Dry Powder Impregnation Research Articles

Preliminary Studies on an Innovative Bioactive Skin Soluble Beauty Mask Made by Combining Electrospinning and Dry Powder Impregnation

The world of cosmetics is now aiming at biobased materials which are skin-compatible and can be used to generate more sustainable beauty masks with enhanced bioactivity. This work presents, in this line of interest, the combination of two innovative technologies, namely electrospinning and dry powder impregnation, to generate biobased skin soluble electrospun pullulan carriers dry impregnated with chitin nanofibrils-nanolignin-glycyrrethinic acid (CLA) complexes, as effective biobased and skin compatible beauty masks. The scalability of the pullulan electrospun carrier and bioactive complexes impregnation were optimized and the morphology evaluated. Subsequently, skin compatibility and mask effectiveness were investigated in vitro and in vivo. The results showed that cell viability was optimal for both impregnated and neat pullulan fibers. Additionally, the CLA impregnated pullulan fibers were able to upregulate the endogenous antimicrobial molecule HBD-2. Preliminary studies in vivo indicated that the beauty mask containing the CLA complexes significantly decreased area, length and depth of forehead and crow’s feet wrinkles, and significantly increased moisturizing levels in the skin. The developed beauty mask was also seen to increase skin firmness, while it did not show skin irritation after the test. The work demonstrates that the combination of these two technologies may open new alternatives to more sustainable bioactive cosmetic products for the skin.

Fabrication of nanocomposite powders with a core-shell structure

This study presents a new process for producing nanocomposite powders for use in various manufacturing processes such as laser sintering or dry powder impregnation techniques for thermoplastic composites manufacture. Polyetherimide (PEI) was used as a polymeric coating/shell to encapsulate nanoparticles on the surface of poly ether ether ketone (PEEK) particles, which were used as a core matrix. Nanoparticles with different morphologies, known to enhance thermal and electrical performance of polymers: 2D graphene nanoplatelets (GNPs) and inorganic fullerene-like tungsten disulfide (IF-WS2) in different concentrations (0.1, 1, and 5 wt%) were incorporated in the shell structures. The coated powders had approximately the same particle size distribution as the uncoated, plain powders, which is an indication that the shell was in nm size and the coating process did not affect the overall size of the particles. Furthermore, the core-shell particles exhibit a smoother surface and an improved flowability after coating. The Transmission Electron Microscopy (TEM) images of the nanocomposite particles cross-section area confirmed the formation of core-shell structure, and the presence of the nanoparticles embedded into the shell layer. The scanning electron microscopy (SEM) images showed a homogeneous distribution of nanoparticles within the coating layer at lower nanoparticle concentrations (0.1 and 1 wt%).

Combining product engineering and inherent safety to improve the powder impregnation process

The functionalization of nonwoven textiles can be realized by dry powder impregnation. In order to develop and improve this process, two complementary approaches have been combined: product engineering and inherent safety. It consists in integrating ab-initio consumers' requirements, production constraints as well as safety and environmental considerations. This case study is focused on the proposal, the characterization and the selection of powders mixtures of flame retardants and copolyesters, which will be used to create fire-proofed textiles. The influences of the chemical natures of the flame retardant (e.g. calcium carbonate, aluminium trihydroxide, ammonium polyphosphates), their respective concentrations, particle diameters and the addition of silica to flame retardant/polymer mixtures on their minimum ignition energy has been investigated. It has been determined that ammonium polyphosphates are far more efficient than other flame-retardants and that a minimum of 20%wt. concentration is needed to generate a powder mixture that will be almost insensitive to ignition by an electrostatic source. Modifying the particle size distribution and introducing glidants play also a significant role on flame retardant/polymer interactions, on powder dispersibility and has a strong impact on the minimum ignition energy. Finally, the formulations which have been selected fulfill the requirements for fire resistance, flowability, prevention of dust explosion; they are non-toxic, environmentally friendly and their cost is reduced.

Effect of Fiber Treatment on Fiber Strength and Fiber/Matrix Interface of Hemp Reinforced Polypropylene Composites

The use of natural fibers as reinforcement in composites is emerging. Several studies are underway to improve the mechanical characteristics of these fibers and its matrix interface properties for better load transfer. However, the treatments generally used are relatively expensive and complicated to apply. This work deals with the effect of new Fibroline process on tensile and interfacial properties of hemp fiber reinforced in polypropylene. Fibroline is a dry powder impregnation method which consists of submitting fibers and polymer powder under strong alternating electric field. Morphology and tensile properties of hemp fibers after different surface treatments (raw, dried, raw and Fibroline-treated, dried and Fibroline-treated) are evaluated. Interface properties of treated hemp fibers on polypropylene matrix are then characterized by fragmentation test of monofilament composites. Results showed the Fibroline treatment reduces the fiber mechanical properties but improves the load transfer efficiency due to random generation of surface cracks and better fiber/matrix adherence, respectively. For the case of dried and Fibroline-treated hemp fibers, large decrease in mechanical and interfacial properties was observed.

Manufacture of aramid fibre reinforced nylon-12 by dry powder impregnation process

The present paper deals with the manufacturing of composites, consisting of continuous aramid fibres and nylon-12, by applying the so-called dry powder impregnation process. The fibres are pre-impregnated by the deposition of fluidised powder particles on aramid fibre tows which are consolidated by heat and pressure to form continuous prepregs. Features of the nylon-12 powders which are important for the dry powder impregnation process are discussed. Material, tool and processing parameters influencing the achievement of impregnation and therefore the fibre volume content of the prepregs are outlined.

High speed pultrusion of thermoplastic matrix composites

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.

Production and characterization of UHMWPE fibers/LDPE composites

The production of unidirectionally fiber-reinforced composites (tapes) consisting of high-strength/high-modulus UHMWPE fibers and LDPE matrix is described. Two production techniques are applied: impregnation by aqueous powder dispersion and dry powder impregnation. The produced composites exhibit excellent mechanical properties. Depending on the fiber volume content which can be obtained: tensile strength (in fiber direction) 460–1100 MPa, elastic modulus 11–22 GPa, and elongation at break 4.9–8.3%.

Ribbonizing of electrostatic powder spray impregnated thermoplastic tows by pultrusion

Process models have been developed for thermoset pultrusion and thermoplastic pultrusion using melt impregnated prepregs. Thermoplastic towpregs are manufactured using new innovative methods such as those using dry powder impregnation. The morphology of dry powder impregnated ‘towpregs’ consists of a dry fibre bundle surrounded by a layer of polymer. In this study a two-dimensional finite element model using non-Newtonian fluid properties was developed to predict the pulling force for ribbonizing of a single thermoplastic powder impregnated towpreg via pultrusion. This is the first model that used a dual medium finite element approach to capture the microstructure of the dry powder impregnated towpregs. The model was experimentally verified using PEKK (Poly Ether Ketone Ketone) powder coated glass fibre tows for two die taper angles of 0.17° and 0.34°. The experiments were conducted at 350°C and the pulling speeds used ranged from 3 mms 1 to 19 mms −1. The model predicted that the pulling force increased monotonically as a function of the pulling speed. The experimentally obtained pulling force increased as a function of pulling speed until the pulling speed was ∼8 mms −1 and then reduced. The pulling force increased with increase in the taper angle for the same total die length. The model predicted that the shear force was the dominant part of the pulling force.

Manufacture of polyphenylene sulfide (PPS) matrix composites via the powder impregnation route

A consolidation model is applied to powder-impregnated composites. The model predicts the time evolution of the void volume fraction as a function of the applied pressure during consolidation. The applied pressure is considered to be composed of resin pressure obtained from a solution of the flow of resin along a channel formed by three parallel fibres. Micrographs support the geometrical assumptions of the model. Good correlation is achieved with experimental data produced from consolidated polyphenylene sulfide glass fibre (PPS/GF) laminates pultruded using the dry powder impregnation technique. Void measurements were taken at three points during processing and are seen to increase linearly with the final fibre volume fraction of the composite. Flexural and interlaminar shear stregth tests are used to correlate the mechanical properties with respect to the impregnation quality, in particular the void content, of the laminates.

Influence of processing conditions on the tensile properties of unidirectional UHMWPE fibre/LDPE composites

Unidirectional composite tapes comprising ultra-high molecular weight polyethylene fibres in a low density polyethylene matrix were produced by a dry powder impregnation technique. Tensile as well as X-ray diffraction studies were carried out to determine the influence of reprocessing on the composite properties. Tensile modulus was not strongly influenced, while tensile strength decreased on reprocessing. The decrease in tensile strength has been explained on the basis of X-ray diffraction patterns.

Manufacture of Powder-Impregnated Thermoplastic Composites

The use of thermoplastic composites has been limited by the lack of reliable techniques to make prepregs of consistent quality. Dry powder impregnation methods offer a new approach to the solution of this problem. This paper discusses the features that are essential to the development of an acceptable dry powder process The physical principles that govern the manufacture of thermoplastic prepreg tapes of controllable fiber-matrix volume fractions and the consolidation of these tapes to make void-free composite parts are presented A novel powder prepregging process suitable for the manufacture of high-quality powder-impregnated tapes and their subsequent consolidation to make void-free parts is discussed. It is shown that a well-designed dry powder process can achieve fine control over both fiber-matrix composition in the prepreg tape and intimate wetting between in dividual fibers and the thermoplastic matrix Powder prepreg tapes can be consolidated into void-free specimens with simple consolidation cycles developed for a specific fiber- matrix combination