In silicone adhesive formulations, tin catalysts typically exist in the form of organotin compounds, such as dibutyltin dilaurate (DBTDL) or dibutyltin diacetate (DBTDA). These organotin compounds act as catalysts to initiate the crosslinking process of silicone adhesives by promoting the cross-linking of silicon molecules. There are two main types of catalysts: tin-platinum, let’s find out how the tin-free silicone can be dominant, and solution to optimize the production process with these materials.
1. Comparison between Tin and Platinum Catalysts
Silicone rubber is processed using Tin (condensation cure) and Platinum (addition cure). Both types have advantages and disadvantages and are not compatible with each other. They offer excellent strength, flexibility, and self-release properties. Silicone rubber processed by Tin (condensation) cure utilizes tin salts as catalysts and ambient moisture to transition from liquid to solid form. Silicone rubber processed by Platinum (addition) cure employs platinum catalysts and heat to transition from liquid to solid form. Platinum-cured silicone can be accelerated by heat, with processing time halved every 10 degrees above 70°F. Therefore, if you heat platinum-cured silicone at 150°F, it will be ready for use in 20-30 minutes.
Tin (condensation) cure
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Platinum (addition) cure
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Therefore, silicone adhesives using Platinum catalysts are considered safer than those using Tin catalysts for medical, food, and other applications requiring high safety standards.
2. Reasons behind the Trend
Silicone adhesives without tin have become prevalent for several reasons:
- Legal Pressure: Regulatory agencies worldwide have imposed restrictions on the use of certain organotin compounds due to their potential environmental and health hazards. Organotin compounds like DBTDL and DBTDA can leach into the environment, posing dangers to aquatic life and potentially harming human health. Regulatory bodies such as the Environmental Protection Agency (EPA) in the United States and the European Chemicals Agency (ECHA) have implemented regulations to limit the use of these compounds in consumer products.
- Environmental Concerns: Organotin compounds are known to persist in the environment and can bioaccumulate in organisms. As awareness of environmental issues grows, pressure on industries to adopt more sustainable and environmentally friendly practices increases.
- Consumer Preferences: Consumers are increasingly conscious of the ingredients used in the products they purchase. They often prefer products free from potentially harmful chemicals, including organotin compounds. Manufacturers respond to this demand by improving their silicone adhesive formulations to eliminate tin, thereby appealing to environmentally conscious consumers.
- Technological Advancements: Advances in catalyst and silicone chemistry have facilitated the development of tin-free silicone adhesives capable of curing without organotin compounds. For example, noble metal catalysts provide an effective alternative for initiating cross-linking reactions in silicone adhesives or modified silicones.
3/ Solution for Manufacturers
For substitutes to tin catalysts, manufacturers can utilize noble metal catalysts or modify silicone formulations to achieve curing without tin. Noble metal catalyst-based silicone adhesives are widely used and offer excellent performance, although they may be costlier than tin-catalyzed formulations. Modified silicone formulations can employ alternative catalysts or curing mechanisms to achieve similar results without relying on tin. These substitute options enable manufacturers to produce silicone adhesives that meet legal requirements and customer expectations regarding performance and environmental responsibility.
The trend towards using tin-free silicone material products is becoming a phenomenon due to environmental friendliness and advancements in the industry. Prostech takes pride in being a leading provider of a diverse range of tin-free silicone material products from renowned brands worldwide, along with tailored manufacturing solutions to suit each stage of your production process. Contact Prostech to discuss with our experienced experts.
4/ Moisture-curing Modified Silicone Adhesive (Tin-free)
Tin-free modified silicone adhesive formulations have been developed in response to EU restrictions on dibutyltin (DBT). These formulations are modified silicone adhesives capable of moisture curing. Upon reacting with ambient moisture, they release neutral alcohol and undergo curing.
Tin-free modified silicone adhesives have gained popularity due to their improved environmental and health safety compared to traditional tin-containing silicone adhesives. They are commonly used across various industries, including the 3C industry (Computers, Communications, Consumer Electronics), for applications such as bonding and casting. The absence of tin compounds helps alleviate concerns regarding toxicity and environmental impact. Additionally, their moisture-curing properties and lack of strong odors make them user-friendly.
Overall, the removal of tin from silicone adhesive products reflects a combination of regulatory, environmental, consumer-driven, and technological factors, all contributing to the transition towards safer and more sustainable formulations.
Some suggested products:
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