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All Journal TEKNIK CHEMICA Jurnal Teknik Kimia Communications in Science and Technology Indonesian Journal of Chemical Analysis (IJCA) Jurnal Ilmu Fisika
Mujtahid Kaavessina, Mujtahid
Program Studi Teknik Kimia, FT, UNS Jl. Ir. Sutami no. 36 A, Surakarta 27126 Telp/fax:0271-632112
Astronomy Chemical Engineering, Chemistry & Bioengineering Chemistry Earth & Planetary Sciences Energy Engineering Environmental Science Materials Science & Nanotechnology Physics

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Formation of fine particles using supercritical fluid (SCF) process: Short review Chafidz, Achmad; Jauhary, Thonthowy; Kaavessina, Mujtahid; Sumarno, Sumarno; Latief, Fahamsyah H.
Communications in Science and Technology Vol 3 No 2 (2018)
Publisher : Komunitas Ilmuwan dan Profesional Muslim Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (760.44 KB) | DOI: 10.21924/cst.3.2.2018.101

Abstract

This paper will discuss about the utilization of supercritical fluid (SCF) process to produce fine particles. Supercritical fluids (SCFs) process can be considered as an emerging “clean” technology for the production of small-size or fine particles (e.g. micron-size). Microsphere is a material in micron scale which has been widely used as adsorbent, catalyst support, and drug delivery system. For advanced application, those materials are formulated in the form of porous microspheres. There are several methods that can be used using SCFs. Those method are, Rapid Expansion of Supercritical Solution (RESS), Gas Anti-Solvent/Supercritical Anti-Solvent (GAS/ SAS), Aerosol Solvent Extraction System (ASES), dan Solution Enhanced Dispersion by Supercritical Fluids (SEDS) and Particle from Gas-Saturated Solutions/Suspensions (PGSS). Considering the morphology of material which will be used to prepare microsphere, each of methods above has specific advantages and disadvantages toward the material. Based on the literatures, the ASES method is more likely to produce porous microparticles (microspheres). In the ASES method, porous microsphere formation is the result of interactions between: degrees of supersaturation, nucleation velocity and crystal growth.
Evaluation of the Chemical Structure and Thermal Properties of Polyethylene Glycol (PEG)-Doped Polylactic Acid (PLA)/Multiwalled Carbon Nanotube (MWCNT) Composites Rifa'i, Awaludin Fitroh; Kaavessina, Mujtahid; Distantina, Sperisa
Indonesian Journal of Chemical Analysis (IJCA) Vol. 7 No. 2 (2024): Indonesian Journal of Chemical Analysis
Publisher : Universitas Islam Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20885/ijca.vol7.iss2.art5

Abstract

This study aimed to investigate the chemical structure, thermal properties, and stability of polylactic acid (PLA) composites blended with multi-walled carbon nanotubes (MWCNTs) and polyethylene glycol (PEG). The composites were fabricated using a masterbatch blending method with two different molecular weights (Mw) of PEG. The masterbatch was initially prepared using solvent casting with chloroform as the solvent, followed by melt blending using an extruder. ATR-FTIR spectroscopy identified strong hydrogen bonds between the C=O groups of PLA and the –OH groups of PEG, as evidenced by the peak at 1748 cm¹. Differential Scanning Calorimetry (DSC) revealed that incorporating 14 wt% of PEG 10,000 into PLA/MWCNT composite significantly enhances the melting enthalpy (∆Hm) from 18.3 J/g to 24.6 J/g and the degree of crystallinity from 2% to 17.3%. The glass transition temperature (Tg) decreased with the addition of PEG, indicating increased chain mobility, while the melting temperature (Tm) remained relatively constant around 158 oC regardless of the PEG Mw. Despite the plasticizing effect of PEG, the thermal stability of the composites was maintained across different PEG Mw. Scanning Electron Microscope (SEM) images showed that MWCNTs were well dispersed within the blend, facilitated by ultrasonic stirring during preparation.
Improving Solvolysis Rate Via Under Glass-Transition Temperatures Quenching Followed by Roll Bending of Carbon Fiber Reinforced Polymer Composite Sukanto, Heru; Kusharjanta, Bambang; Kaavessina, Mujtahid
TEKNIK Vol 45, No 3 (2024): December 2024
Publisher : Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/teknik.v45i3.59296

Abstract

Reusing carbon fiber once it has been used as reinforcement in composite structures involves a complex recycling technique. This recycling process requires a strategy to ensure the recycled carbon fiber meets technical standards. Among various recycling processes, the solvolysis technique yields carbon fiber with high purity. However, solvolysis is also the most time-consuming method. This study proposes using quenching and roll-bending pretreatments, which increase the contact surface area between the composite and the solvent solution for expediting the solvolysis process of carbon fiber reinforced polymer (CFRP) composite. Quenching was performed by heating the composite to 75°C, 100°C, and 125°C before immersing it in water at room temperature. Roll bending was designed based on the principle of three-point bending and aimed to induce a strain in the composite that exceeds the strain of the epoxy resin. Quenching at 75°C, followed by roll bending, resulted in a 21% increase in the surface area of the composite. This increased area improved the solvolysis efficiency of CFRP composites by up to 21% after four days of immersion in a mixture of acetone and acetic acid.
Effect of Freshwater and Seawater Immersion on Mechanical Properties and Pre-Immersion Magnetic Response of Silicone Rubber–Magnetite Composite Magnets Wibowo, Wibowo; Santoso, Nehemia Herbert; Ramadhan, Brilliano Wahyu; Juwana, Wibawa Endra; Kaavessina, Mujtahid
Jurnal Ilmu Fisika Vol 18 No 1 (2026): March 2026 (Forthcoming Issue)
Publisher : Jurusan Fisika FMIPA Universitas Andalas

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25077/jif.18.1.25-34.2026

Abstract

Magnetite (Fe₃O₄) and RTV 48 silicone rubber-based magnetic composites have potential for outdoor applications due to their flexible and tunable magnetic properties. This study investigates the effect of immersion for 14 days in fresh water and seawater on its mechanical, magnetic, and thermal properties. Specimens were made by mixing 70 wt% Fe₃O₄ powder into RTV 48 matrix, then tested for hardness using Shore A durometer, magnetic properties using Vibrating Sample Magnetometer (VSM), and thermal stability using Thermogravimetric Analysis (TGA). Results showed a decrease in surface hardness due to matrix degradation by water penetration. The magnetic properties continued to exhibit soft magnetic characteristics with low coercivity and remanence. TGA analysis revealed changes in thermal degradation patterns, signaling chemical interactions between the material and the wet environment. These findings suggest that exposure to water can affect the long-term performance of Fe₃O₄-RTV 48 composites, making moisture resistance an important aspect for their outdoor applications.
Effect of Acrylamide and Potassium Persulfate on The Characteristics of Water Hyacinth-Carrageenan Bead Gel Using Microwave Grafting Method Distantina, Sperisa; Putra, Novan Aldian Rahmadan; Naryani, Rahma Fitri; Kaavessina, Mujtahid
CHEMICA: Jurnal Teknik Kimia Vol. 10 No. 3 (2023): December 2023 [Available online since December 26, 2023]
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26555/chemica.v10i3.27389

Abstract

The cellulose of water hyacinth (Eichhornia crassipes) was utilized as raw material in bead gel production. In this research, hydrogel was prepared by grafting of acrylamide (AA) monomers onto the water hyacinth cellulose as the backbone using the microwave to produce hydrogel. This research aimed to determine the influence of adding AA and potassium persulfate (PPS) as an initiator on characteristic of swelling capacity in water. The cellulose powder obtained from the stem of water hyacinth was immersed in NaOH solution (1.5 N) for the delignification process for 10 min. The resulted cellulose was mixed with water and varying additions of 4, 7, dan 10 g acrylamide (AA) and 0.05, 0.10, and 0.15 g PPS to undergo grafting reaction.  The obtained gel was washed and soaked in the acetone to remove the unreacted AA and PPS. The resulting precipitated solid was dried and called Water Hyacinth  Cellulose Grafted Polyacrylamide (WH cellulose-g-PAA). The mixture of carrageenan with WH cellulose-g-PAA underwent crosslinking using aqueous KCl and CaCl2 after passing through palm oil layer to form bead gel. The properties of the dried bead gel were tested for functional groups using FTIR and for swelling capacity in water. Based on the FTIR test results, it can be concluded that AA monomers were successfully grafted onto the water hyacinth cellulose backbone. The addition of AA that is too low or too high will reduce the swelling capacity, as well as PPS.
Co-Authors Bambang Kusharjanta Chafidz, Achmad Heru Sukanto Jauhary, Thonthowy Latief, Fahamsyah H. Naryani, Rahma Fitri Putra, Novan Aldian Rahmadan Ramadhan, Brilliano Wahyu Rifa'i, Awaludin Fitroh Santoso, Nehemia Herbert Sperisa Distantina Sumarno . Wibawa Endra Juwana, Wibawa Endra Wibowo Wibowo