Ribbed Smoked Sheets

    Ribbed Smoked Sheets (RSS) are coagulated rubber sheets processed from fresh field latex sourced from well managed rubber plantations adopting modern processing methods. The grades available are shown in the table.  The higher grades RSS 1x to RSS 3 are mainly used for manufacture of products for medical, pharmaceutical and  engineering. The lower grades of RSS 4 and 5 are generally used for the manufacture of automobile tyres, re-treading materials and all other general products.  RSS 3 and RSS 4 are the preferred raw material for radial tyres.   Quality of Ribbed Smoked Sheets is ascertained as laid down in Green Book Standards.

In India, RSS grades are packed as 50kg bales in polythene cover and as 110kg crates as per the requirements of the buyer. Ribbed Smoked Sheets are graded according to the standards as per IS – 15361-2003 by visual comparison method.  Normally this is done by observation of sheets held against light, when the obvious defects become apparent.

Cluster groups formed among rubber farmers in India, popularly known as “Rubber Producers Societies (RPS) are involved in the production of high quality grades in their group processing centres for domestic and world markets.  High grade sheets are produced in individual farms as well. 

Domestically produced RSS rubber grades are in good demand for tyres and other product manufacture indicating their quality and market acceptability.

RSS 1X -

Oxidized spots or streaks, weak, heated, undercured, over-smoked, opaque and burnt sheets are not permissible in this grade. The rubber must be dry, clean, strong, sound and evenly smoked, and free from blemishes, specks, resinous matter (rust), blisters, sand, dirty packing and any other foreign matter.  Small pinhead bubbles, if scattered, will not be objected to.

RSS 1 -

Oxidized spots or streaks, weak, heated, under cured, over-smoked, opaque and burnt sheets are not permissible in this grade. The rubber must be dry, clean, strong, sound and evenly smoked, and free from blemishes, specks, resinous matter (rust), blisters, sand, dirty packing and any other foreign matter, except slight specks.  Small pinhead bubbles, if scattered, will not be objected to.

RSS 2 -

Oxidized spots or streaks, weak, heated, undercured, over-smoked, opaque and burnt sheets are not permissible in this grade. The rubber must be dry, clean, strong, sound and free from blemishes, blisters, sand, dirty packing and all other foreign matter other than specified above as permissible.

RSS 3 -

Slight blemishes in color, small bubbles and small specks of bark permissible in this grade.   Oxidized spots or streaks, weak, heated, under-cured, over-smoked, opaque and burnt sheets are not permissible in this grade. The rubber must be dry, clean, strong, sound and free from blemishes, blisters, sand, dirty packing and all other foreign matte r other than specified above as permissible.

RSS 4 -

Medium size bark particles, bubbles, translucent stains, slightly sticky and slightly over smoked rubber are permissible.  Oxidized spots or streaks, weak, heated, under-cured, over-smoked, and burnt sheets are not permissible.  The rubber must be dry, clean, strong, sound and free from blemishes, blisters, sand, dirty packing and all other foreign matter other than specified above as permissible.

RSS 5 -

Large bark particles, bubbles and small blisters, stains, over-smoked, slightly sticky rubber and blemishes are permissible.  Slightly under-cured rubber is permissible.  Weak, heated, burnt, oxidized spots or streaks are not permissible.   The rubber must be dry, firm and free of blisters.  Dirty packing, sand and all other foreign matter other than specified above is not permissible.

Air Dried Sheets-

This is a light colored sheet prepared in the same way as ribbed smoked sheets but dried in a shed or tunnel using hot air instead of smoke.  As color of the sheets is an important consideration, use of sodium bisulphate which inhibits enzymic discoloration and lightens the color is necessary.  Usually a calculated volume of a solution of sodium bisulphate is added in the bulking tank so as to get 1.20 g of it in one kg of dry rubber.  Air dried sheets can be used as substitutes for Pale Latex Crepe and hence this type of sheets may fetch a better price compared to smoked sheets.

Ribbed Smoked sheets (RSS grades)  specification as per Green Book

Parameters

RSS 1X

1

2

3

4

5

Air Dried sheets Froathy sheets Partly/fully skim latex sheets Wet sheets Bleached (pale) sheets Sand Dirty packing Oxidised spots Streaks Weak sheet Heated Sheet Burnt Sheet

No

Sheets to be – Dry      “       “     - clean      “       “   -  strong      “       “   -  sound

Yes

Covering sheets

Same or higher grade

Holes in Wrapper sheets

Use double wrapper sheets

Bale coating & stenciling

As per the Green Book standard

Resinous matter (rust)

No

No

slight

Less than 5% of sample

Less than 10% of sample

Less than 20% of sample

Less than 30% of sample

Mould/Dry mould

Free of Mould Very slight traces of dry mould on wrappers or bale surface adjacent to wrapper. (No penetration)

+slight on wrapper & bale surface & interior

less than   less than   less than   less than 5% of         10% of      20% of      30% of sample      sample     sample      sample

Blisters

No

Slight

Other foreign matter

No ( other than specified, if any)

Bubbles/pin head bubbles

Scattered small pin-head bubbles

Small bubbles

Medium size

Large

Transluscent stains

No

Medium size

Yes

Stickiness (Tackiness)

No

slight

Under-cured

No

slight

Over smoked

No

Slight

Yes

Opaque sheets

No

Evenly smoked

Yes

Slightly over smoked

Over smoked

Blemishes

No

Yes

Specks

No

Slight

Slight specks of bark

Small specks of bark

Medium size bark

Large bark particles

Stains

No

Small stains

Prohibitions applicable to all grades of RSS

1. Block, cuttings, or other scrap or frothy sheets
2. Weak, heated or burnt sheets
3. Air dried or smooth sheets
4. Wet, bleached, under-cured and virgin rubber
5. Rubber that is not completely visually dry at the time of buyer’s inspection
6. Skim rubber made out of skim latex used in whole or part in the production.

Defects not permitted in any RSS grade

• Opaque sheets
• Wet mould
• Weak sheets
• Heated sheets
• Burnt sheets
• Oxidised sopts or streaks
• Airdried sheets
• Frothy sheets
• Dirty packing sand
• Other foreign matter