This article discusses postconsumer plastics recyclate quantities, the classification of plastics recycling into primary, secondary, tertiary, and quaternary categories, and how the life cycle of plastics is affected by recycling. The recycling processes of polyethylene terephthalate (PET), which accounts for the largest percentage of plastic recycling, high-density polyethylene (HDPE) plastics, the other large-volume plastic recyclate, as well as vinyl resins and polycarbonate resins are described. The life cycle of plastics has four phases: poly formation, part fabrication, product service, and disposal. Landfilling is still the primary method of final disposal, and incineration is another option, but recycling has become a viable alternative. The article presents a comparison between secondary and tertiary recycling.

Microbial degradation in the environment is initiated by abiotic (nonliving physical or chemical) processes. Mechanical weathering and other mechanical processes are the main drivers of the initial degradation. This article presents an overview of weathering and biodegradation. It summarizes the main synthetic polymers that are released and available for bacterial and fungal decomposition. The article also presents a detailed discussion on the enzymes that are involved in plastic degradation, and the measurement of polymer degradation.

This article provides practical information and data on property development in engineering plastics. It discusses the effects of composition on submolecular and higher-order structure and the influence of plasticizers, additives, and blowing agents. It examines stress-strain curves corresponding to soft-and-weak, soft-and-tough, hard-and-brittle, and hard-and-tough plastics and temperature-modulus plots representative of polymers with different degrees of crystallinity, cross-linking, and polarity. It explains how viscosity varies with shear rate in polymer melts and how processes align with various regions of the viscosity curve. It discusses the concept of shear sensitivity, the nature of viscoelastic properties, and the electrical, chemical, and optical properties of different plastics. It also reviews plastic processing operations, including extrusion, injection molding, and thermoforming, and addresses related considerations such as melt viscosity and melt strength, crystallization, orientation, die swell, melt fracture, shrinkage, molded-in stress, and polymer degradation.

This article is a comprehensive collection of engineering tables providing information on the mechanical properties of and the techniques for processing and characterizing polymeric materials, such as thermosets, thermoset-matrix unidirectional advanced composites, and unreinforced and carbon-and glass-reinforced engineering thermoplastics. Values are also provided for chemical resistance ratings for selected plastics and metals, and hardness of selected elastomers.