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The crystallization behavior of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) filled with different amount of multi-walled carbon nanotubes (MWCNT) has been experimentally determined in the entire temperature range between glass transition and melting temperature. Differential fast scanning chip calorimetry, realizing cooling and heating rates of several 1 000 K · s−1, have been applied under isothermal and non-isothermal conditions. The MWCNTs act as heterogeneous nuclei for both polymers. Increasing filler content speeds up crystallization at low supercooling, where heterogeneous nucleation dominates, for more than one order of magnitude. At high supercooling (crystallization temperature below 120 °C for PET and 70 °C for PBT) crystallization kinetics is independent on MWCNT concentration. Here crystallization via homogeneous nucleation is always determining the overall crystallization kinetics and addition of nucleating agents is not effective anymore. Depending on the processing conditions these observations may be important for structure formation in PET and PBT composites. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate)/silica (PMMA/SiO x) nanocomposites were synthesized via sol-gel method and studied by various techniques. The dispersion of the silica particles (10-100 nm) in the matrix was probed by transmission electron microscopy (TEM), while solid-state NMR and Raman spectroscopy detected the formation of an inorganic network with high degree of crosslinking. To elucidate the impact of the filler on the molecular dynamics of the PMMA, different methods were used; namely differential scanning calorimetry, thermally stimulated depolarization current and broadband dielectric relaxation spectroscopy. All three methods observed a significant impact of the nanoparticles on the segmental dynamics of the matrix, which was expressed as an increase of the glass transition temperature ( Tg) in terms of calorimetry and as a shift of the α (segmental) relaxation to lower frequencies in terms of dielectric spectroscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Flame retarded poly(butylene terephthalate) (PBT) is required for electronic applications and is mostly achieved by low molar mass additives so far. Three phosphorus-containing polyesters are suggested as halogen-free and polymeric flame retardants for PBT. Flame retardancy was achieved according to cone calorimeter experiments showing that the peak heat release rate and total heat evolved were reduced because of flame inhibition and condensed-phase activity. The presented polymers containing derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide form immiscible blend systems with PBT. Shear-rheology shows an increase in storage moduli at low frequencies. This is proposed as quantitative measure for the degree of phase interaction. The phase structure of the blends depends on the chemical structure of the phosphorus polyester and was quite different, depending also on the viscosity ratio between matrix and second phase. A lower viscosity ratio leads to two types of phases with spherical and additionally continuous droplets. Addition of the flame retardants showed no influence on the dielectric properties but on the mechanical behavior. The polymeric flame retardants significantly diminish the impact strength because of several reasons: (1) high brittleness of the phosphorus polyesters themselves, (2) thermodynamic immiscibility, and (3) weak phase adhesion. By adding a copolymer consisting of the two base polymers to the blend, an improvement of impact strength was obtained. The copolymer particularly acts as compatibilizer between the phases and therefore leads to a smaller phase size and to a stronger phase adhesion due to the formation of fibrils. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A series of diblock copolymers of n-pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl-functionalized initiator and/or and end-capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature-dependent small-angle X-ray measurements (T-SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d-spacings L0 as well as in the thermal expansion behavior. T-SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order-disorder transition (ODT) until 300 °C. While non-functionalized BCP formed parallel lamellae morphologies, additional OH-termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d-spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing-incidence small-angle X-ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in-situ sol-gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

As a method of compatibilization of immiscible polyether ether ketone (PEEK)/polysulfone (PSU) blends, the addition of segmented PEEK/PSU block copolymers based on amorphous bisphenol A-containing PEEK was studied. This approach was evaluated for blends consisting of PEEK and PSU homopolymers with different molecular weights and different amounts of compatibilizers (segmented PEEK/PSU block copolymers and reactive end-functionalized PEEK and PSU oligomers). The compatibilizers were added under varying melt-processing conditions and effectively allowed the homopolymers to interact with the segmented block copolymers in the blend. The influence of the compatibilizers on the phase behavior was examined in both binary and ternary blends. Interactions in the amorphous phase, which effectively induce an enhancement of the toughness properties of the final product, could be detected. [ABSTRACT FROM AUTHOR]

• Novel trivalent phosphine containing poly(arylene ether)s are reported. • The maximum content of phosphine units is achieved by melt polycondensation. • The polymers are applied as polymer-immobilized catalysts. • Catalytic efficiency in a Mitsunobu etherification reaction is demonstrated. Novel phosphine containing poly(arylene ether)s with trivalent phosphorus are prepared by reaction of bis(4-fluorophenyl) phenylphosphine with 2,2-bis(4-hydroxyphenyl)propane. The reaction conditions are adjusted to avoid partial oxidation of the phosphine derivative during polycondensation. Solution polycondensation results in copolymers with phosphine and phosphorus oxide containing repeating units with high molar contents of phosphine oxide (up to 45 mol% P = O repeating units), while solvent-free melt polycondensation of bis(4-fluorophenyl) phenylphosphine with bis(trimethylsilyl)-2,2-bis(4-oxyphenyl)propane and CsF as catalyst yields 85 mol% phosphine containing repeating units. The weight-averaged molar masses are in the range of 40,000 g/mol. The phosphine containing polymers are used, to illustrate an example, as polymeric reagent in the Mitsunobu reaction for the etherification of 5-hydroxyisophthalic acid dimethylester with henicosaperfluoroicosanol to yield a monomer for semifluorinated polyesters. The Mitsunobu reaction requires triaryl phosphine derivatives as reactants which are oxidized to phosphorus(V) compounds during the course of the reaction. The separation of the oxidized products in the reaction with triphenyl phosphine (TPP) is generally complicated and the application of the novel poly(aryl ether)s results in simplification of the work-up and increase of the yield of the desired product (33% with TPP vs. 55% with the phosphine containing poly(aryl ether) P13). Thus, the applicability of the polymers as polymer-supported phosphine derivatives replacing low molar mass phosphines is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, the role of trimerization in polyisocyanurate (PIR) foams and its impact on the physical properties and the fire behavior is discussed. The degree of trimerization was systematically varied using different catalyst concentrations. The enhanced formation of isocyanurate structures through higher catalyst concentrations leads to higher mechanical stability and improved fire behavior as measured by vertical flame spread according to DIN4102 and under forced flaming conditions in the cone calorimeter. A clear correlation between catalyst content, chemical structure of the foams (relative concentration of isocyanurate units representing crosslinking) and fire behavior is found. • A variety of halogen free, phosphorus-containing PIR foams with different amounts of catalyst was successfully prepared. • The influence of catalyst concentration on isocyanurate content, foam properties, and flame-retarding properties was verified. • Higher catalyst contents yielded higher isocyanurate contents and caused higher compression strength. • Higher isocyanurate contents in these foams yielded better flame retarding properties. [ABSTRACT FROM AUTHOR]

A series of new flame retardants (FR) based on dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO) incorporating acrylates and benzoquinone were developed previously. In this study, we examine the fire behavior of the new flame retardants in polyisocyanurate (PIR) foams. The foam characteristics, thermal decomposition, and fire behavior are investigated. The fire properties of the foams containing BPPO-based derivatives were found to depend on the chemical structure of the substituents. We also compare our results to state-of-the-art non-halogenated FR such as triphenylphosphate and chemically similar phosphinate, i.e. 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO), based derivatives to discuss the role of the phosphorus oxidation state. [ABSTRACT FROM AUTHOR]

State-of-the-art Li batteries suffer from serious safety hazards caused by the reactivity of lithium and the flammable nature of liquid electrolytes. This work develops highly efficient solid-state electrolytes consisting of imidazolium-containing polyionic liquids (PILs) and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI). By employing PIL/LiTFSI electrolyte membranes blended with poly(propylene carbonate) (PPC), we addressed the problem of combining ionic conductivity and mechanical properties in one material. It was found that PPC acts as a mechanically reinforcing component that does not reduce but even enhances the ionic conductivity. While pure PILs are liquids, the tricomponent PPC/PIL/LiTFSI blends are rubber-like materials with a Young's modulus in the range of 100 MPa. The high mechanical strength of the material enables fabrication of mechanically robust free-standing membranes. The tricomponent PPC/PIL/LiTFSI membranes have an ionic conductivity of 10−6 S·cm−1 at room temperature, exhibiting conductivity that is two orders of magnitude greater than bicomponent PPC/LiTFSI membranes. At 60 °C, the conductivity of PPC/PIL/LiTFSI membranes increases to 10−5 S·cm−1 and further increases to 10−3 S·cm−1 in the presence of plasticizers. Cyclic voltammetry measurements reveal good electrochemical stability of the tricomponent PIL/PPC/LiTFSI membrane that potentially ranges from 0 to 4.5 V vs. Li/Li+. The mechanically reinforced membranes developed in this work are promising electrolytes for potential applications in solid-state batteries. [ABSTRACT FROM AUTHOR]

The effects of covalently bound phosphorus (P-) and nitrogen (N-) bearing groups on the thermal and combustion attributes of polystyrene have been investigated. The necessary chemical modifications were achieved through co- and ter-polymerisation reactions, in a suitable solvent, under radical initiation conditions. The influence of P–N cooperative interactions on the combustion properties of styrenic polymers was studied. The co-monomers of interest included: diethyl(acryloyloxymethyl)phosphonate (DEAMP), diethyl-p-vinylbenzylphosphonate (DEpVBP), acrylic acid-2-[(diethoxyphosphoryl)methyl amino]ethyl ester (ADEPMAE) and maleimide (MI). For the first time, the ter-polymers of styrene containing both P- groups, DEAMP or DEpVBP, and N- groups, MI, were prepared via solution polymerisation. It was found that the thermal stability and combustion characteristics of polystyrene were significantly altered by the presence of nominal amounts of P- and N- containing groups, and, in certain cases, cooperative interactions of these groups were also evident. For instance, the extents of char formation post-degradation of the prepared ter-polymers, as revealed by thermogravimetric investigations in an inert atmosphere (nitrogen), were found to be enhanced by more than 20%, as compared to the unmodified polystyrene. The heat release rates and heat release capacities of the ter-polymers, as measured using the pyrolysis combustion flow calorimetric (PCFC) technique, were reduced by almost 50% in comparison to the same parameters obtained for the unmodified counterpart. [ABSTRACT FROM AUTHOR]

Polystyrene (PS) was modified by covalently binding P-, P-N- and/or N- containing fire-retardant moieties through co- or ter-polymerization reactions of styrene with diethyl(acryloyloxymethyl)phosphonate (DEAMP), diethyl-p-vinylbenzyl phosphonate (DEpVBP), acrylic acid-2-[(diethoxyphosphoryl)methylamino]ethyl ester (ADEPMAE) and maleimide (MI). In the present study, the condensed-phase and the gaseous-phase activities of the abovementioned fire retardants within the prepared co- and ter-polymers were evaluated for the first time. Pyrolysis–Gas Chromatography/Mass Spectrometry was employed to identify the volatile products formed during the thermal decomposition of the modified polymers. Benzaldehyde, α-methylstyrene, acetophenone, triethyl phosphate and styrene (monomer, dimer and trimer) were detected in the gaseous phase following the thermal cracking of fire-retardant groups and through main chain scissions. In the case of PS modified with ADEPMAE, the evolution of pyrolysis gases was suppressed by possible inhibitory actions of triethyl phosphate in the gaseous phase. The reactive modification of PS by simultaneously incorporating P- (DEAMP or DEpVBP) and N- (MI) monomeric units, in the chains of ter-polymers, resulted in a predominantly condensed-phase mode of action owing to synergistic P and N interactions. The solid-state 31P NMR spectroscopy, Scanning Electron Microscopy/Energy Dispersive Spectroscopy, Inductively-Coupled Plasma/Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy of char residues, obtained from ter-polymers, confirmed the retention of the phosphorus species in their structures. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid coatings on glass substrates with superhydrophobic properties and with improved scratch resistance were obtained by means of applying a multilayer approach including multiple sol–gel processes. The coatings exhibited a water contact angle (WCA) higher than 150°. Ultraviolet (UV)-curable vinyl ester resins and vinyltriethoxysilane (VTEOS) as coupling agent were employed to increase the adhesion between substrate and the inorganic layers. The surfaces were characterized by means of dynamic contact angle and roughness measurements. Indeed, the occurrence of superhydrophobic behavior was observed. The scratch resistance of the hybrid coatings was tested to evaluate the adhesion of the coatings to the glass substrate. The proposed preparation method for scratch resistant, mechanically stable, superhydrophobic coatings is simple and can be applied on large areas of different kinds of substrates. [ABSTRACT FROM AUTHOR]

Abstract: The reactive extrusion of lauryl lactam to polyamide 12 (PA12) of controlled molar mass was successfully performed in a microcompounder. The maximum residual monomer content was less than 1%. The in-situ polymerization in the presence of 1–5wt.% multiwalled carbon nanotubes (MWCNTs) was studied and the processing conditions were optimized with respect to the electrical resistivity and MWCNT dispersion. Runs which yielded in higher molar mass PA12 resulted in better dispersion of MWCNTs, whereas nanocomposites with lower molar mass PA12 had lower electrical percolation thresholds (MWCNT concentration ∼1wt.%). A high screw speed of 200rpm was identified to cause best dispersion and the lowest percolation threshold. Subsequently, the in-situ polymerized composites were compared with composites obtained by direct melt mixing of PA12 with MWCNTs. In comparison to the composites from commercial PA12 and MWCNTs, the dispersion of primary MWCNT agglomerates via in-situ polymerization is considerably better from which better mechanical properties may be expected. However, better dispersion did not result in a reduced electrical percolation threshold and resistivity. In summary, in-situ polymerization of lauryl lactam under the given conditions was shown to be a suitable processing route to obtain good MWCNT dispersion in PA12. [Copyright &y& Elsevier]