Rubber Cords

Quick Answer: Rubber Cords are lengths of solid, flexible rubber with a round or similar profile, supplied for cutting to length. A rubber cord can be joined into a seal or O-ring, used as a flexible tie, or stretched in physics practicals on elasticity.

Seals, Ties and Stretching Experiments

In the workshop and prep room, cord is the raw material for custom seals. A length cut square and joined with a suitable adhesive forms an O-ring or gasket for a lid, a tank or an apparatus groove where no standard ring fits. Short pieces also make bumpers, grips and flexible ties that hold items without scratching them.

In physics, rubber is the classic contrast to a metal spring. A steel spring obeys Hooke’s law over its working range, extending in proportion to load. Rubber does not: its extension-load graph curves, it stiffens at large strains, and the unloading curve lies below the loading curve. The area between the two curves, the hysteresis loop, represents energy converted to heat in each cycle, and students can plot it with slotted masses and a metre rule.

The compound, cross-section and diameter decide both the sealing duty and the stretching behaviour, and they are not stated in the listing. For flat seals rather than cord, a laboratory rubber sheet is the alternative.

Specifications

Applications

• Making O-rings and gaskets for lids, tanks and apparatus grooves
• Plotting loading and unloading curves to show hysteresis in rubber
• Comparing the stretching of rubber with a steel spring in Hooke’s law practicals
• Flexible ties and bumpers on models and apparatus

Care & Handling

• Cut cord square with a sharp blade so that joined ends meet fully.
• Stay within the elastic range during experiments; overstretched cord does not return to its original length.
• Wear eye protection when stretching cord under load, in case it snaps.
• Store it coiled loosely, away from light, heat and ozone.

Why Choose LabEquip

Rubber cord is ordered by prep rooms and workshops making their own seals and by physics departments teaching elasticity. LabEquip lists it in the General Lab Products range; tell us the diameter and length on the contact page.

Frequently Asked Questions

Does a rubber cord obey Hooke’s law?

Not over most of its range. Extension is not proportional to load; the graph curves and the cord becomes stiffer at large extensions. Only a small initial region is roughly linear.

What is hysteresis in rubber?

When a rubber sample is loaded and then unloaded, the unloading curve lies below the loading curve. The area between them is energy turned into heat in the rubber during each cycle.

How do I make an O-ring from cord?

Cut the cord to the length of the groove’s centre line, cut both ends square, and join them with an adhesive suited to the rubber type. Let the joint cure fully before fitting it.

Is it safe to stretch the cord with heavy weights?

Use eye protection and keep feet clear of the masses. Rubber can snap suddenly under load, and a stretched cord recoils quickly. Add masses gradually and stop well before breaking.

Why does the cord feel warm after being stretched quickly?

Rapid stretching releases a little heat, an effect linked to how rubber’s long molecules line up as it extends, and energy lost through hysteresis also appears as heat.

Which cord should I use for an oily or hot seal?

General rubber swells in oils and weakens with heat. Nitrile cord suits oils and fuels, while silicone cord suits higher temperatures. Match the compound to the conditions before fitting.

Last Updated: September 2026