Tire is a composite material, where man-made organic fibers are employed to reinforce the rubber compound; in the tire industry, the most used organic fibers are Rayon (regenerated cellulose), Polyamide 6/6.6, Polyethylene terephthalate (PET) and Aramid (aromatic polyamide). The adhesion between the organic textile reinforcing materials and the rubber is a crucial aspect to guarantee the tire integrity and durability: from the 1940s to the present, the adhesion was made possible by the Resorcinol Formaldehyde Latex (RFL) dipping [
1,
2,
3]. The RFL is efficient as an adhesive due to the crosslinking of the system with the compound chains [
2]. PET and Aramid are less reactive with the RFL than the other man-made organic fibers; for this reason, a pre-bath is necessary to activate the fiber. The pre-dip introduced by DuPont is the most used in the tire industries; the chemical is prepared by water, miscible epoxy, and blocked isocyanate [
4]. In recent years, researchers have been focused on finding new, alternative methods to promote the adhesion between a textile and rubber, because the presence of the formaldehyde and resorcinol has negative environmental impacts [
5,
6]. Different approaches from different authors were recently explored: one strategy was the preparation of formaldehyde-free adhesive using acrylic resin, another strategy was chemical etching with bromine or the insertion of blocked isocyanate in the compound to promote adhesion [
7,
8,
9]. In this view, plasma technology is an increasingly promising technique. Cold plasma could be created in a reactor by the application of an electric potential difference to a gas [
10,
11]. Thanks to this environmentally friendly technique, it is possible to change the morphology of the surface or to deposit a thin film on different substrates using limited doses of reagents [
12,
13,
14,
15]. If the gas used is an organic compound, the coating can be defined as Plasma Polymer (PPOL). PPOLs are new materials, they differ from a classical polymer by the structural unit, the length of chains and the degree of the crosslinking, which is usually higher [
16]. Plasma treatments were recently used to promote the adhesion between a textile material and a rubber compound. “The General Tire & Rubber Company” patented a plasma activation followed by a grafting with vinyl pyridine before dipping in the RFL, to improve the adhesion of Aramid cord [
11]. The same strategy was explored by Goodyear: plasma activation was followed by the polymerization of CS
2 to develop a network with the compound [
17]. Another plasma approach was explored by Mzabi et al. and based on PE-CVD (Plasma-Enhanced Chemical Vapor) using organic molecules (i.e., maleic acid) to deposit a PPOL [
18]. In this work, the adhesion of PET was promoted by PE-CVD of 2-isopropenil-2-oxazoline (2-iox) mixed with Argon at low pressure. The oxazoline derivates are largely used in medical application because of their biocompatibility [
19]. Oxazoline polymers, obtained by chemical processes, were already used as additives to improve the adhesion of textile materials; the polymers were used as pre-dip before the RFL application [
20]. 2-iox was employed as an organic precursor due to its reactivity. First of all, the oxazoline ring could be fragmentated by the electric potential application during the discharge phase, creating new functional groups. Moreover, the double bond could also react with the radical species that are formed during the discharge. The fragmentation is regulated by the Yasuda Factor, which is defined as the ratio between the Power (W) and the flow. At high values of power, the fragmentation is high, which means that the coating structure is different from the monomer (monomer defect) [
21,
22]. The aim of the work is to find the plasma coating that guarantees the adhesion between a PET monofilament and the rubber compound. Two different regimes were studied to find the best PE-CVD parameters: a continuous regime and a pulsed regime. In the continuous regime, the variable was the power (W), while in the pulsed regime, the discharge is ruled by the duty cycle, which is defined as the alternation of plasma phase on (fragmentation of 2-iox) and plasma phase off (retention of 2-iox) [
21]. The work was divided in two parts; in the first part, the PPOLs were deposited on PET sheets in order to study the surface characteristics and the chemical composition. The wettability was studied, in terms contact angle measurement and thickness, using a profilometer. The chemical composition of the surface was investigated using ATR-IR (Attenuated Total Reflectance Infrared) and XPS (X-ray photoelectron spectroscopy) instruments; the adhesion was studied by Peel Test performed with a tensile machine using the RFL dip adhesion as reference. The characterizations performed on the PET sheets made it possible to optimize the PE-CVD parameters to obtain the coating that guarantees the best adhesion between the fiber reinforcements and the matrix. In the second phase, the optimized PE-CVD of 2-iox was performed on the PET monofilament and the adhesion was studied by the CRA (Cord Rubber Adhesion) test. The degree of coverage was estimated by Optical Microscopy (OM), while TEM (Transmission Electron Microscopy) images were collected to evaluate the thickness and the uniformity of the coating.