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Surface treatment of polydimethylsiloxane (PDMS) with a rotative nozzle atmospheric pressure plasma jet (APPJ) was reported. Operating conditions were optimized by statistical design of experiments, using water contact angle and XPS as response variables; OES (optical emission spectroscopy) was used for plasma diagnosis. The nozzle‐PDMS distance and the torch speed were the most influencing parameters and were optimum at 6.6 mm and 10.3 m s−1, respectively. The extent of hydrophobic recovery of treated PDMS, investigated by water contact angle measurements, was less than what reported in the literature for this amorphous polymer. However, the APPJ treatment proposed in this paper is meant to be inserted in line for a homogeneous surface treatment of PDMS for enhanced adhesion improvement to coatings or adhesives.

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Due to the good strength and similar toughness of epoxy resins, vinyl ester resins are widely used as thermoset adhesives in structural adhesive joints and as composites for different industrial applications. However, vinyl ester adhesives are difficult to cure completely under environmental conditions, even after long periods of time because of gel formation slows the necessary diffusion of the catalyst across the polymer network.Several studies have used weathering chambers to investigate the degradation mechanisms of vinyl ester adhesives. However, a review of the scientific literature revealed both a wide variety of aging processes and several ambiguities between the recorded experimental results.In this work, post-cured vinyl ester resins at different aging cycles were aged under high temperature and relative humidity, and the changes in their structure, mechanical and adhesion properties were studied. Chemical and structural changes were observed in the vinyl ester resins after aging in a climatic chamber.

Recycled polyethylene terephthalate (PET) fiber has been used as reinforcing filler for unsaturated polyester resin (UPR) in order to obtain UPR/PET fiber composites. Different loadings of PET fibers (5-18 phr-parts per hundred parts of resin) of different average lengths (2-3 to 20 mm) were added to the UPR. The mechanical properties of the UPR/PET fiber composites increased up to 8 phr PET fiber loading with a length lower than 5 mm, because of the high affinity between the UPR and the PET fiber surface and the good dispersion of the fiber into the matrix. However, higher PET fiber loading caused a decrease in the mechanical properties of the composites because of the agglomeration of the fibers. The UPR/PET fiber composites presented higher storage moduli than the UPR, and an increase of the glass transition temperature in the composites reinforced with 5-8 phr of short PET fiber was found; further, higher degree of crosslinking was reached. The addition of 5-8 phr PET fiber of short length improved the thermal stability of the composites and the post-curing was produced at higher temperature with much reduced enthalpy.