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The “in service “properties' of high performance composites degrade due to the development of different damage modes occurring hierarchically at different length and time (cycles) scales, from diffuse crackand crazing within the polymer matrix, to fiber-matrix interface failure, to ply rupture and delamination where catastrophic failure occurs. The density of cracks within the matrix saturates at very early stage of the service life of the composite component and this “Critical Damage State” (CDS) triggers the other damage modes. Thus, shifting the CDS toward higher number of cycles allows enhancing the overall fatigue performances of composites, that is the main objective of our proposal. The matrix weakness is due to the residual stresses (of order of magnitude of the matrix strength) that accumulate as consequence of the manufacturing process. In order to relax the residual stresses we propose to take advantage of the anomalies of nanoconfined thermoplastic polymers that show a negative coefficient ofthermal expansion at temperatures below Tg. Silica microspheres can be covered by polymer shells of 10-40 nanometers and added to the reactive resin in order to counter balance the resin contraction through the expansion of the nanoconfined polymer, during cooling.

Additive Manufacturing (AM) of polymer composites has enabled the fabrication of highly customized parts with notably mechanical properties, thermal and electrical conductivity compared to un-reinforced polymers. Employing the reinforcements was a key factor in improving the properties of polymers after being 3D printed. However, almost all the existing 3D printing methods could make the most of disparate fiber reinforcement techniques, the fused filament fabrication (FFF) method is reviewed in this study to better understand its flexibility to employ for the proposed novel method. Carbon nanotubes (CNTs) as a desirable reinforcement have a great potential to improve the mechanical, thermal, and electrical properties of 3D printed polymers. Several functionalization approaches for the preparation of CNT reinforced composites are discussed in this study. However, due to the non-uniform distribution and direction of reinforcements, the properties of the resulted specimen do not change as theoretically expected. Based on the phase inversion method, this paper proposes a novel technique to produce CNT-reinforced filaments to simultaneously increase the mechanical, thermal, and electrical properties. A homogeneous CNT dispersion in a dilute polymer solution is first obtained by sonication techniques. Then, the CNT/polymer filaments with the desired CNT content can be obtained by extracting the polymer’s solvent. Furthermore, optimizing the filament draw ratio can result in a reasonable CNT orientation along the filament stretching direction.

Blends based on protein hydrolysate (PH), derived from waste products of the leather industry, and poly(ethylene-co-vinyl acetate) (EVA), were obtained by reactive blending and their physico-chemical properties as well as their mechanical and rheological behavior were evaluated. The effect of vinyl acetate content and of a transesterification agent added to increase interaction between polymer and bio-based components were investigated. Novel biodegradable polymeric materials for spray mulching coatings were also obtained from hydrolyzed proteins and end-functionalized poly(ethylene glycol) (PEG), which was used as crosslinking agent. These products, almost entirely obtained from renewable sources, represent a new type of biodegradable material which looks promising for several applications, for instance in packaging or in agriculture as transplanting or mulching films with additional fertilizing action of PH. POLYM. COMPOS., 37:3416–3422, 2016. © 2015 Society of Plastics Engineers

The principal features of the volumetric as well as the viscoelastic response of mechanically stimulated glasses can be summarized as follows: i) the time-aging time shift factors contract upon increasing the probe stress (i.e. the stress apparently modifies the volume recovery kinetics), ii) the volume recovery baseline remains unaltered (i.e. the underlying structure of the stimulated glass remains unchanged) iii) yielding scales linearly with the logarithmic of the strain rate. Here we present a review of the above features with aid of a series of numerically simulated results concerning the responses of glassy polycarbonate. Simulations are obtained coupling a modified KAHR equation with the constitutive law for linear viscoelasticity within the domain of the reduced time. It will be shown that by using a minimum of experimental (PVT and linear viscoelastic) data inputs even the subtle intricacies can be predicted. Furthermore a new class of results concerning the stress-strain behaviour of glassy polymers is presented that never appeared before.

Processing of polymer-based composites requires deep knowledge of materials property evolution. In this paper, a comprehensive approach to account for the dimensional and mechanical property changes as function of process parameters is presented. Valid experimental results were obtained to model material properties during the curing process and good agreement has been found with proposed constitutive models. Theoretical predictions of the strip curvature are generated using commercial FEM software (ANSYS) and compared with experimental measurements.

Glassy polymers confined at nano‐scale do exhibit anomalous thermo‐viscoelastic behavior in respect to their bulk response. For example, in ultra‐thin polymer films both negative coefficient of thermal expansion (NCTE) and glass transition temperature (Tg) depression are observed, experimentally. Theoretical conjectures have been drawn that qualitatively explain some features of highly confined glassy polymers [1,2,3] yet quantitative prediction of NCTE and Tg depression would allow a reliable design of devices operating at nano‐scale. In this paper the thin films anomalies are shortly reviewed and their explanation is tempted with classical existing theories.

Linear and cross-linked polymers capable of responding to both temperature and pH changes were synthesized by radical copolymerization of N-isopropylacrylamide (NIPAAm) and N-methacryloyl-L-leucine (MALEU) in different NIPAAm/MALEU molar ratios. The solution behavior of linear polymers was investigated in 0.1 M NaCl and in citrate buffers pH 4.0, 4.5. 5.0 and 6.0. A sharp increase in the cloud point temperature (T CP ) was observed to occur around pH 4-5, Hydrogels were synthesized employing N,N'-methylenebisacrylamide as cross-linking agent. The influence of composition and degree of cross-linking on water absorption was investigated in 0.1 M NaCl and in citrate buffers pH 4.0 and 5.0. A reversible phase transition within a wide range of temperatures, depending on the composition and the pH, in accordance with the behavior of linear polymers, was observed.

The structural relaxation process of an inorganic glass (Li(2)O2SiO(2)) at different cooling rates has been studied by differential scanning calorimetry. A four-parameter model-Tool-Narayanaswamy-Moynihan (TNM) model was applied to simulate the normalized specific heat curve measured. Four parameters, Delta h*/R, beta, In A, and x were obtained and compared with the values obtained from the isothermal approach. (C) 1999 Kluwer Academic Publishers.

A two-parameter model explicitly accounting for the cyclic as well as the mean stress was proposed and tested on the basis of static and fatigue data obtained in four-point bending on a random continuous glass-fiber-reinforced polypropylene. The model is based on residual strength degradation and captures the effect of stress ratio (i.e. the ratio between the minimal and the maximal stress). The experimental data were in excellent agreement with the theoretical predictions, indicating that a fatigue characterization can be achieved with a minimum of experimental tests. Further, the reasonable agreement between the static strength data and the theoretical predictions highlighted the potential and reliability of the model in view of its statistical implementation

The developments of physical aging in phenolphthalein poly(aryl-ether-ketone) (PEK-C) and poly(aryl-ether-sulfone) (PES-C) with time at two aging temperatures up to 20 K below their respective glass transition temperatures (T-g = 495 and 520 K) have been studied using differential scanning calorimetry (DSC). Substantial relaxation within the aging course of several hours were observed by detecting T-g decreasing during physical aging process at the two aging temperatures. The relaxation processes of both polymers are extremely nonlinear and self-retarding. The time dependencies of their enthalpies during the initial stages of annealing were approximately modeled using the Narayanaswamy-Tool model. The structure relaxation parameters obtained from this fitting were used to predict the possibility of physical aging occurring at their respective using temperatures. (C) 1995 John Wiley and Sons, Inc.

The flexural fatigue behavior of continuous and short glass reinforced composites was investigated under four-point bending loading. The effect of mean stress and stress amplitude was identified. It was found that the fatigue life decreased rapidly with the decreasing stress ratio (i.e. the ratio between the minimum and the maximum stress). Further, the specimen lifetime for any loading mode increased with : (a) decreasing load range and decreasing stress ratio and (b) decreasing mean load and increasing stress ratio. From the above observations a brand new two-parameter model based on strength degradation was developed accounting for both the mean load and the load range, in order to express analytically the strength variation during fatigue cycle evolution.

The principal features of models of structural relaxation in the glassy state were reviewed. The concepts of fictive temperature as the structural parameter and nonexponentiality and nonlinearity of structural relaxations were described. Various expressions for the structural relaxation time were presented and compared. One particular model was selected and utilized in a parametric optimization study of structural relaxation. Model predictions were checked against experimental results obtained by volumetric and calorimetric measurements.

The density evolution of a semi-crystalline Poly(lactic acid) under ultra/high pressure histories in the region of alpha relaxation has been studied. It was found that the degree of crystallinity does not change in the temperature and pressure ranges under concern and consequently it is assumed that the volume relaxation kinetics involves only the amorphous part of the polymer. The scaling law for relaxation times, recently proposed by Casalini and Roland, has been utilized in the framework of KAHR (Kovacs Aklonis Hutchinson and Ramos) phenomenological theory in order to model the volume relaxation behavior. With this approach the model contains only two fitting parameters, (namely the relaxation time in the reference state, τg, and the fractional exponent, β, that describes the dispersion of the alpha relaxation) instead of the five parameters of the classical KAHR theory. The model predicts accurately both the density evolution of the PLA during the sterilization and Pasteurization treatments simulated in a pressure dilatometer and the density changes occurring in the PLA films utilized as packaging material in the HP industrial processes.

Non-equilibrium glasses, including polymer glasses, spontaneously tend to approach the equilibrium state. The time-dependent phenomena occurring in glassy polymers below the glass transition are commonly referred to as physical aging. Since the physical aging results primarily in a volume relaxation (or densification), our efforts have been focused on the measurements of the time-dependent behavior of the specific volume. The dependence of the storage and loss moduli upon aging have been related to the progressive loss of mobility associated with the volume relaxation. A Williams-Watts type equation has been adopted to model the volume relaxation data at different temperatures, and a numerical procedure has been developed in order to predict the kinetics of volume relaxation subjected to complex thermal histories.

High performance polymer based‐cements (i.e. cements having a water to cement ratio, w/a, close to 0.1) almost totally free of defect, have been developed in recent years claiming a great interest for their very high tensile strength compared with traditional cements. These materials can be produced utilizing very simple unit operations and further formed in complex shapes with high surface quality. Indeed these materials have the disadvantage of being too much brittle and for this main reason they are rarely utilized in practice. Toughening the Macro Defect Free Cements (MDF) implies the strict control of the structure. The structure is governed by the process‐induced paste modifications. In this paper we show that toughening can be achieved with elastomeric particles having well defined size distribution and physico‐chemical characteristics in relation with both the binder polymer and the cement chemistry.

Residual stresses in reactive resins‐based composites are associated to the net volumetric contraction (shrinkage) arising during the cross‐linking reactions. Depending on the restoration geometry (the ratio of the free surface area to the volume of the cavity) the frozen‐in stresses can be as high as the strength of the dental composites. This is the main reason why the effectiveness and then the durability of restorations with composites remains quite lower than those realized with metal alloys based materials. In this paper we first explore the possibility to circumvent the mathematical complexity arising from the determination of residual stresses in reactive systems three‐dimensionally constrained. Then, the results of our modeling approach are applied to a series of commercially available composites showing that almost all samples develop residual stresses such that the restoration undergoes failure as soon as it is realized.

We have recently reported that the volumetric as well as the viscoelastic intricacies of mechanically stimulated glasses can be predicted by coupling the structural relaxation kinetics and viscoelastic response [1, 2, 3].Here, it will be shown that our approach can be extended to predict the stressstrain behaviour of glassy polymers as function of temperature, strain rate and aging time. In particular, a linear dependence of yield stress on the logarithmic of the strain rate can be obtained, conforming to the classical Eyring-type behaviour. The Poisson’s ratio evolution was obtained from the volume relaxation behaviour highlighting an unexpected correlation between the yield point and the volumetric behaviour.

In this paper the source of non linearity in amorphous materials will be analyzed and verified with phenomenological approaches. A series of simulated results, replicating the relevant experimental data presented in literature along the years, will be reported.

Viscoelastic effects occuring in amorphous and semicrystalline poly (ether ether ketone) (PEEK) and in a PEEK-based composite (APC2) have been analyzed by means of transient (creep) and dynamic mechanical tests, in the range of temperature covering the main viscoelastic regions. In the sub- T g region the non-linear approach to viscoelastic phenomena, i.e. creep, is related to the volume relaxation, and the effect of thermal treatments (physical aging) on the polymer amorphous phase of the three systems is presented. In the transition region just above T g , the amorphous PEEK undergoes cold crystallization and, as a consequence, passes from a liquid-like to a solid-like state. The isothermal crystallization kinetics and the changes in viscoelastic properties are analyzed by means of dynamic mechanical measurements and compared with calorimetric tests. Above T g the mobility of chains is sufficient to allow the free volume to reach its equilibrium level rapidly at any temperature. The principle of time-temperature superposition is applicable in the conventional fashion using a Williams, Landel and Ferry equation. The shift factors obtained for the crystalline PEEK and for an eight-ply unidirectional laminate are compared.

In the present work, characterization of composite materials based on HDPE and PMMA filled with nanometric hydroxyapatite synthesized in situ by high frequency ultrasound has been carried out. For the composites preparation dilutions of the commercial polymers, using decaline as solvent for the HDPE and 2‐butanone for PMMA, were employed. For the synthesis of Hydroxyapatite (HA), ammonium phosphate [(NH4)2HPO4] and calcium hydroxide [Ca(OH)2] were used as precursors. The products obtained were characterized by FTIR and TEM. The results showed that when PMMA was used as matrix, the presence of nanometric HA with clear interactions with the PMMA matrix was obtained. When HDPE was used as matrix a complex complex calcium phase was obtained and without interaction with the matrix.

Macrocyclic oligomers (MCOs) of some commercial alkyl aromatic polyesters (PET, PTT, PBT) were prepared by cyclo‐depolymerization (CDP) of the polymers in refluxing 1, 2‐dichlorobenzene with di‐n‐butyltin oxide as a transesterification catalyst. The mixtures of MCOs and residual polymer obtained at varying polymer/solvent ratios were separated and characterized by thorough GPC and DSC analyses. The higher the initial polymer concentration the lower was the yield of MCOs, and vice versa. Rheological measurements carried out on polymer/MCO mixtures showed a decrease in the melt viscosity with increasing amount of MCOs. Moreover, the MCOs present in these systems easily underwent entropically‐driven ring‐opening polymerizations (ED‐ROPs) to reform the parent polyesters.

stract: Relevant examples are described here concerning the light response of polypeptides bearing covalently bound photochromic groups in the side chains and the optical properties changes of nanocomposites from organic dyes aggregates dispersed in a thermoplastic matrix. The former system shows how the light induced structural changes in side chain chromophores can be amplified by the attached macromolecular response. The latter system provides evidence of the optical smart response to polymer/organic chromophores nanocomposite.

A wet‐pull‐out method for investigation of interaction between the high performance polyethylene (HPPE) fiber and polymer matrix is discussed. The paper concerns a cold plasma technique for improving the bond of the HPPE fibers to the matrices and the fibers impregnation with the matrix. Controlled parameters are pull‐out force and the height of the matrix capillary lifting along the fiber both in air and in vacuum, in combination with plasma activation of the fibers. The method allows one to estimate the wetting and impregnation of multi‐filament fiber with the matrix and simultaneously measure the joint strength. Coupled action of plasma treatment and vacuum impregnation of the fibers improves the joint strength by a factor of 3. Plasma activated HPPE fibers impregnated in air show the value of shear strength τ of 4 Kg/mm2. To understand the effect of treatment initial and plasma‐activated fibers were used to fabricate composite materials (CM). The properties and failure modes were compared to those of ...

Studies of kinetics of polymer crystallization are generally performed by heating the material above the melting point, in order to erase previous thermal and mechanical history, followed by rapid cooling to the desired crystallization temperature or by cooling at a constant rate. For poly(3‐hydroxybutyrate) (PHB) this procedure implies some degradation of the polymer chain, which starts below the onset of melting. In this contribution the effects of melting conditions on the subsequent crystallization kinetics are discussed. It is shown that in order to sufficiently cancel memories of previous crystalline order of the analyzed PHB, it is necessary to bring the material at a temperature higher than 192 °C. Thermal treatments conducted at lower temperatures are not sufficient to destroy all solid aggregates, and crystallization of PHB has an anticipated onset of crystallization due to nucleation occurring via self‐seeding. The chain degradation attained upon exposure at high temperatures has a much minor i...

This paper describes the research work undertaken to evaluate the performance of materials and bonded joints involving Fibre Reinforced Polymers (FRPs) and concrete. Experimental variables ncluded polymer composite materials, test methods and environmental test conditions. Tensile and flexural tests were carried out to determine short term and long term environmental durability of composite materials. Single lap shear, a modified wedge cleavage and pull‐off adhesion tests were used to study the performance of bonded joints. It is shown the tensile strength of composite materials can be affected after exposure to hot/humid conditions. The performance of stressed single lap joints was also affected by hot/humid conditions.

In last decade embedding of metallic phase to matrices of native polymers have been systematically studied in the Institute of Macromolecular Compounds of the Russian Academy of Sciences. Application of polymer matrices renewable in nature such as cellulose of various origins in solid state and its derivatives in solutions opens capacities to create new class of cellulose nanocomposite materials—powders, fibres and films—containing nanoparticles of silver, copper, nickel, cobalt, etc. These nanocomposites exhibit particular properties due to specific features of nanoparticle surfaces and their sizes. The most important properties among them are antimicrobial, catalytic and magnetic ones. Principles of construction of high organised systems on the basis of non‐covalent binding of metal species to native polymer matrices are developed.

A number of techniques are used to study the chain‐dynamics of solid polymers, including those of dielectric relaxation [1–4], dynamic mechanical thermal analysis (DMTA) [1, 5], multinuclear NMR relaxations [6], quasi‐elastic dynamic light scattering [7] and neutron scattering [8] (QELS & QENS) and transient fluorescence depolarization (TFD) [9]. Each technique has its own particular probe of the dynamics in a material. e.g. dielectric relaxation gives information on the angular motions of molecular chain‐dipoles (for dipole relaxation) and the translational motions of ions (for f‐dependent electrical conduction); NMR relaxations relate to the angular motions of chemical bonds; QELS relates to fluctuations in local refractive index; QENS to the time‐dependent van Hove correlation function (suitably‐defined) for proton‐containing groups; TFD to the angular motions of fluorescent groups in a chain. Due to its relevance to practical applications of materials, DMTA is pre‐eminent among the many physical techniques applied to solid polymers, but interpretations of behaviour in terms of molecular properties remain difficult since the direct link between an applied macroscopic stress and the molecular response of polymer chains in a bulk material remains an unsolved problem.Of the above techniques, Broadband Dielectric Spectroscopy (BDS) offers several advantages.(a) Materials may be studied in the frequency range 10−6 to 1010 Hz, over wide ranges of temperature and applied pressure, using commercially‐available instrumentation.(b) Since the electrical capacitance of a film is inversely proportional its thickness, free‐standing and supported films may be studied down to nm‐thicknesses, giving e.g. information on the behaviour of the dynamic Tg as sample thickness approaches molecular dimensions.(c) Theoretical interpretations of dielectric relaxation and a.c. conduction are well‐established in terms of Fourier transforms of molecular time correlation functions (TCFs) for motions of chain dipoles and ionic species. Large scale “Molecular dynamics” simulations have been used to calculate molecular TCFs, and hence the dielectric properties, of model bulk amorphous polymer materials [10, 11].

Biodegradable polymers are one of the most promising ways to replace non‐degradable polymers. TPS films were prepared by casting from cassava starch and three different vegetable oils of Brazilian Cerrado as plasticizer: buriti, macauba and pequi. In this preliminary work it was investigated materials thermal characteristics by TG and TMA. Thermal properties of oils depends on their chemical structures. Starch and vegetable oils are natural resources that can be used how alternative to producing materials that cause minor environmental impact.

Dextran‐graft‐Polyacrylamide copolymers (D‐g‐PAA) of brush‐like architecture were tested as flocculation aids in the model kaolin suspensions. Due to expanded conformation the D‐g‐PAA copolymers are more effective flocculants than individual PAA with close molecular mass. The internal structure of D‐g‐PAA copolymers which is determined by number and length of grafted PAA chains, the distance between grafts, etc., has the significant influence on flocculation behavior of such polymers.

Relaxation properties and adhesion of pressure‐sensitive adhesives (PSA) have been studied with the Probe Tack and Squeeze Recoil methods under the conditions corresponding to the adhesive bond formation under compressive stress and upon the removal of bonding pressure. Direct correlation has been established between the compressive stress relaxation in the course of adhesive bond formation and the mechanism of debonding. High adhesive strength requires the contribution of the longer relaxation times that vary for different PSAs in the range from 150 to 800 seconds. Relative contributions of viscous end elastic deformations into relaxation properties of pressure sensitive adhesives are assessed in the terms of Deborah number. At the stage of adhesive polymer relaxation after withdrawing of bonding pressure, the relaxation properties have been characterized in terms of retardation times. By comparison of the adhesive and relaxation behaviors of different PSAs, the relaxation criteria for pressure‐sensitive adhesion have been stated. Relaxation behavior of the PSAs examined has been shown to reveal two values of retardation time: the shorter retardation time of 10–70 sec and the longer time of 300–660 sec. The longer retardation times are associated with high adhesion.

The present study deals with model systems based on two immiscible polymers, polypropylene (PP) and copolyamide (PA), containing nano‐size inorganic TiO2, processed in a narrow temperature window, just below the melting temperature of the dispersed copolyamide phase. The blends were compounded using a twin‐screw intermeshing extruder followed by injection molding. The effect of processing temperature and blend composition on morphology, mechanical, rheological and thermal properties of the model systems containing nano‐sized TiO2 and their references were explored. It was found that in‐situ fibrillation of the PA phase occurred in the blends based on PP of a relatively high melt flow index, MFI = 12 g/10 min and higher. The nano‐sized TiO2 particles were located upon and within the PA phase and have slightly influenced the shape of the PA fibrils. A correlation between the processing temperature, morphology and properties of the composites is presented.

Nanocomposites consisting of spherical particles of Ag were prepared using a single step in situ method for incorporating metal into PEI whereby the metal is introduced into the dissolved polymer via dissolution as an organometallic complex in the same solvent as the polymer. The kinetic rate of formation of the particles is determined using WAXS and SAX measurements. Nanoparticle formation is found to depend on reducing the solvent/polymer ratio, de‐solvating the metal complex. This destabilizes the metal precursor complex, causing it to degrade and the metal particles to phase separate by a thermodynamic, probably spinodal driving force. The size of the nanoparticles varies with the cure temperature and the conditions affecting molecular mobility.

In the last years there has been much interest in applying ink‐jet printing (IJP) technology to the deposition of several materials for organic electronics applications, including metals, polymers and nanoparticles dispersions on flexible substrates. The aim of this work is to study the effect of ink‐jet deposition of polymer films in the manufacturing of OLED devices comparing their performances to standard technologies. The ink‐jet printed polymer is introduced in an hybrid structure in which other layers are deposited by vacuum thermal evaporation. The electrical and optical properties of the obtained devices are investigated.OLEDs with the same structure were fabricated by spin‐coating a polymer film by the same solution used as ink. Results have been compared to the above ones to determine how the deposition method affects the device optoelectronic properties.

With the aim to investigate the influence of slight differences in the chemical structure of a family of polymers on the response of these to electric perturbation fields, the relaxation behavior of three dimethoxy phenyl isomers of poly(benzyl methacrylate) have been studied.

Gold nanoparticles of regular shape have been obtained by thermal decomposition of AuSC12H25 molecules dissolved in different amorphous polymers. In particular, the formation of triangular nano‐platelets has been observed using poly(vinyl acetate) and poly(methyl methacrylate) as particle growth medium. Whereas, when polymers with less‐bonding side‐groups were used (e.g., poly(vinyl alcohol), polystyrene), the gold nanoparticles did not develop a regular shape during their growth.

A poly(ethersulfone) (PES) engineering thermoplastic was used as toughening agent for an epoxy resin. Different percentages of PES in the resin were used, then cured by electron beam irradiation and some samples were thermally post‐cured. The influence of the hydrothermal ageing on all types of samples was studied, measuring the water absorption percentage, the thermal properties, by dynamical mechanical thermal analysis (DMTA), and the toughness, by K|c measurements.

Polymer layered silicate nanocomposites based on a commercial grade resol were produced using a simple, low labor cost mechanical approach, providing an effective alternative to the more traditional technique based on the use of the intercalative polymerization of phenol and formaldehyde monomers. The matrix was a resol diluted in methanol. The selected nanoclay was Cloisite® 30B. Two kind of nanocomposites were studied: the first one prepared at a nanoclay percentage equal to 5% and, the second one, produced at 20% nanoclay percentage. Finally, a comparison between these nanocomposites and a blend loaded with 20% of micrometric silica, was performed. The produced materials were studied by means of X‐ray diffraction, SEM and thermogravimetric analysis. The first nanocomposite showed a good degree of dispersion as well as distribution of the nanoclay platelets. SEM images even showed that high loaded nanocomposite exhibited a morphology very similar to a porous media. According to thermogravimetric analysis, if the thermal stability of the nanocomposites produced at 5% filler percentage wasn’t significantly better than the neat resol, then the degradative rate of 20% loaded nanocomposite was quite worse than the pristine resol.

Branched polymers Dextran‐graft‐Polyacrylamide and Dextran Sulphate‐graft‐Polyacrylamide copolymers with long polysaccharide backbone and various amount and length of PAA‐grafts were synthesised by radical polymerization using Ce(IV)/HNO3 redox system. It was established, that these copolymers have expanded conformation in solution and are able to intramolecular structure formation. Grafting efficiency is conditioned by amount of initiator and Dextran (or Dextran Sulphate) conformation in solution. It was shown that increase in content of copolymer Polyacrylamide component in Dextran Sulphate‐graft‐Polyacrylamide copolymers causes decrease in size of macromolecule due to blocking of polyion charge of main polysaccharide chain by counterions.

Flexible substrate displays are critical to organic electronics, e‐paper’s and e‐ink’s development. Many different types of materials are under investigation, including glass, polymer films and metallic foils. In this work we report a comparison study of polymer films as flexible substrates for polymer light emitting diodes (PLEDs) technology. The selected polymer substrates are two thermoplastic semi‐crystalline polymers (PET and PEN) and a high Tg material that cannot be melt processed (PAR). Firstly, the chosen films were characterized in morphology and optical properties with the aim to confirm their suitability for optoelectronic applications. Transmittance was analysed by UV‐Vis spectrophotometry and roughness by a surface profilometer. Finally, the surface energy of substrates (untreated and after UV‐ozone treatment) was estimated by contact angle measurements in order to evaluate their wettability for active materials deposition.

The large use of plastics in the world generates a large amount of waste which persists around 200 years in the environment. To minimize this effect is important to search some new polymer materials: the blends of biodegradable polymers with synthetic polymers. It is a large area that needs an intensive research to investigate the blends properties and its behavior face to the different treatments to aim at the biodegradation. The blends used in this work are: some biodegradable polymers such as: poly(hydroxybutyrate) (PHB) and poly(e‐polycaprolactone) (PCL) with a synthetic polymer, polypropylene (PP), in lower concentration. These blends were prepared using an internal mixer (Torque Rheometer), and pressed. These films were submitted to fungus biotreatment. The films analyses will be carried out by Fourier Transform Infrared (FTIR), UV‐Vis absorption (UV‐Vis), Scanning Electronic Microscopy (SEM), DSC and TGA.

Nitrogen oxides play a significant role in chemical processes taking place in an atmosphere and affect on an environment. The researches of the mechanism of nitrogen oxide reactions with polymers are important for evaluation of stability of these materials in polluted atmosphere. These researches can be also used for development of methods of the polymer modification, for example, for preparation of spin—labelled macromolecules. Most important for reactions with polymers are NO, NO2, NO3 as well as NO2 dimers. The features of the mechanism of reactions of these oxides with a number of polymers are considered. The especial attention is given to the mechanism of primary reactions of initiation and intermediate stages of complex radical processes under the action of nitrogen oxides. Nitric oxide does not react directly, but it recombines with free macroradicals formed in polymers by UV photolysis or γ—radiolysis. The nitro compounds formed in the subsequent reactions are converted into stable nitrogen—contai...

Polymer/clay nanocomposites show macroscopic properties depending on many factors but in particular on the morphology of the of the clay nanoparticles (intercalated, hybrid or exfoliated). The morphology is, in its turn, depending on the polymer/clay affinity and on the processing conditions. The flow involved in the melt compounding is the shear flow that can disaggregate the particles, but is not particularly efficient to induce the exfoliation if there is not a very good adhesion between polymer and clay. In this work we demonstrate that the elongational flow can induce the exfoliation in polymer/clay nanocomposite, even in presence of a very poor affinity between the two components. The mechanical properties are strongly increased both because of the orientation of the macromolecules, but also because of the exfoliation induced by the elongational flow.

Hyperbranched polymers are highly cascade branched polymers easily accessible via one‐pot procedure from ABm type monomers. A key property of hyperbranched polymers is their molecular architecture, which allows core‐shell morphology to be manipulated for further specific applications in material and medical sciences. Since the discovery of hyperbranched polymer materials, an increasing number of reports have been published describing synthetic procedures and technological applications of such materials, but their physical properties have remained less studied until the last decade.In the present work, different esterified hyperbranched polyglycerols have been prepared starting from polyglycerol precursors in presence of acetic acid, thus generating functionalization degree with range from 0 to 94%. Thermal analysis of the obtained samples has been studied by Differential Scanning Calorimetry (DSC). Dielectric Spectroscopy measurements have been analyzed by combining loss spectra deconvolution with the mod...

PVB sheet (type Butacite 3GO) with polymer chains containing butyraldehyde, hydroxyl‐ and small amount of acetate groups, was tested. These sheets were highly plasticized, with the content of plasticizer 28%. Studied material was tested at different kneading conditions; especially the influence of temperature, oxygen, mechanical energy and created heat of dissipation was studied.PVB sheet was kneaded at their usual humidity cca 0.5%. Because PVB in known as the material with high hydroscopity, next tests were done on PVB sheets macerated in water. By this operation the humidity of sheets increases to the content 8.0%. High humidity influenced all observed properties. Simultaneously, samples of PVB sheets re‐worked by calendaring and pressing. At the calendaring the sheets were thermally stressed. The calendaring represents shear stress at low temperature. The degradation was evaluated as the change of optical properties, like the light transmittance through the re‐worked material, created haze and yellowi...

The aim of this work was to investigate the foamability of high‐performance polymers (polyethersulfone, polyphenylsulfone, polyetherimide and polyethylenenaphtalate). Two different methods have been used to prepare the foam samples: high temperature expansion and two‐stage batch process. The effects of processing parameters (saturation time and pressure, foaming temperature) on the densities and microcellular structures of these foams were analyzed by using scanning electron microscopy.

It is well known that ionizing radiation can initiate polymerization of suitable monomers for many applications. In this work an epoxy dlfunctional monomer has been used as matrix of a carbon fibre composite in order to produce materials through gamma radiation, for aerospace and advanced automotive applications. Radiation curing has been performed at different absorbed doses and, as comparison, also thermal curing of the same monomer formulations has been done. Furthermore some Irradiated samples have been also subjected to a post Irradiation thermal curing in order to complete the polymerization reactions. The properties of the cured materials have been studied by moisture absorption isotherms, dynamic mechanical thermal analysis and mechanical flexural tests. © 2008 American Institute of Physics.