Abstract
The composition of electrical wires and cables is of critical importance in controlling fire risks. In this respect, polyvinylchloride (PVC) composites are extensively used. Yet, PVC composites are multiple systems in which the final properties depend on the nature and size of the reinforcement or flame-retardant agent and the type of lubricant used for their preparation. Thereby, in this study two series of PVC composites, with stearic acid and calcium stearate as lubricants were prepared in parallel, and additivated with various commercial minerals as reinforcement/flame retardant agents, such as calcium carbonate, alumina trihydrate (ATH) and HMH (a mineral of hydromagnesite and huntite). Following the structure (by FT-infrared), thermal behavior (thermal analyses and differential scanning calorimetry) and mechanical properties (dynamic mechanical analyses, tensile strength and elongation at break) of PVC composites, the flame-retardant effect of the selected minerals was investigated by measuring the limiting oxygen index (LOI). Only ATH and HMH-based composites presented higher flame-resistance, relative to the control samples, making them suitable for the proposed application. The contact angle was evaluated for determining the hydrophobicity of composites when using ATH or HMH, to get an opinion about the stability of the materials in moist environments. Finally, SEM was used to determine the homogeneity of PVC samples.
Highlights
The composition of electrical wires and cables is of critical importance in controlling fire risks
Considering the present literature, this paper provides an interesting comparative study upon the influence of calcium carbonate with particle size of 1 and 2 mm, of alumina trihydrate (ATH) and hydromagnesite and huntite (HMH) as fillers, and the influence of stearic acid and of calcium stearate, as lubricants upon the thermal, the mechanical, the structural and the flame resistance properties of novel PVC composite formulations with potential applications in the industry for electrical wires and cables
Samples with the two types of calcium carbonate VO1 and VO2, display specific bands around 880 cm-1 attributed to Ca-O vibrations, and bands from 1425 cm-1 corresponding to C-O group from carbonate structure
Summary
While the common endothermic flame-retardant fillers act by releasing water in a single process, HMH works as follows: at temperatures of ~ 220°C begins the thermal dreelceoamsepdoasnitdioantatnedmrpeeleraastuersews aatbeor.vAet5a6ro0u°CndH3M30H°Cp,aCrtOic2leiss accumulate at the surface of the burning PVC composites and form a stable char This final step leads to the hindering of the combustion process and implicitly the propagation of the fire [9, 14,15,16,17]. Considering the present literature, this paper provides an interesting comparative study upon the influence of calcium carbonate with particle size of 1 and 2 mm, of ATH and HMH as fillers, and the influence of stearic acid and of calcium stearate, as lubricants upon the thermal, the mechanical, the structural and the flame resistance properties of novel PVC composite formulations with potential applications in the industry for electrical wires and cables
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