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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可以通过电子邮件与JW乳胶顾问来解决问题
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Monday, December 24, 2012
Thursday, December 20, 2012
Which One Is Better - Thread Made From Latex or Thread Made from Dry Rubber?
John Woon (Senior Latex Consultant): I have good news for you because thread produced from latex extrusion process have quite a number of advantages over those made from dry rubber where the thread was made by slitting or cutting thin sheet of rubber made from dry rubber process.
Here are your advantages:
1) Compared with the cut thread whose cross-section is usually a square, that of the latex thread is round. This means that latex thread would have a lower surface area and therefore would be less detrimental to degradation due to exposure such as UV attack and oxidation.
2) Latex extrusion is a continuous process which makes consistency in quality easier whereas the dry rubber process entails a number of different steps that include mixing, calendaring, wrapping, curing, lapping and cutting.
3) The surface of latex thread is smoother than the cut thread under microscopic examination, i.e. cut thread shows more jagged and irregular surfaces.
4) A wider range of thread sizes especially for the finer ones is possible with latex thread whereas this is limited by the cutting process.
5) The last but by no means the least, is an advantage of utmost importance which you can capitalize on to convince your customers. This has to do with the physical properties especially the elasticity of the finished thread.
In the dry rubber process, the rubber must first be subjected to a process we rubber technologists refer to as "mastication" whereby the molecules of the raw rubber is broken down into smaller units to make rubber softer so as to facilitate the addition and mixing of the compounding ingredients. This invariably weaken the inherent strength of the rubber of the finished products.
No "mastication" process is required for latex thread using the latex extrusion process and hence the rubber remains strong particularly in terms of the elasticity, low permanent set, resistance to solvent and oil and resistance to ageing.
Internal and External Plasticization
John Woon (Senior Latex Consultant): There are basically two ways to soften or plasticize the polymer (i.e. to reduce the Glass Transition Temperatures or Tg) - one is through copolymerization where more than one monomer are used while the other is by adding a plasticizer. This of course would also increase the plasticity and fluidity of the polymer.
The former method is termed "Internal Plasticization" while the latter, "External Plasticization".
Wherever possible, "Internal Plasticization" is the preferred route since adding a plasticizer entails careful selection for compatibility, processibility, permanence and other performance properties which in turns are dependable on solubility parameter, molecular weight and chemical structure, etc of the plasticizers.
Examples of undesirable side effects are the gradual loss of the plasticizer and hence the increase in stiffness during service life through evaporation and leaching.
Adhesion and Cohesion of Nitrile Latex Adhesives
John Woon (Senior Latex Consultant): You did not mention whether you were using tackifiers. Unlike Natural Rubber and polychloroprene, Nitrile rubber has poor inherent tackiness. Hence the addition of a good tackifier is a must for Nitrile.
However you should bear in mind that over addition of tackifiers might lead to poor film strength (i.e. cohesive strength).
Therefore a balance should be optimized and reached between good adhesion (tackiness) and cohesive strength (film strength). Some describe "tackiness" as "dry wetting property" which is essential for building adhesive strength between the adhesive and the two surfaces being bonded.
I appreciate your concern about cost and believe that you are adding to fillers to reduce your compound cost. However, the filler would kill both the adhesive and cohesive strength.
Unfortunately, tackifiers could be expensive. Among the tackifying resins, you could use the following types:
1) Hydrocarbon
2) Coumarone indene
3) Hydrogenated esters
4) Terpene resin
To improve the cohesive strength, you could try adding reinforcing agents such as phenolics and terpene-phenolics or other derivatives. Please discuss with your suppliers to decide on the right choice for your purpose. However I must warn that this might not work if there is too much filler in your compound.