My friend was going over budget that is why he was not able to buy cork and he place the screw cap on the bottle but, as far as I know screw caps are not worth using and even spoils the real taste and aroma of a wine like what synthetic caps do.
I will suggest him to get through this post so that he will find out some better ways of bottling the wine.
OK, I am getting up on my soap box now....
For the commercial wine industry, of all the synthetic closures on the market today, Screw caps are currently considered the preferred way to go when not going cork.
For amateurs, there are really only two alternatives (to cork) available, Synthetic plastic corks or screw caps.
Plastic corks have been found to allow micro oxidation, but in excessive amounts. A large portion of wines were found to be horribly oxidized after only three to five years of age.
Screw caps provide the complete air tight seal. It is important to realize that the screw cap does nothing to actually spoil the wine, but traps elements of the wine that would normally react with micro-oxidation of natural cork. You should think of screw caps as a seal and not a closure.
Screw caps never took hold in the USA simply because they were used on the cheaper, domestic wines early on in the US wine industry. At the time, all of the expensive wines (considered as high quality coming from Europe) always had a cork closure.
So a stigma developed in the US that screw caps equate to cheap, low quality wines. This actually had nothing to do with the effectiveness of the screw cap as a closure.
ENTER TCA.
For years, commercial wineries could expect that a small percentage of their wines (3 or 4 percent) would end up being "corked". Until rather recently, not much was known about "cork taint" (or the TCA Compound), so the international wine industry started looking for an alternative to cork to protect wine from this scourge.
To put it simply, screw caps are coming back. The use of screw caps has been steadily growing in England and (to a minor degree) in France and other parts of Europe.
The largest user of screw caps (from a % of wine using the product) is Australia. It seems that the Australian wine industry, one of the youngest, has never had the same stigma that the USA had developed concerning screw caps and some rather high end wines are currently available in screw cap.
To make up for the lack of micro oxidation, most wineries take steps to "pre-age" the wine. This mostly means that the wine is aerated before being sealed in the bottle. Additional chemical treatments are also employed such as the use of copper sulfate prior to seal.
OK, now to wrap this up - Cork is considered the best simply because of micro oxidation. Unless you are willing to perform some sort of "pre-aging" steps, I would not advise using screw caps if you intend to age you wine past several months.
Ok, I think I have successfully pounded this into the ground. I am getting off my soapbox, gonna sit down, and then shut up! (please, no applause)