Acrytonitrile block copolymers

Summary Acrylonitrile was polymerized by an insertion process on being added to solutions containing the adduct of the reaction of tetrakis(dimethylamino) titanium (T4) and azobisisobutyronitrile (AIBN). The obtained azo-linked polyacrylonitrile has appropriate initiating functionality for a subsequent vinyl polymerization.     

The effects of different greenhouse covering materials on energy requirement,growth and yield of aubergine

Effects of UV stabilised polyethylene (UV+PE), IR absorbers polyethylene (IR+PE), double layers of polyethylene (D-Poly) and single layer of polyethylene (PE), as greenhouse covers, on aubergine growth, productivity and energy requirement were investigated in a late autumn season (2001). The late and final yields of plants grown in D-Poly houses were higher than those grown in UV+PE, IR+PE and PE. Light transmission was the highest in PE, intermediate in UV+PE and IR+PE, and the lowest in D-Poly houses. Relative humidity was the highest in D-Poly, intermediate in IR+PE and UV+PE, and the lowest in PE houses. The plants in D-Poly houses grew and developed faster (more leaves and flowers) than those in IR+PE, UV+PE and PE houses. Plant growth and development in UV+PE and IR+PE houses was similar. Economic analyses showed that aubergine production was economically viable in D-Poly, UV+PE and IR+PE houses. For aubergine production in climatic conditions similar to Black Sea Region, the D-Poly greenhouse is strongly recommended, because there was a higher productivity and a lower heating requirement in comparison to UV+PE, IR+PE and PE houses.     

The Effect of Hydrothermal Aging on the Low-Velocity Impact Behavior of Multi-Walled Carbon Nanotubes Reinforced Carbon Fiber/Epoxy Composite Pipes

Chemical transmission lines, petroleum and natural gas lines, pressure vessels, and pipes used in thermal facilities are expected to maintain their mechanical properties for many years without being damaged and not to be corroded in working conditions. The composite materials are the right candidate for these harsh conditions due to their superior properties. Reinforcement of nanoadditives to composite materials improves both the mechanical properties and the resistance to environmental conditions, thereby increasing the lifetime. In this study, multi-walled carbon nanotube (MWCNT) reinforced [±?55°] carbon fiber/epoxy composite pipes produced with filament wound method were used. It was hydrothermally aged in 80 °C distilled water for 1, 2, 3 weeks in order to examine the effect of environmental conditions. In order to investigate its resistance against loads that may occur in working conditions, ring tensile tests (ASTM D 2290–16 procedure A), and low-velocity impact tests at 5, 10, 15 J, energy levels were carried out. The effect of hydrothermal aging on neat and MWCNT added epoxy composite had been examined by considering the aging period. Consequently, the impact resistance of neat and MWCNT added samples decreased with the aging process. Besides, tangential tensile strength loss was 17% in MWCNT reinforced sample and 13% in the neat sample.

     

Evaluation of machining performance in cryogenic machining of Inconel 718 and comparison with dry and MQL machining

There has been significant work on establishing relationships between machining performance and the cutting parameters for various work materials. Recent trends in machining research show that major efforts are being made to understand the impact of various cooling/lubrication methods on machining performance and surface integrity characteristics, all aimed at improving process and product performance. This study presents the experimental results of cryogenic machining of Inconel 718, a high-temperature aerospace alloy, and comparison of its performance in dry and minimum quantity lubrication machining. Experimental data on force components, progressive tool wear parameters such as flank wear, notch wear, crater wear, cutting temperature, chip morphology, and surface roughness/topography of machined samples are presented. New findings show that cryogenic machining is a promising research direction for machining of high-temperature aerospace alloy, Inconel 718, as it offers improved machining performance in terms of reduced tool wear, temperature, and improved surface quality. It was also found that the number of nozzles in cryogenic machining plays a vital role in controlling cutting forces and power consumption in cryogenic machining of Inconel 718.     

Automatically tuned boring bar system

This paper introduces a boring bar system which includes an automatically tuned internal vibration absorber, called a tuned mass damper (TMD). The TMD head can be attached to boring bars with a wide range of lengths. An electromagnetic impulse force actuator is developed to measure the frequency response function (FRF) of the boring bar with an integrated power screw. A portable servo motor is attached to the power screw for adaptive tuning of the vibration damper's stiffness. The measurement and tuning cycle is automated until the negative real part of the FRF is optimized to maximize the chatter-free depth of cut. The system is experimentally validated on boring bars with a wide range of length to diameter ratios.     

Virtual CNC system. Part II. High speed contouring application

This paper presents a trajectory planning strategy for maintaining the tool positioning accuracy in high speed cornering applications. A 3D contour error estimation algorithm is presented for determining the geometric deviation from arbitrarily shaped toolpaths. Two spline fitting strategies are developed for smoothening sharp corners. The under-corner approach reduces the toolpath length, and therefore the cornering time. This technique yields successful results when used with a high bandwidth servo controller (such as sliding mode control), capable of accurately tracking the commanded toolpath. The over-corner approach is based on stretching out the sharp corner with a smooth curve, which counteracts the ‘undercut’ caused by the large phase lag in low bandwidth servo controllers (such as P–PI control). The cornering feedrate is adjusted in the Virtual CNC platform, developed in the first part of this article, to ensure that contour error violation does not occur. The achieved cornering accuracy is verified in experiments, which are in close agreement with predictions obtained with the Virtual CNC.     

Synthesis, characterization and electrochromic properties of a conducting copolymer of pyrrole functionalized polystyrene with pyrrole

A well-defined polystyrene (PSt) based polymer containing at one end-chain 3,5-dibromobenzene moiety, prepared by atom transfer radical polymerization (ATRP), was modified in two reaction steps. First one constitutes a Suzuki coupling reaction between aromatic dibromine functional polymer and 3-aminophenylboronic acid, when a diamino-containing intermediate was obtained. The second step is a condensation reaction between the diamino functional polystyrene and 2-pyrrole aldehyde. Thus, a polymer containing a conjugated sequence having pyrollyl groups at the extremities was synthesized. The presence of oxidable pyrrole groups in the structure of the polymer permitted further electropolymerization. The structures of intermediate polymers were analyzed by spectral methods (¹H NMR, FTIR). Electrochemical copolymerization of pyrrole functionalized polymer (PStPy) with pyrrole was carried out in acetonitrile (ACN)-tetrabutylammonium tetrafluoroborate (TBAFB) solvent electrolyte couple. Characterization of the resulting copolymer were performed via Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), spectroelectrochemical analysis, and kinetic study. Spectroelectrochemical analysis show that the copolymer of PStPy with Py has an electronic band gap (due to π-π* transition) of 2.4 eV at 393 nm, with a yellow color in the fully reduced form and a blue color in the fully oxidized form. Via kinetic studies, the optical contrast %ΔT was found to be 20% for P(PStPy-co-Py). Results showed that the time required to reach 95% of the ultimate T was 1.7 s for the P(PStPy-co-Py).