Study of unsaturated polyester and vinylester morphologies using excimer laser surface treatment

Abstract

ABSTRACT:A technique based on the use of an ArF excimer laser (193 nm) to analyze the morphology of the unsaturated polyester and vinylester networks has been developed. This method is based on the use of the differences between the thresholds at which ablation of the various constituent phases of the materials occurs.After having determined the ablation threshold of a polystyrene, various surface treatments using excimer lasers fluence around this threshold were applied to unsaturated polyesters and vinylester. In the latter case, a two-phase structure consisting of microgels in a polystyrene phase was shown by scanning electron microscopy observations, allowing us to conclude that the mechanisms by which vinylester and unsaturated polyester networks are formed are similar. We also observed that the two-phase structure of the vinylester matrixes, unlike that of the unsaturated polyesters, is organized rather than random-structured, which could represent a major parameter contributing to the very good hydrolysis stability of these materials. In the event of degradation by osmotic mechanisms, the organized structure network would enable limiting of the development of the osmotic pressures by distributing the forces within the material, thus avoiding crazing.

New trends in vinyl ester resins

“…It was also observed that with increasing cure temperature, the size of the microgels and clusters became smaller. The two-phase structure of VE matrices, unlike that of UPE resins, was found to be organized rather than random structured, which gives excellent hydrolytic stability to VE resins (Mortaigne et al 1997). Various methods employed to study the curing behavior of VERs are differential scanning calorimetry (DSC) (Chang 1992, Cook et al 1997, infrared (Ganem and Mortaigne 1993, Brill et al 1996, Li et al 1999, Brill and Palmese 2000, gel time studies (Abadie et al 2002), dynamic mechanical thermal analysis (DMTA) (Scott et al 2002a), torsional braid analysis (Stone et al 2000), and thermal scanning rheometry (Martin et al 2000).…”

Toward reliable morphology assessment of thermosets via physical etching: Vinyl ester resin as an example

“…As expected based on the work of Mortaigne [6] there should be a lower ablation threshold that should be surpassed during etching. Figure 1 shows a series of AFM height, amplitude and phase contrast images taken from the VE etched by different LA parameters.…”

“…Detectability of the morphology was prominently improved by physical etching. VE samples were etched by laser treatment [6] and argon ion (Ar + ) bombardment [7]. On the other hand, the nodules' size in the published works often differed from one another markedly.…”

“…Information on the topology was received by a chromatically encoded confocal measurement (CHRocodile E, Precitec Optronic GmbH, Ridgau, Germany) with an axial resolution of 35 nm, (measuring rate 4 kHz, lateral measuring distance (x = (y = 2.5 µm, feed rate 1 mm/min) yielding an arithmetic surface roughness (R a ) in the range of 260-480 nm. It is noteworthy that in the pioneering work of Mortaigne [6] on the laser ablation of VE using a pulsed ArF excimer laser (! = 193 nm, PRF 10 Hz, number of pulses 200, pulse duration = 16 ns) an ablation threshold of about 25 mJ/cm 2 laser fluence was determined.…”

Radiation and postirradiation crosslinking and structure of two unsaturated polyester resins

“…This is one of the reasons why full conversion is impossible in isothermal conditions [11]. Although it is most often used, unpolar styrene is not a thermodynamically good solvent for relatively polar polyester [10,12,13], and so various saturated diacids or higher dialcohols are added in the preparation of polyesters to improve compatibility. Orthophthalic and isophthalic acids are the most often used diacids, because it is expected that their aromatic rings will increase compatibility with styrene, and the reactivity of the resin can be modified in that manner too, because polyester becomes less flexible and less reactive [14].…”