Surface modification and edge layer post curing of 3D sheet moulding compounds (SMC)

Abstract

Incomplete curing of sheet moulding compounds (SMC), as well as the post-curing and outgassing during the industrial thermal coating process, are the two main reasons for the coating problems of SMC Class-A automotive parts. Furthermore, their surface properties as contact angle and surface roughness strongly depend on the processing parameters of thermal curing and coating as well as cleaning and pickling methods used. Consequently, cost and energy-intensive additional process steps are required in the automotive industry in order to reduce or avoid above mentioned problems during the industrial coating process of SMC-Class-A automotive parts. A cost-efficient robust procedure is required in order to overcome these disadvantages as well as to fulfil the requirements of the industrial coating process. Based on electron beam curing and surface functionalization by low energy electrons a novel pre-treatment procedure was developed and tested. For this purpose, two different compact electron emitters have been coupled to an industrial robot in order to validate this novel in-line pre-treatment procedure. Through this one-step treatment, post edge-layer curing and surface functionalization of the three-dimensional SMC-parts are achieved.