# Quality Analysis of Bonded Joints in the Renovation of Plastic Automotive Parts
## 4 Discussion  
Since several adhesives are used in practice, it is useful to know their behaviour in terms of strength. As the application of adhesives is in the field of renovation, it must be considered that these adhesives in the form of joints of plastic parts are exposed to various external influences. Therefore, the aim of this paper was to select the three most widely used adhesives and compare them with each other, with tensile and impact tests being chosen as evaluation tests. The selection of the chosen tests was due to the most common stressing of plastic parts in practice. To complete the knowledge of the strength of the adhesive used, bonded joints of three different thicknesses were created and then subjected to the effects of the sprinkling agents based on simulated industrial operating conditions. In the case of tensile properties, this involved exposure in an environment with the presence of SO2 and exposure for 1 year under realistic atmospheric conditions. In the case of impact strength, the environments chosen were the ones with the presence of SO2, the 20% salt solution environment, and, again, exposure for 1 year under realistic atmospheric conditions. The adhesive thickness significantly influences the load-bearing capacity of the joints. Experimental work has confirmed the dependence of the adhesive thickness and the strength of the joint. It depends on the specific type of adhesive, the method of loading, and the conditions to which the joint is subjected. The effect of weather conditions is to degrade and reduce the strength properties of adhesives used in bonded joints. The degree of degradation depends on the specific loading  
Figure 16: Impact strength comparison for different environments for all adhesives used. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Adhesive**} & **Average Impact** & **Average Impact Strength** & **Average Impact** & **Average Impact** \\  & **Strength [kg.cm\({}^{-1}\)]** & **[kg.cm\({}^{-1}\)]** & **Strength [kg.cm\({}^{-1}\)]** & **Strength [kg.cm\({}^{-1}\)]** \\  & **After Curing** & **Condensation Chamber** & **Salt Solution** & **1 Year** \\ \hline Megabond 2000 & 32.16 & 3.68 & 3.2 & 14.88 \\ ChS EPOXY 1200 & 23.84 & 4.96 & 7.2 & 30.24 \\ DINITROL 860 & 15.68 & 4.48 & 6.7 & 21.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 23: Measured impact strength values for each environment used. conditions and the type of adhesive used. The reduction of the mechanical properties of the bonded joint can negatively affect its strength. Bonding allows flexible fixation of sheet metal while achieving higher stiffness and strength of the car body. Degradation of the adhesive can reduce the tightness of the joints, which affects the anti-corrosion properties of the bodywork and the service life of the vehicle. The adhesive layer, therefore, represents an electrical isolant, which, by breaking the integrity of the joint, can cause electrolytic corrosion. Similarly, a breach in the integrity of the bond may also increase the sound level of the vehicle as well as reduce the strength of the bodywork in the case of crashes. The individual results demonstrated the following claims:  
1. The highest values of load at failure after curing were achieved by ChS EPOXY 1200, a lower value was achieved by DINITROL 860, and the lowest value was achieved by MEGABOND 2000. 2. When comparing the adhesives used and the individual adhesive thicknesses of 0.1 mm, 0.25 mm, and 0.33 mm, with respect to the post-cure condition and after exposure to an environment with SO2 present, there was a decrease of load at failure with the change in environment for each adhesive. The least affected results were obtained from the ChS EPOXY type adhesive compared to the MEGABOND 2000 and DINITROL 860 adhesives. For the MEGABOND 2000 adhesive, the most significant difference was achieved at 0.33 mm thickness, more than four times the values measured after curing.