The latex doctor[1rY F Bader

Magnesiumcontent in latexPinholes in gloves

J ayour professionalopinioncan you advisehow flavours andpigments additives

affect the mechanical/physicalpropertiesof condoms?

We alreadyhave testedsomeof our coloured/flavouredcondoms for biocompatihilitytestsby NamSA, mc, and weare now facing this question.Throughmanyyearsof ourproduction experience,thesematerials do not critically affect thequality of condoms. We wereaskedto establishaprofessionalopinion, andthat is why we areseekingyour expertise.

GeneralManagerDongicuk TechnoRubber

Malaysia.

I havenot heardof either mechanical or physical propertyproblems with the addition offlavours, pigmentscolourants,or fragrancesto the latex compoundsusedfor condoms.Therehavebeensomebiocompatibilityproblems. However, T have nospecific information.

About two years ago, I did acolourantevaluationprojectfor amajorU.S. toy balloon manufacturer. Much to my surprise, wefoundthatvulcanizationtimesandtemperatureshad to be changedto get good physical propertieswhen balloons with somecolourantswerebeingproduced.In all cases,good physicalpropertieswereobtainedby makingthechanges.

I don’t believe that would be aproblem with condomsbecausethe colour intensity would be

much less. With balloons, thecolour mustbe retainedafter theballoon is inflated. The quantityof colourantis high comparedwiththatusedto produce condom tints.

W e arehaving theclassic debate aboutthe differences be

tweenThai andMalaysian latices with one of our customers.The point of contention is themagnesiumcontentandtheaddition of TMTD:

* How would an Mg contentof,say, 30 ppm on TSC affect acompoundfor surgicalgloves?

* Would that compound begreatlyaffectedif, say,theMgcontentwas Sppm on TSC?

* What is current legislation bytheUS FDA regardingTMTDcontentin laticesused for exams and surgicalgloves?

* What developmentsdo you expectto see regardingthis legislation in the future?

* Our customerfinds that theyhave absolutely no problemwith Thai origin LATZ latices,but with HA latexthey areexperiencing small, rough lumps on their gloves. Any ideahow thatmight be corrected?We requestyou to shedsomelight on the matter.

GeneralManagerMetalco Co. Ltd.

Thailand

Answer in the same order asquestionsreceived.

* A 30 ppm magnesiumcontentwould likely reduceboththeme-

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Mr. Harry F.Bader, Vice-President,LatexServices,AkronRubberDevelopmentLaboratory inAkron, USA,and a worldauthority onlatex, answersquestionsand doubtsofreaderson latexand latexproducts.

Sendyour questions to:

‘The Latex Doctor’Rubber Asia,Dhanam House,Cochin - 682 -020,Kerala, India Fax: 94-484-317872 I.

RubberAsla U September- October1999 77

chanicalandchemical stabilityof a latex compound.

* 5 ppm of Mg in a compoundshould not beaproblem.

* TMTD as an acceleratormustbe 1.5% or lessasa % of latexcompound. However, residualacceleratorsmustbemuchless.Actual allowableamountwill beknown in may be six months.The allowable amount willlikely bein the50 Rg/dm2range.

* Protein limits, powder limits,andresidualacceleratorlimits,will likely be regulatedby theendof 1999 Theremaybemorethan one limit for eachof thethree. A changein the amountofallowableTMTD in thecompoundis not likely.

* You did not explain the natureof the lumps. However, if theyare bits of coaguiwn, they areprobably due to low mechanicat andchemical stability - ExcessMg couldbethe reason.Asyou areaware,phosphatestabilizers will reducethecoagulumproblem. Also, excessivemixing time shouldbe avoided.

p leasebe advisedthatwearea glovesnianufacturing company.Attached,

pleasefind the formulations ofnitrile latex compoundingandcoagulantmixing, respectively,that arecurrently beingused.

Basedon the aforementionedformulations, pleasegive somecommentson them in order toupgradethequality ofour product, aswe recentlyreceivedsomecomplaintsfrom our customersdueto the poor quality. For instance,pinholesandshrinkage.The defectswere only referredto powderfreenitrite glovesandthere was nothing wrong withthepre-powderedtype. Furthermore, the defectswere only detected once the goods reachedthe destination, which initiallywere found in good conditionaud passedall the QA inspections before shipment tookplace.

As far as we are concerned,we have no idea whether thedefects were due to either ourproduct failuresor environmen

tal stresscracking failures, butonething we aresureot is thatchlorination plays a key role inthe mentioneddefects.

Ng ChangKeongPamitexIndustries

Malaysia.

Formulations were received.For purposesof confidentiality,thesearenot beingpublished.

* Shrinkageof nitrile usually happens if the forms are too hotwhen entering the latex. Thegelledlatexshrinks downimmediately after the forms leavethelatex tank. If this is the type ofshrinkageyou areexperiencing,reduceform temperatures.

I havenot experiencedshrinkageof a curednitrile film eitherwith or without chlorination.

* Pinholesfrequentlybeginto leakafter chlorination. This condition becomesworseafterseveral weeks’storage.In my experience, this hasbeendueto thethin film over small air bubblesin theglovebecomingbrittle dueto chlorination.This brittlenessincreasesduring storage.

When theglove is stretched,thethin brittle film over the airbubble breaksand leakageoccurs. Chlorinated rubber is abrittle material. If bubblesarepresentin thegloves,theproblem you describewill occun

Theproblemcanbereducedbyreducing the Cl2 concentrationor the timeof chlorination.Theproblem can be eliminatedbygetting rid of theair bubbles.

* Chlorinatedgloves do not agewell, particularly if they areover chlorinated. It is possiblethat insteadof thepinholeproblem I describedabove,you areactually getting small cracks inthefilm which areleaking.

Microscopicexaminationof theleakwill reveal if it wasacrackor if it wasa brokenairbubble.

*Your formulasaresatisfactory.Be sureall powdersaregroundto lessthan 5 micronsand thatadditions of all materials aremadeslowly. Materialssuchassurfactants, which are sometimes very viscous, should bediluted beforebeingadded. *

78 RubberAsla U September- October 1999