Showing papers on "Thermoplastic published in 1998"

Improvement of Starch Film Performances Using Cellulose Microfibrils

Abstract: Starch is a natural, renewable, biodegradable polysaccharide produced by many plants as a storage polymer. It usually has two major components and appears as a mixture of two glucosidic macromolecules very different in structure and properties: largely linear amylose of molecular weight between one thousand and one million, consisting of R-(1f4)-linked D-glucose, and amylopectin, having the same backbone as amylose but with a myriad of R-(1f6)-linked branch points. The most commercially important starch comes from corn, wheat, rice, potatoes, tapioca, and peas. Native starch occurs in the form of discrete and partially crystalline microscopic granules that are held together by an extended micellar network of associated molecules. Starch has received considerable attention during the past two decades as a biodegradable thermoplastic polymer and as a biodegradable particulate filler. Indeed, products from agricultural sources, such as starch, offer an attractive and cheap alternative in developing degradable materials. Starch is not truly thermoplastic as most synthetic polymers. However, it can be melted and made to flow at high temperatures under pressure and shear. If the mechanical shear becomes too high, then starch will degrade to form products with low molecular weight. Addition of water or other plasticizers enables starch to flow under milder conditions and reduces degradation considerably. However, the thermomechanical stability is strongly reduced by the addition of plasticizers. By itself, starch is a poor choice as a replacement for any plastic. It is mostly water soluble, difficult to process, and brittle. In principle, some of the properties of starch can be significantly improved by blending it with synthetic polymers. Physical incorporation of granular starch or starch derivatives as a functional additive and filler into synthetic polymers during processing has been largely used since the first announcements of using starch in combination with synthetic polymer either as starch gel blends with ethylene acrylic acid copolymers by Westhoff et al.1 or as particulate starch dispersions in polyolefins by Griffin.2 More recently, increasing interest in developing new and inexpensive biodegradable materials has led to a substantive amount of research in polymer blends containing starch.3-8 However, the mechanical properties of films are generally reduced by incorporation of starch. Like most of the polymers, starch is immiscible with most of the synthetic polymers at the molecular level. Grafting of synthetic polymers on starch is known to improve some of its properties, but although the grafting of starch with synthetic polymers has been known for 30 years, very few processes have led to full-scale commercialization. Another way of using starch in the material field is the processing of starch microcrystals, which can be obtained as an aqueous suspension. This filler brings a great reinforcing effect to a polymeric matrix, as shown previously.9 In this work, an attempt was made to improve the thermomechanical properties and to decrease the water sensitivity of starch-based systems, preserving the biodegradability of the material. An alternative way to palliate these restrictions is the use of cellulose as a natural and biodegradable filler. Natural cellulose fibers are gaining attention as a reinforcing phase in thermoplastic matrixes. Its low density, a highly reduced wear of the processing machinery, and a relatively reactive surface may be mentioned as attractive properties, together with their abundance and low price. In addition, the recycling by combustion of cellulose composites is easier in comparison with inorganic filler systems. Nevertheless, such fibers are used only to a limited extent in industrial practice, which may be explained by difficulties in achieving acceptable dispersion levels. Cellulose fibers are constituted of long threadlike bundles, called microfibrils, of cellulose molecules stabilized laterally by hydrogen bonds between hydroxyl groups of adjacent molecules. Cellulose microfibrils can also be found as intertwined microfibrils in parenchyma cell wall, in particular from potato pulp. They can be extracted from this biomass by a chemical treatment, leading to purified cellulose, followed by a mechanical treatment in order to obtain a homogeneous suspension due to the individualization of the microfibrils. This suspension has been used afterward to process composite materials with a high level of dispersion, by mixing with an aqueous suspension of gelatinized starch as matrix. Potato pulp was purified according to the treatment displayed in Figure 1. After the removal of starch granules, the remaining pulp is traditionally pressed and dried to be marketed as cattle feed. This byproduct was provided, as pellets, by Avebe Co. (Haussimont, France). The pellets were hydrated into water and ground in a Waring blender apparatus for 10 min. The potato slurry was then poured on a 0.25 mm sieve and washed with water, to remove most of the remaining starch granules. The alkali extraction with sodium hydroxide (NaOH) solution allowed the solubilization of pectins, residual starch, and hemicelluloses, which were then removed by filtration and finally rinsed with distilled water. The resulting insoluble residue was bleached with a sodium chlorite (NaClO2) solution, as already described for sugar beet.10,11 At this stage, the different cell walls are individualized, as shown in Figure 2A, but the microfibrils are still associated within the cell wall. To extract and individualize the microfibrils from the cell walls, a mechanical treatment is required. The insoluble bleached cellulosic pulp was suspended in distilled water (2 wt %) and disintegrated for 15 min in a Waring blender. The suspension was then homogenized by 15 passes through a Manton-Gaulin laboratory homogenizer, described elsewhere by Dufresne et * To whom correspondence should be addressed (e-mail: dufresne@cermav.cnrs.fr). 2693 Macromolecules 1998, 31, 2693-2696

Thermoplastic toughening of epoxy resins: a critical review

Abstract: Thermoplastic toughening of epoxy resins has been actively studied since the early 1980s with considerable progress in property improvement and understanding having been made since then. The main advantage in using thermoplastics to toughen epoxy resins is that their incorporation need not result in significant decreases in desirable properties such as modulus and yield strengths as is generally the case when rubbers are used as toughening agents. However, the predominant criteria for achieving optimum toughness enhancement in the thermoplastic toughening of epoxy resins are still not all that clear from the literature. This review has focused upon the importance of the thermoplastic endgroups, the material's morphology, the ductility of the matrix and the chemical structure of the thermoplastic, it summarizes what the authors believe are the important requirements for good thermoplastic toughening. © 1998 John Wiley & Sons, Ltd.

Balloons made from liquid crystal polymer blends

Abstract: Balloons for use on medical devices such as catheter ballons are formed from polymer blend products which include a liquid crystal polymer (LCP), a crystallizable thermoplastic polymer, especially thermoplastic polyesters such as PET, and a compatabilizer. The compatabilizer my be an ethylene-maleic anhydride copolymer, an ethylene-methyl acrylate copolymer, an ethylene-methyl acrylate copolymer, an ethylene-methyl acrylate-maleic anhydride terpolymer, an ethylene-methyl-methacrylic acid terpolymer, an acrylic rubber, and ethylene-ethyl acrylate-glycidyl methacrylate terpolymer or a mixture of two or more such polymers.

Styrolux+ and styroflex+ ‐ from transparent high impact polystyrene to new thermoplastic elastomers: Syntheses, applications and blends with other styrene based polymers

Abstract: Styrolux and Styroflex are styrene and butadiene based block copolymers prepared by butyllithium initiated anionic polymerization. Styrolux is a transparent, tough and stiff thermoplastic material for high speed processing. Its specially designed molecular structure allows homogeneous mixing with general purpose polystyrene maintaining the transparency. Styroflex is a newly commercialized product with the mechanical behavior of a thermoplastic elastomer, e.g. low modulus and yield strength, high elongation and excellent recovery. High transparency and thermal stability give the competitive edge over conventional styrene-butadiene elastomers. Styroflex, Styrolux and general purpose polystyrene form a unit construction system e.g. for transparent film materials and injection molded parts with fine-tunable hardness and toughness.

Packaging material for photographic photosensitive material

Abstract: This invention provides a packaging material for a photographic photosensitive material having a conductive light-shielding thermoplastic resin film layer which comprises a resin composition comprising 3 to 49 wt. % of a thermoplastic elastomer having a crystallinity of 40% or less measured by the X-ray diffraction method, 0.01 to 10 wt. % of lubricant, and 1 to 70 wt. % of carbon black which is acetylene carbon black or furnace carbon black, which is excellent in the dispersion of carbon black to improve light-shielding ability and rare generation of lumps and microgrits, heat sealing properties, small degradation of physical strength, film moldability, etc.

Modification of thermoplastic vulcanizates using random propylene copolymers

Abstract: Random propylene thermoplastic copolymers can be used to increase the elongation to break and toughness of thermoplastic vulcanizates. Semi-crystalline polypropylene is a preferred thermoplastic phase. The rubber can be olefinic rubbers. Random thermoplastic polypropylene copolymers are different from conventional Ziegler-Natta propylene copolymers as the compositional heterogeneity of the copolymer is greater with Ziegler-Natta copolymers. This difference results in substantial differences in properties (elongation to break and toughness) between thermoplastic vulcanizates modified with random thermoplastic propylene copolymers and those modified with conventional Ziegler-Natta propylene copolymers. An increase in elongation to break results in greater extensibility in the articles made from a thermoplastic vulcanizate.

Fiber reinforced thermoplastic resin structure

Abstract: PROBLEM TO BE SOLVED: To provide a fiber-reinforced thermoplastic resin structure which comprises a thermoplastic resin and reinforcing fibers homogeneously dispersed in the thermoplastic resin and has a specific fiber length distribution and a specified fiber length. SOLUTION: This fiber-reinforced thermoplastic resin structure comprising a thermoplastic resin and reinforcing fibers, characterized in that the ratio of the weight-average fiber length of the homogeneously dispersed reinforcing fibers to their number-average fiber length is 1.1 to 3 and in that the weight- average fiber length is 2 to 15 mm.

Clustering and percolation effects in microcrystalline starch-reinforced thermoplastic

Abstract: The use of starch microcrystals as biodegradable particulate filler is evaluated by processing composite materials with a weight fraction of starch ranging from 0 to 60%. In a previous work [Macromolecules, 29, 7624] the preparation technique of a colloidal suspension of hydrolyzed starch and the processing of composite materials by freeze drying and molding a mixture of aqueous suspensions of starch microcrystals and synthetic polymer matrix were presented. Starch microcrystals with dimensions of a few nanometers were obtained from potatoes' starch granules, and it was found that this filler produces a great reinforcing effect, especially at a temperature higher than Tg of the synthetic matrix. Classical models for polymers containing nearly spherical particles based on a mean field approach could not explain this reinforcing effect. The morphology of these nanocomposite systems is discussed in light of aggregate formation and percolation concepts. The sorption behavior of these materials is also performed. Starch is a hygroscopic material, and it is found that the composites absorb more water, as the starch content is higher. The diffusion coefficient of the penetrant is predicted from modified mechanical three branch series-parallel model based on a percolation approach. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2211–2224, 1998

Water-dispersable materials

Abstract: The present invention relates to water-dispersible materials (e.g. fibers or films) and to a method of producing same. The materials of the invention comprise a water soluble component, for example, a sulfonated polycondensate thermoplastic, and a modifying auxiliary component, for example, a low melt temperature thermoplastic.

High performance elastic composite materials made from high molecular weight thermoplastic triblock elastomers

Abstract: The present invention comprises a continuous feed spun bonded laminate having improved elastic properties measured at body temperature. The laminate comprises at least one first and second nonelastic layers between which is sandwiched at least one elastic layer, the elastic layer being comprised of a triblock polystyrene-poly(ethylene/propylene)-polystyrene (“SEPS”) copolymer having a number average molecular weight of about 81,000 g/mol. The weight percent of styrene is approximately 18% and the weight percent of ethylene/propylene is approximately 82%. The molecular weight increase in the EP block, while holding the molecular weight of the styrene block constant, increases the entanglement density, polymer chain persistence length and the relaxation time. The resulting laminate load decay rate and load loss measurements over a period of 12 hours at body temperature showed marked improvement over known CFSBL product. The laminate is particularly useful as side panel material in training pants because of the resistance to sagging at body temperature.

High speed pultrusion of thermoplastic matrix composites

Abstract: The main problem with using thermoplastic matrices for composites is the difficulty in impregnating the fibrous reinforcement with the high viscosity resin. This has led to the development of a number of different manufacturing techniques, which are used to fabricate thermoplastic matrix composites. One method is to provide the matrix in fibre form and intermingle, or co-weave, the polymer fibres with the reinforcing fibres. These commingled fibres should ideally be combined in the same strand, allowing a high degree of intimacy to be achieved and minimising the flow distance for impregnation. An alternative technique is to impregnate the reinforcing tow with polymer powder particles and then melt fuse the particles in place. This method, the dry powder impregnation technique, allows for the formation of resin bridges between adjacent fibres, and with the application of applied pressure, longitudinal resin flow takes place. This differs from the transverse impregnation which occurs with the commingled fibres.These two consolidation mechanisms have been characterised and modelled using compression moulding techniques on commingled and powder towpregs, and the results of these experiments have been applied to the on-line consolidation which occurs during pultrusion processing. Successful correlation was achieved between the experimental results and the models with commingled polypropylene/glass fibres and dry powder-impregnated PA12/glass fibre-reinforced towpregs. The models then enable users to produce well-impregnated continuously reinforced composites of minimal void content at high line speeds, those reported in this work are speeds up to 10 m/min. With more powerful processing equipment, even higher line speeds could be achieved, demonstrating the potential cost effectiveness of pultruded thermoplastic composites.

Thermoplastic bonding to metals via injection molding for macro-composite manufacture

Abstract: In this work, we explore a new method of in-situ joining of polymers to metals in injection molding to allow direct bonding between thermoplastic and metal parts. Such a method can integrate several downstream steps in product manufacture, allow optimal design of products and joints, and avoid adhesive application, assembly, and associated difficlties. A variety of process parameters and their effects upon the interface tensile strengths were examined. A full factorial experiment was conducted involving four of the critical process parameters identified. The effects upon tensile strength at break of the following process parameters were studied: (1) adherend surface temperature, (2) screw linear velocity, (3) bondline thickness, and (4) pack and hold pressure. The fracture surfaces and the thermoplastic metal interfaces were analyzed. The bonds fabricated with higher adherend surface temperatures have increased mean tensile strength and less adhesive failure. This increase in mean bond tensile strength and less adhesive failure was due to increased polymer penetration of the adherend surface roughness, at the micrometer level, as shown in the analysis of the polymer-metal interface by a scanning electron microscope (SEM).

Macro- and micro-impregnation phenomena in continuous manufacturing of fabric reinforced thermoplastic composites

Abstract: Macro- and micro-impregnation of molten thermoplastic polyamide 6.6 into glass and carbon fabrics during continuous manufacturing using a double belt press was investigated. Following the analytical approaches on transverse permeability of fiber bundles, a comprehensive experimental set-up has been derived to verify the effects of temperature boundary conditions, resident time, consolidation pressure and fiber bundle permeability on the degree of impregnation. Samples with reinforcements of glass and carbon fabrics were produced at distinct processing conditions and the degree of impregnation was investigated by microscopic observation and mirrored by measuring the flexural stiffness in a three-point bending test. Hence, contribution of particular processing properties on impregnation was discussed in detail and the results are to be applied to guide the manufacturing process concerning selection of appropriate raw materials and optimized processing conditions. It could be concluded, that the continuous manufacturing process using a double belt press might basically be simulated by applying the current analytical approaches on the impregnation of fibers with thermoplastic polymers, but exhibits its own characteristics with respect to intra-bundle mechanism such as microscopic adhesion and void entrapment.

Dynamic properties of thermoplastic butadiene-styrene (SBS) and oxidized short carbon fiber composite materials

Abstract: In composites consisting of a thermoplastic butadiene-styrene (SBS) elastomer matrix reinforced with oxidized short carbon fiber, scanning electron microscopy ( SEM ) reveals the existence of matrix-fiber interactions, which are not detected when employing commercial carbon fiber. Interpretation of the dynamic properties and other parameters, such as equivalent interfacial thickness, and glass transition temperature, measured in terms of maximum damping temperature, as well as the apparent activation energy of the relaxation process, helps to explain the existence of such interactions.

Toughening of epoxies through thermoplastic crack bridging

Abstract: The fracture toughness and toughening mechanism of two epoxy matrices containing varying concentrations of pre-formed polyamide-12 particles was investigated. The pre-formed thermoplastic modifier was used to keep the physical and morphological characteristics of the second phase constant while varying the matrix intrinsic toughness to simplify the interpretation of toughening results. We observed that these particles toughened the epoxies through a crack bridging mechanism involving large plastic deformation of the second phase.This mechanism was found to be effective independent of the potential of the matrix for plastic deformation since the increasing fracture toughness was accomplished without significant amounts of plastic deformation in the epoxy matrix. A quantitative model was adapted to account for the increase in toughness due to the crack bridging mechanism. From this model, it was possible to determine the factors which are most important when attempting to toughen a material through thermoplastic crack bridging. A better understanding of the specific factors which influence the efficiency of the crack bridging mechanism enables the fracture properties of brittle materials to be further improved with thermoplastic addition. This was shown to be very important when attempting to enhance the toughness of materials which are believed to be “un-toughenable” by conventional rubber modification, or materials whose other mechanical properties suffer from the addition of elastomeric materials.

Energy absorbing articles of extruded thermoplastic foams

Abstract: An energy absorbing article having a direction in which impact resistance is desired is formed of extruded thermoplastic foam exhibit anisotropic compressive strength. The extrusion direction of the thermoplastic foam is aligned substantially parallel with the direction in which impact resistance is desired to provide an energy absorbing article exhibiting a high ratio of compressive strength to weight.

Fuel cell collector plate and method of fabrication

Abstract: An improved molding composition is provided for compression molding or injection molding a current collector plate for a polymer electrolyte membrane fuel cell. The molding composition is comprised of a polymer resin combined with a low surface area, highly-conductive carbon and/or graphite powder filler. The low viscosity of the thermoplastic resin combined with the reduced filler particle surface area provide a moldable composition which can be fabricated into a current collector plate having improved current collecting capacity vis-a-vis comparable fluoropolymer molding compositions.

Biodegradable thermoplastic composition

Abstract: Disclosed is a thermoplastic composition comprising an unreacted mixture of a poly(lactic acid) polymer; a polybutylene succinate polymer or a polybutylene succinate adipate polymer, or a mixture of such polymers; and a wetting agent. The thermoplastic composition exhibits substantial biodegradable properties yet is easily processed. The thermoplastic composition is useful in making multicomponent fibers or nonwoven structures that may be used in a disposable absorbent product intended for the absorption of fluids such as body fluids.

Laminated fiber networks

Abstract: Laminated fiber network structures having high resilience, good cushioning properties, and excellent impact-resistance include at least one layer of a three-dimensional fiber network material and a second layer, which may be a planar material (e.g. a fabric, film, or sheet) or a second layer of a three-dimensional fiber network material. The surfaces of the two layers face each other and are bonded together at their points of contact. The three-dimensional fiber network material is a fabric made from thermoplastic filaments that are at least 0.1 mm in diameter, where the fabric has an array of projections and optional depressions pushed out of one or both sides of the fabric.

Thermoplastic dicyclopentadiene-base open-ring polymers, hydrogenated derivatives thereof, and processes for the preparation of both

Abstract: Thermoplastic dicyclopentadiene-base open-ring polymers prepared by the ring-opening polymerization of a monomer component comprising a dicyclopentadiene monomer, characterized in that the polycyclic repeating units account for at least 50 mole % of the total amount of the repeating units and are bonded with a cis configuration to the carbon-carbon double bonds of the main chain and that the content of low-molecular components having molecular weights of 2,000 or below is 10 wt.% or below based on the whole of the polymer; and hydrogenated derivatives thereof prepared by hydrogenating the carbon-carbon unsaturated bonds of the thermoplastic dicyclopentadiene-base open-ring polymers.

Method for molding composite structural plastic and objects molded thereby

Abstract: A method for molding composite structural plastic components is disclosed wherein such components are cast from a polymerizable thermoset or thermoplastic composition in a conventional metalcasting mold. In the instant invention, a low viscosity thermoset or thermoplastic composition having reinforcing fibers distributed therein is poured into conventional metalcasting molds, obviating the need for high heats and pressures associated with injection or compression molding of composite materials as taught in the prior art. In the case of a thermoset resin, the object to be fabricated is fully cured by the action of a catalyst at relatively low exothermic resin temperatures. In the case of a thermoplastic resin, curing is generally achieved independently of high added heat and pressure. If using a thermoplastic such as nylon 6 in the present invention, a preferred method of use involves the addition and combination of fiber reinforcements while the nylon 6 resin is being manufactured. The process for manufacturing nylon 6 involves three components: a monomer (i.e. caprolactam), an activator and a catalyst. The typical activator is HDI-caprolactame pre-polymer and caprolactam, and the typical catalyst is aliphatic cyclic amide, sodium salt. Typical activator and catalyst ratios are 0.50-3% by weight. Components used in the production of thermoplastic resins are often available in a solid form which must be liquefied so as to be suitable for pouring into a mold. One method of liquefying solid forms of caprolactam requires melting of the monomer into a liquid and then using a catalyst and activator to complete chemical transition into a flowable thermoplastic resin and ultimately a solidified part. The catalyst and activator complete the cure into a solid nylon 6 part without the need for high added heat or injection pressures. Caprolactam monomer is also available in a molten form and nylon casting activators can be acquired in liquid form, showing similar performance in the casting process and in the finished parts. However, all three components (monomer, activator and catalyst) are usually manufactured in a solid flake form. Whether thermoset or thermoplastic, the selected resin has a sufficiently low viscosity so as to allow mixture of the resin with high percentages of reinforcement fibers and suspension of the reinforcement fibers therein. During mixing and curing, the resin's viscid state prevents the fibers from settling or grouping, thereby achieving desirable dispersion of the fibers therein. This method furthermore enables fabrication of high quality composite structural plastics in traditional soft molds and molds produced using rapid prototyping techniques. The mold itself may be made by constructing a pattern of the object to be molded and casting the mold in a liquid or soft formable material such as wax, plastic rubber or spray metal which may use extractable cores therein. Structural plastic molds made with this process can be used for prototype or production purposes. This economical molding technique permits production of quality structural molds and plastics utilizing low cost molds heretofore used only in the prototyping of plastic visual aids.

Method of forming a hybrid polymer film

Abstract: A hybrid film, comprising a first polymer film having a plasma-treated surface and a second polymer film having first and second surfaces, with the first surface of the second polymer film being disposed along the first plasma-treated surface of the first polymer film, has superior thermal and mechanical properties that improve performance in a number of applications, including food packaging, thin film metallized and foil capacitors, metal evaporated magnetic tapes, flexible electrical cables, and decorative and optically variable films. One or more metal layers may be deposited on either the plasma-treated surface of the substrate and/or the radiation-cured acrylate polymer A ceramic layer may be deposited on the radiation-cured acrylate polymer to provide an oxygen and moisture barrier film. The hybrid film is produced using a high speed, vacuum polymer deposition process that is capable of forming thin, uniform, high temperature, cross-liked acrylate polymers on specific thermoplastic or thermoset films. Radiation curing is employed to cross-link the acrylate monomer. The hybrid film can be produced in-line with the metallization or ceramic coating process, in the same vacuum chamber and with minimal additional cost.

Preforms for moulding process and resins therefor

Abstract: Binder coated fibres comprising from 80 to 99 % by weight reinforcing fibres and from 1 to 20 % by weight of a preform binder resin, said binder resin being in the form of particles or discrete areas on the surface of the reinforcing fibres, said binder resin comprising: from 40 to 90 % by weight of the binder resin of a thermosetting resin and from 10 to 60 % by weight of the binder resin of a high molecular weight engineering thermoplastic and/or an elastomer selected from vinyl addition polymer, fluororelastomers and polysiloxane elastomers, the engineering thermoplastic/elastomer being dissolved in the thermosetting resin, the binder resin being non-tacky at ambient temperature, having a softening point in the range 50 to 150 °C and being heat curable at a temperature in the range 50 to 200 °C.

Multilayer polyester sheet

Abstract: The present invention relates to a multilayer polyester sheet comprising: a base layer comprising a thermoplastic polyester resin (A) having a glass transition temperature of not less than 80° C., and a sealing layer comprising a thermoplastic polyester resin (B) having a glass transition temperature at least 5° C. lower than that of the base layer and laminated on at least one side of the base layer, said multilayer polyester sheet being a substantially non-stretched transparent sheet.