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The effect of the so called environment friendly hybrid flammability reducing fillers, i.e. the halogen/antimony-free ones containing phosphorous, nitrogen and silicon on the utility properties of carbon reinforced epoxy laminates was studied. The total content of the fillers did not exceed 23 wt.%. The flame resistance of the laminates aimed as parts of aircraft construction was determined. The fire retardancy mechanism of the hybrid fillers was investigated by SEM/EDS examination of partially burned laminates. The best combination of flammability reducing fillers for the epoxy composite matrices consisted of 15 wt.% ammonium polyphosphate, 5 wt.% dipentaerythritol, and 3 wt.% organofilized bentonite. The synergy of silicon and phosphorus in this composition provided material of UL-94 flammability class V-0.

Summary This study aimed at investigating into possible applications of polyhedral oligomeric silsesquioxanes (POSS) as fillers of epoxy elastomers. Detailed studies were carried out for octakis[(3-glycidyloxypropyl) ­dimethylosiloxy]octasilsesquioxane (POSS-OG). The elastic epoxy materials consisted of diglycidyl ethers of 1,4-butanediol or 1,6-hexanediol, crosslinked with polyoxypropylenediamine Jeffamine D2000. The results obtained by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), and rheological measurements made it possible to establish the effect of POSS-OG modifier on the properties of the material. The silsesquioxane modifier was found to enhance the elasticity of the resulting polymers and reduced gelation time.

This article concerns the study of polymer composites with anthracite fillers of various structural order. Raw Svierdlovski anthracite of turbostratic structure and the anthracite thermally treated at 2,000°C of graphite-like structure were used as fillers of low-molecular-weight diglycidyl ether of bisphenol A cross-linked with aliphatic amine. Two anthracites of extremely different structures were compared to natural graphite that is composed of well-ordered graphene sheets. Systematic studies of the influence of the structure of anthracite filler on the curing behavior, morphology, dynamic mechanical thermal properties, and thermal stability of epoxy composite were performed. It was found that the structure of anthracite filler affects the cross-linking reactions of the epoxy matrix as well as the morphology of the composites and their viscoelastic properties. Raw anthracite added to epoxy matrix had a visible effect on the activation energy and differential scanning calorimeter parameters of the curing process, in contrast to the epoxy matrix modified with anthracite heated at 2,000°C. On the contrary, the effect of anthracite on dynamic mechanical behavior of composites is more evident when the anthracite prepared at 2,000°C was used as a filler. POLYM. COMPOS., 36:336–347, 2015. © 2014 Society of Plastics Engineers

It is well known that addition of a small amount of nanoparticles to liquid crystals may enhance their nonlinear optical properties. To date, in most reports, semiconductor- or metallic-core nanoparticles in LCs have been described. Here, we report on the synthesis of two types of novel nanoparticles based on a cubic siloxane cage (RSiO3/2)8, known as polyhedral oligosilsesquioxane (POSS) with the Si–O skeleton surrounded by covalently attached eight groups (R) of azo-benzene mesogenes differing in the length of their aliphatic chains. These dielectric-core nanoparticles substituted with mesogenic groups are well adapted to the calamitic liquid crystal matrix. Azo-benzene units add an important light-driven functionality to the system via their conformational photoisomerisation. We report on the photochromic properties of these new compounds in chloroform. By embedding the nanoparticles in a nematic liquid crystalline matrix, a functional hybrid nanocomposite material has been obtained. Our research was focused on the characterization of the third order nonlinear optical properties in this system linked to photochromism. The experimental results of all-optical switching in an optical Kerr effect configuration are discussed in the framework of light-induced modification of the aliphatic chains containing azo-benzene photoisomerizing moieties and following local director reorientation in nematic liquid crystals. The described properties are useful in the field of real-time holography.

Unsaturated polyester (UP) resins were filled with up to 3 wt % of bentonites modified with silsesquioxanes (POSS). The effects on mechanical properties and flammability changes of the composites obtained therefrom are presented. The mechanical properties of cured resins were improved; the tensile strength and Charpy impact strength increased by up to 44% and 59%, respectively, compared to unmodified resins. The cured resins had a typical clay nanocomposite structure with layer-like morphology, as observed in scanning electron microscopy (SEM) photomicrographs of brittle fractures, an absence of X-ray diffraction pattern (because of the smectic structure of clays), and exfoliated structure, as evidenced by transmission electron microscopy (TEM) examination. The presence of POSS-modified bentonites in cured UP resins improved their flame resistance, as exemplified by the increase in the limiting oxygen index, from 17.2 for unfilled resin to 25.2 for the resin containing 3 wt % of Wyoming bentonite modified...

Summary — Biostatic and thixotropic properties of bentonites modified with quaternary ammonium salts (QAS) in a waterborne paint and acrylic lacquer are presented. The fungistatic properties were tested for two commercially available bentonites modified with QAS. The bentonites were added to emulsion acrylic paint and acrylic lacquer in the amount of 2 or 4 wt. %. The resulting compositions were put on gypsum plaster disks and treated with Aspergillus niger and Penicillium chrysogenum, the molds frequently met in human environments. Microbiological tests were performed using procedures consistent with Polish Standards with modifications which stemmed from the materials used. The presence of bentonites modified with QAS substantially improved the resistance of coatings against microorganism colonization. Thixotropic properties of paint compositions containing modified bentonites were also found improved.

A typical composition consisting of a low-molecular commercial epoxy resin based on bisphenol A and aliphatic polyamine hardener: triethylenetetramine was modified by replacing a part of the composition with up to 15 wt.% of low molecular weight bis(glycidylpropyl)- or bis(aminopropyl)-tetramethyldisiloxane. The reactivity of the compositions and basic properties of the resulting epoxy polymers, including glass transition temperature, storage modulus, thermal stability, impact and bending strengths, Brinell hardness, and flammability (limiting oxygen index) were evaluated.

Changes in dispersity of step-growth linear polymer were calculated for systems where monomer was added to polymerization reactor in portions, each after the previous ones reached certain conversion or after predetermined time. For step-growth branching polymerization involving di- and trifunctional monomers used in the ratios that do not lead to gelation it was shown that the monomer mixtures can be forced to gel, when they are introduced to the reactor in several portions.

The properties of two pairs of recently synthesised compounds with mesogenic unit were compared. The four compounds consist of a central segment (based on biphenyl or phenylbenzoate) with symmetric carbon chains ended with vinyl or epoxy groups. Typical measurement techniques (including microscopic observations, differential scanning calorimetry and wide-angle X-ray scattering and dielectric studies) were used to examine phase transitions in the studied materials. The phase transition sequences were determined for all materials. A liquid crystalline phase appeared in some cases. It was observed that replacing the functional group in the tails visibly changes the temperatures and sequences of phase transitions.

We present the synthesis, characteristics and curing process of liquid crystalline epoxy monomers containing a central triaromatic mesogenic group. The epoxy monomers were cross-linked with aromatic amines or dicarboxylic acids. In most cases, solid, thermally stable and anisotropic products were obtained. The curing reactions of the monomer were also carried out with selected fillers. The cross-linking process of the composites was monitored by differential scanning calorimetry and dielectric relaxation spectroscopy to compare with analogous liquid crystalline systems not containing filler. Some properties of the cured resin and the composites are described and discussed.

A step-growth alternating copolymerization of monomers A 2 and B 3 was studied by an off-lattice Monte-Carlo simulation. In the random systems, i.e. with no substitution effect, the polymerization leads to gel formation provided the molar ratio of monomers is not very far from the stoichiometric one (A 2 : B 3 ≈ 3: 2) and the reaction is carried out in one batch. A substantial deviation from the stoichiometric ratio may halt gelation altogether, even at conversions of the minority functional groups approaching unity. We demonstrate that in these non-gelling off-stoichiometric systems, one can force the system to gel, after all, without altering the kinetics or diffusion parameters of the reaction. The clue is to carry out the reaction in steps.

Monte Carlo simulations were carried out to model the molecular size distribution in a hyperbranched polymerization involving a monomer of AB 2 type, where A and B were functional groups reacting with each other only. Three approaches were tested: the off-lattice percolation, classical percolations on square or cubic lattices with adjustable reaction range, and the dynamic lattice liquid (DLL) simulation. The latter was used also to investigate dependence of the average radii of gyration of hyperbranched macromolecules on the conversion.

The molecular mobility of four liquid crystalline epoxy compounds was studied by dielectric spectroscopy in a wide range of frequency (10−1–109 Hz). All the investigated materials form a nematic liquid crystalline phase at temperatures above 60 °C, one of them additionally exhibits a smectic A phase. Two of the compounds have molecules composed of a mesogen and two symmetric tails with eight alkyl groups each. Their properties were compared with the homologous pair having two alkyl groups in each tail. The length of the carbon chain influences the temperature range of the mesophase, which was also observed in this study. Characteristic relaxation processes were observed in the different mesophases. These processes were quantitatively analyzed and the estimated parameters were discussed in detail in dependence of the structure of the materials.

Properties of liquid crystalline polymer networks depend on the structure of the reagents as well as on the density of cross-linking bonds, which – in turn – is affected by the degree of ordering of the molecules during the reaction. Changing external conditions (including temperature, time of curing and various factors enforcing orientation of the monomers, such as preparation of cell surface or magnetic field) one can obtain different products. The influence of these external factors on the properties of cured epoxy monomers is studied in this paper. Liquid crystalline polymer networks were obtained as a result of curing three different epoxy compounds with 4,4′-diaminodiphenylmethane (DDM). All the three monomers have nematic phases in wide range of temperatures. The process of cross-linking, the final product of curing and the pure monomers were examined using polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). Chemical structure of the products was confirmed using spectroscopic methods. The study demonstrates that setting up specific conditions for curing (a temperature corresponding to liquid crystallinity range of pure monomer and an external factor enforcing molecular alignment in liquid crystalline phase) may result in cured products with somewhat better organisation at the molecular level.

Two recently synthesised diepoxy compounds based on the same rigid central segment with carbon chains of different lengths were compared. Microscopic observations, differential scanning calorimetry (DSC) and dielectric measurements confirmed the existence of a mesophase in both compounds and enabled determination of the temperatures of phase transitions. Wide-angle X-ray scattering (WAXS) measurements and optical observations enabled identification of mesophase types. Nematic phase appeared in both compounds; in the material with longer chains smectic A phase was also detected. Lengths of the molecules and average nearest neighbor distances were estimated using the wide-angle X-ray scattering results. Lengths of the molecules were also computed by quantum mechanical methods resulting in very good agreement with the experimental data.

This paper reports on the work carried out to evaluate the frequency dependent viscoelastic properties of epoxy/novolac compositons modified with a liquid reactive rubber and carbon filler. For epoxy systems modified with elastomer, three typical transitions were observed: the α-relaxation deeply related to the glass transition of epoxy, the β-transition of epoxy, and the glass transition of rubber appeared near to the β-relaxation of epoxy resin. Considering an Arrhenius equation, the activation energies of β-relaxation were estimated. In the region of glass transition and rubbery state the temperature dependence of the shift factor (αT) was determined through Williams-Landel-Ferry (WLF) equation.

The curing behaviour of epoxy resins modified with reactive liquid rubber, using a novolac resin as a hardner was studied by means of differential scanning calorimetry in isothermal (100, 130 and 150 °C) and non-isothermal conditions (2, 5, 10 and 15 °C min-1). The influence of carboxyl- (CTBN) and epoxy- (ETBN) terminated butadiene-acrylonitrile copolymers on the kinetic parameters and glass transition temperature (Tg) of cured epoxy systems was determined. The effect of grinded bituminous coal as an organic filler into epoxy network was also investigated. The carboxyl-end groups strongly enhanced the curing rate, in contrast to the epoxy-terminated rubber (ETBN) that had only a minor effect on the curing reactions. The presence of coal accelerated curing in its early stage. The Tg of completely cured epoxy was practically unaffected by the presence of carbon filler and reactive rubbers and was equal about 132 °C. The apparent curing activation energies were determined. A smaller activation energy was observed only for CTBN/epoxy/novolac system. The effect of reactive rubber and coal on the Charpy impact resistance of cured epoxy systems was also discussed.

Three recently synthesized epoxy monomers were studied. All the monomers form a nematic phase in temperatures above 80 °C. This paper presents the dielectric response of pure monomers in the frequency range of 10 6 –10 9 Hz as well as its changes occurring in the course of crosslinking with 4,4′-diaminodiphenylmethane used as curing agent. A relaxation process related to molecular motions is clearly visible in this frequency range for each of the monomers, though its characteristics are somewhat different in particular cases. The evolution of the relaxation process is visible in the course of curing. The dynamics of curing observed through dielectric data is compared with the results of differential scanning calorimetry measurements.

Summary: Having developed a theoretical model of hyperbranched polymerization involving AB2 and B2 monomers we present preliminary results of a test of its validity for the system consisting of 4,4-bis(4-hydroxyphenyl)pentanoic acid (AB2 monomer) and bisphenol A (B2 monomer). The monomers reacted at room temperature to yield the title hyperbranched polyesters. Diisopropylcarbodiimide (condensation water remover) along with an effective catalyst were used for that purpose. The total of AB2 monomer was introduced at once to a reactor containing B2 core monomer or it was divided into 3 or 5 equal portions and each of them introduced after the monomers previously present have reacted to a predetermined conversion. GPC measurements of the resulting molecular mass distribution gave inconclusive results because of poor reproducibility of polymer isolation/purification procedure and/or insufficient accuracy of GPC technique.

A new liquid-crystalline epoxy monomer (LCEM) containing central triaromatic mesogen and aliphatic spacers consisting of eight methylene units terminated with epoxy groups was synthesized and characterized by means of IR and NMR spectrometry, differential scanning calorimetry (DSC), polarized optical microscopy, and wide-angle X-ray scattering. The cure reaction of LCEM with primary aromatic diamines in a stoichiometric ratio and with a tertiary amine catalyst of polymerization and the properties of the cured products were investigated with a DSC technique. The effects of the curing conditions (polyaddition vs anionic polymerization) and the structures of the amines on the formation of liquid-crystalline networks were studied. The monomer cured with selected amines yielded an anisotropic network. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 224–228, 2007

The effects of types and amounts of the additives: butadiene-acrylonitrile rubbers, with carboxyl or epoxy groups as chain ends (CTBN and ETBN, respectively), on mechanical properties and morphology of epoxy composition consisting of low molecular weight epoxy resin, type Bisphenol A diglycidyl ether (,,Epikote 827"), phenol-formaldehyde novolak (NZ) and up to 16 wt. % of coal showing medium metamorphism degree as a filler, were investigated. Mechanical properties were evaluated using static (Table 1) and dynamic methods (DMTA, Fig. 1-6). Optical microscopy and transmission electron microscopy (TEM) methods were used to study the morphology of the products. DMTA analyses results showed the effects of CTBN and ETBN on storage modulus (E') in the whole range of measurement temperature (from room temperature up to 250 °C). The effect of rubber addition on glass transition temperature (Tg, evaluated as maximum tg 5) of tested cured compositions is marginal. It was found that the addition of only coal filler deteriorated mechanical strength and impact strength of the composition while introduction of a system: coal filler/rubber did not cause that adverse effect. It was also found that morphology and phase separation influenced the mechanical properties significantly (Fig. 7-10). The optimal concentration of CTBN or ETBN rubber introduced to the composition containing - or not - the coal filler is 6 wt. %. This amount of a rubber does not lower To of the composition yet.

A simple kinetic model of modelling hyperbranched polymerisation involving AB2 and Bf core monomers is developed and analytical solutions of the model are presented. The number- and weight- average polymerisation degrees can be calculated using the model as functions of polymerisation time or conversion degree. Application of the model is tested for predicting the broadness of molecular size distribution of the hyperbranched polymers obtained by varying the procedures of feeding AB2 monomer to polymerisation reactor.

A kinetics model was developed describing the time evolution of the molecular size distribution in hyperbranched condensation polymerization of monomers AB2 and B2 (A and B are functional groups). The rate equations derived from the model were used to calculate moments of the distribution of polymer species. The calculation procedure was adjusted to simulate introduction of fresh AB2 monomer into the polymerization reactor in equal portions, with each portion introduced after the previous one reached a predetermined conversion degree. The core monomer B2 was introduced with the first portion. The calculation procedure also made it possible to subtract unreacted monomer from the system. This was yet another method of narrowing the molecular size distribution of polymers in addition to the feed scheme. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.

A generalized theoretical model of hyperbranched polymerization of an AK f monomer was used to calculate the weight average polymerization degree (P ω ) and dispersity index (D M ) of the resulting hyperbranched polymers. The monomer functionalities were f = 2, 4, or 6. The model derived in Part I of the series and based on the Smoluchowski coagulation equation was used. The monomer functional groups B reacted according to the first shell substitution effect principle. Both, the weight average polymerization degree and dispersity index were found to grow with conversion the faster, the higher was the monomer functionality and the more positive was the substitution effect.

Smectic clays with quaternary ammonium salts (QAS) were subjected to hydrophobization, whereupon we applied the products in attempts to modify various polymers. The clays were of natural origin and contained a large proportion of montmorillonite and an original method of modification was applied. A significant improvement of the stability of unsaturated polyester (UP) resins, modified with clays modified with QAS, was observed with essentially no change in the reactivity of resins. The compositions of polyester resins containing 2 wt % of modified smectites had excellent thixotropy. The presence of modified bentonites in a cured commercial UP resin (2–4 wt %) improved its tensile strength (by 21–62%), Brinell hardness (23–70%), and unnotched impact strength (23–100%), depending on the type of bentonite used. The compositions of UP resins with modified clays had certain properties typical for nanocomposites: improved stiffness, strength, transparency, and fine-lamellar morphology of the fracture as found by electron scanning microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 793–801, 2005

Computer simulations of the step-growth homopolymerization of an AB 2 monomer have been carried out on a square lattice. No rearrangements of units were made between reaction events. Instead, the capture radius, i.e., the maximum distance between the randomly selected unit and its reaction partner was changed. The reaction was considered as controlled either by diffusion and local concentration fluctuations or by the law of mass action (classical limit). The size distribution of polymer species and the extent of cyclization reactions in the polymerization are discussed.

A generalized theoretical model of hyperbranched polymerization of an AB f monomer is derived. The model is a classical mean-field one based on the Smoluchowski coagulation equation. The monomer functional groups B react according to the first shell substitution effect principle. It is shown that irrespectively of the monomer functionality (f), the number average molecular weight of hyperbranched polymers depend on conversion of A groups in exactly the same way. Also the degree of branching, a parameter describing perfectness of polymer structure changes very slightly with increasing functionality of the monomer.

On the basis of literature data, the structures, types and properties of liquid crystalline polymers have been characterized. The subject of the own research was two-step synthesis of four new liquid crystalline epoxy monomers. They were obtained by esterification of four various diphenols, showing rigid structure, with 4-pentenoic acid and subsequent epoxidation of obtained unsaturated esters using m-chloroperbenzoic acid (Scheme A). The structures of the cured products obtained as well as the courses of the monomers' curing were investigated using DCS, WAXS and polarization microscopy methods. The results concerning the curing of p-phenylene bis[4-(4,5--epoxypentanoyloxy)benzoate] (MU2 according to Scheme A) with p-phenylene diamine (PDA), 4,4'-diaminodiphenylmethane (DDM) and 4,4'-oxyphenylenediamine (DDE) (Figs. 3-6 and 8) were described in details. It was found that as a result of the process of mesogenic diepoxy monomers' curing carried out at the temperature of mesophase existence, liquid crystalline order had been mostly maintained.

Summary - A recycling method of RIM PUR foam wastes by controlled degradation during twin-screw extrusion has been developed. The process involves breakage of only cross-linking bonds (allophanate and,/or biuret bonds) in the polymer. The essential factor that has to be controlled is int. al., decreasing temperature profile along extruder cylinder (from fed hopper to die). The method provides thermoplastic elastomer of strength comparable to . that of the original material. It can be injection molded or extruded into various products. Reactive co-extrusion of polyesterdiol based PUR wastes with PVC-U (5-10 wt. "k) that yields homogeneous polymer blends of improved

A kinetic model of hyperbranched polymerization is presented where an AB2 monomer reacts with up to 10% of a B3 one (A and B are functional groups) to yield a hyperbranched polymer. The model consists of two compact rate equations for entire distributions of two kinds of molecules that are formed in the system. Changes in reactivity of B groups in the form of the so-called first shell substitution effect are taken into account. Molecular parameters, namely the number and weight averages of polymerization degree as well as the average degree of branching of hyperbranched molecules, are extracted out from the rate equations and plotted against conversion.

A model is developed in the form of one or two partial differential equations (master Smoluchowski-like equations) that describe evolution of the size distribution of polymer species formed in a step-growth polymerization of an AB2 monomer. Groups B react with a substitution effect; i.e., they are initially equally reactive, but the reactivity of the second B group changes as the first has reacted. One master equation is sufficient to model formation of branched molecules only. Two are needed to take into account intramolecular cyclization. Monte Carlo simulations of the same process are used to verify the results of applying the kinetic model. The model can be applied to calculate various molecular parameters in polymerizing systems, including various average degrees of polymerization, size distribution of acyclic and cycle-containing polymer molecules, degree of branching, etc. Explicit formulas describing the dependence of some of these quantities on time or conversion degree are derived for the random...

A Monte Carlo computer model of is described for hyperbranched polymerization involving AB 2 monomers. The structure of algorithm used in the model and selected results of its application are presented. The results are compared with those obtained by using an analytical kinetic model. For analogous polymerization systems, the two models were found to yield identical molecular parameters, viz., the average degrees of polymerization as the degree of conversion was varied, and polydispersity index for the reacting systems involving different substitution effects.

Two basic groups of models of polymerisation, the classical, known as the Flory-Stockmayer models, and the computer based ones which are in fact Monte-Carlo simulation techniques are briefly reviewed. The notion of time correlations is explained. Four versions of kinetic modelling of hyperbranched polymerisation are presented.

A system involving homopolymerisation of a 3-functional monomer has been studied by using an off-lattice long-range percolation model. The elementary reaction steps were controlled by substitution effects and by local concentrations of units. The latter were controlled by setting a constant value to a range-of-reaction parameter called the capture radius. The critical conversion at gelation in the system turned to the classical one as the value of capture radius increased.

Two mean-field kinetic models of the polymerization of an AB 2 monomer that lead to hyperbranched polymers are presented. The first model deals with oranched molecules only and constitutes a new yersion of the Flory theory. Its modification, which takes into account ring formation, is the second model. Preliminary results of the application of the models are shown and discussed.