Is it possible using composite material with polyester matrix in wet places?
Thanks in advance
Hello dear. You can do it, but the ideal case is that the polyester be hydrophobic, because it has more resistance against to wet.
Sure. You can use PLA resins in wet places because the polyester hydrolysis is very very slow at room temperatures. So, you should be careful to not use PLA at higher temperatures. The Tg of PLA is about 60°C; when PLA is exposed at temperatures higher than Tg, the hydrolysis reactions become more and more rapid.
I do not know what type of polyester you are interested in, but in general polyester does degrade in the presence of humidity, temperature, and stress. You may be interested in more recent polylactic acid derived polyester, or more traditional unsaturated polyester resins. If the latter, there are various grades of polyester, depending on what type of acid you use, that influence the hydrolytic stability. Tg is in the range 70-100oC. Below this temperature, the stability is good. But, the degradation is general aid / general base catalysis. So, as long as you have humidity and environment other than neutral, it does degrade. Degradation in the base environment is more severe. The way cross linker, styrene unit, copolymerizes with the unsaturated polyester resin, influences the stability significantly. Also the type of aid used, such as isophthali acid, orthophthlic acid, and bisphenol A in this order the stability improves. The latter is typically used for the chemically resistant applications such as pipes in the chemical plants. To further improve the properties, intermediate material between unsaturated polyester and epoxy has been developed. It is called vinyl ester. Finally, polyester degrades faster under tension, in particular in the presence of humidity, whereas under compression, it survives longer, based on Eyring;s equation of mechanochemistry
You can have a look in:
M. Deroiné et al. Polym. Degrad. Stab. 2014, 108, 319-329
Regards,
Stéphane
The adhesive bonds in almost any polymer matrix will hydrolyze in presence of excessive water molecules. Vinyl esters are relatively less susceptible to hydrolysis as mentioned by Hatsuo. There are certain kind of polyester resins that are either blended or crosslinked with silicones. So, to answer your question, you may extend the stability of polyester resin by coupling it with silicones. Due to low surface energy, silicones migrate to the surface that preserves the underlying surface from percolating water molecule.
Yes, but it depends on the polyester used, as indicated above. Most watercraft (boats, yachts, kayaks, etc) are made using glass fibre reinforced polyester resin (free radical crosslinked unsaturated polyesters) in their hulls that are in constant contact with water (fresh and/or sea).
Dear Nawras,
polyesters are a material group with large variations in molecular structures. All the answers you might get will be different without specifying the polyester type.
Thermoplastic polyesters like PBT in most cases are sensitive against hydrolysis. Especially at high temperatures the material is damaged. But the molecular structure can be modified to reduce the sensitivity in an effective way. Such types you will find p.e. in the product portfolio of BASF (ULTRADUR B4330 G6 HR).
With best regards
Michael
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