The effect of octylated diphenylamine and Irganox 1520 antioxidants on the stability of polybutadiene rubber
One of the serious problems in polybutadiene rubber (PBR) production units is the color change in products, which is due to aging and the inability of antioxidants to protect the product, especially at high temperatures. In this study, the effects of amine-type antioxidant [octylated diphenylamine (OD)] and non-amine-type antioxidant (Irganox 1520) on the color yellowness, gel content and thermal stability of PBR, at concentrations of 500, 1000, 1500, 2500 and 4000 ppm, at temperature of 110 °C, and different aging times (1–10 h) were investigated. The results showed that the polymer with Irganox 1520 antioxidant has a higher thermal stability, less gel formation and lower color than polymer containing OD antioxidant; therefore, the Irganox 1520 antioxidant was more suitable.
KeywordsAntioxidant Color yellowness Gel content Irganox Octylated diphenylamine Polybutadiene rubber Stability
Nowadays, polybutadiene products are used in the manufacture of various catalysts. One of the catalytic systems used is cobalt acetate, which uses antioxidant for the stability of the polymer . The stabilizers of polymers should effectively protect polymers from various, mostly radical-degrading, processes, be compatible with the polymer, and persist in the polymer [2, 3, 4, 5]. Antioxidants in the polymerization reactions are compounds that are used to inhibit the reaction between polymers and free air oxygen. The oxidation process can be carried out at all stages of the existence of a polymer from the moment of manufacture up to the time of consumption and cause unwanted changes in the chemical, mechanical and electrical properties of the polymer [6, 7, 8]. If, for any reason, the antioxidant is not injected into the polymer, the product is dark brown after a short time and its physical and mechanical properties are practically altered. The reason for this is the destruction of the polymer by oxidation and the change of nature [9, 10]. Even a simple monophosphate antioxidant such as butylated hydroxytoluene (BHT) may also reduce the antioxidant activity and create a quinone system, which can act as a color agent in the polymer [11, 12, 13].
Octylated diphenylamine (C28H43N) is a medium activity, amine-type antioxidant for general-purpose elastomer use. It is antioxidant for natural rubber (NR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and chloroprene rubber (CR). It has good protective character to heat, oxygen, flexing and crazing, and is efficient to rubber whether used together with carbon black . It has obvious thermal brittleness resistance in CR, and can increase its protective character to ozone aging. It is also used as antioxidant and corrosion inhibitor in saline and synthetic lubricants, and as a general-purpose for non-blooming anti degrading in both black and non-black stocks, and in latex applications .
Irganox 1520 (C25H44OS2) is a multifunctional phenolic antioxidant for organic substrates such as elastomers, plastics, adhesives, sealants, oils and lubricants. It effectively protects the substrate against thermo-oxidation during processing and long-term heat aging. It is non-staining, non-discoloring, low in volatility, and stable to light and heat. Irganox 1520 is an effective stabilizer in a wide range of solution polymerized, emulsion polymerized and thermoplastic elastomers including butadiene rubber (BR), styrene–butadiene rubber (SBR), nitrile–butadiene rubber (NBR), isoprene rubber (IR), styrene–butadiene–styrene (SBS) and styrene–isoprene–styrene (SIS), as well as natural rubber [14, 15]. It can be used with other additives such as secondary antioxidants, benzofuranone, light stabilizers and other functional stabilizers, the recommended dosage level of which is 0.05–0.3% [16, 17].
In this work, considering that the technical knowledge of the use of antioxidants was related to the past two decades, attempts have been made to find antioxidants more favorable than the antioxidants used in the technologies available in the polybutadiene production industry.
Materials and methods
Preparation of the samples
Polybutadiene (Shazand Petrochemical Company, Iran) and toluene (99/8%, Sigma-Aldrich) as solvents, Irganox 1520 as a phenolic antioxidant (99%, Basel, Switzerland) and an octylated diphenylamine as an amine antioxidant (98%, Richem, Shanghai china) were used as main materials. First, 20 g of polybutadiene was dissolved in 300 cm3 of toluene and the appropriate amount of antioxidant was added to it, and then in the nitrogen gas atmosphere, the sample of the toluene solvent was dried. After drying, the sample was placed in an oven at 110 °C for aging times of 2, 4, 6, 8, and 10 h. The aging method was carried out in a manner similar to that described in ASTM D1693, ASTM D573 tests for plastic materials.
Differential scanning calorimetry thermal analysis is a method in which material changes at different temperatures are investigated over time. Differential scanning calorimetry was performed with a DSC (METTLER-TC11) at 30–300 °C (10 °C/min) and atmospheric pressure .
Results and discussion
Effect of antioxidants on color yellowness
Effect of antioxidants on gel content
Thermal analysis: differential scanning calorimetry
In this investigation, the performance of amine-type (OD) and non-amine-type (Irganox 1520) antioxidants in improving the stability of Polybutadiene was studied. Experiments were carried out at 110 °C, atmospheric pressure, aging time of 1–10 h, and 500–4000 ppm of antioxidant concentrations. The result of experiments demonstrated the superiority of Irganox 1520 relative to OD antioxidant.
By increasing the time at a specific concentration of both antioxidant types, the amount of coloration in the polymer matrix is increased, but by increasing the concentration of both antioxidants at a given time, the amount of color decreases. It can be said that at different times and concentrations, the color produced by the Irganox 1520 antioxidant is less than OD, which indicates better performance.
By increasing the time at a specific concentration of both antioxidants, the gel content increases in the polymer, while by increasing the concentration of both antioxidants at a given time, the amount of gel decreases. At all times and concentrations, the gel content in Irganox 1520 was always lower than OD, which indicates its advantage.
By increasing the concentration of both antioxidants, enthalpy destruction decreases, but in identical concentrations, the enthalpy of the Irganox 1520 is less than the OD, which indicates its better performance.
According to the experiments, the Irganox 1520 consumption range is 1500–2500 ppm. Using more amounts does not significantly affect the stability of the product and only increases the antioxidant use and, as a result, increases the cost.
- 2.Brandt HD, Nentwig W, Rooney N, LaFlair RT, Wolf UU, Duffy J, Puskas JE, Kaszas G, Drewitt M, Stephan G (2011) Rubber, 5. Solution rubbers. Ullmann’s encyclopedia of industrial chemistry. Wiley. https://doi.org/10.1002/14356007.o23_o02
- 3.Maiti M, Jasra R (2011) High-cis polybutadiene rubber in benign solvents and process for preparation thereof. Patent US20120296055 A1Google Scholar
- 7.Saunier J, Mazel V, Aymes-Chodur C, Yagoubi N (2012) Blooming of Irganox 3114® antioxidant onto a medical grade elastomer. Impact of the recrystallization conditions on the antioxidant polymorphism, on the film wettability and on the antioxidant leachability. Int J Pharm 437:89–99. https://doi.org/10.1016/j.ijpharm.2012.07.060 CrossRefPubMedGoogle Scholar
- 8.Mark HF (2004) Encyclopedia of polymer science and technology: acoustic properties to cyclopentadiene and dicyclopentadiene, vol 5. Wiley, pp 163–168. https://doi.org/10.1002/0471440264
- 17.Podesva J, Kovarova J, Hrdlickova M, Netopilik M (2009) Stabilization of polyurethanes based on liquid OH-telechelic polybutadienes: comparison of commercial and polymer-bound antioxidants. Polym Degrad Stab 94:647–650. https://doi.org/10.1016/j.polymdegradstab.2009.01.003 CrossRefGoogle Scholar
- 20.ISO 11357-3 (2011) Plastics–differential scanning calorimetry (DSC)–part 3: determination of temperature and enthalpy of melting and crystallization. International Organization for Standardization. http://www.iso.org
- 21.Cibulkova Z, Simona P, Lehocky P, Balko J (2005) Antioxidant activity of p-phenylenediamines studied by DSC. Polym Degrad Stab 87:479–486. https://doi.org/10.1016/j.polymdegradstab.2004.10.004 CrossRefGoogle Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.