Separating ESBO’s contribution to heat stability from initial color

Trial design and interpretation

Sample the same PVC formulation and compare initial color with color after subsequent heat exposure under the same processing history. Relate oxirane oxygen and acid value to the process curve. An acceptable initial color does not settle heat-stability acceptance.

Recording Oxirane oxygen content

Oxirane oxygen content: use the agreed method. Ask for oxirane oxygen as a mass fraction and the analytical method on the COA. Distinguish it from epoxy equivalent weight. Acid value: use the agreed method. State titration method, test portion mass and reporting basis.

Why does a replacement give good initial colour but darken quickly on heating?

Check epoxy value, acid value and stabiliser compatibility. Compare colour under one heat-ageing programme. Secondary plasticization of flexible PVC: Hold primary plasticizer, stabilizer and processing conditions fixed. Compare hardness, color and exudation.

What to record

• Oxirane oxygen
• Acid value
• Heat exposure time
• Color change

Technical references

• Valtris: Plas-Chek 775 epoxidized soybean oil ↗

Products and processes