The latex doctorHarry F. Bader

On creasing, testingtensile strength, thelatex ‘mystery’,and adhesives...

I am a production executiveat a glove factory in Malaysia.We’ve been facing some quality issues lately. Some of ournitrile gloves become creased!crinkled after they are produced while others do not. Thisis particularly the caseof chlorinated gloves and is normallyfound when the glove is beinghot-tumbled. Could you pleasetell us what the possiblecauses,physical and chemical, for suchcreasingare?

W.Y. LeeRiversideResourcesSdn.B/rd.

C reasesafter hot tumblingareusually dueto glovesbe

ing removed from the tumblerwhile still hot. The creasesoccuras thegloves cool in the tote boxor hamper.This is more of a problem with nitrile gloves. Turn offthe heatabout 10-15 minutesbefore removingtheglovesfrom thetumbler.

Another possible causeis thatthe tumblerbasketis revolving toofast. This causestheglovesto holdto thesideof thebasket,developing creases.Whenthis occursyouusually see signs of abrasiononthecreases.If that is thecase,slowthe rotationof thetumbler25 rpmis usually aboutright.

A third causecould be thatthetumbler temperatureis too hot.Chlorinated gloves should notexperiencemore thanJl afterchlorination.

c-LI-ta

Resultsof creasesare: I Poorappearanceandpoorcustomeracceptance,2 Easyozoneattackatthe stressedcrease,which willaffect the shelf-life.

S..

Currently, our clients needsomeguidancein testing tensilestrength and elongation ofgloves after oil dipping coating. Would you mind offeringyour professionaltechnologytoreleasethe testing methodseither from ASTM or otherstandards?Pleasedescribetesting methodsin detail?

Andrew Chen,SalesManager

SheenMoreEnterprise Co. Ltd.

T estingphysicalpropertiesofnitrile gloves would be ac

cording to methods in ASTM D412 and to the specifications inASTM D 6319. Essentially,whatis done is thatphysicalpropertiesarecheckedbefore andafter exposureto the oil. The resultsarecomparedwith thestandardminimum requirement.This is according to ASTM D 471. Anothermethod of evaluation is to measure the permeationof the glovematerialby theoil, using ASTMF 739.

I’m sorry, dueto copyrightlawscannotsenda copyof thesestand

ardsandspecifications.All areintheASTM StandardsBooks, and

RubberAsia September - October 2001

Harry F. Bader,Vice-President,LatexServices,AkronRubberDevelopmentLaboratory, Akron,USA, and a worldauthority on latex,answersquestionsanddoubtsof readerson latexand latexproducts.

Send your questions to:

‘The Latex Doctor’Rubber Asia,Dhanarn House,Cochin - 682 020,Kerala, IndiaFax: 94-484-317372

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should be available in a university library or a large city publiclibrary.

.5.

I am sending one sample ofsponge foam rubber the basicraw material of which is a mystery to me. it appears as synthetic latex, but I am unable todecide whether it is neoprenelatex or polyisoprene lattices. Ishall be grateful to you if youcould enlighten me on the rawmaterial used, its source ofavailability and the process applied.

Ram Ji SethRag/wv Udhyog,F-JO Pahnki

SiteII, IndustrialArea, Kanpur

T he foamsamplesweresubjectedto ‘a simple flame test.

Natural rubber will supportcombustionandwill tend to meltas it bums. Neoprenewill not support combustion.It will go out ifnot continuously in contactwith aflame source. SBR will supportcombustion,but it doesnot burnaggressivelyandit chars.

It is my opinion that the polymer of your foam rubber sampleis mainly, if not totally, SBR rubber. To obtain a more preciseanalysis,an FTIR PolymerIdentification would be required.

5S

Is there any cost-effectiveelastomer/TPE, natural or synthetic, excluding silicones andplasticisedPVC, that can givetransparent, colourless andcrystal-clear moulded rUbbercomponents food grade likethe nipples?

is bleached natural rubberlatex available anywhere?Which is the best source, preferably Indian, for completetechnologyof dip/compression/inj. moulded rubber components food grade? Who are thedip-moulding pattern suppliershere? What are the latex adhesivesfood grade available tostick such moulded components to plastic wares/toysPVC/PET/PC?

Can such rubber componentsbe welded to plastics? Can you

explain the latest proceduresadopted for rnicrofine halepiercing, asin pacifiers, etc. forlarge volumes?

S. Chandrasekhar

W henyou add "cost- effective" to your question,you

make it muchmore complicated.‘What is cost effective for surgeon’ s glovesor for infantacifiers is not "cost-effective"for examgloves.

It is difficult to keepup with newtechnology. I suggestyou contactsupplierswho advertisein RubberAsia to get information on newlatex polymerswhich canbeusedto make "clear" products.Contactthe Indian Rubber Board forsourcesof rubbertechnology.

For a referenceon latex technology, I recommendHigh Polymer Lattices by D.D Blackley1966, Mac Laren & SonsLtd..London, Palmerton PublishingCompany Inc., - New York,printed by the GardenCity PressLtd., Letchworth,Hertt’ordshire,UK, and PolymerLattices byD.C. Blackley 1997, Chapinan&Hall India, R. Seshadri,32, Second Main Road, CIT East, Madras 600 035 India. Both shouldbein eitheryour university libraryor acity tibrary.

The best source of adhesivesinformation is the manufacturersthemselves.If you explain whatyou want to adhere,they will recommendtheadhesiveandgive yousamplesto fly.

I am told that rubber films arebeing"welded to plastics". I understandthis is possibleonly withvery stringentquality andprocesscontrols. Also, bothmaterialcostsandequipmentcostsarehigh. Thisinformation is abouta year old,so there may be improvementsavailable.As with most things, thelatestinformation shouldbeavailable from the equipmentsuppliers.

The latesthole cutting techniquefor pacifiersis automatedlasercutting.

The latex will remainstable ifkeptcool during storageandin thedip tank. During dipping, the latex must be kept circulating toensureonly the latex touchingthehot forms coagulates.

RubberAsia S September - October 2001 61.