D Question 19 1 pts One-D linear chain polymers can be _ or _ O crystalline; amorphous All of these O amorphous; semi-crystalline O crystalline; ceramic O amorphous; thermoset D Question 20 1 pts In the leathery region of the log-modulus vs temperature curve of a polymer, the polymer is usually _ and _. O none of these O rigid; ductile O less stiff; has some ductility with less strength O very stiff; brittle O flexible; brittle