Crosslinked Polymer Synthesis kit

Quick Answer: The crosslinked polymer synthesis kit lets students join polymer chains together with a crosslinking agent and watch the material change from a runny solution into a gel that stretches, flows slowly and bounces. It shows how structure at the molecular level controls the properties of a polymer.

Chains, Links and Material Properties

A solution of long polymer chains flows because the chains slide past one another. Add a substance that bridges neighbouring chains and they can no longer move freely: the liquid thickens, then sets into a gel. The more crosslinks there are, the stiffer and less stretchy the material becomes, and students can see this progression within minutes.

The classic school version uses poly(vinyl alcohol) solution crosslinked by borate ions from borax. Borate links are weak and constantly break and re-form, so the gel behaves as a viscoelastic material: it bounces if dropped and snaps if pulled sharply, yet oozes and flows if left alone. The title does not name the chemistry used, so confirm which polymer and crosslinker the kit contains before planning the lesson.

Crosslinking explains everyday materials too. Car tyres are vulcanised with sulfur crosslinks, and permanent waving of hair works by breaking and re-forming disulfide crosslinks between protein chains. The difference between thermoplastics and thermosets comes down to crosslinks, which makes this kit a natural partner to the biodegradable plastic film kit in a polymers unit.

Specifications

Care & Handling

• Wear gloves when handling the crosslinker solution and the finished gel, and wash hands afterwards.
• Label gels clearly as laboratory material and do not let students take them home.
• Keep unused polymer solution tightly closed, as it can grow mould over time.
• Dispose of gels as solid waste under local rules; they can block sink drains.

Applications

• Comparing gels made with different amounts of crosslinker to link structure with stiffness
• Investigating viscoelasticity by pulling the gel slowly and then quickly
• Introducing thermoplastics and thermosets in a materials or polymers lesson
• Measuring how high a gel ball bounces or how fast it flows through a funnel as a quantitative extension

Why Choose LabEquip

Chemistry and materials science teachers who want students to connect molecular structure with how a material behaves use a kit like this as a quick, visual practical. LabEquip lists it under chemistry lab equipment; ask about the kit’s chemistry and class quantities through the contact page.

Frequently Asked Questions

What is a crosslink in a polymer?

A crosslink is a chemical bond or strong interaction that joins one polymer chain to another. Crosslinks turn a collection of separate chains into a connected network, which changes how the material flows and stretches.

Why does the gel bounce but also flow?

When the crosslinks in a borate gel are weak and reversible, they hold during a quick impact, so the gel behaves like a solid and bounces. Over longer times they break and re-form, letting the chains slide, so the gel slowly flows like a liquid.

How does crosslinking relate to thermosets?

Thermosetting plastics have extensive permanent crosslinks, so they do not melt on heating. Thermoplastics have no crosslinks between chains and soften when heated, which is why they can be remoulded.

Can students vary the amount of crosslinker?

Yes, and it is the most instructive variation. A small amount gives a thin, stringy material; more gives a firmer gel. Keeping the polymer volume constant while changing the crosslinker volume makes it a fair test.

Is borax safe for students to handle?

Borax and borate solutions should be handled with gloves and kept away from the mouth and eyes, and some regions restrict their use with younger students. Check the safety data sheet and local rules before the practical.

Why does the gel dry out if left uncovered?

Much of the gel is water held within the polymer network. In open air the water evaporates, and the gel shrinks and hardens. Store samples in sealed bags or containers if they are needed for a second lesson.

Last Updated: September 2026