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