JW Latex Consultants (and Rubber Consultants) 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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Sunday, July 27, 2014

What Solvents Are Best for What Polymers?

Manufacturer: We are manufacturer of water-based adhesives. In response to some customers' request, you are now also looking at manufacturing some solvent based adhesives. We have some polymers in mind such as PVC, EPDM, ABS, NBR, etc. Can you advise us what solvents are best for which polymers?

John Woon (Senior Latex Consultant): Please check out my earlier post titled
"Use of Solubility Parameters in Solvent Based Adhesives" posted on 22 June 2014.
For the list of polymers against their possible solvents, please check out this link => http://goo.gl/p5WhQF

Friday, July 25, 2014

At What Temperatures Should Natural Rubber Latex be Stored?

Manufacturer: Under what temperature condition should natural rubber latex concentrate and prevulcanised latex be stored. We are from a temperate country.

John Woon (Senior Latex Consultant): Heat would increase the kinetic energy of the rubber particles resulting in the increase of both the frequency and violence of collisions among the rubber particles which could result in the formation of coagulum.  Heat would also evaporate water and drive away the ammonia in the latex with the accompanying drop of pH and skin formation on the surface of latex.  Drop in pH would also lead to latex destabilisation.On the other hand the stabilising system within the latex could be rendered ineffective when the latex is subjected to freezing temperature.  Hence latex must be protected from frost. The latex is therefore best kept in-door at a storage temperature of between 10 to 30°C.

If latex is stored for more than 6 months, some minor adjustment by adding some soap stabiliser might be required.  Excessive loss of ammnoia in storage tanks and partially emptied drums should be prevented as this could lead to destabilisation of latex ( e.g. if pH has dropped to below 10.0, ammonia solution should be added to bring it to about 10.5).

The latex should be agitated at slow rate periodically to prevent excessive creaming.

Monday, June 23, 2014

New Hydrogel Condoms ‘More Like Human Skin'

WOLLONGONG, AUSTRALIA - Latex could be replaced as the primary material in condoms.
Researchers at the University of Wollongong in Australia who were awarded a grant from the Bill & Melissa Gates Foundation are furthering research into substances called tough hydrogels, which are currently used in medicine and robotics.

“We hope to deliver a condom that is safe and feels and looks better,” a UW release states. “It’s designed to feel more like human skin than latex rubber.”

The research team touts other benefits of hydrogel condoms, including invisibility and self-lubrication.
“That would eliminate problems with latex allergies and improper use of oil-based lubricants,” according to the release.

Dr. Sina Naficy, a polymer scientist working on the project, said the so-called “next generation condoms” could also be more environmentally friendly because the hydrogels are mostly made of water.
“Hydrogels can also be made to be biodegradable, which solves the problem of condom disposal,” according to the release........CLICK HERE to read the whole article

Sunday, June 22, 2014

Use of Solubility Parameters in Solvent Based Adhesives

Manufacturer: We are manufacturing water based adhesives based on PVac and natural rubber latex. Recently we have decided into venture into solvent based adhesives due to the response to market requirement of our customers. We were advised to look into "solubility parameters" of both polymers we used and the available solvents to determine what solvents are best for what polymers.

What is "solubility parameters" anyway?

John Woon (Senior Latex Consultant): To cut the long story short, solubility parameter is a numerical estimate of the degree of interaction between materials (e.g. solvent with solvent or solvent with polymers), which indicates how good is the miscibility or solubility of the different materials when mixed together. Materials with similar values of "solubility parameter" are likely to be miscible e.g. a polymer with similar solubility parameter of its solvent would be easily dissolved in that solvent.This makes your life so much simpler when you want to choose a suitable solvent for your polymer such as polychloroprene and natural rubber.

To understand fully the chemistry/physics involved, one has to consider Van der Waals forces, cohesive energy density and heat of vaporization of the materials.

The theory behind solubility parameter was proposed by a renowned chemist and scientist, Dr. Joel Henry Hildebrand (November 16, 1881 – April 30, 1983) hence the term "Hildebrand solubility parameter" is often used.

Friday, June 20, 2014

Controlling of Baby Soothers Thickness with Heat Sensitized Latex

Manufacturer: We are manufacturing baby teats and soothers (pacifiers) with heat sensitized latex compound. We find controlling the product thickness of the soothers to be very difficult. We hope you can give us some practical tips to overcome this problem.

John Woon (Senior Latex Consultant): There are so many factors involved in this dipping process that could lead to inconsistent thickness of your products. Briefly, some of these factors are as follows:

1) Latex pH must  be closely controlled and monitored before and after the addition of the heat sensitizer.
2) Former temperature should be high enough to ensure good pick of latex but must be well controlled so that a latex dwell time of only a few seconds should suffice.
3) Latex temperature should be at around 20°C and must not vary for more than 1°C.
4) Prevulcanised latex offers better control of product thickness compared to post-vulcanisable latex compounds.

If you want I can prepare a detailed report for you.

Friday, May 30, 2014

Differences between SBR Latex and Carboxylated SBR Latex?

Manufacturer: Can you explain the main differences between a standard SBR latex and a carboxylated SBR latex for carpet backing and treatment of textile and non-woven fabrics? Why is carboxylated SBR latex a preferred latex?
John Woon (Senior Latex Consultant): The first important property I would like to touch on is the latex colloidal stability. In the case of non-carboxylated SBR latex, the stability is achieved through the addition of surfactants which could be easily "desorbed" from the rubber particles and hence leading to destabilization.

On the other hand, in a carboxylated SBR latex, the carboxylic acid is an integral part of the polymer through copolymerization and by virtue of its ability to ionize, it offers a more permanent stability to the latex.

Briefly, carboxylated SBR latex also offeres the following advantages:

1) Improved wetting for fillers and fibres
2) With improved polarity, adhesion to many substrates is enhanced
3) Improved physical properties (e.g. tensile strength, abrasion resistance, modulus)
4) Improved chemical resistance to non-polar solvents

This question had been raised before in this "forum". Please go to the link below:

Solvent Roughening of Household/Industrial Gloves

Manufacturer: We have been trying to make roughened (kinkled) latex household/industrial gloves with methylene chloride in response to the request of one of our customers but without success.Would appreciate very much if you could guide us in solving this problem.
John Woon (Senior Latex Consultant): I presume you want to make gloves with irregular patterned surface on the outside of the gloves.

This entails careful selection of solvent and coagulant, time of immersion, filler content and the degree of prevulcanization of the latex compound.

It is a complex optimization of all the factors mentioned above. If you want , I could write a separate report for you with more technical details.

In the mean time, I suggest you replace methylene chloride with toluene.

Wednesday, April 30, 2014

Fire Retardant Polychloroprene

Manufacturer: Why is polychloroprene preferred to natural rubber for fire retardant products in the transport industry?
John Woon (Senior Latex Consultant): Since polychloroprene is halogenated i.e. containing chlorine atoms (or Organohalogen compounds), it has good fire retardancy. 

Therefore, unlike natural rubber, when polychloroprene rubber is burnt with a Bunsen burner or a lighter, it will burn but extinguishes itself (i.e. self-extinguishing) immediately once the lighter is removed whereas natural rubber would continue to burn. This is one reason why polychloroprene is used in place of natural rubber in many products, particularly in the building and transport industries (e.g. seating cushions) due to safety reasons. You can therefore “label” your products as “Fire-retarding “or “Fire retardant”. 

Thursday, April 17, 2014

Thickener for Natural Rubber Latex Adhesives

Manufacturer:  I have a very small business related to rubber latex and I am based in West Bengal district of India. My work involves making rubber latex (centrifuged, 60% DRC) thick for adhesive applications.

In the process, first I prepare a solution using thickeners such as CMC, PVA, Sodium alginate etc. But I have not yet achieved the desired success with the help of these chemicals.

Last week, I came in contact with your website and found a reference of SODIUM POLYACRYLATE. Now, I request you to please suggest me whether I can make a thick solution with the help of Sodium Polyacrylate and water (Cold or Hot?) and whether this solution can be added to latex.

I do hope that you would be kind enough to address my query and send me a solution that might help me improve my work.
John Woon (Senior Latex Consultant): Yes, you can try "Polyacrylate" type of thickener. Sodium polyacrylate is quite widely used.

This should be readily available either already in solution form or powder form or the polyacrylic acid which you have to react with sodium hydroxide. These should be available in India.

You can prepare a 1 to 5% solution by dissolving sodium polyacrylate powder in warm water with stirring. The powder should be added in small quantity slowly and gradually to prevent lumping.

Talk to your suppliers who can further advise you on how to use this for latex.

In addition, you can also add about 5 phr of bentonite clay.

Monday, March 17, 2014

Secrets to Succesful Dipping for Toy Balloons

Manufacturer: We are toy balloons manufacturer who have just started commissioning our new dipping dipping line. We would appreciate very much if you could guide us on the "Do's and Don't's" on how to produce good quality balloons. Our full dipping parameters and video clips of our process have been sent to you.

John Woon (Senior Latex Consultant): Thanks for the dipping parameters and video clips which are very helpful for me to understand your process. Obviously, there are a lot of rooms for improvement in your process.

As requested by you, my full report has been sent to you separately but only a summary of the content is revealed in this "forum".

The following are the areas you need to concentrate on:

1) How to Overcome Latex Quality and Stability Problem 
- You need to know how to assess the suitability of centrifuged latex concentrate 

2) Importance of Prevulcanized latex vs Post-vulcanisable latex
- How to produce and handle both these latices

3) Types of Plasticizer to Be Used for Making the Balloons Softer
- Techniques on how to prepare the plasticizer

4) The Dipping Parameters
- The "Secrets" you need to know from formers cleaning stage to final stripping and drying stages

5) Analysis of Balloon Defects and How To Overcome Them
- Some examples of defects frequently encountered by manufacturers include the following:

Thin patches/uneven latex pick-up
Horizontal lines (Striation)
Fish-eyes and windows
Bubbles at bottom of balloons
Fungus growth
Premature bursting/popping
Balloons becoming stiffer on storage
Balloons sticking together 
Tearing of balloons
Blemished surface
Specky particles
Vertical lines with windows and particles
Star-like particles
Vertical lines along the folds

Crystallization and Gel Content of Polychloroprene

Manufacturer: We are using polychloroprene latex (e.g. Neoprene) for making latex dipped products including gloves. We have been advised to consider the "crystallinity" and "gel content" of the polymer in order to select the right grades for the right jobs. Can you tell us how these two properties can affect the properties of my finished products?

John Woon (Senior Latex Consultant): Generally, as you increase the level of "crystallinity" or "crystallization rate", you get the following effects:

1) Cohesion strength, modulus and hardness would increase
2) Elongation, hot oil swell, resistance to permanent set would drop

As you increase the level of "gel content", you get the following results:

1) Cohesive strength, modulus, resilience, resistance to permanent set would increase
2) Elongation, dry tack and hot oil swell would decrease

You should use this information as a guide in conjunction with the curative recipe design to get the optimized final physical properties required for your products.

Thursday, March 06, 2014

Get Your Copy of "Practical Latex Technology"

The 128-paged book, "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.

Monday, February 24, 2014

Storage Conditions of Natural Rubber Products

Manufacturer: We have just received a complaint from one of our major customers regarding the shelf-life of our natural rubber products in their warehouse. We have investigated our formulation and manufacturing process and found that both are already at their optimum levels. Careful design and curatives and antioxidant system had been adhered to. We would appreciate if you could offer further assistance.

John Woon (Senior Latex Consultant): Maybe you should help your customer by advising them on the conditions of storage for your products.

Rubber products can normally be stored for many years without any loss of their inherent properties provided the following precautions are taken:

1) Do not deform the products to prevent stressing the rubber.
2) Do not expose the products to elevated temperatures for long period. If possible do not exceed 35C.
3) Do not expose the products to light i.e. direct sunlight and artificial light. If possible store the products in the dark.
4)  The products should be properly wrapped and covered also to minimize exposure to air (oxygen) and ozone. Ozone is particularly harmful. The warehouse should not have any electrical equipment that can generate ozone such as high-voltage equipment, electric motors and mercury vapour lamps.
5) Excessive humidity and moist condition especially due to condensation should be avoided.
6) Do not allow the products to come into contact with brass, copper, iron, solvents, oil, greases, etc.
7) Do not unduly store the products for too long by ensuring the stocks are used in rotation.

Sunday, February 16, 2014

Zinc Oxide in Natural Rubber Latex

Students: We are a group of students studying the effect of ZnO in ammoniated natural rubber latex concentrate. We hope you could help us with some information on the solubility of ZnO in natural rubber latex especially the effect of pH.
John Woon (Senior Latex Consultant): I am assuming you are already familiar with the phenomenon of "ZnO thickening due to Zinc-amine complex".

Studies had been done on the factors controlling the solubility of ZnO in Hevea natural rubber latex using model solutions containing ammonia and ammonium salt at a given pH. It had been found that the solubility of ZnO in the latex is proportional to the total concentration of ammonia and ammonium salt.

Also, at a constant concentration of free ammonia and ammonium ions, maximum solubility of ZnO can be achieved at a pH of 9.5.

Tuesday, February 04, 2014

European Commission Backs ECHA on Phthalates in Toys

The European Commission has concluded that the use of high molecular weight phthalates in certain toys and childcare products poses no risk to infants. The findings, which also include adult sex toys, are in line with the conclusions presented last August by the European Chemicals Agency (ECHA).

Based on ECHA’s assessment, the Commission has concluded that “no unacceptable risk has been characterised for the uses of DINP and DIDP in articles other than toys and childcare articles which can be placed in the mouth”. The Commission further concluded that “in the light of the absence of any further risks from the uses of DINP and DIDP, the evaluation of potential substitutes has been less pertinent."......CLICK HERE to read more

Monday, January 27, 2014

Happy Chinese Lunar New Year!

For those who are celebrating the Chinese New Year of the Horse on Friday, January 31, we would like to wish you,


"A Very Happy and Prosperous Chinese Lunar New Year"

Sunday, January 26, 2014

Why Can't We reinforce Latex Products with Reinforcing Fillers?

Manufacturer: We are manufacturing rubber products using both natural rubber latex and dry rubber such as SMR 10 and SMR 20. To improve the strength of our products, we usually add reinforcing filler such as carbon black and silica. However we find that this only works with dry rubber compounds and not the latex compounds. Why?

John Woon (Senior Latex Consultant): In dry rubber compounding and mixing, one has to masticate the rubber either in a 2-roll mill or an internal mixer such as Banbury before other additives such as curatives could be added and homogeneously mixed. In the process of mastication, rubber molecules are broken down with the formation of free radicals which would initiate the chemical bonding with the reinforcing fillers especially carbon black. The following diagram shows how a dry rubber compound is being mixed in a two-roll mill:
The difference in the speed of the two rolls results in the required shear force for the mastication of rubber.

No such free radicals are produced in normal latex compounding and hence no significant reinforcing can be achieved with fillers as in the case of dry rubber compounding although in some cases, there could some marginal improvement in tear strength..

Stability of Carboxylated SBR Latex

Manufacturer: How do we stabilize the carboxylated SBR latex compared to normal SBR latex? We do use high loading of filler (e.g. calcium carbonate).

John Woon (Senior Latex Consultant): Compared to standard SBR latex, carboxylated SBR latex generally offers better chemical and mechanical stability due to the carboxylation.

Hence, no extra stabilizer is required to be added at your end unless it is to be blended with other latices with different pH range. Please note that some soaps (stabilizers) are most efficient in the pH range of 8.0 - 9.5 while others are workable only outside this range.
You need to check with your supplier to confirm this.

It is advisable to premix your filler with a chelating agent or similar phosphate type of dispersing agent before use.


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.