The biggest limitation of using glass over Teflon plastic sheet was that glass is extremely heavy to lift and is much more prone to getting broken when fallen down. In the past, substances like rubber, glass or clay were used in households because we only knew how to mold them and give a required shape. But the rubber utensils were not the ideal place to keep things especially the eatables. Rubber is a very smelly substance, has myriad of harmful chemicals, and it even loses its shape when heated.
The stretching property of rubber was discovered in the year 1839, when Charles Goodyear an American inventor was accidentally able to devise a process in which the sulfur undergoes a chemical reaction with the crude rubber on heating up and cooling down. During this process, the rubber develops the elasticity and the ability to stretch and coming back to its original shape. This way, we became familiar with the quality of rubber that the sulfur in it makes a chemical bond in the neighboring rubber polymer threads. These connections intersect the polymer thread, thereafter, making them stretched out and back to any desired shape. This way, Goodyear founded the process called vulcanization with which we were able to create a stretchable quality in the rubber, a process which was later used in making plastic as well.
In a similar way, in the year 1846, Schonbein from Switzerland discovered a polymer when he accidentally spilled the mixture of the nitric and sulfuric acid on the regular cotton. This reaction resulted in the formation of the hydroxyls of cellulose on cotton, which were transformed into the nitrate groups on reacting with sulfur. This resulted in the creation of the polymer called the nitrocellulose. Nitrocellulose was highly flammable, a property that led to its use in the military replacing the famous gunpowder. Then in 1870, another scientist named John Hyatt created a chemical reaction of nitrocellulose with camphor to develop celluloid, a polymer of plastic. Later on, the first ever synthetic polymer called the Bakelite was discovered in the year 1909, which has the amazing property of molding into any desired shape on heating. This quality led to the use of Bakelite in creating different types of household equipments, phones, furniture, etc. With Bakelite, started the creation of a new range of Phenolic sheet plastic polymers with unique properties. Then in 1930, the first plastic polymer known as the nylon was invented with amazing properties of strength, durability. It was also as light as an air, which made is appropriate for creating durable bags, clothes, etc.
The first ever man-made plastic discovered was known as the 'parkesine' after the name of Alexender Parkes who introduced to the world a new material in the annual international exhibition in the city of London in 1862. The material so discovered had the properties of an organic compound extracted from the cellulose. This new material could be given any shape on heating, and once bent it hardens and kept that shape on cooling.
When the plastic was not invented, there was only one thing that we were able to bend in order to give them any shape we wanted, it was the glass. Due to this quality, the utensils made from glass were used to store all types of stuffs. So let's see how the Polycarbonate sheet of plastic we use today came into being.