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Notes
1 1 The term should really be “polyethylenes” because any given class of plastic such as PE includes many different grades of the same polymer that differ in their average molecular weight, molecular weight distribution, and polymer chain architecture such as the degree of branching. Despite the identical chemical structure, their key properties including strength, melting point and levels of crystallinity are very different.
2 2 Embodied Energy (EE) is the energy expended in making a unit mass of the material from feedstock or the ore and includes energy used in raw material extraction, product processing, transportation, construction, use/maintenance, and disposal or reuse.
3 3 The multibillion‐dollar plastic resin manufacturing plant coming up in Beaver County, Pennsylvania, is expected to produce 1.6 million metric tons of plastic pellets annually when it opens in 2022.
4 4 Taking the global warming potential of CO2 to be unity, that of methane is 28–36, nitrous oxide 265–298 and fluorocarbons is 104 or 105!
5 5 Fracking is a technology used to recover natural gas (or even oil reserves) from shale, sandstone, limestone, and carbonite. The fracking liquid (water with dissolved chemicals) pumped under high pressure into the deep vertical fracking wells can contaminate the water table as well as streams or lakes from the invariable leaks and spills. Air pollution due to release of gas (venting or flaring) during the process is also a serious problem. With a majority of the producing wells using hydraulic fracking the cumulative effect on the environment is believed to be very significant. But, it is the boom in fracking that guarantees low‐cost natural gas in the US.
6 6 Bioplastics market data. https://www.european‐bioplastics.org/market/. Accessed March 1, 2021.
2 Plastic Additives in the Ocean
Jennifer M. Lynch1,2, Katrina Knauer3, and Katherine R. Shaw1,2
1 Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD, USA
2 Center for Marine Debris Research, Hawaii Pacific University, Honolulu, HI, USA
3 Novoloop, Inc., Menlo Park, CA, USA
2.1 Function of Plastic Additive Classes
The ecological and toxicological effects of plastic in the marine environment are generally discussed or modeled as if they were “pure” polymers (Cole et al. 2015; Kaiser et al. 2019; Yin et al. 2018); yet, no plastic that exists in the waste stream today is manufactured without additives or as a “barefoot” formulation. Every piece of plastic is made up of a unique combination of the host polymer, with some residual monomers or catalysts, as well as chemical additives added during processing of the plastic (Hahladakis et al. 2018; Hermabessiere et al. 2017). A staggering amount of different kinds of additives are used in plastic formulations and each of them plays a distinct role in delivering/enhancing the functional properties, performance, or appearance of a plastic product (Marturano et al. 2016). Depending on the formulation, plastics may contain anywhere from <1 to 50% or more by weight of plasticizers (Chaudhary et al. 2016; Marturano et al. 2016). Typically, plasticizers, fillers, and flame retardants (FRs) are used at high weight fractions in plastic formulations and, therefore, account for about three‐quarters of all additives produced. Other additives, such as antioxidants and light stabilizers, are used at much lower loadings. Despite the popular conception that plastics last forever, they are organic materials that undergo significant degradation when exposed to processing or environmental conditions, including high temperatures, ultraviolet (UV) radiation, oxygen in the atmosphere, and water (see Chapter 8). The durability and performance that is expected from thermoplastics would not be possible without these intentionally added chemical compounds. The production and use of plastics (and, therefore, plastic additives) has continued to increase exponentially since the mid‐20th century (Binetti et al. 2008). If current production rates continue, a total of 2000 million metric tons of additives will have been produced by the end of 2050 (Geyer et al. 2017). This is based on an estimate of plastics containing on average 7% additives by mass (Geyer et al. 2017). It has been estimated that at least 190 metric tons of additive chemicals entered the ocean in 2015 alone, a rate that is expected to double by 2025 (De Frond et al. 2019). The decades’ worth of plastics already in the ocean was formulated without consideration for marine disposal.
This chapter aims to introduce plastic additives with a focus on their chemistry and function, transport and fate, detection