Preparation and Characterization of Organic/Inorganic Polymer Composites Based on Mg‐Silicates

Summary: An organic‐inorganic hybrid material consisting of a 3‐(methacryloxy)propyl functionalized SiO₂/MgO framework was synthesized. This hybrid was successfully reacted with styrene, butyl acrylate and butyl methacrylate via a free radical emulsion polymerization to form polymer composites. The polymer composites were investigated by means of FT‐IR spectroscopy, TGA, DSC and rheometry. It is shown that the polymer is linked covalently to the organic/inorganic hybrid. Although the polymer content is rather low, the composites exhibit a polymer‐like character and enhanced mechanical properties compared to the corresponding homopolymers.

     

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.

     

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.     

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.     

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.     

From PET Nanofibrils to Nanofibrillar Single‐Polymer Composites

The preparation of nanofibrillar composite (NFC) materials using single‐polymer nanofibrils as starting materials is described. Such a possibility is offered by (i) the concept of polymer/polymer NFCs, which have recently been manufactured and represent a further development in the field of microfibril‐reinforced composites, and (ii) the opportunity to isolate neat nanofibrils through selective dissolving of the second blend component. The resulting nanofibrillar single‐polymer composites are characterized by superior mechanical properties (the tensile modulus and strength are improved up to 350%), competing with glass‐fiber‐reinforced PET.

     

A Novel Phosphorus‐Containing Polymer as a Highly Effective Flame Retardant

Summary: A novel phosphorus‐containing polymeric retardant, WLA‐3, was synthesized from phenylphosphonic dichloride (PPD) and 2‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl) 1, 4‐benzenediol (ODOPB). The flame‐retardant element, phosphorus, was bonded both in the main chains and in the pendant chains of flame‐retardant polymer molecules, and reached a content of 13.8%. The high phosphorus content and rich aryl group structures of WLA‐3 contribute an excellent flame retardancy to poly(ethylene terephthalate) (PET) without a considerable decrease of mechanical properties. WLA‐3 is also very effective in improving flame retardancy of epoxy resin and unsaturated polyester.

     

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.     

Impact Strength and Crystallization Behavior of Nano‐SiOx/Poly(phenylene sulfide) (PPS) Composites with Heat‐Treated PPS

The effects of heat treatment on the crystal structure and impact strength of poly(phenylene sulfide) (PPS) and nano‐SiO_x/ PPS nanocomposites were studied. The molecular weight of heat‐treated neat PPS was increased by 28% due to the crosslinking reaction that changed its crystal morphology. Also, the crystallinity was reduced by 18%, leading to an improvement of the Izod impact strength by 66%. Nano‐SiO_x/PPS composites were manufactured by intensive compounding with 3 wt.‐% nano‐SiO_x particles treated by an epoxy functional group. Test results showed that the Izod impact strength of nano‐SiO_x/heat‐treated PPS composites was 91% better and the crystallinity 27% less compared to the same properties of “as received” neat PPS. Nano‐SiO_x has a high specific surface area and a high surface energy; its grafted epoxy group promotes interfacial adhesion with the PPS matrix, hence increasing the Izod impact strength of the nanocomposites.

TEM micrograph of NHTM‐PPS with 3 wt.‐% nano‐SiO_x.     

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.     

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.

     

Photoinduced Polymerization in the Wall of Hollow Capsules

Summary: Novel light‐sensitive hollow capsules were fabricated from the small molecule 3‐sulfopropylacrylate potassium (SPA) and poly(allylamine hydrochloride) (PAH). With UV irradiation, SPA could be photopolymerized in the wall of hollow capsules. After photopolymerization the capsule size and surfaces showed pronounced differences. The capsules became much more rigid as indicated by an increase in the modulus of more than a factor of 5.

CLSM image of SPA/PAH hollow capsule emission at 554 nm, from rhodamine B after photopolymerization.     

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).     

Harnessing the Melting Peculiarities of Ultra‐High Molecular Weight Polyethylene Fibers for the Processing of Compacted Fiber Composites

Summary: Compacted fiber composites offer unique properties due to their lack of an extraneous matrix. The conditions of processing ultra‐high molecular weight polyethylene (UHMWPE) fibers were simulated in a heated pressure cell. In situ X‐ray diffraction measurements were used to follow the relevant transitions and the changes in the degree of crystallinity during melting and crystallization. The results strongly support the suggestion that the hexagonal crystal phase, in which the chain conformation is extremely mobile on the segmental level, constitutes the physical basis of compaction technologies for processing UHMWPE fibers into a single‐polymer composite. This report suggests that using a pseudo‐phase diagram outlining the occurrence of different phases during slow heating and the degree of crystallinity can provide valuable insight into the technological parameters relevant for optimal processing conditions.

Degree of crystallinity as a function of pressure and temperature in a region relevant to compaction processes.     

Study of the Fire Performance of Magnesium Hydroxide Sulfate Hydrate Whisker Flame Retardant Polyethylene

Summary: Halogen‐free, flame retardant low density polyethylene (LDPE) composites, using magnesium hydroxide sulfate hydrate (MHSH) whiskers as a flame retardant, combined with microencapsulated red phosphorous (MRP) as a synergist, have been prepared using a two‐roll mill. Their fire properties were determined by using the limiting oxygen index (LOI), the UL‐94 test and cone calorimetry. The results showed that MRP was a good synergist in improving the flame retardance of the LDPE/MHSH whisker system. Poly[ethylene‐co‐(vinyl acetate)] (EVA), used as a compatibilizer, increased the fire performance of LDPE/MHSH whisker composites.

HRR curves for LDPE/MHSH whisker composites.     

In‐Line Monitoring and Control of Conversion and Weight‐Average Molecular Weight of Polyurethanes in Solution Step‐Growth Polymerization Based on Near Infrared Spectroscopy and Torquemetry

Summary: It is well known that the weight‐average molecular weight ( ) is strictly dependent on conversion in step‐growth polymerizations performed in batch and that the is very sensitive to impurities and molar imbalance. This makes the work of controlling a non trivial job. In this paper a new methodology is introduced for in‐line monitoring and control of conversion and of polyurethanes produced in solution step‐growth polymerizations, based on near‐infrared spectroscopy (NIRS) and torquemetry. A calibration model based on the PLS method is obtained and validated for monomer conversion, while the weight‐average molecular weight is monitored indirectly with the relative shear signal provided by the agitator. Control procedures are then proposed and implemented experimentally to avoid gelation and allow for maximization of . The proposed monitoring and control procedures can also be applied to other step growth polymerizations.

Proposed control scheme.     

Silicone Liner‐Free Pressure‐Sensitive Adhesive Labels

Pressure‐sensitive adhesives (PSA) were microencapsulated using simple and complex coacervation and aminoplaste. The microcapsules thus prepared were characterized by FTIR spectroscopy, particle size distribution, rheological behavior, and peeling tests. The microcapsules were isolated and found to be out of sticky indicating that the PSAs were indeed encapsulated. The prepared suspensions were deposited at the surface of a paper sheets and the dried labels were then pressed against each other. The ensuing complex was then characterized in terms of peeling forces and showed that the encapsulation using aminoplaste technique of a commercial PSA yielded peel energy of 170 J · m^?2, which constitutes the recovering of about 68% of the adhesive power of the original nonencapsulated PSA.

     

Near Infrared Reflection Spectroscopy: A Versatile Tool for Rapid Characterization of Olefin Copolymers and High‐Throughput Experiments

Near infrared (NIR) spectroscopy was developed as a rapid analytical method for the determination of the composition of olefin copolymers obtained in high‐throughput screening. NIR spectra of ethene/propene and ethene/1‐hexene copolymers, also characterized by means of ¹³C NMR spectroscopy, were recorded and used to design multivariate calibration models. Different methods for the preprocessing of the spectra, including the linearization by non‐linear transformations, were compared. Optimal methods and error estimates were established using crossvalidation. This technique is of particular interest for the rapid on‐line analysis of high‐throughput experiments in the field of polymer and catalyst design employing methods from combinatorial chemistry.

Predicted versus true value of the propene incorporation and standard deviation for ethene/propene copolymers.     

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.     

Morphology,Electrical, and Rheological Properties of Silane‐Modified Silver Nanowire/Polymer Composites

Electrically conducting films containing AgNws, hydrophilic and hydrophobic resins were prepared. FT‐IR reveals that the interface between the AgNws and epoxy could be successfully modified by APTES. XPS shows that the AgNws were attracted by hydrogen bonds of ? NH₂ and ? NH? groups after APTES modification. SEM analysis shows that the AgNws were well dispersed in the resin. The AgNws were also blended with hydrophilic and acrylic resins, and the resulting blends were compared with AgNws/epoxy blends. Results show that AgNw/PVA‐resin films possess the lowest surface electrical resistance. The AgNw/PVA‐resin and silane‐modified AgNw/epoxy resin conductive films possess a similar electrical percolation threshold.