Smoke Suppression in PVC Plenum Cable Jackets

Fire Technology, 2004

Spread of fire along electrical cables may be alleviated by using flame-retardant smoke suppressant (FRSS) additives-based PVC compositions designed for use as insulation and sheathing. These compositions offer improved resistance to ignition, flame spread and smoke generation. FRSS protection may also be achieved by the application of intumescent coatings as fire-protective layers and barriers for electrical cables and cable installations. Metal-based organic (MBO) complexes were synthesized for use as flame retardant smoke suppressants in PVC formulations. Plasticized PVC compositions were prepared and evaluated for their fire performance. Excellent smoke suppression was observed when either of the two MBOs was used. The limiting oxygen index was also found to be fairly high, particularly when the PVC samples were plasticized with a phosphate plasticizer. Flame-retardant smoke-suppressant intumescent coatings were developed for PVC-sheathed electrical cables. The coatings were applied on cables, and their fire performance was evaluated by using national and international standard procedures. The coated cables did not show any surface spread of flame on exposure and their generation of smoke was found to be very low. The coatings were found to be quite effective in reducing the burning behaviour of power cables. Significant improvement in circuit failure time was noted for coated cable specimens.

2021

A new generation of formulations of PVC compounds for producing CPR cables has been developed. Those formulations have shown an extremely low smoke acidity and smoke density during combustion, compared with the old PVC compounds' generation. Smoke acidity has been measured with EN 60754-1 and EN 60754-2. EN 60754-2 is the technical standard to determine the acidity additional class for cables, according to Regulation (EU) N. 305/2011 (CPR), EN 50575 and EN 13501-6, harmonizing the rules for construction products in the European Union. Furthermore, in the presentation EN 60754-1 and EN 60754-2 have been compared. EN 60754-2 requires extremely high temperatures without a heating regime. In these conditions the hydrochloric acid (HCl) evolves fast, and acid scavengers cannot trap it efficiently. On the contrary, the heating regime and the lower temperature of EN 60754-1 represent better the evolution of temperatures in a real fire scenario. M. Piana, G. Sarti

The purpose of this paper is to present an overview of the various technologies used to flame retard and smoke suppress PVC. It gives guidelines on how to formulate PVC using these additives and also discusses the effects these additives have on the physical properties, heat stability and processibility of PVC compounds using them. It is impossible to discuss every aspect of the flame retarding and smoke suppressing of PVC in a paper designed to be presented in a 30-minute talk. However, this paper offers both beginning and experienced formulators useful information in this area.

Journal of Applied Polymer Science, 2010

Combustion and smoke emission properties of PVC compounds, modified with copper (II), molybdenum, and zinc oxides, were studied using cone calorimeter, limiting oxygen index (LOI) and thermogravimetry coupled with mass spectrometry (TG/MS). Results showed that the metal oxides have a very significant effect on the combustion and smoke suppression properties of the PVC compounds. The results also confirmed the anticipation mechanisms of the dehydrochlorination reactions, reductive coupling, and elimination of benzene resulting from the presence of copper (II), molybdenum, and zinc, indicated by the increasing content of postcombustion char residue and the significant reduction in benzene production, indicated by the MS measurements performed. The results also provide indications that the combination of the copper (II) and molybdenum oxides is the one with the best balance of combustion properties, as it reduced the heat released and promoted the suppression of smoke more efficiently. The formulations containing ZnO, because of their strong Lewis acid character, indicated a less pronounced reduction of smoke released during the combustion process, when compared with copper (II) and molybdenum oxides.

2019

The cone calorimeter, under free and restricted ventilation conditions, was used to investigate the toxic emissions from PVC cable fires. Toxic gases were measured using direct high temperature gas sampling from the exit of the cone calorimeter with a short chimney attached to the exit from the electrical cone. Toxic species CO and HCl were identified as a function of time using a heated Gasmet FTIR. The particle number was determined using the Cambustion DMS500 fast response particle sizer with a diluted sample taken from the diluted cone calorimeter exhaust flow at the same location as the optical obscuration smoke meter. The HCl concentrations from the Chlorine in the PVC sheath demonstrated HCl levels well above the LC50 concentration for HCl. The restricted ventilation reduced the peak fire heat release rate and the peak toxicity and HCl occurred later than for free ventilation. The equivalence ratio in the gases from the combustion zone, were both rich at 1.5 for free ventilat...

Polymers in Fire Protection, 2023

In this entry, fire protection of polymeric materials has been discussed with respect to flameretardant polymers as well as additives employed. Flame retardants for polymer and their potential suitability for use in fire applications have been reviewed. Five principle types of flame retardants were discussed for inclusion in polymers, namely halogen, phosphorus, nitrogen, silicon, and organic flame retardants. In this regard, the choice of polymer matrix, additive, processing techniques and characterization method is important for the formulation of high-performance nonflammable system. The influence of polymers and modified flame retardant addition on flame retardation and smoke suppression features have been investigated using cone calorimetric methods, limiting oxygen index measurement, and thermogravimetric analysis. Consequently, it was observed that with increasing flame retardant content, significant enhancement in flame retardancy features may occur.

Journal of Applied Polymer Science, 1986

The addition of an effective transition metal-based smoke retarder to rigid poly(viny1 chloride) (PVC) has three general effects during combustion and inert atmosphere pyrolysis: (1) smoke formation is reduced; (2) char formation is enhanced; and (3) volatile aromatic pyrolyzate formation is reduced while aliphatic pyrolyzate formation is enhanced. A very efficient molybdenum-copper smoke retarder additive has been developed for PVC. It consists of an equal weight mixture of melaminium beta-octamolybdate and copper(I1) oxalate. This combination is synergistic in reducing smoke during the combustion of PVC, i.e., the mixture is more effective than either of the two ingredients used individually a t the same concentration as the mixture. The molybdenum-copper system reduced smoke effectively in three rigid PVC compounds, two of which resemble commercial formulations. The combustibility and pyrolysis effects of this molybdenum-copper additive can be interpreted in terms of an "early crosslinking" mechanism of smoke retardation in PVC. In this mechanism the metal smoke retarder works primarily by catalytically promoting early crosslinking of decomposing PVC chains to yield char as a residue.

2003

Metal-based organic complexes (MBO) are a class of FRSS additives that comprise a transition metal and an organic ligand that cleaves at an elevated temperature thereby releasing the metal in a reactive state. They help in the formation of char and thus act as an effective smoke suppressant. Use of MBO complexes as flame retardant smoke suppressants, phosphate ester as a flame retardant and active filler as endothermic material is reported here as multicomponent FRSS systems. MBOs used in the present study are the chelates of pentanediono. They were used alone as well as in combination with aluminum trihydrate (ATH) as filler were used to impart flame retardancy and smoke suppression to poly vinylchloride. Their performance was measured in terms of flammability, smoke generation, char formation and evolution of combustion gases. MBOs of molybdenum and chromium were found to be very efficient flame retardant smoke suppressants.

Journal of Fire Sciences, 2008

Smoke is considered to be the main fire hazard but its production depends on major variables, principally the chemical character and the burning rate of the polymer plus the availability of oxygen and hence ventilation. The main aim of this work is to study the effect of smoke suppressants on flammability and smoke production of flame retarded unsaturated polyester resinnanocomposites using four different testing regimes representing different fire scenarios. Samples containing zinc borate, zinc stannates, ammonium polyphosphate with and without nanoclay were analysed for smoke generation using cone calorimetry (well-ventilated fire), a tube furnace (fully developed fire) and a smoke density chamber (under-ventilated fire). Carbon monoxide and carbon dioxide measurements using TG-EGA (thermogravimetry-evolved gas analysis), cone calorimetry and tube furnace have also been analysed and compared. Results have confirmed that the production of smoke, carbon monoxide and carbon dioxide depend upon smoke suppressants

Journal of Polymer …, 1981

The amount of smoke suppression induced in PVC by some metal oxides was measured as a function of temperature. The amount of COz evolved in the combustion was also measured simultaneously with smoke emission. Our results show that in a smoldering condition smoke occurred almost immediately, whereas COz occurred a t a later stage. A good correlation was found between smoke density and char yield in nitrogen, and the amount of benzene suppression, induced by metal oxides, also correlated well with the char yield. These facts are taken as evidence that crosslinking catalyzed by metal oxides is the principal mechanism of smoke inhibition and that char oxidation is responsible for the reduction of char yield.