Is it legal to borrow CDs from the library and burn them for personal use?

Unless you are using it for purely educational reasons (which seems unlikely), no.
Do you really not know? Seems pretty obvious to me that it's stealing.
no it is also not legal to borrow them from your friends and do it. It is called pirating, but you are not the first and won't be the last
Totally wrong...
Not legal not any way you look at it.

If the library has a CD, they paid for it. Now, if they lend it to you, you have the CD. Only one person has the CD at any time, and there only one copy of the CD (which has been paid for).

If you copy that CD, even for your own personal use, and return the original to the library, now there are TWO copies of the CD, only ONE of which was paid for.

You can't get a book from the library and copy the entire thing for your personal use either. Of course, no one is asking about that, it takes too much time and effort to copy a whole book. But just because it is easier to burn a CD than copy a book doesn't make it legal to do.
It is illegal but that doesn't stop anyone from doing it.
things are only illegal if you get caught..., by definition of law..., odd huh...
It is illegal. You are allowed to copy a cd you already own and paid for, but only for your own use. For example, say you want to keep the original in the case and keep the copy in the car where it will get all scratched up. If you got caught with burned cd's and you could produce the originals that you already own, then they can't charge you because you paid for that music.

So technically, you could burn a copy for anyone in your household to use, too.

It is funny, but I guess when I was growing up in the Eighties and I taped songs off the radio... I was breaking the law.

No. Burning CD's is not legal unless you have written permission from the label. The exception is if you are creating a compilation CD for your personal use from CD's that you already own. The same is true of movies and books. These are all forms of intellectual property

When you illegaly copy intellectual property you are breaking copyright laws by stealing from the creators of those works. Depending on the level of the offense you could theoretically be sued, fined or sent to prison for violating copyright laws.
No. You can purcase a CD and make archive copies for personal use. Anythings else woudl require writtne permission from the people who hold the rights to the songs.
No. Since you have not purchased the CDs, you are only allowed to listen to it when in your possession.