60/40 cotton/ployester. Washed them in hot water and dried on highest setting a couple times. They haven’t shrunk a bit. An older pair of the same pants shrunk nicely, but that was over the course of years.
Polyester on it’s own shouldn’t shrink, so it’s the cotton content that allowed the other pair of pants to shrink over time. I wouldn’t recommend boiling them. Polyester can melt at high heat - if the pants are labeled for high-heat ironing, go ahead, but I’d guess they probably say to iron on low if necessary.
You may be stuck with just rewashing them over and over again, since you say the other pants took a few years to really shrink. That, or get them tailored.
Urea shrinks polyester, but I suspect that you may not want to wear those pants once they’ve been shrunk that way.
A dry heat around 80-85C will shrink polyester as well. Much higher and it starts lengthening again. Unfortunately, my experiments with this tell me that the shrinkage is not always uniform, depending on the fabric involved.
Not really. It was one of those “Weird Chemistry Fact of the Day” things my Intro Chem professor liked to write on the board before lecture. I have no idea why I remembered it.