Santogard PVI in Rubber Compounding

Santogard PVI (CAS 17796-82-6) is a pre-vulcanisation inhibitor used to control scorch in rubber compounds. This page explains what scorch is, how PVI prevents it, and how to use it alongside delayed accelerators.

What is scorch, and why prevent it?

Scorch is premature vulcanisation – the compound beginning to crosslink before it is shaped. It wastes stock and can block the mixer, extruder or mould.

Cause of scorch	PVI response
High processing temperature	Delays cure onset
Highly active cure system	Offsets the scorch risk
Long storage of stock	Keeps the compound uncured in storage
Thick, slow-heating parts	Delays cure until heat penetrates

How PVI works

During processing – PVI keeps the compound from curing at mixing, extrusion and storage temperatures.
On heating to cure temperature – the retarder’s effect is overtaken and vulcanisation begins.
Cure – the accelerator drives a normal cure, so the final properties are not harmed.

PVI is a retarder, not an accelerator: it delays the onset of cure and then lets the cure proceed normally.

Where PVI is used

Application	Why PVI
High-temperature processing	Widens the processing window
Fast-curing compounds	Prevents premature vulcanisation
Stock stored before use	Resists cure in storage
Thick parts	Delays cure for even heat penetration

PVI with delayed accelerators

Combination	Effect
TBBS + small PVI	Extra scorch safety with essentially unchanged cure
DCBS alone	Longest base scorch safety
DCBS + PVI	Maximum scorch safety for the hardest cases

The principle: get the base scorch safety from the accelerator type, and add PVI only as needed. This keeps the cure system simple and, where nitrosamine limits apply, avoids relying on a secondary-amine accelerator when PVI can supply the extra delay instead.

Frequently Asked Questions

What is Santogard PVI used for?

As a pre-vulcanisation inhibitor (anti-scorch agent) to extend the scorch time of rubber compounds.

Is PVI an accelerator?

No – it is a retarder. It delays the onset of cure and does not speed up vulcanisation.

Does PVI slow the cure?

Used at the right level it delays the onset without harming the cure; too much can slow the cure or reduce the state of cure.

How is PVI dosed?

At low levels, tuned on the rheometer so that scorch safety is adequate and the cure still completes.

Can PVI be combined with DCBS?

Yes – for the most scorch-prone compounds, DCBS plus PVI gives maximum scorch safety.