Model kinetika reaksi polimerisasi toluen diisosianat (TDI) - Dietilen glikol (DEG)

SETYOWATI, Penny, Ir. Rochmadi, SU.,PhD

2002 | Tesis | S2 Teknik Kimia

Reaksi polimerisasi antara TDI - DEG merupakan reaksi polimerisasi adisi yang membentuk poliuretan rantai linier dan apabila TDI berlebihan akan tejadi reaksi sekunder membentuk struktur rantai cabang. Penelitian ini ddakukan untuk mempelajari kinetika reaksi polimerisasi TDI - DEG melalui pengembangan model sistem nonideal dengan menggunakan konsep aktivitas. Koefisien aktivitas dapat diperkirakan dengan cara UNIFAC. Polimerisasi TDI - DEG dilakukan didalam reaktor batch berupa labu leher tiga yang dilengkapi dengan pengaduk, termometer, alat pengambil sampel, pendingin tegak, water bath dan regulator. Larutan DEG dimasukkan ke dalam reaktor, suhu diatur pada suhu yang ditentukan, kemudian larutan TDI ditambahkan sambil diaduk. Suhu dijaga konstan dengan mengatur suhu water bath. Sampel diambil pada menit ke 10 sampai menit ke 60 (sebelum terjadi gelpoint) dengan selang waktu 10 menit dan dianalisa kandungan gugus NCO. Peubah - peubah yang dipelajari meliputi variasi suhu dari 30°C - 50°C dengan interval 5°C pada perbandingan mol NCO/OH 1,5 serta variasi perbandingan mol NCO/OH dari 1,O - 3,O dengan interval 0,5 pada suhu tetap 30°C. Berdasarkan dari hasil penelitian yang diperoleh, disimpulkan bahwa kinetika reaksi polimerisasi TDI - DEG dapat dijelaskan dengan baik oleh model I maupun model II. Konstante kecepatan reaksi k₁ (linier) lebih besar dari k₂ (cabang) dan merupakan fungsi suhu menurut persamaan Arrhenius sebagai berikut : a. model I (ideal) k₁ = 85,3576 e^-4051/RT (L/mol.menit), ralat rata-rata = 0,79% k₂ = 6,20758 e^-3779,144/RT (L/mol.menit), ralat rata-rata = 0,93% b. model II (nonideal) k₁ = 802,5733 e^{-1594,8737/RT} (L/mol.menit), ralat rata-rata = 0,55% k₂ = 7,6001 e^-9630,45/RT (L/mol.menit), ralat rata-rata = 1,38% dengan T dalam K, berlaku untuk kisaran suhu 30°C (303K) - 50°C (323K). Model II dapat digunakan untuk memprediksi distribusi berat molekul larutan polimer yang terbentuk.

The addition polymerization of toluene diisocyanate (TDI) with diethylene glycol (DEG) forms a linear polyurethane and with an excess of isocyanate, branching on the linier polymer occurs as a result of secondary reaction. The aim of this research was to study polymerization reaction of TDI - DEG by developing the model of nonideal system using activity concept, with the activity coefficient predicted using UNIFAC method. TDI - DEG polymerization was carried out in a three necked flask as batch reactor equipped with a stirrer, thermometer, samples device, freezer, water bath and voltage regulator. The DEG solution was put in to the reactor and heated to the desired temperature. After the desired temperature had reached, TDI solution was added and stirred rigorously. During the process, the temperature was kept constant using a water bath. Samples were taken from the flask at particular time (before the gel point reached) to determine the NCO concentrations. Experiments were carried out at the temperature of 30, 35,40,45 and 50°C with a constant NCO to OH ratio of 1.5 and at the NCO to OH ratio of 1.0, 1.5, 2.0, 2.5 and 3.0 with a constant temperature of 30°C. It can be concluded that both model I and model I1 predict well the polymerization of TDI - DEG. The rate constant of linear reaction kl were higher than the branch reaction k2, both in the first model (ideal system) and the second model (nonideal system). The relation between rate constant and temperature are as follows : a. First model (ideal s stem approach) k₁ = 85,3576 e^-4051/RT (L/mol.s), average error = 0.79% k₂ = 6,20758 e^-3779,144/RT (L/mol.s), average error = 0.93% b. Second model (nonideal system approach) k₁ = 802,5733 e^{-1594,8737/RT} (L/mol.s), average error = 0.55% k₂ = 7,6001 e^-9630,45/RT (L/mol.s), average error = 1.38% with T in K, for temperature range from 30°C (303K) to 50°C (323K). The second model can be used to predict a molecular weight distribution of polymer solution.

Kata Kunci : poliuretan, polimer, toluen diisosianat, model kinetik, nonideal, polyurethane, polymer, toluene diisocyanate, kinetic model