Why is oxirane oxygen content the decisive quality metric for ESBO buyers?

Why is oxirane oxygen content the decisive quality metric for ESBO buyers?
Oxirane oxygen content is the single most important specification for epoxidized soybean oil because it directly measures the molecule's ability to absorb HCl and stabilize PVC. Chinese national standard sets a floor of 6.0 g/100g, while US-spec buyers typically demand 6.6 or higher. Products below 6.0 are considered off-spec regardless of price. However, pushing above 6.6 brings marginal cost increases without proportional performance gains. Buyers should verify supplier claims using GB/T 1677-2008 or ASTM 1652-04 test methods, request batch-specific certificates of analysis dated within six months, and ideally review multi-batch trend data over 6-12 months to confirm consistency. Third-party reports from SGS, CTI or similar add credibility, but routine factory release documents remain essential for every shipment.