Volume 35, Issue 7

Recently, ionic polymer-metal composites (IPMCs), which are becoming an increasingly popular material, have been used as soft actuators because of their inherent properties of light weight, flexibility, softness, especially efficient transformation from electrical energy to mechanical energy with large bending strain response under low activation voltage. This paper mainly focuses on a review on optical and micromanipulation applications of IPMCs as soft actuators. After presenting the general mechanism of sensing and actuating in IPMCs, recent progresses are discussed about the preparation process and practical technologies, especially for aided manufacturing techniques defined as the methods to fabricate IPMC into all kinds of shapes in terms of the demands, which are reviewed for the first time. Then, a number of recent IPMC applications for optical actuators, grippers and catheters are reviewed and investigated in this paper. Further developments and suggestions for IPMCs are also discussed. Extensive previous researches are provided for references in detail.

N,N-dimethylacrylamide (DMAA), 2-acrylamido-2-methyl-1-propyl (AMPS), dimethyl diallyl ammonium chloride (DMDAAC) and N-vinylpyrrolidone (NVP) monomers were copolymerized to synthesize a zwitterionic copolymer filtrate reducer. The results of Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) indicated that the molecular structure and chemical compositions of the quadripolymer matched with the design, and the result of the differential scanning calorimetry (DSC)-thermogravimetric analysis (TGA) showed that the polymer had good thermal stability. The effects of the quadripolymer on the properties and salt tolerance of drilling fluids were investigated. The environmental scanning electron microscope (ESEM) was used to observe the microstructure of the DMAA/AMPS/DMDAAC/NVP quadripolymer-bentonite system and filter cake of the drilling fluid added the copolymer. Results showed that a one space grid structure was formed by the molecular film with a hydrophobic association effect and electrostatic interaction between the groups in the positive and negative charges of the quadripolymer. It adsorbed and coated clay particles, and kept the particles distributing multilevels which contributed to forming a compact filter cake to reduce fluid loss. The spatial structure of the quadripolymer in drilling fluid could be destroyed partly by high temperatures, sodium and calcium, but the polymer still had a good effect on reducing fluid filtration.

The present study investigates the properties and structure of condensation non-isocyanate polyurethanes (NIPURs) prepared by reacting 2-hydroxy-6-naphthalenesulfonic acid (HNSA) with phenolsulfonic acid, urea and formaldehyde. Instrumental analyses confirmed a linear and segmented structure of the obtained condensation NIPURs. It was found that NIPUR films containing 20% HNSA and an equimolar ratio of rigid to flexible segments exhibited maximum values of tensile strength and tensile strain at break. All prepared samples showed a very high water resistance. The operating temperature of NIPUR samples based on HNSA was set between -33°C and +145°C. The first temperature was attributed to the glass transition of flexible segments, while the second one was associated with rigid segments melting. The higher the transition temperature, the higher the rigid segment content and the higher the HNSA content in the NIPUR sample.

Poly(aspartic acid) (PASP) hydrogel is a biodegradable and biocompatible polymer with high water absorbing ability. Traditionally, the production of PASP hydrogel consumes large amounts of organic solvents, i.e., dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). This traditional approach is now considered costly, complex and environmentally unfriendly due to required used solvent disposal. The present research explores two novel methods in preparing PASP hydrogel without organic solvent, by using hydrazine hydrate and ethylene glycol diglycidyl ether (EGDGE) or poly(ethylene glycol) diglycidyl ether (PEGDGE) as the cross-linkers. Absorbent ability and other characteristics are determined. Preparing PASP hydrogel in aqueous solution is promising and finds its use in many applications.

Carbon fiber (CF) reinforced polyetheretherketone (PEEK) is one of the most promising orthopedic implant biomaterials. In this paper, CF reinforced PEEK biocomposites were fabricated by hot press molding technology. The influence of the CF surface modification on the flexural mechanical properties of CF/PEEK biocomposites was investigated. Studies on the flexural mechanical properties of CF/PEEK biocomposites revealed that the flexural stress-strain behavior of the biocomposites possessed linear elastic characteristics. The fracture mechanism of the biocomposites was predominated by brittle rupture. Both flexural strength and modulus of the biocomposites obviously increased with the rise of CF content. The influence degree of different CF modification on the flexural properties of CF/PEEK biocomposites increased with the rise of CF content. Moreover, the CF modified by concentrated HNO 3 is beneficial for the flexural strength of the CF/PEEK biocomposites improvement. Conversely, CF modified by KH-560 coupling agent played an adverse influence on the flexural strength of the biocomposites.

In the present study, the effect of fiber and (5% wt) coconut shell powder (CSP) loading on the tensile properties of randomly oriented roselle fiber reinforced vinyl ester (RV) composites was carried out. Composite specimens were fabricated using the hand lay-up technique. It was observed that tensile properties of vinyl ester composites increase upon reinforcement with roselle fibers and CSP particles. The reinforcement of roselle fibers has significant effects on the tensile strength and modulus of the composite. The fractographic study was carried out on the surface of fractured composite specimens using scanning electron microscopy. A better interfacial adhesion, fiber dispersion and less fiber pull out on the surface of fractured composite specimens were identified. The tensile strength of RV composites has also been statistically analyzed by two-parameter Weibull distribution. Twenty-five tension tests were carried out. The results obtained varied between 37.89 MPa and 45.07 MPa. Furthermore, the inspection of the developed distribution was examined by the Kolmogorov-Smirnov (KS) test. The results show that the gained two-parameter Weibull distribution can be used to express the tensile strength and predict its values accurately.

This study explores the deformation behavior of polyamide in the process of backward extrusion at room temperature by both finite element (FE) and design of experiment (DOE) procedures. The distributions of effective strain through the length and the thickness of processed polyamide tube by cold backward extrusion are investigated and compared with ductile metals. The die parameters are comprised of slope angle, corner radius of punch and container which are selected as input parameters. The Taguchi DOE approach is exploited in order to decrease repeated simulations, after which 16 results are carried out. Analysis of variance is performed on simulation results, and it is proved that the corner radius of punch has the greatest effect among die parameters in the mentioned process, in reducing the processing load. The influence of this parameter is obtained as 98%. Eventually, the optimum condition is proposed. Also, the deformation behavior and the probability of failure based on the normalized Cockroft-Latham criterion are studied under this condition.

Poly(phenylene vinylene)/polyvinyl alcohol/Ag (PPV/PVA/Ag) composite nanofibers with excellent photoelectric properties were prepared by coaxial electrospinning using PPV/PVA as the shell and Ag nanoparticles (NPs) as the core, Ag NPs aqueous solution was prepared by the reduction method. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Ag NPs are of a face-centered cubic structure, with an average diameter of 46 nm and the composite nanofibers have uniform and continuous morphology. With increasing Ag content, the diameters of the composite nanofibers decreased from 653 nm to 250 nm. The X-ray diffraction (XRD) patterns verified that in the composite nanofibers, the Ag NPs are not transformed. In the photoluminescence spectra, the PPV/PVA/Ag composite nanofibers presented red-shift compared with PPV/PVA nanofibers. Under illumination, the as-prepared PPV/PVA/Ag composite nanofibers exhibited relatively high photocurrent intensity.

A transdermal therapeutic system (TTS) of diclofenac diethylamine (DDE) was developed to obtain a prolonged controlled drug delivery by the solvent evaporation technique. The matrix diffusion controlled systems used various combinations of hydrophilic (polyvinylpyrrolidone K30) and lipophilic (Eudragit RL 100 ® and Eudragit RS 100 ® ) polymers containing dimethyl sulfoxide (DMSO) (0, 5 and 10% w/w) as a penetration enhancer. In vitro drug release was improved with an increased fraction of hydrophilic polymer. Formulation F8 containing Eudragit RL 100 ® and polyvinylpyrrolidone K30 in the ratio 40:60 presented the highest drug release (92.45%) and permeation rate (0.0988±0.010 mg/cm 2 /h) with sustained release action for 48 h. In vivo pharmacodynamic study of DDE-loaded Eudragit RL 100 ® transdermal system (formulation F8) showed significant higher percent inhibition of rat paw edema compared with the marketed formulation of the drug. Our results suggest that a developed formulation is an efficient system for transdermal diclofenac delivery against inflammation. The optimized formulation was found to be stable and did not show physicochemical interaction. The system is envisaged to be stable for a sufficiently long period (2.52 years) at room temperature.

Polyvinylidene fluoride (PVDF) membranes were prepared via a thermally induced phase separation (TIPS) process using mixed diluent consisting of dibutyl phthalate (DBP) and dibutyl sebacate (DBS). The compatibility between PVDF and mixed diluent was predicted via the solubility parameter theory and verified by experimental results. The effects of mixed diluent composition on cloud point temperature, crystallization temperature, crystallinity, crystal phase and morphology of the membrane were investigated. As a result, as DBS mass fraction in mixed diluent increased, the cloud point temperature and the crystallinity increased, the crystal phase transformed from β phase to α phase and the morphology of the membrane cross-section changed from spherulitic structures to a bicontinuous structure. PVDF hollow fiber membranes were prepared successfully with the PVDF/DBP/DBS system via the TIPS method. The coagulant composition had a significant influence on the water permeability. When the dimethylacetamide (DMAc) content in the coagulant was 60%, the water permeability reached 877 l/m 2 ·h, while the rejection rate to the particles with a size of 200–500 nm was above 95%.