Silicone mold is a special mold for making crafts. According to performance, the raw materials of glue can be divided into ordinary silica gel and weather silica gel. The characteristics of silica gel are high temperature resistance, corrosion resistance, strong tear resistance, high simulation precision, and it is used to make various handicrafts. Mold.
Silicone is more and more popular because of its environmental protection performance. To understand the knowledge of silicone molds, you must start with the raw materials of silicone.
1. Ordinary silica gel, also known as precipitated silica gel
- Color: translucent, milky white, light yellow, gray, etc.
- Hardness: 30°, 40°, 50°, 60°, 70°, etc., commonly used between 40°-70°.
- Density: 1.1-1.12g/cm³
- Elongation: 400%
- Purpose: The most used are mobile phone buttons, miscellaneous parts, conductive glue and other low- and medium-grade silicone products.
- Weather glue, also known as pure silica gel
- Color: transparent.
- Hardness: 30°, 40°, 50°, 60°, 70°, 80°, etc., commonly used between 40°-60°.
- Density: 1.1-1.12g/c㎡
- Elongation: 600%-700%
- Features: Because this material has good transparency and strong tensile strength. High cost
- Uses: Silicone tubes, protective sleeves and other high-end products that require high elasticity.
2. According to physical properties, silica gel raw materials can be divided into solid silica gel and liquid silica gel.
Solid silica gel is mainly used for molded products. For example: silicone sleeves, silicone tableware, silicone molds, silicone buttons, etc. Liquid silicone is mainly used for extruded products, such as silicone pacifiers, silicone tubes, etc.
Thermal insulation silicone pad, excellent high temperature resistance, silica gel (food grade silica gel) can withstand high temperature of 200 ℃ and can be used for a long time. The raw materials of this product meet food-grade standards and pass FDA food-grade testing. It is odorless and non-toxic. Production, color and shape can be customized.
The Production Process Of Silicone Mold
The selection of the mold opening form and the selection of the mold line are very important. First, it is convenient to take the mold. Second, the mold line should be selected so as not to affect the overall effect of the product. Third, it does not affect the product quality. High, the mold sealing line requires a lot of materials, and product cracks are prone to occur; the fourth is to reduce the process operation procedures, such as opening half of the mold.
In order to prevent the flow of silica gel, the mold is fixed in a regular range with wood or planks. When opening the die, the first part of the mold is separated from the sludge. There is no gap between the sludge and the mold, and the surface of the sludge is smooth and flat. After the above work is prepared, then apply petroleum jelly or spray release agent on the plaster mold or the mold. For smooth products, use a clean cotton cloth dipped in petroleum jelly and apply it evenly on the mold. Keep for 30 minutes to make the mold. The product fully absorbs the petroleum jelly, and then wipes the surface of the mold with a clean cotton cloth, and the surface is required to be bright; and the textured product only needs to be evenly coated with the petroleum jelly to adjust the silica gel according to the formula. When mixing the silica gel, stir in irregular directions to make the curing agent and silica gel fully mix to minimize air mixing into the rubber. For smooth products, it is best to vacuum once when the first layer of rubber is applied, and keep the vacuum at -0.1Mpa. 7-8 seconds.
Molding should be made in time after the silica gel is matched. Pour the glue on the highest part of the mold in a trickle, let it flow naturally, brush it in place with an oil paintbrush where the flow is not in place, if it is a piece of silica gel, not only fill the entire product, but also brush the glue evenly. Each product should be brushed with at least three layers of silica gel. The thickness of each layer of silica gel is 1mm. In the process of brushing the silica gel, each layer is required to be cured before the other layer can be brushed. When brushing the third layer, add one layer on top of the second layer. Layer gauze to increase the strength of silicone. The thickness of the entire mold silicone part is controlled at 3-4mm according to the different requirements of the product size, and the width is not greater than the product width 60 mm. The start time of silica gel is 20 minutes.
- Wash the master mold and dry it for smooth treatment (a layer of mold release wax or mold release agent can be applied)
- Put 500-1000 grams of mold silicone rubber (mold silicone, mold rubber, silicone rubber, silicone) as a plastic basin for use;
- Weigh the hardener according to the weight ratio (usually 1.5-2.5%), then add it to the container for mixing, and stir well;
- Add a certain amount of silica gel diluent according to the situation (especially the first layer). Until the mixture is uniform, usually 3-5 minutes.
- Mold silicone rubber (mold silicone rubber, mold rubber, silicone rubber, silica gel) is mixed with the hardener, it will react at room temperature and release low-molecular alcohol. In order to release the alcohol molecule from the colloid, it needs to discharge bubbles under negative pressure 1-3 minute. It can also be used without equipment (mainly depends on the operating experience of the mold maker)
- Multi-layer coating film molds should be cured at the same time as inside, middle and outside. When the amount of curing agent is relatively small, the reaction time is longer, the reaction is sufficient, and the colloid is good. Therefore, the amount of curing agent is best to be less inside and more outside. When brushing, wait for the first layer (inner layer) to dry before brushing the second layer. The operating time is 30-50 minutes, and the mold removal time is 10-15 hours. The curing time is 24 hours. Note that it is best to add mold cloth after painting the first and second layers, which can greatly improve the service life of the mold (but not use glass fiber cloth, otherwise it is easy to cause delamination and the entire mold is scrapped)
- Three-dimensional perfusion mold, generally curing in 10-15 hours is better.
- After the soft mold is made, plaster or glass fiber reinforced plastic jacket should be made to support the silicone soft mold. Note: 1. Mold line selection: choose a position that does not affect the appearance of the product; choose a position that is easy to process after grouting; choose the mold itself to be easy to disassemble The position of the mold; choose the position where the product is not easy to deform. 2. Don’t blindly increase the amount of hardener in order to catch up with the production schedule, otherwise the service life of the silicone mold will be greatly reduced.
The Common Problem Of Silicone Mold
1. Why does the mold silica gel have fewer re-molding times?
Too much silicone oil is added in the process of making the mold, and the silicone oil destroys the molecular weight of the silica gel, so the mold will have fewer times of turning over and become less durable. If it is said that a small product with a more complex pattern is used to open the mold with a high-hardness silica gel, there will be a phenomenon of less re-molding, because the silica gel will be brittle and easy to break when it is too hard. On the contrary, if you use low-hardness silicone to make molds for building products, the results will also be unsatisfactory. Because silica gel is too soft, its tensile strength and tear strength will be reduced, and the resulting mold will be deformed, so the number of mold turns will be reduced. The quality of the mold glue itself is very good, and there is no difference between good and bad silicone, only suitable and unsuitable. We have to use silica gel suitable for the hardness of the product to make the mold and this situation will not occur.
2. Why does the mold silicone burn mold?
Because unsaturated resins and resin products are added with peroxide curing agents, they will generate a lot of heat when they react with the resin. Generally, the curing time of the resin is 3 minutes, so the mold must be demolded as soon as possible after 3 minutes to prevent the silicone mold from being damaged. Produce burn-in phenomenon.
3. The production method of mold silicone filling mold and split mold
Operation method of split mold or sheet mold: apply the vacuumed silica gel to the construction by brushing or pouring. If you are making a sheet mold or a split mold and use the brushing method, first apply a layer of release agent or release agent to the product or model you want to copy before painting, and then brush the silicone on the product (Note : Be sure to paint evenly) After waiting for 30 minutes, stick a layer of gauze or glass fiber cloth on the surface to increase the strength, and then apply a second layer of silica gel. After the silica gel is dry, make an outer mold. The outer mold can be used Materials such as plaster or resin.
The operation method of filling mold or infusion mold: filling mold or infusion mold is used for relatively smooth or simple products, that is, surround the product or model you want to copy with a plastic sheet or glass plate, and evacuated the silicone rubber Pour directly onto the product, after the silica gel is dried and formed, take out the product, and the mold is formed (Note: The infusion mold is usually made of soft silica gel, so that it is easier to demold and will not damage the product in the silicone mold) , The above is the entire process of using and operating mold silicone.
4. Why does the mold silica gel appear to be dry on the outside and inside?
Mold silica gel is a condensation type silica gel. It is cured by absorbing moisture in the air. In the process of making silica gel, the water is evaporated to dryness without adding proper amount of water. This phenomenon will occur. . Solution: This phenomenon is not a product quality problem, but because there is no water control, and the storage period of the silica gel is increased, and the shelf life is long, some phenomena will appear. As long as the silica gel is used, an appropriate amount of 0.05% water is added and mixed evenly. Some situations can be resolved.
5. Why does the mold silicone have poor tension?
In order to reduce the viscosity of the silicone and make the silicone easy to handle, the customer added a large amount of silicone oil to the silicone in the process of making the mold. This will make the silicone very soft, resulting in tensile strength and reduced tear strength. The phenomenon of deterioration of the tensile force, resulting in the mold is not durable, the service life is short, and the number of mold turning times is small.
6. Why does the mold appear to be oily?
The mold silica gel itself does not emit oil. The oil emission occurs because of the addition of compound silicone oil (a compound of silicone oil and white mineral oil) during the operation, because white mineral oil is a petrochemical product, not a silicone oil.
7. Why is the mold not resistant to acid and alkali, and not resistant to aging?
In the process of making silicone molds, we recommend that customers do not add any silicone oil. If necessary, the amount of silicone oil added should not exceed 5%-10%. Because excessive addition of silicone oil will destroy the molecular weight of silica gel, the resulting mold will not be resistant to acids and alkalis, and not resistant to aging.
8. Why does the mold made of mold silicone have traces, streaks, and unevenness on the surface?
This phenomenon occurs because the product or model to be copied is not polished or polished. In fact, the model or the product itself is not smooth or perfect, so if the product or model to be copied is not polished or polished, the mold made of silica gel will be unsightly and not smooth enough. Another situation is that when the release agent is applied, the mold is not smooth if it is not evenly applied.
9. Do you know the wonderful use of mold silicone? ?
Mold silicone is mainly used in toy and gift industry, craft gift industry, furniture decoration industry, character reproduction, building decoration industry, resin handicraft industry, unsaturated resin handicraft industry, candle craft, plastic toy industry, gift stationery industry, plaster Craft gift industry, “mold manufacturing industry, “Poly industrial products”, simulation of animal and plant sculptures, Buddha carving handicrafts and other products copy and mold production.
Mainly used for toys, gifts, products with fine patterns, used for overmolding, infusion mold products, glass crafts, lighting, candles, character copy making molds, large products, split molds, reliefs, Buddha statues, craft gifts
Making molds, shoe sole models, pouring molds, and turning sand casting.
The specific operations for different uses of mold silicone are also different. To meet the requirements, specific operations must be performed according to various parameters.
Link to this article：Silicone Mold