Engineered Protection: Composite materials for Cut and Puncture Gloves

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In the Post “Cut and Puncture Resistant Fibers For Gloves (Pick the Right Fibers)” we covered the most common fibers used in cut and puncture gloves. While this review of fiber types is useful you cant select gloves based on fiber type alone. Most advanced protective materials are composite textiles and are made from multiple fiber types and combine other non-fiber materials.

Textile Types 

Knits: The fastest growing glove textile is the knit. This is driven by automated glove knitting machines which allow us to manufacture the basic glove knit shell with low labor content.  Knits have some great advantages for gloves, jersey knit textile has 2 way stretch and stretch is a significant advantage for glove sizing, comfort and dexterity.  Like most things in life knits and stretch come with a down side. The more open the knit and the more stretch the lower the protection will be for both cut and puncture.  Thin comfortable knits with stretch don’t have high fiber content per unit area. This fiber content per unit area is a simple idea for optimizing cut.  the more of a given fiber type your have under the cutting edge the better the cut performance will be.  With regard to puncture this is pretty clear, an open stretchy knit is not a very effective barrier to puncture.  Even large EN388 penetrators just push the knit fiber out of the way and slide right through the knit materials.  Smaller ASTM nail type penetrators and hypodermic needles penetrate knits with no resistance.

Wovens: Many gloves are made from woven textiles,  however wovens don’t have stretch so a glove made from all wovens has to be very carefully designed and sewn to fit well.  Wovens may not be as easy to use a knits but  they are standouts for cut and puncture performance. The weaving process can product a very dense textile with high fiber content per unit area so you get really high cut performance from well designed wovens. Even better we can engineer weaves that have no sliding yarns so these weaves have high puncture resistance even to the smallest 28 gauge hypo needles.

Coating-Knit-Woven Composites 

In the TurtleSkin line we have found that the best marriage for gloves that are both comfortable and protective is to use a composite or laminate of both knits and wovens. We put the high protection wovens in the area where the risks are on the hand. Then in the areas that are not at risk  we use the stretch and openness of the knit to keep the glove comfortable.  This is an important concept in glove selection. Don’t over spec your protection area. If you ask for 100% protection when you don’t really need this much you will end up with a glove that is both more expensive and less comfortable. If you are not getting injuries on the back of the hand then don’t spec in high protection in this area.

The glove design process does not stop with the combination of multiple types of textiles, coatings play a large role. The mechanical strength for cut and puncture resistance is provided by the textile. Grip and abrasion resistance can be greatly improved with a well engineered coating. Soft polyurethane rubber coatings offer some of the best grip and wear performance around.  In addition to grip coatings provide an opportunity to improve cut and puncture resistance.  The coatings can include hard materials and can be engineered to increase the internal friction in the textile so the cut and puncture are improved. Just as in the case of the use of wovens, coatings reduce the stretch and dexterity in the glove so don’t over spec your coating area. Palm and finger tip coating is a great compromise.

Summary

  1. Knits are very important to comfortable gloves because of their stretch.
  2. Look for wovens for improved Cut and Puncture protection
  3. Look at the coating materials: Do they have enough grip and durability

 

© 2014 Warwick Mills Inc. All rights reserved.

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Cut and Puncture Resistant Fibers For Gloves (Pick the Right Fibers)

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A very common mistake in glove selection is picking the wrong fiber type. As you will find from the descriptions below fibers are not all created equal.

When you are looking for protection and make glove purchasing decisions in  addition to the summary information on fibers listed below the assembled textile and coating must be considered.

Talk a look at a separate post: “The  Puncture and Cut Resistant Textiles and Composites”

Polyester

This material is perhaps the most widely used synthetic fiber. Low in cost and available in may sizes and types. Moderate tensile strength and low cut performance limit the protection from this material used  alone.  Polyester yarn in its textured form has quite good abrasion for its price point.  Chemical resistance is broad, however polyester is a moderate temperature fiber with a burn and drip risk. This material is useful as a blending fiber for controlling the cost of a composite yarn.

Nylon

Nylon is the second most widely use synthetic fiber. Nylon has  moderate tensile strength and low cut.  Nylon has really standout abrasion resistance and this makes it very useful in gloves. The military has used nylon in combination with cotton for BDUs and other garments for many years.   Like polyester, nylon is an excellent choice for glove components, it is  slightly more expensive than polyester but higher in durability. Nylon has moderate temperature resistance and a burn and drip risk if used by itself. Chemical resistance is lower than polyester.

Para-Aramid

This is the old stand Kevlar, Twaron, and Technora this fiber is aromatic nylon. The fiber is strong but small filament size limits it performance for light knit gloves.  The high tensile strength with  small filaments make this a better puncture material than a cut product.  For cut level 4 and 5 gloves we need high density knit fiber cover. These high cover knits are bulky and not very comfortable.  For the Para-Aramid TurtleSkin product there is enough fiber density to provide both cut and puncture. One side benefit of the Para-aramids is they are high temp materials and have excellent flame performance. On the down side Para-Aramids have iffy chemical performance, acids and chlorine bleach are big trouble for these materials.  One last caution, Para-Aramid fibers are not good in abrasion, gloves made from these fibers should have a coating or a cover glove.

Ultra High Molecular Weight Polyethylene UHMWPE

UHMWPE is Spectra and Dyneema fiber significantly stronger than the Para-aramids. They are also small filament yarns with the exception of the new Dyneema Diamond fiber.  Good cut performance and excellent chemical resistance to most common compounds. On the down side these materials can only handle about 220F and start to fail at just slightly higher temperatures. Because UHMWPE is polyethylene it is very low friction. This makes UHMWPE a poor choice for puncture resistance.  In addition UHMWPE will burn and has a bad melt drip issue so all around not a good high temp material.

Liquid Crystal Polyester

The LCP or Vectran material has tensile strength between UHMWPE and Para-Aramid.  LCP is a large denier per filament fiber and has very good cut. Because LCP is Aromatic Polyester it is also a high temp fiber.  LCP fiber is resistant to most industrial chemistry and has some flame resistance. LCP is better all around in abrasion than either Para-Aramid or UHMWPE.  Bear in mid that abrasion and durability in gloves is a complex topic and this review is a summary.   The combination of large filament, tensile, chem resistance, high temp, and abrasion make Vectran a strong competitor. Great combination performance in cut and puncture applications

Fiberglass

Fiberglass is just glass, and as you would expect it is fragile.  Fiberglass does not do well in abrasion or in flex, the damaged surface of fiber glass yarn has sharp ends of broken filament exposed and this shape filament can cause skin irritation.  However fiberglass is very hard when compared to all the organic fibers we have talked about, fiber glass is harder than most cutting tools. The glass fiber breaks down the cutting edge of the threat and and gives good cut resistance.  As long as the fiberglass has a protective cover of one of the other fibers on the list it is a tough high cut fiber. Not a surprise that fiberglass has great thermal resistance and will not burn. Chem resistance is uneven.

Stainless Steel

Like fiberglass stainless steel fiber is a specialty item that is used in combination with one of the other fibers. This fiber has all the properties of steel, hardness, toughness and stiffness. Good thermal and chemical resistance, however as this material is used in a blend these properties are only as useful and the total performance of the blended yarn. To address the stiffness of steel these fibers a low denier per filament and this limits the performance to some degree. The exception is ring mail gloves that over come the stiffness issue with a special welded fabrication process.

 

© 2014 Warwick Mills Inc. All rights reserved.

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The Knit Needs to Work with the Dip (Basics of Dipped Knit Gloves)

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Knit Glove Basics

Knit gloves are made on knitting machines with a limited range of needle density. Thick gloves made from large yarns are generally knit on machines of 8-10 gauge (8-10 needles per inch). These yarns are the same size you find in winter coats. The larger yarns require the larger needle spacing.  Many high cut level gloves  (level 4-5)  use these large yarns and 8-10 gauge knits. For finer and thinner knit gloves the most common knitting style is 13 needles per inch. The 13-gauge knits often use small yarns such as 210 denier nylon. This is about the size of the yarn you use in an oxford shirt.

Openness in Knit Fabric

The knitting machine gauge and the yarn size controls how open the glove textile will be. As an example,  for 13-gauge knits using our 210 denier yarn there is perhaps 30-40% open area in the textile. The % openness in the knit affects how the glove feels and how much stretch it will have. Most users would agree that more open knits result in cooler more comfortable and dexterous gloves.  The down side of more open knits is that it is much harder to create high cut level gloves with small yarns with open space. (More on this in another post.)

The Knit Needs to Work with the Dip

Most users like the grip and durability that palm coated knit gloves offer.   Knit gloves with high levels of openness have an additional benefit for dipping and coating.  With high open area the dip coating can penetrate the textile and encapsulate the yarn on the palm of the glove.  The dip can by nitrile,  polyurethane or NR latex. When the dip can penetrate the knit the coating has the best possible attachment to the textile.  We all want our gloves to be durable and comfortable.  For comfortable gloves with good dexterity the coating and the knit must be thin, no more than 2-4mm in thickness total.  For this type of thin coating layer to be durable it must be well supported by the textile. The rubber in the coating does not have good tear strength. The yarn in the glove provides the reinforcement to prevent premature failure of the coating layer.

When the knit works with the dip you can build a thin comfortable durable glove.

© 2014 Warwick Mills Inc. All rights reserved.

 

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