Water is a highly polar substance that acts like a small magnet with a negatively charged. Polycarbonate, nylon, PBT, PET, ABS, acrylic, urethanes, and many other hygroscopic resins are long-chain polymers. Hygroscopic resins contain carbon and hydrogen but, also have a “polar” segment of atoms that behave like a small magnet with north and south poles. If moisture, also a polar substance, is present, you get two mini-magnets that attract each other.t is this “magnetic attraction” that pulls the moisture out of the air and holds it to the polymer. To get rid of it you have to dry these polymers at sufficient temperature to drive the two attracting magnets far enough apart that the magnetic attraction is minimized, and the circulating air from the dryer can extract the moisture.