Download Nylon Plays Wider Role in Auto, Electronics and Packaging Sectors

Nylon Plays Wider Role in Auto, Electronics and Packaging Sectors
(Apr 26, 2006)
Gordon Graff
Introduction
Comparing properties
Automotive applications
Electronics
Packaging
Conclusion
Introduction
Automotive, electronics and packaging applications are some of the fastest growing markets
for engineering plastics. This growth is opening up new outlets for nylon plastics because of
their high strength, high-temperature resistance, chemical resistance, as well as stiffness and
abrasion resistance. Moreover, these properties can be extended with appropriate fillers and
additives. At the same time, nylons, which fall under the polyamide category, are often less
expensive than competing engineering thermoplastics.
The ability of nylons to stand up to extremes is encouraging adoption of these materials in
several markets. In automobiles, for example, engines are running at hotter temperatures
than ever, requiring plastics that are heat resistant, especially in the presence of harsh
automotive fluids. In electronics, connectors have higher pin densities and thinner walls than
ever before, which requires resins with good flow and dimensional stability, two of nylon's
outstanding characteristics. Elsewhere in electronics, the increased use of lead-free soldering
- and consequently higher soldering temperatures - demands resins with exceptional heat
resistance. In packaging, there is increased emphasis on plastics that can prolong shelf life of
foods, while providing attractive, eye-catching enclosures. Nylon, with its good gas barrier
properties, mechanical strength and easy printability, is therefore becoming a frequent choice
for food packaging.
Comparing properties
Nylon 6,6 (PA 6,6) is the most popular form of nylon, followed by nylon 6 (PA 6). Other
commercial products include nylon 4,6; nylon 6,12; nylon 11; and nylon 12. Nylons can be
reinforced with carbon fibers and glass to add strength. Carbon fillers also give nylon
electrical conductive and static dissipative properties. Minerals and flame retardants are other
common additives to nylon. Nylons have a tendency to absorb moisture, which can degrade
the processed polymer properties unless the resins are dried before processing. However,
some types of nylon are less moisture-absorbing than others.
Properties
E-modulus (MPa), cond.
PA12 PA11 PA612 PA66 PA6 PA46
1100 1100
1800
1700 1100 1100
Notched Impact Strength at 23° C (Charpy, kJ/m 2), cond.
7
14
6
12
20
Notched Impact Strength at -30° C (Charpy, kJ/m2), cond.
6
11
6
4
3
12
Melting Point (DSC,° C)
178
189
218
260
222
295
Heat Distortion Temp. HDT-B (0.45 MPa, ° C)
115
145
180
225
170
280
Moisture Absorption (23° C/50% rel.h. , %)
0.7
0.8
1.3
2.5
3.0
3.7
Density (dry, gm/cm3 )
1.01
1.03
1.06
1.14 1.14 1.18
Table 1: Different commercial nylons exhibit a wide variety of properties.
(Source: EMS-Grivory)
45
Nylon 6,6 has a good balance of strength, stiffness, heat resistance, resistance to
hydrocarbons, lubricity and wear resistance. Nylon 6 has a better creep resistance but lower
modulus than nylon 6,6; it processes at some 27° C lower than nylon 6,6, and with less mold
shrinkage. Nylon 6 gives a lustrous surface, which is useful where appearance is a concern.
However, nylon 6 absorbs moisture more readily than nylon 6,6.
Nylon 4,6 has among the highest impact strengths of commercial grades of nylon, but its
modulus is less than that of nylon 6,6. Nylon 4,6 has excellent resistance to wear and friction,
and has outstanding flow characteristics, which makes it easy to process. However, the 4,6
material has a relatively high moisture absorption.
Compared to other nylons, nylon 12 has a relatively low concentration of amide groups in the
polymer chain, which gives it the lowest water absorption of any commercial nylon. It also has
good to excellent resistance to oils, fuels, hydraulic fluids, solvents and salt. The material also
resists stress cracking and abrasion.
Nylon 6,12 is also fairly low in moisture absorption and has many properties similar to nylon
12. However, compared to nylon 12, the 6,12 polymer has a higher heat deflection
temperature, and greater tensile and flexural strength.
Nylon 11 is also relatively low in moisture absorption. It features a high degree of chemical
resistance and the ability to accept high loadings of fillers. However, relative to other types of
nylon , nylon 11 is higher in cost and less heat resistant.
Automotive applications
Automobile air intake manifolds were once made of metal, but today are often fabricated from
30-35% glass-reinforced nylon 6. Nylon 6,6 and 4,6 are also used in manifolds. According to
an estimate by DSM, substituting metal in the manifolds with nylon reduces production costs
by up to 30%, reduces the weight of the part by up to 50%, cuts system costs through parts
integration and contributes to higher fuel efficiency. (For the intake manifold sector DSM
supplies nylon 6 and a high-flow grade of nylon 6 under its Akulon trade-name.).
Figure 1: Air intake manifolds are increasingly being fabricated from nylon 6 and nylon
4,6
(Source: DSM.)
Nylon 4,6 is occasionally used for air intake manifolds, especially where a manifold is
exposed to temperatures that exceed the capabilities of nylon 6 and nylon 6,6. According to
DSM, which offers nylon 4,6 under its Stanyl label for intake manifold applications, replacing
metals in manifolds with nylon 4,6 can cut costs by 10%.
Engine covers are another frequent nylon 6 application. Compared to other types of nylon, the
high-flow grades of nylon 6 are useful because they allow thinner walled designs, a better
surface appearance, and a wider processing window due to better flow and lower injection
pressures.
Figure 2: Engine covers benefit from high-flow grade of nylon 6 (Akulon Ultraflow),
which permits thinner walls and lower weight than standard nylons
(Source: DSM.)
Rocker valve covers are another place where nylon 6 is increasingly found in autos. For this
application, industry claims that nylon 6 maintains strength and stiffness better over the life of
the vehicle than nylon 6,6. It is also said to mold more easily than nylon 6,6, and to provide
the best toughness for manufacturing and end-use conditions.
In airbag containers, nylon 6 offers parts integration and reduced weight compared to metal
containers. Containers made of nylon 6 do not splinter at low temperatures, as do some other
polymers. Nylon 6 also possesses sufficient stiffness and strength to cope with high
temperatures without failure.
Figure 3: Good low-temperature performance and reliability are claimed assets of
airbag containers made of nylon 6
(Source: DSM.)
For a car's powertrain, plastic chain tensioner guides made of nylon 4,6 are being promoted
by manufacturers. One reason is that nylon 4,6 is said to offer better wear performance than
high molecular weight nylon 6,6. Nylon 4,6 in this application also reportedly enhances safety
and reduces noise generated by the chain.
Figure 4: Chain tensioner guides made of nylon 4,6 (Stanyl) are designed to offer
improved wear over nylon 6,6, plus less noise generation
(Source: DSM)
Nylon 6,6 has found its way into automotive cooling systems, where it allows consolidation of
various components once made of aluminum and plastics.
Figure 5: Nylon 6,6 cooling system
for Renault Mascott light truck
consolidates header tank,
inlet/outlet pipes, and radiator
support brackets once made of
different materials
(Source: BASF.)
Nylon 6,6 is also used in headlamp Bezels. According to DuPont, which supplies a heatresistant grade of its Zytel nylon 6,6 for this application, bezels made of nylon remain
dimensionally stable even when the headlamps reach their operating temperature of 150° C.
Nylon 6 also is being deployed in exterior automotive parts. These include door and tailgate
handles, exterior mirrors, front-end grilles, fuel caps and lids, and wheel covers and trim.
Elsewhere in the automotive world, nylon 12 is used in fuel lines, while nylon 6,12 is found in
hydraulic clutch lines.
Electronics
Nylon 6,6 has long been a material of choice in electronic connectors. But this material is
giving way to nylon 4,6 in this application because connectors are increasingly exposed to
high temperatures. This is especially the case as lead-free soldering continues to advance in
the industry. These high temperature soldering operations require connector materials that
are stable to at least 230° C. Today's connectors have higher pin counts than in the past,
requiring improved weld-line strength and better flow.
There is also a finer pitch between pins, which necessitates connector materials with high
flow, high mechanical strength, and exceptional weld-line strength. In many cases, nylon 4,6
meets all these requirements.
Figure 6: Molding connectors with nylon 4,6 (Stanyl)
led to less flash and less reworking than molding them
with LCP, according to the manufacturer
(Source: DSM.)
Nylon filled with electrically conductive materials can provide antistatic, electrostatic discharge
(ESD) and EMI/RFI shielding for electronic equipment, as well as for trays and conveyer
systems used in the manufacture of semiconductor chips. Common fillers in this application
include carbon fiber, carbon powder, nickel-coated carbon fiber, and stainless steel fiber. Just
about any variety of nylon can be used in ESD and EMI/RFI protection. PolyOne, for instance,
offers electrically conductive grades of nylon 6; 6,6; 12; and 6,12 under its Stat-Tech line of
conductive polymers.
Packaging
In food packaging, nylon 6 films provide excellent barrier properties that keep oxygen out and
seal aroma in. The films can be made by cast, blown or biaxially oriented polyamide (BOPA)
processes. Foods commonly packaged with nylon 6 resins include meats, cheeses, dried
foods, and chilled fruit juices. Oxygen permeability of the nylon films increases with
temperature and humidity.
Consumer packaging made of nylon 6 provides a good combination of strength, tear and
puncture resistance. An example of this packaging is air cellular cushioning, which protects
products from damage during shipment. In the medical field, nylon 6 is fabricated into tough,
puncture-resistant packages for medical blister packs.
Figure 7: Nylon 6 barrier properties make it useful for food
packaging (left). It also finds uses as protective packaging for
goods in transit (right).
(Source: Honeywell.)
Nanocomposites based on nylon 6 are also being developed for packaging applications. In
these cases, the polymer is loaded with 2-8% of an organically treated mica-like clay mineral
that is dispersed throughout the polymer in micron-size particles. According to RTP Co.,
which supplies nanocomposite compounds, films or sheets made of the nylon
nanocomposites display a fourfold improvement in oxygen barrier properties over unfilled
nylon 6 films. Compared to the unfilled nylon, the nylon nanocomposite also exhibit a 35° C
improvement in heat deflection temperature, more than a third greater tensile strength, and a
50% improvement in flexural modulus. Recommended packaging applications of the
nanocomposites include foods, cosmetics, medical products and electronic equipment
Conclusion
The unique properties of nylon resins, such as high strength, resistance to heat and
chemicals, and dimensional stability, are giving these materials an advantage over other more
costly engineering thermoplastics in three fast-growing end use markets: automotive,
electronics and packaging. There are a broad range of polyamides included in the nylon
class, each with their own property profiles. Additives and fillers are vital elements in
extending the properties of nylon into new regimes, thereby opening up new markets to these
materials.
References:
Website:
Albis Plastics, Arkema, Asahi Thermofil, BASF, Degussa, Dow, DSM, DuPont, EMS-Grivory, Honeywell Plastics,
PolyOne Corp., Rhodia, RTP Co., Solvay.
Publication:
Robert D. Leaversuch, "Strength and Beauty: New Nylons Bring Both to Under-Hood Parts," Plastics Technology,
Jan., 2003.
"Six Always Wins in Nylons Game," Modern Plastics, July, 2004.
Joseph A. Grande, "New High-Performance Nylons for Automotive, Electronics, Packaging," Plastics Technology,
May, 2005.