TECGEN71 Product Bulletin
The challenge is balance. More specifically providing the optimal balance of the following factors:
- Breathability (THL – Total Heat Loss)
In the last 5 to 10 years, textile mills and turnout gear manufacturers have worked towards creating fabrics and designing turnout gear that attempt to find that optimal balance . We have seen advancements improving comfort with lighter and more flexible outer shells and face cloths with high lubricity and moisture wicking. As systems have gotten lighter, we have seen TPP (Thermal Protective Performance) averages lower slightly to the 38-42 range.
The challenge is balancing these factors as they are inversely related. For example – Increasing TPP often comes with a tradeoff for weight, bulk and reduction in breathability (THL). The THL average of all the certified composite in the current NFPA 1971 standard is 248.4 with a TPP average of 43.0.
The same inverse relations can be said for fabric strength and its impact to comfort by limiting the THL performance of 3-layer composite systems (outer shell, moisture barrier & thermal liner). Over the past few years, the industry is seeing stronger outer shells with tensile and tear strength numbers that are 3-4x the requirements in the NFPA 1971 standard.
Do these higher strength numbers provide more durability and if so, what is the trade-off for the increased strength?
Based on our years of manufacturing experience, we, at Fire-Dex, believe that at some point, a fabric is strong enough to withstand the demands of the fire service. Exceeding that point can compromise other more important attributes – mainly comfort and THL.
The ultimate goal for TECGEN71 was to create the most flexible, lightest weight, highest THL composite systems in the market without sacrificing thermal protection or durability in the process. Our focus is to address the leading cause of Line of Duty Deaths since NFPA began tracking in 1979 – Heat Stress.
TECGEN71 composite systems deliver the highest THLs with high TPPs and durability. Other outer shells have been designed to be stronger, limiting the ability to deliver the highest THL/TPP combination.
To better understand fabric strength, let’s dig into industry tests and NFPA requirements.
WHAT IS TABER ABRASION?
Taber Abrasion tests involve mounting an outer shell material to a turntable platform that rotates while two Taber abrasive spinning wheels apply pressure to create a rub-wear action against the fabric.
While this test is designed to demonstrate accelerated wear testing and may have some value in material evaluation, extreme caution should be taken when comparing results of various fabrics.
Taber Abrasion is not a required NFPA performance test and has been shown to provide inconsistent results showing no correlation to durability or actual field performance.
On the Taber Abrasion test, TECGEN71 compares good or better than comparable outer shells in the market. In the Fire-Dex laboratory, the Taber Abrasion test follows ASTM 3884 using two H-18 wheels and it is weighted with a 500-gram weight on each side.
The following Taber Abrasion samples were tested at 500 cycles on the same machine, strictly following ASTM methods to ensure the most relevant comparison possible.
Taber Abrasion Results @ 500 Cycles:
WHAT IS TENSILE STRENGTH OR TEAR STRENGTH?
Fabric tear testing is designed to demonstrate the capacity of an outer shell to resist tearing once a rip or cut has occurred. A fabric with adequate tear strength will help keep that rip or cut from becoming larger and potentially compromising the safety of the PPE. This test is important because firefighters are often in situations where small cuts or tears in the outer shell can occur. Tear strength is tested by a machine that uses a piece of already cut fabric and measures the force it takes to rip the fabric along the initial cut.
Tensile strength testing is used to measure how much force it takes to pull a whole, uncut or untorn, fabric apart. It is an indicator of how well a garment will stay together when it has forces applied to it from a variety of situations.
NFPA recognizes the importance of fabric strength (tensile and tear strength) and sets minimum requirements for performance. These requirements make outer shells in PPE the strongest materials in any industry. Tensile Strength must be > 140lbs and Trapezoidal Tear Strength must be > 22lbs.
DOES MORE STRENGTH EQUAL DURABILITY?
Fire-Dex data, collected over the past year, shows that only 0.005% of our entire production has been returned or replaced due to a fabric durability problem. That is 1 out of 20,000 sets of gear.
Most fabric related issues are for color change or other appearance issues and not fabric failures. Interestingly, the returns that were related to fabric failures were outer shells that had some of the highest tensile and trap tear data in the market.
In the chart below, you will see tensile strength differences between a traditional Kevlar®/Nomex® blend and a typical High Strength blend. While the high strength blend shows visibly higher tensile strength numbers, the Kevlar®/Nomex® blend is the most popular fabric in the market and has been proven over the years to be one of the most durable products ever in the fire service.
The TECGEN71 outer shell utilizes a real-world tested and trusted combination of DuPont™ Kevlar®/Nomex® on the face of the fabric with a superstructure of the TECGEN fiber inside, creating a highly durable construction. The Trap Tear strength of TECGEN71 is strong enough to last the wear life expectations of fire departments.
WHAT IS CIRCULAR BEND?
The Circular Bend Test determines fabric stiffness by measuring the amount of force that is required to push a fabric sample through a round hole. Testing is conducted on a steel platform with a 1.5” diameter hole in the center and uses a plunger to push the fabric through the opening.
This test is not a requirement of NFPA but is the optimal testing method to compare fabric stiffness. Less weight/force equals more flexibility.
In summary, TECGEN71, an exclusive outer shell by Fire-Dex, was designed to find an optimal balance of protection, comfort (weight, bulk, flexibility and breathability) and durability. The test data as identified by the NFPA standards reveal that balance. A 3-layer composite system can enjoy high breathability (THL) without sacrificing protection and durability as evidenced by TECGEN71 in combination with DuPont™ Kevlar®/Nomex®.
For more information about TECGEN71, please contact your local Fire-Dex dealer.