## 2 Thermal Pyrolysis
### Feedstock Types and Possible Degradation Reactions  
Polymeric materials are a common raw material in a wide range of industries, sectors, and services. One of their most significant advantages is their ease of processing and high applicability to diverse technological solutions. Polymers have numerous industrial applications that have been well documented for many years and are composed of several assemblies of simple monomers. However, some fractions are more important than others in applications. Their significance can be seen in the share of their global consumption shown in Table 2.  
Polymeric materials are applied in a wide range of industries, including automotive, construction, furniture, electronics, and telecommunications. Furthermore, polymers are used in healthcare, but unlike the previously mentioned uses, this sector does not allow for material recovery because medical materials must be disposed of neutrally. The most common materials are PE (polyethylene), PP (polypropylene), and PVC (polyvinyl chloride) (Table 2), which account for nearly 70% of total plastic applications and demand globally. Their application potential is determined by their quality and physiochemical properties. Polystyrene and thermosetting plastic blends have also played important roles, accounting for roughly 20% of total global use. The remainder of the worldwide market includes various specialised fractions such as PA (polyamide), PBT (polybutylene terephthalate), and ABS (acrylonitrile budadiene styrene). All these materials have unique physicochemical features that influence their applications and processing. The existence of these constituents, particularly volatiles and carbon content, has a considerable impact on its subsequent application, particularly during thermal pyrolysis. All plastics have a volatile content of more than 90%. On the other hand, the amount of fixed carbon content varies from 0.04% for PE to 6.3% for PVC and 7.77% for PET. Based on the monomers, the process of polymerization, and the creation of copolymers with different parts in different amounts, a wide range of physical and chemical properties can be made [34]:  
* Polyolefins, such as PE/PP, are extremely inert and hydrophobic, with a low density. * Poly(tetrafluoroethylene) PTFE (Teflon) has an ethylene backbone and four fluorine molecules that are covalently bonded. * Poly (vinyl chloride) PVC has an ethylene backbone with one covalently bonded chlorine
* Silicone -Si-O- has a backbone with a variable chain length and crosslinks that govern its mechanical properties and ranges from liquid oil to gel to rubber elastomer. Polyolefins silicones are notable for being hydrophobic and biostable elastomers. * Methacrylate's (PMMA) properties include substantial stiffness, and its primary application is in medical applications (orthopaedics and dentistry). * Polyesters are biodegradable and biostable polymers that are also used in biomedicine (drug-eluting coatings, orthopaedic applications, etc.). * Polyurethane can be synthesised in a variety of chemistries and characteristics. This large group's structure is flexible due to the combination of hard and soft segments. Some fractions are flame-retardant, steam-resistant, or operate at high/low temperatures. Medicine uses many polymers. General surgical implants, orthopaedic implants, temporary in vivo applications (wound dressings, vascular catheters), ophthalmology, and dentistry are key medical areas. Plastics are used in many economic sectors, but each product is profitable. Life cycle ends = trash. This means the owner or manufacturer discards, plans to discard, or must discard it. Different methods are used. Preventing waste is the most environmentally friendly option, but manufacturing byproducts cannot be eliminated. In addition to removing byproducts, solutions should neutralise them. Plastic pyrolysis produces good results. A method without air access decomposes raw material by degrading polymer chains into monomers.