Chemical properties of Indopol® polybutenes
Polybutene Structure
- Indopol polybutenes are synthetic hydrocarbon polymers made via acid catalysed cationic polymerization of an isobutene-rich C4 stream. They approximate to pure polyisobutene (PIB), but also have some n-butene incorporated. Each molecule possesses an olefinic double bond at or near one end. A generic structure for polybutene is shown below.
- The number average degree of polymerization (DPn) for Indopol polybutenes ranges from about 3 up to 110, depending upon grade.
Reactivity
- The presence of olefinic double bonds makes polybutenes amenable to the same reactions as low molecular weight substituted mono-olefins. Such reactions can be used to impart the properties of polybutenes (e.g. oil solubility, hydrophobicity, viscosity) to the derivative. For instance, the reaction of polybutene with maleic anhydride yields polyisobutenyl succinic anhydride (PIBSA), which is used to make engine oil dispersants and anti-rust additives.
- Other reactions which have been successfully performed on polybutene include: epoxidation, oxidation, halogenation, hydrohalogenation, sulphonation, reductive amination, haloboration/oxidation and nitration. Polybutenes can also be used as alkylating agents in electrophilic substitutions of isoalkanes and aromatics.
Oxidative Stability
- Indopol polybutenes are chemically stable and typically are not prone to atmospheric oxidation under ambient conditions. Their chemical stability is demonstrated by their retention of viscosity and tackiness, and their failure to harden or to show any deterioration of color on prolonged ageing at ambient temperatures. Indopol polybutenes contain no anti-oxidant, but these can be added by the customer if color and odor requirements are stringent. For further comments on color, see the above section on physical properties.
Metal Impurities and Corrosion
- Indopol polybutenes are essentially free from metal impurities, do not corrode metals and can be stored in carbon/mild steel tanks or drums. ICP analyses have typically shown sodium, potassium, iron, copper and aluminum levels below 1ppm.
Solubility in Organic Solvents
- In general, Indopol polybutenes are soluble in non-polar solvents and insoluble in polar solvents. However, polymer molecular weight can influence solubility. For example, a light grade such as Indopol L-8 is soluble in some ester and ketone solvents, which will not dissolve heavier grades such as Indopol H-300. Note that the solvency of poor or marginal solvents can often be increased by blending with non-polar co-solvents.
Compatibility with Resins, Polymers, etc.
- Indopol polybutenes are generally most compatible with non-polar materials. Compatibility between polybutene and other materials decreases as: 1) the polarity of the other material increases, and 2) the molecular weight difference between polybutene and the other material increases. Nevertheless, incompatibility between polybutene and polar materials can often be overcome by the use of a third compatibilizing component in a mixture, or by the addition of inorganic fillers.