Collapsibility of metastable sand by non-conventional oedometer tests
The stability of foundations soils could represent a clear and present threat for the conservation of even well preserved buildings, particularly for Architectural heritage conservation and land art heritage. A dramatic case is the presence of collapsible metastable sands as foundation soils, as it occurs in the sacral complex Valle dei Templi in Agrigento. This site listed by UNESCO, stands on a crest of a calcarenite cuesta, overlaying a layer of these sands. When the collapsible sand is dry, the structure is strong enough to bond the sand particles together. When the sand becomes wet, a de-structuration mechanism occurs and the soil’s strength is compromised. This paper has a twofold aim…
Structure–property relationship and controlled drug release from multiphasic electrospun carvacrol-embedded polylactic acid/polyethylene glycol and polylactic acid/polyethylene oxide nanofiber mats
Electrospinning technologies gained considerable interest over the last decade. In this study, it is proposed a systematic study of polylactic acid/polyethylene glycol (PLA/PEG) and polylactic acid/polyethylene oxide (PLA/PEO) electrospun blends at different concentrations. The effect of blend composition and PEG molecular weight on the morphological and mechanical properties of the mats was evaluated. Furthermore, the kinetic release of carvacrol as model drug in phosphate buffer saline at 37℃ was studied and the data were then fitted using an exponential model. The scanning electron microscopy revealed that the morphology of the mats was strongly dependent on the relative ratio PLA:PEG, …
Green Composites Based on Hedysarum coronarium with Outstanding FDM Printability and Mechanical Performance
The addition of natural scraps to biodegradable polymers has gained particular interest in recent years, allowing reducing environmental pollution related to traditional plastic. In this work, new composites were fabricated by adding 10% or 20% of Hedysarum coronarium (HC) flour to Poly (lactic acid) (PLA). The two formulations were first produced by twin screw extrusion and the obtained filaments were then employed for the fabrication of composites, either for compression molding (CM) or by fused deposition modeling (FDM), and characterized from a morphological and mechanical point of view. Through FDM it was possible to achieve dense structures with good wettability of the filler that, on…
Innovative, ecofriendly biosorbent-biodegrading biofilms for bioremediation of oil- contaminated water.
Immobilization of microorganisms capable of degrading specific contaminants significantly promotes bioremediation processes. In this study, innovative and ecofriendly biosorbent-biodegrading biofilms have been developed in order to remediate oil-contaminated water. This was achieved by immobilizing hydrocarbon-degrading gammaproteobacteria and actinobacteria on biodegradable oil-adsorbing carriers, based on polylactic acid and polycaprolactone electrospun membranes. High capacities for adhesion and proliferation of bacterial cells were observed by scanning electron microscopy. The bioremediation efficiency of the systems, tested on crude oil and quantified by gas chromatography, showed that…
Effect of different matrices and nanofillers on the rheological behavior of polymer-clay nanocomposites
In this work, a comprehensive study of the rheological behavior under shear and isothermal and nonisothermal elongational flow of low density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA) based nanocomposites was reported to evaluate their "filmability", that is, the ability of these material to be processed for film forming applications. The influence of two different kinds of organoclay - namely Cloisite 15A and Cloisite 30B - and their concentration was evaluated. The presence of filler clearly affects the rheological behavior in oscillatory state of polyolefin-based nanocomposites but the increase of complex viscosity and the shear thinning are not dramatic. A larger st…
Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer
Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrilla…
Green Composites Based on PLA and Agricultural or Marine Waste Prepared by FDM
Three dimensional-printability of green composites is recently growing in importance and interest, especially in the view of feasibility to valorize agricultural and marine waste to attain green fillers capable of reducing bioplastic costs, without compromising their processability and performance from an environmental and mechanical standpoint. In this work, two lignocellulosic fillers, obtained from Opuntia ficus indica and Posidonia oceanica, were added to PLA and processed by FDM. Among the 3D printed biocomposites investigated, slight differences could be found in terms of PLA molecular weight and filler aspect ratio. It was shown that it is possible to replace up to 20% of bioplastic …
Nanofilled Thermoplastic–Thermoplastic Polymer Blends
Nanofillers can play two important roles in polymer blends. The first is the improvement of various properties such as mechanical, barrier, thermal, flame retardancy, and electrical properties. The second is the modification of miscibility/compatibility and morphology of polymer blends. The mechanism of action of nanoparticles to modify the morphology, interfacial properties, and performance of immiscible polymer blends relies on their localization, their interactions with polymer components, and the way these additives disperse within the polymer blend. The objective of this chapter is to review the research on nanofilled thermoplastic/thermoplastic polymer blends, paying particular attent…
A new equipment to measure the combined effect of humidity, temperature, mechanical stress and UV exposure on the creep behaviour of polymers
To be able to study and predict the physical properties of a polymeric material under different environmental conditions is very important. Moisture, UV irradiation, thermal and mechanical stresses can dramatically change the characteristics of the material and hinder some specific applications. In this work, a new equipment able to perform creep tests under different environmental conditions (temperature, humidity, stress) is presented. Some preliminary results are also presented using a sample of polyamide 6. As this polymer is sensitive to all these variables, it is appropriate to verify the effectiveness of the new instrument.
Reactive blending of a functionalized polyethylene with a semiflexible liquid crystalline copolyester
Reactive blends (50/50 w/w) of a low molar mass polyethylene containing free carboxylic groups (PEox) and a semiflexible liquid crystalline polyester (SBH 1 : 1 : 2, by Eniricerche) have been prepared at 240 degrees C in a Brabender mixer, in the presence of Ti(OBu)(4) catalyst, for different mixing times (15, 60, and 120 min). In order to prove the formation of a PE-g-SBH copolymer, the blends have been fractionated by successive extractions with boiling toluene and xylene. The soluble fractions and the residues have been analyzed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG and DTG), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM)…
Reactive Compatibilization of PBT/EVA Blends with an Ethylene-Acrylic Acid Copolymer and a Low Molar Mass Bis-Oxazoline
Polyesters and polyolefins form highly incompatible blends with poor properties and gross morphology that hinder any practical applications. In this work, the possibility to compatibilize an incompatible blend of poly(butylene terephthalate) (PBT) with ethylene vinyl acetate (EVA) by adding a bis-oxazoline compound, 2,2'-(1,3-phenylene)-bis(2-oxazoline) (PBO), and an ethylene acrylic acid copolymer (EAA) as compatibilizer precursors has been studied. The results indicate that the binary uncompatibilized blends show poor mechanical properties and a bad morphology with scarce adhesion between the phases. The situation is only slightly improved when the EAA is added while the best performance …
A new route for the preparation of flexible skin–core poly(ethylene-co-acrylic acid)/polyaniline functional hybrids
Abstract Surface modification of polymeric films is a way to obtain final products with high performance for many specific and ad hoc tailored applications, e.g. in functional packaging, tissue engineering or (bio)sensing. The present work reports, for the first time, on the design and development of surface modified ethylene–acrylic acid copolymer (EAA) films with polyaniline (PANI), with the aim of inducing electrical conductivity and potentially enable the electronic control of a range of physical and chemical properties of the film surface, via a new “grafting from” approach. In particular, we demonstrate that PANI was successfully polymerized and covalently grafted onto flexible EAA su…
Degradation and Recycling of Films Based on Biodegradable Polymers: A Short Review
The environmental performance of biodegradable materials has attracted attention from the academic and the industrial research over the recent years. Currently, degradation behavior and possible recyclability features, as well as actual recycling paths of such systems, are crucial to give them both durability and eco-sustainability. This paper presents a review of the degradation behaviour of biodegradable polymers and related composites, with particular concern for multi-layer films. The processing of biodegradable polymeric films and the manufacturing and properties of multilayer films based on biodegradable polymers will be discussed. The results and data collected show that: poly-lactic…
Experimental analysis and micromechanical models of high performance renewable agave reinforced biocomposites
Abstract The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the m…
Green Composites Based on Mater-Bi® and Solanum lycopersicum Plant Waste for 3D Printing Applications
3D printability of green composites is currently experiencing a boost in importance and interest, envisaging a way to valorise agricultural waste, in order to obtain affordable fillers for the preparation of biodegradable polymer-based composites with reduced cost and environmental impact, without undermining processability and mechanical performance. In this work, an innovative green composite was prepared by combining a starch-based biodegradable polymer (Mater-Bi®, MB) and a filler obtained from the lignocellulosic waste coming from Solanum lycopersicum (i.e., tomato plant) harvesting. Different processing parameters and different filler amounts were investigated, and the obtained sample…
Oxazoline functionalization of polyethylenes and their blends with polyamides and polyesters
The compatibilization of blends of polyamide-6 (PA6) with linear low density polyethylene (LLDPE) and of poly(ethylene terephthalate) (PET) with high density polyethylene (HDPE), by functionalization of the polyethylenes with oxazoline groups was investigated. Chemical modification of LLDPE and HDPE was carried out by melt free radical grafting with ricinoloxazoline maleinate. Blends preparation was made either with a two-steps procedure comprising functionalization and blending, and in a single step in which the chemical modification of polyethylene with the oxazoline monomer was realized in situ, during blending. The characterization of the products was carried out by FTIR spectroscopy an…
A New Methodological Approach to Correlate Protective and Microscopic Properties by Soft X-ray Microscopy and Solid State NMR Spectroscopy: The Case of Cusa’s Stone
Hydrophobic treatment is one of the most important interventions usually carried out for the conservation of stone artefacts and monuments. The study here reported aims to answer a general question about how two polymers confer different protective performance. Two fluorinated-based polymer formulates applied on samples of Cusa’s stone confer a different level of water repellence and water vapour permeability. The observed protection action is here explained on the basis of chemico-physical interactions. The distribution of the polymer in the pore network was investigated using scanning electron microscopy and X-ray microscopy. The interactions between the stone substrate and the protective…
Effect of the additive level and of the processing temperature on the re-building of post consumer pipes from polyethylene blends
Abstract One of the main shortcomings of the mechanical recycling is that the properties of the secondary materials are generally sensibly inferior with respect to the virgin ones. This feature implies, for sure, that they cannot be used for the same technological application but also other uses of the secondary material are impossible. The aim of this work is to study the re-building of recycled post-consumer pipes, made of a blend of different polyethylenes, by re-processing in the presence of a nitroxyl compound as radical generator. The processing temperature and the additive concentration have been varied in order to study the effect of these parameters on the final properties. The mec…
On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene
Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, pr…
Preparation and characterization of polyamide 6/polyethylene blend-clay nanocomposites in the presence of compatibilisers and stabilizing system
Abstract Several compatibilising systems were added to high-density polyethylene (HDPE) and polyamide 6 (PA6) blends in the presence of an organically modified montmorillonite (OMM). All the blends were prepared by using a co-rotating twin-screw extruder and characterized by SEM, TEM and XRD analyses. In addition, the rheological behaviour and the mechanical properties – tensile and impact – were evaluated. The presence of OMM affects the dimensions of the polymeric phases in the blend but not their mutual adhesion, granted only by the compatibilisers. TEM, SEM and XRD analyses indicated that there is a strict correlation between the compatibilisation level and the final interlayer distance…
Rheological Response of Polyethylene/Clay Nanocomposites to Annealing Treatment
The rheological response of a polyethylene/clay nanocomposite to annealing treatment under air and nitrogen atmospheres was studied. The treatment influences the rheology of the nanocomposite significantly. In particular, the viscosity and the non-Newtonian behavior dramatically increase with annealing time, and a liquid-like/solid-like transition is observed. The annealed samples were characterized by ATR-FT-IR spectrometry and it was shown that a silicate-rich layer is formed on the surface of the nanocomposite. This result was confirmed by TEM images of bulk and surface of annealed samples. It was demonstrated that the formation of this coating is the main cause of the change of rheologi…
Effect of adding wood flour to the physical properties of a biodegradable polymer
Wood flour/polymer composites (WPC) gained a significant interest during the last decades, due to several advantages related to the use of a natural-organic filler rather than an inorganic-mineral one. However, most of the studies have been performed on composites based on polyolefin matrices. A further step is the use of biodegradable polymers instead of traditional ones. In this work, wood flour (WF), under the form of short fibers, with two different sizes (coarse and fine) was added to a corn starch based biodegradable polymer of the Mater-Bi family. The effect of WF size, WF content, thermal treatment on the mechanical properties was investigated. The tensile mechanical tests showed an…
Kenaf-filled biodegradable composites: rheological and mechanical behaviour
Biodegradable polymer composites, typically based on biodegradable polymer matrices and natural-organic fillers, are gaining rising interest and importance over the last few years. Several natural-organic fillers can be used but the most widespread so far is wood, in the form of fibres or flour. Alternative cellulosic fillers can ensure advantages in terms of resource utilization and properties of the final composite. In this work, Mater-Bi® based biodegradable composites were prepared with two kinds of wood flour, and directly compared with alternative composites containing kenaf fibres. The use of kenaf fibres allowed improved elastic modulus, tensile strength and interaction with the pol…
Incorporation of nisin in poly (ethylene-co-vinyl acetate) films by melt processing: a study on the antimicrobial properties
Both industry and academia have shown a growing interest in materials with antimicrobial properties suitable for food packaging applications. In this study, we prepared and characterized thin films of ethylene-co-vinyl acetate (EVA) copolymer with antimicrobial properties. The films were prepared with a film blowing process by incorporating a nisin preparation as an antimicrobial agent in the melt. Two grades of EVA containing 14 and 28% (wt/wt) vinyl acetate (EVA 14 and EVA 28, respectively) and two commercial formulations of nisin with different nominal activities were used. The effect of the nisin concentration also was evaluated. The films with the highest antimicrobial activity were th…
Melt stabilization of wet polyamide 6
Abstract Melt processing of polycondensate polymers must be carried out after careful drying in order to avoid any hydrolytic chain scission caused by the presence of water or other small molecules. In this work, the effect of two different antioxidants on the processing and flow properties of a polyamide 6 sample not dried before processing operations has been studied. One of these stabilizers seems to protect the wet polymer from hydrolytic chain scission. This action has been interpreted considering that the stabilizer hydrolyses instead of the polyamide macromolecules.
Degradation Behavior of Nanocomposite Polymer Blends
The usefulness of any material, including nanocomposite polymer blends, depends on its degradability and durability. Thus, this chapter reviews the status of the research on degradation of nanocomposite polymer blends and, in particular, on clay-nanocomposite polymer blends, paying particular attention to both the role of the filler and the role of the blend morphology and composition. The results of recent research indicate that the clay has two opposing effects on the thermal stability of a nanocomposite polymer blend: (1) a promoter effect of the polymer matrix degradation, which decreases the thermal stability, and (2) a barrier effect, which improves the thermal stability. Moreover, th…
Modification of EVOH copolymers with e-caprolactone: synthesis and compatibilization effects in PE/PVC blends
Polyethylene-polycaprolactone graft copolymers with different chemical structures (i.e. different number and length of PCL grafts and molecular weight of PE backbone) were synthesized from various EVOH copolymers and e-caprolactone, using Aluminum isopropoxide as catalyst, and were tested for their compatibilizing capability in PE/PVC blends. PE and PCL segments in the graft copolymers were found completely immiscible, while PCL segments of the graft copolymers were found completely miscible with PVC. When graft copolymers were added to PE/PVC blends they proved to be good agents for the dispersion of PVC phase in the PE matrix. SEM showed also improved adhesion between the dispersed PVC ph…
Rheological Properties of Different Film Blowing Polyethylene Samples Under Shear and Elongational Flow
Summary: The rheological behavior of polyethylenes ismainly dominated by the molecular weight, the molecularweight distribution and by the type, the amount and thedistribution of the chain branches. In this work a linearmetallocenecatalyzedpolyethylene(m-PE),abranchedme-tallocene catalyzed polyethylene (m-bPE), a conventionallinear low density polyethylene (LLDPE) and a low densitypolyethylene (LDPE) have been investigated in order tocompare their rheological behavior in shear and in elonga-tional flow. The four samples have similar melt flow indexand in particular a value typical of film blowing grade.The melt viscosity has been studied both in shear and inisothermal and non-isothermal elonga…