Introduction:
We have been using different materials in our daily life. One of them is the rubber. It has different structures and uses. It is used in varied ways. Do you know why the balloons become flat in a few days? Because they are made of polyisoprene, which cannot hold air or in other words, is not gas impermeable. But guess what will hold air? Synthetic rubber or Elastomer called Polyisobutylene (Shortly known as PIB). And it’s special because it’s the only rubber that’s gas permeable and can hold air for a long time. In today’s article, we will explore Polyisobutylene.
History of Polyisobutylene:
The 1940s were crucial years for the world. Some nations were fighting for Independence while some were fighting the World War. Polyisobutylene was developed during these years when the demand for natural rubber was not met due to internal wars between nations. Let’s indulge in these interesting events that took place in the development of Synthetic Elastomer. Malaysia, which was conquered by the Japanese Army, during World War 2, was the largest producer of natural rubber – Polyisoprene. Polyisoprene was the best elastomer and was easy to isolate from the sap of hevea trees (Hevea trees were found in abundance in Malaysia). Since the Japanese Invasion of Malaysia, the demand for natural rubber was not met and the need had arisen for an alternative. Some nations allied and made a useful discovery of PIB, also known as butyl rubber. It helped in successfully fulfilling the demand for rubber worldwide.
The Structure:
There are 3 main types of Polymers: Thermosets, Elastomers, and Thermoplastics. Polyisobutylene is a Vinyl Polymer. It’s very similar to Polyethylene and Polypropylene in structure. The difference is the substitution of every other carbon with two methyl groups. The interesting thing is most polymers with symmetrical backbones like isotactic polypropylene or polystyrene are Crystalline, but it’s not the case with PIB.
The Formation:
Another fact is that PIB was already developed by German scientists long before the war in 1931. A process in which when sulphur and lead were added to rubber and burnt, it formed bridges. This ties all the polymers in the rubber together and it is known as a crosslink. American Chemists came up with a way to Crosslink it. PIB is made from the monomer isobutylene, by Cationic Vinyl Polymerization. They copolymerize isobutylene with around 1 per cent isoprene. The polymerization is carried out at a freezing -100 degrees Celsius. This is because the reaction is so fast that we can’t control it. When isoprene is polymerized with isobutylene, only about 1 or 2 units out of every hundred repeat units is an isoprene unit. These have double bonds, meaning the polymer can be crosslinked by vulcanization just like natural rubber.
Uses of Polyisobutylene:
Natural Rubber surely made a comeback and now there are huge hevea tree farms enough to supply natural rubber for the entire world. But Synthetic Elastomers are produced approximately 20% more than natural rubber. The reason is the multi-purpose usage of gas – impermeable PIB.
It is being used globally to produce lubricants, sealants, fuel additives, chewing gum, and cling – film. It is FDA approved to be used in the production of Chewing gum and cling–film. It can also be used in some formulations as a thickening agent. Apart from Lubricant and fuel additive, it’s also used in manufacturing explosives as a biding agent. It is used as a primary seal in insulating Glass windows, damp proofing and repairing roofs, also commonly used for manufacturing rubber stoppers for sealing medicines, and even for speakers and other audio equipment including surround sound systems. It’s also one of the most powerful elastomers when it comes to gas masks and decontamination. It is a harder and less porous material than other elastomers.
Properties of Polyisobutylene:
Following are the properties of PIB:
- It has Moisture permeability
- It is Non – toxic
- It’s Colourless
- It’s Odourless
- High thickening ability
- Good sheer stability
- Clean burning
- Adhesive Properties
Where is it applicable?
Some of the processes where it is applicable: Pressure sensitive adhesives and hot melt adhesives, Electrical insulation materials like cables, condensers, asphalt modifiers, chewing gum, personal care, resin plasticizer, stretch films, wrap films, lubricants and greases like in automotive and industrial gear oils, metal working fluids, as an intermediate for lubricants and fuels dispersant additives, explosive emulsifier to name a few.
Takeaways:
In this article, we learnt about what is Polyisobutylene. How is it formed and structured? It has an interesting history and has been a part of some important events in our history. We also understood its properties in a very simple language hopefully. We also learned where can we recognise this Elastomer from in our day-to-day life, as it is being used in chewing gums, window repairs, and sound systems, seal stoppers on medicines and even for gas masks.
We hope that viewers have received an exploration regarding the usage of Polyisobutylene. Kindly drop your valuable feedback in a suggestion box. We would like to have your feedback and responses. Keep on reading and stay tuned with us.