HSM Background

A 100% mechanical process without adding any chemical agent

The essence of this approach is the use of mechanical stresses to selectively break cross-linking bonds, thereby returning a previously cured visco-elastic material to a soluble state for recycling into existing or new formulations.

This means a simple process:

  • requiring no additional chemical additives for the breakdown (except the curing system adjustment)
  • requiring no elevated temperatures
  • that can be tuned to meet the requirements of specific formulations
  • for a wide range of cross-linking mechanisms.

Experimentation and development over the last ten years has shown that this process can be applied to a wide range of polymers at industrial scales.

HSM Origins

A New Technology With a Long History

In the 1950's, Dr William F. Watson and co-workers showed that under certain conditions uncured rubber could be softened purely by mastication.

Although this phenomenon had been observed by others, Dr Watson was able to develop a theoretical treatment of this effect, backed by experimental result. The theoretical treatment was based on mechanochemistry theory in which predictable changes to the chemical nature of a material can be achieved by applying mechanical forces.  

The principle of altering the molecular weight of a polymer through mastication is now an established technique in the rubber industry. It is reasoned that the the softening of rubber is the result of the rupturing of main-chain bonds caused by the extension of the central sections of the rubber chains.

During the last 20 years, Dr. Watson has extended this theory to cured networks, examining both sulphur and non sulphur cure systems.

As an example, for a sulphur bonded system examination of the bond strengths indicates that under certain conditions, the sulphur bonds are weaker than the carbon-carbon bonds. The bonds within the crosslink should therefore break before the carbon backbone. It can therefore be reasoned that if stress is correctly applied across the total network, then the crosslinks should break preferentially.

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