What problem you might have with your liquid silicone
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What is LSR ?
Liquid Silicone Rubber with low compression set, fast cure cycles, great stability and ability to resist extreme temperatures of heat and cold can makes itself being ideally suitable for the high standard quality production application. Unlike most thermoplastic elastomers, LSR remains flexible and elastic down to -60 centigrade and retains its properties up to 200 centigrade. In addition to these properties, the wide range of hardness and colors, silicone elastomers have become the material of choice for an ever increasing amount of applications.
Typical applications for liquid silicone rubber are products that require high precision such as seals, sealing membranes, electric connectors, multi-pin connectors, infant products where smooth surfaces are desired, such as baby nipples, medical applications as well as kitchen goods such as baking pans, spatulas, etc.
Characteristics of LSR:
Durable: LSR parts can withstand extreme temperatures, which makes them an ideal choice for components under the hood of cars and in close proximity to engines. Parts fabricated via liquid silicone rubber injection molding are fire retardant and will not melt.
Chemical resistance: Liquid silicone rubber resists water, oxidation and some chemical solutions such as acids and alkali.
Temperature resistance: Compared to other elastomers, silicone can withstand a wide range of high/low temperature extremes.
Mechanical properties: LSR has good elongation, high tear and tensile strength, excellent flexibility and a hardness range of 5 to 80 Shore A.
Electrical properties: LSR has excellent insulating properties, which offer an appealing option for a host of electrical applications. Compared to conventional insulating material, silicone can perform in far higher and lower temperatures
How to make silicone mold with diy silicone mold kids to have silicone mold making.
Different between Tin cure and Platinum cure liquid silicone
The chemical difference between tin-cure (condensation cure) and platinum-cure (addition cure) silicone mold making rubbers lies mainly in the metal used to catalyze or cure the base rubber. The metal tin is used to catalyze or cure tin silicone, and platinum is used to cure platinum silicone rubber. Accordingly, tin-cure silicone rubbers are usually significantly less expensive than platinum-cure ones.
All mold making rubbers may be subject to cure inhibition by contaminants on the surface of a model being used for mold making. Silicone rubber is sensitive to sulfur that can be found on different surfaces and are present in some types of modeling clay. Platinum-cure silicone rubbers are critically sensitive to sulfur and will not cure under any circumstances when exposed. Tin-cure silicone can cure over models containing sulfur if the model surface is first thoroughly sealed with an acrylic spray.
A major difference between these two systems is shrinkage of the cured rubber over the short and long term. Tin-cure silicone rubber molds generally exhibit higher shrinkage over time depending on the type of mold rubber being used, material being cast into the rubber mold, mold configuration, and other variables.
Tin-cure silicone rubber molds have a limited library life. Depending on the specific tin-cure silicone, the library life of a rubber mold can be as little as 6-8 months, which may be acceptable if your project is short term.
Platinum-cure silicone has a relatively long library life that is measured in decades. Museums choose platinum-cure silicone rubbers to make molds of valuable artifacts and works of art.
Which silicone rubber chemistry (tin vs. platinum) will give you the longest life for production casting of wax, gypsum, concrete, resin, etc.? It depends on different variables and is usually application specific to determine which rubber mold material is right for your project, contact us easily to find out which kind of silicone is suitable for your project.
What makes Platinum cure silicone not cure
If your silicone is not curing, make sure to not have any contact between the uncured silicone and the following substances:
· Tin (Sn): Are present in for example 1 component silicone ahesives (condensation curing) as well as 2 component condensation curing silicones. Also present in some types of PVC plastic.
· Nitrogen coumponds such as amides, amines, nitriles, cyanates etc.
· Sulphur compounds: Present is for example latex, natural rubber, neoprene, PVC, wood, oils and some solvents. Consider the types of protective gloves you are using when working with a platinum-catalyzed silicones and not using a wooden spatula to mix it.
· Some metals such as silver, tin, lead and mercury.
· Some epoxies and polyurethanes.
What is the hardness we should choose
Normally, different size of silicone mold should be select according to different product's features.
For example :
* Recommend product AS220
For products size ( within 20 cm ) : With fine designs, soft silicone is suitable, suggest 10-20 shore A.
* Recommend product AS225
For products size ( 20cm-80cm ) : With fine designs, suggest 20-25 shore A. With simple designs, suggest 25-30 shore A.
* Recommend product AS225 or AS230
For products size ( 80cm-150cm ) : With fine designs, suggest 25 shore A. With simple designs, suggest 30-35 shore A.
* Recommend product AS225 with brush on method or AS230
For products size ( more than 150cm ) : With fine designs, suggest 25-28 shore A. With simple designs, suggest 35-40 shore A.
How to make mold with Tin cure silicone ?
Operation instructions Step 1: prepare the original molds Make sure your original molds perfect, use release agent if needed. Fix the original mold on a board, find suitable size frame for the original mold. ( normally 1 cm frame space ).
Step 2: Take 100 G parts A and add 2G parts B and mix them evenly. Notes: Mold making silicon rubber is a kind of flowing liquid, It contains two parts. Part A is a kind of flowing white liquid and part B is the curing agent or catalyst .Please follow the step strictly: 1.Weigh the two part exactly by electronic weight.. If not, for example add two much catalyst, the operation time will be too fast and not able to operate, which will cause inconvinience to operate . 2.Mix part A and part B evenly.
If not mix well, the silicon rubber will be partly solidified, then the mold will be not able to use.
Step 3: Pouring casting or Brush operation Notes:
1. For simple pattern products we suggest use pouring operation way, which will be very easy to operate and demould.
Pourable silicone require light viscosity which will be easy to flow smoothly and easy to de-air. 2.For delicate pattern products we suggest use brushing operation way, which can copy the pattern exactly. Brushable silicone require high viscosity which won't be easy to flow away and easy to brush . 3. We suggest, to set the silicone mold for another 12 hours after demold before put into large production.
How to make mold with Platinum cure silicone ?
1: Prepare the desired molds
Prepare a desired mold and clean it before operation.
Notes: Make sure the desired molds and operation tools were cleaned up to avoid uncured problem.
( Suggest to use stainless steel or wooden material mixer. )
2: Take amount Part A :100 g / Part B :100 g ( or Part A : 100 g and Part B :10 g ) and mix evenly.
* Weigh the two part exactly by electronic weight. If any part not in exactly weight, it may cause changing of hardness, or even cause uncured problem.
* Mix part A and part B evenly.
3: Vacuum the mixed material
This step must less than 10 minutes. Otherwise, it will cause cross linking reaction, might cure too fast.
4: Pouring casting
* For simple mold, just to pour the vacuumed material into mold, cured will be 8-12 hours.
* For fine designed mold, to brush the liquid silicone on mold surface then pour the silicone into mold. This will make the casing properly.