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PEL PLASTICS UPDATE highlights recent progress in key areas of
polymer/plastics technology including: catalysis, biopolymers, smart/functional
polymers, alloys & blends and polymer modification. A recent issue of PEL
Plastics Update follows.
Complimentary Copy
Vol. 5, No. 5
PEL PLASTICS UPDATE
Sept-Oct, 1997
By Mort Wallach
ISSN 1094-656X
RECENT PROGRESS IN POLYMER/PLASTICS TECHNOLOGY
Nanotechnology-New polymer composites with nanoscopic silicate
minerals exhibit improved properties including flame resistance, structural
characteristics, and gas barrier features which have important industrial
potential. Polyimide nanofoams were developed with possible applications in
microelectronic devices, and optically transparent polyimide composite
waveguides were prepared by dispersing nanosized TiO2 particles into
the polymer matrix.
- Prof. E. Giannelis and coworkers at Cornell in Ithaca, NY and Kolon
Chemical, of S. Korea prepared nanocomposites with enhanced properties by
attaching alkyl chains to the surface of mica-type minerals dispersed in
polymers including polyesters, polystyrene, and polyethylene oxide. The cation-exchanged
silicates readily form nanocomposites of either intercalated (slightly
separated silicate layers) or an exfoliated arrangement (highly dispersed
mineral blocks). Property enhancements include flame resistance, structural
features and gas diffusion. These systems have important practical potential
in a variety of markets including automotive, appliances and electrical
applications. (M. Jacoby, C&EN, Oct. 6, 1997, p. 35)
- R. Briber and coworkers at U. of Maryland in College Park have
prepared new polyimide nanofoam films with possible applications in
microelectronic devices. They were produced from triblock copolymers derived
from polyimide as the center block [e.g., pyromellitic
dianhydride-1,1-bis(4-aminophenyl) -1-phenyl-2,2,2-trifluoroethane] and
polypropylene oxide as the end blocks. The nanofoam was produced in a three
step process: spin-casting the triblock copolymer onto a Si substrate, thermal
imidization of the center block and thermal treatment in air to degrade the
polypropylene oxide domains and form nanoscale voids. (Mater. Res. Soc. Symp.
Proc., 461, 103, 1997)
- P. Prasad and coworkers at SUNY, Buffalo have prepared optically
transparent polyimide-TiO2 composite waveguide materials by the
dispersion of nano-sized TiO2 particles into the polyimide matrix.
The particles were produced through reverse micelles using the sol-gel method,
and were dispersed into the fluorinated polyimide (Ultradel 9020D) solution.
The solution was coated on to a glass substrate, and a polyimide-TiO2
composite waveguide (4 wt % TiO2 concentration) was successfully
produced after heat treatment. Because the particle size was very small, no
noticeable scattering loss was observed. The measured optical propagation loss
at 633 nm was 1.4 dB cm-1. It is equivalent to that of the pure
polyimide, and the refractive index was increased from 1.550 to 1.560 by the
incorporation of the TiO2 particles. This is another demonstration
of the diverse and important applications of nanotechnology. (J. Mater. Sci.,
32, 4047, 1997)
Supramolecular Structures-Polyion films in intricate tailored
patterns were built into ultra-thin multilayers on gold substrates. Chemical
functionality was directly programmed into the surface so that adsorbed polyions
form microstructures by self-assembly. The technique has much promise and could
be used for device fabrication involving customized refractive index, or unique
emittance, or electron-transfer properties.
- Prof. P. Hammond and coworkers at MIT have created supramolecular
structures with controlled nanometer sized horizontal and vertical resolution.
An example involves coating gold surfaces with parallel columns of polyion
films, e.g., strips of film a few hundred nanometers thick form 3.5 µm wide
lines separated from each other by 2.5 µm. Substrates were prepared using the
microcontact printing technique developed by G. Whitesides of Harvard. The
gold surface patterned with regions of alternating chemical functionality
serves as a molecular template for polyanions. Adsorption of polyanion layers
thereby proceeds with lateral selectivity and researchers can experimentally
control whether layers of polycations or polyanions preferably assemble on
selected regions. Since chemical functionality is directly programmed into the
surface, adsorbed polyions form microstructures by self-assembly. The method
has much promise for making electronic and optical devices such as
electroluminescent instruments and sensors that diffract light of certain wave
lengths under controlled conditions, and possibly wave guides for fiber
optics. (PMSE, 77, 620, 1997)
Biopolymers-Further understanding of how the protein p53
protects against cancer has been uncovered as a three step process by which p53
kills potential cancer forming cells.
- B. Vogelstein and coworkers at Johns Hopkins U. in Baltimore have
developed a biomolecular map of how the p53 protein protects against cancer by
determining which genes are activated by p53. Measurements were made of the
amount of various messenger RNA molecules present in cells that contain active
p53 as compared to mRNA in control cells. The mRNA levels indicate which genes
are functioning and their level of activity. In this way the researchers
identified genes which were activated by p53 and their function. It turns out
that many of these genes encode proteins that can generate or respond to
oxidative stress. Overall, these results suggest that there is a three step
process by which p53 kills cells that otherwise could become cancerous. First
the p53 switches on redox-related genes. Products of these genes then produce
reactive oxygen species which cause degradation of components of the cell's
mitochondria. This leads to the death of cells which are potentially
cancerous. (Nature, 389, 300, 1997)
Alloys & Blends-In studies of the compatibilization of the
polyamide/polyethylene system with functionalized polyethylene (PE-g-GMA), Nylon
11 exhibits the most efficient grafting as compared to several other aliphatic
polyamides.
- E. Koulouri and workers at U. Patras, in Patras, Greece have
investigated the grafting efficiency of different nylons (e.g., 6, 11, 12,
6-10, and 6-12) with ethylene-glycidyl methacrylate copolymer (PE-g-GMA) and
ethylene ethyl acrylate copolymer at a composition of 85/15, when melt-mixed
under optimum conditions. Two of these-nylon 6 and 11-were studied in the
complete composition range. Using techniques like dynamic mechanical analysis,
tensile testing, differential scanning calorimetry, SEM, and Fourier transform
infrared spectroscopy (FTIR) for the characterization of the blends it was
shown that the most efficient grafting occurred in the case of nylon 11/PE-g-GMA
blends. The formation of a copolymer was confirmed by extraction experiments.
The existence of both polymers in the isolated copolymers was proven by FTIR
and thermal analysis. Overall, the concept of the compatibilization of the
polyamide-polyethylene system was confirmed in the case of nylon 11/HDPE
compatibilized by PE-g-GMA. (Polymer, 38 (16), 4185, 1997)
Alloy & Blend Patents-Among 1000 patents reviewed during this
period, several noteworthy inventions include: ternary polyetherimide/polyester
blends with improved transparency, TPO laminates for automotive parts,
transesterification inhibited PET compositions, and inorganic compound-coated
film with good moisture resistance.
- "Ternary Polyetherimide/Polyester/Polyester Blends With Improved
Transparency". C. E. Scott (Eastman Chemical Co.) US 5,648,433, July 15,
1997. A visually clear blend of thermoplastic polymers comprises (A) a
polyetherimide, (B) a mixture of polyesters comprising: (1) a polyester
comprising repeat units from (a) 2,6-naphthalene dicarboxylic acid and (b)
ethylene glycol (I) and (2) a polyester comprising repeat units from
(a) an acid of terephthalic acid and isophthalic acid or mixtures thereof, and
(b) a glycol of I 1,4 cyclo-hexanedimethanol (II) or a mixture
thereof. A blend containing Ultem 1000 (polyetherimide) 30, I-dimethyl
2,6-naphthalene dicarboxylate copolymer 14, and di-Me terephthalate-I-II
copolymer 56%, gave injection-molded test pieces with clear appearance,
Rockwell hardness 104L, and flexural modulus 342 kpsi. (Chem. Abs. 127:
136506t)
- "Thermoplastic Elastomer Composition Laminates For Automobile Parts".
K. Kobayashi (Mitsui Petrochemical Ind.) JP 09,156,009, June 17, 1997. The
title laminates, giving automobile parts having good scratch resistance,
lightweight, recyclable, and no toxic gas generation, even on incinerating,
comprise (a) an embossed surface layer prepared from (a1) polyolefin blends
containing 15-45% ultrahigh molecular weight polyolefins (e.g., UHMWPE) and
60-85% low-or high-molecular weight polyolefins (e.g., LDPE) 10-50, (a2)
hydrogenated block copolymers of styrene (derivatives) block and isoprene or
butadiene-isoprene block (e.g., hydrogenated isoprene-styrene block copolymer)
50-90, and optionally (a3) silicone oil (e.g., SH 200) aliphatic alcohol-(dicarboxylic
acid or fatty acid) esters (e.g., distearyl phthalate) fluoropolymers (e.g.,
KF Polymer W-1000), and/or fatty amides (e.g., erucamide, oleamide, ethylene
bisoleamide) 0.01-10 parts, and (b) a base layer of (b1) polyethylene or
polypropylene foams or (b2) crystalline polyolefins or polyolefin-olefin
rubber (e.g., EPDM) crosslinked products. (Chem. Abs. 127: 122676m)
- "Transesterification-Inhibited Poly(Ethylene Terephthalate) Melt Blend
Compositions Having Improved Dyeability". W. Cattron et. al. (Amoco Corp.)
US 5,646,208, July 8, 1997. Melt blend compositions, useful for shrink fiber
and film and as powdered binders for nonwoven fabrics having high m.p.,
improved dyeability and good solvent resistance, comprise poly(ethylene
terephthalate) (PET) and poly(ethylene isophthalate) (PEI) or random
copolymers of poly(ethylene terephthalate) and poly(ethylene isophthalate) and
an inter-esterification inhibitor. Thus, PEI dried pellets (prepared from
isophthalic acid and ethylene glycol) 566.7, PET dried pellets 2266, and
Ultranox 626 [bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite]
transesterification inhibitor 14.24 g were blended and melt-extruded at 280C
to give a blend showing m.p. 253.0C, Tg 76.0C and fiber shrinkage
(2 min at 80C, spun at 32 m/min) 9.5%. (Chem. Abs. 127: 149783f)
- "Inorganic Compound-Coated Plastic Film With Good Moisture Resistance
And Good Flexibility". T. Azuma et. al. (Kureha Chemical Ind.) JP
09,183,179, July 15, 1997. The film comprises, in sequence, polymer substrate,
evaporation coated inorganic compounds, gas-barrier polymer coatings and
relief layers, where the relief layers (Lf) satisfy with 5 N/mm < elastic
modulus of Lf (GPa) x thickness (µm) of Lf < 90 N/mm. Thus, a film was
prepared by bonding a Si oxide-coated (on PET side; thickness 3 µm) laminate
of PET and vinyl chloride-vinylidene chloride copolymer and LDPE (thickness 40
µm; elastic modulus of MD 0.18 GPa, of TD 0.22 GPa). (Chem. Abs. 127: 150017r)
Automotive Plastics-Thermoplastic car-body materials are being
employed in several new models. Favored materials include: alloys & blends and
composites of Noryl GTX (nylon/ PPO), Azdel PP glass mat, PET glass filled
polymer, and Xenoy (PC/PBT) systems. Cars employing these plastic body materials
are no longer niche vehicles with production levels expected at 100,000 to
200,000 vehicles/yr. Several of these applications were shown at the recent show
in Frankfort.
- Unveiled at the recent Frankfort International Motor show was the
plastic-bodied Composite Concept Vehicle (CCV) by Chrysler made of recyclable
15% glass filled PET. Panels are assembled (4 per car) with polyurethane
adhesive on a steel chassis. There are only 1100 parts (vs 4000
conventionally) and no paint is required. The car weighs half as much (1,200
lb) as a comparable metal car, and gets 50 mpg. The plastic panels can be
recycled and contain up to 20% recycled PET themselves. The car is aimed for
developing countries by the year 2000 and will sell for about $6000. The
panels are molded on a 9000 ton injection molding machine with 160 ton molds
which are 3X larger (14 X 8 X 6 ft) than any other mold used in automotive
applications. The polyester composite is relatively inexpensive at $1.50/lb
compared to other plastic blends and composites. Cycle times are only 3 min (vs
twice that for comparable SRIM sections) due to novel gate and gas injection
sequences. Other cars introduced with plastic panels include the new Mercedes
compact A-Class tailgate of Noryl GTX outer skin (and front fenders) and Azdel
PP glass mat inner skin; the new Land Rover Freelander also with front fenders
of Noryl GTX; the new VW Beetle with front and rear fenders of the same
material. GE claims car manufacturers can achieve up to 50% fender weight
reduction by switching from steel to Noryl GTX, with repainting only required
at collision speeds of 35 km/hr compared to the need for steel fender
replacement after simulated collisions of just 8 km/hr. Meanwhile, the
Mercedes/Swatch joint venture (MCC) also introduced a completely plastic clad
car which is due in production very soon. It has self-colored Xenoy (PC/PBT)
exterior panels with a clear coat. (Modern Plastics, Oct. 1997, p. 17)
New Polymer Ventures/PEN-Several major chemical companies
including (Amoco, Eastman Chemical, Shell, ICI, DuPont, Teijin Chemical, and
Mitsubishi Gas Chemical) have entered the poly(ethylene naphthalate) (PEN)
business. Key target markets include glass and aluminum which supply 16 billion
bottles for beer and 35 billion cans for soft drinks annually. However, some
important issues remain including monomer availability, pricing, FDA and
recycling concerns. Performance-wise the future looks good with markets
including film, fiber, and packaging. PEN's rigid chain architecture accounts
for its increased strength, heat stability, and barrier features as compared to
PET. Current entry markets involve specialty films such as in advanced photo
system cameras (where PEN provides thinner gauge and better curl resistance),
and electronic film applications (where PEN enhances thermal performance, aging,
and dielectric properties). However the film market now represents only a small
specialty opportunity of 2MM lbs (with 9 MM lbs projected for the year 2000).
Amoco Chemical is the only US producer of the main PEN raw material naphthalene
dicarboxylate (NDC) and the price of PEN ($4-5/lb) is strongly determined by
that of NDC. Capacity is currently 60 million lb/yr. As a result a virtual
single source has led to some significant reported delays in PEN development
programs. However, Amoco has plans for a plant expansion (Decatur, AL) to from
85-110 million lbs/yr. Larger market opportunities in fibers and packaging are
more sensitive to supply security. Applications in the fiber market include tire
cord (the largest) to replace rayon in high speed vehicles and industrial uses
such as equipment belts and heavy-duty cables as a possible steel replacement.
Much of this work is in the early developmental stage. The best opportunity for
PEN is the packaging market due to its higher Tg and improved barrier
properties. This puts PEN in a good position to replace glass and aluminum cans
in applications which could not be captured by PET. Its higher temperature
capabilities along with light weight and shatter resistance open up many food
container possibilities. PEN's heat stability allows it to be used in the
returnable/refillable beer bottle market. Improved barrier properties make PEN
suitable for small 12 oz beverage containers where PET can not be used. However,
packaging market penetration is very price dependent and in the year 2000 Kline
& Co. estimates penetration of only 1.6 MM lbs @ a price of $3.25/lb, and 5 MM
lbs @ $2.00/lb; in 2005 the volumes are projected to be 14 MM lbs @ $3.25/lb and
140 MM lbs @ $1.50/lb, respectively. Other larger estimates have also been made.
The use of blends and copolymers with PET are being investigated to address the
price issue. From a technical point of view this approach is straight forward
but FDA approvals and resolution of recycling issues could be slowed down. Since
most PEN companies are also major PET players any development strategy must
consider the impact it may have on the PET business. (P. Morse, C&EN, Nov. 10,
1997, p.8)
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