1. Characterization of ExxonMobil Escorene and
Achieve Polypropylene Melt Blown Nonwovens
Stephen R. Whitson
Summer 2011
Abstract
The purpose of this research was to analyze the differences in properties of Exxon
Mobile’s Escorene polypropylene resin and their new polypropylene resin Achieve. Both resins
were run through and Industrial Melt Blowing Line at an air pressure of 10 psi, DCD (Die-To-
Collector) distance of 20 cm, and Air Temp of 500 ᵒF to produce non-woven webs. As well as
this, three different Achieve webs were produced and tested, by running the resin at different air
pressures (10 psi – 5 psi) and DCD distances (20 cm – 35 cm). After thickness and fiber diameter
was found (avg. thickness = 1 mm, avg. fiber diam. = 2 μm) each web was tested using ASTM
D737 air permeability method, ASTM D5035 tensile test method, ASTM D5734 Elmendorf tear
test method. A TGA was also performed on both Escorene and Achieve pellets and resins; all
materials lost the majority of weight at around 300 ᴼC. Tensile tests showed that the Achieve
web had a higher average peak load and elastic modulus than the Escorene web. It also showed
that accordingly named PC3 web was had the greatest average peak load (1732 gms) and elastic
modulus (1296194 gms/in²) in the cross direction, while the PC2 web had the greatest average
peak load (2759 gms) and elastic modulus (3576177 gms/in²) in the machine direction.
Introduction
Background
Polypropylene is an isotactic thermoplastic polymer; a crystalline material it is noted for
its high strength-to-weight ratio, excellent chemical resistance and high performance in
thermoforming and corrosive environments. It is a versatile polymer that can be used for a
variety of plastic applications including containers, tools, mechanical parts, and textiles. Both
ExxonMobil’s Escorene and Achieve resins are polypropylene homopolymers designed for melt-
blowing applications. Achieve is the next generation having a higher MFR (1550 g/10 min) and
larger resin particles. It is also free of the peroxides, which the Escorene resin contains to control
rheology (flow). The melt flow rate (MFR) is an indirect measure of the molecular weight of a
thermoplastic polymer. The measure helps to determine how easily the molten raw material will
flow during processing.

2. Melt blowing is a process for producing fibrous non-woven webs from polymers or
resins. “Melt-blowing is a one-step process and one of the most practical processes for producing
microfiber nonwovens directly from thermoplastic polymers, in which hot/high velocity air
blows the extruded filament from a die tip towards a moving conveyer belt or a cylinder.” [1] In
a melt-blowing line the resin is heated to melting temperatures as it is extruded through a screw
(or screws). The extruded polymer, is then suctioned through a metering pump in order to control
flow rate. The resin is then discharged to the melt-blow die; the die contains holes through which
the molten resin is pushed. The resin is then immediately hit with high velocity hot air coming
from both top and bottom (at various angles) of the die assembly. This extenuates and tangles
fibers unto a conveyor belt which is then fed to a rolling assembly. Schematics of process are
shown below.
Figure 1. Hopper and screw extruder [2] Figure 2. Die To Collector [2]
Figure 3. Schematic of MB process [2]
Testing
To discover how well air flows through a fabric or web an air permeability test is done.
Air permeability is the rate of air flow passing perpendicularly through a known area under a
prescribed air pressure. According to ASTM D737 ten samples are tested to produce at least 4
samples that have values within 5% of one another.

3. Figure 4. TexTest FX 3300 Air Permeability Tester Figure 5. EJA Tensile Tester
A tensile tester was used to produce a load vs elongation graph. According to ASTM
D5035 8 (1” gauge) samples are tested in the cross direction and 5 (1” gauge) samples are tested
in the machine direction. All 8 cross direction samples must be within 50% of one-another for all
values; all 5 machine direction samples must be within 50% of one-another for all values.
Machine direction is defined as the direction that the fibers are blown onto the conveyor belt; the
cross direction is transverse to the machine direction. A tensile testing instrument will apply an
increasing amount of tensile load on a material, in a specified direction, measuring the elongation
along the direction of the tensile force until the sample fractures. A load vs. elongation curve can
then be mapped from the data. From this curve we can deduce many different aspects of the
particular materials properties. At the beginning of the curve is linear with an even slope. This
slope represents what is called the modulus of elasticity, which can be thought of as the stiffness
of the material; the resistance to permanent deformation. At a certain point the slope ends and the
curve begins to bend, going slowly upward until it reaches its maximum point, the tensile
strength or peak load. Past this point the material can no longer maintain structure, will begin to
break down and eventually fracture. Because the process of breaking down often decreases the
cross-sectional area of the specimen the load-elongation curve will begin to bend downwards as
the area decreases faster than the force of the load increases. It will continue until the fracture
point the maximum load that the sample was able to handle until breaking; at which point data
can no longer be recorded.
The Elmendorf tear “test method covers the measurement of the average force required to
propagate a single-rip tear starting from a cut in a nonwoven fabric using a falling-pendulum
(Elmendorf) apparatus.” [3] It is a measurement of how much resistance a fabric provides against
tearing. According to ASTM D5734 5 samples (2.5” by 4”) are tested in the cross direction and 5
samples (2.5” by 4”) are tested in the machine direction.

4. Figure 6. TexTest FX 3750 Tear Tester Figure 7. Mettler Toledo TGA/SDT 851
To determine the amount of weight loss that materials undergo under certain
temperatures a TGA test is performed. Thermal gravimetric analysis (TGA) is a type of testing
performed on samples that measures and graphs changes in weight in relation to change in
temperature.
Experimental
Melt-Blowing
An industrial melt blowing line with Haake twin screw extruder, Zenith metering pump,
Ingersol-Rand air compressor, colletor, and 6 in. (120 hole) die were used to melt blow non-
woven webs from ExxonMobil Escorene and Achieve resins.
Table 1. Initial MB processing conditions for ExxonMobil Polypropylene Resins
Parameters Escorene® PP3546 Achieve® 6936G1
Air Pressure: 10 psi 10 psi
DCD: 20 cm 20 cm
Colllector Speed: 137 rpm (4.9 m/min) 137 rpm (4.9 m/min)
Extruder Speed: 57 rpm 69 rpm
Extruder Pressure: 160-180 psi 370-380 psi
Pump Pressure: 11 psi 14 psi
Pump Speed: 8.5 rpm 8.5 rpm
Air Temp: 500 ᵒF 500 ᵒF

5. In order to maintain a basis weight of 100 grams for each web, extruder speed and the pressure
the of extruder and pump were adjusted. Air temperature and pressure, DCD (Die-To-Collector
distance), and collector speed were kept the same when processing both webs. The Achieve resin
was also run at three different processing conditions. The extruder speed and pressure, pump
pressure, and collector speed shown below were kept constant. However DCD and air pressure
were changed to produce three different Achieve webs (PC1, PC2, PC3).
Table 2. Achieve MB processing conditions
Extruder Speed: 69 rpm
Extruder Pressure 350-380 psi
Pump Pressure: 15 psi
Collector Speed: 137 rpm (4.9 m/min)
Table 3. Achieve MB processing conditions
Air Pressure
Sample DCD (cm)
(psi)
PC1 20 10
PC2 20 5
PC3 35 5
Thickness and Fiber Diameter
Tests were conducted under ASTM D5729 standard for Escorene and 3 types of Achieve
web. Web thickness was measured using TMI 49-70, 10 times per web in accordance with
ASTM standard D5729. Fiber diameter was calculated by examining microscopic images of each
web and using ImageJ to measure the average fiber diameter for each web. 6 images were
examined for each web, and 10 measurements were made per image.

6. Figure 8. Escorene Web Microscope Image Figure 9. Achieve/PC1 Web Microscope Image
Figure 10. PC2 Web Microscope Image Figure 11. PC3 Web Microscope Image
Air Permeability
Tests were conducted using TexTest FC 3300 Air Permeability Tester under ASTM
D737 standard for Escorene and 3 types of Achieve web. 10 samples larger than 5.93 in² of each
web were prepared from the center of the web reel. Each sample was secured in the crosshead
and test run. Values were recorded in cfm (Cubic Foot per Minute).
Tensile Test
Tests were conducted using EJA Tensile Tester (10 lb load cell) under ASTM D5035
standard for Escorene and 3 types of Achieve web. 8 samples 1” wide and 6” along cross
direction were loaded into tensile tester and then tensile test was run. Following this, 5 samples
1” wide and 6” along machine direction were loaded into tensile tester and then tensile test was
run. Peak load, Peak Elongation, and Modulus values were recorded for each run.

7. Elmendorf Tear Test
Tests were conducted using TexTest FX 3750 Elmendorf Tear Tester under ASTM
D5734 standard for Escorene and 3 types of Achieve web. 5 samples 4” wide and 2.5” along
cross direction were loaded into tensile tester and then tensile test was run. Following this, 5
samples 4” wide and 2.5” along machine direction were loaded into tensile tester and then tensile
test was run. Values were recorded in cN (CentineNewton).
TGA
Tests were conducted using Mettler Toledo TGA/SDT A851 and results were evaluated
using Star-e vs. 8.10. Four tests were run, one each for Escorene pellets, Achieve pellets,
Escorene web, and Achieve web. Samples were loaded into a ceramic crucible, which had been
previously tared, and weighed. The crucible containing the sample was then loaded into the TGA
and temperature program run. The temperature program ran from 25 ᴼC to 650 ᴼC at 10 ᴼC/min.
Results and Discussion
Table 4. Web Properties of Escorene and Achieve
Polymer Fiber Diam. (µM) Thickness (mm) Air Perm (cfm)
Mean 1.95 1.15 27.57
Escorene®
Std. Dev. 0.60 0.10 1.02
Mean 2.28 1.31 24.59
Achieve®
Std. Dev. 0.67 0.07 0.89
10 10
Measurements
measurements
5 5
Per 30
Per 30
0 0
1 1.5 2 2.5 3 3.5 4
Diameter (μm) Diameter (μm)
Figure 12. Escorene Fiber Diam. Distributio Figure 13. Achieve Fiber Diam. Distribution
As we can see from these results, under the exact same processing conditions the Achieve
resin produced a thicker web most likely due to the larger fiber diameter. Both the Achieve and
Escorene web attained the same basis weight of 100 grams however, which shows that the
Achieve resin is slightly less dense than the Escorene resin. The Escorene contains peroxide
which breaks down the polymer chains into shorter units in order to control flow rate. The
Achieve being peroxide free “achieves” better flow rate, while retaining the longer polymer

8. chains. This lack of peroxide however, makes the Achieve less dense since the longer polymer
chains don’t pack as tight. Being thicker the Achieve web was slightly less permeable than the
Escorene web.
2000
1800
1600
1400
1200
Escorene MD
Load (gms) 1000
Achieve MD
800
Escorene CD
600
Achieve CD
400
200
0
-0.2 0 0.2 0.4 0.6 0.8
Elongation (in)
Figure 14. Load vs. Elongation in MD and CD for Escorene and Achieve Webs
Table 5. Tensile and Tear Properties of Escorene and Achieve
Peak Load Peak Elongation (% Modulus Elmendorf
Polymer (gms) in) (gms/in²) (cN)
Mean 1403.0 5.40 1,283,755 51.7
Escorene® Std.
Dev. 164.3 0.90 288,090 15.8
Machine Direction
Mean 1894.6 5.07 1,758,291 49.4
Achieve® Std.
Dev. 228.7 0.42 158,099 11.9
Mean 605.6 18.45 244,525 79.6
Escorene® Std.
Dev. 39.4 2.55 14,633 18.8
Cross Direction
Mean 619.7 8.39 347,856 68.6
Achieve® Std.
Dev. 17.3 0.8 18,948 6.6

9. From the graph and table you may notice the large difference in curves between the
machine and cross directions. When a non-woven web is formed, the majority of the fibers
usually fall into place in the machine direction, which means when a tensile test is run in this
direction we are looking at the strength of the fibers until they break apart. In the cross direction
however, we are looking at the strength of the horizontal bonds between the individual fibers as
they break apart from one-another. This means that as a rule fabrics will have better tensile
strength in the machine direction. The trend we see from the load vs. elongation graph is the
Achieve web is stronger and stiffer (having a higher modulus). This is mostly due the difference
in length of polymer chains within each resin. Because the Achieve is peroxide free, it contains
longer polymer chains that give it it’s larger tensile strength in the machine direction (along the
fibers). This is further proven by lack of a noticeable difference in tensile strength in the cross
direction since, as discussed, this is a measure of bonds between the individual fibers.
In the Elmendorf tear test, fabrics tear much easier in the machine direction since the tear
will propagate along the length of the fibers. In the cross direction however, the tear goes
through the fibers and therefore there is much more resistance. In the case of the Achieve web
vs. the Escorene web, we find that the Escorene, while being the thinner fabric, was much more
resistant to tearing in the cross direction than the Achieve web. This once again may be due to
the Escorene having shorter polymer chains and as the tear propagates in the cross direction it
will have a much less linear pathway as it diverges more frequently, between polymer chains.
When weight loss under high temperatures was tested, both Escorene and Achieve (resins
and webs) performed about the same. As can be seen in table and graph below, both resins
(pellets) lost around 99% of their weight, beginning at around 300 ᴼC. The nonwoven webs
perform very slightly different losing slightly less weight at slightly higher temperatures. As we
can see from the graph all samples loss their weight very quickly once reaching the threshold.
Table 6. TGA Data for Escorene and Achieve
Initial Weight Weight Weight Loss Onset
(mg) Loss % (mg) (ᴼC)
Escorene 7.26 -99.0% -7.20 309
Pellets
Achieve 7.39 -99.3% -7.34 290
Pellets
Escorene 7.59 -97.8% -7.43 304
Web
Achieve 7.31 -97.2% -7.11 326
Web

10. Figure 15. TGA Curve for Escorene and Achieve
( Temperature ᴼC along horizontal axis; % Weight along vertical axis)
Table 7. Web Properties of Achieve Variants
Air Perm
Fiber Diam. (µM) Thickness (mm) (cfm)
Mean 2.28 1.31 24.59
PC1
Std. Dev. 0.67 0.07 0.89
Mean 1.95 0.89 19.46
PC2
Std. Dev. 0.4 0.06 0.94
Mean 2.28 0.96 25.61
PC3
Std. Dev. 0.75 0.03 1.18

11. 10 15
Measurements
Measurements
10
5
Per 30
Per 30
5
0 0
1 1.5 2 2.5 3 3.5 4 1 1.5 2 2.5 3 3.5 4
Diameter (μm) Diameter (μm)
Figure 16. PC1 Fiber Diam. Distribution Figure 17. PC2 Fiber Diam. Distribution
10
Measurements
5
Per 30
0
1 1.5 2 2.5 3 3.5 4
Diameter (μm)
Figure 18. PC3 Fiber Diam. Distribution
The only differences between the three Achieve webs are processing conditions. Namely
PC1 was processed at an air pressure of 10 psi while the other two were processed at 5 psi; and
PC3 was processed with a DCD of 35 cm while the other two webs were processed with a DCD
of 20 cm. Since all three webs are the made of the same resin, the fibers should therefore be the
same density. The drop in air pressure between PC1 and PC2 (10 to 5 spi) seems to have
produced a smaller fiber diameter and therefore a thinner fabric. However the PC3 was also
processed at 5 psi yet produced the same fiber diameter as the PC1. This is interesting since it
would seem that the DCD, having to do with the process after the die, would not affect fiber
diameter. No web was as thick as the PC1 at 1.31 mm nonetheless. While the thinnest, the PC2
was the least permeable, which implies that the smaller fibers packed more closely creating a
denser, thinner fabric.

12. 3500
3000
2500
2000
Load (gms) PC1
1500 PC2
PC3
1000
500
0
0 0.1 0.2 0.3 0.4 0.5
Elongation (in)
Figure 19. Load vs. Elongation in MD for Achieve Web variants
2000
1800
1600
1400
1200
Load (gms) 1000 PC1
800 PC2
PC3
600
400
200
0
0 0.1 0.2 0.3 0.4 0.5 0.6
Elongation (in)
Figure 20. Load vs. Elongation in CD for Achieve Web Variants

13. Table 8. Tensile and Tear Properties of Achieve Web Variants
Peak Elongation (% Modulus Elmendorf
Polymer Peak Load (gms) in) (gms/in²) (cN)
Mean 619.7 8.39 347,856 68.6
PC1 Std.
Dev. 17.3 0.80 18,948 6.6
Mean 877.0 3.90 1,137,186 68.6
Cross Direction PC2 Std.
Dev. 29.6 0.34 42,429 6.6
Mean 1732.4 16.02 1,298,194 53.1
PC3 Std.
Dev. 56.4 1.89 42,891 5.5
Mean 2019.9 5.28 1,841,227 49.4
PC1 Std.
Dev. 244.7 0.51 113,385 11.9
Mean 2758.9 3.04 3,576,177 40.7
Machine Direction PC2 Std.
Dev. 147.8 0.13 141,961 4.6
Mean 2338.5 11.97 2,079,719 55.6
PC3 Std.
Dev. 402.0 2.44 279,292 4.2
As we can see from the graph and table, the PC3 web had the most tensile strength and
stiffness in the cross direction. This is most likely due to the increase in the distance from die to
collector the fibers tend to become more entangled and randomly laid creating more resistance to
the individual fibers breaking apart from one-another. The fibers in the PC3 web being more
randomly laid means that the direction of the fibers did not as often lie in the direction of the
collector belt. This means that the properties in the cross and machine direction are going to be a
lot closer together than when compared with PC1 and PC2 webs (which were processed at
shorter DCD’s). Unusually the PC2 web was the strongest and stiffest in the machine direction.
This is most likely due to the better bonding between the “thinner” fibers, which were more
densely packed (see air permeability of PC2 web). Surprising these more densely packed fibers
were not more resistant to tearing in the cross direction than the other webs. The PC3 also, while
having the greatest tensile strength in the cross direction was not as resistant to tearing as the
other webs. This may show that there is a correlation between the Young’s Modulus (stiffness)
and the tear resistance; as the webs that were the stiffest tended to tear the easiest.

14. Conclusion
When melt blown under the same processing conditions the Achieve resin produced a
web that was stronger, had a higher elastic modulus, and was slightly less dense. This is largely a
result due to the lack of peroxide, which the Escorene resin contains. The TGA showed that both
Escorene and Achieve resins (and webs) lose the majority of their weight at around 300 ᴼC.
After running the Achieve resin under three different processing conditions we found that
decreasing air pressure produces a stronger and stiffer nonwoven web. We also found that
increasing the DCD distance produces a web with fibers more entangled and more laid in more
random directions. This in turn produces a web that is comparable in both machine and cross
direction.
References
1. Dr. Lee, Youn Eung and Dr. Wadsworth, Larry C. “Process Property Studies Of Melt
Blown Thermoplastic Polyurethane Polymers For Protective Apparel” Knoxville, TN:
University of Tennessee Department of Materials Science and Engineering, 2005. Print.
2. Kotra, Ramaiah and Rong, Haoming. “Melt Blown Technology” Knoxville, TN:
University of Tennessee Department of Materials Science and Engineering, 2004. Print.
3. ASTM Standard D5734, 2001, "Standard Test Method for Tearing Strength of Nonwoven
Fabrics by Falling-Pendulum (Elmendorf) Apparatus," ASTM International, West
Conshohocken, PA, 2003, DOI: 10.1520/C0033-03, www.astm.org.