Addition Of Reactive Diluent Research Articles

Effect of addition of reactive diluent on the thermal and mechanical properties of alumina/epoxy composites

Effect of addition of reactive diluent on the thermal and mechanical properties of alumina/epoxy composites

The effect of reactive diluent on mechanical properties and microstructure of epoxy resins

The effects of an aliphatic reactive diluent on the viscosity, gel time, chemical resistance, mechanical properties, fracture toughness, microstructure and relaxations of two different epoxy resins, i.e., a bifunctional and a multifunctional epoxy, were investigated. The gel time was not significantly affected by the diluent. The modulus and ultimate strength gradually declined, while the ductility steadily increased as the diluent content was increased. The failure mode of epoxy samples under flexural test changed from brittle to much more ductile upon the progressive incorporation of diluent into the epoxy resins. The strain at break of bifunctional resin improved by 75%, while that of multifunctional resin enhanced by more than 24%. The dynamic mechanical thermal analysis (DMTA) showed that the introduction of reactive diluent into different epoxy resins reduced the storage modulus at the glassy region and significantly broadened the glass transition region of the epoxy matrices with approximately no change in the glass transition temperature. The DMTA results also indicated increased microstructural heterogeneities upon the addition of diluent to the epoxy resins as evidenced by atomic force microscopy. The fracture toughness of epoxy resins enhanced with diluent content, about 20% and 29% increase for bifunctional and multifunctional resins, respectively. This was attributed to the improved material’s ductility and activation of plastic deformation in the epoxy resins upon the addition of reactive diluent.

Effect of Different Reactive Diluents on PDMS-PEG Hydrogels Properties

Polydimethylsiloxane (PDMS) is commonly used biomaterials for tissue engineering due to inert and nontoxic properties. However, there is the main drawback of PDMS which it is hydrophobic in nature. To overcome this limitation, PDMS was crosslinked with polyethylene glycol (PEG) in order to enhance it hydrophilic property. In this study, the effect of allyl methacrylate (AMA) and PDMS-MA 1K as reactive diluents in the hydrogel fabrication was investigated. Firstly, PDMS-SiH and PDMS-MA that was synthesized and had been confirmed with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). While for UV-crosslinked hydrogel, contact angle and swelling study were conducted. From the analysis, it was found that increasing in reactive diluents content increased the swelling with insignificant trend for contact angle result. Importantly, from this work the biocompatibility of produced PDMS-based hydrogel was enhanced with the addition of reactive diluents.

Structure characterization of UV-curing PEG-b-PPG-b-PEG dimethacrylate cross-linked network

The molecular structure of a series of newly developed ultraviolet (UV) curable electrical contact stabilization materials, which contain polyethylene glycol (PEG)-block-polypropylene glycol (PPG)-block-polyethylene glycol (PEG) capped with methacrylate functional groups on both ends as the reactive oligomers and a methacrylated PEG as the reactive diluent was studied in detail. The effects of reactive diluents, including functionalities and compositions were investigated via a combination of dynamic mechanical analysis, differential scanning calorimetry, FT-IR spectroscopy and wide angle X-ray diffraction. All the films exhibit completely amorphous state at room temperature regardless of the composition or thermal history. However, a small amount of PPPDI molecular chains undergo crystallization upon slow cooling. This crystallization is completely inhibited when mixed with di-functional reactive diluents, owing to the high cross-link density. The introduction of mono-functional reactive diluents restricts but not completely prevents the crystallization process, which causes the resulting films to be difficult to crystallize to lower crystallinity levels. On the other hand, adding non-reactive diluents transforms the resulting films to become a fast-crystallizing material, as a result of the low cross-link density and a large portion of unreacted oligomers along with the unreactive component. Additionally, the degree of heterogeneity for the cross-linked networks is generally increased by the addition of reactive diluents. The molecular structures of PEG-b-PPG-b-PEG dimethacrylate cross-linked networks as well as mixed with different types of reactive diluents at both room temperature and crystallizing temperature were proposed.

Synthesis and crosslinking kinetic study of epoxidized and acrylated/epoxidized oligoisoprenes: Comparison between cationic and radical photopolymerization

AbstractThe photoinitiated polymerization of epoxidized hydroxytelechelic cis‐1,4‐polyisoprene and of a dual system (epoxidized/acrylated) telechelic cis‐1,4‐polyisoprene in the presence of 2,2‐dimethyl‐1,2‐hydroxyacetophenone or/and hexafluoro‐phosphate triarylsulfonium salt has been studied by real‐time infrared spectroscopy. The synthesis of photosensitives oligoisoprenes was achieved by chemical modifications of hydroxytelechelic cis‐1,4‐polyisoprene obtained by controlled degradation of high molecular weight cis‐1,4‐polyisoprene. Then, the effect of light intensity, photoinitiator concentration, addition of reactive diluent and concentration of functional groups on the photopolymerization process was evaluated. Concerning the cationic process, the results showed that the kinetic profile improves when photoinitiator concentration and light intensity increase. The optimum concentration of triarylsulfonium salt used as photoinitiator was determined as 5% (w/w) and the optimum light intensity was 50 mW cm−2. Reactive diluent (3‐ethyl‐3‐hydroxymethyl oxetane) addition greatly improves the ultimate conversion and the polymerization rate. Subsequently, the photopolymerization kinetic of a dual epoxidized/acrylated system was studied. The results obtained using different photoinitiator mixtures and different intensity of irradiation showed that the crosslinking of acrylate functions at the chain‐end prevents the progression of the cationic process at the oxirane groups along the chain. Thus, the mobility of the cationic reactive centers was restricted by the crosslinking at the high conversion of the acrylate double bonds. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

3D-printing of Urethane-based Photoelastomers for Vascular Tissue Regeneration

AbstractThe mechanical properties of materials designated for vascular tissue replacement are of crucial importance. The elastic modulus, the tensile strength as well as the suture tear resistance have to be adjusted. Our approach is to use photopolymers for artificial vascular grafts. Via the layer-by-layer photopolymerization of suitable resin formulations as performed in additive manufacturing (AM) very complex structures are realizable. Hence AM offer the possibility to create cellular structures within the artificial grafts that might favor the ingrowth of new tissue. Commercially available urethane acrylates (UA) were chosen as base monomers since urethane groups are known to have good cell-adhesion behavior and poly-UAs show adequate mechanical performance. The mechanical properties of the photoelastomers can be tailored by addition of reactive diluents (e.g. 2-hydroxyethyl acrylate, HEA) and thiols (e.g. 3,6 dioxa-1,8-octane-dithiol) as chain transfer agents to comply with the mechanical properties of natural blood vessels. To examine the suture tear resistance a new testing method has been developed. Finally, a formulation containing 30 wt% UA and 70 wt% HEA complies with the mechanical properties of natural blood vessels, shows good biocompatibility in in-vitro tests and was successfully 3D-printed with digital light processing AM.

Preparation of biodegradable networks by photo-crosslinking lactide, ε-caprolactone and trimethylene carbonate-based oligomers functionalized with fumaric acid monoethyl ester

Biodegradable polymer networks were prepared from fumaric acid derivatives of oligomeric esters. Photo-crosslinkable macromers were prepared by reacting star-shaped hydroxyl-group terminated lactide, ε-caprolactone and trimethylene carbonate based oligomers and fumaric acid monoethyl ester in the presence of N,N-dicyclohexylcarbodiimide and 4-dimethylamino pyridine at room temperature. The functionalization method is facile and suited for many hydroxyl-terminated oligomers. The reactivity of the fumarate end groups is such that, upon crosslinking by UV radical polymerization, networks with high gel contents (up to 96%) can be obtained without the addition of reactive diluents. The physical properties of the networks can be tuned by adjusting the composition, architecture and molecular weight of the oligomeric precursors. Such networks, built up of non-toxic compounds and designed to release benign degradation products, may find wide application in tissue engineering and other areas of biomedical research.

Synthesis and characterization of uv‐curable acrylated urethane prepolymers, I. Effects of reactive diluents and relative humidity on physical properties

AbstractA UV‐curable acrylated urethane prepolymer was synthesized from tolylene‐2,4‐diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2‐hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent.The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films.The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.

Properties of UV‐curable polyurethane acrylates: Effect of reactive diluent

AbstractSeveral families of UV‐cured polyurethane acrylates were synthesized, and the effects of reactive diluent type and content on their physical properties were investigated. Increasing reactive diluent content promoted the development of a second, high glass transition temperature phase in all the materials, thereby leading to increased strength and modulus. Changes in the extensibility of the samples upon addition of reactive diluent were inversely related to the effect of the diluent on the crosslink density. The effects of using different reactive diluents (di‐, tri‐, and tetraethylene glycol diacrylate and N‐vinyl pyrrolidone) on the physical properties of the samples were attributed to differences in the softening point (Tg) of the homopolymer reactive diluents and the relative compatibility of the reactive diluents with the urethane acrylate segments.