Thermodynamic Changes, Properties and Types of Function

A thermodynamic system refers to the physical process or the chemical reaction at the centre of interest. 

CLOSED SYSTEM - no material is exchanged with the surroundings (e.g. autoclave - a sealed vessel for carrying out high pressure reactions). 

OPEN SYSTEM - material is exchanged (e.g. by evaporation) with the surroundings. The system does not have to be OPEN in order to change the amounts of substances present this can occur by chemical reaction or interphase transfer within a closed system. 

CHEMICAL - involving reaction and chemical change or PHYSICAL - involving physical change (e.g. variation of pressure, P, or phase such as in boiling (liquid - vapour). 

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The adhesion properties of all types of polyolefins are not easy to explain because these properties are affected by different phenomena. Using of a single theory or mechanisms based on the physical and chemical adhesion manifestations is difiicult for the description of interdisciplinary nature and diversity. There is considerable information to discuss each of the adhesion mechanisms. Therefore, it is not possible to select only the thermodynamic theory of adhesion that is the best to describe the surface free energy of the polyolefin. All mechanisms and adhesion theories are implied by the diversity of polymer systems, which are embraced in combination with research for the analyses of adhesion properties. The physical and chemical composition in the first atomic layers dictates the adhesion and some other properties of the polymer materials. This layer represents underneath layer and this subsurface partially controls the outer layers. The double bonds and cross-linked stmctures limit the mobility macromolecules of polyolefins in the subsurface layers, which results in the functional group stabilization on the surface. Other basic research is necessary for an examination of the polymer subsurface layer and explanation of its effect changes of the surface properties. Moreover, for the improvement of quantitative measurements of adhesion, additional investigation is required. 

The principal business of this chapter is to establish the thermodynamic relations obeyed by two or more phases that are at equilibrium with each other. A phase is a portion of a system (or an entire system) inside which intensive properties do not change abruptly as a function of position. The principal kinds of phases are solids, liquids, and gases, although plasmas (ionized gases), liquid crystals, and glasses are sometimes considered to be separate types of phases. Solid and liquid phases are called condensed phases and a gas phase is often called a vapor phase. Several elements such as carbon exhibit solid-phase allotropy. That is, there is more than one kind of solid phase of the element. For example, diamond and graphite are both solid carbon, but have different crystal structures and different physical properties. With compounds, this phenomenon is called polymorphism instead of allotropy. Most pure substances have only one liquid phase, but helium exhibits allotropy in the liquid phase. 

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