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Burning wood is estimated to produce about 6–10% of ash. Despite the possibility of recycling wood ash (WA), approximately 70% of the wood ash generated is landfilled, causing costs as well as environmental pollution. This study aims to recycle WA in an alternative way by inserting it as filler in geopolymeric materials. Here, metakaolin, NaOH, sodium silicate, and WA are used to realize geopolymers. Geopolymers without and with 10, 20 and 30% of WA are synthesized and characterized after 7, 14, 28 and 56 days. The article’s study methods are related to geopolymers’ chemical, biological and mechanical properties. The geopolymers synthesized are compact and solid. The pH and conductivity tests and the integrity and weight loss tests have demonstrated the stability of materials. The FT-IR study and boiling water test have confirmed the successful geopolymerization in all samples. The antibacterial analysis, the moss growing test and the compressive strength test have given a first idea about the durability of the materials synthesized. Furthermore, the compressive strength test result has allowed the comparison from the literature of the specimens obtained with the Portland cement (PC). The results obtained bode well for the future of this material.

In this paper the viscoelastic behavior of different soft adhesives with substantially similar adhesive performance is analyzed in the light of a Slip-Tube Model. In this model, the junction points between network chains and virtual chains are replaced by slip-links attached to fluctuating ends of virtual chains. The slip-links are allowed to slide along the contour of the network chains but not pass through each other. The predictions of the slip-tube model are in excellent agreement with the experimental data on uniaxial deformation of soft adhesive networks. Furthermore, the study shows that some adhesive performances can be described qualitatively by Small Amplitude Oscillatory Shear (SAOS), and the in-service properties can be described with adhesives with different viscoelastic spectra. Highly nonlinear uniaxial stretching tests reveal deeper insights into the description of the adhesives performances. Some well-established models are adopted and slightly modified by introducing the rate-dependence of their physical parameters to describe the response of soft adhesive to stretching.

A new method for calculating the retardation spectra for linear viscoelastic materials is presented. The method uses the analytical expressions among the viscoelastic functions through the numerical evaluation of the Inverse Laplace Transform (ILT) with the Gaver–Wynn–Rho (GWR) algorithm. It is applied to study three polymers' relaxation mechanisms: a star Polystyrene and two Polycyanurate networks with two different crosslink densities. The shear spectrum is de-convoluted to separate the segmental and the chain modes responsible for the softening dispersion. The retardation mechanisms extracted from the shear response are then compared with the volumetric bulk response. The results show that the shear segmental contribution is narrower than the volumetric bulk response and finishes about two decades before the shoulder's appearance in the shear retardation spectrum. Thus, the volumetric bulk response, mainly exerted by the segmental mode, is also affected at long times by the short time chain mechanism, usually claimed to be Sub-Rouse modes.

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.

Poly(meta-phenylene isophtalamide) (PMIA) was processed via electrospinning to provide nanofibrous membranes with randomly and aligned fibers. Mechanical performance of such membranes was evaluated, applying a normalization procedure that takes into account the peculiar morphology of such complex substrate where voids can sum up to almost 80% of the sample volume. Random and aligned fibers membranes are applied onto wood panels to test their fire resistance in cone calorimetry when coated in polyaramidic thin nanofiber mats. Tests highlighted that random fibers provide a better fire protection, increasing Time to Ignition and decreasing the Fire Performance Index. Another important parameter affecting the performance is the adhesive system used to apply the nanofibers onto wood that is able to significantly modify the fire performance of the polyaramidic-coated wood panels. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineers

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

This article presents the developmental process of a new tactile sensor. The sensor was based on the use of light-emitting diode (LED) phototransistor couples and a silicone rubber layer positioned above the optoelectronics devices. The optoelectronic components were organized in a matrix structure. For each couple, the LED illuminated the reflective surface, which coincided with the bottom facet of the deformable layer. Practically, the deformable layer transduced an external force into a displacement variation of its bottom facet through its stiffness. An external force applied to the deformable layer produced local variations of the bottom surface of the elastic material, and the couples of optical devices measured the vertical deformations in a discrete number of points. In particular, these vertical displacements produced a variation of the reflected light intensity and, accordingly, of the photocurrent measured by the photodetector. The realized prototype was designed and optimized through finite element analysis. A calibration procedure is also presented, whose results demonstrate the ability of the sensor to reconstruct the contact point and also the normal and tangential components of the contact force. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Polymer glasses are rheologically complex materials whose viscoelastic response is a function of the kinetics of structural relaxation. To circumvent the complexity, several experimental loading protocols have been established over the years, but the results have not led to a unifying concept. From a theoretical point of view, we tackled the problem by coupling the structural relaxation kinetics with the constitutive equation for linear viscoelasticity written in the reduced time domain. In this article, we substantiate the reliability of our approach. Geometrical descriptions and thermodynamic rules motivated a constitutive coupling of viscoelastic and structural relaxation phenomena, and that represents the novelty in our theory. The axial creep response is simulated following the thermal/mechanical loading sequence known as Struik's Protocol. Simulation is extended to a vanishing stress, and we showed that the time-aging time superposition procedure holds true above a given stress threshold. Furthermore, we extend our study to a single-step stress relaxation experiments to predict the glass densification that occurs in uniaxial tension (known as “volume implosion”) and compression. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 724–739, 2009

In this work the effect of melt mixing condition and of a trans-esterification catalyst on miscibility of poly(methyl methacrylate) (PMMA)/polycarbonate of bisphenol A (PC) blends is studied. In particular, at high temperature chemical reactions between PMMA and PC phases can take place; these strongly change the compatibility in the blend and materials having single Tg can be obtained. FT-IR analyses, coupled with solvent extraction, suggest that a grafting reaction of PC on PMMA is involved. SEC and DSC data are consistent with spectroscopic results, and some decrement of the molar weight distribution (MWD) of PC phase is observed. On the other hand, the presence of a fraction of modified material having higher MWD of starting PMMA is also noticed. The single Tg characteristic of some materials has been confirmed by experimental data of structural relaxation performed by differential scanning calorimetry (DSC). These materials showed optical clarity and the morphological analysis performed by scanning electron microscopy (SEM) confirm the homogeneity of these materials.

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.

Polymeric blends based on ethylene vinyl acetate (EVA) rubbers filled with high molecular weight carboxymethyl cellulose were investigated in view of possible employment as biodegradable materials. The effect of vinyl acetate (VA) content and of addition of transesterification agent to increase interaction between EVA and cellulosic components was considered. Blends reinforced with cellulose microfibers in different amounts were also characterized in their mechanical, rheological, and thermal behavior. POLYM. COMPOS., 36:980–986, 2015. © 2015 Society of Plastics Engineers

The origin of internal stresses in a polymeric component, subjected to an arbitrary cooling, will be described. The differential volume relaxation arising as a result of the different thermal history suffered by each body point was considered as the primary source of stresses build up. A numerical routine was developed accounting for the simultaneous stress relaxation processes and implemented within an Ansys® environment. The volume relaxation kinetics was modelled by using the four-parameter TNM (Tool-Narayanaswamy-Moynihan) phenomenological theory using the PVT (Pressure-Volume-Temperature) data obtained on a polystyrene sample. The numerical algorithm translates the specific volume theoretical predictions at each body point as applied non-mechanical loads acting on the component. Thermorheological complexity emerged due to coupling of volume and stress relaxation phenomena. A linear dependence of Poisson's ratio on the tensile relaxation modulus was postulated. A quantitative predictions of time dependent stress distribution was realized for two specific test cases.

The 2nd International Conference on “Times of Polymer” was held at the Congress Centre of the Continental Terme Hotel (Ischia, Italy) from the 20th to 23rd of June 2004. The Conference was organized by Prof. Alberto D'Amore (The Second University of Naples–SUN) and Prof. Domenico Acierno (University of Naples Federico II), as in its first edition. The Italian Associations of Materials (AIMAT) and Macromolecules (AIM), the Italian Society of Rheology and the National Institute of Materials Science and Technology (INSTM) sponsored the Conference and funding was received from INSTM and companies working within the area of research equipments (ATSFAAR; Belotti Strumenti, MP Strumenti, Perkin Elmer, Viscomate, Zwick/Roell-Italy).

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.

A comparison of the thermal properties of two classes of poly(D,L-lactic-glycolic acid) multiblock copolymers is reported. In particular, the results of differential scanning calorimetry, and thermogravimetric analysis of copolymers containing poly(ethylene glycol) (PEG) or diol-terminated poly(∈-caprolactone) (PCDT) segments are described. The influence of the chemical structure and the length of PEG and PCDT on thermal stability, degree of crystallinity and glass transition temperature (T g ) is discussed. Finally, an evaluation of the hydrolytic behavior in conditions mimicking the physiological environment is reported.

Tension-tension fatigue tests were conducted on unnotched injection moulded poly(phenylene ether ketone) (PEK-C) specimens with two stress ratios, R. The fatigue behaviour of this material is described. The S-N curves (S = alternating stress, N = number of cycles to failure) for different R values have the same general shape, but the curve for bigger R is shifted to long cycles. A fatigue lifetime inversion is observed from constructed S-N curves. Examinations of failure surfaces and analyses of the fatigue data reveal that the fatigue failure mechanism of the material studied is crack growth dominated. But the manner of the fatigue crack initiation and propagation depends on the maximum cyclic stress applied. At higher stresses, the fatigue crack originates at the corner of the specimen and propagates inward; at lower stresses, the fatigue crack nucleates at an internal flaw of the specimen and propagates outward. The fatigue lifetime inversion corresponds to the transition of crack initiation and propagation from one mode to the other.

The effect of physical aging at 210 degrees C on the mechanical properties of phenolphthalein polyether sulfone (PES-C) and a PES-C/poly(phenylene sulfide) (PPS) blend, with 5% content of PPS, were studied using DMA, tensile experiments, an instrumented impact tester, and SEM observations. The blend shows good mechanical properties in comparison with the corresponding PES-C. The mechanical properties of both materials exhibit characteristics of physical aging, with only the aging rate of the blend relatively slower, which should be attributed to the constraint effect of PPS particles and the good interfacial adhesion. The morphology of the PPS phase in the blend did not change with aging time. The principal role of PPS particles is to induce crazes, which dissipate energy, under applied loading; thus, the blend shows good toughness. On the other hand, the multiple crazing mechanism depends on the molecular mobility or structural state of the matrix. (C) 1996 John Wiley & Sons, Inc.

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 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.

The scaling law for relaxation times (τ's) recently proposed by Casalini and Roland was used in the framework of Kovacs, Aklonis, Hutchinson, and Ramos phenomenological theory. With this approach, it was shown that both the isobaric and the isothermal glass transitions of polystyrene can be reliably predicted with only two fitting parameters, namely, τ in the reference state and the fractional exponent that describes the dispersion of the α relaxation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Diglycidyl terminated 4,4′-oxydiphenyl cured with an aromatic diamine exhibits liquid crystalline properties, even if the amount of hardener is used in defect with respect to the stoichiometric amount. Physical properties of the resin, hardened with different quantities of amine are presented and discussed. In particular the high values of fracture toughness of this class of thermoset has been explained on the basis of the biphasic nature of the crosslinked resin.The differences in mechanical properties are analyzed taking into account the different crosslink densities.

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.

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.

The viscoelastic properties of the amorphous and semicrystalline PEEK and of a PEEK-based composite (APC2) have been analyzed as a function of the aging time and related free volume relaxation, at temperatures close to the glass transition temperature. The effect of thermal treatments (physical aging) on the polymer amorphous phase of the three systems is presented. Creep tests approaching the “zero stress” were performed on samples subjected to different thermal histories. The presence of a second phase, namely crystallites and fibers, determines a loss of the mobility of the polymeric amorphous chains and consequently a decrease of the rate of free volume relaxation.

The behavior of the wing of an aircraft is characterized by the complex interaction among dynamic (distribution of the masses), elastic (ownership of the materials) and aerodynamic (shapes, forces and moments) phenomena. As a rule it is expected from us that the aerodynamic actions damp the oscillations (natural or forced) of the wing. However, above given speeds a lot of undesired aero-elastic phenomena, among which the divergence of the wings, occur and became of considerable importance in view of safety. To potentially prevent dangerous situations, generally the speed of the aircraft is limited; a possible alternative is to endow the “system wing” of proper devices (passive or active, i.e. controls) in order to prevent that the energy transfer of aerodynamic actions amplifies its instability. The forward swept wings are extremely efficient in terms of aerodynamics performance (stall and supersonic behavior) and therefore of maneuverability of the aircraft, even if, unfortunately, they are extremely critic under the profile of the aero-elastic stability. The solution of the technical-scientific and technological problems associated with the use of innovative configurations of wings prefigures a meaningful breakthrough in the international aerospace sector. Within this work the authors aim to determine a particular configuration of composite material for the realization of a forward swept wing in such a way that, under the action of the effective aerodynamic loads, the wings structural response provides a coupled bending-torsion deformations with stability effects. It will be shown that by using a recursive analysis of the composite lay-up one can tailor the overall bending/torsion deformation ratio value.

Organic-inorganic hybrid materials with excellent heavy metal ions chelating properties are synthesized by covalent bonding of multifunctional polymers of polyamidoamine (PAA) type onto silica. Two series of polyamidoamine-silica hybrid materials differing in the PAA chemical structure are prepared and their thermal properties are investigated. Differential Scanning Calorimetry (DSC) is used to study the effects of chain immobilization and ion chelation on the glass-transition temperature (Tg) of the polymers. The Tg of PAA-hybrid materials is elevated with respect to ungrafted PAAs, but when the linear and the corresponding hybrid PAAs are in the complex form with metal ions such as Cu2+ and Co2+, the materials arrive to the decomposition temperature and no Tg is detected. To highlight the effect of metal ion on the molecular mobility of these systems, an oligomeric plasticizer is added. The behaviour in the Tg region is analyzed and discussed in term of Tool-Narayanaswamy-Moynihan (TNM) model. In particular the apparent activation energy (Δh*) is used to discuss overall segmental co-operativity in order to better understand the effect of complex formation on structural mobility.

Statistical copolycarbonates containing different bisphenol A/tetramethyl bisphenol A (BPA/TMBPA) molar ratios were synthesized by polycondensation reaction between a mixture of the two bisphenols and phosgene. The reaction conditions were selected for producing polymers having comparable molecular weights (M n ≃ 9000 g/mol) but different composition, and the same composition but different molecular weights. The calorimetric properties of the products were investigated by differential scanning calorimetry (DSC) and dynamical-mechanical thermal analysis (DMTA). In particular, the effect of the copolymers molecular characteristics on the glass transition temperature (Tg) and the related relaxation processes were studied. DMTA was employed for evaluating the effect of macromolecular structure on the γ low temperature relaxation peak.

Mass-variation measurements were carried out on carbon black (CB)-poly(vinyl chloride) (PVC) composite film with 40% by weight of di(2-ethylhexyl)-phthalate (DOP), cast on resonant piezo-layer (RPL) elements of lead zirconat titanate (PZT). Even if anomalous diffusion is predicted by fitting the data with M t /M∞=kt α , the fractional uptake M t /M∞ is linear with the square root of the time up to M t /M∞=0.6, suggesting Fickian behavour. The anomalous values of a are probably due to experimental time lag. A dependence of the diffusion on the morphology of the material and the penetrant shape and flexibility has been found.

Binary blends based on poly(vinyl chloride) (PVC) were prepared both by casting from tetrahydrofuran (THF) and by mixing in the melt form, in a discontinuous mixer, PVC and multi-block copolymers containing poly(e-caprolactone) (PCDT) and poly(ethylene glycol) (PEG) segments. PCDT-PEG copolymers were synthesized using a polycondensation reaction where the α,ω-bis-chloroformate of an oligomeric poly(e-caprolactone) diol terminated (PCDT) and oligomeric PEG were employed as macromonomers. For comparison purposes, blends PVC with starting oligomers as well as with mixtures containing a typical low molecular plasticizer, dioctylphthalate (DOP), were also prepared. The copolymer miscibility was studied by differential scanning calorimetry (DSC) and FT-IR spectroscopy. The blend morphology was investigated by polarized light microscopy (PLM). A higher miscibility with PVC was observed for copolymers compared to PEG.

Thermodegradative investigations of two classes of multi-block copolymers containing poly(D,L-lactic-glycolic acid) (PLGA) and either poly(ethylene glycol) (PEG) or poly(e-caprolactone) diol-terminated (PCDT) segments were performed. In particular, the influence of the type and length of the segments as well as of the molar ratio between the D,L-lactic acid (LA) and glycolic acid (GA) residues was investigated at 180°C in air by viscometry, FT-IR analysis and isothermal thermogravimetry. The thermal oxidative degradation of these materials is largely affected by the LA/GA ratio, a higher LA content generally imparting higher stability. The FT-IR analysis suggests that, depending on the composition of the PLGA segments, degradative processes are triggered which can lead to a preferential degradation of the blocks.

A new process was developed which enables one to obtain surface-modified silica with a high heavy metal ion complexing ability. The synthetic approach is based on grafting of vinyl-terminated macromonomers onto silica via covalent bonding. A proper selection of the macromonomer structure, molecular weight, and molecular weight distribution allows materials to be obtained with a range of desirable properties. The process has been tested on various dispersions (ranging from 35 and 200 μm) of silica particles and two structurally related macromonomers. Native silica and the resulting mixed organic–inorganic products were fully characterized by IR spectroscopy, SEM, yield of grafting (elemental analysis and calcination), density (helium pycnometry), specific surface area (BET method), and pore size (gas adsorption and mercury porosimetry) measurements. It was found that the corresponding polymers are effectively grafted onto the surface; the density, surface area, and pore size of the silica particles decrease with polymer grafting. Preliminary results on metal-ion uptake indicate that polymer-grafted silica exhibits an excellent complexing ability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1287–1296, 2002

The thermogravimetric analysis (TGA) of two classes of multi-block copolymers based on poly( d , l -lactic-glycolic acid) (PLGA) and diol-terminated poly(e-caprolactone) (PCDT) or poly(ethylene glycol) (PEG) segments is reported. These materials, having the structure of poly(ester-carbonate)s, were synthesized by a chain extension reaction. The influence of the length of PCDT or PEG segments and of the molar ratio of d , l -lactic acid (LA) and glycolic acid (GA) residues on thermal stability in air and nitrogen atmosphere has been investigated. For comparison purposes the degradation behaviour of starting oligomers was also studied. TGA under nitrogen shows two degradation processes that can be ascribed to the PLGA and PCDT or PEG segments, respectively. In addition, the thermal stability increases with the LA content in the PLGA blocks. In the tests run under air two degradation steps have also been observed, though the former occurs in general at higher temperatures.

Polymers capable of responding to both temperature and pH changes were synthesised by radical copolymerisation of N-isopropylacrylamide (NIPAAm) and N-methacryloyl- l -leucine (MALEU) in different NIPAAm/MALEU molar ratios (15:1, 10:1, 2:1 and 1:1). The polymers were characterised by Size Exclusion Chromatography, acid–base titrations, FT-IR and 1H-NMR analyses. Their solution behaviour was studied in 0.1 M NaCl and in citrate buffers (pH 4.0, 4.5, 5.0 and 6.0). At pH 4.0 and 4.5 the cloud point temperature (TCP) of copolymers was depressed proportionally to their MALEU content. In contrast, at pH 5.0 and 6.0 the phase transition temperature increased linearly. The behaviour of the copolymers with NIPAAm/MALEU ratios 15:1 and 10:1 was investigated also between pH 3 and 11 in 0.1 M NaCl. In both cases a sharp increase in TCP was observed around pH 4–5. The TCP vs. pH curve was linearised and the acidity constants were determined by the linearisation procedure. Furthermore, it was possible to demonstrate that the phase transition temperature increases linearly with the ionic content of the polymers.

The use of Wilhelmy plate techniques for studying the interactions of fibers with fluids of variable viscosity is discussed. The influence of hydrodynamic effects of force (F) VS. DEPTH (z) plots is interpreted on the basis of surface tension-independent added terms of the constitutive equation of the Wilhelmy experiment. Wetting experiments using pseudoplastic fluids (polyethyleneglycol/water solution) show that viscoelasticity is indeed important in the interpretation of Wilhelmy plate experiments. The comparison of wetting experiments performed on untreated and plasma-treated carbon fibers showed that at low stage speed and fluid viscosity, surface chemistry and morphology determines contact angles. At higher stage speeds and viscosities and advancing and receding angles are affected by surface chemistry-independent and hydrodynamics-dependent added contributions.

The loss of orientation is a much more rapid phenomenon than the thermal shrinkage of drawn polystyrene, as shown by birefringence and FTIR measurements. The properties imparted by the orientation can be lost before the complete shrinkage occurs. The implications of this fact are discussed.

Analyse transitoire (fluage sous flexion dans diverses conditions) et dynamique rigidite au voisinage de la temperature de transition vitreuse

Thermal treatment of amorphous poly(aryl-ether-ether ketone) below the glass transition temperature has been studied. The extent of aging was measured by differential scanning calorimetry. X-ray and Fourier transform infrared spectra were used to study both melt-cast and annealed samples. The effect of the thermal treatment of viscoelastic response was evaluated using creep tests. Aging has been shown to be accompanied by a marked change in the transport properties of the material.

Dynamic-mechanical and dielectric characterization of the cold crystallization of PEEK has been performed in order to develop a non-destructive evaluation method of crystallinity in thermoplastic matrices. The Avrami approach is applied here to describe the Poly(ether ether ketone) (PEEK) crystallization kinetics after an appropriate reduction of dynamic-mechanical and dielectric parameters. Avrami exponents obtained from dielectric characterization are comparable with those obtained with DSC measurements reported in literature, while the exponents obtained from the dynamic-mechanical characterization are higher, reflecting also changes in the aspect ratio of the growing crystals. Variations in the glass transition temperature detected during cold crystallization are analyzed and analogies between PEEK and PET are discussed.

The empirical model recently found by the authors for the prediction of the indentation depth was verified for composite laminates different in matrix and fiber subjected to low velocity impact loads. The data obtained in a previous research on common glass and carbon fiber laminates made by commonly used epoxy matrix, were here compared to the results obtained on laminates made by glass fibers immersed in phenolic matrix and novel basalt fibers immersed in epoxy resin. The model takes into explicitly account the tup diameter and presents the advantage that only a single material constant to be experimentally determined is necessary for the prediction. The comparison showed that the value of the constant is different for the different material systems analyzed so that it can be assumed as an index for the indentation sensitivity. POLYM. COMPOS., 36:987–991, 2015. © 2015 Society of Plastics Engineers