How to achieve flame retardancy for low-smoke, low-halogen PVC cables?

Low-smoke, low-halogen PVC cables are widely used in densely populated public areas and important equipment rooms, making flame retardancy essential. Currently, most formulations use antimony trioxide or add some substitutes for flame retardancy. Aluminum hypophosphite can also play a certain flame-retardant role in PVC cables, but its formulation differs significantly from that of antimony oxide. Raw materials include aluminum hydroxide, magnesium hydroxide, molybdenum trioxide, ammonium molybdate, zinc borate, etc. Below, we provide one flame-retardant formulation for low-smoke, low-halogen PVC cables for your reference.

I. Raw Materials and Formulation

Raw Materials: PVC with an oxygen index of 45% or a chlorine content of 62%~65%; Plasticizer combinations I and II: DOP, DOTP, and chlorinated paraffin-70; Filler system: Aluminum hydroxide; Flame retardants: Antimony trioxide (Sb₂O₃) and stabilizers, etc. The formula is as follows:

PVC resin: 100; FB and Sb2O3 combination: 4-6; Plasticizer combination I: 40; Al(OH)3: 20-40; Plasticizer combination II: 20; Antioxidant: 0.5; Stabilizer: 7;

II. Preparation Method

According to the PVC extrusion process conditions, the cable material is extruded. The process flow is: batching → high-speed mixing → cooling → granulation → cutting → cooling → extrusion molding → inspection → packaging

III. Related Effects

When designing the formula, comprehensive factors of PVC cable material must be considered. The optimal low-smoke and flame-retardant effect can only be found through a comprehensive balance of plasticizers, flame retardants, smoke suppressants, and fillers. Using composite smoke suppressants and flame retardants is a good direction. The 70℃ low-smoke flame-retardant PVC cable sheath material meets the performance requirements of GB8815-88, with an oxygen index of 32% and a smoke density of 295, representing a 51% reduction in smoke density. The production process of this formula is the same as that of ordinary PVC cable material, so it is feasible for production. The cable material meets the requirements for cable laying and has a bright surface. The cable passed the I-C332-3 bundled burning test. Currently, there is no national standard for low-smoke flame-retardant PVC cable material, therefore further research is needed to improve its low-smoke flame-retardant performance.