Sustainable and Recycled Particulate Fillers

Roger Rothon

Contents

Introduction...................................................................................... 440

Definitions....................................................................................... 441

Linear and Circular Economies.............................................................. 441

Sustainability................................................................................. 441

Renewability................................................................................. 441

Recycling..................................................................................... 442

Sustainability (Renewability) Issues............................................................ 443

Effect of Particulate Fillers on Composite Sustainability................................... 443

Sustainable Sourcing......................................................................... 444

Filler Recycling.................................................................................. 448

Types of Filler Recycling.................................................................... 448

Advantages and Limitations................................................................. 449

Main Sources for Recycled Powders from Other Areas Potentially Useful for Filler

Applications.................................................................................. 450

Recovery and Recycling of Particulate Fillers from Polymer Composites................. 454

Recycling in the Form of a Filled Polymer................................................. 458

Future Prospects................................................................................. 460

Cross-References................................................................................ 461

References....................................................................................... 461

Abstract

Environmental issues, such as life cycle impact and sustainability, are becoming important concerns for most industrial activities. Because of their scale of operation, composite materials are particularly affected, and this is filtering down to their major components, such as fillers.

R. Rothon (*)

Rothon Consultants and Manchester Metropolitan University, Guilden Sutton, Chester, UK e-mail: This email address is being protected from spam bots, you need Javascript enabled to view it

© Springer International Publishing Switzerland 2017

R. Rothon (ed.), Fillers for Polymer Applications, Polymers and Polymeric Composites: A Reference Series, DOI 10.1007/978-3-319-28117-9_21

In defense of using fillers at all, it has been shown that at least in some cases, replacing part of a synthetic polymer by fillers can reduce the environmental impact of a composite. While this is true, more could be done, and the main thrusts are for recycling and the use of renewables. The industry recognizes this; but, despite significant commercial activity, there are difficult obstacles to overcome and only limited success has been achieved so far. Recovery and recycling of fillers themselves is hampered by the low cost of many virgin products and has made little headway. Recycling of waste products from other industries has also made little progress, often due to competition from more valuable alternative applications for the wastes.

More progress has been made where the composite itself is recycled, examples being talc/polyolefin composites in automotive applications. This is much harder to accomplish in cross-linked polymers (thermosets and elastomers), which are inherently more difficult to recycle. The majority of fillers are currently from nonrenewable (although often vast) mineral resources. The exceptions are natural fibers, such as wood, cotton, and flax, and these are considered to be more sustainable.

Despite much effort from the tire companies on products such as starch, renewable particulate fillers have so far made little progress. It has, however, been demonstrated that carbon black can be made from biomass rather than petroleum oil, and this may develop as a significant commercial option in the future.

Despite the difficulties, pressure on the major volume products is only going to increase and we can expect more recycling and use of renewables in the future. This will mainly be in large volume products used in applications such as vehicles.

Keywords

Fillers • Recycling • Sustainability • Glass • Calcium carbonate • Carbon black • Talc • Wood flour • Starch • Lignin • Surface modifiers • Granulation • Pyrolysis • Devulcanization

Introduction

Filler and especially composite manufacturers increasingly have to take environmental matters, such as recycling, sustainability, and life cycle impact into consideration, and these pressures are expected to increase in future. In recent years, the advanced economies have become very much based on linear economics of “extract- make-consume-discard.” But increasing industrialization, affluence, and population are making this model untenable in the medium to long term. Estimates for when we start to run out of resources vary, but all agree that it is fast becoming imperative to find alternative economic models and to use materials more efficiently. We are thus seeing more emphasis on sustainability and especially recycling. This is increasingly being backed up by regulations, such as restrictions on landfill and on the recycling of the components of some major products, such as automobiles (e.g., in the EU, the End of Life Vehicle Directive requires that a minimum of 95% of a vehicles weight must be reused or recycled). Some major customers and retailers such as Wal-Mart Stores Inc. also aggressively apply sustainability scorecards to their sourcing and purchasing processes.

The composite industries are very significant consumers of raw materials (much of it currently nonrenewable) and also large waste generators and so are under considerable scrutiny. This has a knock-on effect on widely used additives such as particulate fillers. It is estimated that over 25 million tons of particulate fillers are currently consumed in polymer applications worldwide. Accurate figures do not exist, but well under 10% of this is currently reused in polymer applications.

Present approaches to this are currently fragmented and still developing, but the main trends in both sustainable resourcing and recycling are discussed here. It should be noted that much of the published information is from trade journals and conferences but not from peer-reviewed publications.

Definitions

Sustainability and recycling are becoming of increasing importance in all areas of human activity which involve materials use. They are also areas where definitions are very important, especially when regulations and commercial claims are involved. This is still a developing area; but the following terms are used in this article.