No abstract

No abstract

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.

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.

Please cite this article as: M.I. Butrón-García, J.A. Jofre-Reche, J.M. Martín-Martínez, Use of statistical design of experiments in the optimization of Ar-O 2 low-pressure plasma treatment conditions of polydimethylsiloxane (PDMS) for increasing polarity and adhesion, and inhibiting hydrophobic recovery, Applied Surface Science (2015), http://dx.doi.org/10. 1016/j.apsusc.2015.01.144 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

No abstract

Several waterborne polyurethane urea dispersions (WPUUs) were prepared by mixing different amounts of two waterborne polyurethane urea dispersions made with polyester (WPUU-Polyester) and polycarbonate diol (WPUU-PCD). Their crystallinity, thermal, rheological, viscoelastic and adhesion properties depended on the segmented structure and degree of phase separation which were determined by the different content of the parent dispersions. The PUU films made with WPUU-Polyester+WPUU-PCD mixtures containing more than 50 wt% of WPUU-PCD showed higher hard segments content and lower degree of phase separation, and the addition of 25 wt% of WPUU-Polyester imparted crystallinity to the polyurethane urea due to the interactions between the carbonate groups in the soft segments. The differences in the degree of phase separation and crystallinity of the PUU films made with WPUU-Polyester+WPUU-PCD mixtures were evidenced by the increase in the glass transition temperature associated to the alpha relaxation of the soft segments, and the higher modulus at the cross-over between the storage and loss moduli. Excellent adhesion 2 was obtained in plasticized PVC/WPUU/plasticized PVC joints, and a cohesive failure of PVC was always obtained, irrespective of the composition of WPUU-Polyester+WPUU-PCD mixtures. Furthermore, the adhesion of surface-chlorinated vulcanized styrene-butadiene (SBR) rubber/WPUU+5 wt% hardener/roughened leather joints were high and similar in all joints and a dominant cohesive failure in the rubber substrate was produced. The accelerated ageing by immersion in water at 70 ºC during different times showed that the polyurethane urea film and the surface-chlorinated vulcanized SBR rubber/WPUU+5 wt% hardener/roughened leather joint made with WPUU-PCD dispersion were not affected, but noticeable hydrolytic degradation of the ester units in the soft segments was produced in PUU-Polyester and, to a less extent, in PUU-50Polyester/50PCD films and adhesive joints.

Vinyl ester (VE) resins are widely used as thermoset adhesives in structural joints and composites, but complete curing under environmental conditions is not produced. The existing literature dealing with the effect of post-curing on the structure, viscoelastic, mechanical, and adhesion properties of VE resin is scarce. Therefore, in this study, VE resin was subjected to different post-curing temperatures (50-140°C) for one hour, and the changes in structure and properties were assessed. The degree of cross-linking of the VE resin depended on the post-curing temperature and cure started to be completed above 100°C, a temperature close to the glass transition temperature (115°C) of the completely cross-linked polymer. Furthermore, gel formation in VE resin was evidenced for post-curing temperature below 100°C. In order to fully cross-link the VE resin, post-curing at 140°C for one hour was necessary, and it was evidenced by an increase in the glass transition temperature and in the mechanical properties; an increase in adhesion to cold rolled steel was obtained although the shear strength was lower than in the joint produced with the non-post-cured VE resin.Keywords: vinyl ester resin; post-curing; DMA; DSC; single lap shear strength IntroductionAdhesive bonding is becoming more commonly used in naval industry because of the numerous advantages over other traditional methods of bonding such as welding or riveting. Some of the advantages of the bonding with adhesives include the ability to join different materials with irregular geometries, the decrease in weight, even distribution of stresses, galvanic corrosion resistance, and air tightness. One of the applications of the vinyl ester (VE) resins in naval industry is the manufacture of structural laminates. For example, the hybrid material MaLECoN©[1] is manufactured by bonding steel, glass fiber-VE resin composite and steel by means of VE adhesive.VE resin (Figure 1) is one of the most important thermosetting adhesives that combines the good chemical, mechanical, and thermal properties of epoxy resins with the rapid cure of the unsaturated polyester resins.[2-6] Due to its chemical structure, VE resin exhibits high chemical and hydrolytic resistance, good toughness, high modulus, good thermal and electrical insulation, high impact, and corrosion resistance.