The latex doctorHarry F. Bader
Resistance to airpermeationWater leakage
I made natural latex bladders,and I search for one naturallatex mix with other latex orproducts for inipermeabilizationto the air for inflatable dippingproducts. Can you help me?
Victor Rodarte
L atex polymers other thannatural rubber latex have
superior resistanceto air permeation. These includepolychioro-prene, nitrile andbury!. These are generally notsatisfactory as replacementsfornatural rubberlatex becausetheydo not have the sameresilience.Sportsballbladdersrequirea good"bounce" - There is also theproblemof increasedcost.
An alternative to total replacement of thenaturalrubber latex isto apply anoverdip of oneof thesepolymersat a thicknesswhichdoesnot adverselyaffect thebounce.
I havemadenaturalpolychloroprenelaminatesin this fashionona production basis, and experimentally with natural/niHlIe andnatural/huty!. The natural polychioroprenehada goodservicelifeand noticeahy improves theresistanceto air permeation.
Laminar fillei-s suchas micawillalso improveresistanceto air permeation. Usea slurry ratherthanadispersion,sinceball mill grinding reducesthe flakesizeanddestroys thepermeationresistance.
Some development work isrequiredto get theproper recipesand theproperprocess.
I am engagedin an independent researchproject. I want toknow whether a virus canpenetratethroughlatex pores. I
need any available informationthat you could give meon testingthat your company has done;particularly the watertightleakagetest.
Joshua
T hereare a numberof specifications which apply to
freedom from holes waterleakage for both condomsandmedical gloves. These are"copyrighted" so I cannotprovidethem to you. However, they arereadily availablefrom the library.
GlovesASTM D 3577Surgeon’sGlove
Specifications
ASTM D 3578 ExaminationGlove Specifications
ASTM D 5151 Water LeakageTestMethod
ISO 10282 Surgeon’sGloves
ISO 11193 ExaminationGloves
FDA CFR 21 Part 800 Surgeon’s andExaminationGloves
CoiWoms
ASTM D 3492 N.R.LatexCondom Specification
ISO 4074 N.R. Latex CondomSpecification
FDA Guide 7124.21 Samplingfor WaterLeakage
BothASTM F 1671 Pathogen
Penetration
Water leakagetesting to meetall the above standards isperformed by independentlaboratoriesandby manufacturersof the products. It is generallyacceptedthnt thematerials,naturaland synthetic, used for condomsandmedical gloveswhen formed
Harry F. Bader,Vice-President,LatexServices,Akron RubberDevelopmentLaboratory. Akron,USA, and a worldauthority on latex,answersquestionsanddoubtsof readerson la,exand latex products.
Send your questions to:
‘The Latex Doctor’Rubber Asia,Dhanam House,Cochirt- 682 020,Kerala, IndiaFax; 94-4S4-317872
81RubberAsia U May- June 2001
into an intact film free ofdetectable water leakageholes,will not allow the penetrationofHIV virus.
There are several semi-annualinter-laboratory trials which areconductedto measurethe qualityof the testing. The accuracyofthe results is operator sensitive.As almost everything in thisworld, if doneproperly it is good.If not doneproperly, it’s not good.
Regulatoryagenciesthroughoutthe world are also doing testing.Throughthecooperativeefforts ofthe manufacturers and theregulatory agencies,the world’ssupply of both condoms andmedical gloves is constantlyimproving.
The problemof increasingvirusinfections is not due to poorproducts,but ratherdueto failureto acceptthatprotection.
We manufacturetoy balloons.Sometimeswe havehigh loss dueto tearu when removing theballoon from the dip form. Weusea 6% powder in coagulant.
Powder Is
10% Calciumnitrate
40% Talc
50% Diatomaceousearth
How can tearsbestopped?Isa better coagulantneeded?
Anonymous
ere could be many reasonswhy you arehavinga problem
such as you have described.Following aresomepossibilities:
The pre-cureof your latex mayhe high and, therefore, the filmwill havea lower tear resistance.
The coagulant tank agitationmay be poor and some of thepowder is setting to the bottom.If so, your 6% powderwould bemuchlower. This couldgive lessmould release.
The level of your coagulantoryour latex may be miss-matched.I would expectthe latex to bea hithigher thanthecoagulantso a thinfilm start to thebeadroll he made.If the film is too thick at the startthe bead will be loose and willlikely to be too large- Both canhavea highernumberof strip tears.
Both latex andcoagulantlevelsmight be too high. which would
leadto havingthick beadrolls andsubsequentlymore strip tears.
I suggesttwo things to bedone.
1. Whenthings arerunningwelland strip tear numbers areacceptable,check on the variousprocessconditions: suchas latexpre-cure level, latex viscosity,latex % ‘1SF, latex temperature,latex gnd coagulant levels onforms, actual coagulantpowderconcentrationat thedipping level,coagulant temperature, formtemperaturesat various points,beadroll thicknessandpositiononthe form, are forms clean? andwhat areoven temperatures’?
If you can establish whatconditionsarewhen quality is good,this givesguidancetowardcorrectingthings when quality is bad.
2. In any case,stripping canbemade easier by adding 2-3%polyethylene glycol to thecoagulant. I suggestPEG 1450,whichwasmelting pointjustunder50°C. This would be a solid atdipping temperatureanda liquid atstripping temperature.As a liquid,it is a good lubricant. If your temperaturesarehigheryou may wantto usePEG 4600 or 80W.
In an air cargo condition,wheretemperaturesdropbelowzero celsium, will this affectnitrile gloves ? Causecrack oranything or damageto nitrilegloves?
Alliance
R eiclthold ChemicalCompanyleading U.S. supplier of
nitrile latex saysthe polymerTgglass transition temperatureis-30°C. This is a commontemperature in Canadain thewinter and!would alsoexpectit to becommonin unheatedcargoplanes. However, I haveno knowledgeof actualtemperatures.
Although the additives in a latexrecipewould likely to raisetheTgsomewhat,it wouldn’t get to 0°C.I and thetechnical representativeat Reichholdhaveneverheardofcold cracking of nitrile glovesduring air cargo transportation.Cold cracking analysis is acommontest for rubberproducts.You may wish to check yourgloves to determinethat criticaltemperature. N
82 RubberAsia * May - June2001
