Fluorinated Hyperbranched Polymers as Additives in Cationic Photopolymerization

Summary: Different fluorinated hyperbranched polymers (HBP) were synthesized starting from fluorinated oxetanes and employed as additives in cationic photopolymerization of epoxy monomers. As previously observed for other hydroxyl containing HBP, they interact with the polymeric carbocation through a chain transfer mechanism inducing an increase in the final epoxy conversion. High gel content values (>96%) for the photocured films confirm that the HBP additive is tightly crosslinked to the polymeric network. In the presence of this fluorine‐containing HBP it is possible to influence the bulk properties, as well as, the surface properties. The fluorinated HBP tends to migrate to the surface inducing an increase of hydrophobicity.

The hyperbranched polymer used in this work.     

Synthesis and Characterization of Hyperbranched Poly(β‐ketoester) by the Michael Addition

Summary: A novel hyperbranched poly(β‐ketoester) was synthesized from 2‐(acetoacetoxy)ethyl acrylate by the Michael addition in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as catalyst. ¹H NMR integration experiments revealed that the degree of branching in the poly(β‐ketoester) was remarkably high at a level of 82.9%. The number‐average molecular weight of the polymer was between 2 100 and 12 000 and increased with reaction temperature and conversion.

Synthesis of hyperbranched polymer by Michael addition of AAEA.     

Crystalline and Conductive Poly(3‐hexylthiophene) Fibers

Intrinsically conducting polymer fibers are prepared from P3HT by melt spinning. High crystallinity is achieved by drawing the fibers after the spinning process, applying a draw ratio of 1:2. DSC and XRD measurements confirm the continuous increase of crystalline phases with drawing. For comparison, poly(ethylene terephthalate) fibers are coated with P3HT and drawn as well. Again, the drawing of the coated fiber results in a significant increase in crystallinity of the P3HT coating. The high amount of crystalline phases is associated with a dramatic increase in conductivity (350 S · cm^?1) after doping with FeCl₃ in nitromethane.

     

Artificial Neural Networks Associated to Calorimetric Measurements Used as a Method to Predict Polymer Composition of High Solid Content Emulsion Copolymerizations

Summary: Inspired by biological systems, artificial neural networks (ANN) have demonstrated to be powerful tools to model non‐linear systems, such as high solid content latexes produced by emulsion polymerization which have a great importance in the polymeric industry, essentially for environmental reasons, since they usually have water as a continuous phase. The quality of the produced polymer is closely related to the structure of the polymeric chain. In order to propose technical and economically feasible alternatives to control a polymeric structure, this work is aimed to develop a new methodology based on ANN associated with calorimetry to predict the polymeric structure. The designed ANN presented excellent results when tested with process condition variations (such as temperature and reaction time) as well as when they were submitted to test concerning the variation on the proportion of monomers in the latex formulation. Hence, it was possible to conclude that ANN, associated to calorimetry, lead to an efficient method to predict the polymer composition in emulsion copolymerizations.

     

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).     

Artificial Opals as Effect Pigments in Clear‐Coatings

Summary: In this paper, we describe the use of artificial opals from polymer beads as effect pigments in transparent industrial and automotive coatings. For this purpose, we synthesized monodisperse colloids from fluorinated methacrylates by surfactant‐free emulsion polymerization. The fluorinated monomers, in combination with crosslinking, lead to a refractive index contrast, thermal stability, and solvent resistivity necessary for use as effect pigments. After crystallization of the monodisperse polymer beads, crystal flakes with iridescent colors can be obtained. The crystal flakes can act as effect pigments in various transparent industrial and automotive coatings. Due to photonic crystal behavior of effect pigments, color flops up to 100 nm are observed.

Crystal flakes of CS ‐7 as effect pigments in a transparent coating. The diameter of the tube is 5 mm.     

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.

     

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 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.

     

Polyurethane Foams of Improved Thermal Stability

In reactions of polyetherols prepared from hydroxymethyl derivatives of uric acid and typical oxiranes with isocyanates and water one obtains a new group of polyurethane foams containing purine rings in their structure. These polyurethanes withstand prolonged heating at temperatures as high as 200 °C. Preliminary results on the effect of the type of polyetherol and the composition used in preparation of the polyurethane foams on their properties are presented. The results of studies on thermal stability and mechanical properties of the foams before and after thermal treatment are also reported.

     

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.     

Preparation and Characterization of Polycarbonate/Poly(propylene)/Attapulgite Ternary Nanocomposites with the Morphology of Encapsulation

Summary: Ternary nanocomposites based on polycarbonate (PC), poly(propylene) (PP), and attapulgite (AT) were prepared via the method of two‐step melt blending, by which the AT was blended with PP prior to compound with PC. Structure and properties of the ternary PC/PP/AT nanocomposites were investigated. The degradation of PC triggered by AT during direct blending process can be inhibited effectively by using two‐step melt blending. It was found that the morphology of encapsulation structure like sandbag was formed in PC matrix, where PP encapsulated AT fibrillar single crystals. DSC experiments showed that in PC/PP/AT ternary nanocomposites, AT had a strong heterophase nucleation effect on PP, resulting in the enhancement of crystallization degree and the crystallization temperature of PP. DMA and mechanical property results showed that the ternary nanocomposites exhibited good balanced toughness and stiffness.

TEM photograph of PC/PP/AT ternary nanocomposite.     

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.     

Inhomogeneity Effects in Vapor Phase Polymerized PEDOT: A Tool to Influence Conductivity

Low‐MW urethanes were investigated to control domain formation as well as inhibiting cleavage reactions during vapor phase polymerization of PEDOT. A diurethanediol (DUDO) was identified as a highly efficient mediator for the process, resulting in PEDOT films exceeding conductivities of 1 000 S · cm^?1. All the urethanes investigated had the desired inhibiting effect on the polymerization, but all apart from DUDO also introduced unwanted domain formation on the micrometer scale. The addition of PEG generally improved conductivity by suppressing the domain formation and, with an optimized combination of DUDO and PEG, conductivities over 1 200 S · cm^?1 were achieved.

     

Analysis of the Influence of Rotor Design on the Stream Flow Conditions Within an Internal Mixer

A flow visualisation apparatus is described which allows to compare different rotor designs to each other. In order to observe the distributive mixing effect, the stream flow and dispersive mixing effect is monitored by an indirect measurement of the power impact within the material. Assuming that the mixing process of an internal mixer is not continuous, a testing device was build to the scale of a 90 l kneader. In this device the mixing chamber and the rotor blade are unwound into the flat plane. With this testing device it is possible to carry out a systematic analysis of the influence of rotor design on the flow processes within an internal mixer in a fast and inexpensive way.

The test device.     

Synergistic Effect of the Charring Agent on the Thermal and Flame Retardant Properties of Polyethylene

Summary: A new charring agent (CA), a derivative of triazines, was synthesized. The flame retardancy and thermal behavior of a new intumescent flame‐retardant (IFR) system for PE (PE‐IFR) were investigated by limited oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and FTIR spectroscopy. The TG curves shows that the amount of residue of IFR‐PE system are largely increased compared to those of PE at temperatures ranging from 350 to 700 °C. The new PE‐IFR system can apparently reduce the amount of decomposing products at higher temperatures and promotes the formation of carbonaceous charred layers. It showed a distinct synergistic flame retardant effect (SE) between nitrogen and phosphorus. The flame retardant PE composition was optimized to achieve a LOI value of 31.2 and UL‐94 V‐0 performance with the synthesized charring agent, ammonium polyphosphate (APP).

TG curves of PE, APP, CA, and different PE/CA/APP systems.     

The Effect of Particle Matrix Adhesion on the Mechanical Properties of Silica Filled Cyanate Ester Composites

Summary: The effect of silica and its surface treatment on the mechanical properties of composites was studied as part of the evaluation of cyanate ester matrices as potential electronic encapsulants. Three filler surface treatments were used, as a qualitative interfacial adhesion scale, in an attempt to gauge the magnitude of interfacial adhesion between untreated filler and the cyanate ester matrix. There was strong interfacial adhesion between matrix and untreated filler. The level of silica content most affected composite modulus and fracture toughness. Filler surface treatment most affected composite strength and fracture toughness/energy. Composite fracture was found to occur via crack pinning and/or crack blunting depending on the strength of adhesion. The composites evaluated were found to possess suitable mechanical properties for potential use as electronic encapsulants.

     

Thermal Imidization of the Precursor of a Liquid Crystalline Polyimide

Imidization of the precursor of a liquid crystalline polyimide was investigated using modulated differential scanning calorimetry (MDSC), Fourier transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analyzer (TGA) coupled to FTIR (TG‐IR). The FTIR study revealed that the rate and degree of imidization are functions of curing temperature and time. Imidization proceeds in two stages under isothermal condition. The initial weight loss up to 250 °C as observed from TGA was due to thermal cyclization, i.e., imidization process. The XPS analysis shows that the poly(amic acid) has two nitrogen 1s species at 400.3 and 399.2 eV possibly due to the isomerism of the dianhydride carbonyl, while liquid crystalline polyimide shows only a single nitrogen 1s species at 400.8 eV due to imide species.

PLM micrograph of PAA (at 280 °C) after imidization.     

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.     

Synthesis of Alkyl‐Functionalized Hyperbranched Polymers and Their Use as Additives in Cationic Photopolymerization of Epoxy Resins

Summary: An alkyl‐functionalized hyperbranched polymer, HBP(OH)–C16, was synthesized by partial modification with fatty acid of an aromatic‐aliphatic OH‐terminated hyperbranched polyester HBP? OH. This product was used as additive in the cationic photopolymerization of an epoxy resin. The alkyl‐modified polyester takes part in the photopolymerization process thanks to the residual OH groups by means of chain‐transfer reactions. An increase of the epoxy conversion is observed by increasing the amount of the HBP additive in the photocurable resin with a modification of the bulk properties of the final ultraviolet‐cured films. The presence of HBP(OH)–C16 induces an increase in glass transition temperature, thermal stability, and solvent resistance. Moreover the surface properties of the films are modified achieving highly hydrophobic surfaces in the presence of even very low amounts of HBP(OH)–C16.

Structure of HBP–C16.