JW Latex Consultants (and Rubber Consultants,乳胶顾问) offer solutions to your problems in Natural Rubber latex and Synthetic Rubber latex processing and the manufacturing of latex products (condoms, catheters, medical gloves, baby teats and soothers, toy balloons etc) Quick answers through e-mails are possible at reasonable cost.



(Please click on the following selected subjects to view the Q&A)

[Adhesion and Cohesion].. [Adhesive Bonding of Rubbers 1].. [Adhesive Bonding of Rubbers 2].. [Advantages of Prevulcanization].. [Ageing of Natural Rubber 1].. [Ageing of Natural Rubber 2].. [Ageing of Natural Rubber 3].. [Air Bubbles in Latex].. [Air Permeability 1].. [Air Permeability 2].. [Alkalinity and pH of NR Latex].. [Applications of PV Latex].. [Artificial Latices].. [Bacteria and Latex].. [Balloon Defects].. [Binding Agent].. [Biodegradability of NR 1].. [Biodegradability of NR 2].. [Black Articles].. [Blending of Different Latices 1].. [Blending of Different Latices 2].. [Blooming of Chemicals].. [Bouncing Ball and Tyres].. [Bursting of Toy Balloons].. [Carpet Backing Compound 1].. [Carpet Backing Compound 2].. [Carpet Backing Compound 3].. [Carpet Backing Compound 4].. [Cement/Latex Mix].. [Chemical Toxicity].. [Coagulant and Rubber Transparency].. [Coagulant - Water vs Alcohol ].. [Compression Set].. [Condoms].. [Condom Tearing].. [Copper Staining].. [Creaming 1].. [Creaming 2].. [Creep of Rubber].. [Cross-Linking Density on Rubber Properties].. [Cross-Linking Effects on Rubber Properties].. [Cyclohexylamine Acetate as Coagulant]..


[Defoamer].. [Delamination Problem].. [Demoulding of Latex Foam Products].. [Detergent Resistance of Latex Products 1].. [Detergent Resistance of Latex Products 2].. [Dipping Problems 1].. [Dipping Problems 2].. [Dipping Problems 3].. [Discoloration of Latex Products 1].. [Discoloration of Latex Products 2].. [Discoloration of Latex Products 3].. [Dispersions of Rubber Chemicals].. [DRC of Latex].. [Evaporated Latex Concentrate - Viscosity].. [Extruded Rubber Bands].. [Extrusion of Medical Tubings].. [EV and Semi-EV Cure System 1].. [EV and Semi-EV Cure System 2].. [EV and Semi-EV Cure System 3].. [Fabric-Lined Gloves].. [Fatty Acid Soaps].. [FDA Approved Antioxidants and Antiozonants].. [Filler 1].. [Filler 2].. [Filler 3].. [Flame Retardant].. [Flock Lined Household Gloves 1].. [Flock Lined Household Gloves 2].. [Foaming Agents].. [Foam Stabilizers].. [Food Packaging].. [Freeze-Thaw Stability of Latex 1].. [Freeze-Thaw Stability of Latex 2].. [Friction of Rubber].. [Gamma Radiation vs Ethylene Oxide].. [Gelling of PVC Plastisol in Oven].. [Gel Strength of Latex 1].. [Gel Strength of Latex 2].. [Glove Demand].. [Glove Discoloration].. [Glove Selection].. [Grafted Latex].. [Guayule Latex]..


[Heat Sensitivity of Latex 1].. [Heat Sensitivity of Latex 2].. [History of Gloves 1].. [History of Gloves 2].. [HLB Balance of Surfactants].. [Hysteresis].. [Inorganic Phosphate and Latex Stability].. [Joul Effect].. [KOH Number of NR Latex].. [Lab Equipment].. [Latex Particle Size and Molecular Weight].. [“Latex” Definition].. [Latex Based Adhesives vs Solvent Based Adhesives].. [Latex Foam].. [Latex Processibility].. [Latex Skins and Lumps].. [Latex Stability 1].. [Latex Stability 2].. [Latex Technology - Training ].. [Latex Thread 1].. [Latex Thread 2].. [Latex Thread 3].. [Latex Thread 4].. [Latex Thread 5].. [Leaching].. [Low Temperature Applications].. [Milling of Rubber Chemicals].. [Milling Problem].. [Mixing Equipment Directory].. [Mold Growth].. [MREPC Articles].. [Nano Polymer Particles].. [Nano ZnO].. [NBR vs SBR].. [Natural Rubber from Dandelions].. [Natural Rubber Latex Stability].. [Odour of Rubber 1].. [Odour of Rubber 2].. [Ozone Attack 1].. [Ozone Attack 2]..


[PA-80 Rubber for Extrusion].. [Permanent Set].. [Plasticisation].. [Polychloroprene 1].. [Polychloroprene 2].. [Polychloroprene 3].. [Polychloroprene 4].. [Positive Charged Latex].. [Powder in Coagulant 1].. [Powder in Coagulant 2].. [Pre-Cure and Maturation of Latex Compounds].. [Prevulcanisation Inhibitor].. [PVAc Emulsion for Adhesives].. [PVC Latex].. [REACH].. [Reconstituted Leather].. [Resilience 1].. [Resilience 2].. [Rubber Bands].. [SBR Latex - Carboxylation 1].. [SBR Latex - Carboxylation 2].. [SBR Latex - Stability Against Filler].. [Skin Irritation].. [SMG].. [SMG].. [Sodium Soaps vs Potassium Soaps].. [Solvent Resistance of PV Latex Film].. [Solubility Parameters].. [SP/PA Rubber ].. [Stereoregularity of Rubber Moleccules ].. [Stiffness of Latex Products].. [Stiffening Agent for Latex Products].. [Storage Hardening].. [Storage Condition for Latex].. [Stress Relaxation].. [Surface Tension in Latex Dipping 1].. [Surface Tension in Latex Dipping 2].. [Surfactants 1].. [Surfactants 2].. [Surfactants Against Calcium Ion].. [Surfactants Directory]..


[Tackiness of Adhesives - Wet Tack and Dry Tack].. [Tensile Testing and Inconsistent Results 1].. [Tensile Testing and Inconsistent Results 2].. [Thickeners for Latex 1].. [Thickeners for Latex 2].. [Thickeners for Latex 3].. [Tensile Properties].. [Thickness Control of Latex Dipped Products 1].. [Thickness Control of Latex Dipped Products 2].. [TMTD in Latex].. [Toxicity of Rubber Chemicals ].. [Training in Latex Technology 1 ].. [Training in Latex Technology 2 ].. [Training in Latex Technology 3 ].. [Transferring of Latex].. [Transparency of Latex Products 1].. [Transparency of Latex Products 2].. [UV Degradation].. [VFA of Latex].. [VFA vs KOH Number].. [Viscometers].. [Viscosity of Polymer Emulsions - On Storage].. [Vulcanization].. [Vytex].. [Waxes in Rubber].. [Wetting Agents for Coagulant 1].. [Wetting Agents for Coagulant 2].. [Wetting of Coagulant].. [Xanthates].. [Yulex]..
[ZDEC in Latex].. [ZnO in Latex].. [ZnO and Latex Compound Shelf-Life].. [ZnO Thickening].. [ZOT - ZnO Thickening Test ]..


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Saturday, July 14, 2018

Why Can't We Make Very Thin NR Gloves?

Manufacturer: Most glove manufacturers today are making medical examination gloves based on NBR latex. In fact, the NBR gloves are now very light and thin. Why can't we make NR gloves with similar weight and thickness? We were encountering many problems when we tried to do this.

John Woon (Senior Latex Consultant): Yes, Nitrile examination gloves are getting thinner from approximately 7 to 9 grams to 3 to 5 grams per glove (i.e. from about 0.15 mm to 0.05mm). This is to ensure "softness" of the gloves.

While the physical properties (i.e. tensile strength, modulus and elongation at break) of the glove remain unchanged, the thinner the glove, the "softer" would be the glove to the touch. As a result, the dexterity and tactility improve. Likewise, a rubber film always feels "softer" than a rubber sheet although both are made using the same rubber compound, with no change in the inherent modulus.

But why can't we make similar thin gloves with NR latex?

The answer is quite simple, really. It has a lot to do with the modulus of the base rubber. Compared to Nitrile rubber, natural rubber has quite a low modulus. Therefore, a thinner NR examination glove would be too soft to handle or process, not to mention the possible higher degree of tackiness.

The solution to this "problem" is obvious - Increasing the modulus of the NR gloves.

This can be done in either one or a combination of the following steps:

1) Re-design of the curative recipe e.g. increasing sulphur level, use of ZDEC/ZMBT blend (Note: a curative for maximum tensile strength would also help)

2) Addition of high-styrene SBR latex

3) Addition of Methyl Methacrylate-grafted NR latex

Friday, July 13, 2018

Difference Between "Latex Gel" and "Gel Content" of Latex

Manufacturer: When studying latex technology, I was very confused over the term "gel". What actually is the difference between "latex gel" and "gel content" of latex?

John Woon (Senior Latex Consultant): Good question! At one time, I was confused too! In a typical uncompounded latex, either natural or synthetic, some cross-linking of the rubber molecules sometimes takes place forming a network of usually quite large size.

If one dissolves the dry rubber (from the latex) with a solvent, the content that remains undissolved (although swollen in some cases) is termed the "Gel Content" whereas the rubber that has been dissolved is termed "Sol Content".

On the other hand, "Latex Gel" refers to the formation a continuous soft solid as a result of colloidal destabilisation of the liquid latex, for example, when the latex is exposed to a gelling agent such as ammonium acetate.

Tuesday, June 26, 2018

Formation of Skin and Lumps in Latex Dipping Tank

Manufacturer: I kindly request you to spare sometime to look into the matter and
suggest your opinion.

In some occasions we experience some problems like formation of skin and lumps in the dipping tank (lump comes along with the former) even using latex with acceptable latex parameters like low V.F.A, good M.S.T, KOH Number and maintaining process parameters like coagulant
concentration, oven temperature, former temperature in good condition. Parameter wise the latex is seems to be good, but performance wise it behaves not good.

Is there any other test method to verify the quality and stability behaviour of centrifuged latex before using for processing ? Kindly advise how to tackle the matter.

John Woon (Senior Latex Consultant): Please take note that sometimes the usual latex concentrate properties such as VFA Number, MST, KOH, etc. do not fully tell you how the latex would perform in a given latex product manufacturing process. Different batches of the latex concentrate with similar properties might behave quite differently even in a well established dipping process.

If you are encountering the coagulum and skinning problem with only certain batches of latex (especially over a one-year period) it might be due to the latex itself, probably as a result of seasonal changes in the inherent latex properties which could not be detected by the usual standard tests.

However, if you are facing the problems consistently with every batch of latex over a long period, you should investigate to see if the causative factors actually come from the dipping process itself.

I believe there is a strong possibility that your formers could be insufficiently dried before they enter the latex dip tank. This could result in the formation of skins and coagulum when the fluid coagulant comes into contact with the latex surface.

Tuesday, May 29, 2018

The Language of Rubber Properties and Behaviour – Permanent Set

Manufacturer: We are a group of university students from India. Can you please explain in simple language what "Permanent Set" of rubber means? We've been arguing this with our supervisor. We hope your explanation can put to rest this argument. Sorry to trouble you.

John Woon (Senior Latex Consultant): When rubber is distorted for a given duration, the degree of deformation after the release of the distortion force is referred to as the Permanent Set.

If the deformation is caused by tension, it is known as Tension Set.

On the other hand, if it is caused by compression, it is described as Compression Set.


Permanent Set is therefore defined as the amount of residual displacement after the distortion load is removed. Permanent Set is worse at elevated temperatures. Generally, the lower the permanent set, the higher would be the resilience and elasticity but the lower would be the Tensile Strength although there are exceptions.

A poorly or insufficiently vulcanized rubber would usually exhibit high Permanent Set. Choice of the vulcanizing system also plays an important part in determining the degree of Permanent Set. If the lowest possible Permanent Set is required for certain applications especially at elevated service temperatures, the sulphur to accelerator ratio should be low and sometimes the elemental sulphur is totally omitted in the compounding recipe.

Permanent Set is closely related to another important property of rubber products, namely the Stress Relaxation.

Go to the following link for the video on how Compression Set test is carried out:

(The Rubber samples are put into the fixture and spacers are used to compress to the appropriate size. The samples are then left for a given period at room temperature or elevated temperature. After the test is complete the height of the rubber samples is measured and the before-and-after heights are compared)


What has the bouncing ball to do with tyres?

Latex Gloves Educational Articles from the Malaysian Rubber Export Promotion Council

How do you select your medical gloves?

Rubber Chemicals: Carcinogenicity, Mutagenicity, Clastogenicity.

Why is Compression Set measurement important?

Assessment of Latex Stability

Joule Effect

Poor Flocking Quality Of Household Gloves

Creaming of Latex

What is Vulcanization?

History of Latex Dipped Products

Applications of Prevulcanized Latex

Defoamer Creating Havoc in Glove Factory

Problems With Milling Rubber Chemicals

Medical Gloves From Guayule Latex

Introduction to SMG Gloves



Click on The Following Links to Read More Articles:

[Advantages of Vulcanization] [Applications of PV Latex] [Bacteria and Latex] [Chemical Toxicity] [Cross-Linking Density] [Biodegradability] [Black Articles] [Blooming] [Bouncing Ball] [Compression Set] [Condoms] [Creaming] [Defoamer] [FDA] [Fatty Acid Soaps] [Flame Retardant] [Flocking] [Food Packaging] [Glove Demand] [Glove Selection] [Guayule Latex] [History of Gloves] [Joul Effect] [Latex Stability] [Latex Thread] [Milling Problem] [MREPC Articles] [Nano Polymer Particles] [Nano ZnO] [Polychloroprene] [REACH] [SMG] [Storage Hardening] [Vulcanization] [Vytex] [Yulex]

The information and data contained in this site are believed to be accurate and reliable. However it is the responsibility of the visitors and readers to satisfy themselves that the information is workable under their own processing conditions. Hence the owners of this site make no warranties concerning the suitability of the information given in this site.