Over the last century, new materials have been discovered as derivatives of petroleum. They are lighter, stronger, and have insulating properties. These are some desirable features in safety work boots. But steel toe boots have their uses, too. Carbon toe is a type of composite toe. They may also be made of fiberglass, Kevlar, aluminum, or titanium. In this discussion, we will compare carbon and steel toes, their uses, and the ASTM Standards they comply with.
What is Carbon Toe?
Carbon fibers are 10 times stronger and 5 times lighter than steel. It is eight times lighter than aluminum and 1.5 times lighter. These fibers are 5 – 10 micrometers or 0.0002 – 0.00039 inches in diameter and composed of carbon atoms.
When observed under a microscope, we see that the carbon atoms bond to make microscopic crystals. These crystals align parallel to the longitudinal axis of the fiber. This structure makes them very strong for their size.
Carbon fibers have many forms that have various applications. For example, thousands of carbon fibers are twisted into yarn to make fabrics. These fibers can be combined with epoxy and molded into various shapes. These composite materials can be molded into safety toe caps for work boots.
There are carbon-fiber-reinforced composite materials, too. They are used to making parts for spacecraft and aircraft. They are used to reinforce car bodies, golf shafts, and safety toes in worker’s boots. These materials are preferred because they are lightweight and very strong.
Carbon fiber is classified by its tensile modulus. The British unit is a pound of force per square inch of the cross-section. Low modulus carbon fibers have a tensile strength of 34.8 million psi or 240 million kPa. The ascending order of tensile modulus is – standard, intermediate, high, and ultrahigh. The ultrahigh tensile modulus is 72.5 -145.0 million psi or 500 million-1.0 billion kPa.
In comparison, steel’s tensile modulus is 29 million psi or 200 million kPa. Evidently lighter and stronger, they also have superior fatigue resistant properties. When composited with the right resins, they are the most corrosion-resistant, too.
Carbon toe boots are reinforced structures made of composite material. This material carries a tensile strength of 50,000 psi and a tensile modulus of 3.8×106 psi. It has a compression strength of 42,000 psi, a specific gravity of 1.9, and a Barcol hardness of 70. The carbon fiber is combined with thermoset vinyl ester. This sheet is molded into a toe cap. The carbon fiber content is 63% and the length of each fiber is one inch. The maximum thickness of the toe cap is between 0.1 to 0.25 inches.
Carbon Toe boots are subjected to the same ASTM Standards for Testing and Performance as the Steel and Composite (carbon) toe boots. Carbon is an insulator, thus offers better protection against flowing and static electricity, making them popular among engineers and electricians. These boots also meet the ASTM and OSHA standards for personnel safety. Especially for personnel working with live wires and electricity.
These boots offer additional protection like metatarsal protection, static dissipative protection, electrical hazard resistance, and puncture resistance. These boots can withstand an impact of 75 foot-pounds and a compression greater than 2500 pounds.
This is printed as – Meets ASTM F2413-11 M I/75 C/75 ratings – on the boot. This information may be printed or embroidered on the boots. They are 30% lighter than the steel toe boots, thus offering higher levels of comfort and less fatigue.
As the boot is made of non-conducting or insulating materials, the feet remain comfortable. Insulation is a boon when working in extreme temperature conditions. The non-conductive materials do not set off security systems with metal detectors. This factor makes these boots perfect for Fly-In-Fly-Out (FIFO) workers when they pass through airports.
There are downsides to the carbon boots is that they cannot withstand as much force as steel toes. Carbon toes rebound after compression but are significantly weakened after impact. Thus, the protection offered reduces proportionately to the number of impacts.
Steel toes offer more puncture protection than carbon toes. To offer the same level of protection; the carbon toe cap is thicker, causing the boot to look bulbous. They are also more expensive than steel toes.
What is Steel Toe?
The protective toe in these boots is made of non-corrosive steel. The toe cap protects the phalanges of the feet. These boots meet the ASTM F2413 Standard for Protective Personal Equipment (PPE). These caps are made of heavy-duty steel. They protect against hazards such as punctures, falling objects, and impact.
They offer higher ‘flat’ protection compared to carbon toes. They do not shatter or snap contrary to popular myth. Thus, there is no toe amputation. They also do not degrade or weaken over time. Therefore, they are preferred by construction workers and people working with heavy machines and tools such as grinders, chainsaws, drills, etc.
The cons are that they are heavier than carbon boots, thus strain the ankle joints. They also set off the metal detectors at security checks. And offer poor insulation in extreme weather.
Carbon Toe versus Steel Toe
Both types are toes may be used in making safety footwear. This protective footwear is manufactured to meet the ASTM Standards, such as the ASTM F2412. To meet this standard, the boots are passed through various tests for Protection of the foot.
The ASTM F2413 Standard measures the performance of a safety toe cap. It tests the safety toe caps’ ability to withstand compression and impact.
The test methods are standardized in the ASTM F2412. The impact test studies the effect of a falling object. While the compression test studies the effect of a heavy object rolling onto the shoe.
All the work boots are subjected to quality control tests at the manufacturing unit. When a brand claims that their boots with steel or carbon toe are ASTM-compliant. It means that the boots offer adequate protection against impact, puncture, and compression.
These boots offer additional protection like metatarsal protection, static dissipative protection, electrical hazard resistance, and puncture resistance. They are marked with a code that specifies the hazard they protect against.
Carbon toe boots are comparatively lighter than steel toe boots. This means lesser fatigue and strain on the joints. If the worker walks around and stands all day – lighter boots help boost productivity. When considering a boot’s weight, the steel toe may not be the only contributing factor.
Consider the heavy-duty soles for protection against puncture and electrical shock. The material of the upper and the insulation may contribute to the weight. Fortunately, boots are made from advanced materials for the upper and insulation that lighten the boot without compromising safety.
The right fit can be achieved by picking the right size. Take time to break into the boots. This will prevent the in-growth of nails, corns, blisters, etc. Try on the boots in the afternoon or evening, with the socks on. The feet are the most relaxed or expanded in the latter part of the day. Carbon toe caps are thicker than steel toe caps to offer the same level of protection.
As the carbon toe boots are made from an insulating material, they are ideal for engineers and electricians. Besides, they help maintain favorable temperature and dryness inside the boot. As opposed to the steel toe boots.
Due to this good conductor, the body’s heat escapes to the cold outside, chilling your feet. In a hot place like a desert; the steel will conduct heat to the foot. Making it impossible to walk because of sweaty, slippery feet. Waterproof and insulated boots solve this problem.
Carbon Toe is a type of Composite Toe. To ensure that they offer the same level of protection – both types are subjected to uniform test conditions for performance specifications. Here is a comparison of the two types of toes.
|Carbon Toe Vs Steel Toe|
|Carbon Toe||Steel Toe|
|Tests:||· ASTM F2412
· Standard Test Methods for Foot Protection
· Impact test
· Compression test
· ASTM F2413
· Standard Specification for Performance Requirements for Protective (Safety) Toe Cap Footwear
|· Meets both standards
· ASTM F2412 Standard
· ASTM F2413 Standard
|Protection:||· Boots carry code to indicate protection offer
· Against compression, impact, and puncture
· Additional protection such as metatarsal protection, static dissipative protection, electrical hazard resistance, and puncture resistance.
· They withstand an impact of 75 foot-pounds
· And compression greater than 2500 pounds.
|· Boots carry a code indicating the protection offered|
|Weather:||· Offer better insulation from the elements due to non-conducting materials||· Boots carry a code indicating the protection offered|
|· Offer better insulation from the elements due to non-conducting materials||· Steel is an excellent conductor of temperature
· May not offer adequate protection in extreme weather
|Security:||· Do not set off the metal detectors at security checks||· Sets off metal detectors|
|Comfort:||· Lighter than steel toes
· Better dexterity and movement
· Less weight means less strain on the ankle and foot joints
· Less fatigue
|· The weight is due to the gauge of steel in the cap
· Making the cap resistant to compression, puncture, and impact
Are carbon or steel toe boots a legal requirement?
Boots with steel or carbon toes are called safety boots. The OSHA mandates federal regulations for protecting personnel. It is mandatory for the personnel to wear them. The employers are expected to provide them. And ensure that the Personnel Protective Equipment (PPE) is worn through the workday.
What is the ASTM Standard for work boots?
The ASTM F2413-18 expects the work footwear to have a protective – steel or carbon -toe cap to be an integral part of the boot. The toe cap should be tested to guard against compression and impact.
How to inspect these boots?
Safety boots carry a code of what protection they offer. Carbon toe boots are non-conduction while steel conducts heat and electricity. These boots should be inspected before every use. Check for wear & tear such as worn treads, torn uppers, cracks, holes, broken buckles, etc. The soles should be checked for metal shards that present a tripping or electrical hazard.
What is the difference between Static Dissipative (SD) and Electrical Hazard (EH) boots?
The EH boots prevent the possibility of electrocution. SD boots ground the build-up of a static charge in a controlled manner. There are eliminating the possibility of a static shock or discharge which may cause a fire.