Altering nature's polymers In the early 1900s scientists began to understand the chemical makeup of natural polymers and how to make synthetic polymers with properties that complement those of natural materials. They began altering a number of natural polymers chemically. Cellulose, for example, was treated with nitric acid to make celluloid, an early plastic material. Its flammability was major drawback, though; movie theaters often caught fire in the old days, as hot projector bulbs set celluloid film aflame. Cellulose from wood was also converted into materials like rayon and cellophane.