Volume 34, Issue 2

The effect of gold nanoparticles (AuNPs) on the electronic transport in chitosan and chitosan/AuNPs films was experimentally and theoretically studied. The electronic properties (current-voltage curves) relative to the transport in the organic bulk in films were fitted to various models: space-charge limited current (SCLC), trap-charge limited current (TCLC) and scaling rule. However, it was found that the TCLC model, I TCLC ( V ) αV l +1 and scaling rule, I ( V ) α ( V - V T ) ξ , describes better the electronic transport in chitosan and chitosan/AuNPs films. Current-voltage ( I-V) curves showed an increasing conductivity with the AuNPs concentration. In addition, a bistable behavior was observed in chitosan/AuNPs films and it was attributed to the electron capture in the AuNPs. The results reported in this paper indicate that the electronic conductivity and bistable behavior in chitosan/AuNPs films could be controlled by the AuNPs incorporation on the chitosan matrix.

A light exposure degradation study of electrically active polymers – high-glass-transition-temperature poly(1,4-phenylenevinylene) (T g -PPV); poly(3-hexylthiophene-2,5-diyl) (P3HT); and poly(2-methoxy-5-(3′-7′- dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) – in pure form and blends with [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) was conducted to assess the influence of the employed transport layers on the materials’ photodegradation stability. Devices were prepared on quartz glass and silicon (Si) substrates with a transport layer prepared from poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) or titanium dioxide (TiO 2 ). Photodegradation processes in ambient air demonstrated that the polymers were thermally stable in the dark; thus, the material deteriorations not only were caused by thermal stress, but also from light-induced processes. Degradation processes of pure polymers may be considered as fast – in the order of hours – but retardable by blending of polymers with PCBM. The deposition of polymer blends on an additional layer of PEDOT:PSS or TiO 2 revealed that the polymer blends studied in this work (except for P3HT) presented higher stability against polymer chain scission when deposited onto the TiO 2 layer. Kinetic analysis undertaken during this work revealed that the photodegradation processes were followed by two degradation steps. Degradation kinetics were evaluated according to a Perrin-like model for absorption assessments and according to simple exponential for emission measurements.

Acrylamide (AM), 2-acrylamido-2-methypropane sulfonic acid, sodium styrene sulfonate (SSS), and N-vinyl pyrrolidone (NVP) monomers were copolymerized via a redox initiator system to synthesize a quadripolymer capable of reducing drilling fluid filtration. Fourier transform infrared spectroscopy (FT-IR) was used to determine the molecular structure of the product, confirming its successful synthesis. The effects of the copolymer on the properties and salt resistance of drilling fluid are discussed. The adsorption of the copolymer on bentonite was also studied using atomic force microscopy (AFM). The copolymer reduced the filtration of drilling fluids of various salinities before and after aging at 200°C; at room temperature, the copolymer was adsorbed uniformly across the bentonite surface at low concentration. As its concentration increased, the distributed polymer spread and connected to form a network. After aging for 16 h at 200°C, the copolymer could still adsorb to bentonite and maintained its network structure. Sodium ions induced the coalescence of the copolymer, damaging its network structure.

Soluble poly(ε-lysine)s bearing β-cyclodextrin (β-CD) moieties were prepared by three amino β-CD derivatives and N-succinylated poly(ε-lysine), in which the poly(ε-lysine) and amino β-CD derivatives were bonded covalently to the end carboxyl groups of succinic acid by peptide bonds. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDCI) and N-hydroxysuccinimide (NHS) were chosen to assist the reaction. The three poly(ε-lysine) derivatives were characterized by 1 H nuclear magnetic resonance ( 1 H NMR) and Fourier transform infrared (FT-IR). The synthesis process is simple, feasible and has strong practicability. The target polymers can serve as new polymer biomaterial for use in the biotechnology area.

Biocomposites incorporating cellulose fibres, a renewable resource, have high modulus and strength and flexibility suitable for structural applications. Solution casting, ultrasonication, and compression moulding methods were used to prepare the specimens. Results show that plasticiser indeed improved the flexibility of the composite and adding fillers further enhanced the performance of the composite.

The main purpose of the present work is to develop an artificial fingertip comprised of a soft layer and an inner rigid core, which emulates a human one with skin and bone. The influences of introducing the core and the effects of variations in thickness of the soft layer over the contact parameters are investigated. From the results, it is evident that the power law theory proposed by (Xydas N, Kao I. Int. J. Rob. Res. 1999, 18, 941–950) becomes invalid in this criterion; by contrast, if the power law theory acts for finger tips with internal cores, the conclusion may be redefined in such a way that the soft material behaves more softly in the presence of internal cores and the dimensionless number, core-soft layer coefficient F cs ≈0.5, is the critical parameter which produces the change of behavior. Moreover, soft finger tips with an inner core are preferable to entirely soft ones, as a higher grasping stability is achieved with the same area of contact, and the conforming nature of the fingers is maintained.

A quadripolymer of acrylamide (AM), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), N-vinylpyrrolidone (NVP) and dimethyl diallyl ammonium chloride (DMDAAC) was synthesized by solution free radical polymerization, and characterized using Fourier transform infrared (FTIR), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) methods. The rheological and filtrate properties of saturated brine-based fluid with AM/AMPS/NVP/DMDAAC quadripolymer were investigated before and after thermal aging tests. The apparent viscosity (AV), plastic viscosity (PV) and yield point (YP) increased and the filtrate volume decreased with increase in the concentration of AM/AMPS/NVP/DMDAAC quadripolymer after thermal aging test at 180°C for 16 h. The filtrate volume could be controlled when the concentration of AM/AMPS/NVP/DMDAAC quadripolymer reached 2.0% under these conditions. The filtrate volume of saturated brine-based fluid could be controlled effectively at a thermal aging temperature not exceeding 200°C and was smaller than that of the AM/AMPS/NVP terpolymer. The AM/AMPS/NVP/DMDAAC quadripolymer was better at improving the quality of a filter cake than the AM/AMPS/NVP terpolymer. The drilling fluid containing the AM/AMPS/NVP/DMDAAC quadripolymer had an excellent tolerance to salt and high temperature.

Within this study, the effect of functional additives and processing conditions on the overheating protection performance of thermotropic systems with fixed domains (TSFD) for overheating protection purposes was evaluated. The focus was on improving the overheating protection performance of a prototype TSFD based on a UV curable acrylate resin by optimization of the material constitution (addition of functional additives like surfactants and nucleating agents) and the processing conditions (temperature conditions during manufacturing, annealing). For the evaluated system, an effect of the nucleating agent on the overheating protection performance was ascertained. Furthermore, omission of an annealing step improved the overheating protection performance slightly.

The use of electromagnetic induction heating on achieving high mold temperature has been proven to effectively improve the appearance quality of injection molded parts. However, until now, the method has only successfully been used on heating small mold surfaces. This study aims to apply the method on a large injection mold that is used for producing 42-inch LCD TV frames. With the goals of achieving heating efficiency and uniformity, the main focus in this research is designing the induction coil. Initially, three types of induction coils – a single-layered coil with currents that flow in one direction, a single-layered coil with currents that flow in opposite directions, and a two-layered coil – were compared to confirm their heating rates; the best one was then chosen. Additionally, evaluation of various induction coils was preceded with commercial simulation software that supports electromagnetic and thermal analyses. An experiment involving heating a simple workpiece with a heated area similar to that of the male mold plate of the LCD TV frames was conducted to confirm its heating rate and uniformity. Real injection molding LCD TV frames assisted with induction heating was then carried out. Experimental results depicted that: (1) a single-layered coil with currents that flow in one direction performed best; (2) that it heated the simple workpiece at a high heating rate of 5.5°C/s with reasonable temperature uniformity (standard deviation: 5.1°C); and (3) induction heating of a 42-inch LCD TV frame mold surface in practical injection molding provided a high heating rate of 4.5°C/s with favorable temperature uniformity (standard deviation: 4.0°C).

Polystyrene was grafted onto oil palm empty fruit bunch (OPEFB) fiber in aqueous medium by using the H 2 O 2 /Fe 2+ system as an initiator. Optimization of the reaction conditions was carried out by varying the reaction period, temperature, amounts of the monomer, initiator and co-catalyst. The presence of the peaks around 3026 cm -1 , 698 cm -1 and 755 cm -1 in the Fourier transform infrared (FTIR) spectra of the grafted product and the presence of polystyrene on the surface of grafted OPEFB in the scanning electron micrograph provided strong evidence of the grafting. The maximum percentage of grafting (about 200%) was achieved when the reaction was carried on for 4 h at a temperature of 65°C, using 52.27 mmol monomer, 6.00 mmol initiator and 0.26 mmol co-catalyst. The thermal stability of the grafted OPEFB was found to be better than that of the ungrafted fiber, as seen from thermogravimetric analysis (TGA).

The properties of polyamide 6 (PA6)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends (60/40, wt%) compatibilized by poly(styrene-co-maleic anhydride) (SMA) were studied. The addition of SMA can form an in situ copolymer, SMA- graft -PA6. The SMA- graft -PA6 copolymer actually plays a key role as a compatibilizer to improve the interface between PA6 and PPO. It was found that the effect of compatibilization resulted in improvement of the morphology, impact strength and water absorbability of PA6/PPO blends (60/40, wt%), but with no favorable effects for thermal stability. However, at high SMA contents, the properties of PA6/PPO (60/40, wt%) blends deteriorated to some degree.