The common reed, Phragmites australis, is a plant species quite similar to the currently used bio-based aggregates and available on most continents. The purpose of this work is to characterise this common reed and compare its properties to other plants already studied for building use. This study presents the different properties focussing on Phragmites australis chemical composition, hydrophobicity nature and how this character could be explained. To that end, wettability and also water adsorption measurements were carried out on plant flour and aggregates in comparison to miscanthus, wood and hemp shiv properties. Formulations based on reeds of different origins and using different binders (lime and earth) were tested in compression and with thermal conductivity measurements in order to evaluate the behaviour of the reed as a material for building use.

Composites based on lignocellulosic fillers such as wood, miscanthus or common reed have received much attention due to their low cost and positive impact. Knowledge of the physico-chemical characteristics of plant flour is essential to obtain indications of the thermal stability and humidity behaviour of the resulting biocomposite. The different methods that can be applied to plant flours to characterise them for composite applications are presented. Chemical composition, wettability and sorption curves are the most important data that can distinguish one plant filler from another. This article focuses on the Phragmites australis (P.a.), a widespread wild plant that shows interesting properties for composite applications due to its hydrophobicity. First results indicate a significant amount of solubility in P.a. and a high presence of silicon. Despite a greater quantity of hemicellulose (polysaccharide reinforcing hydrophilicity) in reed P.a. compared to wood, it shows high hydrophobic behaviour against both water vapour adsorption and wettability. Thus, the amount of hemicellulose appears not to be a sufficient criterion to justify the hydrophilic/hydrophobic behaviour of a biocomposite based on plant flour.

Wood-plastic composites (WPCs) are water-sensitive materials. Standards describe water absorption protocols on composites to obtain results after a long period of aging. From an industrial point of view, it is necessary to obtain the same information (i.e. equilibrium water content and absorption kinetics) over a short time. In this paper, we propose a new immersion aging protocol based on cubes taken from a reference WPC. This new methodology was validated by varying several test parameters (temperature, sample size, etc.) and applying it to other WPCs. Cubic samples were found to diverge from a Fickian behavior after a certain time of aging because of swelling and cracking that creates another characteristic pore scale and an increase of diffusion coefficient. Compared to the same formulation of cubic samples, the plate samples usually used for water absorption didn't crack. Fick's law approximation was used to determine the diffusion coefficient on plate materials. The coefficients measured in the three directions of WPC decks and a 3D model enabled us to recalculate the apparent coefficient of cubic samples for short-term absorption. Comparison of diffusion coefficients for short and long-term absorption showed the water concentration dependence of composites. Long-term diffusion coefficients and swelling stress coefficients were used in the pseudo-Fickian model to predict the water absorption behavior for composites undergoing water concentration dependence.

This work aims understanding the influence of the size distribution of wood flour particles on the physical and mechanical properties of an extruded wood plastic composite (WPC). A industrial-scaled process has been tested for both the wood flour production and the composite forming. Three size distributions of wood flour have been produced from the same batch of wood chips. The analyses of the particle size and form for the three wood flours were carried out by sieve column and by image analysis, revealing the limits of sieving in the case of particles with a high aspect ratio. The present study investigates the influence of the wood flour size distribution on the tensile and flexural behavior of WPC. The Charpy impact behavior of HDPE-WPC is also studied. In addition to the industrial process, the originality of this work lies in relating the microstructure to the mechanical performances of the extruded WPC; especially the orientation of the wood particles that differs according to the size distribution of the wood flour used. In general, mechanical performances of composites are improved by adding large particles. However, in the transverse direction to the extrusion, fine wood flour allows better performances. (C) 2017 Elsevier Ltd. All rights reserved.

The mechanical and toughening properties of ternary nano-composites (polypropylene/polyolefin elastomer/calcium carbonate) are investigated. Blends of polypropylene (PP)/ethylene-alpha olefin copolymer (polyolefin elastomer)/nano calcium carbonate were prepared through a two-step process. Stearic acid-treated CaCO3 (denoted CC322) and non-treated CaCO3 (denoted CC31) were used at content of 1%, 3%, and 5%. Two polyolefin elastomers (POE), ethylene-butene and ethylene-octene copolymers at 5 wt% were also used to adjust the phase structure of the ternary nano-composites. Tension surface measurements were correlated to morphological observations. Two phase structures were found: (1) treated calcium carbonate contributes to form the core-shell structure (2) non-treated calcium carbonate builds filler-network structure for the two POE. The mechanical properties of nano-composites were investigated using Izod impact and tensile tests. The influence of the morphologies on the impact strength and toughness of the nano-composites was studied. The formation of a filler-network structure was found to be a key for the toughness enhancement. A positive and synergic effect was found using ethylene-octene copolymer and non-treated calcium carbonate.

Calcium carbonate (CaCO3) reinforced polypropylene/ethylene propylene rubber (PP/EPR) copolymer composites for automotive use were developed by means of extrusion and injection molding process. Three kinds of CaCO3 (stearic acid treated and untreated) nanoparticles and microparticles were used as fillers. The influence of stearic acid, particle size, and filler content on the state distribution and morphology were investigated by SEM and rheological measurements. Two different morphologies were observed: EPR and CaCO3 dispersed in the PP matrix and a core shell structure, depending on the interactions between EPR and CaCO3. Toughening mechanisms and mechanical properties of the different systems were investigated. Significant improvement in tensile modulus is observed in all composites, depending on filler content. Elongation and notched impact strength were drastically decreased, especially for composites with nano CaCO3. Better impact properties were obtained with low content of treated particles, showing the importance of filler treatment. POLYM. ENG. SCI., 55:2859–2868, 2015. © 2015 Society of Plastics Engineers

This paper discusses the influence of low content red fibers on the mechanical characteristics of recycled HDPE composites. Composites of High Density Polyethylene (HDPE) and common reed (Phragmite australis) natural fibers were prepared by successive single screw extrusion blending. The mechanical and thermal properties of these composites which have low concentrations of fibers were investigated. It was found that the number of extrusions had no effect on the thermal stability of composites, even if the presence of fibers may be accelerating the degradation of the polymer matrix. Moreover, rheological measurements showed a decrease in the viscosity of the neat matrix, while the opposite was observed in composites for which the highest viscosity is obtained after five cycles of extrusion. These results suggest a decrease in the molecular weight of the HDPE during reprocessing. For composites, however, a good dispersion of the RF matrix was obtained, which increased as the number of extrusions grew larger. As for the mechanical properties, a substantial enhancement in ductility was observed, as compared to that of neat recycled matrices, when small RF concentrations were added. Thus, for 2.6% RF the best enhancement of ductility was obtained with the conservation of the fiber length and a good dispersion of fibers. These findings show that incorporating low contents of reed fibers can be an interesting solution when trying to improve the mechanical behavior of recycled polyethylene.

The present article investigates the recycling effect on properties of dilute suspension of HDPE reinforced by SGF without coupling agents. This dilute suspension at different proportions of SGF loading was produced by melt compounding cycles with a single screw extruder. The differential scanning calorimetry results have shown an increase in the crystallinity of HDPE with SGF proportion and the number of extrusions. The increase varies from 8.2% for neat HDPE 5 extrusions to 13.3% for HDPE 10% SGF 3 extrusions. Besides, rheological measurements have shown a decrease in the viscosity of neat matrix from 33,800 Pa.s to 24,500 Pa.s after 5 extrusions for 0.01 s −1 , while the opposite is observed for composites for which the highest viscosity is obtained with five cycles of extrusion. These results suggest a decrease in the molecular weight of the HDPE during reprocessing, but for composites a good dispersion of SGF matrix was obtained, increasing with the extrusion number. As for the mechanical properties, a substantial enhancement in ductility was observed, compared to neat recycled matrix, by adding small SGF concentrations. Thus, for 1.6% and 2.6% SGF the best enhancement of ductility was obtained with conservation of the fiber length and a good dispersion of fibers.

The effect of successive injection moldings on the thermal, rheological, and mechanical properties of a polypropylene impact copolymer (PP) was investigated. The crystal content decreased as the molecular weight decreased due to chain scission with repeated injection molding. The Young modulus and the yield stress remained constant, despite a drop in the strain to break. Virgin and recycled PP matrix were filled with nanosized calcium carbonate (CaCO3) particles. The effect of morphology on the thermal and mechanical properties of nanocomposites of virgin and recycled PP filled with nanosized CaCO3 particles was also studied. The mechanical properties of the nanocomposites were strongly influenced by the intrinsic toughness of the matrix and the concentration and dispersion of the filler. The yield strength and strain of virgin PP decreased gradually, while its Young's modulus increased slightly with increasing CaCO3 loading. These phenomena were less pronounced for the recycled matrix. Incorporation of nanoparticles to virgin matrix produced an increase in tensile stiffness and ductility, when good dispersion of the filler was achieved. However, the impact strength dropped dramatically for high filler contents. A significant increase in impact strength was observed for the recycled PP. POLYM. ENG. SCI., 50:1904-1913, 2010. (C) 2010 Society of Plastics Engineers

The aim of this paper is to study the mechanical behavior of three copolymer polypropylene (PP) and to use a non usual phenomenological three-dimensional hyper-visco-hysteresis (HVH) model. This model is introduced in the finite element computation software, called HEREZH++ [1]. This behavior law is particularly adapted to model cyclic loading, loading/unloading and complex loading (non-radial). Experimental tests of monotonic tension, cyclic loading–unloading and relaxation tests at various strain rates and variable levels of strain are carried out on three grades of PP molded specimens. The results obtained from these tests enabled us to identify the HVH model parameters by a least squares minimization method. The constitutive model seems to be adequateness to describe the stress–strain evolution of the studied polymers under various mechanical loadings such as the loading–unloading and the torsion tests.

Microscopic, nanoindentation and tensile tests were carried out to determine the mechanical behavior of PP and PLLA/reed fiber composites. As a first step, nanoindentation investigations were carried out to obtain longitudinal modulus and hardness of vegetal fibers. This study has allowed us to place the mechanical properties of reed fibers between those of sisal and hemp fibers. Optical microscopic observations have exposed the short length and the poor aspect ratio of the reed fibers used. Complementary SEM pictures have shown an improvement of the bonding between fibers and matrix with the addition of PP-g-MA or PLA-g-MA and the poor dispersion of reed fiber into composites by showing an important number of bundles.Tensile tests have highlighted an important improvement of the tensile modulus and a decrease of the tensile strength at yield with the addition of vegetal fibers. The presence of maleated matrix induces an improvement of modulus and strength for PP/reed composites. (C) 2008 Elsevier Ltd. All rights reserved.

The dynamic mechanical and dielectric behaviours of Polypropylene (PP) and (Ethylene-Vinyl Acetate) Copolymer (EVA) blends are reported as a function of the morphology. For EVA contents lower than 20%, blends show the two-phase morphology characteristic of immiscible blends, with spherical EVA droplets finely dispersed in the PP matrix. After stretching in the molten state, the morphology of EVA fibers is observed. Mechanical Relaxation Spectroscopy display three relaxation processes: the EVA and PP alpha-relaxations associated to the glass transitions and a transition corresponding to a PP crystalline phase relaxation. The PP alpha-relaxation shifts to higher temperatures when EVA presents a fiber morphology, corresponding to a decrease of PP chain mobility since it is hindered by the reinforcement effect of EVA fibers. Quite different results are obtained by DRS analysis. In blends containing EVA fibers, only one main relaxation associated to the EVA alpha-transition is observed whereas one additional relaxation can be noticed in the blends containing EVA droplets. This new relaxation might be assigned to interfacial polarization effects, phenomena that are sometimes observed in heterogeneous polymer blends when a low content of one polar component is embedded in a non conductive matrix. In this case, the occurrence of a characteristic interfacial polarization relaxation appears to be correlated to the accessible experimental frequency.

The use of volume fractions in the empirical mixing laws to predict the glass transition temperatures (Tg) of polymer blends provides good agreement with experimental values, even for polymer systems with different densities. No adjustment parameter is therefore required whereas Gordon-Taylor and Kwei equations based on weight fractions need the use of a fitting parameter which has to be determined from experimental data. This assumption was validated from Tg measurements through DSC experiments conducted on PMMA /PVDF blends which have significantly different densities.

The effects of the composition and resulting morphology on the crystallization and rheology of blends containing poly(butylene terephthalate) (PBT) and an ethylene-co-ethyl acrylate (EEA) copolymer, two immiscible polymers, were studied over the entire range of volume fractions. Differential scanning calorimetry (DSC) thermograms recorded during cooling showed important differences, mainly in terms of the PBT crystallization temperatures, depending on the blend composition. In addition to the classical crystallization peaks of PBT and EEA, a third crystallization peak appeared for blends containing less than 60% PBT. This peak was attributed to a delayed crystallization of PBT. This phenomenon was examined in terms of homogeneous crystallization. Linear viscoelastic measurements allowed the delayed crystallization behavior in these polymer blends to be displayed. Indeed, the variation of the storage modulus with the temperature showed increasing steps during cooling. These sudden increases appeared at temperatures very close to those at which the crystallization peaks were observed in the DSC experiments. This behavior was verified for different blend compositions. (C) 2004 Wiley Periodicals, Inc.

Abstract Crystallization of binary blends of semi-crystalline polyolefins (i-polypropylene and HD-polyethylenes) and amorphous cycloolefin copolymers (COC) was followed by Differential Scanning Calorimetry (DSC). Blend morphologies were investigated by Scanning Electronic Microscopy (SEM). The thermal behavior and morphology of iPP–COC blends are characteristic of immiscible blends. The two crystallization exotherms observed on cooling from the melt were explained in terms of fractionated crystallization. This phenomenon occurs when iPP inclusions are finely dispersed in the COC matrix so that their number is much greater than the number of heterogeneities originally present in the bulk polymer, resulting in the suppression of the heterogeneous nucleation. A quite different behavior is observed in PE–COC blends. DSC and DMTA results show a significant decrease of both PE Tm and COC Tg, observations usually associated to some polymer miscibility in the amorphous phase. The crystallization mode and the resulting morphologies also appear to be largely dependent on the molecular weights and polydispersity indices of the dispersed phase.

Crystallization of semi-crystalline polyolefins (i-polypropylenes and HD-polyethylenes) in their blends with amorphous cycloolefin copolymers (COC) were studied. The thermal behaviour of the blends was characterized by Differential Scanning Calorimetry (DSC) whereas blend morphologies were investigated by Scanning Electronic Microscopy (SEM). In iPP/COC blends, a phenomenon of fractionated crystallization is evidenced when i-PP is finely dispersed in the COC matrix. Such a behavior is generally observed when the number of droplets is much larger than the number of heterogeneities originally present in the bulk polymer. In HDPE/COC blends, complex morphologies are observed which do not fit good correlation with DSC results. The nucleation and crystallization modes seem to be largely influenced by the characteristics of the micro-dispersed phase, largely dependent on the PE molecular weights and polydispersity indices.

The influence of pigments and mineral fillers on the crystallization kinetics of poly(vinylidene fluoride) (PVDF) in its blends with poly(methyl methacrylate) (PMMA) was studied by Differential Scanning Calorimetry and Optical Microscopy. The introduction of organic pigments or mineral fillers into FVDF results in a more or less significant increase in non-isothermal crystallization temperatures, depending on the additives used. In FVDF, the pigment nucleation activity is quite different from that previously found in poly(butylene terephthalate) (PBT). Attractive interactions between PVDF and additive surfaces are particularly important parameters. The competition between pigments and talc lead to the observation that some pigments are able to inhibit the nucleating power of this mineral in PVDF, probably through specific attractive interactions. In PVDF-PMMA blends, selective interactions between polymers and additives were observed, depending on their chemical structures. Highly chlorinated pigments present a strong attraction for PMMA and then lose an important part of their nucleating power towards FVDF. On the other hand, a pigment containing carbonyl groups becomes the most active nucleating agent, illustrating the presence of strong interactions between such compounds and the PVDF C-H bonds.

The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester–MMA) copolymers (MMA–MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA–MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA–MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory–Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ12 increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ12 values as compared to VDF–TFE or particularly to VDF–TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values.