Evaluation of factors affecting repaint adhesion of automotive coating systems
Typ
Examensarbete för masterexamen
Program
Materials chemistry (MPMCN), MSc
Publicerad
2021
Författare
Koca, Firat
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
As it is today, when for some reason a car body needs to be repainted in the factory,
either because of defects, or because an additional colour is to be applied, the body
must go through a step called sanding. Sanding is a process where the top layer
of the car body coating is being grinded. This is required in order to prepare
a surface on which a required adhesion can be achieved. However, with sanding
comes consequences. The process of sanding takes time and additional place on
the conveyor belt, which in turn costs a lot of money and reduces the productivity.
An additional negative side effect is that the sanding causes pollutant particles in
the air in the factory, which leads to other car body coatings to get defects, which
in turn leads to additional car bodies requiring repainting and sanding. Thus, a
vicious circle is created. It is therefore desired to skip sanding. It is suspected that
different factors and processes from the painting process have different influence on
the repaint adhesion. In this work, the goal was to evaluate some of these factors
influence on the repaint adhesion. This was done by applying coatings to test
panels in a procedure simulating the steps in the factory. The repaint adhesion was
evaluated by exposing the panels to a high pressure car wash jet. Examples from the
factors evaluated are, curing time and temperature. Also, different coating materials
and properties of the repainted surface, such as surface energy and hardness were
among the factors evaluated. This work resulted in the findings that, among the
factors evaluated, the most significant was those concerning the curing of the clear
coat, namely, curing time and temperature. Also, indications, that suggest that the
amount of rest-isocyanate on the repainted surface could have an influence on the
repaint adhesion, was observed.
Beskrivning
Ämne/nyckelord
Adhesion , repaint, , automotive coating systems , car wash jet