Here's the pattern that addresses every mistake at once:

• Turn your tee inside out before washing. This protects the outer surface, including the collar, from direct abrasion.
• Zip up any hoodies or jackets before washing. Those zippers are like sandpaper for collars.
• Wash with like fabrics only. Keep your tri-blends with other soft tees, not with jeans or towels.
• Air dry. Hang it on a hanger or lay it flat. It takes a few extra hours, but your collar will stay smooth.

This isn't a list of separate tips—it's one approach: reduce friction at every point of contact. Once you start thinking in terms of "what rubs against the collar," the solution becomes obvious.