Sains Malaysiana 53(9)(2024): 3135-3147

http://doi.org/10.17576/jsm-2024-5309-18

Diimide-Mediated Hydrogenation of Nitrile Butadiene Rubber

(Penghidrogenan Pengantaraan Diimida bagi Getah Nitril Butadiena)

AMIRA SHAFIQA SALLEH HUDDIN¹, YI-FAN GOH², NAHARULLAH JAMALUDDIN³ & SITI FAIRUS MOHD YUSOFF^1,4,*

¹Department of Chemical Sciences, Faculty of Science andTechnology, Universiti Kebangsaan Malaysia, 43600UKM Bangi, Selangor, Malaysia

²Asia Innovation Centre (AIC), Synthomer Sdn Bhd, Kawasan Perindustrian i-Park, Bandar Indahpura, 81000 Kulai, Johor, Malaysia

³Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia

⁴Polymer Research Centre (PORCE), Faculty of Science andTechnology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

Diserahkan: 19 Januari 2024/Diterima: 19 Julai 2024

Abstract

The hydrogenation of nitrile butadiene rubber (NBR) has shown great potential for improving its physical, thermal, mechanical, and chemical stability. Hydrogenation process of NBR in this work involved the utilization of diimide produced from the interaction between hydrazine hydrate (N₂H₄) and hydrogen peroxide (H₂O₂), with the addition of boric acid as a promoter. Attenuated total reflectance Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were used to evaluate the degree of hydrogenation, glass transition, thermal stability, and rubber crystallinity, respectively. The highest hydrogenation degree was 99%, which resulted in a 57% gel content. Upon hydrogenation, both the glass transition temperature (T_g) and decomposition temperature (T_d) increased. The hydrogenated rubber samples generally showed an amorphous state, except for the 99% hydrogenated sample, which displayed a semi-crystalline state. However, using diimide for direct hydrogenation yields a side reaction from the free radicals in the system, which leads to gel formation. Optimization was accomplished by employing the response surface methodology (RSM), which entailed manipulating parameters such as the total solid content (TSC) of NBR, reaction time, and the mole ratio of H₂O₂ to N₂H₄, to reduce the percentage of gel content. The RSM analysis identified the optimum reaction conditions as a 1:1 mole ratio of H₂O₂: N₂H₄ and 25% TSC, with a reaction time of 8 h, which yielded 32% gel content percentage, where a mole ratio of H₂O₂ to N₂H₄ and reaction time indicated a synergistic effect, whereas TSC denoted an antagonistic effect.

Keywords: Diimide; gel content; hydrogenation; nitrile butadiene rubber; response surface methodology

Abstrak

Penghidrogenan getah nitril butadiena (NBR) telah menunjukkan potensi besar untuk meningkatkan kestabilan fizikal, haba, mekanik dan kimianya. Proses penghidrogenan NBR dalam kajian ini melibatkan penggunaan diimida yang dihasilkan daripada interaksi antara hidrazin hidrat (N₂H₄) dan hidrogen peroksida (H₂O₂), dengan penambahan asid borik sebagai promoter. Spektroskopi jumlah pantulan dilemahkan- inframerah transformasi Fourier (ATR-FTIR), kalorimetri imbasan pembezaan (DSC), analisis termogravimetrik (TGA) dan pembelauan sinar-X (XRD), digunakan untuk menilai darjah penghidrogenan, peralihan kaca, kestabilan terma dan sifat kehabluran getah. Darjah penghidrogenan tertinggi yang dicapai ialah 99%, menghasilkan kandungan gel sebanyak 57%. Selepas penghidrogenan, kedua-dua suhu peralihan kaca (T_g) dan suhu penguraian (T_d) meningkat. Sampel getah terhidrogenasi menunjukkan keadaan amorfus, manakala sampel getah dengan 99% peratusan penghidrogenan, memaparkan keadaan separa kristal. Walau bagaimanapun, diimida menghasilkan tindak balas sampingan daripada radikal bebas dalam sistem, yang membawa kepada pembentukan gel. Pengoptimuman dicapai dengan menggunakan kaedah rangsangan permukaan (RSM), dengan menggunakan parameter yang dimanipulasi, iaitu jumlah kandungan pepejal (TSC) NBR, masa tindak balas dan nisbah mol H₂O₂ kepada N₂H₄, untuk mengurangkan peratusan kandungan gel. Analisis RSM mengenal pasti keadaan tindak balas optimum sebagai nisbah mol 1:1 H₂O₂:N₂H₄ dan 25% TSC, dengan masa tindak balas selama 8 jam yang menghasilkan 32% kandungan gel dengan nisbah molar H₂O₂ kepada N₂H₄ menunjukkan kesan sinergistik, sementara TSC dan masa tindak balas menunjukkan kesan antagonis.

Kata kunci: Diimida; getah nitril butadiena; kandungan gel; kaedah rangsangan permukaan; penghidrogenan

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*Pengarang untuk surat-menyurat; email: sitifairus@ukm.edu.my