Zulkifli Ahmad

The most researched elastomer in recent years is polydimethylsiloxane (PDMS), which has several uses in various engineering industries. One of the PDMS’s key characteristics is its hyper-elasticity nature, which enables the production of sensors, flexible electrical circuits, transducers, and antennas. This study used the hyper-elastic constitutive models to predict the mechanical behavior of incompressible, isotropic, and hyper-elastic material PDMS under uniaxial tension. These models are curve-fitting tools that consist of strain energy density and stress functions. To pursue the analysis, a new formulation of PDMS substrate was proposed, and a tensile test was performed to evaluate its stress-strain behavior. The experimental data was implemented on various hyper-elastic models using Abaqus, like Mooney-Rivlin, Yeoh, Ogden, and reduced polynomial models. The goodness of fit of every model was evaluated by calculating R2 values. Consequently, among these models, the reduced polynomial model with 6 material constants possessed the highest R2 value (0.9936) and was considered the best-fit model among the other models. Furthermore, the material constants of this model were applied to the 3D dumbbell-shaped model of PDMS in Abaqus for its validation. The boundary conditions were applied on the model similar to the experimental setup, as 33 mm displacement on one end and the other was fixed with all DOF. For mesh quality and mesh sensitivity of the material, various mesh sizes with the linear formulation (C3D8RH) were utilized, and the best mesh size was selected to evaluate very close results with the experimental.

Teaching materials are one of the elements that support the teaching and learning process. Science learning is the most enjoyable learning so that in the process of learning biology on the material concept of the general characteristics of plants, especially in the sub-subject matter of ferns, it can be done with learning media assisted by corporate pdf. This study aims to (a) determine the validity of the use of PDF corporate learning media on the concept of material General characteristics of plants in class X students at SMA Negeri 5 Kota Ternate, (b) To find out the learning outcomes of SMA Negeri 5 Kota Ternate on the material characteristics concept -general characteristics of plants using coprate PDF media. Learning media validation was assessed by 4 validators to obtain media and material validation data, while learning outcomes data were analyzed using Excell 2010. The results of this study show that the media validation results obtained a score of 89% with valid criteria, while the material validation results obtained a score of 91.3%. with very valid criteria. The learning outcomes of class X IPA 4 at SMA Negeri 5 Kota Ternate experienced an increase in learning outcomes after the teaching and learning process used PDF Corporate assisted learning media.

Optical properties of two‐fluorinated polysiloxane‐co‐polyimide (PI‐PDMS and 3‐(aminopropyl)triethoxysilane [PI‐APTES]) were investigated based on their molecular structure and compared with the pure PI at 1,550 nm radiation. The refractive indexes and birefringence of the copolymers were reduced which is attributable to the chain flexibility as substantiated from the differential scanning calorimetry result. They are highly transparent at near infrared (NIR) region with light transmittance above 90% at visible region while displaying excellent thermal stability up to 456°C. Asymmetry planar waveguides was fabricated which recorded a respectable low optical loss 0.020 dB/cm for pure PI, 0.042 dB/cm for PI‐PDMS, and 0.066 dB/cm for PI‐APTES, respectively. Despite proving low NIR absorption and low birefringence, extrinsic factor namely surface roughness was accounted as affecting the higher optical loss in polyimide siloxane copolymer compared to pure PI. The excellent thermal and optical properties displayed by these series of material established their viable application as waveguide material at 1,550 nm wavelength.

Optical properties of fluorinated polysiloxane-co-polyimide (PI-ATPDMS) were investigated based on the molecular structure and compared with the pure polyimide (PI) at 1550 nm radiation. The refractive index of the copolymers was slightly reduced by 3.5% whilst the birefringence was reduced by 0.37% respectively compared to PI. They are highly transparent at near infrared (IR)...

The rapid progress in electronic applications for movable devices requires the conductive matrix to be not only flexible but also stretchable. A simple microstrip patch antenna was fabricated based on silver ink polysiloxane composite with a stretchable polysiloxane substrate at a resonance frequency of 2.50 GHz. It is designed at a postpercolation threshold of 35, 45, and 60 vol % conductive filler loading so as to allow a consistent conductivity at an ample range of cyclic stretching. With the presence of coupling agent and additives, the patch antenna displayed an extremely good adhesion between the ink and the substrate, which prevents any local rupture during stretching. Variable range hopping model verified that conductivity occurs through hopping and tunneling mechanisms, giving transient optimum conductivity in the range of 10–70 S/cm at 10–20% strain amplitude range. The fabricated prototype of microstrip patch antenna displayed a decreasing resonant frequency with strain. Of note, the radiation loss S₁₁ and the bandwidth values are proportionally related to the conductivities during stretching. These results verified the proposed mechanisms of construction and destruction of conductivity occurring during the percolation threshold process. The fabricated antenna proved the feasibility for use as a stretchable device at an ultrahigh-frequency band.

This work aims to synthesize new series of polysiloxane copolymer through hydrosilylation reaction based on different level of crosslink densities and phenyl content. The results revealed that polysiloxanes resins with phenyl rings increased viscosity up to 3800 cps while displaying a relatively high refractive index of 1.531. The asymmetric phenyl substitution onto chain backbone led to formation of densely packed structure resulting in reduced water absorption and gas permeability of PDMS resins. High level of crosslinking contributed to a high shore A hardness and adhesion strength. It displayed transparency of 97% whose percentage reduction was 1.6% under thermal and 0.6% UV aging. No obvious discoloration was observed during accelerated thermal aging up to 210 min at 80 °C. These results are key attributes that make the synthesized polysiloxane series as ideal candidate for high brightness LED encapsulant. © 2019 Wiley Periodicals, Inc. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47895.

Qualitative polymer gels exhibiting considerable viscoelastic properties are of immense significance in the petroleum industry as they curtail excessive water production during the tertiary stage of crude oil production. The incorporation of suitable organic or inorganic solid substances into the polymer gel system strengthens its viscoelastic properties. This research work presents hybrid gravitational search algorithm (GSA) and support vector regression (SVR) as novel modelling tools for viscoelastic properties estimation of polymer gel synthesized from polyacrylamide (PAM)/polyethyleneimine (PEI). The coal fly ash (CFA) was incorporated in PAM/PEI gel in order to enhance its viscoelastic characteristics. The hybrid GSA‐SVR models were developed using real‐life experimental data. The results of the models validated using unseen data show a high degree of correlation coefficients (87.3 % for elastic modulus and 97.2 % for viscous modulus), with experimental data generating a small root mean square error (coefficients 669.5Pa for elastic modulus and 38.5Pa for viscous modulus). The developed hybrid models were further used to scrutinize the effect of the addition of various amounts of CFA on the PAM/PEI viscoelastic properties and observed behaviours were presented and discussed. The predictive capability of the developed hybrid model coupled with its strength in modelling the impact of CFA in the PAM/PEI gel are highly meritorious and the outcomes from this investigation would be relevant during the design and formulation of polymer gels employed for water shutoff treatment during hydrocarbon recovery.

Next generation electronics should be implementation on heterogeneous integration between sensor device with micro controller unit (MCU). Towards to robustness and high sensing performance, hybrid flexible printed electronic (HFPE) technology becoming an alternative for sensor fabrication compared to conventional silicon semiconductor processing photolithography technique. Thus in this paper, formulation on stretchable conductive ink (SCI) by implementing polydimethylsiloxane (PDMS) as a binder mixed with silver (Ag) flake was characterized. Resistance average between 0.6 – 98.9 with strecthability from 0% to 90%. Fabricated strechtable based temperature sensor showed the resistivity of circuit trace was average 0.7–1.6 Ohm.μm. This paper showed the capability implementation SCI as a circuit trace and heteregenously integration with multiple rigid components such as micro controller unit IC, LED IC, temperature sensor and cable connector as a simple temperature circuit system on TPU substrate.