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Study of the crosslinking process of waterborne UV curable polyurethane acrylates
Progress in Organic Coatings, 2016
UV curable acrylic end capped polyurethane dispersions were obtained by the acetone process, using different molecular weight polyols. Photo Differential Scanning Calorimetry (Photo-DSC) was employed to study the effect of the photoinitiator concentration as well as the curing temperature in the curing reaction rate. The penetration capacity of UV radiation was determined by "in situ" Attenuated Total Reflectance Infrared Spectroscopy (ATR-FTIR). In addition, Temperature Modulated Differential Scanning Calorimetry (TM-DSC) was used to calculate the crosslinking degree through the measurement of the Heat Capacity (Cp). According to Photo-DSC data, the conversion of the curing reaction increased with temperature and no dependence with the photoinitiator concentration was found. Cp values of the cured samples enabled us to compare the crosslinking degree as a function of photoinitiator concentration, polyol molecular weight and curing temperature.
Controlled Light Cross-Linking Technique to Prepare Healable Materials
Polymers
Detection of defects, damages and cracks in structural polymers is very difficult, and even if they are detected, they will be very hard to be repaired. This is because different kinds of stress can reduce the mechanical efficiency of structural and functional thermosetting composite materials and they can damage the polymer matrix, thus reducing the purposed properties. General healing processes use thermal energy "alone" to heal these materials, thus impairing the intended properties of the materials. Therefore, we present a thermal healing ability that can be switched-on and/or-off at desire using illumination by photon energy (visible and ultra violet). By this technique, one can control local heal while keeping the efficiency of the material nearly unchanged. Furan-based cross-linker chemically reacts (forward-and reverse-reaction) with short-chains of maleimide-substituted poly(lauryl methacrylate) to form robust chemical bonds. This permits us to perform local control over thermally induced de-and/or re-cross-linking techniques. One can extend and apply this technique to cover micro-devices, coating-techniques, fine lithography, micro-and nano-fabrication processes, etc. Therefore, the present work developed a suitable technology with structural polymeric material, which has the ability to self-heal cracks (and damages) and recover structural function.
Crosslinking of Polylactide by High Energy Irradiation and Photo-Curing
Molecules, 2020
Polylactide (PLA) is presently the most studied bioderived polymer because, in addition to its established position as a material for biomedical applications, it can replace mass production plastics from petroleum. However, some drawbacks of polylactide such as insufficient mechanical properties at a higher temperature and poor shape stability have to be overcome. One of the methods of mechanical and thermal properties modification is crosslinking which can be achieved by different approaches, both at the stage of PLA-based materials synthesis and by physical modification of neat polylactide. This review covers PLA crosslinking by applying different types of irradiation, i.e., high energy electron beam or gamma irradiation and UV light which enables curing at mild conditions. In the last section, selected examples of biomedical applications as well as applications for packaging and daily-use items are presented in order to visualize how a variety of materials can be obtained using s...
Photosensitive Formulation for Additive Manufacturing-3D Printing
Materiale Plastice
UV curing is a photochemical process in which high-intensity ultraviolet light is used to instantly cure or ��dry�� coatings, inks, adhesives and thin film technology. It has been around as a coating for wood, paper and as a clear coating via photolithography process on printed circuit boards PCBs or integrated circuit boards ICBs for years. It is fast becoming one of the most popular techniques in the paint and coatings industry. Most of the formulation use multifunctional acrylate monomers or oligomers or a mixture of them that crosslink under exposure to UV/EB radiations in a free radical process. We briefly present the advantages of EB vs. UV. A new type of formulation based on multifuctional monomer of dicyclopentadiene epoxy derivative with additional diluent as co-reactive solvent will be described and evaluated. This formulation differs from the acrylate one by the use of a cationic photoinitiator. The final product presents all the advantages of epoxy resins viz. better adh...
Journal of Photopolymer Science and Technology
This paper presents the effect of UV-LED and UV-mercury as the light source toward curing behaviour of urethane acrylate coating. The UV-curable coating was prepared based on aliphatic urethane acrylate oligomer, 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), and commercial photoinitiator. The effect of irradiation time on curing behaviour was investigated using Fourier Transform Infra-Red (FTIR) and the percentage of C=C conversion was calculated. From the ATR-FTIR spectra, the C=C absorption peak at 810 cm-1 and 1635 cm-1 was found to be decreased after UV irradiation, indicated the proceeding of the polymerisation reaction. In term of C=C conversion, UV-LED irradiation showed better results with 97-99% than UV-mercury irradiation which is 86-96%. It was also observed that the tackiness of the coating reduced via UV-LED irradiation, suggesting higher conversion of monomers. Gel fraction of the coating also measured and higher gel fraction values, > 98% in this study was associated with higher cross-linking density. The results of this study depicted that UV-LED is a viable alternative to replace UV-mercury-based lamp in the coating industry.
UV curable urethane acrylate coatings formulation: experimental design approach
Pigment & Resin Technology, 2014
Purpose -The purpose of this work was to perform a systematic study on the effect of formulation on the physical and mechanical properties of ultaviolet (UV) curable urethane acrylate resins. In addition, the authors wanted to derive mathematical formula for the prediction of physical and mechanical properties for the aforementioned system. Design/methodology/approach -The experiments were carried out based on mixture experimental design to determine the effect of different multifunctional acrylates (i.e. 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), trimethyolpropane triactylate (TMPTA)) concentration on the physical and mechanical properties of a UV curable polyurethane acrylate system. The urethane oligomer was synthesized and characterized by the research team. Microhardness, adhesion strength and scratch resistance of the cured films were evaluated as the physical and mechanical properties. Findings -The results revealed that the resin and TMPTA concentrations had the most significant effects on the microhardness property. Adhesion strength of the films showed a linear trend with respect to all variables. Moreover, all components also had a significant and complex influence on the scratch resistance of the cured systems. In addition, mathematical equations proposed by mixture experimental design were derived for all the mentioned properties.
Polymer, 2020
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