CONTENTS
12.1 Introduction and synopsis
12.2 Metals and alloys
12.3 Polymers
12.4 Ceramics and glasses
12.5 Hybrids: composites, foams, and natural materials
12.1 Introduction and synopsis
You can’t calculate anything without numbers. This chapter provides them.
It takes the form of double-page data sheets for 47 of the materials used in the greatest quantities in modern products. The sheets list the annual production and reserves, the embodied energy, process energies, and the carbon footprints associated with these. They list, too, the general, mechanical, thermal, and electrical properties, important because it is these that determine the environmental consequences of the use phase of life. And they provide basic information about recycling at end of life.
Each section starts with a brief introduction to a material family: metals and alloys, polymers and elastomers, ceramics and glasses, and hybrids 265
(composites, foams, and natural materials). Within a section the material
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Table 12.1 The Material Profiles |
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|
Metals and alloys |
Polymers and elastomers |
Ceramics and glasses |
Hybrids: composites, foams, and natural materials |
|
Aluminum alloys |
ABS |
Brick |
CFRP |
|
Magnesium alloys |
Polyamide PA |
Stone |
GFRP |
|
Titanium alloys |
Polypropylene, PP |
Concrete |
Sheet molding compound |
|
Copper alloys |
Polyethylene, PE |
Alumina |
Bulk molding compound |
|
Lead alloys |
Polycarbonate, PC |
Soda-lime glass |
Rigid polymer foam |
|
Zinc alloys |
PET |
Borosilicate glass |
Flexible polymer foam |
|
Nickel-chrome alloys |
PVC |
Paper and cardboard |
|
|
Nickel-based superalloys |
Polystyrene, PS |
Plywood |
|
|
Low carbon steel |
Polylactide, PLA |
Softwood, along grain |
|
|
Low alloy steel |
PHB |
Softwood, across grain |
|
|
Stainless steel |
Epoxy |
Hardwood, along grain |
|
|
Cast iron |
Polyester Phenolic Natural rubber, NR Butyl rubber, BR EVA Polychloroprene, CR |
Hardwood, across grain |
profiles appear in the order shown in Table 12.1. Each data sheet has a description and an image of the material in use. The data that follows are listed as ranges spanning the typical spread of values of the property. When a single ("point") value is needed for exercises or projects, it is best to use the geometric mean of the two values listed on the sheet.1
A warning. The engineering properties of materials—their mechanical, thermal and electrical attributes—are well characterized. They are measured with sophisticated equipment according to internationally accepted Standards and are reported in widely accessible handbooks and databases. They are not exact, but their precision—when it matters—is reported; many are known to 3-figure accuracy, some to more.
The eco-properties of materials are not like that. There are no sophisticated test-machines to measure embodied energies or carbon footprints. International standards, detailed in ISO 14040 and discussed in Chapter 3, lay out procedures, but these are vague and not easily applied. The differences in the process routes by which materials are made in different production facilities, the difficulty in setting system boundaries and the procedural problems in assessing energy, CO2 and the other eco-attributes all contribute to the imprecision. [50]
So just how far can values for eco-properties be trusted? An analysis, documented in Section 6.3, suggests a standard deviation of ±10% at best. To be significantly different, values of eco-properties must differ by at least 20%. The difference between materials with really large and really small values of embodied energy or carbon footprint is a factor of 1000 or more, so the imprecision still allows firm distinctions to be drawn. But when the differences are small, other factors such as the recycle content of the material, its durability (and thus life-time) and the ability to recycle it at end of life are far more significant in making the selection.
