Insight into the Release Agents/PVD Coatings Interaction for Plastic Mold Technology

Abstract

In polymer processing, the formation of undesired fouling hinders the plastic manufacturing processes. Hence, the use of emulsions as releasing agents is mandatory and their affinity to the mold substrates plays a crucial role. Therefore, this research work has been focused on the wetting properties of commercial water-based release agents (namely Marbocote ® W2140, EP, EV-333) towards different Physical Vapor Deposition (PVD) nitride coatings (AlTiN, NbN, ZrN and TiN), usually adopted in the industrial manufacture of Hydrogenated Nitrile Butadiene Rubber (HNBR). The investigated solid substrates were characterized by means of profilometry, SEM/EDX and Surface Free Energy (SFE) analyses, whereas, tensiometric determinations were acquired on the commercial pure and diluted emulsions. The release agents/mold substrates wettability features were studied by means of the work of adhesion and the spreading coefficient. Finally, nitride-coated mold seals were directly tested in an industrial plant with the most performing release agent in terms of adhesive features; for the first time, a deep correlation between the service life, in terms of number of molded seals, and surface (contact angles, work of adhesion and spreading coefficient)/electrochemical (OCP) features was drawn. IntroductionPolymer processing technology, including injection and compression molding [1-3], entails a prolonged polymer/metal tool contact. Hence their adhesion [4][5][6], depending on the process conditions, the solid tool surface features (type, roughness and surface free energy) and the polymer chemistry, plays a pivotal role in affecting the quality of the final plastic product.However, when the affinity between the polymers and the mold substrates is relatively low, the formation of mold fouling [7] occurs, causing the interruption of the plastic manufacturing process. Specifically, mold fouling is a layer of material, which forms on the surface of metal molds during the rubber vulcanization. Indeed, it is the result of thermochemical changes in components of rubber compounds during high temperature molding condition, impeding the heat transfer from the mold to the polymer. Thus, in order to obtain defect-free rubber articles, mold fouling must be removed from the metal surface tools by means of regular cleanings, therefore representing an onerous step for the industry (i.e. the production line shutdown, the use of expensive chemical products).Hence, two approaches can be followed to limit the mold fouling phenomena. The first one consists in the modification of the rubber formulation, for example by choosing the right plasticizing agents, such as extender oils [8,9]. The second approach involves the use of release agents [10,11] (typically emulsion-based compounds [12,13]), which are applied to the mold surfaces to ensure the total removal of the undesired products from the surfaces themselves. Regarding the former, the plasticizer is fundamental for the vulcanizing process, because this component allows the phase transitions. However, ba...

Influence of Silver Nanoparticles on Mechanical Characteristics of Arboblend V2 Nature Lignin-Based Polymer

“…The higher pressure helped to better compact the biopolymer in the injection mold and the longer cooling time allowed for closer intermolecular bonds. The structural homogeneity of the samples and the experimental reproducibility is highlighted by the low values of standard deviation obtained for each experiment aspect visible in Figures (4)(5)(6). According to the literature, [8], the maximum arrow in case of the Arboblend V2 nature is 5.44 mm.…”

“…The most common PVD processes are sputtering and evaporation. PVD can be adapted to requests, and the layers can be improved for various features, like decorative, optical, electrical, and mechanical properties, [4][5][6]. The manuscript aims to evaluate the obtained mechanical characteristics of a biodegradable material -Arboblend V2 Nature (granules -substrate) and silver nanoparticles -AgNPs (coating material) through Physical Vapor Deposition (PVD) process.…”

Electrochemical evaluation of mucilage and cochineal pigments as a hybrid film coating on aluminum surfaces

“…The CMC and CMC-T systems present higher values of resistance and efficiency of the organic coating as a function of the inversion time than the studied CM system and the reference without coating. It is pointed out that the R s values of different coatings under study are minor compared to a without covering system due to the microstructure in systems with mucilage is denser and presents holes that provide a diffusion path of the electrolyte to the recovering/substrate interface [40][41][42].…”

“…Figure 7(a) shows the infrared spectrum (FT-IR) of the mucilage extracted from the nopal (CM). The band at 3255 cm −1 is attributable to carbohydrate O-H bonds of the hydroxyl groups [41]. The C-H stretching vibrations at 2930 cm −1 , and small bands at 2882 and 2850 cm −1 are due to C-H and -CH 2 stretching of the pyranose and the carboxylic groups, respectively [41].…”

“…The band at 3255 cm −1 is attributable to carbohydrate O-H bonds of the hydroxyl groups [41]. The C-H stretching vibrations at 2930 cm −1 , and small bands at 2882 and 2850 cm −1 are due to C-H and -CH 2 stretching of the pyranose and the carboxylic groups, respectively [41]. The C-C stretching bonds are visible at 2100 cm −1 .…”