Thermal and Mechanical Properties of the Recycled and Virgin PET—Part I

Abstract

In various countries, polyethylene terephthalate (PET) represents one of the plastics with a very high recycling rate. Since currently there is no analytical method enabling direct distinction between recycled PET (rPET) and virgin PET (vPET), there are various attempts to differentiate these materials indirectly. One of these approaches claims that the recycling of PET leads to polymer chain degradation, which is reflected in changed thermal, mechanical and crystalline properties, and testing of these properties can therefore be used to distinguish rPET and vPET. However, there are many sources leading to changes in the molecular structure and consequently to the changes of the above-mentioned properties of the PET. The purpose of this study is to analyze the glass transition and melting temperature, degree of crystallinity as well as bending and impact properties of 20 different commercially available PET recyclates from 14 suppliers and evaluate the results with respect to the literature values for vPET. The main results of this study show that the range of vPET properties is so broad that all of the corresponding properties of the tested rPET lie within this range.

Bio-Based Degradable Poly(ether-ester)s from Melt-Polymerization of Aromatic Ester and Ether Diols

“…However, all of the copolymers maintained satisfactory T g values and melting points when compared to existing vanillin-derived polyesters and their analogous petro-chemical counterparts such as PET. HC1 had a T g reaching 120 °C, which suggests that the crystallinity level of that sample was superior to PEV [ 55 ] and PET [ 68 ] homopolymers. The copolymer compositions leading to high chain mobility promoted the alignment of their long-chain structure, which induced rapid crystal growth at elevated temperatures (T c = 156 °C), as observed during the cooling scan from the melt.…”

“…To investigate the influence of ether-ester bonds on the mechanical properties, the tensile test results can be compared with those obtained for vanillin-based polymers such as PE-ms, furan-based PBFGA and conventional PET, synthesized by Zamboulis [ 55 ], Pang [ 59 ] and Celik [ 68 ], respectively. The stress–strain curves for the poly(ether-ester)s are provided in Figure 9 b, and the mechanical parameters extracted from them are listed in Table 3 .…”

Understanding the Structure–Activity Relationships in Catalytic Conversion of Polyolefin Plastics by Zeolite-Based Catalysts: A Critical Review

“…In the following decades, the undegradable property has made plastics competitive materials and been promoted worldwide. − As a result, the rapid accumulation of plastic waste has brought about serious environmental pollution problems, caused massive damage to the ecosystem, and threatened human health. − In contrast to the increasing amount of plastic waste generated yearly, only a small proportion of plastics are recycled. Most plastic waste is disposed of by landfill or incineration for energy recovery accompanied by toxic byproduct formation. , Besides, mechanical recycling, especially applicable to thermoplastics such as PET bottles and some polyolefin resins, will convert the plastic waste into the former plastic but will generally lead to degradation of thermal, physical, and mechanical properties. , Based on the current situation mentioned above, more eco-friendly and economical recycling of plastic waste needs to be explored urgently. Emerging as promising alternatives, chemical recycling and upcycling offer exciting opportunities to transform plastics into a series of value-added products, such as high-purity monomers for repolymerization, hydrogen and light cracking feed oil for fuels, value-added chemicals including light olefins and aromatic compounds, functional carbon materials etc. − Among all kinds of plastics, polyolefins, mainly consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polypropylene (PP), are of particular significance, since they are the most consumed plastics in the world, accounting for 57% of total municipal solid waste. , …”

Polystyrene-Free Chain Extenders for Recycled Poly(ethylene terephthalate)

“…Approximately 40% of rPET in Europe is downcycled for low-end applications (e.g., nonfood grades). 4 In addition, PET that is currently not recycled is valuable enough to warrant research and development (R&D) efforts to increase collection and recovery through advanced recycling techniques or by maximizing features that facilitate recycling, such as enhanced labeling and the reduction of secondary materials. Efforts have been focused on recycling PET, the most recycled plastic.…”

“…Polyesters, especially poly­(ethylene terephthalate) (PET), are widely used in packaging (e.g., beverage bottles, thermally stabilized films), textiles (fibers), and many engineering applications because of their excellent mechanical strength, chemical resistance, excellent electrical insulation, and thermal resistance. − Recycled PET (rPET) is mainly obtained from beverage bottles because a better collection infrastructure exists for bottles than for other types of municipal solid waste (MSW). Approximately 40% of rPET in Europe is downcycled for low-end applications (e.g., nonfood grades) . In addition, PET that is currently not recycled is valuable enough to warrant research and development (R&D) efforts to increase collection and recovery through advanced recycling techniques or by maximizing features that facilitate recycling, such as enhanced labeling and the reduction of secondary materials.…”