Specification :

Brief description of mold making silicone rubber
Silicone rubber for mold making is white or red flowing liquid with general hardness of 22-50A° after curing. Molding silicon rubber is a kind elastic silicon rubber mold which features with resistance to deformation, high-temperature, acid-alkali and expansion as well as high reproduction times, good tensile strength, tear strength and elongation.
Applications of mold making silicone rubber
Silicone rubber for mold making is primarily intended for poly resin crafts, PU crafts, PU resin crafts , gypsum crafts , unsaturated resin crafts, lighting and candles crafts , plastic toy , stationery gifts crafts industry, a large statue Buddha, furniture, furniture decorative materials, statues Buddha, artifacts copied, building decoration materials, large-scale cement mold, artificial fossils Factory, Europe component factory, simulation landscapes, animals and plants sculpture, sandstone crafts and so on.

Brief features of mold making silicone rubber:
1. resistance to deformation, high-temperature
2. high reproduction times
3. good tensile strength
4. exceptional fluidity and good operability.

Model code:
According to the different materials, two series of mould making silicon rubber are divided, which are HY-6 and HY-7.
HY-6 Series includes model codes of HY-620, HY-640, HY-628, HY-638 with the hardness of 18-22 shore A, 38-42 shore A, 25-30 shore A and 35-40 shore A respectively.
HY-620 and HY-640 are particularly suitable for pouring mould.HY-620 is for small crafts mould making, while HY-640 is for large crafts mould making.
Common features of HY-620 and HY-640: light viscosity, pourable effort, good fluidity, easy-operation, good tension and high tear strength.
HY-628 and HY-638 are particularly suitable for brushing mould making.
Common features of HY-628 and HY-638: moderate viscosity, easy-operation. Agents are available if requested. It won’ t affect the quality of silicon rubber but to make the operation much easier.
HY-7 Series includes model codes of HY-718, HY-728, HY-738 with the hardness of15-20 shore A, 25-30 shore A and 35-38 shore A respectively.HY-718 is a kind of soft silicon rubber and suitable for pouring mould making of small crafts.HY7-28 with moderate viscosity is suitable for pouring mould and collapsible mould making of crafts in medium size.HY-738 with high hardness is suitable for to collapsible mould making of crafts in large size.
Note: Different colors are available if requested.
Operation Instruction for mold making silicone rubber:
Step One: Take 100g of part A and add 2g of part B and mix the silicone rubber and curing agent evenly.
Notes: Moulding silicon rubber is a kind of flowing liquid and it contains two parts. Part A is a kind of white flowing liquid and part B is the curing agent. Remember to mix part A and part B evenly, otherwise the silicon rubber will be partly solidified and this will give birth to difficulties in your final operation. What’ s more, the finished moulds will meet a short life. All of these will cause a waste of silicon rubber.
Step Two: vacuum pumping
Without exception, this step takes less than 10 minutes. Otherwise, it will cause cross linking reaction, and no more further steps will be available.
Step Three: Brushing cast & Perfusion Molding operation
Brushing cast:
a. Evenly brush the mixed silicon rubber on the product which is covered with mold spray with a brush or a brush pen.
b. After the cross linking reaction ( about 30 minutes) , brush a second coat which can increase the tension and tear strength of the mold.
c. Cover a glass cloth on it after another 30 minutes of a second cross linking reaction, and use a brush pen or a brush to avoid any interstices.
d. Cover a third coat.
( Note: if you have high requirements for the tension and the tear strength for the mold, please repeat step c and step d. Hence, the finished silicone moulds will have a good quality and a longer life, which can help you save cost and increase production efficiency.)
Perfusion moulding:
It is suitable for simple products with the smooth surface.Without any mold lines, which helps you save time and is easy for operation.Evenly and slowly perfuse the mixed silicone rubber into the square fram.After the cross linking reaction and the silicone rubber turns dry, you can take the products out.Thus, the mold has been done.
( Note: we usaully use soft silicone rubber to make molds by perfusing, which is easy for demoulding and will not damage the product in the silicone molds.)
Operations of external mold:
a. Make a square frame with four pieces of wooden boards or rubber plates, then place the product which is covered with the finished silicon rubber mould in the middle.
b. Slowly and evenly perfuse the gypsum into the square frame. Also you can brush the resin on the product which is covered with the finished silicon rubber mould with a brush or a brush pen. Repeat this process two or three time after the cross link reaction.

Frequently asked questions of mold making silicone rubber
1.Why does the silicone rubber mold have few molding times?
The silicone rubber mold has few molding times is due to follwoing reasons: adding too much silicone oil which will destroy the molecular of silicone rubber; making the mold for small and fine detailed products with higher hardness silicone rubber which is easy to break; making the mold for large products with soft silicone rubber which will reduce the tensile and tear strength of the mold, and the mold will have deformation. Thus, we should take the proper silicone rubber to make the mold for suitable products.
2. Why does the silicone mold get burnt out?
This consequence happens only because you have left out the important notes when using unsaturated resin materials to produce your products. The unsaturated resin produces great heat when added the curing agent. So you must demould the product within 3 minutes to avoid this problem.
3. Why does the silicone mould appear to be dry outside but wet inside?
Because molding silicone rubber is a kind of condensation silicone rubber, which get solidified after absorbing moisture from the air. In order to provide a significant shelf-life for the silicon rubber, we will dry out the water in the silicon rubber.
Solution: Add 0.05% water into the silicon rubber and Stir over a low speed briefly when you use it.
4. Why is the tear strength of the silicone mold weak?
In order to reduce the viscosity of silicone rubber and pursue a good quality, you may add a lot of silicone oil into the silicon rubber when making molds. In fact, it might have just the opposite effect. The tension and the tear strength will be reduced badly with the addition of silicon oil. And the silicon molds will be in a weak and flimsy manner.
5. Why is the silicon mold oily?
The molding silicone rubber itself doesn’ t contain any oil, so it won’ t be oily. If the mold is oily, it may be because you add the compound silicone oil( the compound of silicon oil and white oil) . The white oil is not silicon oil but a kind of petrochemicals.
6. Why isn’ t the silicon mold acid & alkali and aging resistant?
It is due to the addition of the silicon oil. Normally we do not advise our customers to add any silicon oil into the silicon rubber. If it is necessary, the ratio must be 5% -10% .
7.Why is the appearance of the finished mold striate and unsmooth?
It is because the appearance of the product or the model itself is not perfect, and it has not been polished before the further operation. So when you make silicon molds, firstly you should polish the product, spray the mold spray evenly on the product. In this case, the problem can be avoided.

Limitations:
1) When the hardness of silicon rubber is lower than 15 shore A, the tension, the tear strength, the ageing resistance, acid and alkali-resistance of silicon rubber will reduce respectively.
2) When the hardness of silicon rubber is higher than 50 shore A, the tension and the tear strength of silicon rubber will reduce, and the solidified silicon mold will be easily broken.
Any questions, please feel free to contact Ms. Jennifer :
TEL: 086-755-85224692
FAX: 086-755-89948030
MOBILE: 086-13164733190
Website: www( dot) szrl( dot) net
E-MAIL: jnf578( at) gmail( dot) com