Gloves made from synthetic polyisoprene exhibit rubber-like characteristics when vulcanised, very similar to Natural Rubber Latex (hereafter NRL). Synthetic polyisoprene latex is a mixture of cis-1,4 and trans-1,4 polyisoprene that can be made into an emulsion to be used in the glove dipping process. Unlike natural latex (cis-1,4 polyisoprene), synthetic polyisoprene is stabilized with surfactant and does not contain natural latex proteins. Synthetic polyisoprene will not result in Type I allergic reactions in those persons who have become sensitised to the natural latex proteins.
The properties of synthetic polyisoprene latex can be varied through modifications in the reaction process for making synthetic polyisoprene. These changes control how much cis- and trans- isomers are formed during the reaction process, which in turn may affect the performance properties of this polymer. Even though synthetic polyisoprene comes close to natural latex in its structure and makes a glove that is very soft, it does not match the tensile strength of natural latex.
Synthetic polyisoprene latex gloves exhibit excellent softness, reasonable tensile strength (depending on the polymer composition) and very good barrier performance to viruses and blood borne pathogens. These properties make synthetic polyisoprene latex gloves a good choice for medical surgical gloves.
Synthetic polyisoprene gloves have poor oil, fat and hydrocarbon resistance compared to some synthetic alternatives. For certain applications polyisoprene 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.
Synthetic polyisoprene latex does not contain NRL proteins like NRL. Glove users have no need to be concerned about becoming sensitised to NRL proteins or developing a Type I allergic reaction.
Synthetic polyisoprene gloves are very soft and flexible resulting in a comfortable glove with good tactile sensitivity for the glove user. Polyisoprene gloves have many characteristics similar to NRL because it is essentially a synthetic version of NRL. Polyisoprene gloves exhibit full recovery after being stretched (full elasticity). Full recovery can result in hand stress and fatigue when polyisoprene gloves are worn over a long period of time. Unlike polyisoprene and NRL gloves, some synthetic gloves made of nitrile exhibits 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. These synthetic gloves 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 a longer periods of time such as dental and clean room environments.
Polyisoprene latex, like NRL, is a linear polymer and hence has to undergo a pre-curing step to enhance its strength before dipping and forming a glove. Synthetic latexes 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 these synthetic polymers.
Some polyisoprene latexes are very stable due to the process requirements used to make the emulsion. This high degree of stability can make it difficult to use polyisoprene in a conventional mould-dipped process. Formulation and process modifications are typically needed to be able to process polyisoprene on natural or nitrile glove dipping equipment.
From an environmental perspective, polyisoprene latex is free of nonyl phenol ethoxylate (NPE) surfactants known to contribute to toxicological issues in water and wastewater streams. Polyisoprene 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. No CN or chlorinated compounds should be produced during the incineration of polyisoprene latex gloves because it contains no acrylonitrile or chlorinated compounds (like nitrile and PVC gloves, respectively).