How Latex Gloves are Manufactured
Posted on 2nd , May 2012
The manufacture of latex gloves has many different stages which must be followed to ensure high quality medical exam grade gloves are produced.
The term medical-grade means that the fabric of the glove will act as a consistently protective barricade which stops the transmission of microorganisms found in blood or other bodily fluids which can infect and cause disease. This includes infections such as Hepatitis B and HIV.
Medical Grade Exam Gloves are regulated for quality under section 21 CFR 800.20 of the United States Food and Drug Administration (FDA). The FDA standards mirror the standards by the Association of Testing Materials (ASTM).
Medical Grade Exam Gloves are strictly tested to pass certain requirements in durability, protection and appearance. Gloves that do not meet the grade are described as general purpose gloves which can have many uses in the home and workplaces, particularly in industries such as beauty and food industries.
Manufacturers of Medical Grade Exam Gloves must also have been given 510k certification. This certification refers to section 510(k) of the FDA Federal Food, Drug and Cosmetics Act and its purpose is to establish if the medical product they wish to manufacture is "substantially equivalent" to an existing product which has already been approved.
The quality of the gloves that are being produced will be dependent on how each stage of the remanufacturing process is implemented by the individual manufacturing plant.
Collecting raw materials
Latex is a natural product that comes from rubber trees so the first stage of making latex gloves is to collect the natural rubber which is the primary ingredient in creating latex gloves. Workers ‘tap’ the Hevea Brasiliensistree
(rubber trees) to collect the milky sap. They do this by cutting a slit on the tree trunk and allow the sap to drop into a container. The trees are generally found in Asia, in countries such as Indonesia, Malaysia, the Philippines and China.
The collection centre
Once collected the liquid sap needs to be treated with chemicals quickly or it hardens into a gum. Once stabilised the latex is centrifuged to remove water, proteins and any impurities in order to create a better quality of latex for production.
Ammonia is added to preserve the sap while it is being delivered to the glove manufacturer’s factory, where it is processed and mixed with other chemicals to make the latex concentrate.
The glove manufacturing factory
The factory must follow Good Manufacturing Practices (GMP) which is a set of standard manufacturing guidelines regulated by the Food and Drug Administration (FDA). They govern the manufacture of medical goods that will be used in United States (where the majority of medical gloves are shipped).
The factory work environment must be completely clean to ensure no dirt gets into the manufacturing process. This is particular true of the ‘formers’ which are the ceramic moulds which create the hand shape of the glove. They are cleaned using an alternating dip of acid and alkaline and then brushed. It is imperative these are clean, or they could introduce tiny holes into the gloves rendering them unusable, so they are regularly inspected and cleaned.
The formers are dipped into a tank containing a 140 degree coagulant latex and calcium nitrate mixture. The mixture will have different ingredients and chemicals depending on the brand of gloves being produced at the time. This stage determines the thickness of the gloves, the thicker they need to be the longer the formers stay in the tank. Once thoroughly and consistently coated the formers are then ‘dripped’ to ensure the surface of the gloves is constant and even. The excess mixture that drips off is restored to the coagulation tank. The gloves then travel through a series of 210-250 degrees ovens to dry.
Once the gloves have dried and solidified the ‘leaching’ process begins. The gloves are moved through a leaching line where the gloves are rinsed of the proteins and residual chemicals using 160 degree fresh circulating water. This is an essential part of the process which is important in determining the quality of the glove, the longer the leaching line the better!
The cuff of the glove is then rolled, The is a process is called ‘beading’ which makes the glove stronger and enable it to be put on (‘donned’) or taken off (‘stripped’) easily and without breaking.
The gloves are then coated in a wet ‘slurry’ powder made from cornstarch. Traditionally latex gloves have a powder called Donning Powder applied to make them easier to put on and also to increases shelf life and stop gloves sticking together. The ASTM D6124 standard specifies acceptable levels of powder for both examination and surgical grade gloves. A powdered glove is more vulnerable and more likely to spread allergens so it is therefore more likely to fail certain quality tests by the FDA. Powdered gloves are becoming increasingly un-popular and are hardly ever used in the healthcare industry now. Even gloves that are not powered will go through this wet powdering stage. Powdering is essential to stop the gloves melting together in the manufacturing process.
A powder-free medical exam glove is basically a powdered glove which has had its powder removed via water rinsing and a chlorine bath.
All gloves will go through additional ovens for further drying and leaching cycles to remove the powder.
The gloves are now ready to be manually removed from the formers by workers, turned inside-out and taken to the final drying stage. Workers can remove approximately 16,000 gloves in an hour.
They are taken to a final drying stage which takes place in large industrial dryers. This process ensures any excess powder is distributed or removed and helps the gloves elasticity.
Now the gloves are complete the quality testing stages begin to ensure compliance with ASTM and FDA standards.
It is not possible to test every single glove; instead a small representative sample of the batch is tested. If this sample does not meet the Acceptable Quality Level or AQL then the whole batch of gloves will be rejected. An AQL of 1.5, for example, requires that there be no more than 15 failures for every 1000 gloves produced. General medical exam gloves have an AQL of 2.5 whilst surgical gloves have an AQL of 1.5.
The gloves are ‘air tested’ to check that once inflated with air no holes are present for the air to escape. Then they are subjected to a ‘water test’ where the gloves are filled with water to check for leaks.
The dimensions of the gloves, including width, length, palm thickness, and finger thickness, are tested. They are also tested for flexibility, strength and elasticity as per ASTM D412 and D573 . All gloves are tested for powder and powder residue, as per ASTM D612.
If the gloves are to be considered sterile they must also be tested using criteria specified by the United States Pharmacopeial Convention (USP).
The gloves are typically packaged into their boxes by hand, by workers wearing protective clothing to prevent contamination. The gloves are placed one on top of the other like tissues in a tissue box (‘layered technique) so they are easy to remove from the box when needed.
The boxes are then packed into larger pallets and shipped to their destination.
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