Aging Studies on Conducting Polypyrrole

Kaynak, Akif The Korean Fiber Society 2001 Fibers and polymers Vol.2 No.4

Change of tensile properties, electrical conductivity and microwave shielding of electrochemically synthesized polypyrrole films with time are presented. Highly doped films had good electrical stability, retaining high microwave reflectivity throughout the aging period. Lightly doped films were less stable and partially reflective and absorptive of microwaves. FT-IR spectral observations revealed a progressive increase in intensity of an unsaturated conjugated carbonyl peak, which was not observed in the highly doped films, suggesting that the concentration of the dopant had an influence on mechanism of degradation of conductivity.

Characterization of Conductive Polypyrrole Coated Wool Yarns

Kaynak, Akif,Wang, Kijing,Hurren, Chris,Wang, Xungai The Korean Fiber Society 2002 Fibers and polymers Vol.3 No.1

Wool yams were coated with conducting Polypyrrole by chemical synthesis methods. Polymerization of pyrrole was caned out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical Properties of the yam upon coating with conductive polypyrrole are Presented. Coating the wool yams with conductive Polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive Polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yin. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yam.

Uniform Micellization: The Key to Enhanced Mechanical Strength and Swelling Efficiency of Chitosan Hydrogel

Bijan Nasri-Nasrabadi,Akif Kaynak,Cynthia Wong,Pejman Heidarian,Khashayar Badii,Abbas Z. Kouzani 한국섬유공학회 2019 Fibers and polymers Vol.20 No.1

The fabrication of hydrophilic porous hydrogel, with high mechanical strength and good uptake capacity is desirable for a broad range of applications such as drug delivery and liquid sensors. The usual methods are limited to the production of structures with high density of covalently crosslinked networks that restricts the polymer chain rearrangement, resulting in non-uniformed pore size distribution. Covalent networks also limit the activity of functional groups and influence the uptake properties of the polymer. In this study, we proposed simple cyclic cryogelation for the fabrication of hydrogels with uniform pore sizes via controlling the micellization and crystal formation. The chitosan based hydrogels ionically crosslinked with 8 % (w/v) of tripoli phosphate sodium (TPP) displayed high Young’s modulus (63 MPa) after cyclic freezethawing. The liquid uptake capacity of the samples treated with 8 % (w/v) TPP solution at pH 4 showed a slight decrease of about 29 % in comparison to that of non-cyclic processed samples (36 %).

Correlating the Fineness and Residual Gum Content of Degummed Hemp Fibres

Beltran, Rafael,Hurren, Christopher J.,Kaynak, Akif,Wang, Xungai The Korean Fiber Society 2002 Fibers and polymers Vol.3 No.4

It is well known residual gum exists in degummed or rotted hemp fibers. Gum removal results in improvement in fiber fineness and the properties of the resultant hemp yams. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibers and the fiber fineness, described in terms of fiber width in this paper. This study examined the mean width and coefficient of variation (CV) of fiber width of seventeen chemically rotted hemp samples with reference to residual gum content. The mean and CV of fiber width were obtained from an Optical fiber diameter analyser (OFDA 100). The linear regression analysis results show that the mean fiber width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fiber width and the residual gum content. The strong linear co-relation between the mean of fiber width and the residual gum content is a significant outcome, since testing for fiber width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fiber cross-section hence the term \"fiber width\" is used instead of fiber diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at $1370cm^{-1}$, $1325cm^{-1}$, $1733cm^{-1}$, and $1600cm^{-1}$ attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.cter lost.

Frictional and Tensile Properties of Conducting Polymer Coated Wool and Alpaca Fibers

Wang Lijing,Lin Tong,Wang Xungai,Kaynak Akif The Korean Fiber Society 2005 Fibers and polymers Vol.6 No.3

Wool and alpaca fibers were coated with polypyrrole by vapor-phase polymerisation method. The changes in frictional and tensile properties of the single fibers upon coating with the conductive polymer are presented. Coating a thin layer of polypyrrole on the alpaca and wool fibers results in a significant reduction in the fiber coefficient of friction, as the conducting polymer layer smooths the protruding edges of the fiber scales. It also reduces the directional friction effect of the fibers. Depending on the type of fiber, the coating may slightly enhance the tensile properties of the coated fibers.

Nonlinear large deformation dynamic analysis of electroactive polymer actuators

Amir Ali Amiri Moghadam,Abbas Kouzani,Reza Zamani,Kevin Magniez,Akif Kaynak 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.6

Electroactive polymers have attracted considerable attention in recent years due to their sensing and actuating properties which make them a material of choice for a wide range of applications including sensors, biomimetic robots, and biomedical micro devices. This paper presents an effective modeling strategy for nonlinear large deformation (small strains and moderate rotations) dynamic analysis of polymer actuators. Considering that the complicated electro-chemo-mechanical dynamics of these actuators is a drawback for their application in functional devices, establishing a mathematical model which can effectively predict the actuator’s dynamic behavior can be of paramount importance. To effectively predict the actuator’s dynamic behavior, a comprehensive mathematical model is proposed correlating the input voltage and the output bending displacement of polymer actuators. The proposed model, which is based on the rigid finite element (RFE) method, consists of two parts, namely electrical and mechanical models. The former is comprised of a ladder network of discrete resistive-capacitive components similar to the network used to model transmission lines, while the latter describes the actuator as a system of rigid links connected by spring-damping elements (sdes). Both electrical and mechanical components are validated through experimental results.

Advanced Design, Fabrication, and Applications of 3D-Printable Piezoelectric Nanogenerators

M. A. Parvez Mahmud,Partho Adhikary,Ali Zolfagharian,Scott Adams,Akif Kaynak,Abbas Z. Kouzani 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.2

Piezoelectric nanogenerator (PENG) is a leading-edge mechanical energy harvesting device used in portable power supplyand self-powered sensor systems. Advanced 3D printers have been recently used to create 3D printed (3DP) PENGs. This hasfacilitated the rapid fabrication of PENGs and their integration into wearable electronics, biomedical systems, and internetof things devices. However, researchers face several critical challenges in developing robust 3DP-PENGs that can produceadequate electrical energy for self-powered systems. Therefore, this review on 3DP-PENGs is conducted to highlight theirrecent developments and challenges. This paper presents the latest 3D-printed piezoelectric nanogenerators in terms of theirmaterials selection and functionalization, design and architecture formation, and applications including pressure sensors,fl ow sensors, microphones, and implants. Finally, crucial challenges and optimization strategies that considerably impactthe output performance of 3DP-PENGs, along with a roadmap for their future enhancement are given. It is envisioned thatthis work will help reduce the gap between 3D printing and PENG technologies and accelerate the research and developmentof 3DP-PENGs.