Preparation of Ultrafine Ethylene/Propylene/Diene Terpolymer Rubber Fibers by Coaxial Electrospinning

Elastomeric EPDM fibers with diameters of 200–400 nm are prepared by coaxial electrospinning of PVP/EPDM fibers, subsequent vulcanization of the polymers and finally removal of the outer PVP layer using ethanol. The initially applied PVP layer restricts the elastic recovery of the EPDM fibers. The crosslinking density of the EPDM fibers reaches 8.44 × 10^?5 mol · cm^?3. The original morphology of EPDM is preserved after removing the PVP layer. The ultrafine EPDM fibers are expected to be useful in many fields, such as brittle plastics toughening, as well as applications in extremely high or low temperatures.

     

Fabrication of Aligned Poly(L‐lactide) Fibers by Electrospinning and Drawing

A new target collector was designed for taking up aligned nanofibers by electrospinning. The collector consists of a rotor around which several fins were attached for winding electrospun filaments continuously in large amounts. The alignment of the nanofibers wound on the collector was affected by the electrospinning conditions, such as the needle‐to‐collector distance and the applied voltage, but not by the rotation speed of the collector. At a voltage of 0.5 kV · cm^?1, about 60% of the fibers were found to be aligned within an angle of ± 5° relative to the rotational direction of the collector. The fiber alignment was improved to 90% by drawing the fiber bundle 2–3 times at 110 °C. The drawing was also effective for crystal orientation of the fibers as revealed by WAXD. The drawn fibers show improved mechanical properties.

     

Epoxy Resin Nanofibers Prepared Using Electrospun Core/Sheath Nanofibers as Templates

A strategy is described to prepare epoxy resin nanofibers by combining coaxial electrospinning and traditional hot‐curing processes. Core/sheath nanofibers with diameters of 480 ± 80 nm are prepared at flow rates of 0.1 and 2 mL h^?1 for the core (20% w/v EP and 6% w/v curing agent in ethanol/acetone) and sheath (10% PVP in ethanol) fluids. After the curing of the nanofibers and selective removal of the sheath PVP, EP nanofibers with an average diameter of 210 ± 60 nm are obtained. ATR‐FTIR analysis shows that the EP nanofibers display no obvious difference compared with an EP film cast from the core solution. The method presented allows to develop functional EP nanoproducts and to prepare heat‐cured resin nanofibers.

     

Thermoplastic Polyurethane Nanocomposites Produced via Impregnation of Long Carbon Nanotube Forests

TPU was infiltrated into vertically aligned, 3.5 mm‐long MWNT forests to produce continuously reinforced anisotropic nanocomposites, and thermomechanical and electrical testing has revealed multifunctionality which shows promise for numerous applications. A 1000% increase in the storage modulus at 70 °C was observed as compared to the neat TPU, and these continuously aligned composites showed electrical conductivity two orders‐of‐magnitude greater (≈1.5 S · cm^?1) than randomly aligned composites prepared using CNTs from these forests. The heightened improvement for the continuously reinforced composite appears to be owed to the extremely high aspect ratio of these CNTs and the interconnected network which remains after infiltration.

     

Direct Melt Extrusion Processing of Nylon 6/Clay Nanocomposites Based on Pristine Montmorillonite

Summary: An original direct melt extrusion processing of nylon 6/clay nanocomposites was reported based on pristine (Na⁺‐based) montmorillonite as well as a simple approach using a typical two‐screw extruder. By the application of intercalation agents as the thermodynamic assistants, this method is as an appropriate procedure for industrialized manufacture together with much lowered production cost. Interestingly enough, the synergistic effects of montmorillonite with other inorganic particulates was observed for the first time here.

X‐ray diffraction patterns of pristine MMT and nylon 6/MMT composites with grouped intercalation agents.     

Rigid‐Rod Polymers: Synthesis,Processing, Simulation,Structure, and Properties

Synthesis, structure, and properties of rigid‐rod polymers with special emphasis on poly(p‐phenylene benzobisoxazole) (PBO) and poly(p‐phenylene benzobisthiazole) (PBZT) have been reviewed. Recent studies on chemical modifications and molecular simulations have also been given. After nearly 20 years of research and development, PBO fiber was commercialized in the late 1990s. However, due to processing difficulties, the concept of the so called molecular composites has not been successful. Development of the high compressive strength M5 and dihydroxy‐PBI fibers clearly suggest that there is potential for further developing properties of this class of materials. Opto‐electronic properties have also been reviewed.

Synthesis of PBZT.     

The Reinforcement of Elastomeric Networks by Fillers

Summary: The mechanisms involved in rubber reinforcement are discussed. A better molecular understanding of these mechanisms can be obtained by combining characterization of the mechanical behavior with an analysis of the chain segmental orientation accompanying deformation. While the strain dependence of the stress is the most common quantity used to assess the effect of filler addition, experimental determination of segmental orientation can be used to quantify the interfacial interactions between the elastomeric matrix and the mineral inclusions.

SEM micrograph of natural rubber containing 10 wt.‐% of organomodified clay.     

Coaxial Electrospinning with Triton X‐100 Solutions as Sheath Fluids for Preparing PAN Nanofibers

Coaxial electrospinning using surfactants as sheath fluid for preparing high‐quality polymer nanofibers is studied. PAN nanofibers are fabricated using this process with Triton X‐100 solutions in DMF. FESEM demonstrates that the Triton X‐100 solution has a significant influence on the quality of the nanofibers. The nanofiber diameters can be controlled by adjusting the concentration of Triton X‐100 in the sheath fluids with a scaling law D = 640 C^?0.32. The mechanism of the influence of Triton X‐100 solutions on the formation of PAN fibers is discussed and it is demonstrated that coaxial electrospinning with surfactant solution is a facile method for achieving high‐quality polymer nanofibers.

     

Properties of Poly(3‐hydroxybutyric acid) Composites with Flax Fibres Modified by Plasticiser Absorption

Natural fibre‐biopolymer composites have been prepared from flax and polyhydroxybutyrate (PHB). The flax was modified by drying, followed by plasticiser absorption to replace the water lost to prevent embrittlement. This protects the fibres from problems associated with their water content and changes in water content due to equilibration with the environment. Flax and PHB showed good interfacial adhesion, which was decreased when plasticisers were present. Some plasticiser migrated from the flax to PHB and caused complex changes in the glass transition, crystallisation and crystallinity of the PHB. Morphology of the composites was examined by scanning electron microscopy (SEM) and optical microscopy (OM), SEM provided information on the interfacial adhesion through fractography. OM showed extensive transcrystallinity along the fibre surfaces. Dynamic mechanical analysis was used to measure elastic and damping characteristics and their relation to composition and morphology.

SEM micrograph of the PHB‐plasticiser‐flax system PHB‐PEG‐flax.     

Laccases to Improve the Whiteness in a Conventional Bleaching of Cotton

This study reports for the first time on the enhancement of the bleaching effect achieved on cotton using laccase enzyme. Laccases applied in short‐time batchwise or pad‐dry processes prior to conventional peroxide bleaching, improved the end fabric whiteness. The whiteness level reached in the combined enzymatic/peroxide process was comparable to the whiteness in two consecutive peroxide bleaches.

Effect of 10 min laccase pre‐treatment at 60 °C, pH 5 on fabrics whiteness before and after a conventional hydrogen peroxide bleaching.     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

The Effect of Mold Temperature on the Performance of Injection Molded Poly(lactic acid)‐Based Bioplastic

This research investigates the effects of processing parameters, namely molding temperature on the mechanical performance of impact‐modified poly(lactic acid) (PLA). Polymer crystallization dictates many of the final properties of the material. Increasing the mold temperature, crystallization may progress to a further stage, increasing crystallinity. Molding at a lower temperature, and producing a highly amorphous polymer can increase the mechanical properties, namely elongation and impact strength. Molding at 30 versus 90 °C improved the elongation from 22 to 243% and the impact strength from 67 to 133 J · m^?1. This improvement is not without its drawbacks. By molding at 30 °C, the polymer becomes very amorphous, and thus is more susceptible to unwanted processes such as physical aging.

     

Extrusion Monitoring of Polymer Melts Using a High‐Temperature Surface‐NMR Probe

Summary: Extrusion is one of the major ways of polymer processing, and extrusion monitoring is important to control or improve the extrusion process and the product quality. Especially methods for in‐line monitoring are desired because those enable the fastest possible response and a localization of chemical reactions in reactive processing. Methods of optical and acoustic spectroscopy have successfully been implemented so far. NMR provides a wealth of information. Surface NMR mostly gives access to molecular mobility via relaxation times. These can be correlated to temperature, composition and homogeneity which are substantial indicators for the product quality. NMR is a non‐destructive method, which does not require direct contact with the sample and it is not restricted to optical transparent materials and is therefore suitable for extrusion monitoring. The problem for the adaptation is the hostile environment in and in front of an extruder for polymer melts. Here, a NMR surface probe is presented sustaining this environment in front of an extruder. First measurements with this device are shown.

High‐temperature surface‐NMR probe.     

Micromechanical Processes in PET/PC Multilayered Tapes: High Voltage Electron Microscopy Investigations

Summary: A totally new kind of multilayered tape consisting of two macroscopically ductile polymers (PET and PC) was studied using high voltage electron microscopy (HVEM). Both components were co‐extruded as uniform laminates with thousands of alternating layers. The multilayered PET/PC samples were annealed at high temperature. Investigation of the multilayered PET/PC tapes with various compositions clearly demonstrated a transition of the microdeformation mechanism which was dependent on the thickness of the individual layers. The annealing of the tapes led to a significant change in the deformation behavior. However, no lamellae formation was revealed in the PET phase after annealing, leading to the assumption of constrained crystallization in very thin PET layers.

     

Design of a Microfluidic System to Investigate the Mechanical Properties of Layer‐by‐Layer Fabricated Capsules

A microfluidic system was designed, fabricated and implemented to study the behavior of polyelectrolyte capsules flowing in microscale channels. The device contains microchannels that lead into constrictions intended to capture polyelectrolyte microcapsules which were fabricated with the well‐known layer‐by‐layer (LbL) assembly technique. The behavior of hollow capsules at the constrictions was visualized and the properties of the capsules were investigated before and after introduction into the device.

Time series of video frames showing capsules being compressed into a constriction.     

Compatibilization of Poly(propylene)/Polyamide 6 Blends with Functionalized Poly(propylene)s Prepared with Metallocene Catalyst

Summary: Propylene was copolymerized with 10‐undecen‐1‐ol using dimethylsilanylbis(2‐methyl‐4‐phenyl‐1‐indenyl)zirconium dichloride as catalyst and MAO and TIBA as cocatalysts. Comonomer incorporations from 0.1 to 0.9 mol‐% (0.5 to 3.6 wt.‐%) were obtained. These hydroxyl functionalized copolymers were applied as compatibilizers to PP/PA6 blend with a composition of 70/30. For comparison, hydroxyl functionalized polyethylene prepared with metallocene catalyst and commercial MAH grafted ethylene butyl acrylate (E/BA/MAH) and poly(propylene) (PP‐g‐MAH) were also used as compatibilizers. Effects of the compatibilizers on morphology and mechanical and thermal properties of the blends were studied. Enhanced adhesion between the blend components was observed in morphology and dynamic mechanical studies. Although improvement in toughness was not as pronounced as expected, there were indications that the hydroxyl functionalized propylene copolymers prepared with metallocene catalysts could serve as a new type of compatibilizer in polymer blends.

SEM micrograph (5 000×) of an PP/PA6/PP‐co‐OH4 blend.     

Synthesis of 3‐Iodoquinolines by Copper‐Catalyzed Tandem Annulation from Diaryliodoniums,Nitriles, and 1‐Iodoalkynes

A novel method for the synthesis of 3‐iodoquinolines was developed by copper‐catalyzed tandem annulation from diaryliodoniums, nitriles, and 1‐iodoalkynes. It is a method that is characterized by the most convenient operation and wide molecular diversity.

     

Poly(vinyl acetate)/Silver Nanocomposite Microspheres Prepared by Suspension Polymerization at Low Temperature

Summary: High molecular weight (HMW) poly(vinyl acetate)/silver nanocomposite microspheres (PVAc/Ag), which are promising precursors of embolic materials with radiopacity, were prepared via a suspension polymerization approach in the presence of silver nanoparticles. It was found that a high yield and high molecular weight PVAc/Ag could be concurrently obtained even using a low‐temperature initiator 2,2′‐azobis(2,4‐dimethylvaleronitrile) (≈30 °C). In the case of presence of silver nanoparticles, the rate of polymerization was slightly slower than that without Ag. The suspension polymerization approach introduced could produce PVAc/Ag composite with conversion and viscosity‐average molecular weight ( ) up to 95% and 1 300 000, respectively, in spite of the low polymerization temperature (≈30 °C), in sharp contrast with an only ≈30% conversion of VAc under bulk polymerization. Morphology studies revealed that except normal suspension microspheres with a smooth surface, a golf ball‐like appearance of the microspheres was observed, due to the migration and aggregating of the hydrophilic Ag nanoparticles at the sublayer beneath the microsphere's surface.

     

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

Flame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.

TEM of PA‐n nanocomposite.     

Transcrystallinity in Surface Modified Aramid Fiber Reinforced Nylon 66 Composites

Aramid (kevlar‐49) fibers were surface treated by two different methods to induce roughness and then used to produce unidirectional nylon 66 based composites. The transcrystallinity generated around the treated fibers was characterized by SEM and polarized light microscopy and compared with the regular transcrystalline layers produced by pristine aramid under the same processing conditions. The treated fibers generated a double transcrystalline layer, the inner layer being thinner and more compact than the regular nylon 66 transcrystallinity. In addition, mechanical testing of the composites showed the longitudinal Young's modulus of the treated fiber composites to be significantly higher than the control in a wide range of fiber volume fractions.

Polarized light microscopy picture of double transcrystallinity in Br/NH₃ treated aramid fiber reinforced nylon 66.