What are the differences between DOP and DOTP?
DOP (dioctyl phthalate) and DOTP (dioctyl terephthalate) are both widely used PVC plasticizers, but they differ significantly in chemical structure, safety, performance, regulation, cost, and applications. DOP is a phthalate with potential health risks and stricter regulations, while DOTP is a non-phthalate with better stability, lower volatility, and better electrical insulation, making it more suitable for high-performance and environmentally friendly applications.
Core Differences
1. Chemical Structure
- DOP: An ortho-phthalate ester derived from phthalic acid (benzene-1,2-dicarboxylic acid), with two 2-ethylhexyl groups attached to the ortho-positioned carboxyl groups of the benzene ring.
- DOTP: A terephthalate ester derived from terephthalic acid (benzene-1,4-dicarboxylic acid), with two 2-ethylhexyl groups attached to the para-positioned carboxyl groups of the benzene ring, resulting in a more rigid and stable molecular structure.
2. Safety and Toxicity
| Aspect | DOP | DOTP |
| Classification | Potential endocrine disruptor; reproductive toxicant; 2B carcinogen (IARC) | Non-phthalate; generally considered safer with no endocrine disruption concerns |
| Migration/Leaching | Higher tendency to migrate from PVC matrix | Lower migration rate; better retention in the polymer |
| Regulatory Scrutiny | Strict restrictions in EU (REACH), US (CPSIA), etc., especially for toys, food contact, and medical devices | Widely compliant with global standards; preferred for export and high-safety applications |
3. Key Performance Parameters
| Parameter | DOP | DOTP | Advantage |
| Thermal Stability | Flash point ~195°C; lower heat resistance | Flash point ~210°C; better thermal stability; less volatile at high temperatures | DOTP (for high-temperature processing) |
| Volatility | Higher volatility; more prone to evaporation loss | Lower volatility; slower loss over time; longer product lifespan | DOTP (for long-term durability) |
| Migration Resistance | Lower resistance; more likely to leach into contact materials | Higher resistance; better retention in PVC matrix | DOTP (for food/skin contact, medical) |
| Electrical Insulation | Volume resistivity ~10¹⁰ Ω·cm | Volume resistivity ~10¹¹ Ω·cm (10× higher) | DOTP (for cables, wires, electronics) |
| Low-Temperature Flexibility | Good plasticizing efficiency at low temperatures | Slightly inferior to DOP in cold flexibility | DOP (for cold-climate applications) |
| Viscosity (25°C) | ~56.5 mPa·s | ~63 mPa·s | DOP (faster solvation in mixing) |
4. Cost and Market Trends
- Historical Cost: DOP was cheaper, but prices have converged in recent years due to economies of scale and regulatory pressures favouring DOTP.
- Total Cost of Ownership: DOTP may offer lower long-term costs due to reduced maintenance, longer product life, and regulatory compliance benefits.
5. Typical Applications
| DOP | DOTP |
| General-purpose flexible PVC (films, sheets, artificial leather, footwear) | High-performance PVC (cable insulation, automotive components, flooring, toys, medical devices) |
| Cost-sensitive products with low migration/heat requirements | Applications requiring thermal stability, low volatility, and high electrical insulation |
| Short-term use items with minimal regulatory constraints | Export-oriented products compliant with global safety standards |
How to Choose
- Choose DOP if you prioritize cost, need better low-temperature plasticizing efficiency, and operate in non-restricted general-purpose PVC applications.
- Choose DOTP if you need higher thermal stability, lower volatility/migration, better electrical insulation, compliance with strict regulations, or longer product lifespan.
Summary
DOP is a traditional phthalate plasticizer with good cost-performance but significant health and regulatory concerns, while DOTP is a non-phthalate alternative with superior stability, safety, and compliance, ideal for modern high-performance and environmentally conscious applications. As regulations tighten and prices align, DOTP is increasingly replacing DOP in many sectors.