Why do you use powder on your trip? I have taken liquid detergent with me several times in the past with no trouble at all.
Here is what I do:
Put the proper amount of liquid detergent in a ziploc bag, seal it removing excess air, place all ziplocs of detergent in a plastic container (such as a sports bottle) and put it in the checked luggage.
When it comes time to do laundry, take the bag out of the plastic container and open it up, turn it inside out over the machine so that all detergent falls in, and toss the bag in the machine with the clothing. (don't write on the bag though as the ink may come off) Wash with cold water and remove the bag before tossing in the dryer.
I have never had any trouble with transporting the liquid this way and no damage to any of my clothing.