Compare Plasticizer DINP and DOP in PVC Waterproof Membrane

Keywords: Plasticizer, DINP, DOP, PVC waterproof membranes, low-temperature performance, weathering resistance

1. Plasticizers: The Core Factor Influencing Durability of PVC Waterproof Membranes

The flexibility and durability of PVC waterproof membranes are critically dependent on plasticizers. DINP is better than DOP in terms of low-temperature performance and resistance to migration after weathering, as shown by the following results:

1. Superior Low-Temperature Performance:
   • After 1,000 hours of UV aging, DINP-formulated samples maintained a low-temperature brittleness threshold of >-20.5°C, while DOP-formulated samples fell below -20°C (see Figure 1).
2. Enhanced Migration Resistance:
   • Long-term thermal aging tests (80°C × 15 days) revealed significantly lower mass loss rates for DINP compared to DOP, indicating stronger chemical stability and reduced risk of migration into adjacent materials like EPS insulation boards.

2. Mechanism of Action: Molecular Structure and Performance

1. Molecular Differences:
   • DINP has a lower relative molecular weight (210) and flash point (216°C) than DOP (391 and 418°C), enabling better thermal stability under prolonged exposure.
   • The elongated molecular structure of DINP forms a more uniform plasticizing network, reducing stress concentration and improving impact resistance.
2. Weather Resistance:
   • UV aging tests showed minimal surface degradation for DINP-formulated membranes (only slight yellowing), whereas DOP formulations exhibited resin degradation and cracking risks (see Figure 1).

3. Synergistic Optimization Strategies: Filler Content and Membrane Thickness

1. Optimal Filler Dosage:
   • Exceeding 20 parts of heavy calcium carbonate filler led to a noticeable decline in low-temperature impact resistance due to stress concentration at filler aggregation points (see Figure 1). A filler content ≤20 parts is recommended.
2. Thickness Matters:
   • Increasing membrane thickness from 1.2 mm to 2.0 mm reduced mass loss rates by over 30% after thermal aging, with no significant loss in low-temperature performance (see Table 4). Thicker membranes (≥2.0 mm) are strongly advised for exposed applications

4. Practical Application Recommendations

1. Plasticizer Selection: Prioritize DINP over DOP, especially in cold climates or long-term exposed projects.
2. Formulation Design:
   • Use 60–63 parts DINP per 100 parts PVC to balance flexibility and durability.
   • Incorporate 5% titanium dioxide and 0.2% UV absorbers to enhance photostability.
3. Construction Safeguards:
   • Install an isolation layer between PVC membranes and EPS boards to prevent plasticizer migration-induced softening.