Radiation curing of 1,2 epoxy – phenoxy propane in the presence of an iodonium salt

Water diffusion and swelling stresses in ionizing radiation cured epoxy matrices

Abstract In this work a DGEBF epoxy monomer was cured by electron beam radiation in the presence of an iodonium salt and the obtained system was hydrothermally aged as such and also after a thermal treatment, in order to obtain two systems having different uniformity in the cross-linking degree. On both systems, the transient stress field arising from swelling was measured and monitored by an optical Photoelastic technique and the results were commented with reference to a thermally cured epoxy system containing the same monomer and already discussed in a previous work. Beam samples with identical dimensions, obtained from the irradiated systems, have been aged at 80 °C in water, and charac…

Properties of Epoxy-Pes systems as polymer matrices for carbon fiber composites produced by e-beam curing

Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies

The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant s…

Epoxy based matrices for structural composites prepared by ionizing radiation. Morphological and thermal behaviour

Radiation curing of epoxy resins in the presence of engineering thermoplastic: a way to produce nanostructured matrices for aerospace composites

Design, synthesis and characterization of a theranostic nanoplatform for tumor site-specific delivery of doxorubicin

Radiation curing of diacrylate glycerolate of bisphenol-A in the presence of an organically modified montmorillonite for the production of flame-resistant polymer–clay composites

Polymerization of an acrylate derivative of bisphenol-A by ionizing radiation in the presence of an organically modified montmorillonite was carried out in order to produce a flame-retardant composite. The measurement of the thermal effect during irradiation indicates that radiation curing of pure resin and resin-clay mixtures occurred in both cases. Moreover, differential scanning calorimetry and dynamic mechanical thermal analysis showed that a curing completion can be obtained by thermal curing after irradiation with a significant increase of the glass transition temperature. The morphology was investigated by X-ray diffraction and transmission electron microscopy. These have indicated t…

Devices for the capture of rare cells from biological samples for diagnostic purposes

The chance of surviving to a disease often depends on early diagnosis and effective therapy. In the field of early prenatal diagnosis, micromanipulation is a reliable technique for manual selection and isolation of rare fetal cells in maternal biological fluids for molecular or cytogenetic analysis. This technique allows obtaining pure cell populations for analysis, but it is expensive and time consuming, as it requires qualified and experienced staff and specific equipment [1]. This research aims at making the prenatal diagnosis more economical and reproducible in the hospital environment, by creating a device that allows selecting rare cells from biological samples in a semi-automated way…

Effetto dell’invecchiamento idrotermico sulle proprietà termiche e meccaniche di resine epossidiche strutturali

Le resine termoindurenti, utilizzate come matrici per materiali compositi rinforzati con fibre di carbonio, sono caratterizzate da un elevato grado di densità di reticolazione che conferisce loro una elevata fragilità e che allo stesso tempo le espone a significativi effetti di invecchiamento idrotermico durante il loro utilizzo [1]. In particolare si assiste alla diminuzione della temperatura di transizione vetrosa, per effetto di fenomeni di plasticizzazione e degradazione, e alla diminuzione di modulo elastico a flessione. Recentemente gli autori hanno proposto un metodo, Photoelastic Stress Analysis (PSA), molto efficace per monitorare le modifiche del materiale, in termini di swelling …

Thermal properties of e-beam cured epoxy/thermoplastic matrices for advanced composite materials

The aim of this work is to investigate the possibility to improve the thermal behaviour of epoxy based systems, cured by ionizing radiation, in order to produce matrices for advanced carbon fibres composites. Blends of two epoxy monomers, difunctional and trifunctional, have been polymerized by e-beam irradiation and the dynamic mechanical thermal properties have been investigated. The increase of the concentration of the trifunctional epoxy monomer in the blend causes a marked increase of the Tg, but strongly decreases the reactivity. Subsequently, blends of the same epoxy monomers with a high Tg thermoplastic toughening agent have been considered and their reactivity and the thermal prope…

Water diffusion and swelling stresses in highly crosslinked epoxy matrices

Abstract The present work investigates the swelling induced stresses arising in two epoxy systems during water uptake. The analysed systems are two epoxy resin based on DGEBA monomer and DGEBF monomer respectively, both fully cured by DDS amine. The systems achieve different cross-link density degrees, and are characterised by high glass transition temperatures ranging between 200 and 230 °C. Both epoxies have been conditioned in deionized water baths at two different temperatures (50 °C and 80 °C). A desorption process at room temperature in a dry airborne environment was performed after saturation. Dynamic Mechanical Thermal Analysis, carried out at the various stages of hydrothermal cond…

E-beam cross-linking of LDPE-OMMT nanocomposites and their photo-oxidation behaviour

“Ionizing radiation induced polymerization of epoxy resin in order to produce carbon fibre composites”

Idrothermal ageing of ionizing radiation cured epoxy matrices for carbon fibre composites

Radiation processing per la sintesi di nuovi materiali

DELAMINAZIONE INTERLAMINARE DI COMPOSITI CFRP AL VARIARE DELLE CONDIZIONI DI CURA DELLA MATRICE

In questo lavoro si è condotto uno studio sperimentale del comportamento a delaminazione interlaminare in Modo I di laminati compositi unidirezionali in fibra di carbonio e matrice epossidica (CFRP), al variare delle condizioni di cura della matrice. Tutti i sistemi analizzati hanno utilizzato lo stesso tessuto e lo stesso monomero epossidico DGEBA. Variando il processo di cura (cura termica o mediante radiazioni), gli agenti di cura (ammine o anidridi per i sistemi curati termicamente), e l’impiego di additivi tenacizzanti (es. il PES per i sistemi irradiati), è stato possibile controllare e modificare sia il grado di adesione fibra/matrice, che il grado di fragilità della matrice (monitor…

Realizzazione di Giunti Strutturali Mediante Polimerizzazione di Sistemi Adesivi Indotta da Fasci di Elettroni

Absorption kinetics and swelling stresses in hydrothermally aged epoxies investigated by photoelastic image analysis

Abstract The present work proposes an experimental optical methodology able to measure the transient swelling stresses induced by the water uptake ageing of polymers. In particular, the work describes the implementation of a Photoelastic technique to quantify internal stresses arising during the hydrothermal ageing of cast epoxy samples. The material investigated is a model DGEBA/DDS epoxy system. Curing and post-curing cycles have been optimised in order to obtain a fully cured, high T g , and completely stress free initial condition. Rectangular beam samples were then left in a hydrothermal bath at 90 °C, and regularly monitored by gravimetric and photoelastic analyses. The quantitative e…

Toughened epoxy matrices produced by e-beam irradiation

Processi di cura di resine epossidiche mediante radiazioni ionizzanti per la realizzazione si materiali compositi per il settore aerospaziale. Influenza delle condizioni operative sulle proprietà finali

Influence of Nylon 6,6 nanofiber mats on cure behavior and properties of CFR epoxy resin

In this work Nylon 6,6 nanofibrous mats produced by electrospinning were used as interlayers in carbon fiber reinforced laminates. A high crossilinked epoxy resin was chosen as matrix. The effects of polymeric mats on cure behavior, thermal and delamination properties of the composite laminates were investigated.

Radiation engineered nanogels as platform for next-generation of medical diagnostics and therapeutics

The durability of carbon fiber/epoxy composites under hydrothermal ageing

Studies on fibre reinforced composites are now receiving greater attention. Industrial applications have been successful in areas like aerospace, automobile, marine, construction and sporting goods. The first generation of epoxy resins for use in carbon fibre composites are able to achieve optimized high stiffness modules and high heat resistance by a high crosslink density, reached through thermal curing. However, these formulations can be very toxic and brittle with low crack resistance, which was a major disadvantage for structural applications. In the last years the use of ionizing radiation as alternative to thermal curing has been proposed as an environmentally friendly process. Furth…

Recombinant mussel protein Pvfp5β enhances cell adhesion of poly(vinyl alcohol)/k-carrageenan hydrogel scaffolds

Polymeric hydrogels are increasingly being considered as a scaffold for tissue engineering because they show similarity to the extracellular matrix (ECM) of many tissues. To control various cellular processes, hydrogels are often functionalized or loaded with various bioactive molecules such as: specific ligands for adhesion receptors, growth factors, hormones, enzymes, and other natural or synthetic regulators of cellular behavior [1]. Cell adhesion is essential for cell communication and regulation of the cell cycle and is therefore of vital importance in tissue engineering. Biomimetic approaches have been investigated to facilitate cell-scaffold adhesion interactions. In particular, the …

Rare cell capture platforms based on antibody-conjugated electrospun nanofiber mats for noninvasive prenatal diagnostics

The chance of surviving to a disease often depends on early diagnosis and effective therapy. In the field of early prenatal diagnosis, micromanipulation is a reliable technique for manual selection and isolation of rare fetal cells in maternal biological fluids for molecular or cytogenetic analysis. This technique allows obtaining pure cell populations for analysis, but it is expensive and time consuming, as it requires qualified and experienced staff and specific equipment [1]. The aim of this study is to make the prenatal diagnosis more economical and reproducible in the hospital environment, by creating a device that allows selecting rare cells from biological samples in a semi-automated…

Interlaminar fracture toughness behavior of electron-beam cured carbon-fiber reinforced epoxy-resin composites

The work describes the preparation and physical-mechanical characterization of unidirectional CFRP panels manufactured by an electron beam curing technique. Delamination fracture toughness in Mode I and II is investigated in order to evaluate the influence of fiber–matrix adhesion strength, matrix toughness and matrix crosslinking density as determined by the radiation curing process. A matrix system comprising a DGEBA epoxy monomer and an initiator of cationic polymerization have been used, with one batch of resin mixed with a PES monomer in order to enhance matrix toughness. Curing was achieved with a pulsed 10 MeV Electron Beam accelerator. Thermally cured composite systems have also bee…

The influence of the processing temperature on gamma curing of epoxy resins for advanced composites

Radiation curing of an epoxy resin based system under controlled temperature conditions

RADIATION CROSSLINKED ADVANCED WOUND DRESSING CONTAINING EGG WHITE PROTEINS

During the past decades, the use of antibiotics has grown worldwide in different fields, from medicine to agriculture, leading to antibiotic resistance of microbes, which is the cause of thousands of deaths every year worldwide. [1, 2] Finding new antibiotics is becoming more and more difficult because their development is no longer convenient in term of the cost–benefit ratio for the pharmaceutical industry. The interest in egg white proteins, such as ovoalbumin, ovotransferrin and lysozyme, has risen especially because of their demonstrated antimicrobial activities. [3] These antimicrobial proteins can then be used to enrich wound dressing films that requires a high level of control of mi…

Study of the curing of a DGEBA based system through structural investigation

Radiation curing of carbon fibre composites

Epoxy/carbon fibre reinforced composites were produced by means of e-beam irradiation through a pulsed 10 MeV electron beam accelerator. The matrix consisted of a difunctional epoxy monomer (DGEBA) and an initiator of cationic polymerisation, while the reinforcement was a unidirectional high modulus carbon fibre fabric. Dynamic mechanical thermal analysis was carried out in order to determine the cross-linking degree. The analysis pointed out a nonuniformity in the cross-linking degree of the e-beam cured panels, with the formation of clusters at low Tg (glass transition temperature) and clusters at high Tg. An out-of-mould post irradiation thermal treatment on e-beam cured samples provides…

Radiation Curing of Thermosetting- Thermoplastic Blends as Matrices for Structural Carbon Fibre Composites

Synthesis od epoxy/carbon fiber composites induced by e-beam. Study of the effect of hydrothermal ageing on thermal and mechanical properties

Fracture Toughness of Hydrothermally Aged Epoxy Systems with Different Crosslink Density

Abstract The present work investigates the fracture toughness behaviour of Single Edge Notched Bending (SENB) samples of epoxy systems subject to water uptake aging. Two epoxy systems with a significantly different Glass Transition Temperature, T g , are in particular considered: a typical commercial non-aeronautical grade resin matrix for composite applications, reaching a T g of 90 °C, and a DGEBA+DDS epoxy system achieving a T g of 230 °C.The materials have been conditioned by hydrothermal aging in a thermal bath at the temperature of 50 °C. TransmissionPhotoelastic Stress Analysisis carried outon SENB samples during water aging, monitoring the presence and evolution of swelling stresses…

Radiation sculpured nanogels as platform for novel therapeutic systems

Multifunctional and Bio-hybrid Hydrogel As bioartificial Matrices and Drug Delivery Devices

Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends. Thermal, mechanical and morphological behaviour

Abstract A model epoxy resin/anhydride system, modified with a polyethersulfone (PES) engineering thermoplastic toughening agent, has been studied under hydrothermal ageing in order to investigate the modification of the thermal, morphological and mechanical behaviour through dynamical mechanical thermal analysis, SEM microscopy and fracture toughness test respectively. Two different concentrations of the toughening agent were used in the blends and two ageing conditions have been considered, consisting of the immersion of the samples in distilled water at constant temperature of 70 °C for 1 week and for 1 month. Dynamical mechanical thermal analysis results on hydrothermally aged materials…

RADIATION CURING OF CARBON FIBRE COMPOSITES

Nano structured systems synthesised by ionizing radiation

Mode I fracture toughness behavior of hydro-thermally aged carbon fibre reinforced DGEBA-HHPA-PES systems

In this work the Mode I fracture toughness behavior of unidirectional CFRP laminates is investigated by means of Double Cantilever Beam (DCB) tests. The composite samples were manufactured by thermal curing after impregnation of a Carbon fabric with a DGEBA epoxy and anhydride HHPA curing agent. One resin batch was also mixed with a PES thermoplastic monomer to enhance the matrix toughness. Two lots of samples, toughened and un-toughened, were then left to soak in hot water to achieve various degrees of aging. The influence of matrix toughening and hydrothermal aging on the delamination behavior of the composite have then been assessed and correlated with characterization data from Dynamic …

Properties-morpholohy-processing relationships in the e-beam curing of epoxy resin-thermoplastic blends for advanced composite matrices

Review of photoelastic image analysis applied to structural birefringent materials: glass and polymers

Photoelasticity is particularly suitable for the analysis of the stress state in structural materials that are transparent and birefringent. Some techniques of digital photoelasticity (phase shifting and RGB) are applied to the analysis of stress field in two classes of structural materials. The first one consists of tempered glasses, such as those used in the automotive and architectural fields. The second one consists of thermoset polymers, typically used as matrices in fiber reinforced plastic structural composites. The birefringence of such resins is, in particular, exploited to investigate the development of swelling stresses and changes in fracture toughness as induced by water uptake…

Thermal and mechanical properties of polymer matrices for carbon fibre composites produced by radiation curing of Epoxy-Pes blends

Polymer matrices for composites obtained through radiation curing of epoxy resins

Hydrogel films engineered in a mesoscopically ordered structure and responsive to ethanol vapors

Abstract Responsive hydrogels filling the interstitial spaces of photonic crystals can form mesoscopically structured materials, which exhibit reversible shifts in the Bragg diffracted light as a response of environmental changes. These materials can be used to generate chemical or biochemical sensors. The present work reports on the synthesis and characterization of ethanol responsive hydrogels that can be used in the design of novel breathalyzers. The dynamic mechanical behavior of the macroscopic hydrogels and their swelling features in the presence of different liquids or vapors have been investigated to orientate the choice of the best responsive material and curing process. The swelli…

Matrici polimeriche nanostrutturate per materiali compositi ottenute mediante radiazioni ionizzanti

Recombinant mussel protein Pvfp5β enhances cell adhesion of poly(vinyl alcohol)/k-carrageenan hydrogel scaffolds

Polymeric hydrogels are increasingly considered as scaffolds for tissue engineering due to their extraordinary resemblance with the extracellular matrix (ECM) of many tissues. As cell adhesion is a key factor in regulating important cell functions, hydrogel scaffolds are often functionalized or loaded with a variety of bioactive molecules that can promote adhesion. Interesting biomimetic approaches exploit the properties of mussel-inspired recombinant adhesive proteins. In this work, we prepared hydrogel scaffolds with a 50%w mixture of k-carrageenan (kC) and polyvinyl alcohol (PVA), by a two-step physical gelation process, and we coated them with Perna viridis foot protein-5 beta (Pvfp5 be…

Effects of Nylon 6,6 Nanofibrous Mats on Thermal Properties and Delamination Behavior of High Performance CFRP Laminates

none 8 no Nylon 6,6 electrospun nanofibrous membranes interleaved in Carbon Fibre Reinforced Plastic (CFRP) laminates have been proposed as a means to provide a higher threshold value to delamination on structural sites where composites are more prone to develop such failure. A model, highly crosslinked thus inherently brittle, epoxy matrix was selected for its high Young’s modulus and glass transition temperature exceeding 250 °C. The influence of the Nylon 6,6 nanofibres on the curing behaviour of the matrix and on the thermal and dynamic mechanical properties of the cured resin was investigated. These properties were related to the features of the epoxy resin and of the resin impregnated…

Electrospun rubber/thermoplastic hybrid nanofibers for localized toughening effects in epoxy resins

Synthetic rubber/thermoplastic blends were electrospun from their solutions. The rubber was a solid acrylonitrile/butadiene/acrylic acid copolymer and the thermoplastic was polyacrylonitrile. The aims of this study were to identify suitable systems and processing conditions for obtaining rubber-based electrospun nanofibers, to investigate the ability of an epoxy resin system to impregnate and swell selected hybrid rubber/thermoplastic mats, and to assess the impact of the nanofibers on the resin morphology and curing behavior. In particular, electrospinning trials were carried out varying the composition of the feed solution and process parameters, such as the applied voltage, the flow rate…

Ionizing radiation induced curing of epoxy resin based systems for advanced composites matrices

High-energy radiation processing, a smart approach to obtain PVP-graft-AA nanogels

Abstract Poly(N-vinylpyrrolidone)-grafted-acrylic acid biocompatible nanogels (NGs) were prepared using an exiting industrial-type electron accelerator and setups, starting from semi-dilute aqueous solutions of a commercial PVP and the acrylic acid monomer. As a result, NGs with tunable size and structure can be obtained quantitatively. Sterility was also imparted at the integrated dose absorbed. The chemical structure of the NGs produced was confirmed through Fourier Transformer Infrared Spectroscopy (FT-IR). The molecular and physico-chemical properties of NGs, such as the hydrodynamic dimensions and surface charge densities, for various polymer and monomer concentrations in the irradiate…

The influence of the processing temperature on gamma curing of epoxy resins for the production of advanced composites

Abstract Gamma radiation curing of an epoxy monomer, in the presence of an iodonium salt, as initiator, is studied. Systems have been polymerized at the same irradiation dose and dose rate and at different processing temperatures. The experimental results show that all the irradiated materials exhibit a latent reactivity, undergoing toward an increase of crosslinking density if they are thermally cured after irradiation. The results indicate that the processing temperature affects both the crosslinking density after irradiation and the sensibility to the post-irradiation thermal treatment.

Influence of Polymer Electrospun Nanofibers on Thermal Properties of Epoxy Resins

Electrospinning of polymers has gained surging interest in the last decades due to its wide range of applications in different fields, such as sensors, electronic devices, separation systems, biomedical materials. Still there are only few reports on the use of these nanofibers as reinforcement in polymer composites. In this paper, solution electrospinning was employed to produce nanofibrous mats impregnating two epoxy resins to form “monolayer“ systems, with the aim to study the influence of the nanofibers on both the curing behaviour and the morphology of the resin systems. Three polymers were chosen for producing electrospun mats, a polysulfone (PSF), a polyamide Nylon 6,6 (Ny66) and a po…

POLYMER ELECTROSPUN NANOFIBERS AS INTERLEAVES FOR ENANCHEMENT OF CFRP LAMINATES DELAMINATION RESISTANCE

Electrospinning process is a technique to produce nanoscale fibers that has evinced more interest in recent years due to its versatility and potential for applications in several applications. The mall size and the concomitant ultra-high specific surface area of electrospun nanofibers make them suitable for several applications, such as tissue engineering, biosensors, filtration and advanced polymer composites (1). In particular for carbon fiber reinforced polymers (CFRPs) the huge specific surface area of electrospun nanofibers results in very large interfacial area between nanofibers and polymer matrix and therefore leads to substantial improvement of fiber-matrix interfacial interactions…

Hydrothermal ageing of radiation cured epoxy resin-polyether sulfone blends as matrices for structural composites

Abstract The hydrothermal ageing of epoxy–thermoplastic blends, used as matrices for carbon fibre composites, cured by electron beam, has been studied. Two different thermoplastic percentages have been adopted. A suitable choice of both curing process and formulation parameters allows to carry out irradiation at mild temperature with several advantages, coming from a “non thermal” process, for both the final properties of the materials and the environment. Nevertheless the occurring of vitrification phenomena needs the use of a short thermal treatment after irradiation on the already solid materials, in order to complete the cure reactions. Radiation cured epoxy based matrices have been sub…

Water diffusion and swelling stresses in ionizing radiation cured epoxies as matrices for carbon fiber composites

Cross-linking polymerization initiated by high energy radiation is a very attractive technique for the production of high performance composite materials. This method in fact offers many advantages compared to conventional thermal curing processes, due to the possibility to operate at mild temperature and in short time, limiting both energy and time consuming [1-2]. High performance composite materials mainly consist of epoxy resins as matrix and carbon fibers as reinforce, due to their excellent properties in terms of thermal and mechanical resistance. An important requirement of such systems for structural applications is their ability to maintain the properties within a fixed range durin…

κ-Carrageenan and PVA blends as bioinks to 3D print scaffolds for cartilage reconstruction.

3D printing of polymeric scaffolds and autologous stem cells is a promising tool for damaged facial cartilage reconstruction surgeries. To this end, suitable bioinks are needed to generate scaffolds with the required morphological and functional features. We formulated hydrogel bioinks using k-Carrageen (kC) and poly(vinyl alcohol) (PVA) in three different weight ratios. The kC gives the systems the ability to undergo rapid sol-to-gel transitions upon cooling from 60 °C and above to body temperature, while the PVA is used as rheology modifier and porogen. The latter is crosslinked after molding or printing by freeze-thaw cycling for 1 day (FT1) or 5 days (FT5). To select the most suitable f…

Macromolecular design and preparation of nanogels as pharmaceutical carriers

TEMPERATURE-TRIGGERED MACROSCOPIC GELATION OF IRRADIATED XYLOGLUCANS FOR BIOMEDICAL APPLICATIONS

Structural adhesive joints for transport applications

Sintesi di materiali avanzati mediante radiazioni ionizzanti

Carbon Fiber Composites Cured by γ-Radiation-Induced Polymerization of an Epoxy Resin Matrix

The use of ionizing radiation in order to initiate polymerization of suitable monomers has found increased interest in the last two decades due to its several advantages. In this work, carbon fiber composites through gamma radiation polymerization of epoxy matrices have been produced for aerospace and advanced automotive applications. Composite samples were produced by irradiation at room temperature using different radiation doses and, as reference, thermal curing of the same epoxy resin formulations was also carried out. Furthermore, some irradiated samples were subjected to postirradiation thermal curing to complete the polymerization reactions. The properties of the cured materials were…

Ionizing radiation induced curing of epoxy resin for advanced composites matrices

Abstract The radiation curing of an epoxy monomer in the presence of an iodonium salt, as photo initiator, is studied. Systems with different concentrations of photo initiators have been polymerized via both gamma rays and e-beam, at various dose rates. The aim of this work is to investigate how the photo initiator concentration and the irradiation dose rate affect the temperature of the systems during curing and how the different thermal histories influence the dynamic mechanical thermal properties of the obtained materials.

Fracture toughness of synthesised high-performance epoxies subject to accelerated water aging

Abstract The effects of water uptake on the fracture toughness of epoxy systems with high glass-transition temperatures (Tg above 170 °C) are investigated. Aging conditioning has been conducted in hot water, followed by a desorption conditioning in a room temperature dry-airborne. Water aging determines plasticisation effects and crosslink-density modifications, revealed by reductions of the Tg. It is less known how such modifications influence the material fracture toughness. In this study, Single Edge Notched Bending samples have been tested according to standards, to evaluate the KIC fracture toughness at different stages of water absorption-desorption. The characterisation has been supp…

Study of the Curing Process of DGEBA Epoxy Resin Through Structural Investigation

In this work, a multi-scale approach with different analytical methods is applied to study the curing process and the structural properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin. This monomer, thermally cured using 4,4′-diaminodiphenilsulfone (DDS) as hardener, is analyzed after 10, 45, 90, and 120 min of reaction time at 180 °C to obtain information on samples with different cross-linking densities. Samples are also characterized after extraction in acetone in order to obtain structural information on the insoluble parts. For this purpose, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), solid-state nuclear magnetic resonance (ss-NMR),…

Radiation engineering of functional biomaterials: from smart hydrogels to theragnostic nanodevices

Toughened matrices for advanced carbon fibre composites obtained through e-beam curing of two different epoxy-thermoplastic blends

Ionizing radiation curing of epoxy based blends in order to produce high performance composites

Effect of hydrothermal ageing on the thermal and delamination fracture behaviour of CFRP composites

Abstract This work investigates the hydrothermal ageing behaviour of a carbon fibre reinforced laminate and its epoxy matrix in bulk conditions. A model DGEBA epoxy is employed, and water uptake and dynamic mechanical thermal (DMTA) analyses have been performed on both the composites and bulk resin. Fracture toughness of the bulk resin has been measured, evidencing a substantially unmodified critical stress intensity factor KIC, although the evidence of plasticisation effects given by DMTA. Interlaminar Mode I fracture toughness of the composite showed a variable trend towards slight decreases or slight increases, according to the prevailing toughening or embrittling mechanisms activated by…

Solid State NMR Spectroscopy Investigation of the Molecular Structure of Epoxy Based Materials Cured in Different Conditions

In this work two epoxy resin model systems, whose monomers are typically used in structural composites, were thermally cured in different cure conditions in order to obtain different cross-linking densities. Their molecular structures were investigated through solid state NMR spectroscopy in order to correlate them to the cure process conditions used and the results were discussed in the light of the dynamical mechanical thermal analysis (DMTA) performed.

Influence of the e-beam irradiation and photo-oxidation aging on the structure and properties of LDPE-OMMT nanocomposite films

Abstract In this paper two systems, polyethylene (LDPE) and polyethylene/commercial organo-modified montmorillonite (LDPE/OMMT) nanocomposite, were subjected to e-beam irradiation at different doses and both the molecular modifications and mechanical properties have been investigated through solubility, FT-IR, calorimetric and tensile tests. Moreover, in some of the irradiated systems photo-oxidation aging was performed and its effects were studied. The results show an enhancement with irradiation of the positive effect of the nano-filler loading, related to the increase of the mechanical properties, due to the increase of the nano-filler polymer interaction. Nevertheless calorimetric and F…

Radiation-Engineering of All Plastic Nanocomposite Films

In recent years, polymer nanocomposites have fascinated scientists, engineers and industrialists on the premise that the creation of new and more performing polymeric materials is possible by the combination of different building blocks with controlled dimensions at the nanoscale. Unfortunately, uniform dispersion of the hetero-phase domains within the plastic matrix or on its surface often fails due to the unfavorable thermodynamics, thus resulting in migration and irreversible aggregation phenomena. In-situ generation of a dispersed hetero-phase within the same polymer matrix or in its precursors increases the chances of achieving a better control of morphology by eliminating the often cr…

Epoxy resin based matrices for advanced composites cured by ionizing radiation. Study of the influence of process parameters on final properties

Xyloglucan-based hydrogel films for wound dressing: Structure-property relationships

Thin xyloglucan-based hydrogel films have been synthetized and characterized in the prospect of producing wound dressings. Polyvinyl alcohol (PVA) and glycerol (Gro) were added to have an optimal combination of softness, conformability and resilience. Physical hydrogels have been transformed into permanent covalent hydrogels by reaction with glutaraldehyde (GA). Network structure-process-property relationships are discussed on the account of the results of several complementary characterizations: FTIR, rheology, thermal analysis, morphological analysis, moisture retention and swelling measurements. Selected formulations were also subjected to preliminary in vitro cytotoxicity tests. The phy…

Structural investigation of e-beam cured epoxy resins through solid state NMR

Abstract In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artef…

Radiation processing: a versatile methodology to tune the structure of polymeric materials

Photonic crystal hydrogel films responsive to ethanol vapors

Pulse radiolysis and theoretical investigation on the initial mechanism of E-Beam polymerization of epoxy resins. The results obtained on (phenoxymethyl)oxirane

Pulse radiolysis and theoretical investigation on the initial mechanism of the e-beam polymerization of epoxy resins. The results obtained on (phenoxymethyl)oxirane

Abstract The radical cation of (phenoxymethyl)oxirane ( PGE ⋅ + ) is generated by pulse radiolysis in dichloromethane solution and by direct action of radiation on the title compound. In the pure system its UV–vis spectrum is characterized by two bands at 340 and 430 nm, such that the electronic structure corresponds to a dipole bearing the positive charge on the phenoxy side. At the same time, the phenoxy-oxirane bridge is weakened. Then, the radical cation fragments into a phenoxonium ion and an oxyranylmethyl radical ( k PGE - fragm = 1.16 × 10 7 s - 1 ) . The latter immediately rearranges to an allyloxyl radical by ring opening. It is then conceived that the action of onium salts, as ra…

PROPERTIES OF IONIZING RADIATION CURED POLYMER MATRICES FOR CARBON FIBER COMPOSITES AFTER AGEING DUE TO MOISTURE ABSORPTION AND THERMAL TREATMENT

TENACITÀ ALLA FRATTURA INTERLAMINARE DI COMPOSITI CFRP SOTTOPOSTI A PROCESSI DI INVECCHIAMENTO IDROTERMICO

In questo lavoro si è condotto uno studio degli effetti dell’invecchiamento idrotermico sulla tenacità alla frattura interlaminare in Modo I di laminati in composito CFRP con lay-up unidirezionale. I pannelli realizzati impiegano una resina epossidica DGEBA. Provini DCB sono stati ricavati in accordo con la norma ASTM D5528. Prove dinamico meccaniche DMTA sono state condotte per analizzare l’influenza dell’invecchiamento sulla temperatura di transizione vetrosa, e quindi sul grado di fragilità della matrice. Il lavoro descrive il set-up sperimentale per la determinazione delle Curve R, evidenziando l’influenza della morfologia del tessuto in carbonio. I valori di GIC di innesco e di propaga…

Studies of network structure and dynamics of e-beam crosslinked PVPs: From macro to nano

Much interest has been paid to develop a variety of radiation-crosslinked hydrated polymeric materials, which swell in water but do not dissolve, as biocompatible materials used for wound healing, drug delivery system, surface-coating material for medically used devices, etc. With the aim of establishing design rules to produce hydrogels of controlled size at the nanoscale and desired internal network structure using conventional electron accelerators and set-ups, here we attempt a description in terms of structural and dynamic properties of polymer networks generated through e-beam irradiation of aqueous solutions of the same model polymer, a commercial grade poly(N-vinyl-pyrrolidone), sub…

Epoxy resin-thermoplastic blends as polymer matrices for carbon fiber composites

Hydrothermal aging of carbon reinforced epoxy laminates with nanofibrous mats as toughening interlayers

Electrospun mats have been applied as toughening interlayers in high performance carbon fiber epoxy composites. While the toughening mechanism exerted by the mat at the interface is the subject of several recent studies, no investigations are reported on the aging behaviour of laminates comprising these nanostructured elements. This work investigates the influence of the combined effect of water and temperature (90 °C) on laminates with Nylon 6,6 electrospun membranes placed either at the middle plane only or at each interlayer. The water-uptake behaviour is modelled by a two-stage diffusion model and compared with the behaviour of the neat resin and of the laminate without mats. Interestin…