Effects of oligomer-to-monomer ratio on ink film properties of white UV-curable gravure ink for printing on biaxially oriented polypropylene (BOPP)

The high shear rate environment of gravure requires very low viscosity, fluid inks. The problems associated with low viscosity such as spilling, crawling, scumming and crazing, have hindered the development of UV-curable gravure inks. This led the researcher to study UV-curable gravure ink formulation. The effects of oligomer-to-monomer ratio and pigment dispersion loading on white ultraviolet (UV)-curable gravure ink film properties (surface cure efficiency, abrasion resistance, substrate adhesion, and ink film flexibility) were investigated. In this study, molecules normally used as monomers, in UV-curable systems, were selected as oligomers relative to the selected monomer, Glycerol Propoxylate Triacrylate (GPTA). The selected oligomers were, Trimethylolpropane Triacrylate (TMPTA), Trimethylolpropane Ethoxylate Triacrylate (ETMPTA), and a commercially available oligomer, Commerical Product A, used in flexographic ink applications. The outcome of this research created a starting point for white UV-curable gravure ink formulation, which will be used in the researcher\u27s family printing business. The results of the experiment showed that oligomer-to-monomer ratio did not have significant effects on surface cure efficiency, substrate adhesion, and ink film flexibility in the range from 70 to 90% oligomer concentration. Abrasion resistance was dependent on the type of oligomer. Using oligomer Commercial Product A, a soft oligomer, in combination with monomer Glycerol Propoxylate Triacrylate (GPTA), exhibited a decrease in abrasion resistance from 70:30 to 90:10 ratio. However, when using oligomers Trimethylolpropane Triacrylate (TMPTA) and Trimethylolpropane Ethoxylate Triacrylate (ETMPTA), oligomer-to-monomer ratio had no effect on abrasion resistance within the same range. Titanium dioxide pigment dispersion loading on 70:30 ratio (TMPTA:GPTA) did not have significant effects on substrate adhesion and ink film flexibility. Surface curing efficiency increased to 100% (from 99.5% with no pigment present) with pigment loadings equal to about 20%, but would begin to slightly decrease from complete curing at concentrations exceeding 40%. A significant decrease in abrasion resistance, caused by increased friction, was observed at 20 percent loading. There was, however, an increase in ink film strength from 30 to 50 percent pigment loading. Developments in UV ink components and persistent research will most likely solve the issues of UV-curable gravure inks. This research opened up a wide array of research opportunities in UV-curable gravure ink formulation and taken a step towards creating an effective white UV-curable gravure ink

Silane Surface Modification of Boron Carbide in Epoxy Composites

Boron carbide (BC) is used as a radiation absorber in the nuclear industry and particle physics experimentation. BC parts are generally manufactured through a sintering process, which limits the size and shape of components and imparts high cost. On the other hand, a polymeric matrix composite (PMC) with high BC content can be easily obtained through a moulding process, providing lower cost parts whilst accommodating increased complexity of geometry and size. Despite the importance of BC in industry, only a few studies have been carried out on epoxy PMCs containing only small amounts of BC. The lack of adhesion exhibited between BC and resin led to limited mechanical strength and durability. Hence, silane surface modification of BC particles was conducted with γ–glycidoxypropyltrimethoxysilane (GPS) as an aqueous solution to attain an 80%wt BC-epoxy PMC with improved strength and durability. Surface analysis on BC, and physical-chemical characterisation, mechanical testing and durability studies on the PMCs were conducted to better understand the effect of silane treatment and parameters (pH, %GPS). Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) confirmed boron oxide and hydroxyl groups on the native surface which can offer a means of attachment to the silane. Surface modification was more evident using higher GPS concentrations in pH5-7 solutions. These parameters were found to strongly affect the silane layer structure (crosslinking, density, thickness and coverage). Also, IR bands corresponding to B-O-Si were evident which are typically found on borosilicate glass. Increased hydrophobicity and adhesive wettability confirmed by sessile drop method, led to PMCs with higher density, lower porosity and reduced water permeability. Mechanical testing by means of three-point bending (3PB), Iosipescu and double v-notch (DVN) tests demonstrated correlations between strength improvement and the various surface modifications and physical-chemical characterisation. This was supported by SEM of the PMC failure surfaces, showing enhanced adhesion through distinguishable layers of epoxy and small BC particle clusters, remaining attached to the larger particles. This was due to a better adhesive wetting and stronger interfacial bonding. Optimal mechanical properties and durability were generally obtained using 0.5-1%GPS in pH5 solutions due to the combination of high initial strength and lower reductions in strength after ageing (water immersion)

Air pollution monitoring instrumentation A survey

Air pollution monitoring instrumentation developed for aerospace uses surveyed for industrial application

NASA Tech Briefs Index, 1978

Approximately 601 announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Emphasis is placed on information considered likely to be transferrable across industrial, regional, or disciplinary lines. Subject matter covered includes: electronic components and circuits; electron systems; physical sciences; materials; life sciences; mechanics; machinery; fabrication technology; and mathematics and information sciences

Powder and High-Solid Coatings

This volume illustrates some of the most innovative aspects of organic coatings designed not only to protect against corrosion but also to obtain smart coatings. Both modification of the composition of organic coatings and performance evaluation techniques are presented

New generation of interactive platforms based on novel printed smart materials

Programa doutoral em Engenharia Eletrónica e de Computadores (área de Instrumentação e Microssistemas Eletrónicos)The last decade was marked by the computer-paradigm changing with other digital devices suddenly becoming available to the general public, such as tablets and smartphones. A shift in perspective from computer to materials as the centerpiece of digital interaction is leading to a diversification of interaction contexts, objects and applications, recurring to intuitive commands and dynamic content that can proportionate more interesting and satisfying experiences. In parallel, polymer-based sensors and actuators, and their integration in different substrates or devices is an area of increasing scientific and technological interest, which current state of the art starts to permit the use of smart sensors and actuators embodied within the objects seamlessly. Electronics is no longer a rigid board with plenty of chips. New technological advances and perspectives now turned into printed electronics in polymers, textiles or paper. We are assisting to the actual scaling down of computational power into everyday use objects, a fusion of the computer with the material. Interactivity is being transposed to objects erstwhile inanimate. In this work, strain and deformation sensors and actuators were developed recurring to functional polymer composites with metallic and carbonaceous nanoparticles (NPs) inks, leading to capacitive, piezoresistive and piezoelectric effects, envisioning the creation of tangible user interfaces (TUIs). Based on smart polymer substrates such as polyvinylidene fluoride (PVDF) or polyethylene terephthalate (PET), among others, prototypes were prepared using piezoelectric and dielectric technologies. Piezoresistive prototypes were prepared with resistive inks and restive functional polymers. Materials were printed by screen printing, inkjet printing and doctor blade coating. Finally, a case study of the integration of the different materials and technologies developed is presented in a book-form factor.A última década foi marcada por uma alteração do paradigma de computador pelo súbito aparecimento dos tablets e smartphones para o público geral. A alteração de perspetiva do computador para os materiais como parte central de interação digital levou a uma diversificação dos contextos de interação, objetos e aplicações, recorrendo a comandos intuitivos e conteúdos dinâmicos capazes de tornarem a experiência mais interessante e satisfatória. Em simultâneo, sensores e atuadores de base polimérica, e a sua integração em diferentes substratos ou dispositivos é uma área de crescente interesse científico e tecnológico, e o atual estado da arte começa a permitir o uso de sensores e atuadores inteligentes perfeitamente integrados nos objetos. Eletrónica já não é sinónimo de placas rígidas cheias de componentes. Novas perspetivas e avanços tecnológicos transformaram-se em eletrónica impressa em polímeros, têxteis ou papel. Neste momento estamos a assistir à redução da computação a objetos do dia a dia, uma fusão do computador com a matéria. A interatividade está a ser transposta para objetos outrora inanimados. Neste trabalho foram desenvolvidos atuadores e sensores e de pressão e de deformação com recurso a compostos poliméricos funcionais com tintas com nanopartículas (NPs) metálicas ou de base carbónica, recorrendo aos efeitos capacitivo, piezoresistivo e piezoelétrico, com vista à criação de interfaces de usuário tangíveis (TUIs). Usando substratos poliméricos inteligentes tais como fluoreto de polivinilideno (PVDF) ou politereftalato de etileno (PET), entre outos, foi possível a preparação de protótipos de tecnologia piezoelétrica ou dielétrica. Os protótipos de tecnologia piezoresistiva foram feitos com tintas resistivas e polímeros funcionais resistivos. Os materiais foram impressos por serigrafia, jato de tinta, impressão por aerossol e revestimento de lâmina doctor blade. Para terminar, é apresentado um caso de estudo da integração dos diferentes materiais e tecnologias desenvolvidos sob o formato de um livro.This project was supported by FCT – Fundação para a Ciência e a Tecnologia, within the doctorate grant with reference SFRH/BD/110622/2015, by POCH – Programa Operacional Capital Humano, and by EU – European Union

Methods for testing high voltage connectors in vacuum, measurements of thermal stresses in encapsulated assemblies, and measurement of dielectric strength of electrodes in encapsulants versus radius of curvature

Internal embedment stress measurements were performed, using tiny ferrite core transformers, whose voltage output was calibrated versus pressure by the manufacturer. Comparative internal strain measurements were made by attaching conventional strain gages to the same type of resistors and encapsulating these in various potting compounds. Both types of determinations were carried out while temperature cycling from 77 C to -50 C

Pretreatments of fluoropolymers to enhance adhesion

The aim of the project was to gain a better understanding of the factors that affect adhesion of fluoropolymers. This was achieved by employing various analytical techniques to the treated and untreated polymers. The effects of novel pretreatments, and established treatments, on Polytetrafluoroethylene, PTFE, Poly (vinyl fluoride), PVF, and poly (vinylidene fluoride) PVdF, were characterised using: adhesion tests, X-ray photoelectron spectroscopy (XPS), including derivatisation reactions, Fourier Transform Infrared (FTIR), contact angles and scanning electron microscopy (SEM) For untreated PVF and PTFE it was found that a certain degree of adhesion improvement was achievable without any chemical modification of the surfaces. This was observed when the substrates were repeatedly bonded. It is proposed that weakly cohesive material was present in the polymers and these acted as weak boundary layers when bonded. Removal of weak boundary layers alone was found to be insufficient to obtain high adhesion with PTFE. Surface functionality, increased wettabiIity and favourable topography all contributed to the high bond strengths observed with 'Tetra-Etch' treated PTFE. 'Tetra-Etch' treatment is used commercially on PTFE but prior to this programme was unreported on PVF and PVdF. The treatment was effective at promoting adhesion for PVF though at a· much slower rate than for PTFE. Additional mechanisms to that for PTFE (Le. electron transfer) are proposed for the action of 'Tetra-Etch' on PVF. These are dehydrohalogenation through electron transfer and an elimination reaction. The same mechanisms are proposed for PV dF. Flame and Iow pressure plasma treatments·,w7re carried out on PVF and PTFE. Flame was found to be ineffective for PTFE but with PVF chemical modification (oxidation) occurred at the carbon/hydrogen sites. No defluorination was observed; this was in contrast to the mechanism of oxidation via plasmas on PVF, where defluorination, oxidation, ablation, and crosslinking may have all contributed to the high bond strength obtained. Certain plasma treatments were effective at improving the adhesion of PTFE but were slower and caused less modification. Removal of weak boundary layers was proposed as the major factor since oxidation was often slight. Reaction with solutions of potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium hydroxide (LiOH) were effective as adhesion pretreatments for PVF and PVdF but not for PTFE. For PVF and PVdF rates of reaction and chemical modification varied with time, temperature, molarity of solution and the nature of the solution i.e. aqueous or alcoholic. The greatest improvement in rate and effectiveness of the treatment for adhesion improvement was on the addition of a phase transfer catalyst to the aqueous solution. It was found for PVF that substantial surface oxidation could be achieved without improving the adhesion. It was suggested that oxidation occurred at sites present in a weakly cohesive layer. Mechanisms of the reactions were considered in terms of neucloephilic substitution and elimination; for PVF and PV dF both are likely. The mechanism of the phase transfer catalyst was investigated and found to be complex. It was found not to be simply a wetting agent but had inherent reactivity on its own. A combination of mechanisms was proposed