GB/T 40125-2021 PDF English
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Liquid silicone rubber - Mold making
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GB/T 40125-2021: PDF in English (GBT 40125-2021) GB/T 40125-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.060
CCS G 35
Liquid silicone rubber - Mold making
液体硅橡胶 模具胶
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Classification and designations ... 5
5 Technical requirements ... 6
6 Test methods ... 7
7 Inspection rules ... 8
8 Marks, packaging, transportation and storage ... 8
Annex A (normative) Linear shrinkage test ... 10
Annex B (normative) Durability test for mold rubber ... 12
Liquid silicone rubber - Mold making
1 Scope
This Standard specifies classification and designation, technical requirements,
test methods, inspection rules, packaging, marks, transportation and storage
for liquid silicone rubber mold rubber.
This Standard is applicable to liquid silicone rubber for making rubber molds
(abbreviated as mold rubber).
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 528, Rubber, vulcanized or thermoplastic - Determination of tensile
stress-strain properties
GB/T 529, Rubber, vulcanized -determination of tear strength (trouser, angle
and crescent test pieces)
GB/T 531.1, Rubber vulcanized or thermoplastic - Determination of
indentation hardness - Part 1: Shore hardness tester method (Shore
hardness)
GB/T 2941, Rubber - General procedures for preparing and conditioning test
pieces for physical test methods
GB/T 22235, Determination for viscosity of liquids
GB/T 36804, Liquid silicone rubber - Classification and system nomenclature
3 Terms and definitions
There are no terms and definitions that need to be defined in this document.
4 Classification and designations
4.1 Type
Mold rubber is divided into four types according to its purpose:
a) Universal type
It is used for decorative moulding and industrial moulding, specifically for
the reproduction of statues, toys, candle holders, decorations, photo
frames. It is represented by the letter G.
NOTE: The material for reproduction should be plaster, polyester, polyurethane foam,
epoxy resin and so on.
b) Industrial prototype
It is used to manufacture precision molds and casting molds, with high
copy accuracy requirements and good simulation. It is represented by the
letter I.
NOTE: The material for reproduction should be polyurethane resin, ABS,
photosensitive resin and so on.
c) Building type
It is used for building beautification, such as restoration of historical sites,
sculpture decoration, stone marking, exterior decoration, building
renovation. It is represented by the letter B.
NOTE: The material for reproduction should be liquid concrete, plaster, artificial
stone, polyester and so on.
d) Pad printing type
It is used to use pad printing technology to print color graphics on the
surface of various objects, such as ceramic transfer, label or decal transfer.
It is represented by the letter P.
NOTE: The material for reproduction should be ink and so on.
4.2 Designations
The naming of mold rubber designation is based on the provisions of GB/T
36804. It is expressed by liquid silicone rubber code, product component,
vulcanization mechanism code, hardness, mold rubber code and type code.
6 Test methods
6.1 Appearance inspection
Visually inspect under natural light.
6.2 Specimen preparation and adjustment
6.2.1 Specimen preparation
Weigh a certain amount of unvulcanized liquid silicone rubber. The components
are mixed evenly according to the ratio specified in the product manual. After
vacuum deaeration, put it into the cold-mold mold. Make it naturally leveling. If
it cannot level naturally, add a cover plate. Vulcanization conditions are room
temperature or heating (refer to product instructions for details). The made test
piece shall be smooth and clean, uniform in thickness, and free of bubbles. The
finished test piece shall be cooled at room temperature for at least 16h. Then
prepare specimens according to the requirements of each test method.
6.2.2 Specimen adjustment
According to GB/T 2941, adjust the specimen temperature to 23°C±2°C, and
the relative humidity to 50%±10%. The adjustment time is not less than 16h.
6.3 Viscosity
Determine according to GB/T 22235.
6.4 Shore hardness
Determine according to GB/T 531.1.
6.5 Tensile properties
According to GB/T 528, Take 5 type 1 specimens to determine the tensile
strength and elongation at break.
6.6 Tear strength
Determine according to GB/T 529. Use a crescent-shaped specimen.
6.7 Linear shrinkage test
Determine in accordance with Annex A.
6.8 Durability
Determine in accordance with Annex B.
a) Manufacturer's name (or trademark) and address;
b) Reference to this Standard;
c) Product name;
d) Designation;
e) Batch number;
f) Date of manufacture;
g) Net weight.
8.2 Packaging
Generally, the packaging of liquid mold rubber includes inner packaging (plastic
bag) and outer packaging (metal drum, 25kg or 150kg). Other packaging
methods agreed between the manufacturer and the user can also be used.
Each batch of products shall be accompanied by a product certificate,
inspection report and product instruction manual. The product instruction
manual includes at least the following content:
a) A description of the components;
b) The mixing ratio of the components;
c) Vulcanization conditions.
8.3 Transportation
During the transportation of the product, avoid rain and snow dipping and sun
exposure. It is strictly forbidden to contact with oil, grease, acid, alkali.
8.4 Storage
When two-component or multi-component mold rubber is stored, each
component shall be stored separately. The product is sealed and stored in a
dark, clean, dry and ventilated warehouse. Avoid squeezing. From the date of
production, the storage period shall not exceed 12 months.
Annex B
(normative)
Durability test for mold rubber
B.1 Overview
The durability of the mold rubber is embodied in the number of mold reversals
or the number of pad printing.
B.2 Equipment and materials
B.2.1 Male mole: The shape and size of the male mold can be negotiated by
both parties (see Figure B.1).
B.2.2 Reproduction material: polyurethane resin or other reproduction material.
NOTE: The designation of the resin is determined through negotiation between the supplier
and the purchaser.
B.3 Specimen preparation
Mix the various components of the mold rubber according to the ratio given in
the product manual. Mix well. Put the mixed rubber in the vacuum chamber.
Properly adjust the vacuum to eliminate bubbles in the mixture. Then pour the
mixed rubber into the male mold.
Vulcanize the rubber compound according to the conditions given in the product
manual to make a silicone mold (female mold), printing roller or printing plate.
B.4 Test steps
B.4.1 Mold reversal
Pour or coat polyurethane resin (or other resin) on the silicone mold. Naturally
or heat curing completely. Remove the reproduced resin product. Check
whether the reproduced product meets the requirements. If it is reached, it will
be counted as a mold reversal. Repeat this operation for N times, until the
silicone mold is deformed, cracked, falling off, then stop using it. The number
of mold reversal is recorded as N-1 times.
B.4.2 Pad printing
Use a roller or printing plate to dip the ink or other materials evenly. Print the
desired pattern on the substrate. Check whether the pattern is clear and
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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