Melt Co-extrusion Research Articles

One-step Eco-friendly Fabrication of Antibacterial Polyester Via On-line Amination Reaction by Melt Coextrusion

One-step Eco-friendly Fabrication of Antibacterial Polyester Via On-line Amination Reaction by Melt Coextrusion

Continuous fabrication of core-sheath fiber for strain sensing and self-powered application

Fiber-based sensor based on the core-sheath structure has drawn increasing attention in the strain sensing and self-powered fields because of its various advantages (e.g., lightweight, small size, flexibility and ease of weavability into soft textile, etc.). However, it still has been challenging to continuously fabricate core-sheath fiber with good interfacial interaction. Herein, a core-sheath fiber was continuously fabricated by melt co-extrusion molding method, whose sheath layer and core layer are respectively pure polystyrene polybutadiene polystyrene (SBS) and SBS/multi-walled carbon nanotubes (SBS/MWCNTs) composite. In view of this, exhibits good compatibility occurs between core layer and sheath layer because they share the same SBS phase. Moreover, with the help of sheath layer, core layer can be effectively prevented the environmental damage. Fiber strain sensor based on such core-sheath fiber exhibits a higher sensitivity (i.e., GF = 106341), wider working range (strain of 0–200 %) and shorter response time (50 ms), which can further perform underwater communication and underwater motion monitoring. Furthermore, based on such core-sheath fiber, fiber triboelectric generator (F-TENG) and textile triboelectric generator (T-TENG) have been successfully developed and they can respectively serve as self-powered bionic whisker (SPBW) and mechanical energy harvester (MEH). This study provides a facile, low-cost, continuous and environmentally friendly method to fabricate core-sheath fiber, paving a new pathway to develop fiber with strain sensing and self-powered sensing performance.

Surface-Modified Melt Coextruded Nanofibers Enhance Blood Clotting In Vitro.

Blood loss causes an estimated 1.9 million deaths per year globally, making new methods to stop bleeding and promote clot formation immediately following injury paramount. The fabrication of functional hemostatic materials has the potential to save countless lives by limiting bleeding and promoting clot formation following an injury. This work describes the melt manufacturing of poly(ε-caprolactone) nanofibers and their chemical functionalization to produce highly scalable materials with enhanced blood clotting properties. The nanofibers are manufactured using a high throughput melt coextrusion method. Once isolated, the nanofibers are functionalized with polymers that promote blood clotting through surface-initiated atom transfer radical polymerization. The functional nanofibers described herein speed up the coagulation cascade and produce more robust blood clots, allowing for the potential use of these functional nonwoven mats as advanced bandages.

High-Throughput Manufacturing of Antibacterial Nanofibers by Melt Coextrusion and Post-Processing Surface-Initiated Atom Transfer Radical Polymerization

High-Throughput Manufacturing of Antibacterial Nanofibers by Melt Coextrusion and Post-Processing Surface-Initiated Atom Transfer Radical Polymerization

Biologically Triggered Delivery of EGF from Polymer Fiber Patches.

Wound healing is modulated by complex spatial and temporal regulation of growth factors within a wound site. Regenerative medicine seeks to generate materials that can mimic this environment for the healing of chronic or traumatic wounds. Herein, we report a programmed release of epidermal growth factor (EGF) from coextruded polymer fiber patches, which is triggered by the natural biological cascade of wound healing. Genetically engineered EGF containing a matrix metalloproteinase (MMP) cleavage site was covalently conjugated to a nonwoven poly(ε-caprolactone) (PCL) fiber mat fabricated by multilayered melt coextrusion. The genetically modified EGF showed rapid release in the presence of a biological trigger, MMP-9, while a control protein showed negligible release. The biologically responsive fiber mat dramatically enhanced proliferation and migration of human keratinocytes in the presence of MMP-9. This study describes the release of a critical wound-healing growth factor as triggered by the biology inherent in the healing process.

Polymeric Nanofiber/Antifungal Formulations Using a Novel Co-extrusion Approach.

We report the successful implementation of a novel melt co-extrusion process to fabricate ca. 1μm diameter fibers of poly(caprolactone) (PCL) containing the antifungal compound clotrimazole in concentrations between 4 and 8wt%. The process involves co-extrusion of a clotrimazole-loaded PCL along with poly(ethylene oxide) (PEO) as a co-feed, with subsequent removal of PEO to isolate PCL-clotrimazole fibers. In vitro tests of the clotrimazole-containing fibers against the fungus Aspergillus fumigatus, Candida albicans, and Trichophyton mentagrophytes strains demonstrated good antifungal activity which was maintained for more than 3weeks. An in vivo study using a mouse model showed the lowest tissue fungal burden for PCL-clotrimazole when compared to a PCL-only patch and untreated controls. Comparative studies were conducted with clotrimazole-containing PCL fibers fabricated by electrospinning. Our data showed that the co-extruded, clotrimazole-containing fibers maintain activity for longer times vs. electrospun samples. This, coupled with the much higher throughput of the co-extrusion process vs. electrospinning, renders this new approach very attractive for the fabrication of drug-releasing polymer fibers.

Protein and Bacterial Antifouling Behavior of Melt-Coextruded Nanofiber Mats.

Antifouling surfaces are important for biomedical devices to prevent secondary infections and mitigate the effects of the foreign body response. Herein, we describe melt-coextruded poly(ε-caprolactone) (PCL) nanofiber mats grafted with antifouling polymers. Nonwoven PCL fiber mats are produced using a multilayered melt coextrusion process followed by high-pressure hydroentanglement to yield porous patches. The resulting fiber mats show submicrometer cross-sectional fiber dimensions and yield pore sizes that were nearly uniform, with a mean pore size of 1.6 ± 0.9 μm. Several antifouling polymers, including hydrophilic, zwitterionic, and amphipathic molecules, are grafted to the surface of the mats using a two-step procedure that includes photochemistry followed by the copper-catalyzed azide-alkyne cycloaddition reaction. Fiber mats are evaluated using separate adsorption tests for serum proteins and E. coli. The results indicate that poly(oligo(ethylene glycol) methyl ether methacrylate)-co-(trifluoroethyl methacrylate) (poly(OEGMEMA-co-TFEMA)) grafted mats exhibit approximately 85% less protein adhesion and 97% less E. coli adsorption when compared to unmodified PCL fibermats. In dynamic antifouling testing, the amphiphilic fluorous polymer surface shows the highest flux and highest rejection value of foulants. The work presented within has implications on the high-throughput production of antifouling microporous patches for medical applications.

Biphenyl-based liquid crystals for elevated temperature processing with polymers

Due to the limited thermal stability of current commercially available liquid crystals (LCs), the incorporation into polymer composites through standard processing techniques, such as melt coextrusion, has been hindered. Motivated by this dilemma, a series of smectic B liquid crystalline structures based on the 4,4ʹ-alkyl substituted biphenyl moiety were synthesised through conventional methodologies and probed for their thermal stability and LC properties. Degradation temperatures were found to increase with increasing aliphatic chain length – up to 295 °C for C16 substituted structures, which is well above the processing temperatures of commercial polymers. Additionally, all compounds were found to be liquid crystalline in nature with crystal-to-smectic B transition temperatures ranging from 49.8 °C to 91.4 °C. Thermal stability, phase separation, and compatibility of LC/polystyrene composites were also examined. Less than 10% of 15A15 LC by weight in polystyrene exhibited good polymer miscibility, while phase separation occurred at loads higher than 15% by weight. We foresee the use of these LCs in applications that require elevated processing conditions to produce materials with enhanced mechanical or gas barrier properties.

Thermochromic composite fibres containing liquid crystals formed via melt extrusion

A three-layered composite fibre has been generated via a modified wire-coating melt co-extrusion process. The continuous fibre consists of a thermochromic liquid crystalline (TLC) layer encapsulated between a transparent polypropylene outer sheath and a black polyether ether ketone inner core. The fibres exhibit clear thermochromic behaviour consistent with the behaviour of unincorporated TLCs, and have been formed into a textile. The presence of the black inner core was found to be the key for the clear retention of colour within the fibres against both white and black backgrounds. The temperature-sensitive fibres and textiles can be applied to a variety of thermal mapping applications, such as in the medical and engineering fields, due to the tunable nature of TLCs.

Deformation of Confined Poly(ethylene oxide) in Multilayer Films

The effect of confinement on the deformation behavior of poly(ethylene oxide) (PEO) was studied using melt processed coextruded poly(ethylene-co-acrylic acid) (EAA) and PEO multilayer films with varying PEO layer thicknesses from 3600 to 25 nm. The deformation mechanism was found to shift as layer thickness was decreased between 510 and 125 nm, from typical axial alignment of the crystalline fraction, as seen in bulk materials, to nonuniform micronecking mechanisms found in solution-grown single crystals. This change was evaluated via tensile testing, wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). With the commercially relevant method of melt coextrusion, we were able to overcome the limitations to the testing of solution-grown single crystals, and the artifacts that occur from their handling, and bridged the gap in knowledge between thick bulk materials and thin single crystals.

Physical aging of layered glassy polymer films via gas permeability tracking

The physical aging of polymers in confined environments has been an area of intensive study in recent times. The rate of physical aging in thin films of many polymers used in gas separation membranes is dependent on film thickness and accelerated relative to bulk. In this study, the physical aging of polymer films with alternating glassy polysulfone and rubbery polyolefin layers was monitored by measuring the gas permeability of O 2 and N 2 as a function of aging time at 35 °C. The alternating layer structures were formed by a melt co-extrusion process. The polysulfone layers have thicknesses ranging from 185 to 400 nm, and the overall thicknesses of the films are on the order of 80–120 μm. The aging of freestanding thin films of polysulfone is rapid and exhibits clear thickness dependence, whereas the aging of multilayered films was observed to be similar to bulk and showed no dependence on layer thickness. At 1000 h of aging time, a 400 nm freestanding PSF film decreased in O 2 permeability by 35%, whereas on average the bulk and multilayered films only experienced a decline of 10–15%. A slight increase in O 2/N 2 selectivity for the multilayered films was observed over the course of aging.

Polymer grafted silver and copper nanoparticles with exceptional stability against aggregation by a high yield one-pot synthesis

A straightforward synthesis of silver nanoparticles (mean diameters well below 4 nm) with a “graft-to” polystyrene shell (PS@Ag) is described and different synthesis routes are compared. In addition to standard methods like TEM, XRD, UV/Vis and DSC the hybrid material has also been characterized by gel permeation chromatography (GPC).Long-term stable hybrid materials with silver contents up to 18 wt-% have been realized. The exceptional stability allows industrial-scale processing by melt extrusion. No aggregation or agglomeration of silver nanoparticles is observed after melt co-extrusion with conventional polystyrene at 190 °C. The co-extruded blends with silver nanoparticle contents up to 1 wt-% show a homogenous dispersion of nanoparticles in the polystyrene matrix. The synthesis route has also been applied to PS-block-PMMA stabilized silver nanoparticles and to copper to yield polystyrene-stabilized copper nanoparticles with diameters well below 3 nm.

Plastic deformation of low‐density polyethylene reinforced with biodegradable polylactide, Part 1: Microstructural analysis and tensile behavior at constant true strain‐rate

AbstractBlends of low‐density polyethylene (LDPE) and polylactide (PLA) were prepared by melt coextrusion. The plastic behavior of the LDPE/PLA blends was investigated at room temperature under uniaxial tension by means of a video‐controlled system. The constitutive behavior was analyzed in terms of the variations of true stress vs. true strain at constant true strain rate. With increasing concentrations of PLA, the blend show: (i) higher Young's modulus, (ii) stiffer viscoelastic response, (iii) increase of elastic limit stress, and (iv) earlier fracture. Particular attention was paid to the evolution of the volume strain with the applied strain. While dilatation begins very lately for the neat LDPE, the LDPE/PLA blends show increasing deformation damage as the PLA content is increased. Scanning electron microscopy of deformed specimens shows that cavitation occurs preferentially at the poles of the PLA particles whose adhesion to the LDPE matrix seems very weak despite the partial grafting of polyethylene chains with maleic anhydride. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.

Incorporation of lead phthalocyanine into periodic nanolayered assemblies for advanced optical systems

AbstractPeriodically structured polymeric materials can lead to the next generation of electro‐optic and nonlinear optical devices for applications in information technology. Layer‐multiplying melt coextrusion is an attractive method for fabricating periodic structures with thousands of alternating polymer microlayers or nanolayers. Many advanced applications for periodic polymeric structures would be enabled by locating a photoactive dye in one or both layers. However, it is anticipated that due to the thinness of the individual layers and the relatively low molecular weight of many dyes, a substantial fraction of the dye will diffuse from the doped layers into the undoped layers during melt coextrusion. In the present study, we demonstrate two methods for confining the activity of a photoactive dye, lead phthalocyanine, to the doped layers. Polycarbonate containing lead phthalocyanine was coextruded with undoped polyester as an assembly of 128 alternating 86 nm‐thick layers. Using the absorption spectra, we demonstrated that a high concentration of the monomer form persisted in the polycarbonate layers, whereas the lead form was converted to the less active lead‐free form in the polyester layers. Thus, the active monomer form of PbPc(β‐CP)4 was maintained selectively in the polycarbonate layers. In the second approach, the coextrusion process was altered so that the alternating polycarbonate and polyester layers were separated by a thin layer of a barrier polymer. The barrier layer prevented diffusion of the dye during melt coextrusion and the dye remained selectively in the polycarbonate layers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Theoretical and experimental characterization of stearic acid-based sustained release devices obtained by hot melt co-extrusion

This study was conducted to develop and characterize a hot melt co-extruded cylindrical system for controlled drug delivery. Different lengths and configurations (homogeneous, hollow and heterogeneous) co-extrudates were considered. Stearic acid and polyethylene glycol were used as hydrophobic and hydrophilic components, respectively. Acetaminophen and theophylline were used as model drug. Release kinetics were studied on the basis of in vitro tests and experimental data were analyzed by a new mathematical model accounting for drug dissolution and diffusion inside the cylindrical matrix. Surface tension measurements were carried on the two model drugs and the hydrophobic matrix. Experimental results showed that co-extruded length and configuration sensibly affect release kinetics of both drugs. Additionally, the proposed mathematical model proved to be reliable and yielded an explanation for the lower acetaminophen release rate with respect to that of theophylline. This behavior could be explained by the formation of a low permeable layer surrounding the acetaminophen-loaded systems. In addition, surface property analysis evidenced the higher hydrophobic nature of acetaminophen-loaded systems with respect to theophylline systems.