Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-11-20
2002-06-04
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06399707
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polymer blends. More particularly, the invention relates to polymer blends useful for molding applications for forming molded articles. More particularly, the invention relates to polymer blends useful for injection molding for forming polymeric articles such as automotive exterior components and particularly, painted automotive exterior components. Examples of automotive exterior components include, but are not limited to bumper fascia, wheel flares, exterior molding, and step pads.
SUMMARY OF THE INVENTION
A polymeric material suitable for fabrication into an article and particularly a polymeric material suitable for fabrication into an article suitable for receiving paint is provided. The polymeric material may be a blend of impact copolymer and plastomer. The impact copolymer includes between 95 and 78 wt % homopolypropylene and between 5 and 22 wt % of ethylene-propylene rubber, wherein ethylene propylene rubber may have less than about 50 wt % ethylene. The plastomer may be an ethylene/hexene plastomer. The ethylene/hexene plastomer may have a density in the range from 0.88 to 0.915 and a melt index (dg/min) from 0.8 to 10. The impact copolymer may be present in the blend in a range of 95 to 70 wt % and the ethylene/hexene plastomer may be present in the blend in a range from 5 to 30. The propylene, ethylene and hexene components may be present in the blend in respective ranges of 73.2 to 84.2 wt %, 14.3 to 23.1 wt % and 1.5 to 3.7 wt %.
DETAILED DESCRIPTION OF THE INVENTION
Test protocols and definitions are set out in Table 1, and described in more detail in the specification.
TABLE 1
Test Protocols
Property
Units
Definition or Test
Density
g/cm
3
ASTM D-792
Molecular weight distribution
None
None
Tensile at Yield
Psi
ASTM-D638
Elongation at Yield
%
ASTM D-638
Secant Modulus (1%)
Psi
ASTM D-790A
Gardner Impact at −29° C.
in-lbs.
ASTM D-5420G
Instrumented Impact Strength
ft-lbs.
ASTM-D-3763
Room Temp. Notched Izod
ft-lb./in
ASTM D-256
Physical Property Measurements:
Melt Flow Rate (MFR):
MFR was measured according to ASTM D 1238 test method, at 230° C. and 2.16 kg load, and is expressed as dg/min or g/10 min.
Tensile Strength at Yield and Elongation at Yield:
Tensile strength at yield was measured according to ASTM D638, with a crosshead speed of 50.8 mm/min, and a gauge length of 50.8 mm, using an Instron machine.
Flexural Modulus:
The flexural modulus was obtained according to ASTM D790A, with a crosshead speed of 1.27 mm/min (0.05 in/min), and a support span of 50.8 mm, using an Instron machine.
Gardner Impact Strength and Failure Mode:
The Gardner impact strength was measured according ASTM D5420, Method G, Procedure GC, at −29° C. and on 90-mm diameter and 3.175-mm thickness disks. The failure mode is classified as shatter, brittle, and or ductile, based on the appearance and condition of the impacted disk. For example, the classification of “shatter” is appropriate when the test disk fractures into multiple pieces (often the number pieces can range from 10 to 15) on impact by the falling weight. The classification of “brittle” is appropriate when the impacted disk exhibits many radial cracks extending from the area of the impact point. These radial cracks do not propagate all the way to the outer periphery of the disk and portions of the disk defined by the radial cracks do not separate. The classification of “ductile” is appropriate when, after impact, an area of the disk contacted by the weight protrudes from or appears pushed out from the disk surface. The protruding area is generally unsymmetrical and exhibits a crack on one side. Portions of the disk surface defining the extended area appear rough and fibrillar in nature. The failure modes of shatter-to-brittle, brittle-to-ductile, are combinations of two different types of failure modes exhibited by the disk. The failure mode of brittle-to-ductile, which is between shatter and ductile, is characterized by radial cracks extending from the protruding area. However, portions of the disk defined by the radial cracks do not separate. While the failure modes described above are based on human judgment, rather than a quantitative number from an instrumental evaluation, these failure modes are reproducible and provide both the polymer producer and the parts fabricator with reliable information relative to the suitability of polymers for various applications. An individual trained and experienced in this test procedure can classify different polymeric materials using the Gardner impact test procedure with accuracy.
Notched Izod Impact Strength:
The room temperature notched Izod impact strength (RTNI) is measured according to ASTM D256 test method. The impact strength equipment is made by Testing Machines Inc.
Instrumented Impact (Dynatup):
The instrumented impact strength is measured by ASTM D3763 using a Dynatup model 8250. A weight of 25 pounds and a speed of 15 miles per hour are used to measure the failure mode and the total energy. The weight is adjusted such that the velocity slowdown is less than 20%.
The failure mode is defined as ductile (D) if the load vs. displacement curve is symmetric and there are no radial cracks in the sample and the tup pierces through the sample. The ductile-brittle (DB) failure mode is defined as the mode where on the load-displacement curve, the load goes through the maximum, and suddenly drops to zero and there are radial cracks in the sample. And, brittle-ductile (BD) failure mode is defined as the condition where in the load-displacement curve, the load falls well before reaching a maximum and the sample breaks into multiple pieces. The desirable failure mode is completely ductile at the specified temperatures.
Paint Adhesion Testing
This test is one of the simplest and most widely recognized test methods in the automotive industry utilized to determine relative adhesion of paint on plastic. This test involves making a series of cuts in the coating, applying a pressure-sensitive tape over the cuts, and removing the tape and quantifying the degree of paint adhesion. Specifically, the paint system used is the following: Adhesion promoter/Base Coat/Clear Coat (Redspot LE16610XM/Redspot 106S21945RRN (1K White BC)/Redspot 379S21654EPCX (2K Clear). These tests were carried out, data for which is in Table 7.
Moisture Resistance
Same criteria for Paint Adhesion Testing. This testing is designed to determine the adequate cure of the paint (example, over-cured paint can lead to poor humidity/moisture resistance).
Aggressive Adhesion and Scuff Resistance Testing
This is a two-part test designed to quantify the performance of a TPO (thermoplastic olefin) relative to paint durability. The aggressive adhesion is designed to evaluate the paintability to penetrate into the TPO, and the scuff abrasion portion of the test is designed to evaluate adhesive (% removal) cohesive integrity of the TPO to withstand scuffing and marring.
Rating: Both the aggressive adhesion and scuff are rated in terms of percent (%) removal. Results of less than 20% for both indicate a desirable performance criteria, and results of less than 2% removal for both indicates excellent results.
Gasoline Resistance
This test is conducted to help determine the propensity of solvents to penetrate the TPO substrate. This propensity is quantified by immersion of crosshatched topcoated panel in CE-10 gasoline over a 15-minute period at room temperature and continued up to 60 minutes of duration and evaluated every 15 minutes (i.e., 15, 30, 45 and 60 min). CE-10 is a mixture of the following: 10/90 ethanol/reference fuel C, reference fuel C is a 50/50 blend of toluene/iso-octane by weight.
Polymeric materials may be employed in a variety of applications such as for example, household appliances, fabrics (woven and nonwoven), containers, pipes, and automotive parts. In the case of automotive parts, depending upon the physical properties of a particular polymeric material, the polymeric material may be used to form articles suitable for use in the automobile cabin area (t
Burke Paul J.
Killinger Kris K.
Luce James T.
Meka Prasadarao
Valentage Jeffrey
Alexander David J.
ExxonMobil Chemical Patents Inc.
Faulkner Kevin M.
Nutter Nathan M.
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