Preparation and Characterization of Conducting Systems based on EPDM/PE/PS‐co‐DVB/HSb

Summary: Blends of different compositions were prepared from: a thermoplastic elastomer (EPDM), a low density polyethylene (PE), a polystyrene crosslinked with a small amount of divinylbenzene (PS‐co‐DVB) and an inorganic proton conductor: antimonic acid (HSb). The blends obtained were sulfonated heterogeneously with chlorosulfonic acid and were then structurally and electrically characterized by means of the following techniques: differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), crystallization kinetics under non‐isothermal conditions and complex impedance spectroscopy.

Dynamic mechanical analysis for EPDM and EP‐3 blends series.     

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.

     

Toughening of Polystyrene with Ethylene‐Propylene‐Diene Terpolymer (EPDM) Compatibilized by Styrene‐Butadiene‐Styrene Block Copolymer (SBS)

Summary: Polystyrene (PS) was toughened with ethylene‐propylene‐diene terpolymer (EPDM) in the presence of styrene‐butadiene‐styrene block copolymer (SBS). Incorporation of SBS into the PS/EPDM blends clearly improved the impact properties. For PS/EPDM/SBS (mass ratio: 69/21/10) blends, the notched Charpy impact strength reached a maximum value of 26.3 kJ/m². Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that SBS was distributed on the interface between PS and EPDM. Butanone extraction and FTIR analysis found that there was a grafting reaction between PS and EPDM phase during melt compounding. Shearing and processing rheological behaviors of blends were evaluated with a Haake capillary rheometer and a torque rheometer, respectively.

     

Molecular and Morphological Characterization of Immiscible SAN/EPDM Blends Filled by Nano Filler

The compatibilizing effect of nano sized calcium carbonate filler on immiscible blends of styrene‐co‐acrylonitrile/ethylene propylene diene (SAN/EPDM) was examined. The surface energy of the calcium carbonate was modified by stearic acid. The compatibility of SAN/EPDM blends was studied by following the glass transition temperature T_g by DSC. SEM was used to observe the blend morphology and the X‐ray analyzer was used to detect the calcium from filler in samples. Mechanical properties of the blends were determined, and related to changes of polymer‐filler interactions and morphology. The results suggest that the morphology of the SAN/EPDM blends studied was affected by the reduction of surface energy of the filler.

SEM micrograph of an SAN/EPDM blend with 5% of maximally treated filler.     

Processing,Structure, and Properties of PAN/MWNT Composite Fibers

Conventional dry‐jet wet fiber spinning techniques were used to fabricate continuous PAN/MWNT composite fibers with up to 20 wt.‐% nanotube loading. PAN at the MWNT interface exhibited lower solubility under thermodynamically favorable conditions than in bulk PAN, indicating good interfacial interaction. Due to the PAN/MWNT interaction at the interface, thermal shrinkage decreases with increasing MWNT loading (5 to 20 wt.‐%). For high MWNT loadings, PAN/MWNT composite fiber at 15 wt.‐% MWNT loading showed an axial electrical conductivity of 1.24 S · m^?1. For all loadings, PAN/MWNT composite fibers exhibited higher tensile moduli than theoretically predicted by rule‐of‐mixture calculations, suggesting good reinforcement of the PAN by MWNT.

     

Formaldehyde Resins Bearing Diaminodiphenylmethane Groups: Synthesis,Characterization and Properties

Summary: Novel formaldehyde resins bearing diaminodiphenylmethane groups were synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), cyclohexanone (CHx) and o‐cresol (o‐Cz) with formaldehyde (FA) in the presence of an acid catalyst (HCl). The resins obtained were characterized by spectral, elemental and thermal analysis and used as a hardener for epoxy resins. The curing and temperature behavior of these epoxy resin/formaldehyde systems were investigated using differential scanning calorimetry and thermogravimetry techniques. The resins had good thermal stability and the activation energies of degradation reactions had values between 70–98 kJ · mol^?1.

The curing reaction of epoxy resins with the DDM/CHx/o‐Cz/formaldehyde resins.     

An Application of Silica‐Based Monolithic Membrane Emulsification Technique for Easy and Efficient Preparation of Uniformly Sized Polymer Particles

Summary: Uniformly sized polymer particles were prepared by an emulsification and polymerization technique utilizing a silica monolithic membrane, namely the “silica monolithic membrane emulsification technique”. In this paper, we utilized silica monolithic membrane as a device for the preparation of uniformly sized polymer particles. A mixture of monomers, diluents and oil‐soluble initiator was emulsified into a continuous medium through the silica monolithic membrane and polymerized. The particles obtained had a higher size uniformity than that of particles prepared by previously reported membrane emulsification techniques, such as the Shirasu Porous Glass (SPG) emulsification technique. Through the silica monolithic membrane emulsification technique, we could prepare particles having availability as a possible packing material for solid‐phase extraction (SPE) and high performance liquid chromatography (HPLC).

SEM photograph of silica particles prepared through capillary plate membrane.     

Ternary Gels of a Polymer Blend and a Recycled Oil: Their Use as Bitumen Modifiers

A blend of random ethylene‐vinyl acetate copolymer (EVA) and triblock styrene‐butadiene‐styrene copolymer (SBS) was dissolved in a recycled engine oil to obtain ternary thermoreversible gels. As the temperature was increased, first a network associated with EVA disappeared, and a second one associated with SBS dominated, maintaining the elastic response of the system. The principal advantage of these ternary systems is that their mechanical properties and thermal stability are better than that of binary gels. These gels, made from waste, can be used as bitumen modifiers to obtain binders of improved properties and good stability, which are useful for road surfacing.

Temperature sweeps of elastic modulus performed at a frequency of 1 Hz.     

Proteases to Improve the Mechanical Characteristics of Durable Press Finished Cotton Fabrics

N‐Methylol reagents are conventional crosslinking agents that are still widely used in textile industry to produce crease‐resistant cotton fabrics. In this work serine proteases were used to recover the strength of fabrics, cross‐linked with N‐hydroxymethylacrylamide. Nearly one half of the strength loss of crosslinked cotton fabrics could be restored after protease treatment, while the wrinkle recovery angle (WRA) decreased only slightly. The enzymatic hydrolysis of the amide cross‐links in the durable pressed cellulose was confirmed by FT‐IR analysis and dyeability with an acid dye.

Effect of protease concentration on the tensile strength recovery, WRA and acid dye dyeability at 30 min reaction time.     

The Solid State Postcondensation of PET, 4

Summary: A new method of polymerising PET in the solid state is proposed in either a gas phase reactor, or in hydrocarbon dispersion. It is shown that the reaction can be carried out efficiently at temperatures on the order of 200–240 °C directly from a prepolymer without the need for a melt phase step. It is shown that the crystal structure of the prepolymer plays a determining role in the kinetics of the SSP reaction.

Schema of the reactor used for gas phase SSP.     

Structure Studies on 6a-Thiathiophthenes and Related Compounds

The results from structure studies on 6a-thiathiophthenes show that different substituent groups perturb the bonding in the three-sulphur sequence to different degrees. Both equal and unequal S? S bonds occur in symmetrically as well as in unsymmetrically substituted derivatives. The specific effect of methyl and phenyl substituents on the sulphur-sulphur bonding may be described by the results from CNDO/2 calculations on mono-methyl and mono-phenyl substituted 6a-thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the S? S bonding. The structures of equally substituted 6a-thiathiophthene analogues with and show, when compared with the equivalent 6a-thiathiophthene, that and cause a pronounced change in the S? S bonding, while the perturbation caused by is negligible. In symmetrical 6a-thiathiophthene analogues with and , the average bond length in the linear three-atom sequence is 9 – 12% longer than the respective single bond.     

Improved Design of Shearing Sections with New Calculation Models Based on 3D Finite‐Element Simulations

New models for the Maddock and spiral shearing sections have been developed, employing three‐dimensional finite element analysis (3D FEA). These models describe the pressure‐throughput and power consumption behavior of the shearing sections for both the extrusion and the injection molding process and have been implemented in the REX 6.0 and PSI 4.0 simulation software. As a consequence it is now possible to describe the process behavior of these shearing sections within just a few seconds with the accuracy of FEA calculations.

Actual Maddock shearing section (left) and actual spiral shearing section (right).     

Metallized Organoclays as New Intermediates for Aqueous Nanohybrid Dispersions,Nanohybrid Catalysts and Antimicrobial Polymer Hybrid Nanocomposites

Summary: The chemical metallization of aqueous bentonite dispersions afforded stable aqueous hybrid nanoparticle dispersions containing simultaneously dispersed sodium bentonite nanoplatelets together with bentonite supported silver, palladium, or copper nanoparticles with average metal nanoparticle diameters varying between 14 and 40 nm. Such aqueous bentonite/metal hybrid nanoparticle dispersions were blended with cationic PMMA latex to produce PMMA hybrid nanocomposites containing exfoliated polymer‐grafted organoclay together with bentonite supported metal nanoparticles. This dispersion blend formation was investigated with respect to the role of nanostructure formation and mechanical properties. Palladium/bentonite hybrid dispersions were used as catalysts for hydrogenation reactions and the electroless plating of copper. In contrast to the conventional organoclay nanocomposites, the PMMA hybrid nanocomposites, containing simultaneously dispersed organoclay nanoplatelets together with organoclay supported silver nanoparticles, exhibited high antimicrobial activity against the ubiquitous bacterium Staphylococcus aureus, even at low silver content.

Preparation of a polymer hybrid nanocomposite.     

From “Strong” to “Much Stronger”: Utilization of Green Tea Extract Dispersant for SWCNT‐Reinforced Polymer Composites

PVA is reinforced with SWCNTs using green tea extract as a dispersant to achieve good dispersion of the SWCNTs in an organic solvent and finally high‐performance composite fibers. A combination of green tea extract/DMSO/SWCNT/PVA is found to disperse larger aggregates of SWCNTs to individual or thin bundles of a few nanotubes. Incorporation of 0.5 wt% SWCNTs into PVA fibers yields a tensile strength of 2.42 GPa, a Young's modulus of 46 GPa, toughness of 105 J · g^?1 at a failure strain of 11%, and a loop strength of 245 MPa, much higher than the values of commercial PVA fibers. The incorporation of highly dispersed SWCNTs suppresses the fibrillation tendency of the PVA fibers. The applied load is effectively transferred from the matrix to the SWCNTs.

     

Methionine‐Containing Poly(amino acid) Hybrid Fibers via Self‐Assembly at Aqueous Interface

Summary: Using sulfonium groups to create a novel fiber material, methionine‐containing hybrid fibers were prepared from S‐methylated poly(L ‐methionine) and poly(L ‐lysine, L ‐methionine) solutions with gellan solution by polyion complex (PIC) formation via self‐assembly at the aqueous interface. The breaking strain of the PIC fibers were increased by incorporation of methionine residues into the poly(L ‐lysine). These findings may provide a new approach for preparing a wool‐like fiber in aqueous media using the synthetic water‐soluble methionine‐containing poly(amino acid)s.

SEM image of Met‐containing PIC fiber: (a) poly[Met¹⁹Met(SMe)⁸¹]‐gellan fiber (magnification, ×500).     

Strongly Photosensitive and Fluorescent F8T2 Electrospun Fibers

Electrospun fibers of poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] (F8T2) with exceptional electro‐optical performance are obtained. The I/T characteristics measured in fibers with 7–15 µm diameter and 1 mm length show a semiconductor behavior; their thermal activation energy is 0.5 eV and the dark conductivity at RT is 5 × 10^?9 (Ω cm)^?1. Besides exhibiting a photosensitivity of about 60 under white light illumination with a light power intensity of 25 mW · cm^?2, the fibers also attain RT photoluminescence in the cyan, yellow, and red wavelength range under ultraviolet, blue, and green light excitation, respectively. Optical microscope images of F8T2 reveal homogeneous electrospun fibers, which are in good agreement with the uniformly radial fluorescence observed.

     

The Solid State Postcondensation of PET, 3

Summary: It was demonstrated that it is possible to produce prepolymers with a number‐average degree of polymerisation on the order of 5–40 directly in a liquid‐liquid dispersion in less than three hours. It was also shown that prepolymers made via this route and rapidly crystallised by the addition of a dispersant at ambient temperature are more porous than prepolymers made in an industrial liquid melt process.

SEM micrograph of prepolymers pLL‐PTA with \overline {DP} _{\rm n} = 28, d_p ∈ 63–125 μm.     

A Novel Impact Modifier for Nylon 6

A new carboxylated styrene‐butadiene rubber (CSBR) in ultrafine powder form was used to modify the properties of nylon 6. The nylon 6/CSBR blends possessed higher toughness than nylon 6/maleic anhydride‐grafted polyethylene‐octene elastomer (POE‐g‐MAH) system. TEM micrographs revealed the fine dispersion of CSBR particles with a diameter of 150 nm. The effective toughening of nylon 6 with CSBR was attributed to the good interface, fine dispersion, and shear yielding.

TEM photograph of undeformed Nylon 6/CSBR (80/20) blend (×40 000).     

Limitation of the Coalescence of Evolutive Droplets by the Use of Copolymers in a Thermoplastic/Thermoset Blend

Summary: Polystyrene (PS)/epoxy‐amine (DGEBA‐MDEA) is a thermoplastic/thermoset precursor blend which is miscible at high temperature (177 °C), and which phase separates under the polymerization of the epoxy‐amine system. Previous studies have shown that the morphology of this blend polymerized under shear is coarse and irregular because the dispersed epoxy‐amine domains coalesce before they gel. Several styrene‐methyl methacrylate and a styrene‐butadiene‐styrene block copolymers have been added to the PS/DGEBA‐MDEA 60/40 blend in order to limit the coalescence and thus obtain a finer morphology. Two of the copolymers used were reactive either with the epoxy or with the amine. It was shown that the addition of 15 wt.‐% of non reactive copolymer had a positive but limited effect on the size of the final epoxy‐amine particles. The copolymer remained at the interface at the early stages of the polymerization. However, it was pulled out by the shear forces around the gel point of the epoxy domains. Most of the non reactive copolymer was present in the shape of micelles at the end of the process. On the other hand, the reactive copolymers were able to establish covalent bonds with the epoxy‐amine drops and hence were not extracted at all. Consequently they allowed the decrease the size of the particles by a factor of 15. Despite this, the observation of the morphology at different stages of the polymerization has revealed that the copolymer moved at the interface of the epoxy domains during the collision of two droplets. The movements of fluids into the epoxy domains pushed the copolymer out of the inter‐droplet zone so that it could not prevent the drainage of the liquid film between the droplets and consequently their coalescence.

TEM showing that the layer of copolymer (in dark grey) has moved along the interface of epoxy‐amine drops during their successful collision in a polystyrene‐rich matrix.     

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.