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Background This work evaluated the performances of protein-based bioplastics obtained from black soldier fly (Hermetia illucens) prepupae. Protein films were synthesized by film casting, using both the whole proteins and their soluble fraction at pH = 10. The effects of glycerol as a plasticizer and of citric acid as a mild crosslinker on film properties were also evaluated. Results Films obtained using the soluble protein fraction were the strongest, as well as the most homogeneous and transparent ones. Protein mild crosslinking improved film tensile properties, especially in films obtained with the whole protein fraction. Non-crosslinked samples had a high affinity with water while crosslinking almost eliminated the ability of films to absorb water. All protein-based films proved to be effective barriers to red light (transmittance less than 2%). Conclusions Bioplastics derived from black soldier fly prepupae may find applications in the agricultural sector (biodegradable pots, mulching films, utensils) and deserve to be tested for food and non-food packaging. © 2021 Society of Chemical Industry.

Fabrication of new biobased composites with remarkable properties offers an attractive pathway for producing environmentally friendly materials. Here, a reinforcement for poly(3-hydroxybutyrate-co-...

none 7 no In this study epoxy resin/TiO2 nanocomposites have been prepared according to the Reactive Suspension Method, to obtain TiO2 nanoparticles (NPs) covalently bonded to the macromolecular network. After the chemical- physical characterization of both NPs and polymeric matrix, the dynamic-mechanical properties (storage modulus as a function of the temperature) of the nanocomposites have been studied. In particular, the experi- mental storage modulus in the rubbery state has been found significantly higher than the value predicted by the generalized Kerner equation. This has been rationalized considering that the inorganic NPs act as additional cross-linking points, as confirmed by the solid-state NMR investigations, leading to a very high and unexpected increase of the stiffness. Consequently, the experimental data have been also fitted using the Halpin-Tsai equation, which has allowed to obtain suitable predictions of the storage modulus by adjusting the so-called reinforcing geometry factor. By the proposed approach has been possible to incorporate in the Halpin-Tsai model a factor that considers the contribution due to the presence of filler/matrix covalent bonds and to obtain more accurate predictions. none Micaela Degli Esposti; Francesca Bisi; Valeria Righi; Paola Fabbri; Federica Bondioli; Massimo Messori; Davide Morselli Micaela Degli Esposti; Francesca Bisi; Valeria Righi; Paola Fabbri; Federica Bondioli; Massimo Messori; Davide Morselli

The two-way shape memory effect is the ability of a material to change its shape between two configurations upon application and removal of a stimulus, and, among shape memory polymers, it is featured only by few systems, such as semicrystalline networks. When studied under tensile conditions, it consists of elongation–contraction cycles along cooling and heating across the crystallization and melting region, typically under the application of a constant load. However, recent studies on crosslinked semicrystalline co-polymers demonstrate that also a completely stress-free, or self-sustained, two-way effect may be achieved through specific thermomechanical cycles. This effect is currently regarded with interest for the development of intrinsically reversible sensors and actuators, and it may also be displayed by simpler materials, as homopolymer-based semicrystalline networks. Only seldom articles investigate this possibility, therefore in this work the two-way shape memory behavior is studied on a poly(ɛ-caprolactone) system, crosslinked by means of a sol-gel approach. The effect is studied both under stress-driven and stress-free condition, by applying properly set-up thermo-mechanical histories. The results allow to describe the effect as a function of temperature, to reveal the dependence on specific testing parameters and to compare the extent of the reversible strain variation under these two conditions.

In this work, poly(ethylene glycol) (PEG)/poly(epsilon- caprolactone) (PCL) semicrystalline networks were prepared by photo-cross-linking of methacrylated macromonomers with different molecular weights and in different proportions to obtain amphiphilic materials capable of displaying properly designed shape memory effects. Networks based on PCL 10 kDa and PEG 3 kDa showed suitable thermal and mechanical properties with well-separated crystallization and melting regions to achieve a self-standing two-way shape memory effect. Particularly, after the application of a specific thermomechanical history, these materials are capable of cyclically changing their shape between two configurations upon cooling-heating cycles in the absence of any external load applied. The effect of the composition of the networks and of the employed thermomechanical parameters, such as the applied strain and the actuation temperature, was investigated to shed light on the shape memory mechanism for this class of materials, which are considered promising for applications in the biomedical field and as reversible actuators for soft robotics.

A commercial tannin wine seed extract powder (T), a seed polyphenol extract (Sext) and virgin wine seeds wastes (Se) have been mixed with polypropylene (PP) and tested as long-term stabilizers. Their stabilizing activity has been compared with that of a synthetic antioxidant commonly used within PP (Irganox 1010). Each sample has been subject to both UV and thermal aging. The PP-based films photo-oxidation has been followed through the C=O formation over the aging time by FT-IR. The PP-based tensile specimens have been oven aged and the mechanical properties loss has been investigated monitoring the variation of the elongation at break. Melt Flow Index (MFI) measures and Different Scanning Calorimetry analysis have been conducted on thermally aged samples. At the same time, wine derived additives have been characterized in terms of total polyphenol content, FT-IR and UV/VIS spectra meanwhile catechin and gallic acid have been quantified by LC-MS. Experimental results have evidenced the ability of all the wine derived additives to withstand both to thermal and UV long-term degradation. In particular, wine seeds extracts exhibit the best results in terms of stabilization (even better than Irganox 1010) without compromising the PP mechanical, thermal, morphological and rheological properties.

In this study, covalently cross-linked network strategy has been applied to prepare new triple-shape memory polymers (TSPs) based on poly(l-lactide) (PLA)/poly(ɛ-caprolactone) (PCL) blends. The TSPs were fabricated by adding di-cumyl peroxide, with triallyl isocyanurate as a coagent for performing the cross-linking reaction. The differential scanning calorimetry (DSC) analysis demonstrated that all the PLA/PCL blends show two melting points (Tm,PCL and Tm,PLA), which can be employed as the transition temperature (Ttrans) to induce triple-shape memory behavior. The scanning electron microscopy (SEM) analysis indicated that there are two immiscible morphologies: co-continuous structure and matrix-droplet. The influence of temperature on the crystalline phase changes was analyzed by X-ray diffraction at various temperatures. The results revealed that during the heating–cooling cycle, the degree of crystallinity decreased when the temperature increased and at higher temperature, the crystallization peaks of PCL disappeared. Multiple thermal–mechanical tests were performed and the results showed that the composition ratio of the two phases plays an important role in the triple-shape memory behavior. The results confirmed that the excellent shape memory behavior was obtained for the sample containing 50 wt% PCL.

Grape stalks are a lignocellulosic biomass, which is a very complex material, whose easy and profitable fractionation to obtain its basic components is still not available. Therefore, alternative ways to try and make use of grape stalks are currently being explored. In the present study, the possible use of dried and milled grape stalks as filler in bio-composites was assessed using polybutylene succinate as a basic polymer. The tensile specimens produced using 10% grape stalk powder as it is and functionalized through pre-extrusion acetylation and silylation, and silylation in situ were characterized for their structural, mechanical, thermal, morphological, and color properties. The bio-composites showed to be stiffer than the control polymer, with an increase of Young’s modulus from 616 MPa to 732 MPa in the specimens obtained with acetylated grape stalk powder. This led to a potentially new method to valorize by-products of the wine industry such as grape stalks in order to recover raw materials which could prove useful in the biomaterials and bio-composites sector.

The aim of this work is to study some physical and chemical properties of an organic semiconductor (OSc)/ x%titanium dioxide (TiO2) heterosystem (with 0 ≤ x ≤ 20%) (OScs/ x%TiO2). The OSc is obtained from pure curcumin and paracetamol as starting molecules. The synthesis methodology of the mixtures of OScs/ x%TiO2 heterosystem involves a microwave-assisted multicomponent reaction using curcumin, paracetamol, and TiO2 as a heterogeneous solution. All mixtures were analyzed by Fourier-transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis/differential thermal analysis, X-ray diffraction, ultraviolet–visible spectroscopy, and scanning electron microscopy. The results obtained show a new nanocomposite with interesting pharmaceutical, optical, electronic, and structural properties, which can be used in the fields of energy production, water purification, and air purification, as a biomaterial and for electronic applications.

Oat hull fibers are an agri-food industrial waste used in this research as a filler for a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) matrix, to obtain a fully bio-based polymer-matrix composite material. The compounding process was carried out with a twin-screw extruder, avoiding chemical solvents and employing a technology commonly used by the industrial field. Silanization procedure was run to improve the affinity between the matrix and the filler. Compounds were structurally, microstructurally, mechanically and thermally characterized. Results denote that also at 8 v/v%, oat hull fibers work not only as inert filler, but also they have a slightly improving effect on mechanical properties of neat biopolymer, increasing of almost 12% the Young’s modulus, without a loss in tensile elongation at break. Therefore, this research study is a noteworthy approach which reduces the material costs and PHBH volumes, while valorizing waste biomasses.

The effect of epoxy dilution with acetone on the mechanical performance of epoxy-coated alkali-resistant glass (ARG) fabric embedded in a lime-based mortar is studied experimentally. The mechanical behaviour of the composite system is assessed in uni-axial tensile tests, according to the ICC guidelines. Epoxy is diluted in acetone and several concentrations, namely 10%, 25%, 50%, 75% and 90%, are considered in an attempt to define a decay law for strength, ductility and dissipated energy at failure. Although epoxy-coating promotes a striking improvement of the mechanical performance with respect to the uncoated specimens, epoxy dilution appears to little affect the global response, even at very low epoxy-to-solvent ratios. Actually, a notable increase in the ultimate strength and strain as well as dissipation capacity are evidenced for 75% dilution. Indeed, epoxy resin is able to uniformly impregnate the bundles of the yarns in a very thin layer, still preserving its contribution to the mechanical performance. In fact, wettability of the yarns plays a fundamental role in the mechanical performance of the laminate for it limitates telescopic failure. A threshold of viscosity is identified. Above this limit, the high quality of impregnation overcomes the issue of the reduction of the amount of epoxy resin in the coating. Besides, dilution strongly promotes the ease of application, as a result of the resin viscosity being sharply reduced. Most remarkably and contrarily to common expectation, the specific energy dissipated at failure exhibits a maximum point, whence an optimal dilution ratio exists which best balances interphase strength and ductility.

Invisible orthodontic aligners (IOAs) have been introduced in the orthodontic field as an innovative alternative for fixed brackets, in relation to their ability to be easily inserted/removed from the oral cavity without affecting the chewing ability and the aesthetic of the patients. The paper provides a complete physicochemical and mechanical characterization of thermoplastic materials in the form of disks used for commercial IOAs. A wide palette of specific techniques is considered, from tensile tests and dynamic-mechanical analysis, to X-Ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR-ATR) analyses and water absorption tests. The disks are investigated before and after immersion into staining beverages (red wine, coffee, nicotine and artificial saliva), in terms of colour variations, transparency, and microscopic surface modifications by means of colorimetry, UV-VIS absorbance and scanning electron microscopy (SEM). Among all the samples, polyurethane (PU) exhibited the highest crystallinity and the highest values of mechanical and thermal resistance, while the poly(ethylene terephthalate)-glycol (PETG) samples presented better transparency and less ability to absorb water. Moreover, red wine and coffee give noticeable colour variations after 14 days of immersion, together with a slight reduction of transparency.

Preliminary epoxy coating of the reinforcing fabric provides an effective approach for improving matrix-to-fabric strength in inorganic matrix composites. We investigate the effect of epoxy resin dilution in acetone on uni-axial tensile performance of coated alkali-resistant (AR) glass fabric embedded in a lime-based matrix. Remarkably, it is found that dilution has a mixed effect on performance and this trend is consistently retrieved for strength, ductility and energy dissipation. Indeed, performance initially decays and then it suddenly raises to a level close to or even exceeding that of the undiluted specimens. It is postulated that this behaviour is caused by resin viscosity, that falls off exponentially with the dilution degree. Once a viscosity threshold is breached, epoxy is capable of penetrating inside the yarn and thereby prevents telescopic failure, that is the sliding of the outer over the inner glass filaments. Furthermore, the interphase surface area increases dramatically and this enhances performance and narrows scattering. Besides, optimal viscosity is reached at an unexpectedly high dilution degree, whence material cost is significantly reduced. A cost-to-performance comparison of common strengthening technologies is presented, which shows that diluted epoxy composites score comparably to FRPs. It is concluded that epoxy coating optimization plays an important role in designing inorganic matrix composites.

A grape pomace extract (GPext) and a grape seed extract (T) have been melt mixed within poly(butylene succinate) (PBS) and tested as natural stabilizers. Their effect on the PBS stabilization has been evaluated trough thermo-mechanical degradative tests (reprocessing), thermo-oxidation (oven aging), thermogravimetric analysis (TGA) and biodegradation tests. GPext and T have been deeply analyzed in terms of polyphenolic profile and bioactivity to connect the stabilization's results with the antioxidant's structures. Additive T exhibited the best results, maintaining unaltered the PBS molecular weight both after six reprocessing steps and after 300 h of oven aging and to increase the degradation temperature of more than 20 °C. These encouraging results have been explained by the long-chains polyphenols present within T (medium degree of polymerization of 10.8), by the excellent radical scavenger activity of T (6.0 mM TEAC) and by the low releases of peroxides from T (0.06 µM H2O2).

In this study, the corrosion resistance of commonly used plumbing materials was evaluated when three disinfection treatments were applied in hot water distribution systems. In particular copper, br...

The preparation and thermo-mechanical characterization of composites based on polyamide 11 (PA11) filled with various amounts of both expandable and expanded graphites are presented. Investigation conducted using X-ray diffraction (XRD), scanning electron microscopy and surface area analyses indicated how graphite expanded under the selected processing conditions. The XRD analysis on PA11/graphite composites revealed no change in the crystal form of the PA11, while the presence of diffraction peaks associated to the graphite-stacked lamellae can be still detected. All the investigated composites showed an improvement of the thermal stability and mechanical properties (elastic and storage moduli).

The aim of this review is a faithful report of the panorama of solutions adopted to fabricate a component using vat photopolymerization (VP) processes. A general overview on additive manufacturing and on the different technologies available for polymers is given. A comparison between stereolithography and digital light processing is also presented, with attention to different aspects and to the advantages and limitations of both technologies. Afterward, a quick overview of the process parameters is given, with an emphasis on the necessities and the issues associated with the VP process. The materials are then explored, starting from base matrix materials to composites and nanocomposites, with attention to examples of applications and explanations of the main factors involved.

Three different solid wine wastes (peels, seeds and stalks) have been mixed with polypropylene (PP) and tested as stabilizers. Their stabilizing activity has been compared with that of a commercial tannin extract powder, rich in polyphenol. Thermogravimetric analysis, Oxidation Induction Time and Oxidation Onset Temperature measurements have been conducted to investigate the thermo-oxidative stability. Tensile tests, Dynamic Mechanical Analysis and Differential Scanning Calorimetry have been conducted on the samples in order to evaluate the effect of the additives also on the thermal and mechanical properties. Scanning Electron Microscopy have been used to assess the adhesion and distribution of the wine-wastes additives within the PP matrix. Experimental results evidence that all three wine-wastes derived additives do not significantly change the mechanical and thermal properties of PP, meanwhile they enhance its thermal stability. Moreover, the expectation to obtain better results with the commercial tannin extract has not been achieved. The obtained results show how wine wastes can be effectively used as polymer stabilizers and represent a valid alternative because of theirs environmental and cost-effects advantages.

In this study, a novel thermally actuated triple-shape memory polymer (triple-SMP) based on poly( l -lactide) (PLA)/poly( e -caprolactone) (PCL)/graphene nanoplatelets (GNps) nanocomposite was prepared by facile solution mixing method and the design of which was based on two well-separated melting temperatures. In order to improve the dispersion of GNps in the matrix, functionalization reactions were carried out on the GNPs surface. Functionalization was confirmed by various techniques including FTIR, Raman and TGA analysis. TEM micrographs revealed an exfoliated morphology for the functionalized GNps (FGNps) and a homogenous dispersion in the matrix. The crystallinity behaviour of nanocomposites was investigated by DSC and variable temperature XRD (VT-XRD) analysis and an increase in crystallinity was observed. Dynamic mechanical analysis (DMA) showed that the presence of FGNps improves the fixity and recovery ratios because of increase in crystallinity and thermal conductivity. The best shape memory behavior was obtained for PLA50/PCL50/FGNp 1.5 nanocomposite.

Poly(ethylene glycol) (PEG) blends photo-curable and thermal activated shape-memory polymers (SMPs), with different activation temperature (Tswitch), have been synthesized and characterized. PEG blends with different molecular weights were chain-end functionalized with isocyanate ethyl methacrylate and photo-cured with UV lamp. Degree of cross-linking of the blend network, determined by gel content measurement, resulted as higher than 95%. The thermal and thermomechanical properties of these SMPs PEG blends were characterized by differential scanning calorimetry and dynamic mechanical analysis. The shape-memory properties of the networks were quantified using thermomechanical three-point bending experiments and showed strain fixity rates higher than 99% and a minimum strain recovery ratio of 82%.

Hybrid transparent coatings based on zirconia nanoparticle fillers and epoxy resin were designed to increase scratch resistance of commodity polymers without impairing their optical properties. Suspensions of nano-crystalline ZrO 2 in benzyl alcohol were synthesized via a versatile non-hydrolytic sol-gel process using ZrCl 4 as precursor. The obtained ZrO 2 nanoparticles showed a crystalline structure attributable to a tetragonal phase and an average particle size of 2 nm. ZrO 2 nanoparticles, suspended in tert-butanol, were mixed with a commercial epoxy resin (5 and 10%wt.). The organic solvent was then evaporated and hybrid composites were deposited on polycarbonate and poly(methyl methacrylate). The obtained coatings showed a homogeneous adhesion and a negligible effect on the transparency of these polymers. An increased scratch-resistance was obtained by increasing the ZrO 2 nanoparticles content.

The conductive polymer-based applications combine low cost, simple manufacturing procedure, flexibility and other properties. However, the low viscosity and solubility of these polymers make it difficult to produce layers by using industrial techniques. Among the most commonly used conjugated conductive organic polymers we can mention polyacetylene, polythiophene, polypyrrole, polyaniline, etc. In order to test them in further applications, new copolymers of thiophene and p-methoxybenzaldehyde were synthesized. The copolymers obtained will be characterized by several techniques (NMR, UV, CV, ATG, and electrical characterization). The study of the optical properties after doping is performed according to oxidation-reduction reactions by FeCl3, I2, in order to apprehend the redox behavior of this copolymer. The calculated value of energy gap $$E_{g}^{{cv}}$$ of the studied polymers shows a decrease with the oxidation agent doping according to their oxidation potential, from 2.48 eV for the no doped copolymer passing by 2.22 eV for the copolymer doped with I2 and up to 1.5 eV for the copolymer doped with FeCl3. The decrease of the energy gap with the doping (FeCl3 and I2) corresponds to the increase of the conductivity with doping from 2.85 × 10–5 S m–1 for no doped polymer to 7.86 × 10–5 S m–1 for copolymer doped with I2 and 1.55 × 10–4 S m–1 for copolymer doped with FeCl3.

An experimental investigation on the mechanical performance of epoxy-coated Alkali-Resistant (AR) glass textile reinforced mortar subjected to elevated temperature is presented. Two epoxy coatings are considered, which differ by the hardening agent alone. After 56 days dry curing, specimens are heated up to four different temperatures. After cooling down to ambient temperature, specimens are assessed in uni-axial tensile test according to Annex A of AC434. First cracking strength and elongation, ultimate tensile strength and elongation, cracked and uncracked moduli, transition point location and energy dissipation capability are evaluated. It is found that, in the explored temperature range, degradation is surprisingly mild and strongly dependent on the resin which is taken as coating agent. Indeed, temperature exposure may lead to strength enhancement. This positive outcome takes place at the expense of ductility and it is traced back, through Differential Scanning Calorimetry (DSC), to a post-curing process. Nonetheless, energy dissipation still decreases with temperature and, remarkably, with the same power-law behaviour for both resins. Such behaviour is compatible with a cumulative Weibull distribution, that is adopted in thermal damage models for resins, and it indicates that the underlying damage mechanism indeed operates on the resin at the fabric-to-matrix interface.

Polymeric nanocomposites containing Fe3O4 nanoparticles were prepared through a chemical route under different precursor-to-solvent ratios and were submitted to structural and morphologic characterization. The embedded nanoparticles, containing pure magnetite and characterized by considerable polydispersity, are rather homogeneously dispersed in the matrix. The magnetic properties of two representative samples were analyzed in detail between T = 5 K and room temperature. Magnetic effects clearly associated with the Verwey monoclinic to cubic transition with transition temperatures distributed in the interval 95–120 K were put in evidence. On heating through this region, the coercive field and the maximum susceptibility of hysteresis loops display marked downward/upward steps, respectively, while the high-field magnetization is not affected at all; a comparable upward step is measured in the FC/ZFC curves. Reporting the maximum susceptibility as a function of the reciprocal of the coercive field in the interval from T = 95 to T = 120 K, and using the predictions for single-domain nanoparticles with randomly distributed axes of uniaxial and cubic anisotropy (the former/latter case being applicable below/above the Verwey transition, respectively), the evolution of the transformed cubic-anisotropy fraction upon heating has been studied, and the distribution of Verwey transition temperatures related to the sample polydispersity has been accurately determined. The low-temperature value of the uniaxial anisotropy constant is obtained from coercive field measurements and found to be comparable to, albeit slightly higher than the corresponding quantity measured in bulk crystalline magnetite.

In recent years, biopolymers have been attracting the attention of researchers and specialists from different fields, including biotechnology, material science, engineering, and medicine. The reason is the possibility of combining sustainability with scientific and technological progress. This is an extremely broad research topic, and a distinction has to be made among different classes and types of biopolymers. Polyhydroxyalkanoate (PHA) is a particular family of polyesters, synthetized by microorganisms under unbalanced growth conditions, making them both bio-based and biodegradable polymers with a thermoplastic behavior. Recently, PHAs were used more intensively in biomedical applications because of their tunable mechanical properties, cytocompatibility, adhesion for cells, and controllable biodegradability. Similarly, the 3D-printing technologies show increasing potential in this particular field of application, due to their advantages in tailor-made design, rapid prototyping, and manufacturing of complex structures. In this review, first, the synthesis and the production of PHAs are described, and different production techniques of medical implants are compared. Then, an overview is given on the most recent and relevant medical applications of PHA for drug delivery, vessel stenting, and tissue engineering. A special focus is reserved for the innovations brought by the introduction of additive manufacturing in this field, as compared to the traditional techniques. All of these advances are expected to have important scientific and commercial applications in the near future., Bioengineering, 8 (2), ISSN:2306-5354

In order to develop new electronic devices, it is necessary to find innovative solutions to the eco-sustainability problem of materials as substrates for circuits. We realized a photoresponsive device consisting of a semiconducting polymer film deposited onto optically semitransparent and conductive biodegradable poly(3-hydroxybutyrate) (PHB)/carbon nanotube (CNT) substrates. The experiments indicated that the PHB-CNT bionanocomposite substrate behaves as an optical window trapping electric charges produced by the photoexcitation of the semiconducting polymer. Such PHB-CNT functional substrates are expected to be attractive for eco-friendly electronics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 596–602

In this study, the effect of graphene nanoplatelets (GNPs) on the shape memory properties of poly(L-lactic acid) (PLLA) was studied. In addition to thermal activation, the possibility of infrared actuating of thermo-responsive shape mem- ory PLLA/GNPs nanocomposite was investigated. The incorporated GNPs were expected to absorb infrared wave's energy and activate shape memory PLLA/GNPs. Different techniques such as differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), field emission gun scanning electron microscope (FEG-SEM) and dynamic mechanical thermal analysis (DMTA) were used to characterize samples. DSC and WAXD results indicated that GNPs augmented crystallinity due to nucleating effect of graphene particles. GNPs improved both thermal and infrared activating shape memory properties along with faster response. Pure shape memory PLLA was slightly responsive to infrared light and its infrared actuated shape recovery ratio was 86% which increased to more than 95% with loading of GNPs. Drastic improvement in the crystallinity was obtained in nanocomposites with lower GNPs contents (0.5 and 1 wt%) due to finer dispersion of graphene which resulted in more prominent mechanical and shape memory properties enhancement. Infrared activated shape memory PLLA/GNPs nanocomposites can be developed for wireless remote shape control of smart medical and bio-systems.

Hydroxyapatite (HA) filled poly(methyl methacrylate)/poly(hydroxyethyl methacrylate) (PMMA/PHEMA) blends were prepared by reactive suspension method: HA was synthesized by co-precipitation process directly within a HEMA solution and the so-obtained suspension was polymerized in the presence of PMMA. HA particles were obtained in form of nanorods with a length of 50–200 nm and a diameter of 10–30 nm. A significant increase in glass transition temperature was observed in the nanocomposites with respect to the unfilled polymer blends. Dynamic-mechanical thermal analysis showed a significant increase in the storage modulus in the nanocomposites measured in the rubbery region. This increase was unpredicted by Mooney’s predictive equation and was attributed to the presence of cross-linking points due to the in situ generated HA particles. An increase in the elastic modulus was also observed at room temperature in compression and three-point bending tests. The presence of HA in the polymer blends resulte...

The capability of the Atmospheric Pressure Plasma Treatment (APPT) to increase the shear strength of adhesively bonded Single Lap Joints (SLJ) realized with polymeric adherends was investigated, by exploring the different response obtainable by changing the surface-to-nozzle distance and the treatment speed and by considering an industrial application as target. Beyond APPT, abrasion and chemical treatments were also performed and considered as reference. Three thermoplastic resins were used as adherends: polypropylene (PP), polyethylene (PE) and polyamide 66 (PA66). In addition to the mechanical characterization, even the variation of the surface free energy associated with the different combinations of parameters employed for the APPT was evaluated by means of optical contact angle (OCA) measurements. Moreover, for some representative combinations of substrates and APPT parameters, the changes of the polymer chemical structure were assessed by means of infra-red spectroscopy (IR). Finally, the sensitivity of the mechanical behavior to the time between the treatment and the deposition of the adhesive was assessed. The results showed that, in a plasma treated joint, a decrease of the surface-to-nozzle distance assured however an increase of the shear strength with respect to the chemical treated samples, provided that the treatment speed was correspondingly risen up. The trend of the wettability with the process configuration appeared to be consistent with the one exhibited by the joint shear strength, while any apparent influence of the delay time was detectable within 24 h, which allowed to assume that APPT represents a reliable pre-treatment technique for industrial applications.

Solid wine wastes named wine lees (WL) have been mixed in different percentages (10, 20 and 40 phr) within Polyamide 11 (PA11) and Polybutylene Succinate (PBS) by twin-screw extrusion. Reactive extrusion has been also tested using 3-methacryloxypropyltrimethoxysilane tested as coupling agent. The obtained bio-composites have been characterized from a thermal (DSC, TGA, HDT), rheological (MFR), mechanical (tensile test) and thermo-mechanical (DMA, creep test) point of view. Micro-mechanics models of Voigt, Halpin-Tsai and Pukanszky have been fitted on tensile properties data meanwhile the creep behavior has been modeled and described through the models of Burger, Kohlrausch-Williams-Watts and Findley.

The limited availability of materials with special properties represents one of the main limitations to a wider application of polymer-based additive manufacturing technologies. Filled resins are usually not suitable for vat photo-polymerization techniques such as stereolithography (SLA) or digital light processing (DLP) due to a strong increment of viscosity derived from the presence of rigid particles within the reactive suspension. In the present paper, the possibility to in situ generate silver nanoparticles (AgNPs) starting from a homogeneous liquid system containing a well dispersed silver salt, which is subsequently reduced to metallic silver during stereolithographic process, is reported. The simultaneous photo-induced cross-linking of the acrylic resin produces a filled thermoset resin with thermal-mechanical properties significantly enhanced with respect to the unfilled resin, even at very low AgNPs concentrations. With this approach, the use of silver salts having carbon-carbon double bonds, such as silver acrylate and silver methacrylate, allows the formation of a nanocomposite structure in which the release of by-products is minimized due to the active role of all the reactive components in the three dimensional (3D)-printing processes. The synergy, between this nano-technology and the geometrical freedom offered by SLA, could open up a wide spectrum of potential applications for such a material, for example in the field of food packaging and medical and healthcare sectors, considering the well-known antimicrobial effects of silver nanoparticles.