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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.

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CONTENTS:

[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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Problem Solving Through E-Mails with John Woon Latex Consultants Is Possible
可以通过电子邮件与JW乳胶顾问来解决问题

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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)

img06.jpgimg04.jpgimg03.JPG

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.



Poor Flocking Quality of Household Gloves

Manufacturer: We are household gloves manufacturers. We are struggling with the quality of our flocke-lined gloves due to poor flock pick-up.



John Woon (Senior Latex Consultant): Your latex formulation for the adhesive layer should be designed to ensure the latex does not flow excessively and also there is a good latex-pick up to receive the flocks and hence the addition of a thickener is necessary. Also your surfactant system much be designed to ensure that there is no premature gelation of the latex otherwise the adhesion of the flocks to the latex is poor.

Friday, May 08, 2015

Governments to Construct Rubberised Roads

KUALA LUMPUR: The Malaysian government, in a bid to shore up natural rubber prices, will construct rubberised roads, says Plantation Industries and Commodities Minister Datuk Douglas Uggah Embas.



"We should increase the use of rubber and the government is targeting to utilise 10 per cent of total rubber production this year," he said, adding that Indonesia and Thailand have also agreed to do the same..........CLICK HERE to read the whole article.

Saturday, April 25, 2015

Other Roles Played by the Detack Powder in Coagulant

Manufacturer: We are gloves manufacturer. What other role is the detack powder playing beside reducing the tackiness of the rubber film? We found that when we eliminate the powder in the coagulant, we observed poorer film formation and uneven thickness.

John Woon (Senior Latex Consultant): Powder in the coagulant dip tank could help to minimize the the coagulant flow on the former which might result in thin patches. This is because as the water evaporates, the powder increases the viscosity of the coagulant on the former. The powder also causes the surface of the former to have a degree of roughness which in turns would also slow down the flow of the coagulant.

Other means of controlling the coagulant flow without using the detack powder have been sent to you separately as per your request. 

Wednesday, March 25, 2015

How to Achieve Maximum Transparency in Latex Coagulant Dipped Products

Manufacturer: We are manufacturing a wide range of latex dipped products using the coagulant dipping process with calcium nitrate. In one or two of our product range, we need to achieve maximum transparency in the final products. We have minimized or eliminated ZnO in our formulations but the degree of transparency still leaves something to be desired. Our prcess does not allow for straight dipping without coagulant.

We hope you could help us after viewing and studying our compound formulations.



John Woon (Senior Latex Consultant): Your formulations need some adjustment. Your choice of accelerators is wrong because different accelerates would have different solubility in the rubber and hence would affect the transparency of the rubber products. Three improved formulations which you can use have been sent to you separately.

You might also have to consider changing your coagulant because calcium nitrate would form rubber-insoluble salts/soaps and hence would reduce the transparency. One possible alternative is CHA (Cyclohexylammonium acetate) the by-products of which are more rubber soluble.

Friday, March 20, 2015

Successful Manufacture of Fabric-Lined Gloves

Manufacturer: We are manufacturing industrial supported gloves. Please explain the importance of coagulant and latex stability to ensure good quality gloves.


John Woon (Senior Latex Consultant): The strength of the coagulant (e.g. calcium nitrate) should be adjusted so that it is sufficiently strong to ensure adequate latex pick-up but not too strong that it prevents the penetration of the coagulant into the fabric otherwise the rubber to fabric adhesion would be poor.


The latex stability must be adjusted so as not to penetrate the fabric liner right through (i.e. strike through).

My detailed report on "Successful Manufacture of Fabric-Lined Gloves" has been sent to you separately.

Sunday, February 22, 2015

Alcohol-Based Coagulant Vs Water-Based Coagulant

Manufacturer: While most of the latex dipped products manufacturers today are now using water-based coagulant, we observe that some are still using alcohol-based coagulant despite the higher cost, health and fire hazards. Do you know why?

John Woon (Senior Latex Consultant): While the alcohol-based coagulant have the disadvantages you mentioned, it has the advantages of better flow control and faster evaporation. As a result, coagulant drainage problem can be minimised and more even deposit on the former attained.

Compared with water-based coagulant, it is also more effective in covering uniformly uneven former surfaces such as finger crotches and textured patterns.  


Former Cleaning with Hard Water

Manufacturer: We are glove manufacturers. We have heard that some of our competitors are using softened water for their former washing. What's the danger of using hard water?

John Woon (Senior Latex Consultant):

In some countries it is extremely important that after the online washing process, the formers are thoroughly rinsed with softened water. This is because the hardness of the water would deposit traces of inorganic salts on the former surface leading to potential formation of pinholes in the rubber film.

Monday, January 26, 2015

Why Is It Important to Remove Coagulant from Rubber Film by Leaching ?

Manufacturer: We are manufacturing toy balloons but without leaching. Why is it important to remove the coagulant from the rubber film by leaching ?



John Woon (Senior Latex Consultant): If the coagulant salt such as calciuum nitrate is allowed to remain in the rubber film, the film would tend to discolour when exposed to warm air, gas fumes and UV light. The physical properties would also be negatively affected due to poor particle-to-particle integration during drying.

I strongly advise you to install a leaching process in your Production as this would also improve the brilliance of the colour and gloss of your inflated balloons.


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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]

Disclaimer:
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.

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