Mobility Of Macromolecular Chains Research Articles

POLYMERIC MATERIALS BASED ON ACRYLIC MONOMERS WITH ADJUSTABLE SUSTAINABILITY

Increased intensity of operation of construction infrastructure, unfavorable for quality repairs of natural and climatic conditions of Ukraine and a high probability of emergencies necessitate the need for domestic import-substituting structural composites for restoration work with regulated viability. The specifics of repair and restoration works - limited time, extreme temperature and humidity conditions, problems in ensuring full-fledged technology and others. - makes it necessary to develop PKM that take into account these features. The authors state that such compositions can be developed on the basis of acrylic binders, mainly methyl methacrylate (MMA), polymer composite materials (PCM) based on which are characterized by high rates of strength, mechanical and physicochemical properties, as well as durability. comprehensive study of the influence of the conditions of formation of the polymer material (curing temperature) and prescription-technological factors (chemical modification of the binder, the method of introduction of benzoyl peroxide, etc.) on its strength. Effective means of increasing the latter have been identified. To assess the effect of the studied modifiers on the change in the mobility of macromolecular chains by linear dilatometry, the glass transition temperatures Tc (° C) of PM polymer matrices were determined (decrease in glass transition temperature is usually associated with increased mobility of polymer chain segments). It was found that among a number of studied modifiers - 3-methacryloxypropyltrimethoxylan (MPTMS), glycidyl methacrylate (GMA), dimethacrylate ether of triethylene glycol (TGM-3), hydroxypropyl methacrylate (GPMA) (the two most effective) (methacrylate). The expediency of adjusting the content of PB and DMA to accelerate the set of strength at low positive and negative curing temperatures is shown. The optimal contents of PB and DMA have been established, which allow to reduce the time of reaching the minimum operational (40 MPa) and ultimate strength for bending of PM based on MMA. Keywords: acrylic monomer, manufacturability, strength set of acrylic systems, modification with acrylic derivatives.

Study of the Effect of Physical Aging on the Polylactic Acid by Thermal and Optical Techniques

In this work, we investigated the influence of physical aging on polylactic acid (PLA) films using thermal and optical techniques; Differential Scanning Calorimetry (DSC), Thermally Stimulated Depolarization Current (TSDC), and Attenuated Total Reflection Spectroscopy (ATR). The PLA films were aged for different periods: 60, 90, and 120 minutes at a temperature Ta= 43 °C. The result obtained by DSC showed that the effect of physical aging appeared as an endothermic peak, which increased with increasing aging time and evolved towards higher temperatures. TSDC results showed a thermal current peak located between 30 and 80 ° C, which represented the main relaxation mode (α relaxation) of the dielectric manifestation of the glass transition. The intensity of this peak decreased and was shifted to higher temperatures when aging time increased, this result can be explained by a decrease in the molecular mobility of macromolecular chains due to the decrease in the free volume. The effect of physical aging on the PLA by the ATR technique showed a gradual decrease in all absorption bands during the aging period. In particular, the wide absorption band between 3000 and 3700 cm-1attributed to the hydroxyl group (OH), which disappeared after two hours of aging

Novel Poly(Vinylidene Fluoride)/Montmorillonite Polymer Inclusion Membrane: Application to Cr(VI) Extraction from Polluted Water.

Novel hybrid polymer inclusion membranes (PIMs) based on poly(vinylidene fluoride) (PVDF) (polymer matrix) and Aliquat 336 (ion carrier) and containing native sodium (Cloisite Na+ (CNa)) and organo-modified (Cloisite 30B (C30B)) Montmorillonites were elaborated and tested for the removal of toxic Cr(VI) ions from the aqueous solution. The influence of the nanoclay incorporation on the physicochemical properties of PVDF-based PIMs was studied and the resulting membrane transport properties of the Cr(VI) ions were investigated in detail. The water contact angle measurements reveal that the incorporation of the CNa nanofiller affects the membrane wettability as less hydrophilic surface is obtained in this case—~47° in the presence of CNa as compared with ~15° for PIMs with C30B. The membrane rigidity is found to be dependent on the type and size of the used Montmorillonite. The increase of Young’s modulus is higher when CNa is incorporated in comparison with C30B. The stiffness of the PIM is strongly increased with CNa amount (four times higher with 30 wt %) which is not the case for C30B (only 1.5 times). Higher Cr(VI) permeation flux is obtained for PIMs containing CNa (~2.7 µmol/(m2·s)) owing to their porous structure as compared with membranes loaded with C30B and those without filler (~2 µmol/(m2·s) in both cases). The PIM with 20 wt % of native sodium Montmorillonite revealed satisfactory stability during five cycles of the Cr(VI) transport due to the high membrane rigidity and hydrophobicity. Much lower macromolecular chain mobility in this case allows limiting the carrier loss, thus increasing the membrane stability. On the contrary, a deterioration of the transport performance is recorded for the membrane filled with C30B and that without filler. The obtained results showed the possibility to extend the PIM lifetime through the incorporation of nanoparticles that diminish the carrier loss (Aliquat 336) from the membrane into the aqueous phase by limiting its mobility within the membrane by tortuosity effect and membrane stiffening without losing its permselective properties.

Micro-DSC, FTIR-ATR and NMR MOUSE study of the dose-dependent effects of gamma irradiation on vegetable-tanned leather: The influence of leather thermal stability

Leather artefacts, archaeological, historical or modern, are prone to microbiological attack which could lead to irreversible degradation. Previous studies performed on new leather mock-ups indicated good resistance of leather at doses up to (25–50) kGy. The aim of this research is to improve our understanding about the changes in the thermal stability and structural order of collagen within vegetable-tanned leather exposed to gamma irradiation. Variously vegetable-tanned leather samples were therefore exposed to irradiation with Co-60 gamma-rays with increasing doses (10–100 kGy) and the dose-dependent effect on collagen-tannin matrix was investigated using micro-DSC, the best technique for determining proteins' thermal stability, coupled with FTIR-ATR and NMR MOUSE spectroscopy, to enhance the analytical coverage of the calorimetric profile. FTIR-ATR technique revealed the very subtle changes in collagen at the molecular (lower order) level by, which are reflected in the properties of the structures with a higher level of order, namely the hydrothermal stability of fibrils (measured by micro-DSC) and mobility of macromolecular chains (determined by NMR MOUSE). It was proved that a 10 kGy dose causes significant variation on collagen molecular structure, fibrils hydrothermal stability, and macromolecular chain's mobility when the collagen-tannin matrix is already thermally destabilized and present a wide distribution of collagen populations with distinct thermal stability. On the other hand, leathers characterized by high thermal stability and homogeneous distribution of collagen populations better withstood radiation up to either 25 kGy or 50 kGy, depending on the collagen-tannin interactions' strength. This protocol, with high analytical and diagnostic sensitivity, can thus be applied to characterize a broader range of collagen materials sterilized/crosslinked with gamma radiation.

Copernicia Prunifera Leaf Fiber: A Promising New Reinforcement for Epoxy Composites.

A basic characterization of novel epoxy matrix composites incorporated with up to 40 vol% of processed leaf fibers from the Copernicia prunifera palm tree, known as carnauba fibers, was performed. The tensile properties for the composite reinforced with 40 vol% of carnauba fibers showed an increase (40%) in the tensile strength and (69%) for the elastic modulus. All composites presented superior elongation values in comparison to neat epoxy. Izod impact tests complemented by fibers/matrix interfacial strength evaluation by pullout test and Fourier transformed infrared (FTIR) analysis revealed for the first time a significant reinforcement effect (> 9 times) caused by the carnauba fiber to polymer matrix. Additional thermogravimetric analysis (TG/DTG) showed the onset of thermal degradation for the composites (326 ~ 306 °C), which represents a better thermal stability than the plain carnauba fiber (267 °C) but slightly lower than that of the neat epoxy (342 °C). Differential scanning calorimetry (DSC) disclosed an endothermic peak at 63 °C for the neat epoxy associated with the glass transition temperature (Tg). DSC endothermic peaks for the composites, between 73 to 103 °C, and for the plain carnauba fibers, 107 °C, are attributed to moisture release. Dynamic mechanical analysis confirms Tg of 64 °C for the neat epoxy and slightly higher composite values (82–84 °C) due to the carnauba fiber interference with the epoxy macromolecular chain mobility. Both by its higher impact resistance and thermal behavior, the novel carnauba fibers epoxy composites might be considered a viable substitute for commonly used glass fiber composites.

Effects of pressure on poly(ether‐ether‐ketone) (PEEK) sintering mechanisms

ABSTRACTThis study deals with the understanding of the sintering mechanisms that occur during consolidation of an ultra‐high‐performance polymer: poly(ether‐ether‐ketone). In particular, we investigated the effects of uniaxial pressure during spark plasma sintering (SPS) processing. Glass‐transition temperature (Tg) measurements under loading, stress–strain curves and scanning electron microscopy analysis allowed us to determine the role of pressure intensity and temperature of application on macromolecular chain mobility in both the bulk and the surface of the particles. First, a loss of chain mobility in the bulk of the particles was observed under high pressure. Second, it was shown that high pressure applied at low temperature leads to friction effects between the particles which enhances chain mobility in the particle shell through a local melting phenomenon. These experimental conditions favor the healing of particles and high cohesion was then observed in the resulting sintered samples. The level of friction is enhanced when pressure is applied at a low temperature since the powders are still in a glassy state. Finally, the achievement of cohesive grain boundaries was found to be related to the location and conformation of chain ends. Good healing between particles can only occur if a sufficient number of chain ends are available at the surface of the particle shell. We showed that the native powder state plays a significant role. The direct use of as‐received powder leads to final material exhibiting good cohesion whereas pretreatments of the native powder are highly detrimental. It should be noted that this processing does not affect the high initial degree of crystallinity because no bulk melting is observed during consolidation by sintering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47645.

Rheological and thermal behavior of Tunisian clay reinforced recycled polypropylene composites

AbstractIn the present paper, the influence of Tunisian clay filler on rheological and thermal behaviors of based recycled polypropylene (RPP) composites is investigated. RPP was mixed with 1, 3, 5, and 7 wt% of Tunisian clay particles using twin‐screw extruder. Maleic anhydride‐grafted polypropylene (PP‐g‐MA) was used as a compatibilizer. The morphological, structural, rheological, and thermal properties of raw and composite materials were analyzed. Scanning electron microscopy results showed that with the incorporation of clay and PP‐g‐MA, the particles were uniformly dispersed into RPP/PP‐g‐MA/clay composites. FTIR analysis showed that clay particles altered the shape of the observation band of RPP, indicating the presence of a chemical interaction between the clay and RPP matrix. The increased storage and loss moduli indicated that the Tunisian clay had a reinforcing effect on the RPP matrix. In differential scanning calorimetry analysis, crystallization temperature (Tc) increased with clay content, indicating that the addition of Tunisian organoclay accelerated the crystallization of the RPP matrix. The slight decrease in melting temperature (Tm) with increasing clay loading could be due to PP‐g‐MA, which affects the mobility of macromolecular chains.

Yield stress changes induced by water in polyamide 6: Characterization and modeling

This paper considers the effect of water content on mechanical properties of polyamide 6 when used in a humid environment. First an experimental section presents the tensile behavior of polyamide with different amounts of water, with and without a through-thickness water gradient. Water profiles are introduced by immersion in sea water at 25 °C. The effect of testing temperature is also investigated in order to consider the influence of macromolecular chain mobility on the mechanical behavior. Then, in a second section, modeling of yield stress is proposed based on physical considerations. This can be used for life time prediction of PA6 in humid environment when plasticization is the main degradation mechanism.

Dielectric characterization of Indonesian low-rank coal for microwave processing

The present study aims to provide a preliminary guide for microwave processing of low-rank coals by investigating the dielectric characteristics of an Indonesian low-rank coal based on determination of its permittivity from 21°C to approximately 1000°C at 915 and 2450MHz in argon. The results show that the relative dielectric constant of the coal gradually decreases with increasing temperature below 200°C due to dewatering. It then has a considerable increase up to 750°C because of devolatilization and carbonization, preceded by a slight decrease due to physical-chemical and chemical processes connected with the mobility of macromolecular chains of the coal. Thereafter, it increases with a declined rate ascribed to the coal's continuous structure transformations. The dielectric loss factor shows a similar variation, except the presence of the “dielectric loss peak” at about 600°C, associated with rise of microwave loss. The microwave penetration depth of the coal presents a depth peak at approximately 400°C, indicating potential application of variable frequency microwave heating to large-scale processing. The reflection loss (RL) patterns reveal the strong coal slab thickness dependences of magnitude and location of absorption peaks in the range 0.02–0.20m, with minimum RL values of −42.39dB and −47.92dB obtained at thicknesses of 0.16 and 0.06m at 915 and 2450MHz, respectively. This dissimilarity is primarily attributed to the different dielectric parameters and wavelengths at these frequencies. Microwave heating functions sufficiently in a narrow temperature range from about 500 to 700°C, in which target temperature can be selected for efficient coal processing.

Carbon Deposition from Aromatic Solvents onto Active Intact 3d Metal Surface at Ambient Conditions

The process of carbon deposition onto 3d metal surface immersed in aromatic solvents (benzene, toluene, xylene) at ambient conditions was studied for as-prepared magnetic nanoparticles (MNPs) and Fe-based films by thermal analysis, mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and energy-dispersive X-ray spectroscopy. The mechanism of the deposition at the interface is likely the heterogeneous Scholl oxidation of the aromatic hydrocarbons, which is the cationic polymerization of the aryl rings. It results in the formation of polycyclic aromatic hydrocarbons (PAH) chemically bonded to the surface of a MNP or thin metallic film. The benzene rings in the polycyclic deposit do not maintain planar aligned structures and do not provide delocalization of the π-electrons in the zone structure. Contrary to the dense graphite layers, the polycyclic layers, although chemically bonded, are not attached tightly to the surface. Such "hairlike" structure of the carboneous deposit might be especially favorable for the applications that imply the enhanced interaction at the surfaces incorporated in the functional matrices (polymeric composites or biosensors). The aromatic chemical nature of the deposit provides strong interaction with most polymers, while its loose structure favors conformational mobility of macromolecular chains at the interface.

Functionalization of polyvinyl alcohol hydrogels with graphene oxide for potential dye removal

ABSTRACTBecause of highly frozen macromolecule chains, polyvinyl alcohol (PVA) hydrogels have never been used for dye removal. This work focuses on improving the adsorption capacity of the PVA hydrogel by using amphiphilic graphene oxide to improve its macromolecular chain mobility in crystal domain and introduce new functional groups. To evaluate its effectiveness, crystal structure, swelling kinetics, and model dye methylene blue (MB) adsorption of the as‐prepared PVA hybrid hydrogels were systematically investigated. The results indicate that the hybrid PVA hydrogels have lower crystallinity and less crystal stability, demonstrating the improved macromolecular chain mobility. Moreover, improved swelling ratios of PVA/GO hydrogels also illustrate the enhanced macromolecular chain mobility. MB adsorption experiment indicates that GO introduced can result in great improvement in MB adsorption. And the adsorption process follows the second‐order kinetic model and Morris–Weber model, which is determined by the intraparticle diffusion. Furthermore, MB adsorption isotherm follows Freundlich model and the adsorption is heterogeneous. Desorption studies indicate that the interaction between PVA hydrogels and MB consists of both physisorption and chemisorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39872.

Plasticization effect of triacetin on structure and properties of starch ester film

The aim of this work was to evaluate the plasticizing effect of triacetin on the structure and properties of starch ester film and further establish the structure–property relationships. The presence of triacetin resulted in multiple structure changes of the film. The mobility of macromolecular chain was increased to form scattered crystallite during the film formation process. The amorphous region was enlarged to contain more triacetin squeezed from crystalline region. The plasticization of triacetin and restriction of crystallite oppositely influenced the mobility of macromolecular chains in different regions. The thermal stability of triacetin changed along with its fluctuant interaction with macromolecules. Comparatively, the enhanced ether bond and the restriction from crystalline regions on the mobility of the amorphous chain consequently improved the thermal stability of the film matrix. The interaction between triacetin and starch ester was essential to film forming but unexpectedly lowered the triacetin stability.

Thermomechanical behavior of shape memory elastomeric composites

Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape in response to environmental stimuli such as heat, electricity, or irradiation. Most thermally activated SMPs use the macromolecular chain mobility change around the glass transition temperature ( T g ) to achieve the shape memory (SM) effects. During this process, the stiffness of the material typically changes by three orders of magnitude. Recently, a composite materials approach was developed to achieve thermally activated shape memory effect where the material exhibits elastomeric response in both the temporary and the recovered configurations. These shape memory elastomeric composites (SMECs) consist of an elastomeric matrix reinforced by a semicrystalline polymer fiber network. The matrix provides background rubber elasticity while the fiber network can transform between solid crystals and melt phases over the operative temperature range. As such it serves as a reversible “switching phase” that enables shape fixing and recovery. Shape memory elastomeric composites provide a new paradigm for the development of a wide array of active polymer composites that utilize the melt–crystal transition to achieve the shape memory effect. This potentially allows for material systems with much simpler chemistries than most shape memory polymers and thus can facilitate more rapid material development and insertion. It is therefore important to understand the thermomechanical behavior and to develop corresponding material models. In this paper, a 3D finite-deformation constitutive modeling framework was developed to describe the thermomechanical behavior of SMEC. The model is phenomenological, although inspired by micromechanical considerations of load transfer between the matrix and fiber phases of a composite system. It treats the matrix as an elastomer and the fibers as a complex solid that itself is an aggregate of melt and crystal phases that evolve from one to the other during a temperature change. As such, the composite consists of an elastomer reinforced by a soft liquid at high temperature and a stiff solid at low temperature. The model includes a kinetic description of the non-isothermal crystallization and melting of the fibers during a temperature change. As the fibers transform from melt to crystal during cooling it is assumed that new crystals are formed in an undeformed state, which requires careful tracking of the kinematics of the evolving phases which comes at a significant computational cost. In order to improve the computational efficiency, an effective phase model (EPM) is adopted to treat the evolving crystal phases as an effective medium. A suite of careful thermomechanical experiments with a SMEC was carried out to calibrate various model parameters, and then to demonstrate the ability of the model to accurately capture the shape memory behavior of the SMEC system during complex thermomechanical loading scenarios. The model also identifies the effects of microstructural design parameters such as the fiber volume fraction.

UV-waterborne polyurethane-acrylate nanocomposite coatings containing alumina and silica nanoparticles for wood: mechanical, optical, and thermal properties assessment

The effect of alumina and silica nanoparticles on mechanical, optical, and thermal properties of UV-waterborne nanocomposite coatings was investigated. The addition of nanoalumina and nanosilica was shown to decrease the hardness because of nanoparticle aggregation. In comparison to the neat coating and despite the presence of aggregates, the scratch resistance of nanocomposite coatings was significantly improved. As expected, the gloss of UV-waterborne coatings was reduced following the addition of nanoparticles due to an increase of the surface roughness. Alumina and silica nanoparticles were found to enhance the glass transition temperature of PUA nanocomposite coatings by hindering the mobility of macromolecular chains at the interface around the nanoparticles. Finally, the interest and efficiency of grafting trialkoxysilanes was demonstrated with the study of nanosilica behavior. Not only was the dispersion of nanosilica enhanced following trialkoxysilanes grafting onto silica nanoparticles, but also the scratch resistance and the adhesion of UV-waterborne coatings containing nanosilica markedly increased even with 1 wt% content. Silica which is recommended in the wooden furniture and kitchen cabinet manufacturing industry as nano-reinforcement provides improved properties well suited in surface coating applications to efficiently protect surface of wood substrates.

PLA nanocomposites: Effect of filler type on non-isothermal crystallization

Nanocomposites of poly( l-lactic acid) (PLA) with fumed silica nanoparticles (SiO 2), montmorillonite (MMT) and oxidized multi-walled carbon nanotubes (o-MWCNTs), containing 2.5 wt% nanoparticles were prepared, by solved evaporation method. SEM micrographs evidenced fine dispersion of the nanoparticles into PLA matrix. This has as result to act as efficient reinforcing agents increasing the storage modulus, as was verified from DMA analysis. The nanoparticles were found to be effective nucleaging agents in cases of silica nanoparticles and MWCNT. On cooling from the melt crystallization was accelerated by the presence of nanoparticles and the effective activation energy calculated using the isoconversional method of Friedmann decreased. The nucleation activity was calculated. Cold-crystallization was also affected by the presence of nanoparticles. However, it seems that the phenomenon begins at lower temperatures and this results in formation of imperfect crystalline structure which reduce macromolecular chain mobility of the remaining amorphous polymer, finally limiting the ultimate crystallinity.

The role of clay network on macromolecular chain mobility and relaxation in isotactic polypropylene/organoclay nanocomposites

It is well known that a so-called “three-dimensional filler network structure” will be constructed in the polymer/layered silicate nanocomposites when the content of layered clay reaches a threshold value, at which the silicate sheets are incapable of freely rotating, due to physical jamming and connecting of the nanodispersed layered silicate. In this article, the effect of such clay network on the mobility and relaxation of macromolecular chains in isotactic polypropylene(iPP)/organoclay nanocomposites was investigated in detail with a combination of DMTA, DSC, TGA, TEM, rheometry and melt flow index measurements. The main aim is to establish a relationship between the mesoscopic filler network structure and the macroscopic properties of the polymer nanocomposites, particularly to explore the role of the clay network on the mobility and relaxation of macromolecular chains. It was found that the nanodispersed clay tactoids and layers play less important or dominant roles on the mobility of iPP chains depending on the formation of percolating filler network. The turning point of macroscopic properties appeared at 1 wt% organoclay content. Before this point, the effect of organoclay can be negligible, and the increase of chain mobility was ascribed to the decrease of molecular weight of polymer chains, as commonly occurs during dynamic melt processing; after this point, however, a reduced mobility of chains and a retarded chain relaxation were observed and attributed to the formation of a mesoscopic filler network. The essential features of such a mesoscopic organoclay network were estimated and discussed on the basis of stress relaxation and structural reversion measurements. A schematic model was proposed to describe the different relaxation and motion behaviors of macromolecular chains in the unfilled polymer and the filled hybrids with partial and percolated organoclay networks, respectively.

Cross‐linking of polybutadiene: correlation between solid‐state 1H NMR spectroscopy, thermoporosimetry, densimetry and crystallinity measurements

AbstractT2 proton NMR relaxation times were used to follow the changes in the macromolecular chain mobility of a chemically (by dicumyl peroxide) cross‐linked polybutadiene matrix. The same phenomenon was also studied by an investigation of the ability of the polymer to crystallize using DSC measurements. The solubility of the elastomer depends on the size of its macromolecular chains. Cross‐linking, leading to an increase in the size of macromolecules, provokes an insolubility of the elastomer. By densimetry measurements, it was possible to follow the changes in the solubility of the polymer up to its gel‐point. Beyond the gel‐point, the swelling solvent, cyclohexane, was used as a textural probe. Using the shift of its solid‐solid thermal transition points, it was possible to calculate the distribution of the distances between the cross‐links as a function of the curing times by thermoporosimetry analysis. Copyright © 2003 Society of Chemical Industry

Tensions superficielles de copolymères méthacryliques perfluoroalkylés

AbstractThe surface properties of methacrylic copolymers with a random distribution of perfluoroalkyl pendent groups were studied by a tensiometric method and were found to depend on the concentration of fluorinated units (2‐hydroxy‐4,4,5,5,6,6,7,7,8,8,9,9,9‐tridecafluorononyl methacrylate (1)), and the nature of the non‐fluorinated methacrylic ester (methyl, butyl, stearyl). The surface tensions estimated by various approaches (critical surface tension, geometric and harmonic mean approximations) are very low (11 mN · m−1 < y < 12 mN · m−1). The surface tension of the copolymers drops drastically when a few percent of fluorinated units are incorporated into the polymeric chain. The wetting hysteresis, observed particularly in the case of water, could be due to the mobility of macromolecular chains at the interface, leading to a reorganization of fluorinated groups in order to minimize the interfacial energy.

Hybrid‐particulate composites based on an epoxy matrix, a reactive rubber, and glass beads: Morphology, viscoelastic, and mechanical properties

AbstractThe deformation and fracture behaviors of hybrid‐particulate epoxy composites have been examined. These materials were based on a DGEBA/DDA matrix with various volume fractions of glass beads and different rubber contents. Young's modulus, yield stress, dynamic mechanical spectra, and fracture energy have been determined at room temperature. The Kerner model fits well the Young's modulus for the hybrid complexes with various glass bead contents. The analysis of the relaxation peak recorded from viscoelastic measurements allow us to discuss the influence of the introduction of the glass beads on the mobility of macromolecular chains and the characteristics of the rubber‐separated phase. The fracture energy displays a strong improvement and a synergism effect due to the presence of both kinds of particules. The toughening mechanisms were discussed. © 1993 John Wiley & Sons, Inc.

Radiation‐induced grafting of styrene onto FEP. films: Structure and thermal behaviour of copolymers

AbstractThermal characteristics of radiation‐grafted FEP‐g‐polystyrene copolymer films were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The grafting of polystyrene onto FEP film introduced a two‐step degradation pattern where polystyrene degradation occurred in the range of 400–460°C beyond which the loss in the FEP component was observed. DSC studies showed that the heat of fusion was reduced in the grafted FEP samples. This was attributed to the dilution of inherent crystalline zones by the incorporation of amorphous polystyrene grafts into the amorphous region of the FEP matrix. The melting temperature, on the other hand, remained constant for the entire range of graft levels (0–40%). All the copolymer films exhibited two glass transition temperatures (Tg) each corresponding to the FEP and polystyrene moieties. However, the Tg in grafted films were found to be higher as compared to that in ungrafted FEP and homopolystyrene films. These results have been explained in terms of the decrease in the segmental mobility of macromolecular chains in the grafted films.