Common Characteristics to Organic Silicon Coupling Agents
Release Time: 2022-12-01 12:53:00
Common Characteristics to Organic Silicon Coupling Agents
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In some previous articles, we have introduced the basis of organic silicon coupling agents. Even though there are many different types of organic silicon coupling agents, there are also many common properties between them. For example, when we refer MSCA and SCA which are two types of common silicon coupling agents, both of their chemical structures contain a silicon functional group (usually written by an alternative “X”) and organic functional group (written by an alternative “Q”). What is more, they both have the connective groups R’ or large molecular chains which link the silicon functional group and the carbon functional group with inertia. They also have the silicon-carbon chemical key inertia hydroxyl R. The possible chemical reactions made by the silicon functional groups of different organic silicon coupling agents are basically similar while the chemical reactions made by carbon functional groups are more different.
Chemical Reactions of Silicon Functional Groups
The silicon functional groups in organic silicon coupling agents include alkoxy like –OMe, acyloxy like –OAc and others. Even though silicon and silicon function groups are connected by covalent bonds, but their ionization feature is larger (like Si-O key is 50%, Si-Cl key is 30%, Si-N is 30%), and their ionic bond energy is smaller (like Si-Cl key is only 795kJ/mol). Therefore, the silicon functional groups in the silicon coupling agents have properties of inorganic chemicals. The bonding and breaking of silicon and silicon functional groups in chemicals are determined by the concentration degree of the matters during the corresponding reactions. Agents could change the reaction speed. If do not break the balance during the reaction processes, then the proportion of the final products and types will not be influenced.
Silicon material has d-election to form the chemical key and its coordination number is greater than 4 and its electronegativity is only 1.8. It is the metalloid. Therefore, the silicon functional groups in the organic silicon coupling agents are easier to be reactive through the processes of SN2 reactions. Different types of silicon coupling agents could have condensation, alcoholysis and hydrolysis and lead to the acceleration of reactions with the cooperation of acid or alkaline; but the difficulty of the reaction is different according to the different chemical structures and the size of groups of silicon functional groups of organic silicon agents. Also, it is also influenced by the electronic effect, the space factors and the PH value of carbon functional groups.
Properties of Carbon Functional Groups
The chemical properties of carbon functional groups in silicon coupling agents are similar with the chemical characteristics of the organic functional groups in the organic chemicals or macromolecular polymers. The reactions which may occur during the organic chemistry or macromolecular chemistry will also be possible to appear in the carbon functional groups in organic silicon compounds. It is due to the carbon functional groups are easy to have hydrolysis, if we fail to control the reaction conditions well, we will not get the expected results from the corresponding reactions. If we want to use the cyano in the coupling agents to hydrolyze the silicon coupling agents which have hydroxyl, the silicon functional groups will have hydrolysis too and it will be way easier to get polysiloxane which has hydroxyl.
By making full use of the reactive features of carbon functional groups in silicon functional groups, we could form new organic silicon compounds and new silicon coupling agents. We could also lead the silicon functional groups which are easy to hydrolyze to organic polymers to get new macromolecular materials.
Today’s macromolecular organic silicon monomers which are used to modify organic materials could be made via silicon coupling agents. By using the reactive features of carbon functional groups, enzyme could be stabilized on the diatomite and other inorganic materials. Now researchers who are focusing on optical products or materials are always applying silicon couping agents. The functioning of organic materials is also one of the hot spots of modern material studies.
Carbon Functional Group & Silicon Connective (-R’-) Groups on Properties
When the carbon functional groups of silicon coupling agents bond to the methyl, the carbon functional groups will have chemical stability. When –R’- group is arylene, the heating resistance of this silicon coupling agent is higher than other carbon functional groups over 100 Celsius degrees. Therefore it is better to apply it in heating-resistance coating or organic materials, but it is more difficult to produce organic silicon coupling agents like it.
Andrianov and others have studied the hydrolysis and condensation of methyl and other functional groups. The experiments show that the stability of R will become more stable since the size of R is bigger.
It is according to the research mentioned above, although it is not the hydrolysis of orgnic silicone compounds who have carbon functional groups, but the –R’- still has influences on the hydrolysis and condensation of silicon coupling agents and it is a must to consider the effects made by –R’- when producing & applying silicon coupling agents.
Common Properties among Macromolecular Compounds
MSCA and SCA’s reactive functional groups have the same or similar chemical structures; they will not have many differences during reactions. The difference between MSCA and SCA is that MSCA has polymer chains which are designed to aim at composite materials. These chains allow MSCA has better influences on composite materials: the strengths, modulus and toughness of composite materials could be improved at the same time.
MSCA’s polymer chains are long and reactive, thus they could be applied to cover powders of mines or other inorganic materials and to make the surfaces of the inorganic materials to be organic then to improve the corresponding composite materials’ modifying effects.
MSCA’s polymer chains could also be made or processed by different methods to make polymers in different shapes.
Also, the MSCA could reduce the quantity of the produced VOC which is popular today. This is another point why SCA fails.