Plasma Nanocoatings Developed to Control the Shear Strength of Polymer Composites

Abstract

All reinforcements for polymer-matrix composites must be coated with a suitable material in the form of a thin film to improve compatibility and interfacial adhesion between the reinforcement and the polymer matrix. In this study, plasma nanotechnology was used to synthetize such functional nanocoatings using pure tetravinylsilane (TVS) and its mixtures with oxygen gas (O2) as precursors. The plasma-coated glass fibers (GFs) were unidirectionally embedded in a polyester resin to produce short composite beams that were analyzed by a short-beam-shear test to determine the shear strength characterizing the functionality of the nanocoatings in a GF/polyester composite. The developed plasma nanocoatings allowed controlling the shear strength between 26.2–44.1 MPa depending on deposition conditions, i.e., the radiofrequency (RF) power and the oxygen fraction in the TVS/O2 mixture. This range of shear strength appears to be sufficiently broad to be used in the design of composites.

The Adhesion of Plasma Nanocoatings Controls the Shear Properties of GF/Polyester Composite

“…These nanocoatings were prepared in two thicknesses, verified by mechanical profilometry (Dektak XT, Bruker, Billerica, MA, USA), for the nanoscratch (NS) and nanoindentation (NI) tests described below. The main parameters related to the preparation of the plasma nanocoating are captured in Table 1 ; more details and individual steps of the deposition are described in Reference [ 18 ].…”

“…Figure 3 summarises the short-beam strength as a function of oxygen concentration in the TVS/O2 mixture for the two sets of samples (2 and 30 W). The short-beam strengths for unsized and industrially sized GFs are 13.8 MPa and 39.2 MPa, respectively [18]. For the composite samples prepared from fibres with plasma nanocoating that were deposited from the pure monomer using 2 W, it is clear that the shear strength reaches a similar value as that with the fibres using 30 W a-CSi:H plasma nanocoating, i.e., 32.0 MPa and 31.3 MPa, respectively.…”

“…This leads to an increased adhesion at both the nanocoating–fibre and matrix–nanocoating interfaces and, thus, improves the properties of the resulting composite material [ 14 , 16 , 17 ]. The modification of the fibre surface by a gradient multilayer may be uniquely achieved by a plasma nanocoating prepared using PECVD with an organosilicon precursor, namely tetravinylsilane (TVS) [ 12 , 18 , 19 ]. Using this procedure, we obtained polymer composites reinforced with glass fibres with smooth gradients of mechanical and chemical properties between the composite components, mimicking natural and biological systems.…”

“…In our previous study, we demonstrated the ability to increase the shear strength of a polymer composite by changing the deposition conditions used for the synthesis of plasma nanocoatings [ 18 ].…”

“…Figure 3summarises the short-beam strength as a function of oxygen concentration in the TVS/O 2 mixture for the two sets of samples (2 and 30 W). The short-beam strengths for unsized and industrially sized GFs are 13.8 MPa and 39.2 MPa, respectively[18].Polymers 2021, 13, x FOR PEER REVIEW 7 of 16…”