Table Of ContentPLASTICS IN BUILDING STRUCTURES
Conference organised by
THE PLASTICS INSTITUTE
in association with
THE INSTITUTION OF CIVIL ENGINEERS
THE INSTITUTION OF STRUCTURAL ENGINEERS
THE ROYAL INSTITUTE OF BRITISH ARCHITECTS
COMMITTEE
The Plastics Institute
D. S. Mahon BSC, FPT (Chairman)
J. C. Barford BSC, API
W. Dawson BSC, PHD, ARIC, AMICHEME
Z. S. Makowski DIPL ING, PHD, DIC, AMICE
R. F. Salmons BSC(ENG), AMIMECHE
The Institution of Civil Engineers
J. W. Bailey BSC(TECH), AMICE
A. J. Harris BSC, MICE, MI STRUCT E, M CONS E
The Institution of Structural Engineers
H. G. Allen BENG, PHD, AMICE, A MI STRUCT E
C. B. Stone DSO, BSC(ENG), MICE, MISTRUCTE
The Royal Institute of British Architects
R. D. Gay DIP ARCH, ARIBA
I. Fraser A A DIPL, ARIBA
PLASTICS IN BUILDING
STRUCTURES
Proceedings of a conference held in
London, 14-16 June 1965
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Copyright © 1966
The Plastics Institute
First edition 1966
Library of Congress Catalog Card No. 65-28542
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[2413/66]
Foreword
THIS volume contains the full text of all the papers which were presented at the conference,
together with an edited record of the discussions which followed the presentation of each paper.
In addition it contains the text of a few papers (two from overseas authors) which were either
submitted too late or for other reasons could not be included in the conference programme but
which the Committee judged made a valuable contribution to the over-all knowledge on their
respective subjects.
We believe that this volume provides an extremely valuable record of the state of knowledge
in June 1965 of the application of plastics materials in structures. It quite clearly highlights a
number of subjects, particularly performance in fires, where intensive research and development
work will be necessary if plastics materials are to make a full contribution to progress in the building
industry.
We gratefully acknowledge the work done by representatives of the Institution of Civil
Engineers, the Institution of Structural Engineers, and the Royal Institute of British Architects
on the Conference Committee, which contributed so much to the success of the conference.
D. S. MAHON,
Chairman, Conference Committee
vu
1
Paper 1
SfB Dn6
U DC 691.175
Building in plastics—plastics in building: what is needed
R. D. Gay, DIP ARCH, ARIBA
The building industry being rather backward, the plastics industry perhaps suffering
from a false image, and both being concerned in housing—one of the most urgent
tasks of the day—the problem of securing dependable data for the architect must
be faced. With the resulting growth of confidence the exciting new range of materials
on the horizon will in due course be exploited to the great advantage ofthe industries
and the community.
1 The industries profession as if they were of inferior quality. The
philosophy that defines invention as only an abstract
The building industry is one ofthe backward industries
process conceived with a 6B pencil in one hand,
of western civilization. It is only now emerging from
construction thereafter being left to a technician to
the period when a builder considered himself mechan-
make it work, is doomed to failure by virtue of its
ized if he possessed steel wheelbarrows. Today, only a
innate schism. The assessment of the economics and
small proportion of builders are making economical
efficiency of a conception in production-engineering
use of mechanical aids and production-engineering
terms is something practised by other industries.
methods.
Generally, those who build are unconcerned with the
About 40 per cent of the United Kingdom building
conception and uninterested in assessing the designer's
industry's labour is employed on maintenance and
achievements. That is something between the architect
jobbing work. A far greater percentage - probably
and his client. The builder's activity is concerned with
impossible to assess accurately - can be classified as
constructing in the shortest possible time compatible
semi-skilled or unskilled. Each year this percentage
with the minimum inconvenience and maximum
appears to increase. An affluent society does not
profit almost without regard to quality and obligation
create conditions conducive to attracting skilled
to society. A high standard of workmanship is not
labour to open-air work, subject to the hazards of a
implicit today; it has to be specified and it costs more.
British climate with virtually uncivilized lavatory and
The advantages to be gained by appointing the builder
eating facilities, dirty working conditions, and irregular
to work in parallel with the professional team during
travelling arrangements, with the overshadowing
the design stage are frequently of paper value. The
uncertainty whether the tradesman - when he gets to
industry mainly consists of small firms without the
the building site - will be able to put in a full day's
necessary finance for essential large-scale development
productive work. It is of little wonder that the skilled
work, though the commercial pressure ofthe industrial
labour force of this industry continues to be attracted
world at large may force the smaller firms out of
to heated factories with properly organized employee
business.
and welfare services, subsidized canteen meals and the
dubious benefits of 'music while you work'.
Party-political competition resulting from estab-
The United Kingdom building industry spends little lished prejudices and national necessity have committed
on research. In 1963 it contributed less than half of one the construction industry to an annual programme of
per cent of the total research expenditure in private 400000 houses, innumerable hospitals, educational
industry. The position has probably improved a very buildings and roads, for at least ten years with an
little in the last two years. It is reported that the pro- inevitable increase after that. The housing band-wagon
portion is no greater in other western countries. The is in motion and about 400 builders have already
industry is sadly lacking in inventiveness and is con- jumped on, each with his industrialized building system ;
servative in accepting innovation. Its very constitution 95 per cent of these systems are ill-conceived, un-
is inhibitive, being carefully divided into those who suitable, based on ignorance of basic research and
design and those who build. The architects are pre- national requirement, and generally ugly. Many rely
vented by the established protocols and statutes of on concrete which, because of its mass, is difficult and
professionalism from developing their ideas on expensive to transport from factory to site, is too
commercial lines. In spite of their ability to analyse and frequently drab and lifeless when used in large quan-
co-ordinate, the majority of architects shield them- tities in a northern climate, is expensive when associated
selves behind the facade of a dilettante club. Those with with applied finishes, and is also the staple diet of the
technological ideas are treated by the others of their remainder ofthe building industry and civil engineering
Mr. Gay is with Mathews Ryan Simpson, Chartered Architects, London. A
2 R. D. GAY
industry. There is also the problem of the limited supply plastics fabricators - have misled the plastics industry.
of raw materials which will have to be faced. Most building projects assume, by necessity, a one-off
status. Even within the domestic field considerable
Insufficient attention has been paid by industrialized-
variation results from size, social behaviour, geo-
system builders, and the industry as a whole, to the
graphical location and siting. Certain restrictive
problems of the sand and gravel industry. The Water
influences appear inflexible; building and fire regu-
Committee Report, 1951, analysed - area by area -
lations and sound-attenuation requirements combine
the reserves and anticipated surges and future demands.
against the use of plastics materials. There exist major
The geological survey was inadequate and in some
difficulties of communicating with the building
respects erroneous. The anticipated demands were
industry. Whatever the problem, and its order of
conservative; 40 to 45 million tons per year in the
magnitude, it must be realized by both industries
immediate post-war years has already topped 100
that there will be, in a few years, the absolute necessity
million tons per year, and at the present rate of increase
for new materials, used in new ways. A large proportion
will reach 300 million tons per year within the next 10
of these must emanate from the organic-chemical
to 15 years. Already, in north-west England, the
industry, used alone or in conjunction with contem-
supplies are running out and aggregates are being
porary developments in the steel, aluminium and,
imported from pits situated 40 to 50 miles from the
perhaps, other industries.
building sites. The London reserves are likely to last
not more than 7 years and in the eastern counties the
The plastics industry has only itself to blame for the
situation is worse. It is true that new reserves have been
current image derived from the 'wipe it down with a
located in the sea, and that there are some untapped
damp cloth' and 'the colour goes right through' sales
sources under protected areas which can provide a few
slogans, the cheap imitations of the domestic and toy
more years' supply at the cost of our national heritage.
markets, the inappropriateness and inadequacy of
However, it must be emphasized that the future will
designing in ignorance of customers' requirements.
rely on exceptional transport arrangements, and that
It is beginning to understand that the building industry
the distance of 13 miles doubles the pit-head price of
talks in another language, complies with a different code
each cubic yard of sand and gravel. The current costs
of behaviour, is highly discerning in its scrutiny of the
of concrete systems realizea l/10to 1 per cent advantage
deluge of sales literature, needs technical data at its
over systems employing other materials. Parity is
elbow, and does not appreciate the reasons for the
unlikely to be maintained if the competitiveness of the
secrecy of the raw-materials producers. The plastics
sand and gravel constituents depends on preferential
industry does not understand why the building industry
rail-transport arrangements. Road transport cannot
is generally unable to answer direct questions as to its
be economic for long haulage distances. Other materials
requirements, or, if it does, why the answers are always
will have to assist the building industry in achieving
conditioned by influential variations.
its programmes.
The building industry does not understand the direct
Industrialized building is seen to be inevitable,
relationship between invention and commercial
but at what cost? The architecture of a nation reflects
stability. To establish an advisory body, such as the
the extent of its expanding economy and its tech-
Cement and Concrete Association, is comparatively
nological and sociological progress. A casual study of
simple when it is realized that the basic elements are
building in the United Kingdom over the last 20 years
few, well-known and reasonably non-competitive. To
reveals the general absence of an expanding economy
create similar bodies for plastics materials is entirely
and inventiveness. The building industry must become
different. The competition is both national and inter-
aware that methods based on traditional and con-
national, as is the capital investment, the control and
ventional raw materials are dying and must be sup-
'know-how' arrangements. Innovation leading to new
planted, within the next 20 years, by new systems based
patents can give a raw-materials company a 10 to 15
on new materials.
years advantage to enable exploitation and recovery
From where will most of these materials originate of capital invested in research, although recent case
but the petrochemical industry with its organic- histories indicate a considerable reduction in this
chemical by-products? Apart from some limited but period.
worthwhile research into domestic 'heart-units' there is
little work undertaken on the broader front, at least 2 The problems
not within the building industry itself. Has the plastics
In general terms, all plastics materials can be said
industry started? For nearly five years the building
to be combustible. Their behaviour in a fire is therefore
industry has been aware of the plastics industry's
a major factor in considering these materials for
mounting interest in its affairs. Today there is evidence
incorporation in a building structure. Those persons
of a certain cooling off, resulting from a combination
responsible in the United Kingdom for administering
of disillusionment and re-thought. Plastics products
building regulations, fire-prevention and means-of-
and components continue to invade the building
escape requirements tend to be conservative and ultra-
scene, but more as a result of the small fabrication
careful in their acceptance of components wholly or
companies' overt eagerness than of the raw-materials
partly formed of plastics materials. This is under-
giants' promotions.
standable. Their knowledge of the new materials is
It is apparent that the politician-painted pictures of meagre; their regulations, advisory notes and ex-
hundreds of thousands of houses - the order of quan- perience are derived from another era with another
tities needed for economic production by thermo- set of materials ; similarly, fire tests are undertaken by
BUILDING IN PLASTICS—PLASTICS IN BUILDING! WHAT IS NEEDED 3
methods evolved for other materials, building types and definite and have earned the respect of the building
social concepts. industry for that reason. Prima facie, the regulations
restricted new solutions and materials, but the authority
Not least of the problems is the difficulty in evalu-
overcame this in the wide powers given to its district
ating plastics materials by fire tests to BS 476 Parts 1
surveyors and officers at County Hall.
and 3. It is generally accepted that the spread-of-flame
test shows plastics in a false light, ranks them in- The imminent transfer of responsibility for building
correctly in comparison with each other and with other control to the Ministry of Public Building and Works
combustible materials, and reveals different apprecia- presents the central Government with a remarkable
tions from those obtained by foreign tests- particularly opportunity to re-appraise every aspect of building
the United States Fire Underwriters' tunnel test. In control and, in particular, the attitudes and prejudices
short, it is felt that plastics materials are being unfairly towards innovation. The Building Regulations Ad-
stigmatized. visory Committee, in its First Report published in
February 1964, made praiseworthy recommendations
New approval tests must now be introduced to
in the general fields of presentation and administration.
indicate the general burning characteristics and
With respect to the eminent officers of that Committee,
behaviour of these materials and their contribution to
a study of the detailed recommendations seems to
a fire. It is essential to embark upon a series of tests
indicate that it has been a long time since they had been
simulating fires in building structures wholly or partly
personally involved in the task of selling a new con-
of plastics.
structional idea to a local authority officer.
The building industry must insist on being properly
informed of the burning behaviour and contribution If accepted, the now infamous Appendix IV of the
to a fire of plastics and other combustible materials by First Report could be interpreted as the death-knell
tests designed to ensure comparative analysis. The Fire for internal linings made from plastics materials. If
Research Station should lead the industries in this work, responsible professional advisers can be so ill-informed
but it is essential that other responsible bodies should on linings, what shall we expect for structural plastics ?
finance the testing of materials, components and struc- We can but hope that the long period in evaluation of
tures, to accelerate the establishment of performance public criticism of the first building regulations (drafted
data and relieve the congestion at the F.R.S. There are by a Working Party for the Minister of Housing and
no political or statutory obstacles to prevent other Local Government) and the reactions to the Advisory
interested bodies or companies from installing equip- Committee's Report, indicate a broader approach to
ment to undertake tests by methods approved by the the whole subject and, by inference, a more rational
F.R.S. acceptance of innovation.
In the 19th century British engineers led the world
It is of paramount importance that building regu-
with their inventiveness in statics and dynamics.
lations and other requirements do not inhibit the
The United Kingdom and many parts of the world
introduction of new materials or components in-
are studded with their achievements. Free from the
corporating plastics where they are able to perform a
restrictiveness of regulations the brilliant excelled,
function as well as conventional materials. The
and conceived the well-known bridges, wide-span
regulations should be administered to obviate the
arch roofs, reciprocating and beam engines, the Besse-
situation where a material or component can be
mer process, and many other great works, while the
accepted for use in one locality and be rejected for an
less brilliant produced the uninspiring and the failures.
identical purpose in another. It is no reason to inhibit
Whatever the record, these works added up to experi-
the use of any material because its properties are
ence.
entirely different from those materials inherited from
our predecessors. We must continue to learn and reject In the 20th century engineers are once again
19th-century methods of evaluating 20th-century presented with exciting new materials with tremendous
problems where inappropriate. Such criticism can be potentials. Whether as a result of the division of
made of the fire insurance companies and the building engineers into cell-like sub-professions, or of the over-
societies responsible for financing private house powering restrictiveness of building regulations, the
purchases, as it can of the official bodies responsible for civil and structural engineers have failed to grasp the
establishing and administering the regulations. opportunities offered by plastics, and, in particular,
reinforced plastics. Some architects - perhaps promp-
Building regulations should always be precise and
ted by a search for a new fashion or the desire to be
definite, but at the same time they should not prevent
different - a few civil engineers and a few chemical
the introduction of new solutions, methods and
engineers are developing plastics structures based on
materials. The Model Byelaws for Buildings, issued by
the lessons learned from reinforced-concrete folded-
the Ministry of Housing and Local Government
plate and shell structures, and metal single- or double-
under the Public Health Acts, fulfilled none of these
layer flat grid structures, and stressed skins.
functions and their interpretation has been left in the
hands of local building inspectors who are often Generally, civil and structural engineers do not
biased against innovation by restricted experience, appear to be displaying initiative. Uninhibited by
insufficient qualifications, lack of central Government stringent regulations other engineers are developing
support in granting wider powers, or local political boats and bodies for motor cars, buses, haulage
influences. The building regulations administered by vehicles, railway freight containers and coaches in
the London County Council under the London glass-reinforced plastics with the enthusiasm and
Building Acts have always been both precise and inventiveness of their 19th-century predecessors. Let
4 R. D. GAY
us hope their industries at the board room level do market. Expansion in the use of plastics must benefit
not apply the same stranglehold. both the industries and, by inference, the national
economy. The plastics industry needs a market such
The materials are available; the challenges exist.
as that of the building industry if it is to maintain the
The situation should be sufficient to induce a large
phenomenal growth-rate experienced since 1945. The
number of building engineers to try for themselves.
building industry needs new materials to solve its new
At the same time they should be under no delusions :
problems. Ways must be found to overcome the in-
the data on properties of these materials do not exist
creasing waste due to corrosion. New materials and
in the form required - the plastics industry has not
techniques are needed to assist the transition in
learned to present them in that way; some data are
building from site construction to site assembly of
not yet available, because the building professions have
factory-made components, - especially materials of
not made known what they require and how. There
high strength-to-weight ratio, easy to transport and
are no 'codes of practice' ; no text books are available
erect, compatible with factory techniques, and adapt-
for the design of building structures - for a decade we
able to production-engineering concepts. The industry
have been awaiting one from Dr. Dietz and his
needs new materials to ensure economical building in
colleagues at the Massachusetts Institute of Technology.
an era of continual increases in cost of supplying and
But there are articles and reference works on the design
fixing conventional materials.
of reinforced plastics for other purposes and, in
particular, boat structures. One cannot doubt these needs when considering the
building industry's failure to meet building demands
One bright light in an otherwise gloomy landscape is
in our own country and when considering also those
the work of the Feasibility Study Panel on Research
areas of the world where housing shortage is almost
and Development for Plastics in Building convened
compatible with the shortage of food. The industry
by a meeting of 18 different building and plastics
needs a technological revolution and will have it
bodies at the Royal Institute of British Architects in
sooner or later, on its own terms or not. In half a
October 1963. This panel comprised representatives
century the motor-car has changed out of all recog-
of the British Plastics Federation, R.I.B.A., and
nition. The technology of that industry has progressed
Ministry of Public Building and Works and published
although the fundamental problems remained. In the
its Interim Report in May 1964. It investigated the
same period the technology of building has changed
problems of information (the sort of service required,
little. Some new materials have been introduced, but
who will organize it and at what cost etc), of fire
the concepts of load-bearing trabeated construction
(testing materials and structures, development of new
for housing have been retained with their irrational
methods and legislation), and weathering (mechanisms
labour and material economics.
involved, accelerated and practical tests, facilities and
costs). It made proposals for commissioning the Economic industrialized building is dependent upon
Association of Building Centres to collect and display standardization, large orders, production-engineering
sales and technical literature, arrange production of techniques and marketing research - truly a fully
elementary pamphlets and undertake a detailed study computerized exercise. The plastics industry recog-
on the provision of technical information and appro- nizes the similarity of this basis with its own production
priate educational courses. The Interim Report also methods and believes it has the materials to satisfy,
made proposals for research into fire performance and with others, the housing programme's needs. We all
weathering. The financial implications of these pro- recognize that plastics materials are eminently suitable
posals are being studied by the British Plastics Feder- for the mass production of a wide range of articles for
ation, but it is pertinent that although the report was consumer and industrial markets. Similarly, we are
published in May 1964, and the 18 bodies were re- aware of the high and increasing labour content of
convened to approve it in October 1964, the Feasibility building costs. If the plastics industry undertakes a
Study Panel has not since met, being unable to proceed detailed study of the builder's site-erection problems, -
until it learns the reactions of the B.P.F. to its interim vis-à-vis handling, ergonomics, weather precautions,
proposals. joining and jointing - as a second stage of its research
and propagation programme, it will begin to recognize
its inevitable contribution. Technically, the con-
3 What is needed struction of large building structures in plastics has
Despite much ill-advised promotion, large quantities already been proved feasible. The problem is to apply
of plastics materials are already being used in building. these materials economically.
It is estimated that 15 per cent of the total United
New materials bring new problems, not least of which
Kingdom tonnage in 1963 was used by the building
are the misuse and the inappropriateness or inadequacy
and civil engineering industries, and that this figure
of design. It has happened before; a new material fails
excluded all materials used in surface coating and
through no intrinsic fault; it becomes stigmatized and
all fillers, plasticizers, reinforcement etc. It is
the designer has the unhappy task of convincing doubt-
comparable to an analysis of the concrete industry in
ful client and frightened builder of its real merits.
terms of cement, excluding aggregates and reinforce-
For example, to design structures in thermoplastics
ment. In terms of finance the 15 per cent represents
it will be necessary to ensure that the stresses lie within
£13·5Μ (ie 1 per cent) of total building raw-materials
the elastic region of the materials at all temperatures
expenditure (£1400M in 1962). It is estimated that this
to which it is likely to be subjected, or to establish, as
represents £35M of fabricated products.
part of the design brief, a definite structural life, to
The tonnage is small compared with the potential enable creep design methods to be used.
BUILDING IN PLASTICS—PLASTICS IN BUILDING : WHAT IS NEEDED 5
The plastics industry has already suffered from sad B.S.I, for consideration. Standards should be inform-
misapplication of its materials, with the result that even ative and unbiased and must not be devalued to meet
today plastics are widely regarded as cheap substitutes, established products (often without any satisfactory
not as materials in their own right. market research). The preparation of drafts for new
plastics components should be commenced im-
The use of plastics in building can only be properly
mediately, where practicable. Premature attempts
developed by a concerted effort by both industries.
Such a drive will only succeed if it is led by architects should be avoided, for standards must be correct.
and engineers with a sound knowledge and under- Codes of practice for design and use of plastics com-
standing of the materials. In recent years we have ponents are urgently required, particularly in the
experienced a variety of symposia with few represent- field of reinforced plastics. A lead from the building
atives from the building industry. Mostly it has been a industry is required here.
case of plastics people talking to plastics people;
a lot of talking with little result, if one discounts the 3.3 Design data
plastics pantiles, weather-boarding, random-stone
Inter alia, the building industry requires full, scientifi-
walling and Adam mouldings. When plastics have
cally reliable and co-ordinated data, preferably ob-
been applied to more worthwhile products it is all too
tained from large-scale tests, on
often in ignorance of the fundamental principles of
building. (i) design strengths, including flexural and tensile
performance ;
It is essential that the Feasibility Study Panel
continues with its task of analysing the requirements (ii) thermal properties, expansion, conductivity ;
to enable the use of plastics in building to be guided by (iii) acoustics, sound attenuation;
the co-ordination and initiation of research. It is also
(iv) behaviour in resisting fire and spread of flame ;
necessary for the architect and engineer to experiment
(v) optical properties;
with these new materials with their knowledge of
requirements and fundamental principles, thereby (vi) weathering and ageing;
helping the plastics industry to concentrate its research (vii) joining and jointing.
alongthe right lines.
As this information becomes available we shall see
At this stage we are able to outline some of the a rapid expansion in the use of plastics in building,
requirements. first semi-structurally, then quickly fully-structurally
with and without assistance from other materials.
3.1 Basic education
It is implicit that a designer must have a thorough An exciting new range of materials awaits the in-
working knowledge of any material before he specifies ventiveness of architects and engineers. There are
it. When he is confronted with a whole new range of many gaps in the supporting data. There are inhibiting
materials, accompanied by a barrage of long chemical regulations to restrict innovations - although we hope
names, the problem of understanding the materials is to see a relaxation of these influences by intelligent
infinitely greater and more bewildering. It is highly re-appraisals in the near future. The builders will be as
unlikely that he will overcome that difficulty by him- apprehensive as ever in their acceptance of new ideas.
self. At the same time it is imperative that the designer Nevertheless, the future of the construction industry in
has an adequate knowledge of the manufacturing this country and the world demands that we explore
techniques peculiar to the new materials, comparable and refine the use of these materials in the next few
to that which he currently possesses of site-con- years. We must not be dispirited by the national
structional techniques for conventional materials. prejudice against the intelligent enthusiast; it is
The information on properties and techniques needs imperative that a start be made on this work now.
to be submitted in various ways to all levels of the build-
ing industry by pamphlets for the man on the site, Bibliography
brochures and digests on development and application Water Committee Report. Sand and Gravel Association. 1951.
research, bulletins with analytical data, text-books, Freeman, C. The Plastics Industry: a comparative study of re-
lecture courses and films. search and innovation - National Institute of Economic and
As more requirements of the building designers Social Research, London - Study sponsored by the Directorate
for Scientific Affairs of the Organisation for Economic Co-
become known it will be necessary to arrange short
operation and Development. November 1963.
courses for members of the plastics industry, to
Building Research and Information Services - Report of a
acquaint them with the building industry and its
Working Party. H.M.S.O. 1964.
problems.
Cmnd. 2279. Building Regulations Advisory Committee. First
Report. H.M.S.O. February 1964.
3.2 Standards and codes of practice
Research and Development for Plastics in Building. Feasibility
We must avoid the tendency for components to become Study Panel - Interim Report. British Plastics Federation.
faits accomplis before drafts are submitted to the May 1964.
7
Paper 2
SfB Dn6
UDC 691.175
The properties of plastics in relation to building structures
H. R. Everard, ACT(BIRM), ARIC, API
Plastics in building materials, justified by their lightness and ease of erection,
their corrosion-resistance and cheap maintenance, and the saving they afford in
the installed cost of components, are still handicapped because some of the problems
arising from their unorthodox mechanical properties have not yet led to acceptable
solutions.
in a recent speech in the House, Lord Todd remarked nately, this multitude of materials is based on a
Ί know full well that barriers to technological relatively small number of types whose general proper-
innovation in industry are not by any means all ties are well known, eg there are many types of
scientific or technological : many of the most important unsaturated polyester resins used in reinforced plastics,
are financial or social barriers. Included among the but to a large extent they have similar properties.
social factors are all the institutional barriers prevent- Plastics are invariably classified into two groups,
ing the full and rapid exploitation of applied science'. thermoplastic and thermosetting, mainly because of
The barriers between the plastics and building differences in chemical structure. Recent develop-
industries are being gradually removed, as is evident ments have led to thermoplastic materials having
by this Conference, but it is still claimed that one of properties approaching those of the thermosetting
the largest obstacles to progress is the lack of inform- types, and it is becoming more convenient to consider
ation on the properties of plastics materials. There plastics from the viewpoint of mechanical properties.
are many cases where plastics materials are not used, TABLE 1 gives some typical properties of the more
owing to lack of sufficient data on their properties common plastics materials arranged in order of
either because this information is not available or compressive strength. The figures given for urea/
because the architect does not know where to obtain formaldehyde are not comparable, as these resins are
it. not manufactured as such and must contain a filler
The plastics industry produces a multitude of such as alpha cellulose.
materials and it is understandable if the building Although there is no specific correlation between
industry is confused by the ever-increasing number, eg compressive and tensile strength, some useful
many with almost unpronounceable names. Fortu- general observations can be made. The lower the
Table 1 Typical properties of unfilled plastics materials
COMPRESSIVE TENSILE TENSILE DEFLECTION COEFFICIENT OF
STRENGTH MODULUS STRENGTH TEMPERATURE THERMAL
X 105 UNDER LOAD EXPANSION
PER DEG F
lb/in2 lb/in2 lb/in2 °F X 10-6
Melamine/formaldehyde 42000 — — 298 —
rea/formaldehyde* 35000 12-5 8300 275 16
Epoxide 20000 3-5 8500 330 30
Poleyster 20000 4-7 9000 270 44
Phenolic 20000 8-8 7500 250 24
Polyacetal 18000 4-1 10000 255 45
Acrylic 15000 4-2 9500 190 39
Polystyrene 13800 4-5 7000 205 39
Polycarbonate 12500 3-5 8700 272 37
Polyvinyl chloride (rigid) 10500 4-7 7000 146 51
Nylon 6/6 9600 3-5 10500 166 44
Polypropylene 7000 1-8 4900 140 40
Polyethylene (medium density) cold flow 0-4 2400 95 78
* containing alpha cellulose
Mr. Everard is with Turner and Newa 11 Limited.
