How Flame Retardants Work in Plastics

Flame retardants are chemical compounds added to plastics in order to prevent, delay, or slow down combustion, reduce smoke formation, and/or prevent the material from melt collapse (anti dripping). These additives are common in numerous everyday products to avoid the ignition and burning of plastics.

The most common flame retardants are halogenated compounds, which include brominated and chlorinated types. Halogenated flame retardants are highly effective at relatively low load levels. Non-halogen, or halogen free, flame retardants are increasing in demand and include intumescents (phosphorus-based) and metallic oxides. Non-halogen flame retardants require a higher load level, and often need additional adjustments to maintain the mechanical properties of the plastic.

One must consider several factors when selecting a flame retardant. Getting to the desired performance often requires a tailored solution with several trials.

  • What are the test requirements this part needs to pass (burn time, extinguish time, flame spread, smoke development, industry and government regulations, mechanical properties)?
  • What polymers and additives are used in the part?
  • The design, shape, and surface area of the part also play a critical role in combustion.

Flame retardant additives can be compounded with the base polymer or added during the plastic processing step. Sometimes combustion may be prevented by simply adding the flame retardant to a surface layer finish on the final product.

When plastic burns, long-chain molecules of the polymer chain are degraded into smaller hydrocarbon molecules and flammable gases, such as free radicals – a process called pyrolysis. For a fire to begin, fuel, oxygen, and an ignition source must be present. Flame retardants work by interfering or eliminating one of these key ingredients, either physically or chemically. There are a few common methods that flame retardants employ to inhibit combustion and below is a description of each.

  • Gaseous Inhibition: halogenated compounds such as bromines and chlorines are compatible with many base polymers and are the most common flame retardant additives. During pyrolysis, hydrogen and hydroxide free radicals are produced. During a fire, halogenated flame retardants thermally degrade, releasing hydrogen chloride and hydrogen bromide that react with the free radicals in the flame. These newly formed free radicals include the halogens and are less reactive than the original hydrogen and hydroxide free radicals, thus, suppressing the volume of reactive gases available for combustion reactions. Also, this process slows combustion which in turn cools the system, further reducing combustion.
     
  • Solid Char-Formation: this form of flame retardants is often comprised of non-halogen compounds using phosphorous and nitrogen chemistries. During a fire, these types of flame retardants react to form a thick, solid layer of carbon char on the surface of the plastic. This solid layer insulates and shields the plastic, creating a barrier that interrupts the combustion process by hindering the release of more reactive gases.
     
  • Endothermic Cooling: this class of non-halogen flame retardant includes metallic oxides/ hydrated minerals, such as aluminum and magnesium hydroxides. During a fire, these flame retardants use an endothermic reaction to remove heat and release water molecules. The plastic is cooled and limits the amount of reactive gases being formed, thus hindering the combustion process. The use of hydrated compounds as flame retardants is often limited by the low decomposition temperatures of these materials since plastics processing and manufacturing often occurs at high temperatures.

There are many factors to consider when selecting the right flame retardant for a given application including the base polymer being utilized, the specific government and industry regulations and standards that must be met, as well as the desired properties of the polymer such as viscosity and density. Selecting a flame retardant can be a tricky task, which is why it is important to choose a partner, like Amcor, that has extensive expertise in various flame retardants as well as experience with state-of-the-art compounding and blending processes. Amcor will guide you through the selection process to ensure the right additives are chosen for your specific application.

Amcor

Amcor’s flame retardant additives are called “Amout” and include both halogen and non-halogen types.

Amcor is a manufacturer of polyethylene film and bags, as well as polyolefin compounds, additives, blends, and masterbatches. Amcor has grown from a single product line to hundreds of products and five product divisions. In addition to selling products, we also provide tech support, assistance with your equipment, and process recommendations.

Amcor is also a full line distributor of various chemicals, resins, and gases for the plastic industry. With warehousing and distribution facilities across the United States, Mexico, Eastern Europe and China, we service companies of all sizes and locations across multiple industries.

Amcor realizes that on time delivery, a quality product, and personal service are what it is all about. Contact us today to learn how we can assist with your next project!


What Are Polymer Additives?

What Are Polymer Additives?

Plastics manufacturing has evolved significantly over time. Plastics were originally produced using a few natural materials but now there are thousands of plastics formulated from a wide range of natural and synthetic materials. One of the big changes over time in plastic formulations is the use of polymer additives.

Additives are chemicals added to the base polymer to improve processability, prolong the life span, and/or achieve the desired physical or chemical properties in the final product. While the content of additives is typically only a few percent, their impact on polymer performance and stability is significant. Once the additives are added, the polymer blend is referred to as a masterbatch and is processed accordingly.

 

Types of Polymer Additives

There are countless options when it comes to additives and each one offers a specific improvement to the polymer’s functionality or stability. Selecting the right additives for your polymer may seem like a daunting task - this is why it is crucial to choose a partner, like Amcor, that has extensive expertise in various additives and resins as well as experience with state-of-the-art compounding and blending processes. Amcor will guide you through the selection process to ensure the right additives are chosen for your specific application.

Below are common categories of polymer additives. Even within a specific category, such as flame retardants, there are numerous additive options available; the additive that is best for a given plastic depends heavily on the base polymer (to ensure compatibility) and the application of the final product.

--> Plasticizers: base polymers are often rigid and do not have the necessary flexibility and rheology, or flow, properties that are needed for plastics processing. Plasticizers are added to improve rheology as well as elasticity. Plasticizers are one of the most common polymer additives and an example is phthalate esters used in PVC products.

--> Anti-aging stabilizers: nearly every plastic is prone to degradation when exposed to UV light, such as from sunlight, and oxygen including ozone. The degradation causes brittleness, discoloration, and loss of some physical properties. Additives, referred to as anti-oxidants, stabilizers, or anti-ozonants, are added to combat the deterioration of the plastic and to significantly extend the life span of the final product. Examples of antioxidants include phenols, aryl amines, and phosphates, and examples of UV stabilizers include benzophenones and benzotriazoles. Additionally, black is an excellent UV absorber so paints, dyes, or elemental carbon black are often added to protect products against UV light.

--> Blowing agents: these additives are added to the base polymer and when a specific temperature is reached during processing they decompose, releasing gas that forms a cellular structure within the plastic. This structure reduces density and improves insulation properties. There are many different blowing agents available from salts to complex nitrogen-releasing chemicals.

--> Flame retardants: flame retardants prevent, delay, or slow down combustion. These additives are common in electrical products to avoid the ignition and burning of plastics. Flame retardants can be mixed with the base polymer, or added during the plastic processing step, or even as a surface layer finish on the final product. Halogens such as bromines as well as phosphorus and nitrogen chemistries are common flame retardants.

--> Nucleating agents: these additives improve mechanical properties and transparency. They also speed up the plastic crystallization rate, reducing overall cycle time.

--> Processing: these additives are combined with the polymer to improve the processability and processing characteristics of the material. Examples of processing additives include lubricants, and more specifically, fatty acids, hydrocarbon waxes, and some types of polyethylene.

--> Anti-static: these additives are used to minimize the potential for static electricity build up on the surface of the plastic, and in some cases even prevent it entirely. Examples of anti-static additives include amines, ammonium compounds, and polyethylene glycol esters.

--> Colorants: the purpose of these agents is to change the color of the final product. These additives are often pigments or dyes. The specific dye or pigment selected is largely based on which base polymer is being used as the two materials have to be compatible.

--> Odor: there are also additives to modify the odor of the final product. An example of an odor agent is when a chemical is added to paints to produce a more pleasing smell.

--> Anti-microbial: given the increasing trend in implantable medical devices and other technologies, anti-microbial additives are becoming more popular. These agents protect against deterioration of the plastic and reduce the potential for a microbiological attack.

 

Amcor

Amcor is a manufacturer of polyethylene film and bags, as well as polyolefin compounds, additives, blends, and masterbatches.  Amcor has grown from a single product line to hundreds of products and five product divisions.  In addition to selling products, we also provide tech support, assistance with your equipment, and process recommendations.

Amcor is also a full line distributor of various chemicals, resins, and gases for the plastic industry. With warehousing and distribution facilities across the United States, Mexico, Eastern Europe and China, we service companies of all sizes and locations across multiple industries.

Amcor realizes that quick turnaround, on time delivery, a quality product, and personal service are what it is all about. Contact us today to learn how we can assist with your next project!