There are many differences between condensed silicone rubber and additive silicone rubber in product packaging form, usage, and performance (Figure 2), such as curing speed, body strength, adhesion, etc., but each has its own advantages.

1. Packaging form
Condensed silicone rubber can be packaged in either single component or dual component packaging. Additive silicone rubber, as a temperature sensitive product, requires the separation of the catalyst and crosslinking agent, usually in a two component packaging form to avoid reactions during storage. Of course, there are currently two types of single component addition molded silicone rubber products on the market: one is the low-temperature storage type, which requires storage and transportation under frozen/refrigerated conditions and is inconvenient to use; Another type is room temperature storage, which uses a special structure of catalyst and inhibitor and does not have reaction activity at room temperature. At high temperatures, the catalyst activity is released to achieve cross-linking and curing, but the cost is high and the curing temperature is also relatively high.

2. Curing speed
Due to differences in curing mechanisms, there is a significant difference in the curing speed between condensed and additive silicone rubber. Condensed silicone rubber (mainly referring to single component) reacts from the surface with the help of moisture in the air, gradually vulcanizing from the surface to the inside. Deep curing is slower, and usually takes 24 hours or even a week to fully vulcanize. Addition silicone rubber can be vulcanized at both room temperature and high temperature. Under room temperature conditions, the internal and external vulcanization of the rubber compound is relatively consistent, without any obvious order. Under high temperature conditions, the curing rate has a very wide adjustability with temperature, and the rubber can achieve rapid vulcanization within 5 minutes or even 1 minute under baking conditions. It should be noted that under heating conditions, the curing rate of added silicone rubber is related to the thickness of the adhesive, the heat transfer of the substrate, and the blowing effect of the baking equipment. The specific application situation is analyzed in detail.

3. Body strength
Both condensed and added silicone rubber can be reinforced with fillers such as nano calcium carbonate and fumed silica to enhance their mechanical properties, with fumed silica having the most significant reinforcement effect. Due to the difference of systems, the condensed silicone rubber usually uses nano calcium carbonate as the main reinforcement filler, and the addition amount of fumed silica is limited, so the tensile strength is low, generally not more than 3MPa, while the added silicone rubber generally uses fumed silica as the reinforcement filler, and its addition amount can be increased to more than 30% through the treatment of Bis(trimethylsilyl)amine and other modifiers, and the tensile strength can reach more than 10MPa, Far surpassing condensed silicone rubber.

4. Adhesion
Condensed silicone rubber can achieve adhesion to various materials by adding silane coupling agents. Therefore, the vast majority of adhesive and fixing sealants in fields such as construction, home appliances, lighting, rail transit, and photovoltaics currently use condensed silicone rubber, which is based on its good adhesion and wide adhesion. However, the adhesion of addition formed silicone rubber is far inferior to that of condensed silicone rubber, which is related to its low molecular chain polarity and the absence of polar groups that can react with coupling agents in the molecular chain. Additive silicone rubber generally improves adhesion through the following three methods: (1) surface treatment of the substrate using a primer; (2) Adding a special structure of tackifier,