In all due respect to your “expert” - Vinylester resin cannot and is not used as an adhesive - like epoxy can ! Vinylester is simply a resin that is and can only be used for laminating. It will not bond (glue) dissimilar materials together, it doesn’t work well as a bedding for mounting deck hardware, and if I recall correctly, it has less tensile strength and flexibility than epoxy.
Sorry - if I am going to spend nearly $50 (USD) for a quart of something, it better work for a lot of applications - not just for glass composite layups.
VINYLESTER: The vinylester molecule also features fewer ester groups. These ester groups are susceptible to water degradation by hydrolysis which means that vinylesters exhibit better resistance to water and many other chemicals than their polyester counterparts, and are frequently found in applications such as pipelines and chemical storage tanks.
So in this case, I would agree that vinylester is much better than “Polyester” - however - it is still an “ester” based resin. Also - if you look at the molecular makeup of vinylester resin, you will find it is no way an “epoxy” type of resin. See second paragraph below under “polyester”.
EPOXY: High adhesive strength and high mechanical properties are also enhanced by high electrical insulation and good chemical resistance. Epoxies find uses as adhesives, caulking compounds, casting compounds, sealants, varnishes and paints, as well as laminating resins for a variety of industrial applications.
POLYESTER: There are two principle types of polyester resin used as standard laminating systems in the composites industry. Orthophthalic polyester resin is the standard economic resin used by many people. Isophthalic polyester resin is now becoming the preferred material in industries such as marine where its superior water resistance is desirable.
Also, the “ester” groups cure via “catalyst” additives, whereas epoxies cure from adding a hardener.
OSMOSIS: All laminates in a marine environment will permit very low quantities of water to pass through them in vapour form. As this water passes through, it reacts with any hydrolysable components inside the laminate to form tiny cells of concentrated solution. Under the osmotic cycle, more water is then drawn through the semi-permeable membrane of the laminate to attempt to dilute this solution. This water increases the fluid pressure in the cell to as much as 700 psi. Eventually the pressure distorts or bursts the laminate or gelcoat, and can lead to a characteristic ‘chicken-pox’ surface. Hydrolysable components in a laminate can include dirt and debris that have become trapped during fabrication, but can also include the ester linkages in a cured polyester, and to a lesser extent, vinylester.
Use of resin rich layers next to the gel coat are essential with polyester resins to minimise this type of degradation, but often the only cure once the process has started is the replacement of the affected material. To prevent the onset of osmosis from the start, it is necessary to use a resin which has both a low water transmission rate and a high resistance to attack by water. When used with reinforcements with similarly resistant surface treatment and laminated to a very high standard, blistering can then be virtually eliminated. <u>A polymer chain having an <font color=“blue”>epoxy</font id=“blue”> backbone is substantially better than many other resin systems at resisting the effects of water.</u> Such systems have been shown to confer excellent chemical and water resistance, low water transmission rate and very good mechanical properties to the polymer.
<font size=“1”>Published courtesy of David Cripps, SP Systems</font id=“size1”>
Just want to keep focused on facts - [:-graduate] [;)]
Dick Lemke
F-48 #US-06
MultiONE #US-06
Class 3 Landyacht #US-196
Minnesota, USA