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NR in sheet
forms are the oldest and the most popular type. Being the simplest
and easiest to produce on a small sacle, small holder's rubber in
most of the countries are processed and marketed as sheet rubber. Two
types of sheet Rubbers are produced and marketed in the international
market, namely the Ribbed smoked sheets(RSS) and the Air Dried
Sheets(ADS). Among these two types, Ribbed smoked sheet is the most
popular and is available for volume consumption.
RIBBED
SMOKED SHEETS (RSS)
Ribbed
smoked sheets are marketed based on visual assessment of quality. To
establish acceptable grades for commercial purposes, the
international Rubber Quality and Packing conference, have stipulated
the grade description and the details are given in the Green Book.
THE
INTERNATIONAL GRADE DESCRIPTIONS FOR RSS
Only
deliberately coagulated rubber latex processed into rubber sheets,
properly dried and smoked can be used in making RSS. The following
prohibitions are also applicable to the RSS grade.
Wet,
bleached, undercured and virgin rubber and rubber that is not
completely visually dry at the time of buyer's inspection is not
acceptable(except slightly undercured rubber as specified for RSS-No: 5)
Skim
rubber made of skim latex shall not be used in whole or in part in
the patches as required under packing specifications.
Prior
to grading RSS, the sheets are separated, inspected and any
blemishes are removed by cutting with a pair of scissors.
GRADE
DESCRIPTIONS
No:
IX RSS
The
grade must be produced under conditions where all processes are
carefully and uniformally controlled. Each bale must be packed free
of mould but very slight traces of dry mould on wrappers or bale
surfaces adjacent to wrapper found at time of delivery will not be
objected to provided there is no penetration of mould inside the
bale. Oxidised spots or streaks, weak, heated, undercured,
oversmoked, opaque and burnt sheets are not permissible.
The
rubber must be dry, clean, strong, sound and evenly smoked and free
from blemishes, specks, rust, blisters, send, dirty packing and any
other foreign matter. Small pinhead bubbles if scatteres, will not be
objected to.
No:
1 RSS
Each
bale must be packed free of mould but very slight traces of dry
mould on wapper or bale surfaces adjacent to wrapper found at the
time of delivery will not be objected to provided there is no
penetration of mould inside the bale. Oxidised spots or streaks,
weak, heated, undercured, oversmoked, opaque and burnt sheets are not permissible.
The
rubber must be dry, clean, strong sound and from blemishes, rust,
blisters, sand, dirty packing and any other foreign matter, except
slight specks. Small pinhead bubbles, if scattered, will not be
objected to.
No:
2 RSS
Slight
rust, and slight amount of dry mould on wrappers, bale surfaces and
interior sheets, found at time of delivery will not be objected to,
provided these conditions either singly or in combination, do not
exist to an objectionable extent on and in more than 5% of the number
of bales included in the delivery, lot or tender as determined by the
number of bales inspected.
Small
bubbles and slight specks of barks, if catteres, will not be
objected to.
Oxidised
spots or streaks, weak, heated, undercured, oversmoked, opaque and
burnt 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.
No:
3 RSS
Rust
and dry mould on wrappers, bale surfaces and interior sheets, found
at time of delivery will not be objected to, provided these
conditions, either singly or in combination, do not exist to an
objectionable extent on and in more than 10% of the number of bales
included in the delivery, lot or tender as determined by the number
of bales inspected. Slight blemishes in clour, small bubbles ans
small specks of bark permissible. Oxidised spots or streaks, weak,
heated, undercured, oversmoked, opaque and burnt sheets are not
permissible. The rubber must be dry, strong and free of blemishes,
blisters, sand dirty packing and all other foreign matter other than
specified above as permissible.
No:
4 RSS
Rust,
dry mould on wrappers, bale surfaces and interior sheets, found at
time delivery will not be objected to provided these conditions,
either singly or in combination, do not exist to an objectionable
extent on or in more than 20% of the number of bales included in the
delivry, lot or tender as deteremined by the number of bales inspected.
Medium
size bark particles, bubbles, translucent stains, slightly sticky
and slightly over smoked rubber as permissible but should not be
evident to a marked degree. Oxidised spots, or streaks, weak, heated,
undercured opaque and burnt sheets are not permissible. The rubber
must be dry, firm and free of blemishes, blisters, sand, dirty
packing and all other foreign matter other than specified above as permissible.
No:
5 RSS
Rust,
dry mould on wrappers, bale surfaces and interior sheets, found at
time of delivery will not be objected to provided these conditions,
either singly or in combination, do not exist to an objectionable
extent on or in more than 30% of the number of bales included in the
delivery, lot or tender as determined by the number of bales inspected.
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