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]


You Are Visitor Number:

Expedia Promotional Codes


This Site Is Best Viewed With Mozilla Firefox Browser. If You Are Viewing With Internet Explorer, It Is Advisable to Switch to Mozilla Firefox By Going to This Link -> http://www.mozilla.org/en-US/firefox/new/

It Is Free to Download


Send Your Enquiry and Orders To: woonsungliang@yahoo.com.sg

Problem Solving Through E-Mails with John Woon Latex Consultants Is Possible


Please kindly donate to support the maintenance of this site. We'd appreciate it very much.



Tuesday, January 30, 2018

What’s In Store For The Cyber Threat In 2018?

Is your organization safe from Cyber attack?

For more information on how your organization can be protected from cyber attack, please CLICK HERE.

Wednesday, January 24, 2018

Shelf-life of Natural Rubber Latex Compounds without Zinc Oxide

Manufacturer: For some of our latex products that require maximum degree of transparency, we have developed some recipes without the addition of ZnO using both zinc and sodium salts of dithiocarbamates as the accelerators. We found that the shelf-life (by measuring precure) of the compounds having Zinc dithiocarbamates had shorter shelf-life compared to the sodium salts. Why is this so?

John Woon (Senior Latex Consultant): The reason is obvious. Zinc dithiocarbamates, although in the absence of ZnO, do release sufficient amount of zinc ion to activate the vulcanization. Also, the soluble sodium dithiocarbamates are weaker accelerators comparatively.

Do be aware that some of the water soluble accelerators would be lost during the leaching process. Therefore you have to adjust their level of addition accordingly. Also, I suggest you add some Zinc carbonate otherwise you might not get sufficient cure.

Wednesday, December 27, 2017


JW Latex Consultants would like to wish all our students, customers, clients and friends:

"A Very Happy and Prosperous New Year, 2018!"

Tuesday, December 19, 2017

What Causes the Odour of Natural Rubber?

Manufacturer: We are rubber products manufacturers using both synthetic dry rubber and latex. Recently, in response to customers' request, we started using natural dry rubber, especially the brown crepe. Compared with synthetic rubbers, natural rubber has a comparatively more objectionable odour. What causes this odour and what can we do to minimise it?

John Woon (Senior Latex Consultant): Actually, the rubber constituent i.e. polyisoprene of natural rubber itself is odourless. The smell comes from the "non-rubber" constituents, especially the protein. The degree of such odour depends on the production processes involved from the tapping of the tree to the final conversion into the dry rubber in the form of bales. The lower quality rubber made from cup lumps, field coagulum and scrap rubber resulted from the original latex coagulating naturally instead of the deliberate coagulation done in the factory, generally give stronger smell. The higher the extent of washing in the factory, the lower is the extent of odour due to the removal of the non-rubbers by the water.

Skim block usually has more objectionable odour because it contains greater amount of non-rubbers. You should insist on good quality Standard Malaysia Rubber with low volatile matter.

Having said that, the smell is lesser for the finale finished vulcanised products. If your customers still find your products unacceptable due to the residual odour, you can mask it with deodorants.

Wednesday, November 22, 2017

Effects of Detergents on Latex Dipped Products

Manufacturer: We are manufacturing re-usable latex dipped products which sometimes must be washed with detergents after use. We observed that some of these products had poorer ageing resistance after such washing e.g. increasing in tackiness, loss in tensile strength, etc. Your advise on how to overcome this problem would be highly appreciated.

John Woon (Senior Latex Consultant): This could be due to the extraction and/or destruction of the antioxidants and some residual dithiocarbamates during washing in the presence of water. Hence the choice of antioxidants and dithiocarbamates or accelerators both in terms of type and level are of utmost importance. In addition, an EV (Efficient Vulcanisation) system is superior to conventional sulphur curing system.

A separate detailed report with my recommended latex compound formulations had been sent to you.

Wednesday, October 18, 2017

What Happens to TMTD in LATZ Latex Concentrate?

Manufacturer: One of our customers is concerned about TMTD (Tetramethylthiuram Disulphide) used in the production of LATZ low-ammonia centrifuged latex concentrate and requested that we monitor the presence of TMTD in the latex. However, from our analysis we observed a declining of the level of TMTD with storage time. Some batches even show negligible level. Please explain why.

John Woon (Senior Latex Consultant): LATZ is preserved with low ammonia at 0.3% with secondary preservatives in the form of TMTD and ZnO at 0.025% each.

TMTD at this level is considered to be low when compared with TMTD used as an accelerator (at up to 1.0%) for vulcanization. Malaysian Rubber Products Research Association in the UK had done some work in the past and found that TMTD in LATZ gradually (over time) breaks down into ZDMC (Zinc Dimethyl Dithiocarbamate) and other sulphur-containing compounds.

One interesting finding was the fact that the preservation of the latex  was not affected with the "loss" of TMTD.

Saturday, September 16, 2017

Zinc Oxide Thickening of Natural Rubber Latex Compound

Manufacturer: We are manufacturers of latex dipped products such as gloves and frequently encounter latex stability problems such as increased viscosity in compounds having higher level of ZnO. Among other things, we intend to add non-ionic attractant to counter the thickening of the latex. What possible side effects do you think this strategy would give us?
John Woon (Senior Latex Consultant): What you are encountering is what is commonly referred to as "Zinc Oxide Thickening". Non-ionic surfactants of the polyethylene oxide condensate type could help reduce the thickening. This is usually added in conjunction with KOH to maintain a high pH while the use of ammonia is restricted to minimize ammonium salt formation.

However, you must take note of the following negative side effects:

1) It would slow down gelling of latex and hence reducing latex pickup in coagulant dipping process.

2) It affects the gelling of latex extrudate for latex thread manufacturing and hence retarding the formation of solid filament.

3) Some non-ionic surfactants could reduce the mechanical stability of the latex resulting in the formation of coagulum.

Wednesday, August 16, 2017

Breaking and Tearing of Condoms During Use

Manufacturer: We have a serious problem with our condom which is produced by our company. Our lines are from RT and we use PV latex. The problem is the broken and tearing condoms sometimes by our condom users through sexual process. I send you pictures and video for our condom. Please send us your comments and suggestion that how to solve our condom quality problem.

John Woon (Senior Latex Consultant): From your photographs and the samples you sent me, the defects of the condoms could very likely be due to the presence of micro-air bubbles, foreign particles and unknown contamination of the latex. Care should be taken to minimize the formation of air bubbles during the transferring and mixing of the latex. Any air bubbles present should be eliminated before dipping. Ensure that the film of the rubber is at its maximum physical strength by the various stages of the dipping process.

Ensure that all particles of chemicals used in the latex compound are well milled and dispersed. Introduce some Q/C tests to detect possible contamination of the latex which can occur either at your factory or your supplier's factory.

Also, although prevulcanised latex (PV) is being used, sometimes the cure state of the PV can still advance on storage. Therefore it is advisable that you measure the cure state during the cause of the storage and processing of the PV.

Saturday, August 05, 2017

The Meaning of "Creep" of Rubber Products

Manufacturer: We just received a complaint from one of our customers stating that one of our rubber products has shown excessive "creep" property. What is this? We would appreciate your usual good explanation.

John Woon (Senior Latex Consultant): Very simple. "Creep" has a lot to do with "Stress Relaxation". Most people are familiar with the latter but not the former.

Stress relaxation of a vulcanised rubber refers to the loss in stress when the rubber is held at constant strain (e.g. at a given elongation), over a period of time. Closely related to stress relaxation is "Strain Relaxation".

Strain relaxation of a rubber product refers to the gradual increase in deformation (e.g. elongation) under constant load, over a period of time.

"Creep" is another term for "Strain Relaxation". I suggest you review your curative recipe and try to use an EV (efficient vulcanisation) system as far as possible.

Sunday, July 23, 2017

Choice of Coagulant for Maximum Transaprency in Latex Dipped Products

Manufacturer: With your help, we have managed to modify our latex compound formulations to achieve transparency of our latex dipped products with some success. However, we were informed that the choice of the types of coagulant is also important. We found straight dipping gave the best result but once we used calcium nitrate or calcium chloride, the unwanted opacity increases. Can you please explain?

John Woon (Senior Latex Consultant): I had explained about the choice of coagulant for maximum transparency in latex dipped products earlier in this blog.

The reason why you could not get good transparency when using calcium nitrate or chloride is that the resultant calcium soaps after coagulation are not soluble in the rubber. Also, the calcium soaps are not soluble in water and hence leaching would not help in improving the transparency significantly.

The best coagulant to be used for maximum transparency is CHA i.e. Cyclohexylamine Acetate (or Cyclohexylammonium Acetate). This is because while the cyclohexylamine itself is volatile, the resultant cyclohexylamine soaps are soluble in rubber.

One disadvantage of CHA is that it is a weaker coagulant compared to the calcium salts.

I'm happy to note that my report on latex compound formulation design for transparency had been useful to you.

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.


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.