1. RIBBED SMOKED SHEET (RSS: RIBBED SMOKED SHEET)
1.1 Manufacturing method
Grade ribbed smoked sheet by its purity, color and does not have flaws such as air bubbles seen with normal eyes.
An important factor in manufacturing good quality RSS is to ensure the purity. Supplying enough clean water is necessary for diluting latex and cleaning during creating the sheet.
Latex is collected as soon as possible to prevent it from congealing soon and we also can use the popular anti-freeze agent Sodium sulfite (Na2SO3). The dosage can be changed depending on each condition but does not exceed 0,05% for dry rubber.
Congealing can be used as single congealing blocks as congealing tank or congealing to continuous sheets.
When bring latex to the factory, must take samples to check DRC; there are many testing methods but the popular one now is TSC quick test and use table to convert into DRC.
1.2 Quick method to define Total Solid Content (TSC)
Put about 10g liquid latex and tube (weighed in advance) and weigh exactly up to 0.01g.
- Pour latex and tube cleaning water to a clean pan (clean the tube by distilled water)
- Coat latex equally on the pan bottom and put it on the stove, shake the latex pan in order to make the latex scatter equally until the water is evaporated completely. Continue to bake until latex has yellow color.
Take the pan out of the stove and leave it cool. Take all rubber out of it, weigh dry rubber on a technical scale. Calculate the result:
TSC (%) = m2 x100/(mo –m1)
Where mo: quantity of latex and tube (g)
m1: quantity of tube (g)
m2: quantity of dry rubber (g)
When the factory receives latex and filter through 40 mesh or 60 mesh metal sieve and dilute 12.5-15% and deposit for about 15 minutes to remove contaminants such as sand, stone and congealing by Acetic acid (CH3COOH), or Formic acid (HCOOH) with concentration of 2-5% w/v at pH = 4.6- 4.9
Congealing at high DRC will cause easily bubbles in rubber sheets, at low DRC will increase power consuming in manufacturing.
Leave it for a night to have well-trained congealing then roll into thin layers. Crepe sheet is hung in smoke house to drain for 2-4 hours, then dry at temperature 50-48oC, do not dry over 63 oC, it is easy to make air bubbles.
Grading ribbed smoked sheets is carried out by observation method:
• RSS 1 : No bubble, no dirt, no speck
• RSS 2 : and small bubble, no dirt, no speck
• RSS 3, 4, 5 : more bubbles, no dirt, no speck