Material profiles

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

Table 12.1 The Material Profiles

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.