How did FDA start to get itself involved in the regulation of medical gloves?

Glove Chemist:How did FDA (USA) start to get itself involved in the regulation of medical gloves?

JohnWoon:FDA's initial focus was solely on the regulation of drugs and materials coming into contact with food. But this changed with the introduction of the Medical Device Amendments to the Federal Food, Drug, and Cosmetic (FFD&C) Act in 1976. This allows FDA to extend its regulations to cover the proper use, effectiveness, and safety of all medical devices, including disposable medical gloves and condoms.

Although FDA does not write standards for medical devices, it participates in standard-writing committees. It recognizes guidelines written by other parties such as American Society of Testing and Materials (ASTM), the American Association of Medical Instrumentation (AAMI) and United States Pharmacopoeia (USP). FDA uses the published standards when evaluating medical devices for the marketplace.

FDA's requirement that all medical glove manufacturers shall meet ASTM guideline D5151 for the detection of holes in disposable exam gloves is one good example.

ASTM is a nonprofit organization that meets and writes standards for a wide range of products, services, and materials for the benefits of consumers, manufacturers, government representatives etc. Its guidelines are recognized very widely even outside USA. Since FDA gives a lot of importance to these guidelines, glove manufacturers must conform to these standards to meet FDA requirements for the particular types of medical gloves they sell.

ASTM revises its standards in response to changes in industry and also the consumer and regulatory needs. ASTM publishes annually more than 10,000 standards that are compiled in more than 70 volumes of Annual Book of ASTM Standards.

As far as medical gloves are concerned, ASTM's scientifically designed tests are carried out to accurately assess the quality of the products made from a variety of manufacturing approaches, formulations and raw materials. These include water leak, air inflation, chemical permeation, tensile strength, V-tear Test, trouser tear, puncture resistance, skin irritation and sensitization tests.

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History of Latex Dipped Products

Manufacturer:We're in the process of preparing our brochures for market promotion and we would like to add 3 to 5 lines on the history of medical gloves, condoms and catheters. Your input would be appreciated.

JohnWoon:History is always interesting but the problem is there could be more than one versions. I'd would not like to create undue controversies here. But since you had asked, the followings are my versions:

1) Medical Gloves (Examination and Surgical gloves)
Before 1890s', doctors did not wear gloves. In fact, hands were cleaned only after surgery and not before. This was to remove the resultant messy blood. William Stewart Halsted (1852-1922) was the first surgeon-in- chief of the Johns Hopkins Hospital (established in 1889) who started to don the first pair of surgical gloves. He also pioneered many surgical operations. It all started when Dr. Halsted, working with Goodyear Rubber Company, produced two pairs of rubber gloves to protect his scrub nurse (with whom he was in love) from mercuric chloride solution rather than concern over asepsis problem. However, coincidentally, the incidence of asepsis problem happened to decrease considerably.



Since then he started to popularize the wearing of rubber gloves during surgery in 1890s'. This is well before the advent of the latex technology in 1920s'. Dipping was invariably done by using rubber solution (i.e. masticated rubber dissolved in solvent such as naphtha)

In 1923, the first British Patent was filed for the manufacture of gloves along with other articles using dipping process based on ammonia preserved latex. The curing was done by dipping in cold dilute solution of sulphur monochloride (in Carbon disulphide). As we all know, this was replaced with hot vulcanisation with the incorporation of vulcanising agents. Actually,"vulcanisation" was discovered in 1800s' which laid the foundation for the subsequent growth of the modern rubber industry.

Today, natural rubber layex is the best choice of base polymer for the manufacturing of not only examination gloves and surgical gloves, but also other gloves such as household gloves and electrician gloves (i.e. lineman's gloves).

2) Condoms
Condom which has also been known as sheath, protective, rubber, French letter, skin and prophylactics has a long history which some believe could be traced back to ancient Egypt. The first published document on the use of condom made from linen recorded the trials conducted by an Italian gentleman in 1500's to protect men from diseases.

Condom made from animal intestine besides linen and silk came into the scene in 1700s'. Thanks to the discovery of "vulcanisation" coupled with the advent of the latex technology between 1920s' and 1930s', mass production of condoms using latex was made possible.

Today there are many brands of good and bad condoms in the market which are made to suit every taste, smell, feel and fancy. All these bewildering types of condoms expose the users and their partners to not only the rubber itself but also the curatives (chemicals) used in the rubber.

3) Catheters
The use of urethral catheters to relieve full bladder of patients could be traced back to as early as the days of Hippocrates in Greece as reported by some. Bronze catheters were among the first to be used, followed by other metals such as gold, copper and silver.

Subsequently flexible and more malleable catheters were made from lead for "safer" use. The nineteenth century saw the advent of the first prototype of Foley catheter. However it was in the early 1900s when the first balloon catheter was developed.

Today many types of catheters are being used for the drainage of fluids from the internal organs of the human body, most frequently the bladder.

Urinary catheters are often left in the body for a considerable length of time. Hence it is essential that catheters are manufactured with a natural rubber latex compound which has the least tendency to cause irritation to the human mucous membranes.

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What are the applications of prevulcanised latex ?

Student:You had mentioned the advantages of using prevulcanised latex. Can you please briefly describ the products that are being produced commercially using prevulcanised latex?

JohnWoon:Yes, I've discussed the various advantages of prevulcanised latex (PV) in my earlier posting. Here I would like to just mention again in summary as follows:
1) Simple to use
2) Long shelf life
3) Low residual chemicals
4) Low toxicity
5) Maturation and vulcanization not required
6) Better efficiency in leaching
7) One formulation for all seasons

As regards the possible uses of PV, the list could be quite extensive.The following list shows only some important examples of the applications. I'm also including the the basic requirement, recommended types of prevulcanised latex and choice of manufacturing methods.

1) Medical Gloves and Electrian Gloves
Basic requirements: Good tactility and elasticity, low TypeIV Allergic Reaction.

Types of PV : Medium to high modulus.

Method : Coagulant dipping - Single and Multiple.

2) Catheters
Basic requirement: Low toxicity, good balloon symmetry for Foley catheters, good adhesion between dips.

Types of PV : Medium to high modulus.

Method : Multiple coagulant dipping.

3) Toy Balloons
Basic requirement: Low nitrosamine and low nitrosatables, easy to inflate, low bursting rate during printing, good balloon symmetry and sheen.

Types of PV : Low modulus, low nitrosamine.

Method : Single coagulant dipping.

4) Baby Teats and Soothers/Pacifiers
Basic requirement : Low nitrosamine and low nitrosatables, good clarity, good ageing resistance to boiling.

Types of PV : Medium modulus, low nitrosamine, high clarity.

Method : Single coagulant dipping and heat sensitized dipping.

5) Marking Rings
Basic requirement : High tensile strength, high elasticity, low tension set, good ageing resistance.

Type of PV : Medium to high modulus.

Method : Single coagulant dipping.

6) Condoms
Basic requirement : High bursting pressure and volume, high clarity, low TypeIV Allergic Reaction, low toxicity.

Type of PV : High modulus.

Method : Straight double dipping (i.e. with no coagulant)

7) Breathing Bags and Masks (for administering of anesthetic)
Basic requirement : Good elasticity, low toxicity, good fatigue resistance, good ozone resistance.

Type of PV : Medium to high modulus.

Method : Single or double coagulant dipping.

8) Can Sealants
Basic requirement : Low residual chemicals, low toxicity.

Type of PV : Medium to high modulus.

Method : Casting and injecting.

9) Adhesives
Basic requirement : Quick grab, good cohesion and adhesion strength.

Type of PV : Low to high modulus.

Method : Roller coating and brushing.

10) Flooring
Basic requirement : Good outdoor ageing resistance, good bond strength to rubber crumbs.

Type of PV : Medium to high modulus with excellent adhesion to rubber substrate.

Method : Trowelling.

11) Rubber Sheeting (for garments and exercise bands)
Basic requirement : Good elasticity, soft silky feel, latex compound should be easily heat sensitized.

Type of PV : Low to high modulus with good heat sensitizing property.

Method : Coagulant dipping or continuous heat sensitizing casting.


Conclusion

Although both prevulcanised latex and post-vulcanisable latex compound are widely used for the manufacturing of a variety of latex products, the former offers many manufacturers a ready-to-use latex compound with ease of processing which requires simpler process controls with added comparative advantages of low toxicity and long shelf life. As a result, prevulcanised latex has been very popular for the manufacturing of medical devices such as medical gloves, condoms, catheters, baby teats and pacifiers.

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Do we need new regulations for food contact nanomaterials?

Manufacturer:We understand that some polymer packaging materials for food are incorporated with nano-sized additives. Are these new products really safe? What about food handling gloves with similar additives? Are existing regulations adequate to control these materials?

JohnWoon:Everybody knows that nanomaterials industry is fast-growing and is currently working mostly within the scope of existing national regulations. We also know that such regulations have been developed for traditional materials and not nanomaterials.

Despite chemical similarity, nanoparticles could behave quite differently from their regular counterparts due to their very small size, for instance, nano-sized Zinc oxide is expected to behave differently from the normal Zinc oxide i.e. they must therefore be classified as new materials and treated as such.

In short, many experts believe that the existing national or international standards and regulations might not be adequate to control the new materials.

I understand that the UK government is in the process of testing PET bottles and other packaging materials incorporated with nanoclay to improve the impact resistance or nano-sized antibacterial silver particle to prevent and control bacterial growth.

Some of the tests include the assessing of the migrating behavior of these additives and the determination of how leachable they are. I hope they are also studying the toxicity aspect as well.

Critics of nanotechnology are expressing the potential toxicity of these nanosubstances that could adversely affect the stability of cell membranes or disturb the immune system when inhaled, digested or absorbed through the skin. The concern is that by being reduced to the nano-scale, materials become more reactive and therefore potentially more toxic.

The same argument should be applicable to similarly compounded latex products coming in contact with food such as food handling gloves.

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Influence of degree of crosslinking on rubber properties

Manufacturer:You explained the action of vulcanisation earlier but no mention was made about the physical properties of the rubber after vulcanisation. Can this be included?

JohnWoon: Please see the Table at the side bar on the right hand side. This is a good general guide... bearing in mind that some of the properties could be influenced by the level and types of fillers used.

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Can you wet a water repelling polyolefin like Polypropylene?

It is a well known fact that Polyolefins such as PP and PE have excellent hydrophobic characteristic making them difficult to wet since they tend to repel water. While this is advantageous in many applications, it makes them unsuitable for some fiber/nonwoven applications, where properties like aqueous absorption and wettability are required.

A hydrophylic effect can be achieved through the application of topical hydrophilic treatments by spraying or wiping with surfactants. While these treatments achieve an initial hydrophilic effect, they are not durable because the coating could be easily washed away. Application such as wipes must rely on the absorptive capacity of the fibers to hold water.

A hydrophilic internal additive for polyolefin fibers and nonwovens is available from Ciba. It is a melt-processable alternative to topical finishes and allows polypropylene fabrics to absorb many times their weight in water. In addition the additive also improves the soft feel and comfort of nonwoven fabrics.

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Are they that mad to deliberately introduce air into their latex?

Manufacturer: We heard that some latex producers and latex products manufacturers are deliberately bubbling air into their latex. How could anybody be that crazy and stupid?

JohnWoon: This is a very interesting question and I'm glad that you've raised it! But I can assure you that these producers and manufacturers are neither crazy nor stupid. In fact they're smart enough to know exactly what they're doing. Technically, there are good reasons for doing so as far as the mechanical stability of the latex is concerned.

Note to other visitors and readers: The details of this answer are not revealed at this site. If you're interested to know more, please fill up the form below with your e-mail address and I would contact you privately.

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Rubber compound for Guitar "Capo"

Manufacturer: Shall I use plasticised PVC or rubber for the lining of guitar capo?
JohnWoon: Guitar capo lining must be soft enough so that it does not damage the guitar strings especially the nylon ones used for classical Spanish guitars. Also, it should not affect the polymer coating which is sometimes used on metal strings. At the same time it must have low compression set for it to exert a consistent pressure on the strings between the frets of the guitar.

I would prefer to use an NR based compound to a PVC mix since the latter has poor set property while the former could be compounded with very low compression set using EV curing system. The rubber strip could be compression moulded or injection moulded. Casting or dippng from a latex compound is also a possibility.



Note: For those who do not know what a capo is, it is a clamp that you stick on different frets of the guitar to change the pitch or key of the open strings. Each fret on the guitar is a half step, therefore, if you put a capo on the 1st fret, all of the open strings will sound a half step higher than normal. This makes changing the key of a song very easy. Some times I come across songs having really weird chords that I don't want to really struggle with. With a capo, I can change the key or pitch of my guitar and make those tough chords very much easier to play.

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