## 3 Results and Discussion of Conducted Laboratory Research
From Figure 14 it can be seen that, after 15 min of testing, for the Teflon block in polymer fluid without weighting additives but with lubricant X and Z at a concentration of 2% vol., the friction force was higher than for the one with lubricant Y at the same concentration of 2% vol., and for all three lubricants, X, Y and Z, it can be seen from the first 5 min to 15 min of testing that the friction force value has slightly changed. Figure 15 shows the comparison of three lubricants, X, Y and Z, added at a concentration of 2% vol. to polymer fluid with weighting additives (PWL2). \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**PL2**} & \multicolumn{3}{c}{**PWL2**} \\ \cline{2-7}  & & **X** & **Y** & **Z** & **X** & **Y** & **Z** \\ \hline \multirow{3}{*}{Friction factor} & Steel block & 0.292 & 0.482 & 0.134 & 0.344 & 0.336 & 0.29 \\ \cline{2-7}  & PA6 & 0.11 & 0.1 & 0.074 & 0.145 & 0.164 & 0.105 \\ \cline{2-7}  & Teflon & 0.039 & 0.031 & 0.032 & 0.054 & 0.046 & 0.08 \\ \cline{2-7}  & POM & 0.089 & 0.073 & 0.066 & 0.126 & 0.158 & 0.116 \\ \hline \end{tabular}
\end{table} 
Table 3: Friction factor for each block made from different material in polymer mud with and without weighting additive in which one of two lubricants X and Y is added at a concentration of 2% vol. Figure 14: Comparison of friction forces measured on the block made from Teflon in polymer drilling fluid without weighting additive (PL2) and with one of three lubricants, X, Y and Z, at a concentration of 2% vol. From Figure 15 it can be seen that, after 15 min of testing, for the Teflon block in polymer fluid with weighting additives with lubricant Z at a concentration of 2% vol., the recorded friction force was the highest, followed by lubricant X, while lowest value was recorded with lubricant Y. For both lubricants X and Y, it can be seen from the first 5 min to 15 min of testing that the friction force value has slightly decreased, while for lubricant Z the value did not change for all the period of testing. After finishing the measurements of the friction force of the test block made from Teflon in polymer mud with and without weighting agents in which one of two lubricants X and Y were added at a concentration of 2% vol., the next step was to measure the mechanical wear on the previously mentioned device in the Faculty of Mechanical Engineering and Naval Architecture. The test was performed at room temperature with a rotation speed of 60 rpm and the generated load on the test block made from Teflon was 670 N. The weights of the test blocks made from Teflon were measured before the beginning of the test and after the test had finished, i.e., after 24 h. Also, the measurement was conducted using the same mud system that was previously mentioned but KCl was removed from the mud due to the appearance of corrosion in the initial tests that were performed. Figure 13 shows the block made from Teflon before the test (A) and measurement after 24 h (B). In Figure 16A, the surface of the test block made from Teflon is flat, while in Figure 16B, it can be seen that a dent has been formed after 24 h under constant rotation and generated load. Figure 17 shows the mechanical wear of the Teflon blocks after 24 h of testing in polymer mud with and without weighting additive in which one of two lubricants X and Y are added at a concentration of 2% vol. Figure 16: Test block made from Teflon before (**A**) and measurement after (**B**) 24 h.  
Figure 15: Comparison of friction forces measured on the block made from Teflon in polymer drilling fluid with weighting additive and with one of three lubricants, X, Y and Z, at a concentration of 2% vol. (PWL2). From the calculated data that are graphically presented in Figure 17, the mechanical wear of the blocks made from Teflon is higher in polymer mud with weighting additive in which one of two lubricants X and Y were added at a concentration of 2% vol. compared with polymer mud without weighting additive in which lubricant was added at a concentration of 2% vol.