I'm sure we have all
'killed' a commercially produced acrylic knit at sometime in our lives! We washed it on a too hot wash, or the washer went haywire and spun permanent creases into it?
I've just bought several balls of budget acrylic to knit clothes for my first Grandbaby and am finding it scratchy, coarse and dense. So, I did a bit of Internet trawling and have discovered that heat and moisture knock the life out of man-made fibres - particularly acrylic! Washing garments in with the family wash gives the fibre a good bashing, and using a moderate heat in the dryer, works wonders too.
BUT, even better... if you wash and dry the yarn before
creating a garment, you don't have the misery of wondering if you can bear to finish the project! Just the bliss of working with baby-soft yarn.