Table Of ContentPOLYMERIC
MATERIALS
ENCYCLOPEDIA
Editor-in-Chief
JOSEPH C. SALAMONE
Professor Emeritus
University of Massachusetts, Lowell
VOLUME
9
P
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ISBN 13: 978-0-8493-2470-3 (hbk) (Vol. 9)
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Library of Congress Card Number 96-12181
Library of Congress Cataloging-in-Publication Data
Polymeric materials encyclopedia / editor-in-chief Joseph C. Salamone.
p. cm.
Includes bibliographical references and index.
ISBN 0-8493-2470-X
1. Plastics-Encyclopedia. 2. Polymers-Encyclopedia
I. Salamone, Joseph C., 1939-
TP1110.P65 1996
668.9'03-dc20 96-12181
CIP
TABLE OF CONTENTS
P 6517
Poly(Pkenylene Sulfide) and Copolymers 6517
Poly(P-Phenylene Sulfone) 6525
Poly(Phenylene Vinylene)s 6532
Poly(P-Phenylene Vinylene)s 6537
Polyphenylenes 6549
Polyphosphazene Block Copolymers 6556
Polyphosphazenes 6563
Polyphosphonates and Polyphosphates 6569
Polyphthalamides 6573
Polypropylene 6578
Polypropylene 6588
Peroxide-Promoted Degradation of Polypropylene 6589
Process Control for Polypropylene Degradation 6591
Polypropylene 6594
Polypropylene 6602
Polypropylene, Atactic 6609
Polypropylene Blends and Composites 6615
Poly(Propylene Carbonate) 6623
Polypropylene, Hemiisotactic 6630
Polypropylene, Isotactic 6637
Polypropylene, Isotactic 6649
Poly(Propylene Oxide) 6656
Poly(2,6-Pyridinediylvinylene) 6662
Polypyrrole 6670
Polypyrroles 6678
Polyradicals 6686
Polyrotaxanes 6695
Polysaccharide-Polysaccharide Interactions 6704
Polysaccharides, Synthetic 6713
Polysaccharides, Synthetic 6717
Polysilanes 6722
Polysilanes 6734
Polysilazanes 6747
Polysilylpropynes 6758
Polysoaps 6763
Polystyrene 6768
Poly(Styrene-Co-N-Alkylmaleimide)s 6774
Polystyrene and Derivatives, Photolysis 6786
Polystyrene, High Impact 6799
Polystyrene Manufacture 6806
Polystyrene, Rubber Toughened 6814
Polystyrene, Stereoregular 6820
Polystyrene, Syndiotactic 6828
Polystyrene, Syndiotactic 6838
Polysulfides 6844
Polysulfides 6852
Polysulfides 6856
Poly[N,N'-(Sulfo-P-Phenylene) Terephthalamide] 6863
Polysulfones 6866
Polyterpene Resins 6878
Polytetrafluoroethylene 6884
Polytetrafluoroethylene 6891
Poly(2,5-Thienylene Vinylene) and Derivatives 6898
Poly(Thioether Ketone and Sulfone)s 6904
Polythiophenes 6911
Polythiophenes 6918
Polythiophenes, Substituted 6923
Poly(1,2,4-Triazole)s 6931
Polyureas 6937
Polyurethane Catalysis 6940
Polyurethane Catalysts 6947
Polyurethane Elastomers, Segmented 6957
Polyurethane Ionomers 6968
Polyurethanes 6979
Polyurethanes, Blocked Copolymer 6986
Poly(Vinyl Alcohol) 6991
Poly(Vinyl Alcohol) 6998
Poly(Vinyl Alcohol) Fiber 7003
Poly(Vinyl Alcohol) Fibers 7010
Poly (Vinyl Alcohol) Iodine Interactions 7014
Poly(Vinyl Alcohol)-Ion Complex Gels 7020
PVA-Borate Complexes 7021
PVA-Vanadate Gels 7023
Poly(Vinyl Chloride) 7026
Poly(Vinyl Chloride) 7038
Poly(Vinyl Chloride) 7042
Poly(Vinyl Chloride) 7048
Poly(Vinyl Chloride), Rigid 7064
Poly(Vinyl Chloride), Soft 7079
Poly(Vinyl Ketal)s 7088
Polyvinylamine 7095
Polyvinylamine 7103
PoLy(N-Vinylcarbazole) 7107
Poly(Vinylidene Fluoride) 7115
Poly(Vinylidene Fluoride) 7123
Poly(Vinylidene Fluoride) Phases and Morphology 7128
Poly(Vinylpyridinium Salt)s 7138
Poly(N-Vinyl-2-Pyrrolidone) Interactions 7154
Polyvinyltetrazoles 7163
Poly(P-Xylylene)s 7171
Poly(P-Xylylene)s, Coatings and Films 7180
Polyzwitterions 7189
Powder Coatings 7201
Preceramic Polymers 7215
Precipitation Polymerization 7228
Precipitation Polymerization 7237
Printing Inks 7239
[1.1.1] Propellanes 7250
Propylene Polymerization 7256
Protein-Based Polymeric Materials 7263
Protein-Based Polymer Synthesis 7264
Pseudo-Poly(Amino Acid)s (overview) 7279
Pyroelectricity 7290
commercial material.2,3 As will be seen later, the reason for
the low melting point of PPS prepared by this oxidative
process is actually ortho substitution in the final product, not
lack of molecular weight. Additionally, a report in the patent
literature11 described a melt preparation of PPS from
4-chlorophenyltrimethylsilyl thioether, which eliminates tri-
methylsilyl chloride during the reaction, but the reported
yield and melting point were low. Details were too sparse
for drawing sound conclusions about the process, however.
POLY(PKENYLENE SULFIDE) AND Recently Fahey and Ash12 have published some excellent
COPOLYMERS summary work on the mechanistic aspects of the commer-
cial process invented by Edmonds and Hill.2 Of particular
(Melt Preparation via a New Process)
note in the work of Fahey and Ash, the reaction rate of the
David R. Fagerburg first chlorine versus that of the second one in p-dic-
Eastman Chemical Company hlorobenzene gave a ratio of 1:7, i.e., the SNAr substitution
reaction by a sulfur species is 7 times slower when another
chlorine is present on the ring than when a thioether is the
Poly(phenylene sulfide) (PPS) has found numerous engi- substituent.
neering plastic and some fiber and film applications owing All of these approaches, save the silyl ether one, have in
to its excellent combination of chemical resistance and common the generation of large amounts of salt residue for
thermal properties. McCallum,1 first prepared PPS via melt each kilogram of product. In the Edmonds-Hill process this
reaction of p-dichlorobenzene and sulfur in the presence of amounts to 1.3 kg of NaCl per kilogram of PPS. Complete
sodium carbonate, but the product contained considerable removal of salt from a hydrophobic polymer is, of course,
branching along with contaminating salts. In the commer- difficult. In addition, process effluents must be somewhat
cial process patented by Edmonds and Hill,2 PPS is made problematic to deal with in the long term. Another industrial
via solution reaction of p-dichlorobenzene with alkali metal type of consideration for these processes is that none of
sulfide. The product, however, suffered from low molecular them are easily adaptable to a continuous process but are
weight so that air “curing” was needed to obtain useful rather done in a batch process with its attendant variability.
physical properties.3 The branching thus introduced is From a polymer chemistry standpoint one must also
problematic in several potential applications such as film realize that the Edmonds-Hill process is nonequilibrium
and fiber, owing to melt elasticity; in addition, this branch- chain growth, as are the other approaches discussed, and so
ing no doubt contributes to the brittleness of the material the molecular weight distribution can be quite broad and
that is seen in certain molding applications. Some recent will not equilibrate to some equilibrium value if two batches
advances in this solution process involve the use of an alkali of differing distributions are mixed in the melt. Also
metal carboxylate to obtain higher molecular weights but problematic is that the rate of reaction of greater-than-
retain the problem of removal of ionic salts, which can difunctional species in the mixture will not only alter the
interfere with electrical properties. Several other syntheses breadth of the distribution but also may be unevenly
have been reported but not commercialized. Lenz et al.4 distributed in the polymer chains as well. This plus the batch
prepared PPS via condensation of p-halothiophenoxy salts, nature of the process leads to wide variability from batch to
and Port and Still5 polymerized the copper salt of batch unless super precise control is maintained. Typical
p-bromothiophenol. These products also suffered from weight average/number-average molecular weight (Mw:Mn)
metal salt contamination as well as low molecular weights. ratios are reported13 to be on the order of 6-18.
Lovell and Still6 undertook polymerization of bis(^~ The increased mechanistic knowledge from Fahey and
bromophenyl) disulfide but found only modest molecular Ash12 (and probably others unpublished) has allowed com-
weights and then only when a stoichiometric amount of mercially produced PPS to now be made at high enough
copper was present in the reaction mixture. Recently, molecular weight to avoid the air curing step for several
Tsuchida et al. 7-10 prepared PPS via an oxidative polymer- grades of material by, among other things, addition of an
ization method that eliminated the metal salt residues, but equimolar quantity of a carboxylate salt such as sodium
the melting points were low. Even where the molecular benzoate to the reaction mixture. Although this is reputed to
weight was reported to be high, the melting points were still actually make cleanup of the PPS produced somewhat
on the order of 50 °C lower than that expected for easier, the problem of complete removal and also process
0-8493-2470-X/96/$0.00+$.50
© 1996 by CRC Press, Inc. 6517
6518 POLY(PHENYLENE SULFIDE) AND COPOLYMERS (Melt Preparation via a New Process)
o
I +s 1
air bleed
effluent and solvent recovery considerations still must p-diiodobenzene. This process was discovered several years
remain as formidable problems. ago by Rule et al.19 and consists of conducting vapor—for
We have recently reported14-16 a new melt-phase poly- example, benzene in this case—over a heated zeolite
merization process for the preparation of PPS involving catalyst in the presence of iodine and air. The net equation
reaction of p-diiodobenzene and sulfur (Equation 1) and is shown in Equation 2.
some of the characteristics of the resultant polymer. The
model compound reaction of this method also has been
recently reported.17 This new melt process has several
- -J;. >
unique and unusual characteristics. The process can be
i-Q +H2°2
carried out entirely in the melt using, for example, a final catalyst
reaction temperature of 300 °C (initial reaction temperature
is usually 230 °C). However, in an unusual twist for PPS
chemistry, alternatively the polymer reaction can be stopped The reaction mixture contains all three possible diiodo
at a prepolymer stage by use of a lower final reaction isomers, with the para isomer predominating by far.
temperature, typically 250 °C, much as one would expect to p-Diiodobenzene is the only crystalline product of the
be able to do in the technology normally practiced for reaction and is easily separated from the cooled reaction
production of poly (ethylene terephthalate). This prepolymer mixture as white crystals. It is typically produced at about
can then be solid state polymerized to its final, high 70% specificity. The unwanted side products o- and
molecular weight (e.g., the patent of Fagerburg and m-diiodobenzene are easily recycled to the process via a
Watkins18) without an attendant increase in branching. disproportionation reaction with excess benzene over an-
Elemental iodine is the reaction by-product in either the other catalyst to produce iodobenzene. It is obvious that the
melt-phase-only or the melt-phase—solid-phase reaction iodobenzene is then easily recycled to the oxyiodination
sequence, and no ionic by-products are formed. To verify process.
evolution of iodine in the polymerization reaction in the Not surprisingly, it was discovered that the oxyiodination
solid-state, off-gas from the solid state polymerization was process could be used to prepare diiodo aromatic com-
collected in a dry-ice-cooled trap and analyzed by GC/MS pounds from a number of aromatic systems such as biphe-
(accurate mass), which showed the evolved material to be I2 nyl, naphthalene, and diphenyl ether. This leads to a
with only a trace amount of p-diiodobenzene. The p- potentially large number of possible poly(arylene sulfide)
diiodobenzene was most certainly unreacted monomer that polymers and copolymers.
was present in the prepolymer and not itself a reaction As previously reported,1516 the infrared(IR) spectrum of
product. PPS from this process was essentially identical with that of
In addition, unlike other PPS processes, careful control of commercial material (Ryton™; Phillips) both in peaks and
reactant stoichiometry is not nearly as critical to obtaining in ratios of strong and medium peaks, especially in the
high molecular weight. Instead, molecular weight can be all-important fingerprint region (Figure 1). Of course, the
controlled by the time-temperature sequence along with presence of disulfide linkages in the polymer cannot be
reactant stoichiometry. As is also evident from the process verified by the IR spectrum, because the absorbance for
in Equation 1 above, by-product iodine can be recovered disulfide stretching vibrations is IR inactive. Therefore,
and used in the synthesis of more monomer (Equation 2), quantitation of disulfide content had to be done by elemental
thus closing the reaction loop. Thus, our new process analysis.15 In this process it is essential to minimize the melt
effectively makes PPS from benzene and sulfur, basic level of iodine present as is leads to branching in the final
chemicals. product polymer. This can be understood from a blending of
Before continuing further with discussion of some par- our published results in two separate studies.20,21 Branching
ticulars of this novel process, we wish to first briefly effects on thermal and rheological properties were evaluated
examine the oxyiodination reaction used to produce the by experiments where triiodobenzene and Zrzs(p-bromo-
POLY(PHENYLENE SULFIDE) AND COPOLYMERS (Melt Preparation via a New Process) 6519
Wavenumber (cm4)
FIGURE 1. IR spectra of melt process PPS and Ryton P4 PPS. Source: Reference 16. With permission.
phenyl)amine were used as branching agents.20 The former branched material as seen in the decrease and eventual
agent failed to give consistent results, probably partly as a disappearance of the melting transition, equally dramatic
result of lowered reactivity of the third iodine on the ring, in changes in the crystallization upon cooling or heating, and
analogy to the lowered reactivity of the second chlorine in the associated melt rheology. This experience of needing
relative to the first in p-dichlorobenzene. In our own as yet to minimize the melt iodine level to eliminate branching
unpublished experiments, the difference in reaction rate carries directly over to our PPS synthesis, as expected.
between the first and second iodines in p-diiodobenzene was Our unique route for PPS synthesis allowed us to inves-
in a 1:4 ratio (D. E. VanSickle, unpublished work), very tigate several interesting aspects of PPS morphology, only
similar to the 1:7 ratio seen by Fahey and Ash12 for one of which is mentioned here. Because of the presence of
p-dichlorobenzene. This implies perhaps another 4-fold or the heavy iodo end groups in the PPS chains made by this
more reduction in rate of attack for the first iodine in a synthetic route, it was possible to use elemental analysis to
triiodo species, making the first iodine of the triiodobenzene measure the degree of polymerization (DP) with reasonable
substantially less reactive than the first iodine in accuracy. By using this analysis for a series of oligomers, it
p-diiodobenzene. Thus, the triiodobenzene would most was confirmed by hot-stage optical microscopy22 that
certainly tend to be incorporated toward the end of the spherulitic growth was observed for samples with a DP
reaction rather than on a statistical basis throughout the >38, whereas for samples with a DP of 30 the organization
reaction that could more readily be expected of the amine. showed lamellar sheafs. Chain-extended crystal structures
In a second paper21 detailing reaction condition results for were observed at DP <30. The lamellar thickness of the
the model compound p-iodophenyl disulfide, it was appar- chain-folded crystallites was determined by small-angle
ent that an increase in the level of melt iodine produced X-ray scattering (SAXS) data to be 10 monomer units in
