Wool has been the go-to fiber for cold protection during winters since ancient times. Gloves help the most crucial motor organ, which is the hand and the palms and fingers to not only function smoothly in the most hostile working environments, but more importantly, gloves must be treated as a crucial safety garment.
glove applications
Winter gloves have heavy applications in the temperate regions of the earth. However, in industries, these gloves have applications like fisheries, cold storage, laboratories, the meat industry, etc. where there is a constant need for immersing the hand in a sub-zero environment.
Addressing the frostbite
Numbness followed by frostbite and constant exposure would result in gangrene followed by hypothermia
Excessive exposure to cold weather can cause frostbite followed by frostbite on fingers. Numbness followed by frostbite and constant exposure would result in gangrene followed by hypothermia.
If the frostbite isn’t addressed, it might result in death or amputation of the organ.
Insulation
The feeling of coldness or hotness is nothing but the transfer of heat either from the environment to the body or from the body to the environment. This happens through the process of conduction and majorly through convection. So the flow of heat can be stopped we can prevent the loss of heat from the body.
Thermos and woolen cloths are examples of the same. Air we know is a bad conductor of heat. However, air facilitates the loss of heat through convection. Amazingly, air pockets on the other hand prevent the flow of heat through convection.
A double-sided window pane or a thermos or for that matter, wool or acrylic. The common thing between all of them is the presence of air pockets.
Wool vs Acrylic vs Polyester
With acrylic, the spinning method has a significant effect on the structure of PAN fibers
Much like human hair (so as for sheep hair), wool is protein fiber bundles that can be spun into yarns and hence be woven into fabrics. The key to thermal insulation is to create pockets of “still air”. The irregular structure of the wool fiber helps in making the yarns crimp which facilitates the creation of air pockets.
With acrylic, the spinning method has a significant effect on the structure of PAN fibers. Fibers produced by the wet method are very porous containing a large number of microvoids of 0.1–1 μm in size and characterized by a low density between 0.4 and 0.5 g/cm3.
The density of the dry-spun fibers, ranging from 0.8 to 1.17 g/cm3, is close to the density of the polymer itself which is 1.17 g/cm3. [MOD04]
Physical preparation of acrylic fiber:
- Tenacity: Dry= 5gm/den, wet= 4.8gm/den.
- Elongation: Dry=16%, Wet= 17%.
- Moisture regain: 1-2%.
- Flammability: More flammable, burns rapidly with bright yellow flames.
- Abrasion resistance: Good.
- Dimensional stability: Good.
- Colour: Dull.
- Diameter: 15μm to 25µm.
Feel
Since acrylic doesn’t pill as much as wool, acrylic can be “raised” or “brushed” to give a soft feel
It might always be a dilemma as to which fiber to go for when we have to select winter gloves for industrial wear. Industrial workwear is mostly accompanied by Nitrile Coating on top of the liner to provide the glove with a substantial grip. The chemical formulation can be represented as NBR (Nitrile Butadiene Rubber).
Since wool absorbs much more moisture than Acrylic, the comparison of wool and acrylic in humid conditions can be tricky. Acrylic and Polyfil have also been a recent pick because of their vegan nature and categorized as a product that don’t come from animals. Since acrylic doesn’t pill as much as wool, acrylic can be “raised” or “brushed” to give a soft feel.
Polyfill
Research reveals the effectiveness of synthetic insulating materials for protection against cold.
Polyester wadding/batting popularly termed Polyfil is the first choice for protective garments to be used in extremely cold conditions for example glaciers and extremely high altitudes. The selection of material is based on:
- Minimizing heat loss from the body to the environment, so that the metabolic heat generated from the body is not lost to the environment).
- Simultaneously, the material should allow evaporation of sweat from the body to the environment. Sweat gets accumulated on the skin and in extreme cold conditions, the sweat gets frozen and can cause frostbite. [PRA21]
ASTM D 1518 – TOG Value
TOG rating or tog value refers to the thermal insulation offered by a garment or piece of cloth
Derived from the old Roman “toga” which means garment, TOG rating or tog value refers to the thermal insulation offered by a garment or piece of cloth.
TOG value is considered a standard measure of thermal rating in the US market as the TOG value is defined in the standard ASTM D 1518. The TOG value is calculated as follows:
Here, Mallcom has to introduce a unit of measurement called RSI; where 1 RSI = temperature difference (in oC or K) between two surfaces with 1-watt heat flowing through 1 m2 area of the same during 30 min.
- Unit of RSI = m2.K/W
- TOG value = 10 RSI; So 1 TOG = 0.1 RSI
- Acrylic gloves range between about 3 to 4 TOG value
Air resistant
Wind-resistant and wind-proof properties of a fabric can be determined by the air permeability under a prescribed air pressure differential between the two surfaces of a material.
The airflow rate passing perpendicularly through a given area of fabric is measured at a given pressure difference across the fabric test area over a given period. The applicable methods include:
- ASTM D737
- ISO 9237
- GB/T 5453
- CNS 5612
- JIS L1096 8.26.1.A
- KS K 570
Air resistance
To prevent the flow of air and water, windproof membranes can be added
Air resistance is a key feature in temperate region weather where the real feel temperature drops significantly due to the flow of chilling air.
To prevent the flow of air and water, windproof membranes can be added along with fleece and needle-punched non-woven fabrics in the inner lining of the glove.
Water repellent vs Breathable
Perhaps a topic which deserves an article of itself. Let’s get to the basics of the theme. The smallest water droplet is in a range of 700 µ – 1000 µ (1 µ = 10-6 m). The largest vapour molecule on the other hand is in the range of 50-100 µ. This gives us a window of around 102m to make a fabric that would not allow water to enter and at the same time allow sweat vapor to exit.
For a winter glove to be breathable is all the more important as freezing up accumulated sweat on the palm causing frostbites is not desirable. At the same time, a blanket of still air between the hand and the atmosphere is extremely desirous to create thermal insulation.
EN511:2006
The European standard for gloves protection from cold is marked by EN 511 (EN stands for European Norm). This standard measures how well the glove can withstand both convective cold and contact cold. In addition, water permeation is tested after 30 minutes.
- The first figure shows how well the glove protects against convective cold (performance level 0-4)
- The second figure shows how well the glove protects against contact cold (performance level 0-4)
- The third figure shows the glove protection against water penetration (performance 0 or 1 where 0 indicates “water penetration after 30 minutes” and 1 indicates “no water penetration after 30 minutes”).
Nitrile Dipping
Acrylic winter gloves are raised from the inside to give a soft touch and coated with nitrile butadiene rubber (NRL) with/without foamy finish and with/without sandy finish on the top.
The nitrile coating not only imparts chemical resistance properties like hazardous substances and toxic chemicals but also plays a major role in imparting physical properties like slip resistance, abrasion resistance, cut and tear resistance, and puncture resistance.