Poly(ethylene oxide)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] as Strengthening Agent in Paper: Dynamic Mechanical Characterization

To enhance adhesion properties of PEO on wood fibers, block polymers of PEO and 2‐(dimethylamino)ethyl methacrylate were synthesized. The polymers were further modified to obtain strongly cationic species. The resulting polymers were used as additives in paper sheets. Papers were studied by DMA in a controlled‐humidity chamber. Addition of the PEO block co‐polymers enhanced paper strength. The strength of the paper sheets was highest when polymer with molecular weight of 400 kg · mol^?1 was used as an additive. Highly cationic block co‐polymers increased moduli of paper sheets more than their weakly cationic analogs, which indicated strong interaction with fiber surfaces. Strength of the paper sheets decreased both with increased temperature and humidity.

     

An Approach to Calculating Wear on Annular Non‐Return Valves

The serviceability of non‐return valves has a major influence on the productivity of the injection molding process. During a meeting of experts held at our Institute, it was seen that closing behavior and wear are the key problems encountered in practice. The conducted investigations to tackle these questions have shown that both an improved closing behavior and a lower level of wear can be achieved by reducing the inside radius of the locking ring.

Pressure profile over the length of a non‐return valve (n = 0.4; = 25 000 mm³/s).     

Synthesis of Block Copolymers containing Chain‐Controlled Aramid and Fluoroethylene Segments

Summary: Novel block copolymers containing aromatic polyamide (aramid) and fluoroethylene segments were synthesized by a two‐step solution polycondensation. This synthetic method could control the chain‐length of aramid segments and these copolymers could have high structural regularity. The number‐average molecular weight ( ) of one of these polymers is over 2.0 × 10⁴. Incorporating fluoroethylene segments improves the solubility of the resulting polymer compared with conventional aramids.

The synthesis of the fluoroethylene‐aramid block copolymers.     

Brook/Elimination/Aldol Reaction Sequence for the Direct One‐Pot Preparation of Difluorinated Aldols from (Trifluoromethyl)trimethylsilane and Acylsilanes

A methodology allowing the one‐pot preparation of difluorinated aldols directly from Ruppert–Prakash reagent, acyltrimethylsilanes and aldehydes is reported. The process, initiated by a catalytic amount of an ammonium salt, involves the addition of (trifluoromethyl)trimethylsilane to the acylsilane, followed by a Brook rearrangement and elimination of a fluoride anion that promotes the subsequent aldol reaction. An efficient racemic reaction catalyzed by tetrabutylammonium difluorotriphenylsilicate is described, as well as our first efforts towards an asymmetric version.

     

Nylon 6‐Polyesteramide Block Copolymers (NBC) and NBC/Phenolic Resin Composites, 1

Summary: A series of NBC/phenolic resin composites, containing 0, 1, 3, 5 or 7 wt.‐% of a powdered phenolic resin of different particle diameter, was prepared by the reaction injection molding (RIM) process. It was determined by SEM analysis that there exists a strong interaction between particles and matrix and that such interaction occurs through hydrogen‐type bonds as determined by FTIR analysis. According to the results it is thought that the glass transition temperature of the NBC/phenolic resin composites depends on two competing factors: the rigidity promoted by the hard solid filler and the flexibility imparted by the nylon 6 amorphous phase, whose proportion becomes more important with increasing amounts of phenolic resin particles. The elastic and flexural moduli of the NBC were improved by the addition of phenolic resin confirming the reinforcing effect of this filler. On the contrary, the impact strength diminishes with increasing amounts of phenolic resin, although this property is strongly dependent on the particle diameter.

SEM micrograph of the nylon 6‐polyesteramide block copolymer (80/20).     

Structure and Properties of Compatible PPSF‐Rich Blends with PET

Summary: New PPSF/PET (poly(phenyl sulfone)/poly(ethylene terephthalate)) blends rich in PPSF were obtained by direct injection molding. Biphasic morphologies with a very large interface area/dispersed phase volume ratio were obtained and were attributed to a low interfacial tension in the melt state, a consequence of the reactions observed between the components of the blends. This favorable morphology led to small strain mechanical properties close or slightly above those predicted by the direct rule of mixtures, and more significantly, to elongations at break of the blends higher than that of the PPSF matrix.

Morphology of the cryogenically‐broken etched surface of a PPSF/PET 75/25 blend.     

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.     

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.     

Polyolefins with Long Chain Branches Made with Single‐Site Coordination Catalysts: A Review of Mathematical Modeling Techniques for Polymer Microstructure

Summary: Single‐site coordination polymerization catalysts are considered one of the most important developments on the technology of olefin polymerization during the last two decades. Among the several new capabilities of these catalysts is the ability to produce polymer molecules having narrow molecular weight distribution and long chain branches. These advances in polymer synthesis have stimulated the development of mathematical models to describe and predict several features of their molecular architectures. Many modeling techniques have been used for this purpose, including instantaneous distributions, population balances, the method of moments, and Monte Carlo simulations. This article reviews the mathematical models developed over the last decade to quantify the microstructure of polymers made with single‐site catalysts with special emphasis on the mechanism of long chain branch formation by terminal branching.

     

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.

     

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.

     

Preparation of Nano‐Polyethylene Fibers and Floccules by Extrusion Polymerization Under Atmospheric Pressure Using the SBA‐15‐Supported Cp2ZrCl2 Catalytic System

Summary: Nano‐polyethylene fibers and floccules were prepared under atmospheric pressure via ethylene extrusion polymerization in suit, using the SBA‐15‐supported Cp₂ZrCl₂ catalytic system. The major morphology units in the samples were fibers and floccules. The diameter of the single nano‐fibers was 120–200 nm. The single nano‐fibers could aggregate to form fiber aggregates and bundles. The number of PE floccules increased with extension of polymerization time, while the melting point of PE with nano‐fibers was little higher than that of common polyethylene.

SEM micrograph of the nano‐polyethylene fibers produced at a polymerization time of 60 min: micro‐fibers and floccule surface morphologies.     

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.

     

Flexible Use of Single‐Screw Extruders through Multiple‐Process Optimization

Using general‐purpose screws to process different types of material offers considerable cost advantages over special‐purpose screws. Designing screws of this type is generally a difficult task, since modifications to different aspects of the geometry can run counter to each other in some cases. Optimization software is thus of particular benefit here. For this reason, a program was developed for the optimization of general‐purpose screws. A central feature of this program is an appraisal system for the computer‐aided evaluation of single‐screw simulations. The performance of the software was verified on the basis of actual extrusion experiments.

Temperature measuring cross for measuring thermal homogeneity.     

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.

     

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.

     

Novel Poly(N‐isopropylacrylamide)‐graft‐poly(vinylidene fluoride) Copolymers for Temperature‐Sensitive Microfiltration Membranes

In the present work, we report on the synthesis and characterization of poly(vinylidene fluoride) (PVDF) with N‐isopropylacrylamide (NIPAAM) polymer side chains from molecular graft copolymerization in solution. The copolymer can be readily cast into temperature‐sensitive microfiltration (MF) membranes by the phase inversion technique. The copolymer approach to membrane fabrication allows a much better control of the physicochemical nature of the membrane pores through the variation in graft concentration, membrane casting temperature and concentration of the membrane casting solution.

     

The Solid State Postcondensation of PET, 2

Summary: A process for the solid state polycondensation of PET is proposed. It is shown that by correctly choosing the prepolymerisation conditions it is possible to crystallise the product and to directly polymerise it in a dispersed phase. This process is significantly faster than the “standard” PET processes, and allows one to obtain high molecular weights directly from a prepolymer without the need to use an intermediate solution polymerisation step.

Reactor set‐up for precursor preparation and dispersed phase prepolymerisation.     

Improvement of Chromatic Aberration of the Plastic Rod‐Lens Array, 2

Summary: We propose in this paper a new plastic rod‐lens with low chromatic aberration. Since a plastic rod‐lens has a parabolic refractive index distribution, it usually also shows a distribution of Abbe number. This Abbe number distribution is thought to cause the chromatic aberration of the plastic rod‐lens array. We have studied novel materials for a new plastic rod‐lens with low chromatic aberration and have provided new transparent polymer blends consisting of two polymers with different refractive indices and with almost equal Abbe numbers by using a fabrication process based on photopolymerization of methacrylate monomer(s) in the presence of other methacrylic polymers. The process can give new transparent polymer blends which cannot be formed using conventional techniques for polymer blend formation. In this work, tricyclo[5,2,1,0^2,6]deca‐8‐yl methacrylate is used as a high refractive index monomer and tert‐butyl methacrylate is used as a low refractive index one. By using polymer blends including these monomer units, we have created a plastic rod‐lens with lower chromatic aberration.

Molecular structures of comonomers in the study.     

Thermo‐Physical and Impact Properties of Epoxy Containing Epoxidized Linseed Oil, 2

Summary: Biobased neat epoxy materials containing epoxidized linseed oil (ELO) were processed with an amine curing agent. A defined amount of diglycidyl ether of bisphenol F (DGEBF) was replaced by ELO. The thermophysical properties of the amine‐cured biobased neat epoxy were measured by dynamic mechanical analysis (DMA). The Izod impact strength increased with an increase in the amount of ELO added. The change in the Izod impact strength was correlated with the thermophysical properties measured by DMA.

Relation between the Izod impact strength and loss factor for amine‐ and anhydride‐cured ELO‐containing epoxy resins.