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Enhanced replication ratio of injection molded plastic parts by using an innovative combination of laser-structuring and PVD coating

 
: Bobzin, K.; Hopmann, C.H.; Gillner, A.; Brögelmann, T.; Kruppe, N.C.; Orth, M.; Steger, M.; Naderi, M.

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Surface and coatings technology 332 (2017), S.474-483
ISSN: 0257-8972
Englisch
Zeitschriftenaufsatz
Fraunhofer ILT ()

Abstract
The properties of plastic products can be optimized by a suitable design of the component surface. One promising method for plastics processing by injection molding is the use of molding tools structured in the micro-meter range. Within the scope of this paper, laser micro-structuring was carried out on two injection molds. A chromium-based nitride coating was deposited on one of the micro-structured mold by means of middle frequency magnetron sputtering (mfMS). Commercial plastics polycarbonate (PC2245) and polymethyl methacrylate (PMMA 7 N) were considered for all investigations. The coating contained xCr = 51 at.−% chromium, xAl = 30 at.−% aluminum and xN = 19 at.−% nitrogen exhibited a fine and dense columnar structure. It was experimentally seen that the coefficient of friction measured using a pin on disc tribometer reduces about 11% in case of PMMA 7 N, and about 17% for PC2245, using PVD. By comparing coated and uncoated surfaces, a lower wettability in contact with the plastics melt of PC2245 and PMMA 7 N analyzed by means of high temperature contact angle (CA) measurements was achieved for coated surfaces. This corresponds to the low amount of shear energy required for the separation of the solidified PC2245 and PMMA from the samples surfaces after the CA measurements. The influence of the temperature on coating property, roughness, after the CA measurements was observed as well. It was shown that the replication ratio of optical micro-structures can be increased significantly up to 20–30% by using a PVD coated in comparison to an uncoated mold.

: http://publica.fraunhofer.de/dokumente/N-477302.html