Abstract
In this paper, polysiloxane is used to modify insulation paper cellulose, and molecular dynamics methods are used to evaluate the glass transition temperature and mechanical properties of the paper before and after the modification. Analysis of the static mechanical performance of the model shows that, with increasing temperature, the elastic modulus of both the modified and unmodified cellulose models decreases gradually. However, the elastic modulus of the modified model is greater than that of the unmodified model. Using the specific volume method and calculation of the mean square displacement of the models, the glass transition temperature of the modified cellulose model is found to be 48 K higher than that of the unmodified model. Finally, the changes in the mechanical properties and glass transition temperature of the model are analyzed by energy and free volume theory. The glass transition temperatures of the unmodified and modified cellulose models are approximately 400 K and 450 K, respectively. These results are consistent with the conclusions obtained from the specific volume method and the calculation of the mean square displacement. It can be concluded that the modification of insulation paper cellulose with polysiloxane will effectively improve its thermal stability.
Highlights
The glass transition temperature of a polymer is very important, being the turning point at which a polymer material transitions from a glass state to a highly elastic state [1]
Polysiloxane is a cross-linked polymer with Si–O–Si as the main chain, and silicon atoms connected to other organic groups
When organic substituents are introduced into the polymer, its thermal stability will decrease by 623–873 K, but its heat resistance will still be better than that of common organic compounds
Summary
The glass transition temperature of a polymer is very important, being the turning point at which a polymer material transitions from a glass state to a highly elastic state [1]. The main component of oil-immersed power transformer insulation paper is natural cellulose [2], which is composed of crystalline and amorphous regions. The crystalline region is closely arranged and its structure is stable, meaning that its performance is relatively stable under high temperatures. The amorphous region is loosely and irregularly arranged, and so thermal aging usually starts from the amorphous region [3,4]. The initial mechanical properties of cellulose insulation paper can basically meet the needs of its applications, but after its glass transition temperature changes, its mechanical properties seriously decline [5], which causes the paper to fail to meet the needs of the application. The general operating temperature of a transformer is below 100 ◦ C, but local winding temperatures can exceed
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