Introduction to Silicone Resin
Release Time: 2022-12-22 10:59:26
Introduction to Silicone Resin
Cited from: https://pixabay.com/photos/resin-tree-resin-discharge-resins-3300122/
Cover page cited from: https://pixabay.com/photos/snow-winter-cold-frost-frozen-3143778/
We have discussed much on different types of silicone oils before. Today, we are going to introduce another type of famous silicone products- silicone resins.
Silicone resins are high-crossing thermoset polymers that contain bifunctionality, trifunctionality and even treta-functionality.
Silicone resins are the earliest ones of organic silicone materials. However, if we compare them to silicone oil or silicone rubber, the amount of types of silicone resins is smaller and silicone resins also have smaller silicone resins. But it is since there are many unique properties on silicone resins; they will not be altered by other materials easily and thus also applied in many different industries.
There are four types of structural units which are forming silicone resins: SiX4, RSiX3, R2SiX2 and R3SiX. In these units, the T unit or Q unit which are able to form solid 3-dimensional structure are must. They could be made to silicone resins by combining D units and M units. It is similar with the structure of glass; the bone structure of silicone resins is also the amorphous 3-dimensional structure which is constructed by SiOSi chemical key. However, the silicon in glass is all Q units and it is inorganic structure which leads to a high processing temperature. For silicone resins, their structure’s partly or whole silicon atoms all contain methyl, phenyl and similar functional groups and have a flexible structure. This will lead to the enhancement on the processing properties and corresponding affinity to organic materials which will make it easier to be soluble to organic solvents and convenient applications.
The silicon atoms’ substituent groups of silicone resins are mainly methyl, to put some phenyl could improve corresponding thermoelasticity and cohesiveness; to lead ethyl, propyl and long-chain alkyl could improve the affinity to organic materials and hydrophobicity; to use vinyl and hydrogen could lead to platinum agent reaction and has crosslinking reaction with superoxide; to use carbon functional group, the products could be reacted with more organic chemicals and improve corresponding cohesiveness. It is according to these, the silicone resins have formed a group of products.
Categories of Silicone Resins
Silicone resins could be categorized by its elements of structures. The four structure units of silicone resins which are MDTQ have 15 types of possible combinations. Among them, DM, DD and MM could not be used to form branching or crosslinking forms which mean they could be used to manufacture silicone resins. Also, the QQ which is fully condensate is silicon dioxide. The combinations which contain Q are hard to be seen unless MQ. All other combinations like TD, TM, TDM and TT are applied successfully in industry. Silicone resins could also be divided by the organic substituent groups which are connected to silicon atoms like methyl silicone resins, phenyl silicone resins and methyl phenyl silicone resins. It is in order to improve some properties of silicone resins and to increase their application scopes, silicone resins could also be modified by using organic resins. The common organic resin modified silicone resin includes organic silicone polyester paint, organic silicone alkyd resin paint, organic silicone acrylic resin paint and many others. The silicone resins which contain carbon functional groups are also considered as one type of modified silicone resin.
Silicone resins are reacted via hydrolysis or alcoholysis of the monomers like QT, QD, QM, TD, TM, DM, QTD to form prepolymer and then to have solidification via different chemical reactions according to different applications. By the differences of methods of crosslinking and solidification, silicone resins could be divided to three types- condensate type, superoxide type and addition type.
Condensation reaction is the earliest and the most common mechanism of silicone resin solidification reaction. Even if now, most types of silicone resins are using condensation reactions. Although the new siloxane chemical keys produced by condensation could make full use of the heating resistance of silicone resins, but, it is due to the foams will be produced during the process. Therefore, most of these reactions are used on the surface paintings.
The solidification reactions led by superoxide are free radical reactions. The beginning of the solidification is determined by the decomposition temperature of the superoxide. It is due to the reaction will not be started under room temperature; therefore the stability of storage of single-component superoxide silicone resin is good. However, it must be noticed that the air will curb the surface solidification of this type of silicone resins.
The solidification mechanism of additional silicone resins is the hydrosilylation with the agent of platinum. It is due to the process of solidification does not produce any small molecular compounds, thus there are no disadvantages like producing foams or high shrinkage rate which are common in condensation. Therefore, this reaction could allow collecting accurate-sized solidification products. At the same time, it is due to it is easy to control the quantity of reactive functional groups; therefore it could easily adjust the properties of products effectively to get the mature products from hard ones to soft ones.
If we categorize the types of silicone resins by the conditions of solidifications, they could be divided to four types as well- thermosetting, dried, solidification and light-curing.
If we summarize them by the forms of products, silicone resins could be divided to solvents, non-sovlents, water solvent and water lotion. Solvent silicone resin is the main product form, it is to put silicone resin prepolymer to be soluble to phenyl or toluene or xylol liquids to be constructed. The viscosity of silicone resin solvents is pretty low and it is good for painting. It is also easy to mix or spread the powders of filling or paintings; they are the basic forms of the basis of inks. However, if the layer of silicone resin is too thick, there will be foams which will pollute the working environment and even lead to a high risk of explosion. Therefore, the operators must ensure the ventilation of the working environment especially if the working place is im-room.