Group 14 butyl rubber
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Transcript of Group 14 butyl rubber
Butyl Rubber Butyl Rubber
GROUP 14
ONG HUI JIN 152161
SITI ZAHARAH BT SYED RAMLI 152197
NORASHEILA BT MOHD SAAD 152167
INTRODUCTION
•AKA isobutylene- isoprene rubber
• synthetic rubber/ elastomer
• a copolymer of isobutylene with isoprene
•isoprene units: double bond that provides a site for crosslinking during vulcanisation & located randomly in the polymer chain
•excellent impermeability& good flex properties -low levels of unsaturation between long polyisobutylene segments
Figure 1. Structure of butyl rubber.
Preparation/synthesis
Produced by cationic copolymerization between ≈ 98% isobutylene
&≈ 2% isoprene
Typical method:
Initiator: Friedel-Craft acids(e.gAlCl3)
Medium: methyl chloride (reaction diluent)& boiling liquid
ethylene
Why? To remove the heat of reaction and maintain the needed
temperature (Reaction is highly exothermic)
Temperature: controlled at low temperatures (-90 to -100 °C)
Why? To achieve high molecular weight butyl rubber for application
as rubber)
Initiator: mixture of a major amount of diethylaluminum chloride
& a minor amount of ethylaluminum dichloride( activated by minute
amounts of water / methylaluminoxane (MAO) )
-modified initiators :higher molecular weights, higher degrees of
conversion & higher isoprene contents in the butyl rubber
Medium: hexane
Temperature: -60 °C
- Activation by MAO allow higher polymerization temperature
which does not require much heat removal from reaction mixture
Alternative method:
Commercial Butyl Rubber polymerization process
PROPERTIES OF BUTYL RUBBER
Low permeability to air, gases and moisture
Vibration damping
converting the mechanical vibrational energy of solids into heat energy.
Low glass transition temperature
Low modulus elastomer
Elastomer: able to stretch a long distance and still bounce back
Low compression set
Compression set: percentage deflection from original shape of a rubber item
having been subjected to a constant compressive load, then released.
PROPERTIES OF BUTYL RUBBER cont.
Resistance to aging and to weathering from atmospheric exposure
Wide vulcanization versatility
Vulcanization: chemical process for converting rubber into a
compound material (polymer) with the addition of sulphur
Fast cure rates
Cure rates: toughening or hardening of a polymer material by cross-
linking of polymer chains
Processing safety: no nitrosamines or nitrosamines precursors
Nitrosamines: carcinogenic and can cause cancer
PROPERTIES OF BUTYL RUBBER cont.
High extensibility
Broad range of durometer and tensile strength properties
Low filler content for specific gravity, cost-effective compounding
Best sealant of all the known rubbers
Sealant rubber -type of product seals and protects different materials
using rubber-based substances
•Blood compatible
Allows this substance to be used in biomedical applications
USES OF BUTYL RUBBER
THE END