The conventional vibration welding process of polyamide 66 only has a continuous and steady melt flow during the quasi‐steady phase. The process and resulting welds have been thoroughly investigated. Radiation cross‐linking of polyamide 66 with electron beams alters the material's characteristics. Consequently, the resulting energy balance during vibration welding changes and the squeeze flow is impeded. Additionally, this causes the cross‐linking to attain a residual stiffness above the crystallite melting temperature, thereby influencing the characteristics of the vibration welding process. Further, higher weld temperatures and a change in meltdown behavior can be observed. This leads to a varied relationship amongst the process, structure, and properties for vibration welding cross‐linked polyamide. Hence, weld strengths up to the value of the base material strength are possible. The scope of this article is to investigate the influence of radiation cross‐linking on the material characteristics and, by extension, the resulting processing and welding characteristics. Calorimetric, chemical, rheological, mechanical, and optical investigations serve to highlight the influence of radiation cross‐linking on the vibration welding process of polyamide 66. POLYM. ENG. SCI., 55:2493–2499, 2015. © 2015 Society of Plastics Engineers
In conventional injection-moulding processes high flow and cooling velocities affect the morphological and tribological properties of microparts when compared to macroscopic parts. A novel mould technology with dynamic CO 2 -tempering is targeted with an enhanced understanding of the temperature time behaviour of morphology during the setting phase which fundamentally dominates the structure formation. The scope of this paper is to provide an understanding of the processing temperature's influence, in this context mould temperature, on the morphological and tribological properties of injection-moulded microparts. Furthermore, the characteristics of tribological testing conditions in microparts should be identified with regard to optimized testing methods. Results indicate that the tribological properties of microparts are mainly influenced by nature of the skin near layers, which can be greatly improved through the application of mould temperatures close to the crystallisation temperature. Additionally, a tribological testing method is adapted for a correct and high solution of the running-in and stationary phase in order to identify the effects of the skin layer on the wear behaviour.
The production of components consisting of various polymer types by welding is severely restricted and only possible for bonding compatible materials with melting points in a close range. Several modifications, such as the cross-linking of one joining partner, allow for circumventing the restrictions regarding the melting points but do not help in joining bonding incompatible materials. Investigations of dissimilar material combinations, especially from polymer-metal hybrid structures, show a high potential of connections based on form fits. Within the scope of this paper, the possibility of joining incompatible polymer combinations, such as polyamide 66 and high-density polyethylene, by micro form fit using the vibration welding process is analyzed. For this purpose, the generated bonding strength of the test specimen was determined by shear tests. Furthermore, the undercuts of the generated prestructures and the resulting bond of the test specimen were examined microscopically by computer-tomography. These investigations depict the high potential of joining incompatible polymer combinations by form fit in the vibration welding using prestructuring to generate undercuts.
Vibration welding of radiation crosslinked polyamide 66 leads to a different relationship between process, structure, and properties. The radiation‐induced altered material properties result in an impeded squeeze flow and higher temperatures in the weld. It is possible to achieve weld strengths up the value of the base material. General theories cannot completely explain the adhesion for these crosslinked polymers. A possible explanation could be an additional temperature‐dependent adhesion mechanism. The high temperatures during vibration welding could affect the degree of crosslinking and lead to a post‐irradiation crosslinking of the polyamide. These additional links across the joining zone may be an additional adhesion mechanism and could explain the high weld strength of crosslinked polymers. The scope of this paper is to investigate the influence on the degree of crosslinking from material and welding parameters and to correlate these results with temperatures and weld strengths generated in a vibration welding process. POLYM. ENG. SCI., 56:735–742, 2016. © 2016 Society of Plastics Engineers
A conventional vibration welding process of fiber‐reinforced Polyamide 66 is characterized by a continuous melt flow in the quasi‐steady phase. This squeeze flow leads to a disadvantageous fiber reorientation in the weld zone. The fibers are oriented parallel to the melt flow and thus perpendicular to the common stress direction. This causes relatively low weld strength compared to the strength of the base material. Radiation crosslinking fiber‐reinforced Polyamide 66 with electron beams influences the material characteristics. As a consequence, the resulting energy balance during vibration welding is changed and the squeeze flow is impeded, thus averting the fiber reorientation in the weld seam. The scope of this article is to demonstrate the influence of radiation crosslinking on fiber orientation in vibration welds. Mechanical, calorimetric, rheological, scanning electron microscope, and light microscope investigations serve to highlight the influence of radiation crosslinking on the vibration welds of fiber‐reinforced Polyamide 66. POLYM. COMPOS., 38:489–495, 2017. © 2015 Society of Plastics Engineers
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