production of selected secondary metabolites in transformed ...
production of selected secondary metabolites in transformed ...
production of selected secondary metabolites in transformed ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
PHYSICAL-CHEMICAL ASPECTS OF PAINT FILMS DEGRADATION<br />
Ing. Lucie Wolfová<br />
Supervisor: pr<strong>of</strong>. RNDr. Zdeněk Friedl, CSc.<br />
Brno University <strong>of</strong> Technology, Purkyňova 118, Brno 612 00, e-mail:wolfova@fch.vutbr.cz<br />
INTRODUCTION:<br />
My dissertation thesis deals with the physical-chemical aspects <strong>of</strong> pa<strong>in</strong>t film degradation.<br />
This work is focused on the study and exam<strong>in</strong>ation <strong>of</strong> physical-chemical aspects <strong>of</strong> pa<strong>in</strong>t film<br />
degradation by <strong>selected</strong> solvents. Ma<strong>in</strong>ly it is considered to the determ<strong>in</strong>ation <strong>of</strong> solubility<br />
parameters <strong>of</strong> used polymers δ2 and the exam<strong>in</strong>ation <strong>of</strong> the <strong>in</strong>fluence <strong>of</strong> especially polymer<br />
structure to the value <strong>of</strong> this δ2. The ma<strong>in</strong> goal <strong>of</strong> this study is to verify the coat<strong>in</strong>g solubility<br />
theory based on the knowledge <strong>of</strong> their solubility parameters <strong>in</strong> practise and its application for<br />
coat<strong>in</strong>gs. The other goals <strong>in</strong>clude the projection and formulation some new solvent’s mixture<br />
and additives <strong>in</strong>tended for remov<strong>in</strong>g pa<strong>in</strong>t films and graffiti. Such formulation need to be well<br />
perform<strong>in</strong>g and ecological acceptable at the same time, which is the precondition for their<br />
wide application <strong>in</strong> practise.<br />
THEORETICAL BACKGROUND:<br />
Chemical degradation <strong>of</strong> pa<strong>in</strong>t films could be def<strong>in</strong>ed as the physical and chemical<br />
<strong>in</strong>teractions between film-form<strong>in</strong>g components <strong>of</strong> the pa<strong>in</strong>t and chemical surround<strong>in</strong>gs.<br />
Dur<strong>in</strong>g the chemical degradation <strong>of</strong> polymer a disruption <strong>of</strong> cha<strong>in</strong>s and reticulation, a change<br />
<strong>of</strong> chemical structure <strong>of</strong> cha<strong>in</strong>s, a change <strong>of</strong> side groups or comb<strong>in</strong>ation <strong>of</strong> all these<br />
phenomena take place. This leads to changes <strong>in</strong> pa<strong>in</strong>t qualities and coats lose their visual<br />
appearance and orig<strong>in</strong>al qualities upon the exposure to organic solvents.<br />
From the thermodynamic po<strong>in</strong>t <strong>of</strong> view, a solubility <strong>of</strong> polymer and a degree <strong>of</strong> solvent<br />
aff<strong>in</strong>ity to polymer is given by the Gibb´s energy change, which is determ<strong>in</strong>ed by the<br />
<strong>in</strong>teraction between solvent molecules and macromolecular cha<strong>in</strong> elements. ΔGmix = ΔHmix -<br />
TΔSmix < 0.<br />
The more negative is value <strong>of</strong> ΔGmix the better is solubility <strong>of</strong> polymer <strong>in</strong> solvent. Then the<br />
dissolv<strong>in</strong>g <strong>of</strong> polymers is ma<strong>in</strong>ly a question <strong>of</strong> value ΔHmix because dur<strong>in</strong>g swell<strong>in</strong>g or<br />
dissolv<strong>in</strong>g always <strong>in</strong>crease system’s disorderl<strong>in</strong>ess. Accord<strong>in</strong>g to thermodynamic conditions<br />
than is necessary that ΔHmix
Change language