Download Introduction to Plastics Recycling Second Edition PDF

TitleIntroduction to Plastics Recycling Second Edition
File Size1.4 MB
Total Pages184
Table of Contents
                            Contents
Preface
1 Introduction
2 Back to Basics
	2.1 Polymers
	2.2 Thermoplastics
		2.2.1 Polyolefi ns
		2.2.2 Polyamides
	2.3 Thermosets
	2.4 The Formulation of Plastics
	2.5 Why Does Recyclate Always Seem to be Black?
	2.6 What Are Recyclates Used For?
3 The Effects of Processing on Thermoplastics
	3.1 Rheology
	3.2 Heat
	3.3 Physical and Chemical Changes
	3.4 Assessing Property Deterioration Caused by Repeated Cycling by Injection Moulding
	3.5 Short-Term Mechanical Testing
		3.5.1 Tensile Testing
		3.5.2 Impact Testing
		3.5.3 Tensile and Impact Testing of Recycled Expanded Polystyrene
4 Why Plastics Need to be Sorted
5 Reprocessing of Thermoplastic Recyclates
	5.1 Contaminants
	5.2 Recycling Techniques
	5.3 Size Reduction
	5.4 Washing
	5.5 Identification and Sorting of Plastics
	5.6 Agglomeration
6 Processing Techniques
	6.1 Extrusion
		6.1.1 Introduction
		6.1.2 Compounding
		6.1.3 Single-Screw Extruders
		6.1.4 Twin-Screw Extruders
		6.1.5 Co-Extrusion
	6.2 Supply Chains for Compounds
	6.3 Injection Moulding
		6.3.1 Waste During the Injection Moulding Process
		6.3.2 Co-Injection Moulding
	6.4 Blow Moulding
		6.4.1 Extrusion Blow Moulding
		6.4.2 Injection Blow Moulding
	6.5 Weld Lines
	6.6 Film Blowing
	6.7 Compression Moulding
	6.8 Thermoforming
	6.9 Processes for Incorporating Mixed Plastic Waste
		6.9.1 Intrusion Moulding
		6.9.2 Transfer Moulding
		6.9.3 Sinter Moulding
	6.10 Conclusion
	6.11 Case Study: Plastic Lumber
7 Additives for Recyclates
	7.1 Introduction
	7.2 The Degradation of Plastics
	7.3 Restabilisation of Recyclates
	7.4 Testing the Effects of Stabilisers
		7.4.1 Processing Stability
		7.4.2 Heat Stability
		7.4.3 Light Stability
	7.5 Stabilisers
		7.5.1 Thermal Stabilisation
		7.5.2 Light Stabilisation
		7.5.3 Additive Combinations for Specific Purposes
	7.6 Modifying the Properties of Plastics Through Incorporation of Miscellaneous Additives
		7.6.1 Degradable Plastics
		7.6.2 Compatibilisers
8 Other Methods of Recycling and Waste Disposal Options
	8.1 The Case of Thermosets
	8.2 Chemical Recycling
	8.3 Thermal Conversion Technologies
		8.3.1 Pyrolysis
		8.3.2 Hydrogenation
		8.3.3 Gasification
	8.4 Energy Recovery
9 Creation of a Recycling and Recovery Infrastructure for Plastics
	9.1 Development
	9.2 Developing Recyclate Markets
10 The Problem in Perspective: Europe
	10.1 Case Study: Packaging
	10.2 Integrated Product Policy
		10.2.1 Waste Electrical and Electronic Equipment Directive (WEEE) 2002/96/EC
		10.2.2 End of Life Vehicles Directive (ELV) 200/53/EC
	10.3 Conclusion
11 Rise of the Biopolymers: Recycling versus Degradation
Abbreviations and Acronyms
Glossary
Index
Titles of Related Interest
                        
Document Text Contents
Page 1

Introduction to
Plastics Recycling

Second Edition

Vannessa Goodship

Page 92

84

Introduction to Plastics Recycling – Second Edition

6.4.2 Injection Blow Moulding

Injection and extrusion blow moulding take their names from the
methods used to produce the tube for blowing. In extrusion blow
moulding the tube is called the parison, in the case of injection blow
moulding it is termed a preform. Thus in injection blow moulding,
injection moulding is used to produce the preform.

The process sequence for injection blow moulding is as follows:

• The preform is injection moulded.

• It is transferred to a blowing station and infl ated inside
a mould.

• It is transferred to a station where it is stripped from
the mould.

The process thereby uses two moulds, one for injection and one for
blowing. There are several advantages to injection blow moulding.
From a waste management point of view the major advantage over
extrusion blow moulding is that no trim scrap is produced during
moulding. By injection moulding the preform, accurate control can
be maintained on both the neck moulding and the preform itself,
in terms of dimensional accuracy and wall thickness. However,
only simple shapes can be produced, unlike in extrusion blow
moulding where handles can be incorporated into the moulding.
Generally, injection blow moulding makes use of PET, PVC and
PP. Bottles produced by this method can be recognised by a mark
on the base of the moulding, which shows the injection point of
molten material into the injection moulding tool, from injection
moulding of the preform.

Like extrusion blow moulding, injection blow moulding places
very specifi c demands on the raw material it uses and is intolerant
to contaminants. Regrind from in house waste may be utilised
providing attention is paid to cleanliness.

Page 93

Processing Techniques

85

6.5 Weld Lines

Whenever molten fl ows come together a weld line will be produced.
Weld lines are common to almost all processing operations as
often on passing through extruders or moulds (extruder dies,
injection moulding tools, blow moulding tools), molten fl ows will
meet obstructions which split material into different streams, this
is shown in Figure 6.15. How well the materials can ‘knit’ back
together, will affect the weld line strength.

Figure 6.15 Molten material fl owing around obstruction

In extrusion blow moulding of bottles, for the bottle to be sealed
the parison must weld at the seam. The parison is pressed together
by the blow moulding tool, creating a weld line as shown in
Figure 6.16.

Figure 6.16 Cross-section of a parison as it is welded to form
the base seal

Page 184

Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
Telephone: +44 (0)1939 250383
Fax: +44 (0)1939 251118
Web: www.rapra.net

Introduction to Plastics Recycling provides information on plastic materials

and technology in relation to the options for, and problems associated with,

recovering and recycling plastics.

This new edition discusses the increase in recycling rates worldwide in recent

years. It considers the expansion of infrastructure in the UK to support plastic

recycling, and major achievements that have been made in gaining widespread

public support and participation for recycling schemes.

It considers relevant issues, such as the biodegradability versus recycling

debate; broad policies including council recycling of plastic bottles; the practice

of providing free plastic carrier bags by supermarkets; through to individual

steps to reduce household waste. This edition further expands on the wider

context of plastics waste management, life cycle analysis and legislation.

Introduction to Plastics Recycling is written in a clear style by an accomplished

expert in the field, with explanations of terminology and useful illustrations. It

is accessible to a broad audience both within and outside the polymer industry

as a useful guide to the ongoing developments in plastics recycling.

Published by Smithers Rapra, 2007
ISBN: 978-1-84735-078-7

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