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All Journal International Journal of Renewable Energy Development Transmisi: Jurnal Ilmiah Teknik Elektro Jurnal Sains Materi Indonesia Majalah Kulit, Karet, dan Plastik Jurnal Penelitian Karet Makara Journal of Technology
Rochmadi Rochmadi
Gadjah Mada University
Agriculture, Biological Sciences & Forestry Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Education Electrical & Electronics Engineering Energy Engineering Materials Science & Nanotechnology Mechanical Engineering

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STUDI KINETIKA SIKLISASI KARET ALAM DENGAN KATALISATOR ASAM SULFAT Prastanto, Henry; Rochmadi, Rochmadi; Hidayat, Muslikhin
Jurnal Penelitian Karet JPK : Volume 29, Nomor 1, Tahun 2011
Publisher : Pusat Penelitian Karet - PT. Riset Perkebunan Nusantara

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22302/ppk.jpk.v29i1.112

Abstract

Karet alam siklis (CNR) adalah resin pengeras dan pengkaku karet yang dapat dibuat dari lateks karet alam dengan katalis asam. CNR berpotensi menggantikan High Styrene Resin (HSR) yang merupakan produk turunan minyak bumi sehingga penggunaan CNR akan meningkatkan nilai tambah karet alam. Penelitian siklisasi lateks karet alam dengan katalis asam sulfat ini dilakukan untuk mengetahui kinetika reaksi siklisasi lateks karet alam dan nilai konstanta kecepatan reaksi siklisasi (k). Penelitian dilaksanakan di Laboratorium Teknologi Polimer, Jurusan Teknik Kimia Universitas Gadjah Mada. Lateks karet alam dicampur dengan surfaktan dan asam sulfat. Rasio massa asam sulfat terhadap massa lateks pekat karet alam (60%) adalah 1,1; 1,2; 1,3 dan 1,4, sedangkan suhu operasi yang digunakan adalah 85 dan 950C. Sampel diambil dengan interval waktu 15 menit dengan waktu reaksi sampai 2 jam. Selanjutnya sampel digumpalkan, dicuci, disaring dan dikeringkan. Sampel kemudian dianalisis konsentrasi ikatan rangkapnya yang ditunjukkan dengan bilangan iodnya. Analisis bilangan iodnya dilakukan dengan menggunakan metode larutan Wijs. Hasil penelitian ini menunjukkan, rasio massa asam sulfat terhadap lateks pekat agar dapat menghasilkan CNR adalah minimal 1,2:1. Konstanta kecepatan reaksi protonasi (k1) akan semakin besar dengan kenaikan rasio massa asam sulfat terhadap massa lateks. Nilai k2 dan k4 ternyata juga semakin besar dengan kenaikan rasio sehingga selain sebagai reaktan H+ juga berfungsi sebagai katalis.  How to Cite : Prastanto, H., Rochmadi, R., & Hidayat, M. (2011). Studi kinetika siklisasi karet alam dengan katalisator asam sulfat. Jurnal Penelitian Karet, 29(1), 63-75. Retrieved from http://ejournal.puslitkaret.co.id/index.php/jpk/article/view/112
Biokomposit dari serat rami dan sekresi kutu lak termodifikasi dengan lateks terhidrasi dan tidak terhidrasi Rohaeti, Eli; Mujiyono, Mujiyono; Rochmadi, Rochmadi
Majalah Kulit, Karet, dan Plastik Vol 31, No 1 (2015): Majalah Kulit, Karet, dan Plastik
Publisher : Center for Leather, Rubber, and Plastic Ministry of Industry, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (722.923 KB) | DOI: 10.20543/mkkp.v31i1.222

Abstract

Biocomposites are composite materials comprising one or more phases derived from a biological origin. Biocomposite with natural matrix developed more rapidly because they are more environmentally safer. The objective of research was to modify natural matrix from lac insect secretion with adding hydrated latex, to study effect of adding hydrated latex to the functional groups and the intrinsic viscosity of lac insect secretion, and to measure mechanical properties of biocomposite from modified lac insect secretion and ramie fiber. A sulfuric acid solution was used as catalyst in hydration of latex and then natural matrix of lac insect secretion was modified by adding hydrated latex. Biocomposite was prepared by mixing rami fiber and modified  lac insect secretion. It was then pressed with hydraulic press at 150 kgf/cm2 and 150oC for 15 minutes. Biocomposites were characterized using tensile tester according to ASTDM D 638-90 Type IV. The adding of catalyst caused the decreasing of intrinsic viscosity of latex. The adding of hydrated latex to natural matrix caused the increasing of intrinsic viscosity and functional group of matrix. The using 30% of catalyst and adding 10% of hydrated latex produced biocomposite with strength at break of 0.982 MPa, elongation at break of 1.189%, and Young modulus of 0.929 MPa.Keywords: biocomposite, hydration, latex, lac insect secretion, ramie fiber. ABSTRAK Biokomposit merupakan material komposit yang tersusun dari satu atau lebih komponennya berasal dari bahan alam. Biokomposit dari matriks alam berkembang lebih pesat karena lebih aman bagi lingkungan. Tujuan penelitian ini adalah untuk memodifikasi matriks dari sekresi kutu lak dengan penambahan lateks hasil hidrasi, mempelajari pengaruh penambahan lateks hasil hidrasi terhadap gugus fungsi dan viskositas intrinsik matriks, dan untuk mengukur sifat mekanik biokomposit dari matriks hasil modifikasi dengan serat rami. Lateks dihidrasi dengan variasi katalis asam sulfat 10, 20, dan 30% (m/m). Matriks alam dari sekresi kutu lak dimodifikasi dengan penambahan lateks hasil hidrasi sebanyak 5, 10, dan 15% (m/m). Biokomposit dibuat melalui pencampuran sekresi kutu lak hasil modifikasi dengan serat rami dan dipress pada tekanan 150 kgf/cm2 dan suhu 150oC selama 15 menit. Biokomposit dikarakterisasi menggunakan tensile tester sesuai dengan ASTDM D 638-90 tipe IV. Penambahan katalis menurunkan viskositas intrinsik lateks terhidrasi. Penambahan lateks terhidrasi meningkatkan viskositas intrinsik dan gugus fungsi matriks. Biokomposit dari matriks alam sekresi kutu lak termodifikasi lateks terhidrasi dengan penggunaan katalis 30% dan penambahan lateks terhidrasi sebesar 10% mempunyai kuat tarik sebesar 0,982 MPa, elongasi saat putus sebesar 1,189%, dan modulus Young sebesar 0,929 MPa.Kata kunci: biokomposit, hidrasi, lateks, sekresi kutu lak, serat rami.
Studi Pengukuran Partial Discharge Pada Bahan Resin Epoksi Syakur, Abdul; AP, Winarko; Berahim, Hamzah; Sarjiya, Sarjiya; Rochmadi, Rochmadi
Transmisi Vol 10, No 1 (2008): TRANSMISI
Publisher : Departemen Teknik Elektro, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (166.171 KB) | DOI: 10.12777/transmisi.10.1.49-52

Abstract

Polimer materials now have been broadly used for high voltage isolation device. After long operation the polimer isolation can have degradation or decreasing in isolation quality until it became improper isolation. One main caused about this degradation is the deformity for instance the pointed conductor between the conductor to isolation interface that could make the partial discharge. Therefore is so important to have the information about the partial discharge characteristics of  isolation material at operational condition. In this paper the research about the influences of voltage and application time of voltage to partial discharge characteristics was explained . This research used the epoxy resin for isolation and needle-plane electrode measurement method  with 50 Hz ac voltage to investigate the partial discharge parameters such as the number of positive and negative charge and the maximum charge of positive and negative.Keywords:  partial discharge,  resin epoksi,  elektroda jarum-bidang.
ANALISIS NUMERIK HOOKE JEEVES-RUNGE KUTTA UNTUK MENENTUKAN PERSAMAAN LAJU REAKSI POLIMERISASI PIROL Gunawan, Indra; Sulistyo, Hary; Rochmadi, Rochmadi
Jurnal Sains Materi Indonesia Vol 3, No 1: OKTOBER 2001
Publisher : Center for Science & Technology of Advanced Materials - National Nuclear Energy Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (603.731 KB) | DOI: 10.17146/jusami.2001.3.1.5249

Abstract

ANALISIS NUMERIK HOOKEJEEVES-RUNGEKUTTA UNTUK MENENTUKAN PERSAMAAN LAJU REAKSI POLIMERISASI PIROL. Telah dilakukan analisis numerik dengan menggunakan metode Hooke Jeeves yang dikombinasikan dengan metoda Runge Kutta, untuk menentukan model yang paling tepat dari persamaan laju reaksi polimerisasi pirol secara kimia. Polimerisasi kimia pirol dijalankan di dalam larutan FeCl3/pirol pada nisbah pereaksi 1,62 mol/mol dan 2,18 mol/mol dengan suhu reaksi 28℃, 40℃, 50℃, dan 60℃. FeCl3 berfungsi sebagai oksidator untuk membentuk kation pirol yang akan siap berpolimerisasi. Dilakukan analisis numerik dari dua model persamaan laju reaksi yang diturunkan dari persamaan-persamaan reaksi pemicuan, perambatan, dan penghentian. Dari analisis numerik di terhadap konsentrasi kation pirol.
Thermal Decomposition and Kinetic Studies of Pyrolysis of Spirulina Platensis Residue Jamilatun, Siti; Budhijanto, Budhijanto; Rochmadi, Rochmadi; Budiman, Arief
International Journal of Renewable Energy Development Vol 6, No 3 (2017): October 2017
Publisher : Center of Biomass & Renewable Energy, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ijred.6.3.193-201

Abstract

 Analysis of thermal decomposition and pyrolisis reaction kinetics of Spirulina platensis residue (SPR) was performed using Thermogravimetric Analyzer. Thermal decomposition was conducted with the heating rate of 10, 20, 30, 40 and 50oC/min from 30 to 1000oC. Thermogravimetric (TG), Differential Thermal Gravimetric (DTG), and Differential Thermal Analysis (DTA) curves were then obtained. Each of the curves was divided into 3 stages. In Stage I, water vapor was released in endothermic condition. Pyrolysis occurred in exothermic condition in Stage II, which was divided into two zones according to the weight loss rate, namely zone 1 and zone 2. It was found that gasification occurred in Stage III in endothermic condition. The heat requirement and heat release on thermal decomposition of SPR are described by DTA curve, where 3 peaks were obtained for heating rate 10, 20 and 30°C/min and 2 peaks for 40 and 50°C/min, all peaks present in Zone 2. As for the DTG curve, 2 peaks were obtained in Zone 1 for similar heating rates variation. On the other hand, thermal decomposition of proteins and carbohydrates is indicated by the presence of peaks on the DTG curve, where lignin decomposition do not occur due to the low lipid content of SPR (0.01wt%). The experiment results and calculations using one-step global model successfully showed that the activation energy (Ea) for the heating rate of 10, 20, 30, 40 and 50oC/min for zone 1 were 35.455, 41.102, 45.702, 47.892 and 47.562 KJ/mol, respectively, and for zone 2 were 0.0001428, 0.0001240, 0.0000179, 0.0000100 and 0.0000096 KJ/mol, respectively.Keywords: Spirulina platensis residue (SPR), Pyrolysis, Thermal decomposition, Peak, Activation energy.Article History: Received June 15th 2017; Received in revised form August 12th 2017; Accepted August 20th 2017; Available onlineHow to Cite This Article: Jamilatun, S., Budhijanto, Rochmadi, and Budiman, A. (2017) Thermal Decomposition and Kinetic Studies of Pyrolysis of Spirulina platensis Residue, International Journal of Renewable Energy Development 6(3), 193-201.https://doi.org/10.14710/ijred.6.3.193-201
Tin (II) Chloride Catalyzed Esterification of High FFA Jatropha Oil: Experimental and Kinetics Study Kusumaningtyas, Ratna Dewi; Handayani, Prima Astuti; Rochmadi, Rochmadi; Purwono, Suryo; Budiman, Arief
International Journal of Renewable Energy Development Vol 3, No 2 (2014): July 2014
Publisher : Center of Biomass & Renewable Energy, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ijred.3.2.75-81

Abstract

Biodiesel is one of the promising energy source alternatives to fossil fuel. To produce biodiesel in a more economical way, the employment of the low-cost feed stocks, such as non-edible oils with high free fatty acid (FFA), is necessary. Accordingly, the esterification reaction of FFA in vegetable oils plays an important role in the biodiesel production. In this work, esterification of FFA contained in Crude Jatropha Oil (CJO) in the presence of tin (II) chloride catalyst in a batch reactor has been carried out. The esterification reaction was conducted using methanol at the temperature of 40-60 °C for 4 hours. The effect of molar ratio of methanol to oil was studied in the range 15:1 to 120:1. The influence of catalyst loading was investigated in the range of 2.5 to 15% w/w oil. The optimum reaction conversion was obtained at 60 °C with the catalyst loading of 10% w/w oil and molar ratio of methanol to oil of 120:1. A pseudo-homogeneous reversible second order kinetic model for describing the esterification of FFA contained in CJO with methanol over tin (II) chloride catalyst was developed based on the experimental data. The kinetic model can fit the data very well.
Thermogravimetric Analysis and Kinetic Study on Catalytic Pyrolysis of Rice Husk Pellet using Its Ash as a Low-cost In-situ Catalyst Wibowo, Wusana Agung; Cahyono, Rochim Bakti; Rochmadi, Rochmadi; Budiman, Arief
International Journal of Renewable Energy Development Vol 11, No 1 (2022): February 2022
Publisher : Center of Biomass & Renewable Energy, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ijred.2022.41887

Abstract

The thermogravimetric behaviors and the kinetic parameters of uncatalyzed and catalyzed pyrolysis processes of a mixture of powdered raw rice husk (RRH) and its ash (RHA) in the form of pellets were determined by thermogravimetric analysis at three different heating rates, i.e., 5, 10, and 20 K/min, from 303 to 873 K. This research aimed to prove that the rice husk ash has a catalytic effect on rice husk pyrolysis. To investigate the catalytic effect of RHA, rice husk pellets (RHP) with the weight ratio of RRH:ARH of 10:2 were used as the sample. Model-free methods, namely Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO), were used to calculate the apparent energy of activation(EA). The thermogravimetric analysis showed that the decomposition of RHP in a nitrogen atmosphere could be divided into three stages: drying stage (303-443 K), the rapid decomposition stage (443-703 K), and the slow decomposition stage (703-873 K). The weight loss percentages of each stage for both uncatalyzed and catalyzed pyrolysis of RHP were 2.4-5.7%, 35.5-59.4%, and 2.9-12.2%, respectively. Using the FR, FWO, and KAS methods, the values of  for the degrees of conversion (a) of 0.1 to 0.65 were in the range of 168-256 kJ/mol for the uncatalyzed pyrolysis and 97-204 kJ/mol for the catalyzed one. We found that the catalyzed pyrolysis led the  to have values lower than those got by the uncatalyzed one. This phenomenon might prove that RHA has a catalytic effect on RHP pyrolysis by lowering the energy of activation.
The Effect of Rubber Mixing Process on The Curing Characteristics of Natural Rubber Hasan, Abu; Rochmadi, Rochmadi; Sulistyo, Hary; Honggokusumo, Suharto
Makara Journal of Technology Vol. 16, No. 2
Publisher : UI Scholars Hub

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

This research is aimed at studying the relationship between rubber mixing processes and curing characteristics of natural rubber. The curing characteristic analysis was carried out through a natural rubber formula having been masticated and mixed, followed by curing. As many as four mastication methods were finely applied; each respected four sequences of rubber mixing process. In the first method, rubber was masticated for 5 minutes and then rubber chemicals and carbon black N 330 were simultaneously added. In the second and the third methods, rubber was masticated for 1 minute and then carbon blacks and rubber chemicals were also simultaneously added but using different type of fillers. In the fourth method, rubber was masticated for 3 minutes and then rubber chemicals and carbon black were subsequently added. The additions of rubber chemicals and carbon blacks to the masticated rubber were distinguished by the sequence and time allocated for each mixing process. The carbon blacks were added in two stages by which 10 phr was added first and the remaining 40 phr was added later along with oil. In another method, ratios of the carbon blacks addition (as done in the first and the second stages) were 20:30, 30:20, and 40:10. The examination results showed that rubber mixing process gave an impact on the changes of curing characteristics. They were much affected by the method of carbon black addition. The mixing temperature also had an effect on both curing time and curing rate in which the higher the mixing temperature, the lower the curing time and curing rate. Vulcanization temperature also affected the curing time and curing rate in which the higher the vulcanization temperature, the lower the curing time and the higher the curing rate. Lastly, particle size of carbon black also gave an impact on the curing time and curing rate in which the smaller the particle size, the lower the curing time and the higher the curing rate.
Co-Authors Abdul Syakur Abu Hasan Arief Budiman Bambang Sutopo Budhijanto Budhijanto, Budhijanto Cahyono, Rochim Bakti Eli Rohaeti Hamzah Berahim Hary Sulistyo Henry Prastanto, Henry Indra Gunawan Muhammad Amiruddin Mujiyono Mujiyono Muslikhin Hidayat Prima Astuti Handayani Ratna Dewi Kusumaningtyas Sarjiya Siti Jamilatun Suharto Honggokusumo Suryo Purwono Winarko AP Wusana Agung Wibowo, Wusana Agung