What is Room Temperature Curing Epoxy Resin

Room Temperature Curing Epoxy Resin: The Advanced Electrical Insulation Solution

Room temperature curing epoxy resin (RTC epoxy) is a thermosetting polymer engineered to harden at ambient conditions (20–30°C) without external heat. Unlike thermal-cure epoxies, RTC systems leverage reactive amine/anhydride hardeners to initiate cross-linking, making them ideal for encapsulating sensitive electrical components like current transformers (CT), voltage transformers (VT), and dry-type transformers.

Why RTC Epoxies Dominate Electrical Insulation

1. Energy Efficiency
   Eliminates ovens, reducing manufacturing costs by 40–60% for transformer potting and coil encapsulation.

2. Low-Stress Curing
   Minimal shrinkage (<0.5%) prevents microcracks in delicate windings during transformer encapsulation.

3. Superior Dielectric Properties
   RTC formulations achieve >18–22 kV/mm dielectric strength, critical for medium/high-voltage insulation (1–40.5 kV systems).

Core Electrical Performance Metrics

Key Applications in Power Systems

• CT/PT Encapsulation: Protects instrument transformer coils from environmental degradation.

• Busbar Insulation: Gap-filling compounds for 12–40.5 kV switchgear.

• Dry-Type Transformers: Flame-retardant (UL 94 V-0) potting for windings.

• Insulator Manufacturing: Crack-resistant coatings for outdoor bushings.

Critical Material Advantages

• Moisture Resistance: <0.1% water absorption (ASTM D570) prevents corona discharge.

• Thermal Shock Stability: Withstands -40°C to +150°C cycling (IEC 60068-2-14).

• Vibration Damping: 30–50% stress reduction in CT/VT assemblies.

• Chemical Inertness: Resists oils, SF₆, and partial discharge byproducts.

Processing Methods

1. Vacuum Casting:
   Removes air pockets for void-free insulation in complex CT cores.

2. Automatic Pressure Gelation (APG):
   High-yield production of outdoor insulators and bushings.

3. Vacuum Pressure Impregnation (VPI):
   Deep coil impregnation for motor/generator stators.

Formulation Science

RTC epoxies combine:

• Base Resins: Cycloaliphatic (UV resistance) or Bisphenol-A (mechanical strength).

• Hardeners: Modified anhydrides (low exotherm) or polyamines (fast cure).

• Reinforcements: Silica microfillers (↑ arc resistance), alumina (↑ thermal conductivity).

Example RTC System for 36 kV CTs:

Epoxy Resin (Aliphatic) : 100 pbw  
Anhydride Hardeners      : 85 pbw  
Fused Silica (200 mesh)  : 300 pbw  
CTI Improver Additive    : 5 pbw  
→ Dielectric Strength: 24 kV/mm | PDIV: 12 kV  

Outdoor vs. Indoor RTC Epoxies

Why Engineers Choose RTC Epoxies

• Manufacturing Flexibility: Cures in 4–24 hrs without ovens.

• Lifecycle Reliability: 30+ year service in substations.

• Sustainability: 50% lower carbon footprint vs. thermal-cure systems.