The Latex DoctorC l would appreciate it if you could send me

any information on sources from where I canpurchase EPDM in latex form to be used In my researth project.

G.IAD. Krishantha

O verthe yearsI’ve encounteredonly onemanufacturerof EPDM latex. However,

about5 yearsago thatcompanywasacquiredand EPDM was dropped.I currently haveaproject which will require EPDM latex. I’mplanning to get a small quantity of LowMooneyViscosity EPDM and attemptingtoemulsify it.

soluble,theydo notrequiredispersing.

2. A word of caution,since sodiumacceleratorsare soluble,leachingat the gelled filmstatemustbe avoidedsothatacceleratorsarenot removedbeforevulcanisation.

3. By experimentation,reducethe amountof acceleratoraddedto your compound,andtherebyreducethe amountof unreactedacceleratorremainingin yourproductafterit is processed.

4. Switch to a zinc oxide which willrequire much less to producea satisfactoryproduct.

I’m goingto try the basicoil into water typeemulsification which is available in theVanderbiltHandbook.

If you wishto try thesameapproach,EPOMis availablefromUnimersIndiaLimited. E-mailaddress[contactusunirners.com1.

waysto get rid ofzinc ionsAre there any recommendations for the reductionof zinc ions in the effluent of a latex manufacturing plant?

Anonymous-Iniernotionilt LatexConference,

T herearesomebasicstepsto betakenotherthan final effluent treatmentwhich canre

ducethe zinc ion concentratiom

1. Changeacceleratorsfrom zinc saltstoSodiumsalts.This canusuallybeaccomplishedwith no changein the vulcanizationprocess.Also since sodium acceleratorsare water

Age and season can makea differenceIs the latex from very mature trees different fromthat of very young? What are the differences?What are the advantages/disadvantages for certain products that are made using one versus theother?

Anonymous- InternationalLatexConference.

T his is notmy areaof expertise.Thisquestion shouldbe directedto the Malaysianor

Thai "Rubber Board" wherethereare peopie with many years of experiencewith latex from varietiesof clonesas well as fromtreesof all ages.

However, I havehad experienceswhichshowthat therearegreatdifferences.LatexfromLiberia processesdifferently from latex fromMalaysiaLatextappedin one time of the yearprocessesdifferently from latex tappedin anothertimeof theyear.

Thesedifferencesare not asgreatas theywere40-50yearsago. Latexproducersandsuppliers have takenstepsto reducethesedifferences.however,they do exist. I would recommendclosecontactwith your latex suppliersothat you are awareof the differencesin the latex you arebuying.

I haveneverencountereda commercialIatex which I couldn’t use,However,compoundrecipes and processconditions were sometimes changedto maintain productqualitystandards.

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DM in latexrm for

research project

Harry F. Bader.Vice-President, LatexSeMces, Akron RubberDevelopment Laboratory.Akron. USA, and a worldauthority on latex,answers questionsand doubts of readers onlatex and latex products.Send your questions to:The Latex DoctorRubberAsia, OhananiHouse. cochin 682 020,Kerala, IndiaFax 91-484-2317872E-mail: dhanrubber@eth.netRubber Asia MAY-JuNE 2006 97

CONTINUED FROM PAGE 9?

The issue of blendingTo blend or not to blend? That is the question.Often when two or more lattices are blended,worst of the two worlds are expected. But, theoretical consideration of the polymers may suggestthat optimum properties may result from ablend-either through physical association PINor through associative properties, is there anyguideline for systematic blending - rather than itto be hit or miss?

Arcwind, Chennai

I ‘ve usedbothblendsand laminatesin latexproductsthatweresuccessfulin themarket

place. The benefitsare alwaysmodified by areductionof someof’ the individual propertiesof the partnersin the new product.However,propertieswere never the worst of bothpartners.

Blendsof neopreneand other lattices arewell-definedin the NeopreneLatex handbookof 1962by JohnC. Carl.

In my experience,the chemicalresistanceof naturallatex canbe improvedby an addition of neopreneor nitrile latex.Most physicalpropertieswill be reducedby this addition.However,it is possibleto maintaina satisfactory levelof physicalpropertiesandachieveasignificant improvementin oil resistance,airandchemicalpermeationresistancea-s well assunlightresistance.

Avoid high temperaturedryingwhat process changes should I consider whenlooking to introduce a dipped nitrile produce onmy machine designed to produce products fromnatural latex?

Anonymous- JnternationaLaterConference.

T hemainproblemI’ve experiencedwasdueto the lowerpercentof rubbersolids in the

nitrile latex. This resultsin productshrinkageduring manufacturingthat is muchgreaterthanwhat is experiencedwith naturallatex.

High temperaturedrying shouldbeavoided.Also ahigherdippinglevel islikely tobeneededto offsettheshrinkage.

With the high water contentgreatercaremustbe taken in the drying. Vulcanisationisadverselyaffectedif the film moisturecontentis above1%. That is mostlydueto the expectedvulcanisationtimeactuallybeing usedto conipletethe drying.

Compoundingproceduresshouldbe moth-fled to minimisewater additions.

Maturing shouldbe carefully controlledtoachieveefficientvulcanisationafteron-linedrying is complete.

Adding fragrance tolatex foamWe are a unit manufacturinglatex foam since198$.We have the following doubts.

1. Can we add fragrances to latex foam to avoidcomplaints from some customers that it smellsrubber.

2. Some customers ask me for bamboo charcoal loaded foam, In India what is the source andformulation.

3. We do make extra thick mattresses of morethan 160 mm, how can we improve the drying ofsuch products using conventional driers, Somebodysuggested to go for microwave drying - Is it costeffective and viable?

ManagingDirector,MNKlnctustt-ialProducts,India

I ‘ve usedfragranceswith latexproducts.Wefoundthat manywereobjectionabletdSome

people, We eventuallysettledon aroseflowerscentwiuchwaspleasantto themajorityof people.! suggestyou getsamplesof variousscentsandalso of deodorants.Make samplefoam inyour lab andseeif a panelof peoplefinds thempleasant.

Also you may wantto investigatehow efficient you are in washing the foam to removechemical residuesbefore you commencedrying.

2. I haveno informationon this subject

3’ I would expect that well-controllednucrowavingcouldbea satisfactorymethodofdrying. However,I’ve neverheardof it. Considering the high flammability of latex foam andthe possibilityof ‘hot" spotsbeingpresentin amicrowave,I stronglysuggestsmall-scaleexperimentationas well as consultationwith microwaveexperts.

ManyyearsagowhenI wasaTechnicalService Engineerfor a pillow and mattressmanufacturer,our drying was improvedby installinghigh-pressurerollersto removethe major partof the wash water before the productswereplacedon mesh racks in a high-velocityoven. *

MAY-JUNE 2006 99

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