COMPLIMENTARY COPY
Vol. 4, No. 3
PEL PLASTICS UPDATE
By Mort Wallach
http://www.pelassociates.com/
Jan-Feb 1997
ISSN 1094-656X
RECENT PROGRESS IN POLYMER/PLASTICS TECHNOLOGY
Smart/Functional Polymers-Dendritic and hyperbranched polymers are finding
important applications including drug delivery systems, signal amplification, and
molecular-scale sensors, resulting from their unique and varied architecture.

Prof. Frechet and coworkers at Cornell have recently reported new dendritic
structures including a dendritic ‘hybrid star’ which changes its micellar
conformation with the polarity of the solvent medium. The star is formed by four
hydrophilic poly(ethylene glycol) chains terminated by hydrophobic dendritic
wedges (based on 3,5-dihydroxy benzyl alcohol) emanating from a central carbon
atom. Possible applications of this technology include controlled release drug
delivery systems. (J. Am. Chem. Soc., 118, 3785, 1996) The Frechet team also
disclosed an assembly of several polyether dendrimers around a central rare earth
cation. Because of its dendritic overcoat, each cation is isolated from all the others
so that they cannot quench each other when excited by light of the appropriate
wavelength. This technology is targeted for application in signal amplification for
fiber-optic communication systems, e.g., telephony. These researchers are also
developing molecular-scale sensors by adsorbing a functionalized dendrimer to a
surface, followed by molecular interaction with chemical species in solution
designed to trigger a change in properties like surface conductivity or refractive
index.

Hyperbranched and dendritic polymers are also being investigated as chemically
sensitive interfaces in sensing applications by R. Crooks and coworkers at Texas A
& M. The idea is to combine the best features of self-assembled monolayers (e.g.,
easily made with direct analyte attachment) and polymer thin films (high
sensitivity) to make biocompatible sensors, e.g., a restricted access material like a
molecular filter. (J. Am. Chem. Soc., 118, 3773, 1996). Another application is
corrosion inhibiting coatings of hyperbranched films grown in layers, where each
layer can block passage of a different corrosive agent. Crooks has also made thin
film sensors using classical globular poly(amido amine) dendrimers as building
blocks (commercially available from Dendritech) (J. Am. Chem. Soc., 118, 3988,
1996). The real power of dendrimers as chemically sensitive interfaces is in sensor
arrays that are responsive to different classes of analytes. This is being pursued by
Crooks in collaboration with A. Ricco at Sandia National Laboratories. Other
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Jan-Feb 1997
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dendrimer technologies being developed include: the ‘dendritic box guest/host
system’ with potential for enzymatic or photochemical delivery (E. Meijer,
Eindhoven U.of Tech.), and self-assembled dendrimers as potential building blocks
for nanostructured materials, new liquid crystal structures, and viral coatings (S.
Zimmerman, U. of Illinois). Clearly, dendrimers have tremendous practical
potential and much flexibility in the types of structures that can be made. The
chemistry can be complex but research in this area should pay off in both
fundamental and practically useful knowledge. Meanwhile, these investigators are
opening up a lot of possibilities.(R. Dagani, C&EN, June 3, 1996, p. 30).
Biodegradable Polymers-The semi-annual meeting at The Biodegradable Polymer
Research Center (BPRC) was held at UMass Lowell on April 22, 1996. The conference
was highlighted by presentations from center Directors-Profs. R. Gross and S. McCarthyand Members.

Prof. Gross discussed Center research programs in various areas including: (1)
lactone/ ethylene oxide block copolymers involving: ring opening polymerization,
tailoring block length, catalyst effects on MW, stereoregularity, and sequence
distribution, (2) block copolymers of polyhydroxybutyrate (PHB)/polycaprolactone
(PCL), (3) polylactic acid-stereochemistry and morphology, and how crystallinity
affects enzyme susceptibility, (4) polysaccharide-g-polyesters and their applications
as interfacial materials for blends, tie layers, and films, (5) starch modification, e.g.,
acylation, (6) enzyme catalysts for ring opening reaction where advantages include:
enantioselectivity, versatility, and increased efficiency in nonaqueous media, (7)
immobilized enzymes, e.g., using coating techniques, (8) biosurfactants and
bioemulsions tailored for applications in the oil and cosmetics industry, and (9)
PEG modulated fermentation of polyhydroxy alkanoates with application to control
the polymerization of PHB. Clearly, this is broad and innovative array of
approaches to new and improved biodegradable polymer technologies.

Prof. McCarthy outlined Center work on: the effect of processing on
biodegradability, ways to improve properties by blending, biodegradable
plasticizers (e.g., citrate esters), use of reactive processing, composites with low
cost biodegradable fillers such as starch and wood flour, paper coatings, aging
effects on polylactic acid, and cellulose acetate plasticization to improve
processability. Other polymers being studied in processing/blending/ composite
areas include: PCL, PHB, PEO, and polysuccinate esters. The Center also has
programs on testing and medical applications of biodegradable polymers.

Papers presented by Center members include: ‘Biodegradable Materials from
Eastman Chemicals’ (C. Buchanan), ‘Biodegradable Adhesives from PHA’s for 3M
Applications’ (D. Rutherford), ‘Modifications of Poly Lactic Acid’ (M. Hartmann,
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Cargill), ‘Synthesis and Properties of New Biodegradable Polyesters Derived from
the Reaction of Diglycidyl Ethers and Aliphatic Diacids’ (M. Mang, Dow),
‘Biodegradable Plasticizers’ (E. Frappier, Morflex, Inc.), ‘Activities on
Biodegradable Polymers’ (G. Schornick, BASF), ‘Properties and Biodegradability
of Starch Acetate’ (D. Roesser, National Starch & Chemical).
Catalysis-New olefin based crystalline/amorphous multi-polymers made via reactor
Ziegler-Natta catalysis can compete with engineering resins in key markets.

Montell’s new terpolymers of PP and SMA provide elevated temperature
performance, and copolymers of PP and acrylics deliver improved weatherability
with applications in automotive, appliance and consumer products. These
materials-Hivalloy T and W, respectively-add to the G series of reactor based
styrene-propylene copolymers that offer impact-stiffness balances surpassing that of
impact polypropylene. A market development facility (10 million lbs/yr is just
coming on stream and a world-scale 100 million lb/yr unit is scheduled for
operation in 1999). The technology involves control of the size, shape, and
porosity of Ziegler-Natta catalyst particles to make a semi-porous polymer instead
of conventional solid structures. Reactor granules then allow varied comonomers
to be copolymerized in the particle. In effect the particles are mini-reactors. In this
way, submicron scale, homogeneous, highly controlled, interpenetrating
copolymers are formed. Alternative competitive approaches using metallocene
technology such as Dow’s ethylene/styrene interpolymer is another way to use low
cost olefin monomers as building blocks. These materials could compete favorably
with nylon 66, PC, PC/ABS, and other engineering thermoplastics.Other routes to
such polymer systems of semi-crystalline (olefin type) and amorphous (non-olefin
type) alloys-including reactive processing and compatibilization-have possible
caveats including: compatibilizer availability, addition of a heat history, possible
instability of PP functionalization, and compounding costs. While the market place
and durability of these technical innovations decide on which approach succeeds,
the potential is significant with a structural molding market of 9.2 billion lbs
worldwide (3.6 billion lbs U.S.) of mostly amorphous resin selling at $2-5/lb
whereas these SP alloys cost about $1.70/lb and have lower density (0.950 g/cc)
than most of the competition.(R. Leaversuch, Mod. Plas., 73, 27, 1996).
Alloys & Blends-Thermodynamically driven surface modification is being explored
successfully via chain end segregation in polymer blends which could lead to ‘self healing’
surfaces with important commercial potential.

Mayes and coworkers at MIT and U. of Missouri-Columbia have found using
neutron reflectivity and contact angle measurements that in thin film blends of
PS/PS-TFE the concentration of PS-TFE (single end functionalized) that localizes
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Jan-Feb 1997
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near the surface increases as a function of its concentration in the blend. A 10%
blend of PS-TFE (MW=6000) gave >20% coverage of fluorocarbon ends. A
theoretical free energy model supports these findings. One could expect even
higher coverage with polymers functionalized at both ends. In general,
thermodynamically induced surface segregation of a functionalized polymer
component would appear to have advantages over other methods of surface
modification. This technology might even be used to prepare ‘self healing’ surfaces
whereby surface regions that are scratched or worn are regenerated by continued
segregation of the functionalized polymer component until its equilibrium surface
concentration is reached. This work could have important commercial significance
in automobiles, aircraft, appliances, furniture, construction, etc. (Macromolecules,
29, 3982, 1996)
Selected patents follow in key polymer/plastics application areas including biodegradable
polymers, thermooptical coatings, polyester composites, and monomer recovery from PET
medical x-ray film.

“Biodegradable Polymer Compositions With Good Moldability And
Mechanical Strength”. M. Miura et. al. (Mitsubishi Gas Chemical Co.) JP 08
27,362, Jan. 30, 1996.The compositions comprise aliphatic polyester
polycarbonates prepared by polycondensation of aliphatic dibasic acids, aliphatic
dihydroxy compounds, and diallyl carbonates, and poly(b-hydroxybutyric acid) (I).
Thus, 70 parts 1,4-butanediol-diphenyl carbonate-succinic acid polymer and 30
parts I were mixed, melt kneaded, pelletized, and molded to give a molding
showing tensile strength of 20 MPa, heat distortion temperature 94C, Izod impact
strength 7 kg-cm/cm, and a five week-half period of biodegradation on embedding
a film of this composition in soil at 25C and 60% relative humidity. (Chem. Abs.
124: 262627j).

“Polymer Additive Composition Showing Thermooptical Effect, Especially As
Coating For Blocking Solar Radiation”. S. Meinhardt et. al. (Fraunhofer
Gesellschaft), DE 4,433,090 Mar. 21, 1996. The title composition contains an
additive (C10-25 alkanes) that shows a reversible change in refractive index with a
change in temperature and becomes less transparent in solar radiation with
increasing temperature. A glass sheet containing a coating comprising C10-25
alkanes and a binder prepared from phthalic anhydride, soybean oil, and
pentaerythritol, showed good transparency to solar radiation at 30C but became less
transparent to solar radiation on heating to 40C. The thermooptical effect was
reversible even after 1000 heating-cooling cycles. (Chem. Abs. 124: 319217g).

“Glass Fiber Reinforced Polyester Compositions With Improved Hydrolysis
Resistance”. T. Kinoshita, (GE Plastics Japan, Ltd.), JP 08 41,296, Feb. 13, 1996.
Compositions having good adhesion to the glass fibers comprise (A) 50-99 parts
polyesters, (B) 1-50 parts glass fibers, and (C) 0.05-10 parts (per 100 parts A + B)
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Jan-Feb 1997
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monoepoxy compounds. Thus, Valox 295 (polyester) 85, VCE 2 (glass fibers) 15,
EX 192 (monoepoxy compound) 0.5, and Na stearate (catalyst) 0.1, were melt
kneaded, pelletized, and injection molded to give test pieces showing tensile
strength 1020 initially and 480 after 100 hrs. at 120C/2 atm steam. (Chem. Abs.
124: 318835v).

“Recovery Of Dimethyl Terephthalate From Polymer Wastes”, R. Michel et. al.
(Dupont Co.) US 5,504,122, Apr. 2, 1996. Dimethyl terephthalate (DMT) is
recovered from polymer mixtures containing polymers of terephthalic acid and
glycol and a chloride polymer, by adding base to neutralize the hydrochloric acid
formed by the degradation of the chloride polymer. Adding 6.6 gm of 25% NaOH
to 400 gm poly(vinylidene chloride) coated PET film and subjecting the mixture to
methanolysis at 290C and 70 psig gave DMT with 83% conversion. (Chem. Abs.
124: 318143t).
Polymer Modification-New polyphosphazine elastomer chemistry has use with reaction
intermediates, thermally or UV crosslinkable polymers, and flame resistant interpenetrating
polymer networks.

Prof. H. Allcock and coworkers at Penn. State have prepared a number of new
mixed substituent poly(organophosphazines) with 2-butenoxy or
[4(allyloxy)phenyl]phenoxy (I) side groups. Cosubstituent groups include
trifluoroethoxy, phenoxy, or (benzyloxo)phenoxy. Post-reaction of I units with
linear silanes or siloxanes gave hybrid phosphazine/organosilicon polymers formed
by Si-H coupling. Many of the polymers prepared are rubbery elastomers that are
crosslinked by exposing to heat or UV light. Several of the mixed substituent,
crosslinked polymers formed IPN’s with polystyrene, PMMA, PAN, PAA, and
PDMSiloxane polymerized within the crosslinked matrix. Material properties vary
over a broad range dependent on the nature and ratio of the component polymers.
These poly(organophosphazines) are an excellent choice for making IPN’s because
of the ease with which properties can be changed by varying the side groups, the
component polymer, and the flame resistant features of the polymers. The unique
properties of these macromolecules can be used in combination with the advantages
of conventional polymers in applications such as membranes and bio medical
materials. (Macromolecules, 29, 2721, 1996)