Mechanical and thermal properties of UV cured mixtures of linear and hyperbranched urethane acrylates

The properties of urethane acrylate resin mixtures based on the linear and hyperbranched aliphatic polyesters were examined. Linear polyester was synthesized from neopentil glycol and adipic acid. Hyperbranched polyester of the third generation was synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of 60% of hyperbranched aliphatic polyester OH end groups was carried out with isononanoic acid or with soybean fatty acids. Two hyperbranched urethane acrylates, with the same degree of acrylation, and one linear urethane acrylate were obtained by reaction of appropriate polyester and isophorone diisocyanate and 2-hydroxyethyl acrylate. The influence of added amount of HUA and nature of non-acrylic end groups on the rheological, mechanical and thermal properties of the uncured and UV cured mixtures diluted with 20 wt.% hexanediol diacrylate was examined. The nature of non-acrylic end groups have great effect on the interaction between linear and hyperbranched urethane acrylates, which further has a crucial influence on the examined properties of uncured and UV cured mixture samples.     

Anomalous swelling of a polystyrene matrix in organic solvents

Swelling behavior of a commercial linear polystyrene, containing a small amount (<5% wt) of mineral oil, has been studied in three different classes of organic solvents (alkanes, alcohols and carboxylic acids) using both gravimetry and light microscopy. A comparison has been made with the results presented in earlier publications using a different linear polystyrene, without mineral oil. It is shown that the polystyrene containing mineral oil absorbs much higher amounts of solvent at lower temperatures then at higher temperatures. This anomalous behavior sharply contrasts with the polystyrene without mineral oil, which at lower temperatures absorbs much less solvent. Light microscopy of the diffusion layer reveals that in the polymer with mineral oil precipitation occurs during diffusion at low temperatures, but not at high temperatures. These results clearly show that the presence of small amounts of mineral oil (in quantities below the detection limit of FTIR) can cause significant changes in the sorption behavior of polymers. These results are interpreted by pre‐existing nano‐inhomogeneities, formed by the mineral oil, limited miscibility of oil in the polymer phase and high miscibility of solvent in the oil phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The formulator's guide to anti-oxygen inhibition additives

Photo-curing has become increasingly popular in wood coating applications relative to thermally initiated processes due to increased curing rate with reduction in solvent and energy requirements. Stressing the last advantage, light emitting diodes (LEDs) utilize less energy and last longer than traditional Hg lamps and are commercially available now in wavelengths below 400 nm. Although photo-curing does have its advantages, an additional difficulty is encountered when this is performed in open-air since molecular oxygen inhibits radical polymerization. This leads to insufficiently cured films that remain tacky at the surface. Although nitrogen gas inerting can be highly successful in excluding oxygen, chemical additives are often preferable to the small and medium-sized enterprise (SME) end user. A variety of additives have been introduced over the last 30 years both in the scientific and patent literature. We have chosen to experimentally reinvestigate the applicability of some of these additives (hydrogen donors, functional monomers, reducing agents, CO₂ producing agents, and singlet oxygen scavengers), applying them to a urethane acrylate base formulation. Curing was performed with LED irradiation and effectiveness assessed by FTIR in transmission mode.     

Algorithmic and software techniques for embedded vision on programmable processors

In the last few years, programmable architectures centered around high-end DSP processors have emerged as the platform of choice for high-volume embedded vision applications, such as automotive safety and video surveillance. Their programmability inherently addresses the problems presented by the sheer diversity of vision algorithms. This paper provides an overview of high-impact algorithmic and software techniques for embedded vision applications implemented on programmable architectures and discusses several system-level issues. We provide a general discussion and practical examples for the following categories of algorithmic techniques: fast algorithms, reduced dimensionality and mathematical shortcuts. Additionally, we discuss the importance of software techniques such as the use of fixed-point arithmetic, reduced data transfers and cache-friendly programming. In our experience, each of these techniques is a key enabler for real-time embedded vision systems.     

Experimental design for parameter estimation of two time-scale model of photosynthesis and photoinhibition in microalgae

A method for parameter estimation of two time-scale model of photosynthesis and photoinhibition is presented.