- Plastic bottle
- Preparing to experiment with pressure in the bottle
- Water and air use
- Wheel chamber, ball and plastic bottle
- Conduct an experiment with plastic bottles
Most people believe that plastic bottles are fragile enough, and some even fear that they might explode when they contain sparkling water. The answer to the question of how much pressure a plastic bottle can withstand is contained in the article, will make many wonder.
Currently, plastic and plastics are the most common material, which is widely used in various fields of human activity. One of these areas is the manufacture of plastic bottles for beverages. The industry of plastic bottles began to actively develop since the 50s of the last century. The main advantages of plastic bottles in comparison with glass bottles are the simplicity of their manufacture, the possibility of giving plastic a variety of shapes, low cost of production and ease of transportation.
Bottles for carbonated beverages are made from polyethylene terephthalate (PET). However, it should immediately be noted that a container of different volume has some variations in its chemical composition, as well as in the thickness of its plastic walls. The use of PET in the production of bottles for beverages is associated with its chemical resistance to alcohol and natural oils, as well as its physical strength under the influence of mechanical loads, including pressure. You should also be aware that PET is destroyed by acetone and loses its properties at temperatures above 70.
Preparing to experiment with pressure in the bottle
As is known from the course of physics, pressure is a force that acts on the surface of a given area. They express pressure in the SI system in Pascals (Pa), but often other units of measurement are used in practice, for example, millimeters of mercury or bars. So, 1 bar = 100 000 Pa, that is, a pressure of 1 bar is approximately equal to a pressure of 1 atmosphere (1 atm. = 101 325 Pa).
To perform experiments to determine what pressure a plastic bottle withstands 1.5 liters and other volumes, it is necessary to have some devices. In particular, an electric pump is needed, a pump with which tires of cars are pumped will be suitable. You also need a pressure gauge - a device that measures pressure. We also need tubes through which the pump will pump air into a plastic bottle.
Preparing for the experiment also includes installing the bottle in the right way: it is laid on its side, and the hole is drilled through the center of the cap (cork). The corresponding tube is placed in this hole. To fix the tube, you can use different viscous substances, including glue. Once the pump, pressure gauge and bottle are assembled into a single design, you can begin to conduct an experiment.
Water and air use
Both water and air are fluid substances and create pressure in all directions equally, so they can be used for experiments to study the resistance of a plastic bottle to pressure inside it. However, it is necessary to know some features of the use of water and air.
The issue of using water or air rests on two main problems: the complexity of the technique of execution and safety. So, in order to conduct experiments with water, more complicated equipment is needed (durable hoses, a regulator of water supply to the bottle), for experiments with air it is enough to have only a pump. On the other hand, air experiments are less safe than water experiments. The reason for all is the fact that when a bottle explodes, the air escapes from it with tremendous force and can carry away plastic fragments, which, in turn, can harm nearby people. With water, this does not happen, it does not splash in all directions when the PET bottle is destroyed.
Therefore, most often when testing plastic bottles with pressure, air is used, but the bottle is pre-filled with 60-80% water.
Wheel chamber, ball and plastic bottle
Considering the question of how much pressure a plastic bottle can withstand, one should first of all refer to the results of comparative experiments. One of the most popular comparative pressure experiments is the use of a car's camera, a ball and a plastic bottle.
If these objects are pumped up with air, it turns out that the auto camera will burst first, then the ball, and only the last bottle of PET will collapse. Why this happens is not difficult to explain. The car camera and ball are made of rubber, and although it has a different composition, but the base is the same. That is why the ball and the camera withstand approximately the same pressure, only the thickness of the rubber in the ball is greater than in the auto chamber.
The material from which the bottle is made is not as elastic as rubber, but not as fragile as many solids, such as glass. These physical properties give it the necessary margin of safety and resistance when exposed to high pressures.
Conduct an experiment with plastic bottles
After preparing for the experiment and before starting it, it is necessary to take appropriate security measures. They consist in the fact that you need to move a certain distance from the place of the experiment, and you should take care that there is access to the readings of the manometer in order to fix the values at the moment of the explosion of the bottle.
During the experiment one can see that up to 4/5 of the maximum pressure that the bottle can withstand, it is practically not deformed. Significant deformations of PET are observed only in the last 10% for the pressure before the explosion.
As a result of analyzing a series of experiments with PET bottles of different sizes and from different companies, it was found that all the results obtained ranged from 7 to 14 atmospheres. At the same time, it is impossible to unequivocally answer the question of how much a plastic bottle withstands a pressure of 2 liters or 1.5 liters, because of the above reasons, that is, some bottles in 2 liters turned out to be much stronger than 1.5 liters. If we talk about the average value, we can say that plastic bottles with a volume of up to 2 liters can withstand 10 atmospheres. For example, we recall that the working pressure in the tires of a car is 2 atmospheres, and the tires of trucks pump up to 7 atmospheres.
If we talk about PET bottles of larger volume, for example, 5 liters, then we can say that they can withstand much less pressure than 1.5 and 2 liters containers. How much pressure does a 5 liter plastic bottle hold? About 3-5 atmospheres. Smaller values are associated with larger tare diameter.