The latex doctor

Send your questions to:

The Latex Doctor’Rubber Asia,Dhanam House,Cochin - 682 020,Kerala, IndiaFax: 91-484-2317872E-mail: danam@satyam.flet.indhanrubber@eth.net

Right accelerator-A/Ocombine, latex discolourationcauses; NRL prospects etc. -

in latexrubber,chemicalsareusedin the form of dispersions.In maldng dispersionsandemulsions, how do we selecta proper acceleratorand a/o combinations in any latex compounding. In the case of solidrubber, we can check curingtime for an article on OUR or!sWR andthen one can fix thetime for curing. In the caseoflatex, by which method cancure time bechecked?

And if you have guideformulations for dispersions,emulsionsandlatex compounding formulations, pleaselet usknow.

Anand on e-mail

T his is a multiple questionwhich I cannotreply to in thespaceprovided in RubberAsia.However, the following willprovide someguidance:

Dispersion

1. First of all, I would suggestyou obtaina sourceof informationaboutdispersionsandhow dispersionsaremadeplus suggestedrecipes for dispersing commonlatexcompoundchemicals.

Threesourcesare:

- The Vanderbilt LatexHandbook, 3rd edition. 1987.R.T. Vanderbilt CompanyInc.www.rtvanderbilt.com

- NeopreneLatex, John D.Carl, 1962, E.T. DuPont andCo. Inc. www.dupontdow.corn

- PolymerLatices, 3rd edition,1997, Chapman& Hall IndiaMadras600035

Theseprovideavariety of infor

mation, including typical dispersion recipes;ball-mill grinding recommendations,particlesizemeasurement;also guidancetowardsavoiding the manypossibleproblemswhich comefrom improperdispersions.

Latex compoundrecipesare inthesamereferences.

2. These samereferenceswillprovideguidancefor theselectionof acceleratorsand antioxidants.Of course, an understandingoftheserviceexpectedfrom the latex1iroductwill guidetheselectionofantioxidants.Also, theprocessingto be usedwill help in the selection of accelerators.

3. It must first be decidedif apre-vulcanisationor post- vulcanisationsystem is to be used.Thisdone, acceleratorsand a processsystem can be chosen. At thattime, it can also be decided ifresidual acceleratorsare to beavoided. This will also influencethechoiceof accelerators.

4. For a post-vulcanisationsystem: Oncethelatex film hasbeendried to a moisturelevel of 1% orless,acure time of 15-20minutes© 116°C shouldbesufficient. Fora pre-vulcanisation system, nocure is required after drying iscompleted.

Final physical properties willshow if everythinghasbeendoneproperly

I am a chemist with KurlonLtd., a rubberised coir manufacturing firm in south India. Inthe case of dry rubber compounds it is possible to find outthe "vulcanisation time" by

jarry F. Bader

1-lanyF. Bader,Vice-President,LatexServices,AkronRubberDevelopmentLaboratoxy,Akron,USA. anda worldauthorityon latex,answersquestionsanddoubtsofreadersonlatexand latexproducts.

97RubberAsia * March . April 2005

using Rheometer.Is thereany ,uick answeris Yes. There I believethe naturallatex mar-method to find out thesamefor aremanydifferences: ketpercentagewill grow morecompoundedlatex? - The chloroform pre-cure than

syntheticpolyisoprene.Thereareseveralreasonsfor my belief:PradeepKumar P. Joy, measurementwhichworks well

Bangalore for NR latex doesn’t work for * The processingof NR Latexsynthetic polyisoprene. You will greatly improve both the

I f you feel confidentthat you must usen-butyl alcohol. But, residual acceleratordermatitiscan predict the vuicanisation the hexaneswollen diameter problemandtheprotein allergytime by a Rheometer,thendo the method works for both, problem.samewith thelatex. Dry thelatexfilm c 70°C until the moisture * Standardmaturing

methods * Othersourcesof naturallatex

content is less than 1.0%. Then pre-vulcanisationarenot whatwill come into play as alterna

runa Rheometercurveon thedried you would expectfrom NR tives to Heveanaturallatex.

film latexcompounds. How they * Clonesof Heveawith greatly

differ will, as expected, vary reducedproteincontentwill beGenerally, if a latex film is dependingupon thecompound developed.

dried to 1.0% moisture, a 15-20 recipe and the accelerator * Methods of de-proteinisingminutecure@116°Cwill provide system being used. The naturallatexwill be developed.Usatisfactoryphysical properties. polymerisation agent andHowever, if the chloroform stabiliser residuesin the synprecure indicates pre-vulcani- thetic polyisopreneare, in mysation, then only drying is opinion, a major reason for Statementabout ownership

required. thesedifferences,and other particulars of

RUBBER ASIA*** Form IV, SeeRulesS

What testing can we do to en- What is thecauseof pink dis- Ple ofsurea glove will meet require- colouration on my latex gloves publication : Cochirtments for food contact? after 1-2 weebssix plant process

RubberResearchTecb.Indus- storage?Periodicity ofpublication : Bimonthly

try, Maharashtra,India Anonymous - InternationalLatex Conference2004 Akron

F or use in theUS, the requirementsare in theUS Code Discoloration can occur forof FederalRegulations21CFR. numerousreasons.SomeofFood and Drug Regulationshas themare:

Printer’s name : KurianAbraham

Nationality : Indian

Address : DhanamHouse

in Sec. 21 CFR177.2600, a list-. Gloves are wet above 1%

of materialsand theconcentrat- moistureions thereofwhich arepermittedin productscoming in contactwith Storagetemperature

is high.

food or food products. a- Ozoneconcentrationis high instoragearea.

Also in that section there areextractionproceduresand speci- Gloves are exposedto fluore

fications for maximumallowable scent light.

total extractionquantitiesin disti- a- Gloveswere hot whenput intolied waterandHexaneextraction storagecontainers.

29/609KadavanthraCochin

- 682020Editor s name : Kurian

Abraham

Nationality Indian

Address : DhanamHouse29/609ICadavanthma

media. Thepink colouris likely duetoWith your glove compound the antioxidant being used. 2,2-

recipe, you can determineif th Methylenebis 6-4 butyl-4-me-materials content is within the thylphenol is an excellent and-

Cochin682020

Namesand addressesof mdividuals who own the newspa

allowable limits, oxidant. However, when it reacts per and partnersor sharehold

Extractions in DI Water and with oxygen,thereactionproduct

Hexane will determine if your is pink. The physical properties

productmeetsthe requirements. are generally protected,but thepink colour is a problem. I

NOTE: For non-USrequireme- suggest you try a non-stainingnts, investigatethe specification AG such as 4,4-Butylidenebisfor thepoint of salecountry. 6-t-butyl-rn-cresol. There are

cr5 holding more than one percent of the total capital:

Dhanam Publications I’Ltd., Kadavanthra,Cochin - 682 020.

I, Kurian Abraham, hereby dedare that the particularsgiven

*** severalmanufacturersof this. above are true to the best oi my

Is thereany differencein maturing polyisoprene latex and Betweensynthetic and natu-natural rubber latex? ral latex, which hasthe better

Anonymous,2004International market growth potential overLatex Conference,Akron, Ohio thenext 5 to 10 years?

knowledge and belief,

Sd-

Kurian AbrahamPublisher

98 RubberAsla * March ‘ April 2005