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.



[Advantages of Prevulcanization] [Air Permeability] [Applications of PV Latex] [Bacteria and Latex] [Chemical Toxicity] [Cross-Linking Density] [Biodegradability] [Black Articles] [Blooming] [Bouncing Ball] [Compression Set] [Condoms] [Copper Staining] [Creaming] [Defoamer] [FDA] [Fatty Acid Soaps] [Flame Retardant] [Flocking] [Food Packaging] [Glove Demand] [Glove Discoloration] [Glove Selection] [Guayule Latex] [History of Gloves] [Joul Effect] [Lab Equipment] [“Latex” Definition] [Natural Rubber Latex Stability] [Natural Rubber Latex Thread] [Milling Problem] [Mixing Equipment Directory] [MREPC Articles] [Nano Polymer Particles] [Nano ZnO] [Permanent Set] [Polychloroprene] [REACH] [SMG] [Storage Hardening] [Stress Relaxation] [Surfactants Directory] [Tensile Properties] [Vulcanization] [Vytex] [Yulex]


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Friday, June 09, 2017

Aqueous Dispersions of Rubber Chemicals

Manufacturer: We are encountering poor dispersion of rubber chemicals such as sulphur, accelerators and antioxidants used for latex compounding. This has resulted in sedimentation to the extent of forming hard cakes that are difficult to be re-dispersed. We would appreciate very much if you could give us some guidance to overcome this problem.

John Woon (Senior Latex Consultant): Achievement of a well milled and well dispersed rubber chemical in water entails a lot of details which cannot be sufficiently covered in this forum. If you want, I can prepare a comprehensive report for you.

However, in the mean time, you should pay close attention on all factors that allow you to achieve the following:

  • Wetting of Chemical Particles: All the air from the particle surface and between the particles of the aggregates and agglomerates must first be replaced by the solution of a dispersing agent or agents. The particle/gaseous interface should then be transformed into a solid/liquid interface.
  • Milling or Grinding and Separation: The composite from above mentioned step is then subjected to mechanical energy via impact and shear forces. As a result, the agglomerates are broken up  into smaller units and evenly dispersed.
  • Stabilization of the Chemicals Particles in Suspension: The chemical dispersion is stabilized by dispersing agents via the adsorption of molecules of these dispersing agents (usually some surfactants) at the chemical particle surface. This prevents or minimizes sedimentation and phase-separation.  
Let me know if you require a more comprehensive report with recommended recipes for the dispersion of each chemical you are using.

Monday, May 22, 2017

Oldest Rubber Trees in Malaysia

The oldest rubber tree of Kuala Kangsar in the state of Perak, Malaysia, is also one of the two oldest rubber trees still standing in Malaysia.. It stands by the roadside in front of the district office in Kuala Kangsar.  It was planted when the country was still called British Malaya.

It is one of nine seedlings brought over from Brazil by the English botanist H.N. Ridley (from Kew Garden, London) in 1877, about 140 years ago!

Saturday, May 06, 2017

Foaming Agents for Gel and Non-Gel Foamed Backed Products

Manufacturer: We are manufacturing products backed and coated with natural rubber latex foam using both "Gel foam" and "Non-Gel foam" systems. What foaming agents do you recommend?

John Woon (Senior Latex Consultant): For gelled foam based on either zinc/ammonia complex or zinc/sodium silicofluoride, you can use fatty acid soaps one good example of which is potassium oleate. You can either buy the ready made soap or make your own by reacting oleic acid with potassium hydroxide. Other possible soaps are caster oil soap and rosinates.

For non-gel foam, it is best to use anionic and non-ionic surfactants such as sodium dodecyl sulphates, sulphonates and non-ionic polyethylene oxide condensates. Do not use non-ionic foaming agents for "gel foam" as these would retard the gelling of latex.

Tuesday, April 18, 2017

Evaporated Natural Rubber Latex Concentrates Now Available from a Thailand Manufacturer


Evaporated Natural Rubber Latex Concentrates Now Available from a Thailand Manufacturer

Evaporated latex concentrates have an intrinsic property of much higher total solid content (TSC) of up to 75% compared with up to only 62% of centrifuged latex concentrates while still retaining all the inherent small rubber particles and non-rubbers........
CLICK HERE for details

Monday, April 10, 2017

Demoulding Problem of Latex Foam Products

Manufacturer: We are latex foam products manufacturers. Recently we have been having problems of demoulding of our products from the molds resulting in high rejection due to tearing. Your advice would be appreciated.

John Woon (Senior Latex Consultant): All products made from rubbers or elastomers with some forms of moulding should be able to be removed from the moulds easily at the end of each cycle of moulding without undue stress being applied to the products. Your encounter of the demoulding problem could be due to poor cleaning process for the moulds and/or wrong choice of releasing agents.

I suggest you introduce a proper cleaning process to ensure that all surfaces of the moulds are free from the cumulative build-up of non-rubbers from the latex and compounding ingredients.

As for the releasing agents, you can try aqueous solution of sodium carboxymethyl cellulose or it's derivatives and low-molecular-weight polyethylene glycols. You can use either of these or a blend of both. This is best applied by spraying while the moulds are still hot.

Monday, March 27, 2017

JW Latex Consultant's New Website Launched!

We are very pleased to announce the launching of our brand new website at https://slwoon2.wixsite.com/johnwoon 

You are welcome to check it out!

Monday, March 20, 2017

Why Does Dilution of Natural Rubber Latex Cause Latex Detabilisation?

Manufacturer: We always encounter coagulum problem when we dilute our NR latex compounds with water. Why is this so? Please help!

John Woon (Senior Latex Consultant): If your latex compounds are well stabilised with sufficient soaps/stabilisers, dilution with water generally would improve the latex stability.

I believe your latex compounds are not properly stabilised and when water is added, the concentration of stabilisers present in the water phase is reduced, hence a reduction of latex stability leading to the formation of coagulum.

What you can do is to add some stabiliser (similar to that used in the latex) to the water before dilution.

Sunday, March 05, 2017

Second Edition of "Practical Latex Technology" Launched!

JW Latex Consultants are pleased to announce the launch of our Second Edition of the 159-paged Ebook, "Practical Latex Technology" with more additions of Q&A.

It contains answers to more than 150 questions plus other very useful tips and ideas!

For easy of reference, it is divided into 5 Parts:

Part 1: Vulcanisation
(Vulcanization), Vulcanisation of Latex and Prevulcanised Latex
Part 2: Properties of Rubber
and Latex
Part 3: Problems of Latex
Processing and Finished Products
Part 4: Compounding Ingredients
and Processing Aids
Part 5: Miscellaneous Subjects

Get your copy for a one-time investment of only $85.00!


Practical Latex Technology - 2nd Edition

Please contact john@jwlatexconsultants.com and woonsungliang@yahoo.com.sg if you have problem in downloading the ebook.

Sunday, February 12, 2017

Thickeners for Natural Rubber Latex and Nitrile Latex

Manufacturer: We are manufacturing latex dipped products based on both Natural Rubber latex and NBR (Nitrile) latex. Please advise us on the types of thickeners we can use.
John Woon (Senior Latex Consultant): You can try the following:

1) Natural Colloids
Examples for theses are casein and alginate. Ammonium casienate (10% solution of casein in ammonium hydroxide) and sodium alginate (5 - 8% solution) have been used successfully in the industry. However, these are prone to bacterial attack. I suggest you add some bactericide.

2) Celluloses
Widely used cellulose types of thickeners include methyl cellulose, hydroxy propyl methyl cellulose and sodium carboxyl methy cellolose and their derivatives with chemical modifications. All are used at a concentration of 4 to 6%. They are available in different molecular weights giving different viscosity accordingly.

3) Polyacrylates
Examples are ammonium polyacrylate, sodium polyacrylate and polyacylate acid emulsion. When using the acid emulsion care must be taken to prevent possible flocculation of latex.

4) Water-soluble polyurethane 
This is an alkyl phenol ethoxylates associative polyurethane thickener widely used in the coating industry.

Monday, January 23, 2017

Happy Chinese New Year!

Chinese New Year, also known as Spring Festival in China, is the most important traditional holiday for all Chinese. Chinese New Year 2017 is on Saturday, January 28th, 2017 i.e. the first day of the Chinese lunar calendar.

 Mr. John Woon of JW atex Consultants would like to send his visitors a beautiful Chinese New Year Card. Please view the card in the following link:


Sunday, January 22, 2017

How to Obtain Small Natural Rubber Particles for Textile Impregnation?

Manufacturer: We are manufacturing textile and similar products treated with natural rubber latex. We understand that one of the criteria of good penetration and impregnation of the rubber into the textile is the rubber particle size in the latex i.e. we need small rubber particles.

We have been told that in the normal centrifuged latex concentrates, the inherently smaller rubber particles of the latex have been removed by the centrifugation process. My question is how and where do we obtain such small sized rubber particles which are originally present in the latex?

John Woon (Senior Latex Consultant): Good question! Though it is possible it is costly to recover the small sized rubber particles from the skim after the centrifugation of field latex to obtain the concentrated latex.

Fortunately all is not lost because latex concentrates made by evaporation process are commercially available from Revertex Malaysia (Synthomer). In the evaporation process, only water is removed from the latex hence the inherently present small rubber particles are not removed, unlike the centrifuged latex.

Also, these evaporated latex concentrates have excellent mechanical and compounding stability besides having excellent penetrating property. They are available with 68% and 73% TSC.

How to Minimize Copper Staining While Maintening Dithiocarbamates in the Compound Fromulations

Manufacturer: We are a medium sized factory manufacturing latex thread and other dipped products. In one of our products we would like to minimize copper staining. We also want good heat resistance. However we do not want to replace dithiocarbamate in your latex compound. What shall we do?

John Woon (Senior Latex Consultant): It is not easy to prevent copper staining without removing dithiocarbamates from your latex compound formulations. However, I have the following suggestion to control the staining:

1) Try reducing the level of dithiocarmate to the very minimal while adding a thiazole (ZMBT) as the main accelerator. The reduced level of dithiocarbamate is such that it still gives you reasonable rate of vulcanization and physical properties of the final products.

2) If you are using ZDEC, replace it with ZDBC as the latter has lesser tendency to cause migration staining.

As for heat resistance, you can try sulphur donors such as TMTD, DPTT or Morpholine disulphide in conjunction with thiazoles.

Thursday, December 29, 2016

How to Improve Setting of Latex in Straight Dipping?

Manufacturer: For some technical reason requested by our customer we can't use coagulant dipping. We were advised to use only straight dipping. However we encounter excessive latex flow from the former due to poor setting of the latex in the oven. Do you have any tips to overcome this problem?

John Woon (Senior Latex Consultant): Here are some tips you can evaluate:

1) The latex compound must be well matured before use. I'm assuming you are using post-vulcanisable latex compound.

2) Control the latex compound viscosity.

3) Make the latex slightly heat-sensitive by controlling the formation zinc-ammine complex with ZnO and alkali.

We would like to wish our friends, customers, students and clients "A Very Happy New Year!"

Sunday, December 11, 2016

How to Transfer Latex Without Latex Destabilisation Due to Mechanical Shear

Manufacturer: We are manufacturers of latex products using natural rubber latex. We always encounter coagulum formation problem when we transfer latex from tanks to tanks. Please advise us the best way to transfer latex without latex destabilization problem.

John Woon (Senior Latex Consultant): One could transfer latex from one container to another by using pump, compressed air or gravity. While pumping might destabilize the latex, compressed air and gravity feeding have the least destabilization problem. When using pump, care should be taken to select one that gives the least mechanical shear to the latex.

For compressed air feeding, one must use pressure tested and insured tanks and a supply of clean compressed air. Therefore this more expensive method is mainly used for bulk deliveries of latex.

Transferring latex by gravity is the cheapest and simplest to use while preventing mechanical shear to the latex and therefore the chances of coagulum formation are kept to the very minimum. However the factory layout must be designed in such a way that the storage tanks are located on an upper floor or level to allow the latex to flow down to the compounding tanks situated at a floor lower. From the compounding tanks, the compounded latex is in turn allowed to flow to yet another floor lower for further processing such as dipping, casting or extrusion, etc.

Saturday, November 19, 2016

Natural Rubber Latex - Problem with Dilution with Water

Manufacturer: We are latex gloves manufacturer. We always encounter latex destabilisatiion whenever we dilute our latex compound with water before dipping. This has resulted in high loss and poor processing. Can you explain why?

John Woon (Senior Latex Consultant): One possible reason is the fact that when water is added to the latex compound, the concentration of latex stabiliser present in the water phase is reduced accordingly. Therefore you should add a small amount of the stabliser in the water before using it.

Also, you must prevent "pH shock" to the latex by adjusting the pH of the eater to about 9.50. It is advisable to use deionised or softened water for latex dilution to prevent destabilisation of latex by free calcium and magnesium ions.

Tuesday, October 25, 2016

Discoloration of Rubber Products

Manufacturer: We are manufacturer of latex casting and dipped products for medical applications. Very often, we encounter discoloration of our products. Please advise us how to overcome this problem.

John Woon (Senior Latex Consultant): Discoloration is an unwanted and undesirable change of colour of light-coloured rubber products especially white toy balloons. However, it is very often confused and misunderstood by many latex products manufacturers.

It can be caused by compounding formulation (ingredients), processing and storage or service conditions. Different causative factors would require different remedial actions to overcome them.

The following are the possible factors causing the discoloration of toy balloons:

1) Based Latex

2) Compounding Ingredients

3) Processing (curing and leaching)

4) Storage and Service Conditions

In response to your request, the details have been sent to you separately.



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.