Rubber Extrusion Process: What You Should Know

Rubber extrusion ranks among the most common manufacturing methods for producing continuous rubber products such as seals, gaskets, profiles, tubes, cords, and weatherstrips. In case you are engaged in product design, engineering, procurement, or maintenance, knowledge of the rubber extrusion process will assist you in selecting suitable products, communicating effectively with manufacturers, and saving money by not making errors. Here is an easy and simple manual outlining the essential information about rubber extrusion, starting with the key process steps involved, its practical advantages, and common applications.

What Is Rubber Extrusion?

Rubber extrusion is basically a method where a raw (non-vulcanized or uncured) rubber mixture is pushed through a specially shaped hole called a die to get a continuous profile having the same cross-section.

1.EPDM / Sponge Rubber: One of the main choices in the production of rubber products is EPDM, which is mainly used for outdoor and weather-exposed applications, and is therefore suitable for a long lifespan.

• To illustrate the point, one can compare it with squeezing toothpaste out of a tube, the shape of the opening (die) determines the shape of the product.
• Most of the time, after rubber extrusion, the rubber is also cured (vulcanized) to be able to retain the characteristics that come with it, like elasticity, strength, and wear-resistance.

Key Steps in the Rubber Extrusion Process

a) Material Selection and Compounding

The production requires recognizing the correct rubber compound at first depending on the application characteristics such as temperature range, chemical exposure, flexibility, and hardness. Compounding is a process of mixing base rubber with fillers, plasticizers, curing agents, and additives (such as UV stabilizers or flame retardants) to achieve the desired performance.

b) Feeding and Pre-Heating

Most of the time, the compounded rubber comes in strips or slabs. These pieces are put into the extruder's hopper and slowly pulled in by the screw. Pre-heating warms up the rubber, thus, it becomes more convenient to push it and to mix it in the extruder barrel.

c) Screw Extrusion

A turning screw at the extruder chamber impels the rubber to the front under very high pressure and a temperature kept under control. Throughout this process, the material is mixed, compressed, and homogenized to remove air and achieve uniform properties.

d) The Shaping

The heated rubber is forced through a metal die of precise dimensions that essentially determines the cross-sectional shape of the rubber. The die layout has to take into account the expansion, contraction, and flow properties so that the final heat-cured profile is of the correct size.

e) Curing/Vulcanization

The rubber just made by extrusion can be soft and not yet fully functional. It has to be cured or vulcanized to be able to hold its final strength and elasticity. Depending on the material and production facilities, curing is possible in hot air ovens, salt baths, steam autoclaves, or continuous microwave/infrared tunnels.

f) Cooling and Sizing

The profile is chilled (usually by air or water) to fix the dimensions after mending. If the tolerances are very close, sizing tools or calibrators can be used to ensure cross-section accuracy and lessen the effect of warpage.

g) Cutting, Splicing, and Finishing

By the use of different methods, the chilled extrusions are cut to the desired length, coiled for further operations, or spliced to form endless rings or frames. There are also some additional steps that may consist of punching holes, applying adhesives, surface finishing, printing, or quality nspection.