Gloves made from natural latex exhibit rubbery characteristics when vulcanised. Natural latex is essentially cis-1,4 polyisoprene that is harvested from Hevea Brasiliensis rubber trees in the form of a stable emulsion. This emulsion is stabilized naturally with certain proteins, some of which are removed during the glove manufacturing process. The proteins that remain in natural latex gloves can result in Type I allergic reactions in those persons who have become sensitised to the natural latex proteins. The dip-moulding process for making gloves was designed around natural latex and is still used today for not only making natural rubber latex gloves, but also synthetic gloves such as nitrile and polychloroprene.
The properties of natural latex can vary slightly through compounding changes, but the over-arching characteristics of natural latex gloves are fixed because the polymer structure is always the same. This fixed polymer structure delivers several important and advantageous properties, but limits being able to engineer or design specific performance properties like with synthetic polymers.
Natural latex gloves exhibit excellent softness, high tensile strength and very good barrier performance to viruses and blood borne pathogens. These properties make natural latex gloves the product of choice for medical exam and surgical gloves.
However, natural latex gloves have poor oil, fat and hydrocarbon resistance compared to some synthetic alternatives. For certain applications, natural latex gloves may not be suitable. In applications were oil, fat and hydrocarbon exposure may occur over an extended period of time, an alternative glove type may be a better choice.
In addition, natural latex gloves typically contain natural latex proteins. Glove users and those coming into contact with natural latex products may become sensitised to the natural latex proteins, and develop a Type I allergic reaction to natural latex products. The symptoms of this type of allergic response can range from skin irritation to life-threatening anaphylactic reactions.
Natural latex gloves are very soft and flexible resulting in a comfortable glove with good tactile sensitivity for the glove user. When stretched, natural rubber will strain-crystallize, which means it will actually develop increased strength as it is stretched. This property also contributes to the natural latex glove property of full recovery after being stretched (full elasticity). Full recovery can result in hand stress and fatigue when natural latex gloves are worn over a long period of time. Unlike natural latex gloves, some synthetic gloves made of nitrile exhibit a property called stress relaxation. When wearing a glove that exhibits stress relaxation, after the glove is placed on the hand, the film will tend to relax, conforming to the size and shape of the hand. This results in a very comfortable fit. The synthetic glove can be worn for an extended period of time with little stress on the hand and low fatigue. This is an important feature in applications where the glove is worn for longer periods of time such as dental and clean room environments.
There is another difference between natural latex and synthetic polymers; natural rubber is a linear polymer and hence has to undergo a pre-curing step to enhance its strength before dipping and forming a glove. Synthetic latex such as nitrile is inherently cross-linked during manufacture so that little or no pre-curing is necessary to enhance its strength. This can be a process advantage for synthetic polymers.
From an environmental perspective, natural latex is free of nonyl phenol ethoxylate (NPE) surfactants known to contribute to toxicological issues in water and wastewater streams. Natural latex gloves also contain no plasticiser as with PVC gloves, which can migrate from gloves into food or other items being handled when wearing PVC gloves.
Natural latex is environmental friendly, it is biodegradable.