Low-pressure plasma surface modification of polyurethane films with chitosan and collagen biomolecules

Polyurethane (PU) was synthesized using castor oil and a trade grade of hexamethylene diisocyanate, and then PU films were prepared for wound dressing applications. The PU films were then plasma treated with the low-pressure nitrogen plasma to functionalize with peroxide and hydroperoxide groups in order to attach with acrylic acid monomers. Therefore, the polyacrylic acid polymer branches were formed on the film surfaces. Carboxylic acid groups were activated by N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride/N-hydroxysuccinimide and bonded with chitosan and collagen biomolecules. Untreated, nitrogen plasma treated, polyacrylic acid grafted, and finally chitosan and collagen-immobilized PU films were characterized by several tests. The tests included the attenuated total reflectance Fourier transform infrared spectroscopy, static contact angle, atomic force microscopy, scanning electron microscopy, fibroblast L929 cell culture, and antibacterial activity assay to evaluate their in vitro cytocompatibility. The results confirmed that chitosan and collagen were immobilized successfully on the PU surfaces. The chitosan-immobilized PU and collagen-immobilized PU improved the adhesion and proliferation of fibroblast cells compared to untreated PU films. The chitosan-modified PU films exhibit the best antibacterial properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47567.     

Camouflage of cotton fabrics in visible and NIR region using three selected vat dyes

To provide camouflage in near infrared (NIR) region and imitate reflectance profile of greenish leaves, cotton fabrics were dyed with three selected vat dyes, namely C.I. Vat Blue 6, C.I. Vat Yellow 2, and C.I. Vat Red 13. Reflectance curves of two types of fresh greenish leaves were measured as standard reference. Transmittance curve of vat dyes in acetone solution indicated that selected vat dyes have suitable structure to provide camouflage in NIR region. According to reflectance profiles, reflectance curve of Vat Blue 6 has more similarity with that of green leaf at the concentration of 0.85% owf (on weight of fiber) and 1.2% owf in comparison with those of C.I. Vat Yellow 2 and C.I. Vat Red 13. Cotton fabrics were dyed with different mixtures of the dyes to obtain a standard shade to reach camouflage in visible range. Chromatic values of dyed fabrics were measured (CIE1976 L*, a*, and b*) and two standard shades of the 1948 US army pattern, NATO and forest green, were obtained on cotton fabrics with ΔE_CMC < 2. Reflectance profiles of these two shades were located between the reflectance of green leaves. So, two vat dyes were introduced to camouflage dyes group, C.I. Vat Blue 6 and C.I. Vat Red 13, and used to achieve NATO green and forest green shades for first time. All dyed samples showed good fastness properties. The effect of washing and light exposure on camouflage properties of fabrics in visible and NIR region was inconsiderable. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 200–207, 2014     

A robust scheduling of projects with time, cost, and quality considerations

CAM programs can generate cutting tool paths to be used by machining centres. Experience shows that CAM programmed feed rates are rarely achieved in practice during machining, especially when finishing free-form surfaces. These slower feed rates are due to the machines’ kinematic capabilities and behaviour of the numerical control (NC). To improve control over the machining process, applications need to be developed to predict the kinematic behaviour of the machines, taking the mechanical characteristics of the axes and NC capacities into account. Various models to simulate tool paths in linear and circular interpolation have been developed and are available in the literature. The present publication will first focus on the use of the polynomial model to simulate the behaviour of the machine when passing through transitions between programmed blocks with tangency discontinuities. Additional features are proposed to ensure enhancement of the match between the model and the machine’s behaviour. Analysis of machine behaviour shows that NCs do not always allow the axes to reach maximum performance levels, with an attendant loss in productivity. The present article proposes an optimisation procedure allowing control laws to be defined to reduce time spent in the transition. The contributions made by these optimised control laws are then evaluated, while impediments to their implementation are also considered.     

Comparison of the inhibitory capacity of vegetable oils,and their nonionic surfactants on Iran crude oil asphaltene precipitation using Quartz crystal microbalance

Asphaltene deposition is one of the main problems in some oil field production. Using the cheap chemical compounds to control asphaltene precipitation is one of the important tools in crude oil field development. Vegetable oil are natural chemical compounds which can be used as asphaltene stabilizer. In this work, the inhibitory capacity of the vegetable oils, their binary mixtures, and their binary mixtures with nonionic surfactants were studied by Quartz Crystal Microbalances. The results show that the turnip oil, binary mixtures of rosemary oil/sesame oil, sweet almond oil/camomile oil, and olive oil/tritoonX-100 are more efficient than other additives and the percentages of the inhibitory capacity are 87%, 89%, 90, and 90% respectively.