A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC Cables in Fires. I: An Overview of the Theory, Test Methods, and the European Union Regulatory Status

Sarti, Gianluca

doi:10.3390/fire5050127

Cited by 7 publications

(18 citation statements)

References 33 publications

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“…Acid scavengers are remarkable substances designed to prevent thermal degradation and scavenge HCl during the thermal decomposition and combustion of low-acidity PVC compounds for cables [ 38 , 39 , 40 ]. For these reasons, they already are crucial ingredients in formulating PVC compounds.…”

Section: Discussionmentioning

confidence: 99%

Surface Chalking upon Weathering of Dark-Colored PVC Articles and Relevant Stabilizers

Gardi,

Giannone,

Sarti

et al. 2024

Polymers

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PVC items (38% carbon atoms w/w) are environmentally friendly as, unlike polyolefins (86% carbon atoms w/w), they are mainly based on chlorine, one of the most abundant elements on Earth and, so, less based on fossil resources. However, in the eco-design context, articles’ durability plays a crucial role, contributing to the enhancement of their sustainability. In this framework, the research on additives capable of increasing the weatherability of outdoor articles is essential. The theory section of the paper reviews the mechanisms of weathering that lead to PVC degradation and undermine the durability of items such as window frames or roller shutters. The weathering of PVC items is a complex phenomenon, involving photo-chemical and secondary chemical reactions, that yields the formation of conjugated polyene sequences underskin in the absence of oxygen and carbonyls in the surface. Here, the chain scission of the polymer backbone occurs, bringing about the disintegration of the surface of the item and causing the typical discoloration called chalking, especially evident in dark-colored articles. In the experimental section of the paper, the effect of different acid scavengers on item weathering has been studied using a natural outdoor and two accelerated exposures with xenon-arc and Q-UV testing devices. Results confirm that some acid scavengers are efficient in preventing chalking, but some are ineffective or even detrimental. Thus, the PVC formulations of durable articles upon weathering still depend on a complex choice of the appropriate ingredients, and several outdoor and indoor accelerated-weathering tests are needed to predict the articles’ lifetime.

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Section: Discussionmentioning

confidence: 99%

Surface Chalking upon Weathering of Dark-Colored PVC Articles and Relevant Stabilizers

Gardi,

Giannone,

Sarti

et al. 2024

Polymers

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“…After, the solution in bubbling devices is checked to see if pH and conductivities are between 5.50 and 7.50 and be less than 0.5 µS/mm, respectively. If not, it is necessary to repeat the cleaning procedures and adopt the precautions mentioned in Part 1 of this article [27] and EN 60754-2. The tube furnace is ready for the first run when the temperature is stable.…”

Section: Ic Anions and Cationsmentioning

confidence: 99%

“…The water from the bubbling devices and washing procedures is collected in a 1 L volumetric flask filled to the mark. All precautions mentioned in Part I of this article [27] should be taken to prevent errors leading to poor repeatability and reproducibility. Therefore, the smoke acidity measurements should be repeated more times for each sample, and a statistical method for analyzing the measurements should be adopted.…”

Section: Ic Anions and Cationsmentioning

confidence: 99%

A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC in Fires. III: EN 60754–2 and the Species in Solution Affecting pH and Conductivity

Bassi,

Bandinelli,

Delchiaro

et al. 2024

Preprint

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The combustion of PVC cables in fires results in the release of hydrogen chloride gas. In the European Union, Regulation (EU) No 305/2011, in force since 2017, requires the classification of cables permanently installed in buildings for reaction to fire, smoke, flaming droplets, and acidity. The additional classification for acidity is evaluated through EN 60754-2, involving pH and conductivity measurements. This study focuses on the essential research and development of low-smoke acidity PVC compounds for cables, mainly aiming to meet the stringent additional classifications for acidity, a1 or a2, which cannot be achieved with traditional PVC cables. Understanding the chemistry of thermal decomposition and combustion, especially in the presence of hydrogen chloride scavengers, is crucial for meeting the best acidity classification. The article reviews the current tube furnace tests used in the European Union for cable halogen and acidity assessments. It discusses the limitations of the existing method (EN 60754-2) and highlights the potential of emerging tests such as IEC EN 60754-3, which employs ion chromatography for improved sensitivity and specificity. In the experimental part of the article, various standard and low-smoke acidity cable compounds are tested using tube furnace experiments with different heating regimes. The concentrations of cations and anions in solution are measured through ion chromatography and inductively coupled plasma–optical emission spectrometry. This detailed analysis aims to identify the species influencing pH and conductivity, which is crucial for designing effective acid scavengers that do not impact conductivity. The conclusive results emphasize that HCl from PVC thermal decomposition is the primary driver of pH and conductivity, and the contribution from the decomposition of additives and byproducts from combustion is found to be negligible in most of the tested PVC compounds for cables. The findings underscore the importance of understanding the thermal decomposition of PVC compounds to design acid scavengers capable of trapping hydrogen chloride without adversely impacting conductivity.

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“…Low-smoke acidity PVC compounds have been developed to reduce the release of HCl in case of fire. In the low-smoke acidity compounds for cables, acid scavengers at high temperatures acting in the condensed phase are added to capture HCl [23,24]. The consequent reduction of HCl in the gas phase and metal chlorides in the condensed phase inhibits the fire performances of PVC compounds for cables: the consequence is the emission of more heat and smoke despite flame retardants and smoke suppressants added to the compounds.…”

Section: Low-smoke Acidity Compounds and Acid Scavengers At High Temp...mentioning

confidence: 99%

“…Refs. [23,24] detail the main characteristics of the acid scavengers used in this paper, including dispersion properties and mechanism of action. This article compares the formulations with and without acid scavengers acting in the condensed phase.…”

Section: Low-smoke Acidity Compounds and Acid Scavengers At High Temp...mentioning

confidence: 99%

A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC Cables in Fires, IV: The Impact of Acid Scavengers at High Temperatures on Flame Retardance and Smoke Emission

Bassi¹,

Delchiaro²,

Bandinelli³

et al. 2023

Fire

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In PVC compounds, hydrogen chloride plays a fundamental role in ·H and ·OH radical trapping, lowering the flame energy during combustion. Furthermore, it yields actual Lewis acids promoting the cross-linking of the polyene sequences from PVC degradation and bringing a char layer, protecting PVC items from flames. Therefore, PVC is inherently flame-retarded. However, plasticized PVC requires flame retardants and smoke suppressants to enhance fire performance. Low-smoke acidity PVC compounds have been developed to reduce the HCl emission during combustion and, therefore, the acidity of the smoke. They contain potent acid scavengers capable of acting at high temperatures. They react with hydrogen chloride in the condensed phase, making it unavailable in the gas and even in the condensed phase, compromising the reaction to fire and enhancing the smoke produced during the combustion. The effect of the sequestration of hydrogen chloride in PVC compounds for cables by potent acid scavengers is studied in this paper through measurements of oxygen index, heat release, and smoke production. It is noteworthy that the potent acid scavengers strongly affect parameters such as the oxygen index, the fire growth rate in cone calorimetry, the specific (total) heat capacity, and the specific heat of combustion of fuel gases in micro combustion calorimetry. In some formulations, acid scavengers reduce the oxygen index below the values of the formulations without flame retardants and double their fire growth rate. In fact, they neutralize the action of antimony trioxide and Lewis acid precursors commonly used as flame retardants and smoke suppressants in PVC items, making them prone to ignite, release smoke, and spread flame. A new generation of flame retardants and smoke suppressants is needed to keep together the low-smoke acidity and the fire performance in PVC items.

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A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC Cables in Fires. I: An Overview of the Theory, Test Methods, and the European Union Regulatory Status

Cited by 7 publications

References 33 publications

Surface Chalking upon Weathering of Dark-Colored PVC Articles and Relevant Stabilizers

Surface Chalking upon Weathering of Dark-Colored PVC Articles and Relevant Stabilizers

A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC in Fires. III: EN 60754–2 and the Species in Solution Affecting pH and Conductivity

A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC Cables in Fires, IV: The Impact of Acid Scavengers at High Temperatures on Flame Retardance and Smoke Emission

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