FLAME PROTECTION

Flame retardants with Kelewell products

Wildfires, uncontrolled flames, and the constant threat of natural disasters make effective fire protection an essential part of our safety measures.

In this context, flame retardants play a crucial role. These substances not only protect property but also safeguard human lives. From monoammonium phosphate, diammonium hydrogen phosphate, potassium nitrate to strontium nitrate and ammonium polyphosphate: these materials act as tireless guardians against the destructive power of fire.

Let's take a closer look at how they work, their applications, and the heroic role they play in our daily lives.

Aerosol flame retardants

The concept and formation of thermal aerosols

An aerosol is a physical form originating from colloid chemistry. Similar to colloids where particles are suspended in a liquid, an aerosol is a multiphase fluid where a gas forms the continuous phase, and a solid or liquid forms the dispersed phase. In the context of firefighting, the term "hot aerosols" refers to aerosols that carry thermal energy and can achieve extinguishing effects through chemical reactions. For example, it is believed that the coronavirus can be transmitted through airborne hot aerosols.

The development history of the hot aerosol fire extinguishing system:

First Generation: In the early 1960s, aerosol fire suppression technology, also known as smoke suppression technology, was created.
Second Generation (Aerosol of K-type): Developed by the Beijing University of Science and Technology, it utilizes potassium nitrate and inert gas for chemical reactions. Although the extinguishing effect was improved, it contains substances, due to high potassium ion levels, that can damage electronic devices, leading to a decline in its market use.
Third Generation: Successfully developed in 1999, it primarily uses strontium nitrate and inert gas as the main active ingredients. The main difference from the second generation is that strontium ions do not absorb moisture and do not cause damage to electronic devices, while being non-toxic, harmless, and non-polluting to humans.

The operating principles of the hot aerosol extinguishing system:

The four elements of burning are combustible materials, ignition sources, unhindered chain reactions and auxiliary fuels. The operating principle of aerosol extinguishing is to eliminate one or more of these elements. Heat absorption and chemical inhibition play a decisive role here.

Principles of Heat Absorption and Cooling: Particles of metal salts absorb a significant amount of heat at high temperatures by undergoing physical processes such as melting and gas formation. This reduces the flame temperature, thereby slowing down the combustion reaction.
Chemical Inhibition:
- Gas-phase Chemical Inhibition: Upon thermal exposure, gas-form metal ions or positively charged ions disintegrated in an aerosol can react with active radicals in combustion, forming an affinity reaction. This results in repeated significant consumption of active radicals and a reduction in combustion radicals.
- Solid-phase Chemical Inhibition: The tiny particles in the aerosol have a small size (10-9 to 10-6 m) and a large surface area, allowing them to adsorb active radicals in combustion. This leads to chemical reactions where a substantial amount of active radicals is consumed.

The features and benefits of the hot aerosol extinguishing system:

Harmless to humans: The aerosol extinguishing agents of Class S mainly consist of N2 with small amounts of CO2 and solid metal salt particles, and they are non-toxic to humans. During the actual extinguishing process, the fastest release of Stat-X aerosol extinguishing agents is only 8 seconds (30g active substance) and is harmless to humans.
High extinguishing performance without damage to electronic devices: The aerosol of Class S, based on strontium (Sr), does not absorb moisture due to the main oxidation product decomposition of strontium nitrate (SrO, Sr(OH)2, SrCO3). It does not form a conductive and corrosive electrolyte solution, avoiding damage to devices.
High extinguishing performance: Compared to conventional extinguishing agents, the consumption is lower, while the extinguishing performance is higher.
Weight and space savings: The aerosol extinguishing system is stored in solid form at normal temperatures. The weight is only 1/40 of inert gas, and the space requirement is only 1/15.
Environmentally friendly: The aerosol extinguishing agent contains no substances that harm the ozone layer. The ODP and GWP values are zero, making it an ideal replacement for halons.
Easy installation: The Stat-X aerosol extinguishing system, compared to other domestic aerosol or gas installations, does not require additional wire connections. It only needs to be securely mounted on the wall or inside a housing with a simple bracket, making installation extremely simple and time-saving, and no maintenance is required.
Long shelf life: This is one of the greatest advantages. The shelf life of conventional fire extinguishers is about 2-3 years, requiring annual checks and substance replacements. Domestic aerosol extinguishing agents have a shelf life of 5-6 years, requiring inspection or substance replacement every 1-2 years. The Stat-X aerosol extinguishing system has a shelf life of 10-12 years without the need for maintenance or substance replacement during this time, significantly reducing workload.

Powder flame retardants

ABC Powder fire extinguishers and MAP

Monoammonium phosphate (MAP) is a chemical compound commonly used as a fire extinguishing agent, especially for Class A, B, and C fires. Here's how it works and its application in fire extinguishers:

Class A Fires: Monoammonium phosphate is effective in extinguishing Class A fires, which involve common combustible materials such as wood, paper, fabrics, and plastics. MAP works by smothering the fire and creating a barrier between the fuel and oxygen. It cools the fire and helps prevent re-ignition.

Class B Fires: MAP is also suitable for extinguishing Class B fires, which involve flammable liquids and gases such as gasoline, oil, and grease. It works by forming a barrier on the surface of the flammable liquid, cutting off the oxygen supply and suppressing the fire.

Class C Fires: Class C fires involve energized electrical equipment. Monoammonium phosphate is non-conductive, meaning it can be safely used on Class C fires to extinguish the fire without risking electrical shocks or damage to the equipment.

Monoammonium phosphate is a dry chemical fire extinguishing agent and is commonly used in fire extinguishers due to its versatility in combating various types of fires. When discharged from a fire extinguisher, it typically emerges as a fine powder that covers and envelops the burning materials or fuel source, effectively smothering the flames and preventing the spread of the fire.

However, it's important to note that while MAP may be effective for many types of fires, it may not be suitable for all situations. For example, it is not recommended for Class D fires involving combustible metals. In such cases, specialized extinguishing agents for metal fires should be used.

When using a fire extinguisher containing monoammonium phosphate, it is crucial to follow proper safety procedures and discharge the extinguisher in a manner that maximizes its effectiveness. It is also important to identify the type of fire you are dealing with and select the appropriate fire extinguisher for the specific fire class to ensure safety and effective fire suppression.

DAP (Diammonium Hydrogen Phosphate) as a flame retardant:

DAP can be successfully used as a flame retardant, especially in combating forest fires.

The application of DAP has the following important effects:

Reduction of combustion temperature: DAP causes a decrease in the combustion temperature of materials. This effect is crucial to mitigate the impact of fires.
Reduction of weight loss rates: The use of DAP leads to a decrease in the maximum weight loss rates during combustion. This is particularly effective in reducing the intensity of fires.
Increase in residue formation (char formation): DAP contributes to the formation of more residue or char during the combustion process. This is important to reduce the amount of available fuel and promote the creation of firebreaks for fire containment.

The application of DAP as a flame retardant in combating forest fires has proven to be highly effective. This substance is a key component of many commercial firefighting products. Additionally, DAP is even found as an ingredient in "fire-safe" cigarettes.

Use of ammonium polyphosphate (APP) as a flame retardant:

Applications:
- Ammonium Polyphosphate (APP) is used as a flame retardant in various applications, including paints and coatings.
- In various polymers, especially in polyolefins like polypropylene, APP is part of intumescent systems.
Polymer Applications:
- Polyolefins: APP is found in intumescent systems, particularly in polypropylene.
- Thermosets: APP is used in unsaturated polyesters, yellow coatings, epoxides, and polyurethane casting resins, often in combination with synergists.
- Polyurethane Foams: APP is also used for flame retardant treatment of polyurethane foams.
Properties of Ammonium Polyphosphates:
- APP in polymers has long chains and specific crystallinity (Form II).
- Starts to decompose at 240 °C, releasing ammonia and phosphoric acid.
- Phosphoric acid acts as a catalyst in the dehydration of carbon-based polyalcohols.
Mechanism of Action:
- In the gas phase, the release of non-combustible carbon dioxide helps dilute oxygen.
- In the condensed phase, a carbon-containing protective buffer forms, protecting the polymer from attacks by oxygen and radiant heat.
Intumescence (Expansion):
- In combination with starch-based materials like pentaerythritol and melamine, APP achieves intumescence.
- The mechanisms of expansion and the mode of action of APP are described in several publications.

Recognizing the firefighters:

In closing, we would like to extend our sincere appreciation to all the brave firefighters who tirelessly dedicate themselves to protecting our communities. Their dedication, determination and commitment deserve the utmost respect. Day in and day out, they are on the front lines fighting fires and protecting lives. Through their selfless service, they play a vital role in making our world a safer place. We are deeply grateful for their dedication and the enormous contribution they make to minimizing danger. A heartfelt thank you to all firefighters worldwide for their courageous service. Their sacrifice and bravery are a source of inspiration to us all.