Delivering gloves manufacturers with a product combining chemical barrier properties without compromising on physical strength and softness still remains a challenge today
Recent years have seen a reduction in the weight of nitrile gloves driven by economics, as raw latex represents up to 70% of the cost of a glove, and end users look for better glove sensitivity and dexterity. However, reduction in glove thickness (which can be as low as 0.055 millimeter) have a negative impact on solvent barrier properties. In this article, the main parameters affecting chemical permeation will be discussed.
Materials and methods
Chemical permeation is a process by which a chemical can pass through a protective film without going through pinholes, pores, or other visible openings.1 Permeation tests were conducted following the EN 374-3 method using a modified gas chromatograph with FID detection fitted with a permeation cell (see photo of permeation cell).
From the permeation curve, breakthrough time and the permeation rate (expressed in µg/cm² per minute) are determined. Resistance of the glove is calculated by the normalized breakthrough time when permeation rate reaches 1 µg/cm² /min (before conducting a permeation test, the physical integrity of the latex film is tested with the selected solvent).
Results and discussion
Influence of film thickness
Permeation of ethanol through films of different thickness (0.061, 0.080 and 0.264 mm) made from Synthomer X2000, a popular grade for thin gloves, was investigated.2 Film thickness was found to be a critical parameter controlling permeation: Ethanol permeates relatively slowly through a 0.264 mm film with a breakthrough time of 55 minutes. On the other hand, it was detected only after one minute with a reduced thickness of 0.061 mm (figure 1). This trend was reported earlier on a study looking at the permeation of metal working fluids through nitrile gloves.3
Influence of monomers composition
Permeation of hexane was conducted on three latex films of different monomer composition and same thickness (0.06 mm). As shown on figure 2, the industrial grade offers superior barrier protection even with a film of 0.06 mm thickness with a breakthrough time of 18 minutes. In the same conditions, thin glove grades provide a protection of only 4 to 7 minutes. This demonstrates the importance of the monomers composition of the latex in barrier properties.
Influence of compounding formulation
Permeation of hexane through films made from X6322 of 0.09 mm thickness was investigated by varying either zinc oxide or sulfur in the compounding formulation. It was found to have a very limited impact on breakthrough time with values varying between 10 and 15 minutes. Increasing zinc oxide did not show much improvement on breakthrough time whereas a high sulfur content gave some benefit when adjusted to 1.5 phr. However, in practice, compounding formulations are not so flexible and therefore are not likely to play an important role in improving barrier properties.
Film thickness and monomers composition are playing an essential role in barrier property functions. Increasing thickness not being an option and as compounding formulation has a limited effect on permeation, solution lies on the latex formulation itself.
However, delivering gloves manufacturers with a product combining chemical barrier properties without compromising on physical strength and softness still remains a challenge today.
1.Ansell 7th Edition Chemical Resistance Guide, 2003, 8p, Ansell Occupational Healthcare.
2.Soeren Butz, Walther, Alexandra Abele. Nitrile latices as complementary addition to NR
Tailoring of NBR film properties with focus on relaxation properties and barrier functions Accelerator free NBR latices, 5th International Rubber Glove Conferences and Exhibitions 2010, Kuala Lumpur, Malaysia
3.Xu, W., Que Hee, S.S. Permeation of a straight oil metalworking fluid through a disposable and a chemically protective nitrile glove. Journal of Hazardous Materials A137, 2006, pp 709–715
Unleashing new initiatives
A pioneer in the development and supply of nitrile latex (NBR), with over 37 years experience in the field, Synthomer took the brave decision to make a major investment in Kluang, Johor, Malaysia, in 2001 realising that NBR glove manufacturing was growing rapidly in South East Asia with more gloves users switching from NR glove to NBR glove due to protein allergy issue in the 90s. This first investment in a nitrile latex plant with an initial capacity of around 44,000 tonnes a year, paid off and rewarded the company afterward with the No.1 global status in nitrile latex business.
This unique achievement was made possible by the company’s decision to work closely with all the existing and potential customers and grow with the customers, very much in tune with the company’s motto “Better Together” which is inscribed in Synthomer’s logo. It is a philosophy that has stayed with Synthomer throughout.
The company has of late come out with a host of new initiatives with a view to further reinforcing its market leadership, tehnological leadership and cost-efficient manufacturing. There has also been a growth in demand from its customers worldwide that requires the company to invest more in capacity expansion.
Apart from an estimated RM250 million already invested in the state-of-the-art nitrile latex manufacturing plant at Pasir Gudang, Johor, Malaysia, which started operation in 2009, Synthomer recently invested another RM110 million in capacity expansion. With this, the nitrile capacity at Pasir Gudang will rise by over 60%. The first batch of latex from the plant will come out in August 2012.
What is even more important, other than strengthening Synthomer’s presence in the fast-growing synthetic nitrile gloves market, this will fulfil the expansion plans of its customers in medical examination and industrial gloves manufacture. Ever committed to supporting the customers’ ambitious development plans, Synthomer has been able to infuse added confidence into them about the supply of high-quality, technically advanced products.
New XSBR plant
Already a global leader in the production of carboxylated SBR (XSBR), Synthomer has now announced plans to expand its expertise in the field to Asia too by setting up an XSBR facility in the region. The plant, also to be located in Pasir Gudang, Johor, will have a capacity of 70,000 tonnes a year and is expected to come on stream in early 2013.
The company has set itself a goal of achieving over 50% of its sales from emerging markets by 2015 with a major focus on Asia. With the setting up of the new XSBR plant, Synthomer’s investment in expanding its Malaysian capacity in both NBR and XSBR latices will exceed RM40 million in 2012 and it will be a major step towards achieving the set goal. With Asia’s coated paper industry growing fast, especially in China, Indonesia and India, Pasir Gudang is the ideal location for raw material supply and outbound logistics and it helps Synthomer to serve its customers throughout the region more effectively.
Following its vision of continuous improvement, Synthomer has installed new Quality Control/Quality Assurance laboratories to ensure the Group’s high quality standards which have become a bench-mark for for the NBR-Business.
High-tech laboratory reactor
Synthomer has recently commissioned a fully automated ultra-modern laboratory reactor at the Global Nitrile Technical Centre in Kluang, Johor, absolutely imitating its main plant reactor. This forms an important part of the Group’s vision of driving innovation throughout the business. The reactor facilitates faster implementation cycles for new products to full production more efficiently.
Maintaining excellent safety and environmental protection practices have ever been a top priority with Synthomer. While the company, without any doubt, regards this is a “natural” measure of global operations, the company today also supports its efforts in this field with a broad range of Corporate Responsibility activities towards the community around their sites.