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Hot vulcanising vs cold bonding for pulley lagging application – what are the differences?

Hot vulcanising vs cold bonding for pulley lagging application – what are the differences?

Introduction

Cold bonded lagging has been used for more than fifty years largely, as a result of its ease and convenience of application. While hot vulcanized rubber lagging has also been used for many years, hot vulcanized ceramic lagging and polyurethane lagging are more recent additions.

Lagging selection is one of the four pillars required for engineered lagging to perform.

This technical bulletin provides details on the differences between hot vulcanized lagging and cold bonded lagging, and how these differences impact the end use performance.

Cold bonded lagging as the name suggests is a lagging application system that is done at room temperature. Normally this means temperatures between +15°C and +40°C. When ambient temperatures fall outside this range the applicators would normally take steps to adjust the work area temperature to fall within this range.

The main advantage of cold bonded lagging is that it can be done both in the field (i.e. on the conveyor) or in a workshop and, requires no specialized equipment.

Hot vulcanized lagging application involves curing the lagging at elevated temperature, typically 140-160°C for 3-6 hours. This necessitate the use specialized equipment called an autoclave (PHOTO #1) and can only be done in factory setting. Hot vulcanized lagging cannot be done in the
field or with the pulley installed on the conveyor.

Hot Vulcanised Lagging
Photo #1

The main advantage of hot vulcanized lagging is that the process is much more robust than cold bonding, and as a result the adhesion of the lagging to the pulley is much stronger, consistently providing stronger rubber tear bonds.

The Differences Between Cold Bonded & Hot Vulcanised Lagging

The systems

The diagrams below show the cold bonded (Figure#1) and hot vulcanized (Figure#2) systems side by side. The hot vulcanized bonding system has additional uncured bonding layers that when activated by heat diffuse into and/or bond onto adjacent layers such as the steel pulley shell and the cured rubber backing of the lagging.
Cold Lagging Bonding System
FIGURE #1
Hot Vulcanised Lagging Bonding System
FIGURE #2

The application

The differences between cold bonding and hot vulcanization are summarized in the following images:
CURING TEMPERATURE
Cold Bonding                        Hot Vulcanised
CURING TIME
Cold Bonding                        Hot Vulcanised
CURING PRESSURE
Cold Bonding                        Hot Vulcanised
Cold Bonded Lagging Application to Pulley Shell