Elaboration of Poly(ε‐caprolactone)‐g‐TiNbO5 Nanocomposites via in situ Metal Complex Initiated Intercalative Polymerization

Summary: The preparation of poly(ε‐caprolactone)‐g‐TiNbO₅ nanocomposites via in situ intercalative polymerization of ε‐caprolactone initiated by an aluminium complex is described. These nanocomposites were obtained in the presence of HTiNbO₅ mineral pre‐treated by AlMe₃, but non‐modified by tetraalkylammonium cations. These hybrid materials obtained have been characterized by Fourier transform infrared absorption spectroscopy, wide‐angle X‐ray scattering, scanning electron microscopy, and dynamic mechanical analysis. Layered structure delamination and homogeneous distribution of mineral lamellae in the poly(ε‐caprolactone) (PCL) is figured out and strong improvement of the mechanical properties achieved. The storage modulus of the nanocomposites is enhanced as compared to pure PCL and increases monotonously with the amount of the filler in the range 3 to 10 wt.‐%.

SEM image of the fractured surface of a PCL‐TiNbO₅ nanocomposite film.     

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.     

Investigation Into Poly(propylene)/Montmorillonite/Calcium Carbonate Nanocomposites

Summary: A novel method was used to prepare poly(propylene)/montmorillonite/calcium carbonate nanocomposites by melt‐mixing, using pristine montmorillonite (MMT), hexadecyltrimethylammonium bromide (C16), calcium carbonate (CaCO₃) and a matrix in a twin‐screw extruder. Two different sizes of calcium carbonate were used (nanosized CaCO₃ and micron‐sized CaCO₃, the average sizes being 60 nm and 12 μm respectively). The nanocomposite structure was evidenced using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electronic microscopy (HREM). Tensile tests and Izod notch impact tests suggested that the incorporation of nanosized CaCO₃ into PP/montmorillonite nanocomposites increased the mechanical properties of the composites, but the improvement in the micro‐sized CaCO₃‐filled PP/montmorillonite nanocomposites was found to be minimal. The thermal stability and flammability properties were characterized by thermogravimetric analysis (TGA) and a cone calorimeter respectively.

     

The Influence of Calcium‐Stearate‐Coated Calcium Carbonate and Talc on the Quiescent and Flow‐Induced Crystallization of Isotactic Poly(propylene)

The influence of Ca‐stearate‐coated CaCO₃ and talc on the quiescent and flow‐induced crystallization of iPP is studied using different methods. Comparison of rheometry and DSC shows that rheometry is an interesting tool to monitor crystallization kinetics. It is observed that the Ca‐stearate coating degrades at commonly used annealing temperatures, influencing the crystallization behavior of the CaCO₃‐containing polymer. WAXD indicates that the CaCO₃ does not significantly influence the degree of crystallinity. As shear intensifies, both the pure and particle‐containing polymers crystallize faster; however, their behavior also becomes increasingly similar. There are indications that shear influences the organization of the CaCO₃ aggregates.

     

Comparative Characterization of PP Nano‐ and Microcomposites by In‐Mold Shrinkage Measurements and Structural Characteristics

Poly(propylene)‐clay nanocomposites and poly(propylene) containing conventional inorganic fillers such as calcium carbonate (CaCO₃) and glass fiber were used in a comparative study focusing on dimensional stability, structure, mechanical and thermal properties. Micro‐ and nanocomposites were prepared by melt blending in a twin‐screw extruder. The relative influence of each filler was observed from dimensional stability measurements and structural analysis by WAXD, TEM, and thermal and mechanical properties. At equal filler loadings, PP/clay nanocomposites exhibit an improvement in dimensional stability and were the only composites capable of reduced shrinkage in both in‐flow and cross‐flow directions. The flexural modulus of PP increased nearly 20% by compounding with 4% organoclay, as compared to a similar performance obtained by compounding with 10 wt.‐% of CaCO₃ or approximately 6 wt.‐% of glass fiber. The HDT and thermal stability of PP were enhanced by using nanoclay as filler.

     

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.     

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).     

Telomerization of Butyl Methacrylate and 1‐Octadecanethiol by Reactive Extrusion

Butyl methacrylate and 1‐octadecanethiol telomers were prepared by radical reactive extrusion. The main advantages of the use of this processing technique are that mass reactions can be conducted and continuous production is achieved within a reduced reaction time and a correct temperature control. Preliminary studies concerned the choice of the reactants for the telomerization reaction and the adaptation of the telomerization reaction to the reactive extrusion process. The transfer constant to C₁₈H₃₇SH was measured, and then experimental studies were conducted to verify that the hypothesis and approximations made for kinetic modeling are realistic. Particularly, it was shown that the use of relatively high chain‐transfer agent to monomer concentration ratio had no perceptible effect on the monomer conversion kinetic. These results allowed the choice of reactive extrusion conditions. Telomers were prepared using a laboratory co‐rotating twin‐screw extruder. The effect of reaction conditions (temperature, 1‐octadecanethiol to monomer concentration ratio) and of processing conditions (throughput, screw rotation speed) on the residence time distributions, molar mass and monomer conversions were examined. This study allowed the continuous synthesis of butyl methacrylate telomers having variable controlled molar masses and complete monomer conversion.

Screw profile used in reactive extrusion telomerization.     

Thermo‐Mechanical Degradation of LDPE‐Based Nanocomposites

Thermo‐mechanical degradation of LDPE‐based nanocomposites was studied by mainly investigating the rheological properties. For all of the investigated processing conditions, the viscosity of the nanocomposites was higher than that of the pure‐LDPE matrix, but on increasing the severity of the mixing conditions, the difference between the viscosity of the nano‐filled polymer and that of the pure LDPE decreased. The X‐ray traces of the nanocomposites suggest that intercalation has been achieved during the melt, when less‐severe processing conditions were used. At severe processing conditions (longer mixing time, high temperature and shear stress) the thermo‐mechanical degradation was accelerated, possibly due to the loss of mass from the organoclay galleries. The variations of the viscosity in the presence of two organo‐modified montmorillonite (MMt) clays were compared to the ones observed with a MMt clay at different processing conditions.

     

Colloidal Crystalline Arrays of β‐Polymorphic Poly(vinylidene fluoride)

Stable layers of nearly monodisperse spheres of β‐polymorphic poly(vinylidene fluoride) with iridescent properties are prepared. The colloidal crystalline arrays (CCAs) were characterized by optical microscopy, differential scanning calorimetry (DSC), and FT‐IR spectroscopy. FT‐IR spectroscopic and wide‐angle X‐ray scattering (WAXS) studies revealed a β‐polymorphic PVF₂ structure, the DSC study showed that the level of crystallinity in the CCA was much higher than that in the melt‐crystallized sample, and UV‐visible spectroscopy showed extinction peaks at 323 and 510 nm in the CCAs. The β‐polymorphic PVF₂ structure, along with the optical extinction properties of these CCAs, raises the prospect of their application in optical filters and/or piezoelectric sensors.

Optical micrograph of PVF₂ CCA films cast on glass substrates.     

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.

     

Mechanical and Thermal Properties of Poly(L‐lactide) Incorporating Various Inorganic Fillers with Particle and Whisker Shapes

Poly(L ‐lactide) (PLLA) composites incorporating various inorganic fillers (ifR‐PLA) were prepared by the melt blending technique, and their mechanical and thermal properties were evaluated. The filler types influenced the mechanical properties of ifR‐PLA; for those incorporating particle‐ and whisker‐type fillers the tensile moduli were 3.1–3.7 and 3.7–4.5 GPa, respectively, and the flexural moduli were 4.1–4.8 and 4.8–6.1 GPa. It was found that the tensile strength and modulus, as well as the flexural modulus, of ifR‐PLA incorporating whisker‐type fillers increased in proportion to the volume percent of the fillers (V_f). The flexural strength of ifR‐PLA incorporating 9Al₂O₃ · 2B₂O₃ whiskers showed a similar increase, while that of ifR‐PLA incorporating CaCO₃ whiskers showed a decrease with increasing V_f. This difference may be because the 9Al₂O₃ · 2B₂O₃ with its large aspect ratio kept its original fibrous shape, while the CaCO₃ lost its fibrous shape during the blending process. However, the reinforcing effect of these fillers was relatively low compared with that known for the corresponding composites of the conventional polymeric materials, probably because of the poor surface adhesion of PLLA to the fillers.

Comparison of effect on storage moduli of different fillers.     

Temperature Sensitive Behavior of Poly(N‐isopropylacrylamide) Grafted Onto Electron Beam‐Irradiated Poly(propylene)

Summary: N‐Isopropylacrylamide (NIPAAm) was graft‐polymerized from its acetone solution onto poly(propylene) (PP) films, after electron‐beam irradiation in the presence of air oxygen. The effects of pre‐irradiation dose as well as monomer concentration, reaction temperature and reaction time on the grafting efficiency were investigated. Typical conditions for achieving maximum grafting yield were observed for 1 M monomer concentration, after PP pre‐irradiation with a 300 kGy dose and a reaction temperature of 50 °C. The location of the graft polymerization was examined by different methods including measurements of dimensional variations, calorimetry, SEM and AFM. The temperature‐responsive behavior of grafted copolymer was studied by swelling and contact angle measurements at different temperatures.

Temperature dependence of the swelling ratio in water as a function of temperature.     

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.     

Co(acac)2‐Mediated Radical Polymerization of Acrylonitrile: Control Over Molecular Weights and Copolymerization With Methyl Methacrylate

The cobalt‐mediated radical polymerization of acrylonitrile in DMSO using cobalt (II) acetylacetonate [Co(acac)₂] as mediator is studied. Both the evolution of molecular weight and conversion over time under various conditions are monitored. Molecular weights increase sharply at the beginning of the reaction and subsequently grow linearly with conversion. No branching of the polymer is observed by ¹³C NMR. By a careful design of the reaction parameters, number‐average molecular weights >1.2 · 10⁵ g · mol^?1 with a PDI around 2.4 together with conversions of up to 90% within 24 h are achieved. The copolymerization parameters of acrylonitrile with methyl methacrylate in DMSO at 30 °C are determined using the Kelen‐Tüdõs approach giving r_AN = 0.33, r_MMA = 0.71.

     

Monodisperse Silica‐Polymer Core‐Shell Microspheres via Surface Grafting and Emulsion Polymerization

We describe a flexible method for preparing monodisperse silica‐polystyrene core‐shell microspheres. In this method, silica nanoparticles grafted with 3‐(trimethoxysilyl)propyl methacrylate (MPS) were employed as seeds in an emulsion polymerization. The thickness of the shells could be changed through varying the amount of the monomer. The monodispersity and diameters of the core‐shell microspheres were found to depend on the size of the grafted silica nanoparticles and the concentration of emulsifier. In addition, we investigated the formation mechanism of the core‐shell microspheres.

Schematic outline of the experimental procedure and TEM image of the monodisperse silica/PS core‐shell microspheres; inset: grafted silica nanoparticles (scale bar = 200 nm).     

1,8‐Naphthalimides as Blue Emitting Fluorophores for Polymer Materials

The copolymerization of 1,8‐naphthalimide derivatives (as fluorophore) with acrylonitrile has been investigated. The photophysical characteristics of monomeric and polymeric fluorophores in N,N‐dimethylformamide solution have been determined and discussed. During copolymerization, no changes in the chromophoric systems of the fluorophore occur. The influence of the studied monomeric 1,8‐naphthalimide fluorophores upon the structurally bleached polyacrylonitrile has been determined. Infrared absorption characteristics of the polymerizable 4‐alkoxy‐ and 4‐allyloxy‐N‐substituted‐1,8‐naphthalimides have been measured and discussed. The effect of the substituents upon the vibration frequencies of the carbonyl and allylic groups has been established.

Blue fluorescent polyacrylonitrile copolymers with 1,8‐naphthalimides side‐group.     

Ternary Poly(styrene‐co‐acrylonitrile)/Poly(vinyl chloride) Blend Composites with Multi‐Walled Carbon Nanotubes and Enhanced Physical Characteristics

We report a ternary system of poly(styrene‐co‐acrylonitrile) (SAN), poly(vinyl chloride) (PVC), and multi‐walled carbon nanotube (MWCNT) composites prepared by both a solution blending method and the SOAM. The MWCNT content in the composites was optimized by both TGA and mechanical characterization of binary mixtures of SAN/MWCNT and PVC/MWCNT composites. The dispersion of MWCNTs in the miscible SAN/PVC blends was characterized by FT‐Raman spectroscopy, FE‐SEM, and FE‐TEM. The distribution of MWCNTs in the SAN/PVC blends was examined in terms of their wetting coefficients and minimization of the interfacial energy. Composites prepared using the SOAM method showed superior physical properties to the SAN/PVC blends and SAN/PVC/MWCNT composites prepared using the solution blending method.

     

Dextrin‐ and Conducting‐Polymer‐Containing Biocomposites: Properties and Behavior as Cellular Matrix

Both α‐cyclodextrin and linear dextrin are used to prepare biocomposites with poly(3,4‐ethylenedioxythiophene). Materials are prepared electrochemically in aqueous solution. Comparison with the pure polymer indicates that the electroactivity and electrostability decrease with the incorporation of the dextrins while the electrical conductivity is retained. The different properties of the two biocomposites suggest that the linear dextrin is mainly located at the surface, whereas the cyclodextrin is homogeneously distributed in the polymeric matrix. Cell adhesion and proliferation assays indicate that the cellular activity is significantly higher in the dextrin‐containing biocomposites.

     

Scale‐Up in the Design of Extrusion Dies

The similarity theory and the scale‐up procedure developed from it make it possible to convert a technical‐physical process from one scale to another – generally in the upwards direction. In the design of extrusion dies with an annular die gap, the die is broken down into basic geometric elements, and scale‐up rules are then drawn up for the individual elements. In this project, scale‐up rules were found that satisfy both full and partial similarity. The pseudoplasticity and elasticity of the melt were also taken into consideration. A comparison of the model laws obtained with the results of finite element calculations showed good conformity between the models and the production versions.

Deviation in pressure difference between the model and the production version assuming flow behavior in accordance with the power law (D_i = const. and L = const.).