Mechanical Properties of Plasma‐Polymerized Tetravinylsilane Films

Abstract

Continuous stiffness measurement (CSM) and dynamic contact module (DCM) nanoindentation measurements were used to characterize the mechanical properties of plasma‐polymerized tetravinylsilane films deposited by PECVD at RF powers ranging from 10 to 70 W. The Young's modulus and hardness as a function of the indenter displacement (5–500 nm) were investigated for films of 1‐µm thickness. The Young's modulus (hardness) was observed to increase from 8.3 (0.9 GPa) to 58 GPa (9.5 GPa) with enhanced RF power. Nanoindentation analysis together with AFM imaging revealed a grain character of films deposited at a higher power. Finite element analysis was used to simulate nanoindentation measurements and evaluate properties of the elastic–plastic material.

Nitrogen‐Rich Plasma Polymer Coatings for Biomedical Applications: Stability, Mechanical Properties and Adhesion Under Dry and Wet Conditions

“…Nano‐indentations on each sample under successively increasing load (Figure a) enabled us to measure the sampless’ reduced modulus E r and hardness H at various indentation depths, and to determine their values before reaching the critical depth, the one at which the substrate begins to appreciably influence the measured value. According to the literature, this critical depth is about 10% of total thickness . Accordingly, the present work yielded near‐constant H values for low indentation depths, followed by apparent increases due to the rigid glass substrate (Figure b and c).…”

“…The sample's reduced modulus, E r , is determined from the slope of the unloading curve at the very beginning of load reduction, using the following equation: where S , defined as the unloading stiffness, is (d L /d h ) at that point on the plot. Since L‐PPE:N films are soft, while the indenter is very hard, 1141 GPa, E r can be assimilated to Young's modulus, but only if the substrate's presence can be neglected. Even if 10% of coating thickness has been reported by some authors to be the maximum “safe” indentation depth required so as not to sense the substrate, it is not possible to generalize this since it depends on the coating's mechanical properties and the mechanical mismatch between it and the substrate .…”

“…Since L‐PPE:N films are soft, while the indenter is very hard, 1141 GPa, E r can be assimilated to Young's modulus, but only if the substrate's presence can be neglected. Even if 10% of coating thickness has been reported by some authors to be the maximum “safe” indentation depth required so as not to sense the substrate, it is not possible to generalize this since it depends on the coating's mechanical properties and the mechanical mismatch between it and the substrate . Therefore, to assess a possible substrate effect, E r was calculated for each value of L and reported as a function of h , in order to determine the critical depth at which E and H start to rise with increasing depth of indentation .…”

“…Even if 10% of coating thickness has been reported by some authors to be the maximum “safe” indentation depth required so as not to sense the substrate, it is not possible to generalize this since it depends on the coating's mechanical properties and the mechanical mismatch between it and the substrate . Therefore, to assess a possible substrate effect, E r was calculated for each value of L and reported as a function of h , in order to determine the critical depth at which E and H start to rise with increasing depth of indentation . Constant values below this critical depth suggest that the effect of the substrate is minimal under these particular conditions.…”

Elastic Modulus and Hardness of Plasma‐Polymerized Organosilicones Evaluated by Nanoindentation Techniques

“…A Nano Indenter XP (MTS Systems Co.) was used to carry out the indentation measurements with the CSM and DCM techniques. The dynamic contact module (DCM) is a low‐load accessory attached to the same platform used for the Nano Indenter XP.…”