transition close to 80 °C while the hydroformylated gave about 30 degrees lower Tg and comparable strength but higher elongation. Adding glycerin as the crosslinker could increase both Tg and strength. Two series of laminates were prepared using several types of glass fabric, carbon fiber, polyester, cotton and jute fabrics r as reinforcements. Hydroformylated polyol based polyurethane composites were softer, with lower Tg, modulus and strength. Composites with organic fibers were lighter and more flexible than the glass reinforced samples. For comparison glass reinforced epoxy and polyester were prepared and tested. Organic fibers gave lower stiffness and strength than the corresponding glass or carbon fiber. Although the neat polyester and epoxy resins had somewhat higher strengths than the polyurethanes from soybean oil, mainly due to the higher crosslinking density, the composites from the soy oil-based resin displayed comparable or better properties. Glass transition and mechanical properties of the soy-based polyurethanes was varied from about 70 °C to 140 °C with added crosslinkers. Processing time of the soy-polyurethanes resins was shorter than that of the other two resins.

This paper analyzes the value-in-use of advanced fibers, especially of those, which are used to reinforce polymer matrix composites. Of particular interest in this regard are some recent fibers, such as (1) pure silica fibers derived from water glass, (2) oxynitride glass fibers, having the same high elastic modulus as SM carbon fibers, and (3) Kenaf, as well as other natural plant fibers, which are beginning to find commercial use in selected automotive composites.

Three types of debris particles, denoted by L2, H2 and K3 respectively, originated from the abrasion of silica-filled, vulcanized rubber under different test conditions (severity) were analyzed and compared. The structural fractal dimension, DFS, of the particle perimeter was chosen as a morphological descriptor (but not necessarily as an intrinsic property of the fractured material !). Said dimension was estimated by processing light microscopy images. A value of the morphological threshold, TST, which separates the textural from the structural domain in the RICHARDSON plot was determined in order to maximize discrimination between the three particle types and rank them by increasing values of DFS. Particles from the highest severity test (K3) exhibited the highest value of DFS. X ray photoelectron spectroscopy (XPS) provided elemental composition, core level binding energies and the speciation of C, N, O, Si and S. As a result, L2 debris was found to originate from two processes: fracture of rubber and segregation of extender oil. Evidence has come both from morphology and XPS. Particles of H2 and K3 were ascribed to fracture alone. Comparison between K3 and the reference material, rasped rubber (RAS), shows the following: a) increase of the [S]/[C] surface atomic concentration ratio from RAS to K3; b) existence of multiple bonding states of S in K3 with energy peaking at 162.9 ± 0.3 eV ([-S-S-]n); c) weak contribution of R-S-O-R oxidized S species in K3 at 165 eV, not seen in RAS; d) no evidence of either SO3 or SO4 groups in any material. Although preliminary, these results prove the ability of morphological analysis and XPS to characterize the surface properties of debris particles non destructively.

Unlike conventional spin methods, electrospinning is capable of yielding fibers with sub-micron range diameters and high specific surface areas. The use of such electrospun materials in applications, whose functionality depends on the area available, such as separation processes, will be useful. In this study a Bisphenol-A polycarbonate was dissolved in two solvents: Chloroform and a 1:1 mixture of Tetrahydrofuran (THF) and Dimethylformamide (DMF) and resulting polycarbonate solutions were then electrospun to produce polycarbonate fiber-mats. The morphological features of the electrospun polycarbonate fibers have been studied as a function of the solvent used and also as a function of the processing voltage. The studies were conducted using the SEM, TEM and Scion image analysis program. The results indicate bold differences in the fiber morphology and bead density trends with the solvent used. Electrospun polycarbonate fibers exhibit a “Raisin like” puckered structure. Such a structure will enhance the functional efficiency of an electrospun material when used in an area-based application. In addition, studies on crazing of bulk polycarbonate and the surface features of electrospun polycarbonate fibers have been conducted. Results indicate a relation between crazing and the topological features of electrospun polycarbonates.

Carbonaceous mesophases are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a range of fiber textures whose origins are not well understood. Planar polar (PP) and planar radial (PR) textures are two ubiquitous ones. A model that describes the formation process of the PP texture based on the Landau-de Gennes mesoscopic theory for discotic liquid crystals, including defect nucleation, defect migration, and overall texture geometry, is presented, solved, and validated. The computed PP and PR textures phase diagram, given in terms of temperature and fiber radius, is presented to establish the processing conditions and geometric factors that lead to the selection of these textures. The influence of elastic anisotropy to the textures formation and structure is also characterized.

Cellulosics have a very balanced set of general features, with its unique specific control of moisture resulting in widely accepted physiological benefits and wearing comfort. This gives interesting future prospects for the man-made cellulosics Viscose, Modal and Lyocell by Lenzing AG. The fibres produced cover a wide range of nowadays possibilities from the viscose and Lyocell process, covering textile, non woven, technical or medical application. For a brief introduction into the different types some of the main properties are given in table 1 compared with other fibres.

Molten Al-Mg alloys has been infiltrated into SiC to produce Al matrix composites at 900oC for different infiltration times under N2. The wettability of the ceramic reinforcement by the Al-Mg alloy is crucial in determining whether Al can be infiltrated into ceramic preform. Sessile drop results showed that Al alloys with Mg contents greater than 8wt-% had a contact angle lower than 90o, after 5 minutes contact time, this was associated with the infiltration of Al-Mg alloys into SiC preform occurred after 30 minutes. Sessile drop experiments also show that SiC is similarly wetted by Al-Mg alloys under N2. It is concluded that the infiltration process does not involve the intermediate nitride phase suggested by other authors. These materials were also charaterised both mechanical properties and microstructure.

Turkey feather fibers were characterized and then converted into products such as yarn and nonwoven fabrics for a study into the feasibility of their use as textile products. Yarn containing blends of nylon and up to thirty percent turkey feather fibers were spun by combining novel techniques with commercial yarn spinning machinery. These yarns were tested for determination of their mechanical properties. As the percentage of turkey feather fibers increased, the tenacity and elongation of the yarns decreased while the modulus increased. These yarns were knitted into fabrics to determine their insulating properties. As the percentage of turkey feather fibers increased the insulating capabilities of the fabrics also increased. Recent research has focused on producing nonwoven fabrics containing turkey feather fibers utilizing various production methods for use as erosion control fabrics.

The fabricating conditions for the in-situ Al-Si base composite by the centrifugal casting method (CCM) have been examined. The crystallized Si particles with a lower density distribute in a gradient fashion as densely on the inner and thinly on the outer side of the wall of the cylindrical CCM-composite. Synthetically, the 25 mol% Si composite is recommended for the application like the engine liner.

The Northeast Region of Brazil has a land area of over I.5 million km2 and extends over tropical and equatorial latitudes from 18' S in the State of Bahia to 1' S in the State of Maranhão. Although representing only about 18% of the national territory, it is the home of approximately 35% of Brazil's 160 millions inhabitants (IBGE, 2000). The Northeastern region of Brazil, in the States of Bahia, Paraiba and Rio Grande do Norte are responsible for 100% of sisal production. Precipitation is the key environmental factor of ecological significance for the region and can be characterized by three major zones trending east to west. First is a narrow humid coastal strip in the cast (known as Zone of Mata) which receives an average of 1,250 mm to over 2,000 mm of rainfall per annum. Behind this humid zone there is a middle one with moisture deficiency (subject to periodic droughts) which accounts for the largest portion of the Northeast. Most of this zone receives less than 1,000 mm of annual rainfall, with an extreme low of less than 300 mm in some areas. The third zone is one of high rainfall, over 2,000 mm per year, in western Maranhão. Reflecting this wide diversity of moisture conditions are natural vegetation patterns ranging from tropical rainforest (“Atlantic Rain Forest”) to semi-arid thorn scrub (“Caatinga”). This system has been under severe pressure due to the lack of economical alternatives to support the population living in those areas.

When natural fibres are applied as reinforcement in polymer composites the moisture sensitivity, causing fibre swell and ultimately rotting through fungi attack, can be a very serious problem. A number of methods have been developed dealing with this problem that change the chemical and / or physical composition of the fibre, resulting in reduced moisture sensitivity. To this category belong acetylation and hydrothermal treatment. For acetylation, acetic anhydride is used as a chemical that reacts with reactive OH-groups of the lignocellulose material, increasing hydrophobicity. In hydrothermal treatment no chemicals are used, only water and energy.

The main focus of this paper is on hydrothermal treatment, the Duralin® process in particular, of bast fibres such as flax, jute and hemp. Acetylation is reviewed briefly. A survey is given of the structure and composition of bast fibres and the moisture adsorption and desorption mechanisms in these fibres.

The Duralin® process involves three steps, hydrothermolysis, drying and curing. The raw material for the Duralin® process applied to flax is green rippled flax straw. This eliminates the need for the traditional dew-retting, a risky process where the freshly harvested flax stems lay on the field for about four weeks. The Duralin® process reduces moisture absorption and biological degradation, the fibre yield is higher than after dew-retting and the shives can be used as a filler material in polymers and for making a water proof particle board. The main causes for reduced water uptake after Duralin treatment will be reviewed.

Duralin® fibres have equal or higher tensile strength and higher flexural modulus than fibres extracted from dew-retted flax. Compounds reinforced with these fibres have apart from decreased moisture sensitivity a better mechanical performance. Both the amount and the release rate of decomposition products resulting from compounding with polypropylene are significantly less for Duralin® fibres than for dew-retted or green fibres. Duralin® fibres are on a weight basis competitive with glass fibres.

The focused ultrasonic beam technique has been employed for imaging of bulk microstructure of fiber-reinforced composites, for measuring local elastic properties and mapping their distribution over the composite body. Ultrashort probe pulses (operation frequency of 50 MHz) provide resolution of 100 μm. The technique has been employed for nondestructive layer-by-layer imaging of microstructure of CFR laminate composites. Series of acoustic images in planes parallel to the specimen face (C-scans) or perpendicular to it (B-scans) enable to reconstruct of bulk microstructure of compound unidirectional CFR laminates. Different types microdefects, including failures in interply adhesion, buckling of single prepreg plies, internal defoliations and disbonds, have been observed. The method has been applied to measure local values of elastic wave velocities in laminates within area of 100 - 150 μm diameter.

Quality of acoustic images depends on kind and density of fiber packing and on depth of position of the imaging plane. Experience shows that specimens 2-10 mm thick are appropriate for visualization of their bulk microstructure and measuring local values of sonic velocities. The technique is promising for NDE of different composites, not only for carbon-based ones.

Novel hybrid aerogels consisting of the bioderived polymers chitosan, pectic acid or alginic acid and silica have been synthesized as clear monoliths from clear gels by supercritical fluid extraction. These renewable resource polymers, which are soluble and typically unassociated in aqueous systems, are separately arranged in aerogel scaffolding. This makes them exposed and available for reactions that in some cases would not be possible in aqueous systems. Thus, it is possible to react the amine groups of chitosan, a polymer derived from chitin, with isocyanate-terminated prepolymers to form urea linkages and to form new linked chitosan materials. Following the reactions, the scaffold can be dissolved and the new material isolated. Variations lead to hydrophobic or hydrophilic materials. The reactions of aerogel scaffolded bioderived polymers to form urethane-or amide-group linked materials also will be presented and the properties of newly formed materials will be described. Further reactions enabled by the approach, including ones leading to radiation curable polymeric systems will be presented.

General Motors Research and Development and Basell Polyolefins have jointly developed a family of polyolefin-based nanocomposites for use in the injection molding of body-side claddings. Basell Polyolefins commercialized one of these materials as Hifax DX277 in September of 2000, and General Motors has exclusive use of this material. Confidence in the ability of DX277 to perform as intended is being reinforced by molding trials at various Tier 1 locations. In addition to mass savings, the nanocomposite material is showing a much wider processing window than conventional talc-filled TPO’s – allowing Tier 1 molders the opportunity to process away problems rather than initiating a tooling change. This paper will describe the processing advantages associated with the injection molding of a polyolefin-based nanocomposite over a conventional talc-filled TPO.