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Файл:Plastics technology. Часть 1. Учебное пособие.pdf
Министерство образования и науки России
Федеральное государственное бюджетное образовательное
учреждение высшего профессионального образования
«Казанский национальный исследовательский
технологический университет»
S. Yu. Sofina
PLASTICS TECHNOLOGY
Tutorial
Part 1
Казань
Издательство КНИТУ
2012
УДК 678.5(075)
ББК 35.71.я7
Софьина С.Ю.
Plastics technology : учебное пособие. Ч. 1 / С.Ю. Софьина; М-во
образ. и науки России, Казан. нац. исслед. технол. ун-т. – Казань : Изд-во
КНИТУ, 2012. – 212 с.
ISBN 978-5-7882-1295-1
ISBN 978-5-7882-1296-8 (ч. 1)
Tutorial is conformed to a State education standard in the direction
240100 – “Chemical technology” and the program “Polymer science and
technology”.
The tutorial describes plastics based on polymers obtained by
polymerization, polycondensation and on chemically modified polymers
(preparation of monomer, polymerization or polycondensation, properties,
processing and applications).
The tutorial is designed for the masters studying the disciplines
“Chemistry and physics of macromolecular compounds”, “General chemical
technology of polymers”, “Pla stics technology”.
Prepared by the Department of Plastics technology.
Учебное пособие соответствует Государственному образовательному
стандарту по направлению 240100 – «Химическая технология» и программе
«Наука о полимерах и технология».
В пособии описаны пластмассы на основе полимеров, получаемых
путем полимеризации, поликонденсации, и химически модифицированные
полимеры (подготовка мономера, полимеризация или поликонденсация,
свойства, переработка и применение).
Предназначено для магистров, изучающих дисциплины «Химия и
физика высокомолекулярных соединений», «Общая химическая технология
полимеров», «Технология пластмасс».
Подготовлено на кафедре технологии пластических масс.
Печатается по решению редакционно-издательского совета Казанского национального исследовательского технологического университета
Рецензенты: проф. Л.А. Абдрахманова
проф. Ю.А. Тунакова
ISBN 978-5-7882-1296-8 (ч. 1) © Софьина, С.Ю., 2012
ISBN 978-5-7882-1295-1 © Казанский национальный исследовательский
технологический университет, 2012
3
Сontents
Preface .......................................................................................................... 5
1 GENERAL PATTERNS OF POLYMERIZATION REACTIONS .......... 6
1.1 Addition Polymerization ..................................................................... 6
1.1.1 Ionic Polymerization .................................................................. 10
1.1.2 Ziegler-Natta and Metallocene Polymerization .......................... 14
2 PLASTICS BASED ON POLYMERS
OBTAINED BY POLYMERIZATION ..................................................... 16
2.1 Polymers of Unsaturated Aliphatic Hydrocarbons
and their Derivatives ............................................................................... 16
2.1.1 Polyethylene ............................................................................... 16
2.1.2 Polypropylene ............................................................................. 40
2.1.3 Polyisobutylene .......................................................................... 56
2.1.4 Copolymers Containing Ethylene............................................... 57
2.2 Polymers of Unsaturated Aromatic Hydrocarbons ........................... 60
2.2.1 Polystyrene ................................................................................. 60
2.2.2 Styrene-acrylonitrile Copolymers .............................................. 81
2.2.3 Miscellaneous Rubber-modified Styrene-acrylonitrile
and Related Copolymers ..................................................................... 82
2.2.4 Styrene-maleic Anhydride Copolymers ..................................... 84
2.2.5 Butadiene-styrene Block Copolymers ........................................ 86
2.3 Polymers of Halogenated Unsaturated Hydrocarbons ...................... 87
2.3.1 Poly(vinyl chloride) .................................................................... 87
2.3.2 Crystalline PVC ........................................................................ 112
2.3.3 Graft Polymers Based on PVC ................................................. 112
2.3.4 Vinyl Chloride-Propylene Copolymers .................................... 113
2.3.5 Vinyl Chloride-N-cyclohexylmaleimide Copolymers.............. 113
2.3.6 Vinylidene Chloride Polymers and Copolymers ...................... 113
2.3.7 Vinylidene Chloride-Acrylonitrile Copolymers ....................... 116
2.3.8 Polytetrafluoroethylene ............................................................ 117
2.3.9 Poly(vinylidene fluoride) ......................................................... 123
2.4 Polymers Derivatives of Acrylic and Methacrylic Acid ................. 124
2.4.1 Poly(methyl methacrylate) ....................................................... 126
2.4.2 Methyl Methacrylate Polymers
with Enhanced Impact Resistance and Softening Point .................... 142
2.4.3 Acrylic Adhesives .................................................................... 144
2.4.4 Hydrophilic Polymers............................................................... 145
4
2.4.5 Polyacrylonitrile ....................................................................... 145
2.4.6 Polyacrylamide ......................................................................... 146
2.5 Polymers of Complex and Simple Vinyl Ethers ............................. 147
2.5.1 Poly(vinyl acetate) and its Derivatives ..................................... 147
2.5.2 Poly(vinyl ethers) ..................................................................... 151
2.6 Polymers Based on Derivatives of Ethylene
with Complex Substituents ................................................................... 152
2.6.1 Coumarone-Indene Resins ....................................................... 152
2.6.2 Poly(vinyl Carbazole) ............................................................... 154
2.6.3 Poly(vinyl Pyrrolidone) ............................................................ 156
2.7 Polyethers ........................................................................................ 158
2.7.1 Acetal Resins ............................................................................ 160
2.7.2 Miscellaneous Aldehyde Polymers .......................................... 172
2.7.3 Polyethers from Glycols and Alkylene Oxides ........................ 173
2.7.4 Oxetane Polymers..................................................................... 176
2.8 Polyurethanes and Polyisocyanurates ............................................. 178
2.8.1 Fibres and Crystalline moulding Compounds .......................... 179
2.8.2 Rubbers ..................................................................................... 181
2.8.3 Flexible Foams ......................................................................... 189
2.8.4 Rigid and Semi-rigid Foams ..................................................... 200
2.8.5 Coatings and Adhesives ........................................................... 205
2.8.6 Polyisocyanurates ..................................................................... 206
2.8.7 Polycarbodi-imide Resins ......................................................... 208
2.8.8 Polyurethane-Acrylic Blends ................................................... 209
2.8.9 Miscellaneous Isocyanate-based Mat eria ls .............................. 209
5
Preface
One of the fastest changing fields today is the field of plastics as
new polymers are synthesized, new uses are found, and existing processes
and products are modified and improved for ecological needs, better
economics, and better values.
What makes plastics the most versatile of all mat erials is the ease
with which they can be given any desired shape and form. Molding and
fabrication processes, however, vary depending on the type of polymers to
be processed and the end products to be made.
In this tutorial, plastics have been broadly divided into three
categories, namely, plastics based on polymers obtained by polymerization,
plastics based on polymers obtained by polycondensation and plastics
based on chemically modified polymers. The first group of polymers is
those which are produced on very large, large, and relatively large scales,
including the so-called engineering polymers that possess superior
mechanical properties for engineering applications. Besides a handful of
high-volume polymers like polyethylene, polypropylene, polystyrene,
poly(vinyl chloride), polyethers, etc., which are very visible in everyday
life, there are hundreds of other polymers, polymer derivatives, and
polymeric combinations that play special and often critical roles in diverse
fields of human activities.
As we live in a plastics age, the diverse fields of plastics
technology are also undergoing rapid changes both qualitatively and
quantitatively with many newer applications of common polymers and
specialty polymers coming to light. While there are continuous
improvements in the established uses of polymers, new uses are being
developed in such diverse areas as the automotive and aerospace industries,
packaging, agriculture, horticulture, domestic and sports appliances, office
equipment, communication, electronics and electrical technology, and
biomedical applications.
6
1 GENERAL PATTERNS OF POLYMERIZATION REACTIONS
C O O C
O O
CO
2
+
+
CO
2
Free Radicals
CN
C
CH
3
N
N C CN
CH
3
CH
3
CH
3
2CN
C
CH
3
CH
3
+
N
2
I +
CH
2
CH
X
I
CH
2
CH
X
1.1 Addition Polymerization
Addition polymerization is effected by the activation of the double
bond of a vinyl monomer, thus enabling it to link up to other molecules.
This reaction occurs in the form of a chain addition process with initiation,
propagation and termination steps.
The initiation stage may be activated by free-radical or ionic
systems. In the following example a free-radical system will be discussed.
In this case a material which can be made to decompose into free radicals
on warming, or in the presence of a promoter or by irradiation with
ultraviolet light, is added to the monomer and radicals are formed. Two
examples of such materials are benzoyl peroxide and azodi-isobutyronitrile,
which decompose as indicated in Figure 1.
Figure 1
Such free-radical formation may be generally indicated as
I—I → 2I—
The rate of formation of radicals will depend on a number of
features, including the concentration of initiator, temperature and the
presence of other agents. Since subsequent stages of polymer growth occur
almost instantaneously it is the relative slowness of this stage which causes
the overall conversion times in most polymerizations to be at least 30
minutes and sometimes much longer.
The radicals formed may then react with a monomer molecule by
addition, producing another radical.
This radical then reacts with a further molecule of monomer,
7
generating yet another free radical of the same order of reactivity.
X
CH
CH
2
I
+
CH
CH
2
X
X
CH
CH
2
I
X
CH
CH
2
CH
X
CH
2
+
CH
2
CH
X
CH
X
CH
X
CH
2
CH
2
X
CH
CH
2
+
CH
2
CH
X
CH
CH
2
+
X
CH
2
CH
2
X
I
+
CH I
X
CH
2
X
CH
CH
2
X
CH Y
CH
2
X
CH
CH
2
+
RY
+
R
CH
X
CH
CH
2
X
+
X
CH
CH
2
+
CH
2
CH
2
C
X
+
X
CH
CH
2
+
HO
OH
CH
2
CH
2
X
OH
O
Stable
This reaction may then repeat itself many times so that several
thousand monomer units are joined together in a time of the order of 1
second, leading to a long chain free radical. This is the propagation or
growth stage. Termination may be effected in a number of ways, including:
(1) Mutual combination of two growing radicals
(2) Disproportionation between growing radicals
(3) Reaction with an initiator radical
(4) Chain transfer with a modifier
(This reaction terminates growth of a chain but there is no net loss
in the radical concentration and it does not therefore affect the velocity of
the reaction.)
(5) Chain transfer with monomer.
(6) Reaction with a molecule to form a stable free radical, e.g.
hydroquinone.
Termination by mechanisms (1) and (2) above are most common,
whilst mechanisms (4) and (6) are of particular technological importance.
Although it is generally possible to reduce molecular weight to some extent
by increasing the polymerization temperature, there is a limit to the amount
that this can be done. In addition, raising the polymerization temperature
8
often causes undesirable side reactions to occur. On the other hand, by
a
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incorporating small quantities of a modifier a method of regulating the
amount of chain growth is employed which does not interfere with the rate
of the reaction. Such materials are also spoken of as chain transfer agents
and regulators, and include chlorinated materials such as carbon
tetrachloride and trichlorethylene and mercaptans such as dodecyl
mercaptan.
In the case of mechanism (6) there are materials available which
completely prevent chain growth by reacting preferentially with free
radicals formed to produce a stable product. These materials are known as
inhibitors and include quinone, hydroquinone and tertiary butylcatechol.
These materials are of particular value in preventing the premature
polymerization of monomer whilst in storage, or even during manufacture.
It may be noted here that it is frequently possible to polymeri ze two
monomers together so that residues from both monomers occur together in
the same polymer chain. In addition polymerization this normally occurs in
a somewhat random fashion and the product is known as a binary
copolymer* (* Binary copolymers are commonly referred to simply as
copolymers.). It is possible to copolymerize more than two monomers
together and in the case of three monomers the product is referred to as a
ternary copolymer or terpolymer. The term homopolymer is sometimes
used to refer to a polymer made from a single monomer.
Other copolymer forms are alternating copolymers, block
copolymers and graft polymers.
Figure 2 illustrates some possible ways in which two monome rs A
and В can be combined together in one chain.
solvent, in suspension or emulsion. Bulk polymerization is, in theory,
comparatively straightforward and will give products of as good a clarity
and electrical insulation characteristics as can be expected of a given
material. However, because polymerization reactions are exothermic and
because of the very low thermal conductivity of polymers there are very
Figure 2 – (a) Random copolymer, (b) alternating copolymer,
(c) block copolymer, (d) graft copolymer
Polymerization may be carried out in bulk, in solution in a suitable
9
real dangers of the reactants overheating and the reaction getting out of
control.
Reactions in bulk are used commercially but careful control of
temperature is required. Polymerization in a suitable solvent will dilute the
concentration of reacting material and this together with the capability for
convective movement or stirring of the reactant reduces exotherm
problems. There is now, however, the necessity to remove solvent and this
leads to problems of solvent recovery. Fire and toxicity hazards may also
be increased.
An alternative approach to solving the exotherm problem is to
polymerize in suspension. In this case the monomer is vigorously stirred in
water to form tiny droplets. To prevent these droplets from cohering at the
stage when the droplet is a sticky mixture of polymer and monomer,
suspension or dispersion agents such as talc, poly(vinyl alcohol) or gelatine
are added to provide a protective coating for each droplet. Polymerization
occurs within each droplet, providing a monomer-soluble initiator is
employed, and the polymer is produced as small beads reasonably free
from contaminants.
The reaction is considerably modified if the so-called emulsion
polymerization technique is used. In this process the reaction mixture
contains about 5% soap and a water-soluble initiator system. The monomer,
water, initiator, soap and other ingredients are stirred in the reaction vessel.
The monomer forms into droplets which are emulsified by some of the soap
molecules. Excess soap aggregates into micelles, of about 100 molecules,
in which the polar ends of the soap molecules are turned outwards towards
the water whilst the non-polar hydrocarbon ends are turned inwards (Figure
3).
Figure 3 – Structures present during emulsion polymerization
10
Monomer molecules, which have a low but finite solubility in
water, diffuse through the water and drift into the soap micelles and swell
them. The initiator decomposes into free radicals which also find their way
into the micelles and activate polymerization of a chain within the micelle.
Chain growth proceeds until a second radical enters the micelle and starts
the growth of a second chain. From kinetic considerations it can be shown
that two growing radicals can survive in the same micelle for a few
thousandths of a second only before mutual termination occurs. The
micelles then remain inactive until a third radical enters the micelle,
initiating growth of another chain which continues until a fourth radical
comes into the micelle. It is thus seen that statistically the micelle is active
for half the time, and as a corollary, at any one time half the micelles
contain growing chains.
As reaction proceeds the mi celles become swollen with monomer
and polymer and they eject polymer particles. These particles which are
stabilised with soap molecules taken from the micelles become the loci of
further polymerization, absorbing and being swollen by monomer
molecules.
The final polymerized product is formed in particles much smaller
(50-500 nm) than produced with suspension polymerization. Emulsion
polymerization can lead to rapid production of high molecular weight
polymers but the unavoidable occlusion of large quantities of soap
adversely affects the electrical insulation properties and the clarity of the
polymer.
1.1.1 Ionic Polyme r iz a tio n
A number of important addition polymers are produced by ionic
mechanisms. Although the process involves initiation, propagation and
termination stages the growing unit is an ion rather than a radical.
The electron distribution around the carbon atom (marked with an
asterisk in Figure 4) of a growing chain may take a number of forms. In
Figure 4 (a) there is an unshared electron and it acts as a free radical. Figure
4 (b) i s a positively charged carbonium ion, unstable as it lacks a shared
pair of electrons and Figure 4 (c) is a negatively charged carbanion,
unstable as there exists an unshared electron pair.