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Effect of plasticizer on the volume resistivity of PVC cable

Keywords: PVC; plasticizer(DOTP, DOP, DIDP, DIOP, DINP, TOTM); cable; volume resistivity

This study investigates the effects of different plasticizers and their concentrations on PVC cable material resistivity

Study Methodology

1. Sample Preparation: PVC resins from five manufacturers (A/B/C: calcium carbide process; D/E: ethylene process) were blended with stabilizers, stearic acid, and varying amounts of plasticizers (DOTP, DOP, DIDP, DIOP, DINP, TOTM). The plasticizer content ranged from 26 to 56 parts per 100 parts of PVC.
2. Processing: Samples were mixed in a two-roll open mill at 155–160°C (roller speed ratio 1:1.35) and compression-molded in a flat vulcanizing machine (160°C, 0.2 MPa preheating for 5 min, 15 MPa hot pressing for 3 min, and 15 MPa cold pressing for 3 min).
3. Volume Resistivity Testing: Conducted according to GB/T 8815-2008 and GB/T 1410-2006 standards using a high-resistance meter (ZC-36).

Experimental Design

1. Materials:
   • PVC resins (Type 5, calcium carbide/ethylene processes).
   • Additives: Calcium-zinc stabilizer (Adik Chemical), stearic acid (Indonesia Sineen), plasticizers (DOTP, DOP).
2. Equipment: Two-roll open mill, flat vulcanizing machine, high-resistance meter, analytical balance.
3. Formulation:
   • Fixed components: PVC (100 parts), stabilizer (3.5 parts), stearic acid (0.8 parts).
   • Variable component: Plasticizer (26, 34, 42, 50, or 56 parts).
4. Procedure: Mixing → Plasticization → Molding → Resistivity Testing.

Results and Analysis

1. Plasticizer Type and Concentration Effects:
   • At 26 parts plasticizer, resistivity ranking (from highest to lowest) was: DOTP > TOTM > DIOP > DINP > DOP > DIDP.
   • With increasing plasticizer content, resistivity trends diverged (Table 2):
     • Low concentration (26–34 parts): DOTP/DOTP-based formulations exhibited superior electrical performance.
     • High concentration (≥42 parts): DOP/DIDP showed sharper resistivity declines due to enhanced ion mobility.

2. Calcium Carbide vs. Ethylene Process PVC:

• Calcium carbide PVC consistently showed lower resistivity than ethylene process PVC
• Thermal instability and broader molecular weight distribution in calcium carbide PVC amplified resistivity reductions with plasticizer addition.