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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Thursday, May 19, 2016

Reducing Ammonia Content of Latex Concentrate with Formaldehyde

Manufacturer: We are manufacturing dipped tubes, for medical in small scale.
Can we add formaldehyde to reduce the concentration of ammonia in high ammonia latex, so that even dip could be produced?
John Woon (Senior Latex Consultant): Yes, you can add formaldehyde to reduce the ammonia content in the latex.When you add formalin to the latex, pH would drop and latex would tend to destabilise. Therefore you need to add a non-ionic surfactant first. Stir for two hours before adding formalin.

You can try Emulvin W or equivalents as the surfactant. If you continue to encounter stability problem such as viscosity rise it could be due to the latex quality problem, in which case I suggest you remove the ammonia by stirring with a fan over the surface of the latex.

Thursday, April 21, 2016

Curatives for the Vulcanisation of Nitril Rubber

Manufacturer: We are manufacturing rubber parts using dry natural rubber (SMR) via compression molding and are about to conduct some trials using dry carboxylated nitrile rubber. We would be obliged if you could give us some guide lines in terms of curatives compounding.

John Woon (Senior Latex Consultant): For general applications, you can used practically the cure systems for both NR and SBR such as thiazoles and sulphenamide cure system. For high temperature applications and also where low compression set is required, both thiuram and peroxide cure systems should be used.

You should also get the advice from the rubber suppliers or manufactueres because the following factors involved in polymerization, etc. are also affecting the vulcanisation of nitrile rubber:

1) Coagulant
2) Emulsifiers and surfactants
3) Polymerization additives
4) Polymer rheology
5) Process aids in polymerization

Friday, April 08, 2016

Blending of Different Latices and Addition of Fillers in Latex Adhesive Compounds

Manufacturer: We are manufacturer of latex-based adhesives. Please give us some general guidance in blending of two different latices and the addition of fillers in terms of latex colloidal stability.

John Woon (Senior Latex Consultant): I suggest you look into the following points:

1) Blending of two different latices (latexes)

1.1) Make sure the pH of both latices are as close as possible. By changing the latex pH, the latex could sometimes be destabilized in which case, it is advisable to add a non-ionic surfactant to that latex before the pH adjustment.

1.2) Latex with smaller particle size would tend to rob the surfactant already present on the particles of latex with higher particle size. Generally, the level of surfactants required for the blend is more than the total amount required for the two individual latex.

2) Filler addition

2.1) You could either add the filler dry or as a pre-prepared slurry to the latex. The former would require higher level of surfactant than the latter.

2.2) The higher the level of filler, the higher is the level of surfactant required.

2.3) Filler with smaller particle size would tend to rob more of the surfactant from the latex particles compared to filler with coarser particles.

2.4) Filler type is important e.g. clay and talc would have less destabilizing effect on the latex compared to calcium carbonate.

2.5) Generally a combination of surfactants performs better than a single surfactant.

Hope this helps.

Tuesday, March 15, 2016

Mechanism of the Leaching Process

Manufacturer: I am the head of the R&D department in a latex dipped products manufacturing company in Sri Lanka. In order for me to understand the importance of leaching, I need to know the mechanism involved during leaching. Can you help?

John Woon (Senior Latex Consultant): Over the years I've studied and analyzed the factors involved in the leaching process so as to achieve the most optimized leaching effectiveness for a variety of dipped products.

I've identified 7 steps which take place in sequence during leaching. I've sent this along with some details of each step to you separately. Please let me know if this is of any help.

Working Off of Old Latex Compounds

Manufacturer: We are using different latex compound formulations for different products. This always results in the built-up of old latex compounds of more than a few weeks old. How can we make use of old latex compounds to minimise wastage?

John Woon (Senior Latex Consultant): Beware of possible problems when using old latex compounds especially when it has already “over-cured” as it would lead to low elongation at break, high modulus and poor tensile strength and hence premature tearing.

You could try to blend this off into new and fresh compound but lab experiments must be carried out to see if the physical properties (i.e. tensile strength, modulus and elongation at break) are acceptable for the ratios of the blending you've selected

Another alternative is to use prevulcanised latex which does not normally over cure on storage.

Sunday, February 14, 2016

Inorganic Polyphosphates for Latex Stability

Manufacturer: We have been advised to use inorganic polyphosphate to enhance the stability of our latex. How does this work?

John Woon (Senior Latex Consultant): Polyphosphates have been used successfully as deflocculating agents for the dispersion of pigments. They have a mild surface active property and are usually added as the alkali salts.

The alkali polyphosphates have the ability to sequest heavy metal ions and are therefore very useful in countering the destabilizing effect of calcium and magnesium ions that might be present in hard water used in diluting the latex.

Monday, January 25, 2016

Inconsistent Physical Property Test Results

Manufacturer: We are latex catheters manufacturer. For the last 6 months, our Q/C department has been having problem of inconsistent test results from our tensile testing. Our latex compound formulation, production processes have not been changed. The test pieces are cut from films prepared using both casting and coagulant dipping methods.

We would appreciate your input on how to ensure that we achieve consistency in our testing.

John Woon (Senior Latex Consultant): Briefly, please ensure the following:

1) The tensile machine is well calibrated especially the separation speed of the clamps.

2) The thickness gauge is working properly and frequently calibrated.

3) Die cutter must be sharp enough to ensure that there is no jagged edges of the test pieces after cutting.

4) The rubber films are free of micro-flaws caused by air trapped, collusion of dirt, dirty formers or casting plates, etc. (Thicker films could be a better choice)

5) The test pieces must be well conditioned in the testing room at consistent relative humidity and temperature.

6) There is no slippage of the test pieces from the clamps/grips during testing.

Generally, a higher range of results such as tensile strength is more accurate and acceptable than a lower range of results which could be due to any or a combination of the above mentioned factors not being under control.

Saturday, January 23, 2016

Poor Solvent Resistance of Products Made from Prevulcanised Latex

Manufacturer: We are manufacturers of a wide variety of latex products using prevulcanised NR latex. We have been doing quite well until recently when one of our customers complained that one of our products had poorer resistance to solvent compared to a competitive product which is also made from NR latex. Your comment and advice please.

John Woon (Senior Latex Consultant): Unfortunately your customer's complaint could be justified. Owing to the structure of the rubber of a prevulcanised latex film with weaker particle to particle integration, the film has inferior resistance to oils, greases and non-polar solvents when compared with a film of the same thickness but made from a post-vulcanisable NR latex compound.

Therefore, unlike post-vulcanised film, a prevulcanised film would easily rupture when solvent is dropped onto it while being stretched.

I believe your competitor's product is made from a post-vuclanisable NR latex compound. Your problem could be overcome or minimised if you could introduce some post-vulcanisable latex compound into your prevulcanised latex.

Having said this, you must take note of the fact that natural rubber has comparatively poorer resistance to oils, greases and non-polar solvents compared to Nitrile and polychloroprene rubbers and should not be used in applications where the finished products are to be exposed to such liquids.

Friday, December 18, 2015

PVC Plastisol Sticking to Substrates

Manufacturer: We are using PVC plastisol for casting and dipping for various products including gloves. Our problem is the occasional tendency of the products to adhere to some substrates such as the moulds. What shall we do?

John Woon (Senior Latex Consultant): Plasticized PVC does have some inherent tackiness problem. I suggest you add some lubricants to the compound such as metallic stearates, stearic acid, waxes and silicone. These should improve your demoulding process.

Thursday, December 17, 2015

JW Latex Consultants would like to wish our clients, customers, students, friends: "Merry Christmas and Happy New Year!!

Heat Sensitivity of Latex Compound

Manufacturer: We have been having difficulty in controlling the heat sensitivity of our NR latex compounds resulting in variation in product thickness, etc. We are now in the process of developing new compounds with improved heat stability.

We would appreciate it very much if you could suggest a simple lab method for us to measure the latex heat sensitivity.

John Woon (Senior Latex Consultant): You can evaluate the heat sensitivity of
your latex compounds by measuring the increase in viscosity when the latex compound is subjected to an extended period in an oven at, say, 35 to 40°C at a given latex TSC and pH. The temperature used would depend on the latex compound formulation.

Other tests we could carry out include MST and coagulum content (including micro-coagulum).

Thursday, November 19, 2015

Non-ionic Surfactant for Natural Rubber Latex Comppounds

Manufacturer: We are looking for a suitable non-ionic latex stabilizer for one of our heat sensitized natural rubber latex compounds. There are so many variations of such stabilizer in the market making selection a nightmare to us. We would appreciate if you can suggest one suitable grade for our work.

John Woon (Senior Latex Consultant): You should try evaluating an alkylphenol ethylene oxide condensate containing about 30 moles of ethylene oxide/mole.

wherein R comprises 8 to 14 C atoms and x varies from 1 to 40 moles

Thursday, October 29, 2015

Polychloroprene Latex as a Substitute to Natural Rubber Latex?

Manufacturer: We understand that some manufacturers have switched from natural rubber latex to polychloroprene latex despite the higher price of the latter due to protein allergy problem associated with natural rubber latex.

What are the typical properties of vulcanisates from polychloroprene compared to natural rubber?

John Woon (Senior Latex Consultant): Generally, polychloroprene rubber has the following superior properties, especially when compared to natural rubber:

1) Excellent resistance to ozone attack.
2) Good ageing resistance.
3) Low gas permeability
4) Good chemical resistance especially against non-polar solvents.
5) Good flame retardant.

While the modulus and elongation at break are similar to that of natural rubber, the tensile strength and tear strength are slightly inferior. 

Sunday, October 25, 2015

Cyclohexylamine Acetate as Coagulant?

Manufacturer: We heard that you had recommended the use of cyclohexylamine acetate as a coagulant for some latex dipped products. Can you please tell us why?

John Woon (Senior Latex Consultant): Usual coagulant such as calcium nitrate would result in poor transparency since it is insoluble in rubber.

One unique coagulant that has been successfully used for many years for the manufacturing of high-clarity (i.e. transparent) baby teats and soothers is cyclohexylamine acetate (CHA).
The main reason for the transparency is that CHA and its by-products are soluble in rubber.

Wednesday, October 21, 2015

New Market Report on Chinese Disposable Rubber Examination Gloves Industry

ReportBazzar has announced a new report titled “China Disposable medical rubber examination gloves Industry 2015 Market Research Report.".

The China Disposable medical rubber examination gloves Industry 2015 Market Research Report is a professional and in-depth study on the current state of the Disposable medical rubber examination gloves industry.

The report provides a basic overview of the industry including definitions, classifications, applications and industry chain structure. The Disposable medical rubber examination gloves market analysis is provided for the China markets including development trends, competitive landscape analysis, and key regions development status.

Development policies and plans are discussed as well as manufacturing processes and Bill of Materials cost structures are also analyzed. This report also states import/export consumption, supply and demand Figures, cost, price, revenue and gross margins......CLICK HERE to read more.

Saturday, October 10, 2015

Plastic-Eating Worms May Offer Solution to Our Growing Garbage Problem

Polystyrene—most familiarly produced as foams, including Styrofoam—has given the world cheap, lightweight insulation and containers for taking food to go. But the material biodegrades so slowly that it can sit in a landfill for hundreds of years. A new finding points to a potential solution: Mealworms will dine on polystyrene foam when they can’t get a better meal, converting up to 48% of what they eat into carbon dioxide......CLICK HERE to read the whole article.

Thursday, October 01, 2015

Get Your Copy of - "Practical Latex Technology" Now!

"Practical Latex Technology" contains answers to more than 100 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!

NOTE: If you do not receive the book online immediately after making your payment, please contact John Woon at woonsungliang@yahoo.com.sg and john@jwlatexconsultants.com and he would ensure that the book is sent to you without undue delay.

Sunday, September 13, 2015

Heat Sensitized Natural Rubber Latex

Manufacturer: One of our suppliers suggested that we should try Emulvin W and Coagulant WS from Lanxess to make our NR latex compound more heat sensitive in order to make thicker latex dipped products. We would appreciate if you could guide us on how to proceed.

John Woon (Senior Latex Consultant): Emulvin W ia a surface active agent (i.e. surfactant) which is an aromatic polyglycol and is normally added into the latex compound to improve the colloidal stability of the latex against mechanical shear and cationic chemicals. Although it appears oily it can be easily dissolved in water. I suggest you prepare a solution of about 20% before use.

Coagulant WS is a functional organosiloxane that is frequently used as a heat sensitizerfor latex compounds. While Coagulant WS reduces the "coagulation temperature" Emulvin W increases it.

Hence when Coagulant WS is used in conjunction with Emulvin W, the "coagulation temperature" of the latex compound could be changed to suit one's dipping process and also to control the thickness of the latex gel by varying the ratio of these two additives.

The advantage of Coagulant WS is the fact that it is silicone based (although water soluble) and hence it could also act as a releasing agent.

Thursday, September 03, 2015

Training on Latex Technology.

Manufacturer: Please let me know if you do training on latex filming or general training on latex so that I can participate in near future.
Do you have any consultation fee or package system so that I can go through and work out more concerns in latex in a systematic way. Please let me know.
I look forward to hearing from you.

John Woon (Senior Latex Consultant):  I do conduct training on latex technology.

This can be done face-to-face or if required I can also put this into a pdf report for you. This covers the basic science and technology of natural rubber latex, latex specification and the significance of each parameter, latex stability, lab testing and many more topics.

The report would serve as a good reference guide for your work with natural rubber latex.

Tuesday, August 18, 2015

"Precure" and "Maturation" of Natural Rubber Latex Compounds

Manufacturer: We are latex dipped products manufacturers using natural rubber latex. We are confused by the terms, "Precure" and "Maturation". What do they mean in technical terms and how important are they?

John Woon (Senior Latex Consultant): Good questions. Both the terms "Precure" and "Maturation" are quite loosely used in the latex industry. Even some of the qualified latex technologists and scientists interchange one with the other to mean the same thing.

The two terms actually mean two different things. "Precure" means a certain degree of prevulcanisation or cross-links that has taken place while "Maturation" is the state of surfactants initially present in the base latex and those added through compounding and other ingredients having reached an equilibrium usually accompanied with an increase in colloidal stability.

Both precure and maturation are taking place at the same time immediately after compounding.

Both are necessary to ensure successful dipping with good colloidal stability and good gel strength with minimal or no product distortion and eventual acceptable tensile strength.

Sunday, July 26, 2015

Study of Effects of Surface Tension in Latex Dipping Process

Manufacturer: We are manufacturers of a varied range of latex dipped products. We believe we are having some wetting problems with our coagulants and latex and would like to use surface tenstion measurement for our initial work. What should we do?

John Woon (Senior Latex Consultant): I suggest you study the effect of both the "Equilibrium Surface Tension" based on Du Nouy Ring and Wihelmy Plate methods and the "Dynamic Surface Tension" by maximum bubble pressure. (Kyowa Interface Science Co., Ltd. gives the following illustration)


Dynamin surface tension is particularly useful in understanding its effect in a dynamic system such as that experienced by you in your dipping process, where new interfaces are rapidly encountered.

Your surfactants suppliers should be able to give you more details.

Sunday, July 12, 2015

Freeze-Thaw Stability of Natural Rubber Latex Concentrates

Manufacturer: We are using centrifuged latex concentrates from Thailand and very often encountering latex stability problem during winters. Can you explain why and how we can ensure better freeze-thaw stability of the latex.
John Woon (Senior Latex Consultant): If you are storing your latex just above freezing temperatures, the colloidal stability of the latex is normally still acceptable. But once the water phase of the latex is frozen at sub-zero temperatures, latex destabilization would occur with an increase in viscosity and a drop in mechanical stability even after the latex has been thawed.

The frozen of the water phase would force the latex particles to collide and adhere with each other and hence destabilization. In severe cases, this would lead to irreversible coagulation and gelation.

The good news is that freeze-thaw stabilized centrifuged latex concentrates are available from the latex producers if such requirement is specified by the buyers. The improved stability is normally done through the addition of sodium salts of certain phenolic additive and ammonium laurate soap.

Thursday, June 25, 2015

Fraunhofer Researchers Develop Natural Rubber from Dandelions

Approximately 40,000 products of everyday life contain natural rubber. It’s the material that provides extreme elasticity, tensile strength and low-temperature flexibility in products from mattresses and gloves to adhesive tape and tires. As yet, it has no artificial replacement. However, researchers from the Fraunhofer Institute for Molecular Biology and Applied Ecology IME were able to identify a cost-effective and eco-friendly alternative to the natural rubber tree: the dandelion.....CLICK HERE to read the whole article.

Sunday, June 14, 2015

Latex Stability Problem Due to Addition of Filler

Manufacturer: We are adding filler to our latex compounds to reduce cost while increasing modulus. However, every time we do this we encounter a lot of problems due to a drop  in latex stability.


John Woon (Senior Latex Consultant): You did not tell me your stabilizing system and how much stabilizer you are using. The problem you encountered is due to the fact that the stabilizers of the rubber particles are being "robbed" by the filler.

As a general rule, the level of the stabilizer (i.e.surfactant) added should be proportional to the quantity of filler added. Also, the level of stabilizer added in the form of a aqueous dispersion (or slurry) is lesser compared to the case when the filler is added as dry powder.

You should also take note that the lower the particle size of the filler, the higher is the level of the surfactant required.

Sometimes a blend of more than one surfactants works better than when only a single surfactant is used.

Saturday, June 13, 2015

Latex Thread Manufacturing - General Advise

Manufacturer: We are medium sized latex thread manufacturer just beginning production. We're still struggling to get optimization of the production process. A general comment from you would be highly appreciated.

John Woon (Senior Latex Consultant): "A general comment" is far from adequate as the latex thread extrusion is a complex process.

Anyway, here's my general advise:

1) The particle size of your compounding chemicals should be free from coarse particles especially for thread of smaller diameters. It should be below 3 micron.

2) The latex compound must be well matured at room temperature for a number of days depending on your cure recipe. This must then be followed by high pressure homogenizing,  deaeration under vacuum and filtered before use.

3) Dry and cure at between 15 to 20 minutes at 125°C to 130°C. You can also try a shorter cure at higher temperature followed by post curing at lower temperature at about 70°C.

If you need my full report on the "Manufacturing of Latex Thread", please let me know. 

Saturday, May 23, 2015

Transparent Rubber Shoe Soles

Manufacturer: We are manufacturer of rubber parts for the construction of shoes. Our latest project is to develop a suitable compound for transparent rubber shoe sole based on natural rubber with good abrasion resistance. I understand from others in the rubber industry that you could help us in terms of choice of rubber and additives.

John Woon (Senior Latex Consultant): You should start with pale crepe as your base rubber. To have reasonable abrasion resistance, a good choice of filler is precipitated silica since you cannot use carbon black. For better processibility and molding in terms of rheology, magnesium carbonate could help. Light coloured mineral oil would also improve the transparency.

Wednesday, May 20, 2015

Rough Surface of Extruded Staioners' Rubber Bands

Manufacturer: We are manufacturing stationers' rubber bands using dry rubber extrusion process but have been experiencing undesirable surface roughness persistently. All attempts in reformulation and process changes are to no avail. Hope you can help us. We've sent you our formulations.

John Woon (Senior Latex Consultant): Thanks for sending me your formulations which helped me in my diagnosis of your problem.

You can easily overcome the problem by either switching your SMR to SP 20 of blending both.
SP means "Superior Processing Rubber" made form mixing vulcansied latex with normal latex at different ratios before the latex blend is coagulated to obtain the dry rubber. It has superior processing characteristics and good dimension stability which are ideal for calendering and extrusion processes. The extrudates would also show a smoother surface.

SP 20 indicates that 20% of the latex blend is vulcanised latex.


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.