Thermoplastic vs Fiberglass
Thermoplastic versus fiberglass. What’s the difference? Which material is better? There are many misconceptions about these two fire helmet materials. Both thermoplastic and fiberglass materials protect firefighters, but they are different and each material has its own specific strengths. Let’s look at the strengths and differences of these two materials.
Today, high-performance thermoplastics offer superior impact protection, durability, and heat resistance. Specialized high-performance plastics can withstand temperatures of 500° F (260° C). However, they can be compromised by exposure to some chemicals. Thermoplastic materials become softer and tougher as they get warmer and harder and more brittle at lower temperatures. These unique properties are helpful in a high-heat environment such as a fire. The perception that a thermoplastic helmet cannot withstand the same heat exposure as a fiberglass model is false.
High-heat thermoplastics are designed to withstand short-term, repeated exposure to temperatures of 500º F (260º C). At this point, bubbling or blistering may occur. When exposed to high heat for a prolonged period of time, plastic begins to absorb moisture. The plastic gets softer and will withstand impact; however, when the helmet cools off a bubbling or blistering can be seen. This should act as a “fail safe” that the helmet has seen too much heat and must be replaced.
Since thermoplastic helmets are made by a process of melting and re-cooling, they are designed to accept the type of re-heating that occurs when fighting fires. Regular inspection, cleaning, and maintenance are necessary to ensure thermoplastic helmets protect firefighters effectively.
When firefighters think of a traditional fire helmet, they most often think of a composite helmet. These fiberglass helmets provide good protective properties. Fiberglass is actually composed of two materials: a thermoset resin (essentially a glue) and glass fibers which can vary in length. Thermoset resins are a family of plastics that do not melt at high temperatures. Thermoset resins are created by mixing two base materials just like epoxy glue. One of the ingredients is a catalyst that, when combined with the other agents during molding, will solidify, locking itself and the glass fibers into a rigid state.
Some manufacturers use other materials such as Kevlar in addition to glass fibers; however, the real strength of the helmet comes from the resin. The resin and the fibers in a fiberglass helmet are formulated to make a product that has a good balance between strength and weight. Fiberglass offers great resilience when exposed to chemical agents; however, the resin of a composite helmet will degrade with repeated exposure to extreme temperatures. Each exposure to high heat weakens the molecular structure of the resin. Lower temperatures will also degrade the resin but over a much longer period of time. Ultraviolet (UV) exposure from sunlight has a similar effect on these resins.
Fiberglass helmets have traditionally shown their best strength against chemical exposure. Today’s fiberglass helmets also protect well in high heat environments.