hipo impact mod tpoconf2003 williams

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New Low-Density EXACT

Plastomers as High Performance Impact

Modifiers

M.G. Williams, B.A. Harrington, and T.M. Miller

Ethylene ElastomersExxonMobil Chemical

5200 Bayway Drive, Baytown, TX 77520

INTRODUCTION

In the early 1990's, metallocene based ethylene- olefins plastomer products were

commercialized and supplied as free-flowing pellets. These products were quickly accepted for

utilization into many end-uses due to their unique properties. ExactPlastomers, supplied

commercially by ExxonMobil Chemical, are metallocene based ethylene-butene, ethylene-hexene,

and ethylene-octene copolymers that enhance the toughness, clarity and sealing performance of film

and flexible packaging materials. They also add impact strength and flexibility to molded, extrudedand calendered products including automotive parts, tubing, sheeting, containers, and wire and

cable insulation. Currently, one of the largest applications for metallocene plastomers is in the area

of polypropylene modification. In polypropylene modification, the major application is in the area

of automotive TPOs. Over the past decade, metallocene plastomers have found wide commercial

use in many automotive TPO applications such as automotive bumper fascia, body side molding,

and interior trims.

Thermoplastic Olefins (TPOs) are mainly immiscible blends containing a dispersed phase of a

polyolefin elastomer with isotactic polypropylene. Depending on the process or application, the

TPO compound will possess a desired property balance of stiffness, melt-flow, and toughness.

Within these attributes, it is particularly important to have high impact strength at sub-ambient

temperatures. Numerous attempts at improving the performance of a TPO by improvements in theelastomer design have been described. The most notable of these are the use of amorphous

ethylene propylene (EP) polymers for favorable low temperature performance, the use of highly

branched EP(D)M terpolymers for the easy dispersion of the elastomer into very small particles1,

and the introduction of ethylene elastomers containing the comonomer octene instead of propylene

for a closer match of the solubility parameters of the two phases. Metallocene plastomers have

become the modifier of choice for automotive TPO compounds imparting the best overall balance

of key properties in a free-flowing pellet product form. As impact modifiers they also offer a host

of ancillary benefits including processibility, weatherability, paintability, and clarity2,3

. In addition,

performance requirements for automotive TPOs have established the use of lower-density (< 0.880

g/cc) plastomers in order to reach the desired balance of low-temperature impact strength with other

key properties, such as compound flow.

This paper will introduce several new Ethylene-Octene (EO) grades having improved TPO

modifier performance over ExxonMobil's current offerings. Currently, the Exact Plastomer

portfolio resides in the density region of 0.873-0.902 (g/cc). In this density region there are a

number of grades that are utilized as modifiers for automotive TPOs. Currently under development

are several new grades of metallocene EO plastomers in the density range of 0.860-0.870 (g/cc) and

a melt-index range of 0.50-5.0 (I2 at 190 C, dg/min). This paper will also provide some

characterization around these developmental plastomers and highlight their relative performance in

both homopolymer polypropylene blends and model impact copolymer (ICP) based TPO

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compounds. Performance attributes will focus on properties representing the initial screening

requirements for most TPO applications, that being the balance of impact, stiffness, and compound

melt-flow rate.

EXPERIMENTAL

Polyolefin modifiersThe polymer characteristics of the polyolefin elastomer modifiers are in Table 1. Two

series of modifiers are illustrated in this paper - plastomers that represent present commercial

offerings currently being utilized as TPO modifiers, and plastomers that still reside in the

developmental phases representing the main focus of this paper. Note that all of the developmental

plastomers carry the "PX" nomenclature and are presented in the Table 1 in bold text. In comparing

all the modifiers listed in Table 1, one notices several key property characteristics. First, a fairly

broad density range is represented (0.860-0.900 g/cc). Density changes between plastomer

modifiers are produced by varying the amount of comonomer in the polymer; the higher

comonomer content modifier having the lowest density. Also broadly represented by virtue of a

direct relationship with density will be the overall ethylene (C2) crystallinity of the modifiers, from

which many key physical and/or thermal properties are derived. Some of these derivative

properties are also shown in Table 1 (i.e. Tm, Flex Modulus, Shore A). The amount of C2crystallinity is calculated from heats of fusion measured by differential scanning calorimetry (DSC)

and normalizing with respect to the heat of fusion of crystalline PE. Second, most of the

commercialExact grades shown in Table 1 contain butene as the second monomer. Exact3035,

4041, 4042, and 4033 all contain butene as the comonomer. Exact8201 being the only included

commercial grade containing octene. All developmental PX grades contain octene as the second

monomer, and reside in a lower density region versus commercial Exact modifiers. Third, the

modifiers represented in Table 1 are characterized by melt indexes (I2 @ 190C) in the range of 0.5

- 5.0 (dg/min).

Polypropylenes and Talc

All polypropylene (PP) resins are grades produced by ExxonMobil. Homopolymers are

general-purpose or injection molding grades, while Impact Copolymers (ICPs) used are injectionmolding grades. The 35 MFR ICP contains greater than 6% ethylene, while the 80 MFR ICP

contains less than 6% ethylene. Melt flow rates of the PP resins are measured as grams per 10

minutes at 230 C and 2.16 kg load.

The grade of talc used in the talc-filled TPO experiments was Cimpact 610, a non-surface-

treated micronized talc, with an average particle size of 3m, produced by Luzenac America.

Blending and specimen preparation

ThermoPlastic Olefin compounds featuring ethylene-butene (EB) and ethylene-octene (EO)

modifiers were compounded in a 30 mm ZSK twin-screw extruder. Typical polypropylene

extrusion conditions, with extruder melt temperature set at 230 oC. The compounds were pelletized

and injection molded into test specimens.

Sample pellets were injection molded into test specimens using a 75-ton Van Dorn

injection molding machine using standard PP molding conditions.

Mechanical Testing

Mechanical properties such as notched izod impact strength (ASTM D 256, Method A),

flexural modulus (ASTM D790 Method A) and melt flow rate (ASTM D1238, Condition L) were

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obtained from 3.2 mm thickness injection molded test samples. Notched izod impact strength at low

temperature was measured by cooling a test sample in a freezer set at varying sub-ambient

temperatures for 1 hour, and testing at room temperature before any significant warming can occur

in the specimen.

Multi-axial tests were performed at -30 oC and -40 oC using a Dynatup instrumented impact

tester fitted with an environmental chamber and cooled using liquid nitrogen. The specimens wereconditioned for 24 hours at either -30

oC or -40

oC prior to testing. This test consists of puncturing a

cylindrical test specimen (152 mm diameter, 3.2 mm thickness) with a falling weight fitted with a

20.3 mm hemispherical striker. Both the weight of the striker and the velocity with which it strikes

the specimen can be adjusted. The striker normally loses about 10 % of its impact velocity while

passing through the sample. A minimum of 5 samples was tested for each condition.

Blend Morphology and image analysis.

The morphology of the polymer blend was determined using Atomic Force Microscopy

(AFM) using thin sections from the geometric center of instrumented impact disc specimens.

The development of AFM has provided a new tool for examining polymer morphology

down to nanometer resolution. The capability of AFM has been greatly enhanced by the forcemodulation technique, which uses differences in storage modulus for image contrast

4,5. When used

in conjunction with cryogenic facing or sectioning (a common sample preparation step), the force

modulation technique provides excellent phase contrast between the polypropylene matrix polymer

(hard phase) and the impact modifier (soft phase), that differ substantially from each other in elastic

modulus. This type of morphological examination eliminates the tedious etching, staining, and

cryo-sectioning procedures typically required in transmission electron microscopy.

Particle size distribution was obtained from the AFM images using the Adobe Photoshop

5.0 image analysis program. This program differentiates the dispersed particles from the matrix

using a binary contrast, and provides the area fraction, equivalent diameter (dn), major/minor axis

(aspect ratio), and particle orientation. Higher moments of the particle size distribution such as

weight average particle diameter (dw) and the volume average particle diameter (dv)

dw = (ni dni )2 / (ni dni)

dv = (ni dni )3 / (ni dni)

2

were calculated from dn and number of particles (n).

Rheological analysis. Rheological analysis was conducted on the metallocene plastomer modifiers and the 80

MFR impact copolymer polypropylenes in order to measure dynamic viscosity, ' as a function of

frequency at 190 C. Measurements were made on Alpha Technologies Rubber Processing

Analyzer model 2000. The experiments were performed in a dynamic mode in parallel plate

geometry at a strain of 14%. The ' of both plastomer and polypropylene at 190 C were measuredin order to calculate viscosity ratio, p100. P100 is defined as 'd /'m at a 100 rad/s frequency, where

'd is defined as the dynamic viscosity of the dispersed phase (metallocene plastomer) and 'm is

defined as the dynamic viscosity of the PP matrix.

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RESULTS AND DISCUSSION

Homopolymer PP Formulations.

Evaluation of the commercial Exact

Plastomers in both 5 MFR and 35 MFR PP

homopolymer blends was conducted in order to establish a performance baseline. All

homopolymer formulations were blended at a PP/modifier ratio of 70/30 wt. %. This baseline

represents ExxonMobil's more popular current offerings for TPO modification and establishescomparative data for evaluation of the low-density octene plastomers under development in more

difficult to modify homopolymer systems. Table 2 shows the key performance data of the

commercialExactmodifiers in a TPO formulation containing a 5 MFR PP homopolymer matrix.

Within Table 2 one will notice that only two modifiers offer both no break failure mode at room

temperature during notched izod impact testing and ductile failure mode at both -30 C and -40

C during Dynatup impact testing. Exact4033 (0.880 g/cc, 0.8 dg/min) and Exact8201 (0.882

g/cc, 0.5 dg/min) impart much better impact properties than the other three commercial modifiers.

The radar chart shown in Figure 1 depicts clearly the benefits of using a modifier having a

combination of relative low-density and low melt-index when modifying 5 MFR homopolymer PP.

Table 3 illustrates the same key property data for formulations based on 35 MFRhomopolymer PP. All modifiers highlighted in Table 3 exhibit complete break failure mode during

notched izod impact testing at 23 C. However, both Exact 4033 and Exact 8201 provide the

highest instrumented impact total energy versus the other three modifiers. This can be seen clearly

in the radar chart in Figure 2. Again, as with the 5 MFR homopolymer blends, the same relative

combination of low modifier density and high molecular weight (i.e. low MI) yields the highest

level of low-temperature toughening in a 35 MFR PP homopolymer matrix. This is further

supported by the fact that Exact4041, which has the lowest density of the commercial grades at

0.878 (g/cc), imparts the highest room temperature notched izod resilience. However, due to its

relatively low molecular weight, one observes much lower multi-axial impact relative to the higher

molecular weight modifiers. Again, the highest level of impact performance when toughening

homopolymer PP between 5-35 MFR seems to arise from modifiers with a combination of lower

density and lower melt index (i.e. higher molecular weight).

Because of its overall performance in the homopolymer PP blends, and due to its

widespread commercial utilization as an impact modifier for polypropylene, Exact 4033 will be

used throughout this report as the control when comparing the performance of the developmental

low-density octene plastomer grades.

The key property data for the developmental PX EO plastomers in a 5 MFR homopolymer

PP are listed in Table 4. Note that Table 4 also includes the Exact 4033 data for comparative

purposes. One should notice immediately the higher notched izod impact values at lower

temperatures with the lower-density octene modifiers. Generally speaking, lower density gives riseto lower modifier crystallinity and lower glass-transition temperatures (Tg), which translates

directly into specific composite properties such as lower modulus and higher levels of toughening

at sub-ambient conditions. In Figure 3, which is a radar chart where all values have been

normalized to the control Exact4033 modifier, one can clearly see that the same combination of

relative low density and low melt index gives rise to higher levels of impact enhancement. In this

instance PX-5062 at 0.860 (g/cc) and 0.5 (dg/min) imparts the highest room temperature notched

izod impact, while providing ductile failure modes down to -40 C during Dynatup impact testing.

One will notice that all the lower density octene modifiers provide notched izod values between

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20% and 80% higher than higher density Exact 4033 with the exception of PX-5371. PX-5371

and PX-5171 have the same density at 0.870 (g/cc); however, they differ in melt index. PX-5171has a melt index of 1.0 (dg/min), while PX-5371 has a melt index of 5.0 (dg/min). As established

earlier when looking at the commercial Exact grades in the 5 and 35 MFR homopolymer

formulations, modifier melt index is a relatively important property when toughening PP. Higher

molecular weight modifiers generally contain higher levels of chain entanglements, yielding greater

levels of cavitation. Cavitation is a normal mechanism examined in TPOs for impact energyabsorption. This difference shows up in Figure 3 when comparing PX-5371 to PX-5171 in both

room temperature notched izod (RTNI) and -40 C Dynatup impact. PX-5171 has a RTNI value

approximately 25% higher than that of PX-5371. Also, note that the -40 C Dynatup total energy

value for PX-5371 is only 65% of the incumbent control, which has a higher density.

During TPO compound development, enhancement of one key property usually comes at

the sacrifice of another. In general, impact enhancement of PP is attained at the expense of

compound melt flow and stiffness. Though modifier density will have an effect on the composite

flexural modulus, this compound property will be established primarily by the polypropylene used

and the modifier level. At least within the density range discussed here. Since the comparative

data sets highlighted within this paper occur at the same modifier treat level, flexural modulus

values in a given data set between modifiers will not vary greatly.

Figure 4 represents notched izod impact versus temperature for the developmental

plastomers in the 5 MFR homopolymer PP formulation. This graphic allows us to quickly observe

the effect of both modifier density and melt index on the TPO ductile-brittle-transition temperature

(DBTT). The DBTT, where the failure mode transitions from no-break (ductile) to complete-break

(brittle), is again generally lower for the lower density developmental modifiers. It seems also that

the same general trend is seen in this graph as the lower-density and lower melt-index modifiers

give rise to higher levels of toughening, which is delineated by lower DBTT. PX-5062, with the

lowest density and MI combination, has a DBTT of approximately -15 C versus the commercial

control at approximately 0 C. To see the effect of modifier MI, observe the PX-5171 and PX-5371

trend lines in Figure 4. Recall, PX-5171 and PX-5371 are both 0.870 (g/cc) density plastomers.

They differ only in melt index, to which PX-5171 has a melt index of 1.0 (dg/min) and PX-5371has a melt index of 5.0 (dg/min). Notice the point both on the graph where both modified

compounds reach the ductile-brittle transition. From this one can estimate that PX-5171 has a

DBTT between -2 C and +3 C, whereas the higher MI PX-5371 has a DBTT between +9 C and

+14 C.

Table 5 lists the key property data for the very difficult to modify 35 MFR homopolymer

PP. Again, one will notice a general trend of higher notched izod impact with the lower density

developmental grades. The radar chart in Figure 5 shows the key property profile. In the 35 MFR

formulation it seems as though the most favorable balance of properties is afforded via PX-5361,

which has a relatively low density at 0.860 (g/cc) and a mid-level melt index of 3.0 (dg/min). The

most favorable balance of properties is defined here as the highest level of toughening available at

the highest compound melt flow rate and the highest compound stiffness. Due to the graphicresolution of Figure 5, it is very difficult to see performance differentiation of the modifiers when

looking at -40 C Dynatup data. Figures 6 and 7 attempt at highlighting the real differences

between the higher density control and the lower density developmental plastomers. A typical

instrumented impact test output is shown in Figure 66. The force versus distance data are integrated

to provide the total energy needed to break the specimen. In addition, the shape of the curve

provides information about the failure mode. If the force trace drops nearly vertically from its

maximal value, brittle failure occurs. If the force trace is elongated, ductile failure occurs. A

"ductility index" (DI) can be computed:

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DI = {(total energy - yield energy) / yield energy} x 100

Total energy represents the total area under the force-distance curve. Yield energy in the area under

the portion from the start of the experiment to the point of maximal force. As a rule of thumb, a DI

less than 45% represents brittle failure. In many cases it is necessary to report both the total energy

and ductility index to characterize impact strength in the instrumented impact test. Figure 7graphically illustrates the DI for all of the developmental grades in addition to two commercial

Exact grades. It is clear from this chart that there exists significant differentiation among the

modifiers shown as the lower density modifiers again impart the highest level of toughening at low

temperatures. PX-5062, PX-5361, and PX-5061 are the only three that show clear ductile failure at

-40 C. PX-5171 can be characterized as being within the ductile-brittle transition region. That is,

some specimens failed ductile, while others specimens tested were observed having failure modes

other than ductile. Again, the lowest DI was yielded by PX-5371, which again exposes the effect of

melt index.

Impact Copolymer PP Formulations.

TPO compounds were also formulated using Impact Copolymer (ICP) polypropylene as the

base resin and talc as a filler. Specifically, two ICP resins were utilized differing both in melt flowrate (I2 at 230 C) and ethylene content. Both model compounds were designed to provide data

associated with a "typical" talc-filled TPO for an injection molding process and can be seen in

Tables 6-9 along with respective key property data. Table 6 highlights data associated with the 35

MFR ICP formulation for commercial Exact

products. Again, testing and data collection for the

commercial Exact grades was completed to establish a baseline for comparison. As with the

homopolymer data discussed in the previous section, the 35 MFR ICP performance trends are

similar in that both Exact4033 and Exact8201 provide the best overall balance of key properties

versus the other commercial grades evaluated. Note however that brittle failure was observed for

-30 C Dynatup within all formulations emphasized in Table 6. For this reason the -40 C data was

not collected. Table 7 shows the ICP formulation as well as key property data for commercial

Exactgrades within an 80 MFR ICP recipe. In general, all the commercial plastomers evaluated

are relative poor performers due to observed notched izod values below the ductile-brittle transitionand brittle failure during Dynatup testing. One noteworthy item however is described within the

Exact4041 (0.878 g/cc, 3.0 dg/min) formulation. It is here that one observes a RTNI within the

ductile-brittle transition and a -30 C Dynatup value much higher than the other commercial grades

evaluated within this formulation. This is a different trend observed in prior homopolymer

formulations or within the 35 MFR ICP formulation. Notice that Exact4041 does not have the

relative combination low modifier density and low MI established as necessary modifier properties

in the prior recipes. It seems that possibly a higher modifier MI may be a benefit in significantly

enhancing the impact properties of a much higher MFR matrix. This deviation from the trend will

be discussed further during evaluation of the developmental low-density octene grades in

subsequent paragraphs.

When assessing the data described in Table 8 one will notice higher levels of tougheningavailable to the 35 MFR ICP when utilizing the developmental metallocene plastomers as

modifiers. Higher notched izod values at lower temperatures as well as some Dynatup ductile

failure modes down to -40 C are observed with the lower density octene modifiers without

adversely affecting other key properties. PX-5062 and PX-5361 both offer the highest level of

toughening. This is not surprising given both are characterized by the lowest density at 0.860

(g/cc). A quick glance at the notched izod data, one will notice a clear trend with modifier density.

The lower the density, the lower the DBTT. Generally, the lower the DBTT, the higher the impact

enhancement imparted by the modifier. This is shown graphically in Figure 8. Figure 8(a) graphs

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modifier density versus ductile-brittle-transition temperature for the 35 MFR ICP formulations.

The DBTT was estimated by plotting notched izod versus temperature (-40 C - RT) for each

modifier tested. From Figure 8(a) one can clearly see a strong relationship between modifier

density and DBTT. In contrast, Figure 8(b) plots modifier melt index versus DBTT, which shows

very little relationship as depicted by a flatter trend line with larger variation in the data.

Table 9 highlights the same data set within the 80 MFR ICP formulation. The data trendsrepresented here depart slightly from those established in the 35 MFR ICP. By looking at the data

listed in Table 9, one may notice the performance advantage that the higher MI modifiers seem to

afford. Both PX-5371 and PX-5361, which have melt indexes of 5.0 (dg/min) and 3.0 (dg/min),

respectively, offer the highest level of toughening. Unlike previous formulations, there seems to be

less dependency on modifier density in the higher flow matrix. Figure 9 plots DBTT versus

modifier density for all modifiers evaluated. In Figure 9 one can see that within the modifier

density range discussed in Table 9 (0.860 - 0.870), the trend line becomes relatively flat with

significant scatter in the data. This signals less of an impact relationship with density in this density

range. It is not until the modifier density becomes greater than approximately 0.875 (g/cc) does one

begin to see the trend line significantly increase. One will notice by scanning the notched izod data

in Table 9 that PX-5361 gives much better overall impact performance than does PX-5062. Both

modifiers offer the same density of 0.860 (g/cc), differing only in melt index. PX-5062 has a melt-index of 0.5 (dg/min), while PX-5361 has a MI of 3.0 (dg/min). One possible explanation offering

higher performance is the development of morphologies more conducive for toughening the matrix.

As a rule of thumb, sub-micron particle size is necessary to provide suitable low-temperature

impact7. In most cases, it has also been shown that higher levels of performance can be attained via

a combination of small average particle size and narrow particle size distribution. Asar et al.

observed in ethylene-propylene-diene terpolymers / polypropylene (EPDM / PP) blends that local

variations in EPDM concentration and domain sizes can result in a two-fold difference in the total

energy absorbed during impact8. There are a few polymer parameters of importance when trying to

control particle dispersion and TPO morphologies. They are briefly: composition, viscosity and

elasticity ratios, shear stress/shear rate, and interfacial tension9. In an attempt to better explain the

impact enhancement mechanism in the ultra high flow matrix established by the 80 MFR ICP,

attention will focus on viscosity ratio. Viscosity ratio was defined earlier as p100 = 'd /'m at 100rad/s, measured at 190 C. Figure 10(a) and Figure 10(b) both plot DBTT, compound MFR, and

flexural modulus versus p100 inorder to illustrate property trends as well as key property balances.

Figure 10(a) depicts the impact-flow balance. In Figure 10, one can see a clear relationship

between p100 and DBTT. In this case, higher p100 equates to higher DBTT's or less impact

enhancement of the PP. It has been widely reported that at relatively low viscosity ratios, the

elastomeric particle becomes highly deformed during melt flow. If enough melt elasticity exists

within the elastomeric modifier, the highly deformed particle will break-up into small particles.

This stated mechanism requires a relatively high level droplet deformation, which within the 80

MFR ICP formulations seems to be dependent on a low viscosity ratio (p100 < 5-6). One will also

notice in Figure 10(a) that compound MFR is inversely proportional to p100. This makes sense since

in many cases a higher p100 signals higher modifier molecular weight. According to the graph

depicted in Figure 10(a), if high impact properties at the highest flow balance is desired, one shouldstrive for a low viscosity ratio to attain both the highest level of impact performance along with the

highest compound flow.

Figure 11 attempts to support the previous claim with regards to impact modification of the

80 MFR ICP by displaying morphologies PX-5062 and PX-5361 within the 80 MFR ICP. Figure

11(a) is a simple bar chart graphing RTNI of both PX-5062 and PX-5361, which again are

modifiers having equal density of 0.860 (g/cc). Notice the superior performance afforded by PX-

5361. In addition, Figure(s) 11(b) and (c) show the associated AFM morphologies. It is easy to

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differentiate visually between the two morphologies as the higher performing PX-5361 seems to be

more highly dispersed within the PP matrix.

Table 10 presents the particle size analysis of both PX-5062 and PX-5361 in the 80 MFR

ICP formulation. In both cases the average particle size is below 1m. Though analysis of the PX-

5361 blend shows a smaller dn by approximately 32% versus the PX-5062 blend. Possibly more

important than dn are substantial reductions in dw and dv in the PX-5361 formulation, whichcharacterizes a reduction in larger particles. The absence of the large particles can be beneficial

from the standpoint of mitigating coalescence of the dispersed phase.

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CONCLUSION

In conclusion, it has been demonstrated that new low density ethylene-octene metallocene

plastomers currently being developed for commercialization are much more effective in impact

toughening polypropylene homopolymers and impact copolymers as compared to commercial

plastomer grades currently offered by ExxonMobil. Substantial benefits in low temperature

toughness through a lowering of the ductile-to-brittle transition temperature, while maintainingother properties, are realized in all TPO formulations when utilizing the low-density octene

developmental grades. In general, when evaluating modifiers at similar treat levels, modifier

density has the largest effect on TPO impact properties. This is especially true when very low-

temperature ductility is required. When modifying homopolymer PP having melt flow rates

between 5 (dg/min) and 35 (dg/min), lower modifier density in combination with lower modifier

melt index affords the highest level of toughening. The same can be said when modifying a high

impact ICP within a similar melt flow range. In substantially higher flow matrices, such as the 80

MFR ICP analyzed, it would seem that TPO impact performance depends more on rheological

responses of the blend components during melt compounding than in the lower flow systems.

Viscosity ratio was shown to play an important role in developing morphologies more favorable for

impact enhancement.

By extending the current metallocene plastomer grade offerings to include low-densityoctene copolymers, ExxonMobil can now offer customers much higher performing modifiers for

their TPO compounds. Having grades that offer low densities of varying melt indexes provides the

TPO Customer with the flexibility to choose the right plastomer that will impart the required

balance of properties.

ACKNOWLEDGEMENTS

The authors are grateful to Kathy Cabrera, Tim Alford, Kelli Dettor, and Lori Trenery for

preparation and testing of all formulations and to Margaret Ynostroza for the AFM micrographs.

Also the authors are grateful to ExxonMobil Chemical for allowing us to publish this paper.

REFERENCES

1. Dharmarajan, N. and Kaufman, L.G. , High Flow TPO Compounds Containing BranchedEP(D)M Modifiers, Proceedings of Rubber Division, American Chemical Society, Cleveland,

OH (1997).

2. Shaman, L.M., Plastics Technology, 46 (1994).

3. Steininger, F.J., Proceedings of the First International Metallocene Conference, Chicago(1997).

4. Maivald, P., et. al.,Nanotechnology 2, 103 (1991).

5. Overney, R.M., "Procedures in Scanning Probe Microscopy," Wiley Publishing (1995).

6. Yu, T.C., Impact Modification of Polypropylenes, Proceedings of Society of Plastics EngineersAnnual Technical Conference, San Francisco, pp. 2439-2445 (1994).

7. Yu, T.C.,Handbook of Polypropylene and Polypropylene Composites, 2nd Edition. New York:Marcel-Dekker (2003), p. 244.

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8. Asar, H.K., Rhodes, M.B., and Salovey,Adv. Chem. Serv., 176, 489 (1979).

9. Favis, B.D. and Chalifoux, J.P., The Effect of Viscosity Ratio on the Morphology ofPolypropylene/Polycarbonate Blends During Processing, Reprint from Polymer Engineering

and Science, p. 1592.

2003 Exxon Mobil Corporation. To the extent the user is entitled to disclose and distribute this document,

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TABLE 1:

METALLOCENE PLASTOMER MODIFIERSExxonMobil Chemical Company Data

Grade

Density

(g/cc)

MI (I2)

@190oC

(g/10min)

Comonomer

(Type)

MIR

I21/I2

@190C

ML (1+4)

@125oC

(MU)

Crystallinity

(%)

Tm

(

o

C)

Flex Mod

1% Sec

(MPa)

Hardnes

(Shore AExact3035 0.900 3.5 Butene 17 7 39 88 70 92

Exact4041 0.878 3.0 Butene 17 10 22 60 17 81

Exact4042 0.899 1.1 Butene 17 19 38 86 71 91

Exact4033 0.880 0.8 Butene 17 27 18 60 24 82

Exact8201 0.882 1.1 Octene 28 17 19 68 29 81

PX-5061 0.868 0.5 Octene 35 28 11 55 9 69

PX-5171 0.870 1.0 Octene 29 22 12 57 13 70

PX-5371 0.870 5.0 Octene 35 8 14 59 11 72

PX-5062 0.860 0.5 Octene 35 31 10 39 5 53

PX-5361 0.860 3.0 Octene 35 11 9 36 4 51

TABLE 2:

TPO FORMULATIONS COMPARING EXACT MODIFIERS >0.875 (g/cc) DENSITY

5 MFR HOMOPOLYMER POLYPROPYLENEExxonMobil Chemical Company Data

ModifierExact

3035

Exact

4041

Exact

4042

Exact

4033

Exact

8201

PP Homopolymer (5 MFR)

Modifier

Irganox 1010

70

30

0.2

70

30

0.2

70

30

0.2

70

30

0.2

70

30

0.2

Notched Izod Impact21 o C

0o

C-18 o C

-30o

C

-40o

C

(J/m)149.4

30.925.6

20.3

14.4

346.7

85.353.3

26.7

12.8

45.3

22.918.1

13.3

12.8

520.1

282.7

64.0

53.3

35.7

320.0

560.1

80.0

64.0

42.7

Dynatup Impact Total Energy

-30 oC (6.6 m/s, 11.4 kg)

-40 oC (3.3 m/s, 22.8 kg)

(J)

6.9

3.5

31.7

15.2

23.6

3.5

43.7

49.9

39.3

40.7

Flexural Modulus, 1% Secant (MPa) 927.3 874.9 920.5 915.6 1020.4

Melt Flow Rate @ 230 oC (g/10 min) 6.2 6.1 4.5 3.7 4.0

11


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TABLE 3:


35 MFR HOMOPOLYMER POLYPROPYLENEExxonMobil Chemical Company Data

ModifierExact3035

Exact4041

Exact4042

Exact4033

Exact8201

PP Homopolymer (35 MFR)

Modifier

Irganox 1010

70

30

0.2

70

30

0.2

70

30

0.2

70

30

0.2

70

30

0.2

Notched Izod Impact

21o

C

0 o C

-18 o C

-30o

C

-40o

C

(J/m)

38.4

21.9

20.3

15.5

12.3

94.4

34.1

23.5

18.7

13.3

45.3

22.9

18.1

13.3

12.8

48.0

32.0

26.7

21.3

16.0

53.3

48.0

41.6

26.7

15.5

Dynatup Impact Total Energy-30 oC (6.6 m/s, 11.4 kg)

-40 oC (3.3 m/s, 22.8 kg)

(J)3.3

3.3

20.6

12.1

16.1

7.1

38.0

35.6

27.1

10.8


Melt Flow Rate @ 230oC (g/10 min) 22.5 15.5 16.9 15.8 17.9

TABLE 4:

TPO FORMULATIONS COMPARING EO MODIFIERS


13/21

TABLE 5:

TPO FORMULATIONS COMPARING EO MODIFIERS 0.875 (g/cc) DENSITY

35 MFR IMPACT COPOLYMER POLYPROPYLENEExxonMobil Chemical Company Data

ModifierExact

3035

Exact

4041

Exact

4042

Exact

4033

Exact

8201

PP ICP (35 MFR, >6% C2)

Modifier

Talc (~3 d50)

Irganox 1010

64

21

15

0.2

64

21

15

0.2

64

21

15

0.2

64

21

15

0.2

64

21

15

0.2

Notched Izod Impact21 o C

0o

C

-18o

C

-30 o C

-40o

C

(J/m)252.0

59.2

29.2

22.1

16.0

466.5

198.4

68.3

50.4

29.6

416.2

82.7

36.9

24.9

16.0

563.9

365.6

100.3

64.0

47.2

632.9

314.5

61.9

41.6

32.0Dynatup Impact Total Energy

-30oC (6.6 m/s, 11.4 kg)

-40oC (3.3 m/s, 22.8 kg)

(J)

3.12

--

12.66

--

4.42

--

12.37

--

13.92

--


Melt Flow Rate @ 230oC (g/10 min) 20.1 19.2 16.9 14.3 16.3

13


14/21

TABLE 7:


80 MFR IMPACT COPOLYMER POLYPROPYLENEExxonMobil Chemical Company Data

ModifierExact3035

Exact4041

Exact4042

Exact4033

PP ICP (80 MFR,


15/21

TABLE 9:TPO FORMULATIONS COMPARING EO MODIFIERS


16/21

100

30

4025

900

Notched Izod @ 23C, J/m

Dynatup Total Energy @ -30C, J

Dynatup Total Energy @ -40C, JCompound MFR, dg/min

1% Secant Modulus, MPa

Ex4033 (0.880d,0.8MI, B)

Ex3035 (0.900d,3.5MI,B)

Ex4041 (0.878d,3.0MI,B)

Ex4042 (0.899d,1.1MI,B)

Ex8201 (0.882,1.1MI,O)

highest MI/lowest MW =Brittle Failure

600

40

457

1200

Notched Izod @ 23C, J




Ex4033 (0.880d,0.8MI,B)

Ex3035 (0.900d,3.5MI,B)

Ex4041 (0.878d,3.0MI,B)

Ex4042 (0.899d,1.1MI,B)

Ex8201 (0.882d,1.1MI,O)

Lower density/lower MI

Figure 1: Comparison of commercial Exact grades in TPO formulationscontaining 5MFR homopolymer PP. Modifier level = 30 wt.%.ExxonMobil Chemical Company Data

low density & low MI affords highest total energy

Figure 2: Comparison of commercial Exact

grades in TPO formulations

containing 35MFR homopolymer PP. Modifier level = 30 wt.%.ExxonMobil Chemical Company Data

16


17/21

1.8

1.8

1.81.8

1.8


Dynatup Total Energy @ -30C,



Ex4033 (0.880d,0.8MI,B)

PX-5061 (0.868d,0.5MI,O)

PX-5171 (0.870d,1.0MI,O)

PX-5371 (0.870d,5.0MI,O)

PX-5062 (0.860d,0.5MI,O)

PX-5361 (0.860d,3.0MI,O)

Lower Density / Lower MI

Higher MI

Figure 3: Comparison of PX grades vs. Exact

containing 5MFR homopolymer PP. Modifier level = 30 wt. %.

*All values normalized to Ex4033. ExxonMobil Chemical Company Data

4033 in TPO formulations

0

10 0

20 0

30 0

40 0

50 0

60 0

70 0

80 0

90 0

1000

-40 -30 -20 -10 0 10 20

Figure 4: Notched Izod Impact vs. Temperature. Showing DBTT of PX grades vs.

Ex4033 in 5MFR homopolymer PP formulations. Modifier level = 30 wt.%.ExxonMobil Chemical Company Data

30

Temperature (C)

PX-5061

(0.868d,0.5MI,O)

PX-5171

(0.870d,1.0MI,O)

PX-5371

(0.870d,5.0MI,O)

PX-5361

(0.860d,3.0MI,O)

PX-5062

(0.860d,0.5MI,O)

Ex4033 (0.880d,0.8MI,B)

Lower Density

DUCTILE

BRITTLE

17


18/21

3.5

3.5

3.53.5

3.5





Ex4033 (0.880d,0.8MI,B)

PX-5061 (0.868d,0.5MI,O)

PX-5171 (0.870d,1.0MI,O)

PX-5371 (0.870,5.0MI,O)

PX-5062 (0.860d,0.5MI,O)

PX-5361 (0.860d,3.0MI,O)

Lowest density and mid-MI (3.0) delivers highest RTNI. 20

...at the highest compound MFR

See figures 6,7

Figure 5: Comparison of PX grades vs. Exact containing 35MFR homopolymer PP. Modifier level = 30 wt. %.

*All values normalized to Ex4033. ExxonMobil Chemical Company Data

4033 in TPO formulations

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25

Displacement (mm)

F vs. D forDuctile specimen

F vs. D forBrittle specimen

Ductility Index (DI) = [(Etotal - Emax)/Etotal]x 100

Emax = Energy to Max Load

Specimen Shattered

Figure 6: Typical instrumented impact force-displacement curveExxonMobil Chemical Company Data

18


19/21

-40C Ductility Index

16.55

23.08

70

30

40

50

60

67.9265.32

63.38

50

36.01

DUCTILE

BRITTLE

20

10

0PX-5371Ex8201Ex4033PX-5171PX-5061PX-5361PX-5062

Figure 7: Ductility Index at -40C vs. Modifier in TPO formulations containing

35MFR homopolymer PP. Modifier level = 30 wt. %.ExxonMobil Chemical Company Data

19


20/21

-28.0

-18.0

-8.0

2.0

12.0

22.0

32.0

0.857 0.867 0.877 0.887 0.897

Modifier Density (g/cc)

-28.0

-18.0

-8.0

2.0

12.0

22.0

32.0

0.5 1.5 2.5 3.5 4.5 5.5

Modifier Melt Index (dg/min)

DBTT

(oC)

(a) (b)

Figure 8: (a) DBTT vs. Modifier Density; (b) DBTT vs. Modifier Melt Index in TPO

formulations containing 35MFR Impact Copolymer PP. Modifier level = 21 wt. %,Talc level = 15 wt. %.ExxonMobil Chemical Company Data

-20.0

0.0

20.0

40.0

60.0

80.0

100.0

0.858 0.868 0.878 0.888 0.898

Modifier Density (g/cc)

Figure 9: DBTT vs. Modifier Density in formulations containing 80MFR Impact

Copolymer PP. Modifier level = 26 wt. %, Talc level = 10 wt. %.ExxonMobil Chemical Company Data

20


21/21

-20.0

-10.0

0.0

10.0

20.0

30.0

40.0

3.2 5.2 7.2 9.2 11.2 13.2 15.2 17.2

Viscocity Ratio (p100) @ 190oC

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

DBTT

MFR

-20.0

-10.0

0.0

10.0

20.0

30.0

40.0

3.1 5.1 7.1 9.1 11.1 13.1 15.1 17.1

Viscocity Ratio (p100) @ 190oC

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

DBTT

Flex Mod

(a) (b)

Figure 10: (a) Impact/MFR Balance vs. Viscosity Ratio (p100) @ 190oC; (b) Impact/Stiffness

Balance vs. Viscosity Ratio (p100) @ 190oC in formulations containing 80MFRImpact Copolymer PP. Modifier level = 26 wt. %, Talc level = 10 wt. %.

ExxonMobil Chemical Company Data

(b)

(c)

PX-5062 (0.860d,0.5MI)

PX-5361 (0.860d,3.0MI)

100=6

p100=17

0 100 20 300 400 5 6000 00

Notched Izod Impact @ 23C (J/m)(a)

Figure 11: (a) RTNI comparison of PX-5361 & PX-5062 showing effect of viscosity ratio

(p100) in an 80MFR ICP formulation. (b) AFM micrograph of PX-4A in 80MFR I

formulation. (c) AFM micrograph of PX-5062 in 80MFR ICP formulation.

Modifier level = 26 wt. %, Talc level = 10 wt. %.ExxonMobil Chemical Company Data

hipo impact mod tpoconf2003 williams

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