| Abstract | Poli(etilen-tereftalat) jedan je od najviše primjenjivanih polimera u posljednja dva desetljeća, a potražnja za njim kroz godine sve više raste. Odlična svojstva, kao što su visoko talište, niska propusnost na plinove (vodenu paru, O2, CO2), inertnost prema otapalima i kemikalijama, čvrstoća i tvrdoća, žilavost i toplinska stabilnost, omogućuju mu primjenu u brojnim industrijskim granama. Široka mu je primjena u prehrambenoj, tekstilnoj, automobilskoj i građevinskoj industriji pa i u medicini, ali najvažniju primjenu nalazi u izradi PET boca koje su tijekom godina postale najvažnijim proizvodom PET-a. Proizvodnja PET boca odvija se dvama procesima, a oni su injekcijsko prešanje PET predoblika i razvlačno puhanje PET boca koji se mogu odvijati u jednoj ili dvije zasebne faze. Injekcijskim prešanjem rastaljeni se PET ubrizgava u kalupne šupljine gdje poprima oblik predoblika te se kao takav izbacuje iz kalupa, a potom se razvlačnim puhanjem formira u PET boce. Tako nastale boce imaju primarnu ulogu u pakiranju obične i mineralne vode te bezalkoholnih gaziranih pića, no vremenom su postale i ambalaža za pakiranje drugih proizvoda poput mlijeka i mliječnih proizvoda, voćnih sokova, piva, lijekova, kemikalija, kozmetičkih proizvoda, sredstava za čišćenje, umaka, začina i sl. Jedan od glavnih razloga tako široke primjene PET boca mogućnost je njihovog potpunog recikliranja koje je izrazito bitno s obzirom da PET sudjeluje u stvaranju velike količine plastičnog otpada. Prije samog postupka recikliranja, potrebno je provesti pripremu za recikliranje koja se sastoji od sakupljanja, razvrstavanja, usitnjavanja, pranja i sušenja PET boca. Najzastupljeniji postupci recikliranja su mehaničko i kemijsko recikliranje, a kemijsko se recikliranje može provesti metanolizom, hidrolizom ili glikolizom. |
| Abstract (english) | Polyethylene terephthalate is one of the most used polymers in the last two decades, with its demand increasing over the years. Its excellent properties, such as high melting temperature, low gas permeability (water vapor, O2, CO2), inertness to solvents and chemicals, strength and hardness, toughness and thermal stability, allow it to be used in numerous industrial branches. It is widely used in food, textile, automotive and construction industries as well as in medicine but its most important application is in the production of PET bottles, which have become the most important PET product over the years. The production of PET bottles is carried out by two processes: injection molding of PET preforms and stretch blow molding of PET bottles, which can take place in one or two separate phases. In the injection molding process, molten PET is injected into mold cavities where it takes the shape of a preform. These preforms are then ejected from the mold and formed into the PET bottles through stretch blow moulding. These bottles have a primary role in the packaging of still and mineral water and soft carbonated drinks, but over time they have also become packaging for other products such as milk and dairy products, fruit juices, beer, pharmaceuticals, chemicals, cosmetic products, cleaning agents, sauces, spices etc. One of the main reasons for the widespread use of PET bottles is their ability to be fully recycled, which is extremely important considering that PET is involved in generating large amounts of plastic waste. Before the actual recycling process, it is necessary to carry out preparation for recycling, which consists of collecting, sorting, shredding, washing and drying of PET bottles. The most common recycling methods are mechanical and chemical recycling, with chemical recycling being carried out through methanolysis, hydrolysis or glycolysis. |
