Influence of the polypropylene structure on the replication of nanostructures by injection molding

Abstract

In this paper, an experimental study of replication by injection molding of sub-micrometer features is presented. Two polypropylenes with different melt flow rates (MFR) were used throughout this study. The used removable mold insert was textured with a femtosecond laser. Replication of these periodic structures, called ripples, is thus investigated. Despite different MFR, we show that the viscosities of the two polymers at the investigated temperatures and injection shear rates are similar. The reproducibility of the injected molded samples and the texture of the mold were analyzed. We propose a specific methodology to quantify the reproducibility quality replicas. The latter introduces morphological parameters such as anisotropy rate, power density, etc. A difference between the two replicas was noticeable. Based on rheological analysis, the viscosity was ruled out as the origin of this difference. Other properties were identified as the source such as the chain length and the stress relaxation time. Their impact on the replication quality was investigated and found interesting.

Design of an environment controlled dew tracking setup to emphasize the role of the relative humidity on breath figures dynamics

“…The polycarbonate samples were replicated from a mirror polish with a low roughness injection mold [21].…”

Synthèse bibliographique : micro-texturation et microinjection de thermoplastiques

“…5) [37]. Cette indice traduit une viscosité sous faible vitesse de cisaillement (quelques s À1 ) alors que les injections se réalisent parfois à des valeurs supérieures à 10 5 s À1 , il est donc particulièrement important de connaître ce comportement dans les conditions réelles d'injection, ce d'autant plus que certains polymères de MFI très différents peuvent avoir une viscosité relativement proche pour des vitesses de cisaillement élevées [38]. Ainsi, les études rhéologiques en lien avec la taille des structures à remplir se multiplient pour répondre aux problématiques de remplissage de microcavités [39,40].…”

“…Ces comparaisons sont satisfaisantes quand il s'agit de motifs très bien définis et périodiques comme ceux obtenus par LIGA, en revanche quand cela fait référence à des textures moins régulières et multi-échelles, cette approche locale ne convient plus. Il est indispensable de mettre en oeuvre des outils statistiques susceptibles de décrire la topographie de surface au regard des caractéristiques de la forme souhaitée (paramètres d'anisotropie [38]), de la fonction envisagée [4] et de pouvoir faire des comparaisons quantitatives entre le moule et la pièce aux différentes échelles tels que présentés sur la figure 14, par exemple.…”

A multiphase Eulerian approach for modelling the polymer injection into a textured mould

“…The polypropylene described in Table 2 is injected in the cavity illustrated in Figures 3. This part has been experimentally used for characterizing micro-features replication [16,31]: the rectangular plaque is 50mm long and 15mm wide; its thickness is 1mm. The piece exhibits micro features in the central square zone of 8mm.…”

“…Computations were performed with polypropylene (PP) which is one of the most common thermoplastic polymers used in a variety of products and is easily and widely transformed by the injection moulding. Moreover, it has been recently used to obtain replication of submicrometer features by injection (microinjection) molding [36,31]. For example polypropylene is used for biomedical devices which have a short time contact with drugs (disposable syringes and catheters) where the aim is to have a plastic hydrophobic surface to improve the displacement of the plunger inside the syringe.…”