Flame Retardants

Johannes Karl Fink

• Publisher: Wiley-Scrivener
• Year: 2020
• Print ISBN: 9781119750611
• eBook ISBN: 9781119752196
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

This book focuses on the chemistry and applications of flame retardants for polymers and other materials. It starts with a description and types of flame retardants, as well as their properties and chemical structures, to include chlorine- and bromine-containing flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, and silicones. Inorganic materials that serve as flame retardants, such as boron-based additives, graphenes, and others are discussed in detail.

In addition, the following subjects are discussed in detail:

• Flame retardant polymers
• The mechanisms of flame retardants, such as flame cooling, synergetic effects, degradation of flame retardants, and others
• Other flame retardant compositions, such as dripping inhibitors and smoke suppressants
• Testing methods for flame retardants, international standards, human health hazards, such as smoke toxicity and problems with wastes
• Synthesis and fabrication methods, as well as recycling methods
• The application of flame retardants to the coating material using 3D printing, reactive coating, and bulk addition methods
• Non-burning comonomers, foams, nanocomposites and bio-based materials
• Flame retardants with other textiles, such as wool and electrical applications such as batteries

1
Types of Flame Retardants

Polymeric materials are generally subject to burn. Therefore, for safety reasons, flame retardants are added. A measure for the flammability is the limiting oxygen index (LOI). The LOI is the percentage of oxygen in the atmosphere that allows burning under standardized conditions (1, 2). Table 1.1 gives an idea about the flammability.

A series of flame retardants with different chemical structures exists and the mechanism of action is dependent on the nature of the particular compounds.

There are monographs dealing with flame retardant materials (3–6).

1.1 History of Organic Flame Retardants

The history of organic flame retardants has been detailed in an article (7) as follows:

Polychlorinated biphenyls were manufactured and used as flame retardants from the late 1920s until the mid-1980s, although polychlorinated biphenyls were also used in a multitude of other applications, particularly in electrical equipment. Other chlorinated compounds came into use as flame retardant, probably from the 1960s onwards, sometimes also including a phosphate group, such as the tris-(2,3-dichloropropyl) phosphate and tris-(1,3-dichloro-iso-propyl) phosphate (8).

Table 1.1 Limiting oxygen index of selected materials (9–11).

Material	LOI/[% Oxygen]
Poly(formaldehyde)	15
Poly(ethylene oxide)	15
Styrene-butadiene rubber	16.9
Poly(methyl methacrylate)	17
Poly(acrylonitrile)	18
Poly(ethylene)	18
Poly(propylene)	18
Acrylonitrile-butadiene-styrene	18.0 – 39
Cellulose acetate	18 – 27
Poly(butadiene)	18.5
Poly(styrene)	18.5
Poly(imide)	18.6
Cellulose butyrate	18.8 – 19.9
Cellulose	19
Styrene acrylonitrile copolymer	19.1
Poly(ethylene terephthalate)	21
Poly(vinyl alcohol)	22
Poly(amide) 66	23
Wool	25
Silicone rubber	25
Poly(carbonate)	27
Aramid	28.5
Poly(vinyl chloride)	42
Poly(vinylidene fluoride)	44
Isocyanurate foam	29
Phenol formaldehyde	35
Poly(benzimidazole)	38.0 – 43.0
Poly(vinylidene chloride)	60
Carbon	60
Poly(tetrafluoroethylene)	>95.0

The brominated analog of the former compound, tris-(2,3-dibromopropyl) phosphate made headlines in the 1970s due to its use in children’s pajamas (12).

At the beginning of the 1970s, an increasing number of brominated flame retardants (BFrs), e.g., polybrominated biphenyls and polybrominated diphenyl ethers, came on the market. In 1997, the World Health Organization tried to list all major flame retardants, also including any inorganic chemicals used in that role (13).

The first review of BFrs appeared in 1995 (14), including what was known of their analysis, toxicity and environmental occurrence. Numerous other reviews and/or assessment documents have been published since then (15–19).

Among the most recent documents concerning BFrs are five published opinions from the European Food Safety Authority (EFSA) on polybrominated biphenyls (20), polybrominated diphenyl ethers (21), hexabromocyclododecanes (HBCDDs) (22), tetrabromobisphenol A and its derivatives (23), and also an opinion concerning other phenolic BFrs and their derivatives (24). EFSA is presently also preparing an opinion on emerging and novel BFrs for publication in 2012. In 2011, a book on BFrs was published which covered a multitude of issues relating to BFrs (25).

Other major reviews of BFrs from 2005 onwards are included in (26–29).

A review on phosphorus-containing flame retardants was published (30), while, among the chlorinated flame retardants, only the Dechloranes have been comprehensively reviewed (31).

The scientific literature of bromine-, chlorine- and phosphate-containing flame retardants was reviewed (7). The compounds mentioned are collected therein. Also, the trade names are given. The chemical names of these compounds are given in Table 1.2.

1.2 Commercially Available Flame Retardants

Some commercially available flame retardants are listed in Table 1.3.

Table 1.2 Bromine-, chlorine- and phosphate-containing flame retardants (7).

Compound name
2,4-Dibromophenol
Dibromostyrene
2,4,6-Tribromophenol
1,3,5-Tribromo-2-hydroxybenzene
2,4,6-Tribromophenyl allyl ether
1,2,4,5-Tetrabromo-3,6-dimethylbenzene
1,4-Dimethyltetrabromobenzene
2,3,5,6-Tetrabromo-1,4-dimethylbenzene
2,3,4,5-Tetrabromo-6-chlorotoluene
Tetrabromo-o-chlorotoluene
2,3,4,5-Tetrabromo-6-chloromethylbenzene
1,3-Isobenzofurandione
3,4,5,6-Tetrabromophthali...

Table of contents

• Cover
• Table of Contents
• Title Page
• Copyright Page
• Preface
• 1 Types of Flame Retardants
• 2 Mechanisms of Flame Retardants
• 3 Dripping Inhibitors
• 4 Smoke Suppressants
• 5 Standards and Testing
• 6 Synthesis and Fabrication Methods
• 7 Examples of Polymers
• 8 Special Uses
• Index
• Also of Interest
• End User License Agreement