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Manual Mold Silicone Rubber

Manual Mold Silicone Rubber

Applications of manual mold silicone rubber
Manual mold silicone rubber is mainly used for model design of manual mold, PVC plastic molds, cement products, low melting point alloy molds, alloy toys, plastic toys, electronics, handicrafts, stationery, large-scale sculpture, reproduction of cultural relic, shoe sole molds, pad printing allocation, electronic equipment antivibration, and so on.

General introduction on manual mold silicone rubber
HY-528# is applicable to make molds of smaller products and the reduplication will be 2-3 times.
HY-540# , compared to other two types, for its moderate hardness and better quality & performance, its reduplication will be 20-30 times.
HY-570# is applicable to large size products duplications and electronic equipment antivibration.

Operation Instruction of manual mold silicone rubber
Manual mold silicone rubber is a flowable liquid, and the quality has nothing to do with the color. It consists of two components. Part A is a flowable liquid silicone rubber, part B is the curing agent. Firstly, after dealing with the original model, take some liquid silicone rubber, add 2%-3% curing agent of the amount of silicon, and mix them evenly. Then after vacuum-pumping the mixture, you can pour it into the mold frame. The silicone mold will cured in 2-3 hours.

Note: The time for vacuum-pumping should be less than 3-5 mins. Otherwise, once the silicone rubber has cross-link reaction during vacuumizing, it will not be operated.

Features of manual mold silicone rubber
Manual mold silicone rubber has good elasticity, non-deformation, high temperature resistance, low shrinkage. And it is suitable for manual mold design and duplication of small mold products.

Operation Instruction
1. Correct mixing ratio
Component A is mould making silicone rubber, and component B is curing agent or vulcanizing agent, usually the mixing ratio will be 2-3%. Such as to 100G silicone rubber should be added 2G catalyst and then mix them totally (Note: the weight of the silicone and catalyst should be weighted correctly.
According to local weather, the mixing ratio can be 100 to 2 under room-temperature 25 0C; if the local weather is about 10 0C, then the maximum mixing ratio should be 5%; When local temperature is -5 0C, no reaction will happen between the silicone rubber and hardener; once the temperature of local weather is 38-45 0C, the mixing ratio should be 1 %).

2. Preparation of the original molds
Firstly, you should deal carefully with the original mold or the products you want to be molded. If no polishing of the original mold or the products you want to be molded, the surface of it is not so smooth or perfect, then the products made out of silicone molds will be not up to standard.

3. Vacuum-Pumping Process
Mix the manual mold silicone rubber and catalyst with a standard mixing ratio and then do the process of vacuum-pumping. Bubbles will come out during the mixing. If without vacuum-pumping, the bubbles cannot be released from the mixture. As a result, there will be many bubbles in the finished silicone mold. Then the mold has a worse tensile strength which will affect the reproduction times. Such an unsmoothed silicone mold will affect the quality of the production directly.

FAQs of the manual mold silicone rubber
1. How to deal with the bubbles during the mixing process?
It depends on your practical situation. Firstly you can deal the mixture with a vacuum machine if you have one. If no such machine, you can reduce the mixing ratio of the hardener from 4% to 1%-2%.Then in the prior period of the reaction of the mixture will be slower, then the air in the mixture will exhaust by itself for a longer curing time to release the bubble.

2. What should you do for incomplete curing after the mold is finished?
Two causes lead to this problem:
(1) Inexact mixing ratio, not to weigh following the standard.
(2) The mixture of the mould making silicone rubber and catalyst is not mixed evenly. You should avoid this kind of problem; otherwise there will be a waste of silicone mold.

3. The solutions of the sticky of the silicone mold?
The main reason for this problem is that you do not handle the products or original molds well, and then you should deal with the original mold or products carefully before molding. Such as for the products with a complicated pattern or a unsmoothed surface, you should polish and clean the products after which it will be molded, then spray the release agent. Normally, the release agent can be Vaseline, detergent, liquid wax, etc. In practical process, you can brush different release agent according to different material.
The second reason is that the operator pours the molding silicone rubber into the mold when the mixture isn't mixed evenly, then the finish silicone mold will be partially cured.

4. What should you do for deformation of the silicone mold?
It should deal apart according to the size of the products. In principle, the hardness of the mold making silicone rubber should be consistent to the size of the products. For the small size products with detailed patterns, the soft silicone rubber can be applicable which the shore A should be 15-20 for easy demoulding and not damage of the patterns. Otherwise harder silicone rubber should be needed for large size products, such as products with size 50cm will need harder silicone rubber with 40-50 shore A, then no-deformation. If large products but features detailed patterns, then 30 shore A silicone rubber will be workable. (The process should be: a layer silicone, added with a layer fiber glass or cloth.) The outer of mold can be plaster, glass fiber reinforced plastic (unsaturated resin and fiber glass) to protect the products from deformation.

5. How to make an outer mold?
One is to enclose the mold by a plastic plate or wooden plate, then pour into the liquid plaster to fill the mold frame. Another is brushing or coating a layer of resin and then pasting a fiber glass, then repeat brushing and pasting tow to three times, then a outer mold will be finished。

6. How to distinguish the pure silicone oil and un-graded silicone oil?
(1) Check by your observation
Pure silicone oil is a transparent liquid without any smell, but ungraded silicone oil smells bad and is in a turbid liquid form.
(2) To test it by fire.
Take the pontil or glass rod to dip some liquid. If it can be lighted and fumed when burning, so the liquid is the ungraded silicone oil, which is a kind of petrochemicals. And, pure silicone oil can not be lighted, which is colorless, odorless, clear, nontoxic.
The burning point of pure silicone oil is 320C, but ungraded silicone oil is 100C.
(3) Freezing point method
Take 100g of two kinds of silicone oil into refrigerator at the same time. Under temperature of-5 to -10 C for 2 hours, ungraded silicone oil will turn to turbid or frozen, while pure silicone oil is still clear and transparent as before, and it will not freeze until -50 0C.

7. Operation procedure of making multi-pieces mold.
For multiple piece instructions, you can use the vacuumized silicone rubber to make molds in a brushing or pouring way.
If you want to do a multi-pieces mold in a brushing way, it's necessary to coat a layer of release agent or dusting agent on the original mold before brushing, then brush a layer of silicone rubber to the surface of the products (note: it should be brushed evenly), then after 30 minutes spread a layer of gauze or fiber glass cloth to improve the tear strength, then coat the second layer of silicone rubber, after the second layer cured, you can make an outer mold, which can be made of plaster or resin material.

8. Operation procedures for making pouring or perfusion mold.
pouring or perfusion mold is always used for simple or smooth products, and without mold line,it will save time and labor . Enclose the products with plastic plate or glass plate, pour the vacuumized silicone rubber onto the products, after the silicone cured, you can take out your products, and then a mold is formed.
(Note: Generally, in this pouring way, you should use low-hardness molding silicone rubber to make molds, so it will be easier to demould and will not destroy the products.)

Silicone Rubber
    1. Pad Printing Silicone RubberNumber: HY-912
      Distribution time: 2010-06-21
      Usage: For the pad printing of plastic toys, PVC toys, craftworks.