Car glass recycling
According to the data of the European Commission, it is estimated that between 8 and 9 million vehicles are “discarded” every year… in Europe only. Consider now that this is one of the seven continents on our planet where the world’s most developed countries, such as the USA and China, do not lie, where there are certainly many more such vehicles.
There are currently around 1.2 billion vehicles in the world. Their number will continue to grow, and it is estimated that by 2040 there will be more than 2 billion of them. Along with the increase in owned cars, the number of discarded cars is also growing, and as a result – the amount of materials that needs to be recycled is increasing.
The structure of car glass
The metal parts of a car are used at the scrap yard and usually they are not problematic. However, plastic and glass elements must be sent to companies that specialise in the recycling of a given material.
Car glass forms a special group among various glass categories. It is so-called laminated glass, which contains a protective layer, usually PVB film (polyvinyl butyral), placed between two glass panels. The process of binding the layers is usually taking place at high temperature and pressure. After laminating under these conditions, the inner PVB layer becomes transparent and joins two glass panes. This process closes the “glass sandwich” and looks like ordinary glass.
Laminated glass accounts for approx. 3% of the total material in standard passenger cars, and each windshield contains about 1 kg of PVB film alone. After analysing the composition of the laminated car glass, it turns out that it consists of 25% PVB and 75% glass. Worldwide, 65% of PVB film utilised is used for the production of car windows, which has been the cause of rapid development of the PVB market over the past few years.
Given the above statistics, we can imagine the amounts of glass material we must deal with in the process of disposal of motor vehicles.
PVB film – protective properties
Car glass owes its protective properties to the interlayer of artificial material it contains:
- the interlayer dissipates the impact force on a larger surface of the pane, thereby increasing the impact resistance of the glass;
- the glass breaks under the influence of a strong impact, however, the resulting fragments adhere to the middle layer (PVB), which protects the driver and passengers of vehicles against injuries;
- during the impact, the viscoelastic interlayer undergoes plastic deformation and absorbs the energy transmitted by the striking object.
The costly process of car glass disposal
If the PVB film has so many beneficial mechanical protective properties, why is it so much of a problem for recyclers? Well, the disposal and processing of packaging glass is one thing, while the processing of laminated glass is another thing. PVB film is the nightmare of car glass recyclers. The process of laminated glass recycling is a bit more complicated and consists of the following stages:
- Outdoor storage of glass aiming to reduce adhesion between the film and the glass.
- Glass crushing.
- Separation of the glass from the film.
At this stage, recovered glass is sent to a glass recycling plant, while the recycler stays with the waste PVB film powder, whose reuse is problematic. It is reluctantly re-used for the production of laminated glass as it has not been completely cleaned of glass dust. Theoretically, it could be used as an alternative fuel, but despite its high calorific value, the PVB film has relatively low combustibility and contains a relatively large amount of glass particles. If, however, there are “buyers” willing to use the film as an alternative fuel, they are not inclined to offer a high price for the material. In order to dispose of the problematic waste, the recycler bears the costs associated with the disposal of PVB film, which are much more expensive than the recycling of e.g. glass packaging.
The management of laminated glass waste is a global problem, which scientists around the world are trying to solve by developing an effective method of separating and recycling PVB film and glass particles from the resulting waste. Although many studies have been successfully conducted, they are not yet widespread enough to be used on a daily basis. We are waiting impatiently for the solution of this urgent problem.
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