Polypropylene - Building Blocks for Blown Film · PDF filePolypropylene - Building Blocks for...
Transcript of Polypropylene - Building Blocks for Blown Film · PDF filePolypropylene - Building Blocks for...
Polypropylene - Building Blocks for Blown Film Applications Spencer Hirata and Ganesh Nagarajan Basell USA Inc. ABSTRACT: A common question posed by many application and development engineers is “What type of film should I propose for my customer’s application?” When formulating a plan to answer this question, which often includes making a list of potential materials and structures, some materials may be overlooked or dismissed as potential candidates. Often this is the case for polypropylene when structures for blown film applications are developed. This is unfortunate because some interesting features and opportunities may be missed. Rather than focusing on the manufacturing techniques, structure or inherent properties of polypropylene this discussion provides examples that compare the properties of several blown polypropylene films. The experimental examples include the following: composition effects of two component blends, comparison of blends to co-extrusions, comparison of polypropylene and polyethylene co-extruded films, and an application example – making a clear, tough film. The goal of this paper is to provide sufficient incentive for applications and development engineers to reconsider PP for blown film applications. INTRODUCTION: A common question asked by film applications and development engineers is, “What type of film should I propose for my customer’s application?” While this seems to be a simple question, it is often complicated by the seemingly endless choices of materials and ways to combine them. Maybe a better way to phrase the question is, “What types of polymers should I consider and how should I put them together?” Under the pressure of limited resources and tight project timelines, an engineer will often not have time to consider all potential solutions and will begin with materials with which they are familiar. While this approach is acceptable, one may miss opportunities for differentiated solutions. For most people the terms blown film and polyethylene (PE) are almost synonymous. As a result, materials such as polypropylene (PP), more commonly associated with oriented and cast film applications, are often overlooked or dismissed from consideration. However, as the range of applications broadens and film property requirements become more differentiated, PE materials may not always provide the right balance of characteristics required. For these situations, PP materials may help provide unique solutions. When considering unfamiliar materials for their film applications, many engineers indicate that they would prefer comparative data based on “real” films. To demonstrate the utility of PP in blown film structures, a compilation of experiments completed on a small commercial sized line has been put together. Topics included are: the effect of blending two components in a monolayer film structure, comparison of two component blends to two component co-extruded film structures, comparison of PP and PE based co-extruded structures, and an example for making a clear, tough PP film. Experiment #1: Effect of Blending on Blown Film Properties When a single polymer does not provide the properties required for a blown film application, one often considers combining two or more polymers together. The objective is to maintain the best qualities of each polymer while minimizing less desirable properties. One of the most common methods is by making a pellet-pellet blend. For this example, two PP materials were considered for blend modification. One is a 1.2 MFR homopolymer polypropylene (HPP) and the other is a 0.45 MFR impact polypropylene copolymer (i-PPC). The materials selected as the second blend components are two highly modified impact PP copolymers, commonly referred to as thermoplastic polyolefins (TPOs). Although TPOs are often used alone, they are also very useful as blend
modifiers. A list of the materials used in this experiment is provided in Table 1-1 along with some standard material properties. Table 1-1: List of PP materials for blend experiment Material ID Description MFR 2.16 kg / 230 °C
(g/10 min) Flexural Modulus
(MPa) HPP Homopolymer PP 1.2 1420 i-PPC Impact PP copolymer 0.45 1200 TPO-A Thermoplastic olefin 0.65 400 TPO-B Thermoplastic olefin 0.6 80 A series of two component blends were made by tumble blending the pellets together at different ratios ranging from 0% to 100%. The blend combinations are listed in Table 1-2. Table 1-2: List of Blend Combinations Materials Modified with TPO-A Materials Modified with TPO-B HPP + TPO-A HPP + TPO-B i-PPC + TPO-A i-PPC + TPO-B Each of the blends were extruded and then blown into 0.001 inch (25.4 m) monolayer films. The bubble blow up ratio (BUR) used was 2:1. The process set up characteristics for the blown film line is provided in Table 1-3. Table 1-3: Process Set Up for Experiment #1 Extruder Name B Nominal Extruder Diameter 3.5 inch Screw L/D Ratio 30:1 Number of Heating Zones 5 Screw Type Single, Barrier Mixing Section Type Maddock Die Size 8 inch (203.2 mm) Die Lip Gap 0.080 inch (2.032 mm) Cooling Dual Lip Air Ring with Chilled Air Physical testing was completed for each of the film samples and summarized in the graphs, Figures 1-1 through 1-22. These tests included Elmendorf tear resistance, 1% secant modulus, tensile strength, falling dart impact, puncture resistance, haze, 45° gloss and heat resistance. Table A-2 in the Appendix provides a list of the test method references. Heat resistance is an internal test method used to determine the temperature in which the films would stick to each other. The graphs are presented in pairs, with properties of the TPO-A modified blends on the left side (odd numbered figures) and the TPO-B modified blends on the right side (even numbered figures). An overall summary of the comparisons is provided in table 1-4.
Figure 1-1: Figure 1-2: MD Elmendorf Tear Resistance
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Figure 1-3: Figure 1-4:
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Figure 1-5: Figure 1-6:
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Figure 1-7: Figure 1-8: TD 1% Secant Modulus
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Figure 1-9: Figure 1-10:
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Figure 1-11: Figure 1-12:
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Figure 1-13: Figure 1-14: Falling Dart Impact
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Figure 1-15: Figure 1-16:
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Figure 1-17: Figure 1-18:
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Figure 1-19: Figure 1-20: 45° Gloss
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Figure 1-21: Figure 1-22:
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Table 1-4: Summary - Effect of blending TPOs into HPP and i-PPC HPP i-PPC TPO-A TPO-B TPO-A TPO-B 1% Secant Modulus MD TD Tensile Strength MD — — TD — — — — Heat Resistance — Elmendorf Tear Resistance MD — — — — TD — — — Falling Dart Impact — Protrusion Puncture Resistance — — Haze — — — — 45° Gloss — — — — — no significant effect
small decrease , small increase large decrease, large increase
The most noticeable influence of blending the TPOs into the HPP and i-PPC materials was the reduction in the 1% secant modulus as the TPO weight percentage of the blend was increased. Although the TPO-A also affected the dart impact and heat resistance of the i-PPC, TPO-B exhibited a much greater impact on both blend combinations, resulting in a reduction of the films’ tensile strength and heat resistance while increasing the falling dart impact strength and protrusion puncture resistance. Also noticed was that the bubble stability of both the HPP and i-PPC materials improved as the TPO level increased. Experiment #2: Comparison of Blending to Co-extrusion in Blown Film Structures Another method used to combine materials is by creating multilayer structures. For blown films, the most common method is by co-extruding the different materials through a single die. In a simple 3 layer structure, this technique allows the creation of films with differentiated characteristics: a core layer material with a different skin layer material (ABA) or a core layer material with two different skin layer materials (ABC). So how do the properties compare to their pellet blend equivalents? In this experiment a series of two component structures were produced. One set of films were monolayer structures made from pellet-pellet blends while the other set were 3 layer, ABA co-extruded film structures. To keep the weight percentage of the co-extruded samples the same as their pellet blend counterparts (60% / 40%) the layer ratios were set at 30% - 40% - 30%. An example of the two film structures is provided in Figures 2-1 and 2-2 shown below.
Figure 2-1: Monolayer Film of Blend Figure 2-2: ABA Co-extrusion
30% i-PPC 60% i-PPC + 40% second component vs. 40% second component
30% i-PPC The primary material for this experiment was the same i-PPC used in experiment #1. The second component for each structure was selected from a set of materials which included 3 TPOs (each with a different flexural modulus), a linear low density polyethylene (LLDPE), a metallocene catalyzed linear low density polyethylene (mLLDPE), and a polyolefin elastomer (POE). A list of the materials is provided in tables 2-1 and 2-2. Table 2-1: Polyethylene materials used in blend vs. co-extrusion experiment Material ID Description MFR 2.16 kg / 190 °C
(g/10 min) Density (g/cc)
LLDPE LLDPE 1.0 0.918 mLLDPE mLLDPE 1.0 0.918 POE polyolefin elastomer 0.5 0.863 Table 2-2: Polypropylene materials used in blend vs. co-extrusion experiment Material ID Description MFR 2.16 kg / 230 °C
(g/10 min) Flexural Modulus
(MPa) TPO-A Thermoplastic olefin 0.65 400 TPO-B Thermoplastic olefin 0.6 80 TPO-C Thermoplastic olefin 0.6 20 The process set up characteristics for the blown film line is provided in Table 2-3. All films had a nominal thickness of 0.00354 inches (90 m) and were made with a bubble blow up ratio of 2:1.
Table 2-3: Blown Film Line Set Up Extruder Name A B C Nominal Extruder Diameter 60 mm 3.5 in 2.5 in Screw L/D Ratio 24:1 30:1 24:1 Number of Heating Zones 3 5 4 Layer Position in Co-extrusion Outer Core Inner Screw Type Single, Barrier Single, Barrier Single, Barrier Mixing Section Type Maddock Maddock Maddock Special Features Grooved Feed
Section
Die Size 11 inch (279.4 mm) Die Lip Gap 0.060 inch (1.524 mm) Cooling Dual Lip Air Ring with Chilled Air All the film structures and blends processed without difficulty. The physical properties of each film were tested and the data presented in graphs, Figures 2-3 through 2-12. This included Elmendorf tear resistance, 1% secant modulus, tensile strength, protrusion puncture resistance, falling dart impact, haze, and 45° gloss. Each graph shows the data for the blended monolayer structures as compared to the corresponding ABA co-extruded structures. Figure 2-3: Figure 2-4:
MD Elmendorf Tear Resistance
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LLDPE mLLDPE POE TPO-A TPO-B TPO-C
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i-PPC Blendi-PPC ABA Coex
TD Elmendorf Tear Resistance
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Figure 2-5: Figure 2-6:
1% MD Secant Modulus
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1% TD Secant Modulus
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Figure 2-7: Figure 2-8 : MD Tensile Strength
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Figure 2-9: Figure 2-10:
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Figure 2-11: Figure 2-12:
Haze
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45° Gloss
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i-PPC Blendi-PPC ABA Coex
For the purposes of this discussion, the focus is only the difference between the blend and co-extruded pairs, specifically which one provides the better performance. For all the properties listed except for haze, higher values are considered to be better. A summary of the observations is provided in Table 2-4. The numbers in the table represent the number of samples (out of 6) that favor either the blended monolayer or the ABA co-extruded structure. A check mark next to the values indicates the structure that showed an overall advantage.
Table 2-4: Summary - Comparisons of i-PPC blends to i-PPC co-extrusions Property No. of Samples Exhibiting Advantage Better i-PPC Blend i-PPC Co-extrusion Elmendorf Tear Resistance MD 2 4 TD 6 1% Secant Modulus MD 6 TD 5 Tensile Strength MD 3 3 TD 3 3 Falling Dart Impact 3 3 Protrusion Puncture Resistance 6 45° Gloss 5 1 Haze 1 5
- Higher value is considered to be better - Lower value is considered to be worse
6 - The number of samples (out of 6) that are considered to be better - advantage
The results show that some properties favor one structure over the other. For the co-extruded film structures, an advantage was seen for 1% secant modulus, haze and TD tear resistance while the monolayer films seem to provide better protrusion puncture resistance and 45° gloss. For other properties such as MD & TD tensile strength, falling dart impact, and MD tear resistance the mixed results indicate that the outcome is highly dependent on characteristics of the second component. Experiment #3: Comparison of Polypropylene and Polyethylene Co-extruded Blown Films After reviewing experiment #2 a commonly asked question is “How would LLDPE based co-extruded structures compare to those based on i-PPC?” To answer this, another set of structures were produced replacing the i-PPC with the LLDPE. The LLDPE films were made on the same blown film line using the same conditions. The film thickness remained at 0.00354 inch (90 m) and the BUR at 2:1. An example of the film structures being compared is provided in Figures 3-1 and 3-2.
Figure 3-1: i-PPC ABA Co-ex Figure 3-2: LLDPE ABA Co-ex
30% i-PPC 30% LLDPE 40% second component vs. 40% second component 30% i-PPC 30% LLDPE
The film properties tested included: Elmendorf tear resistance, 1% secant modulus, tensile strength, puncture resistance, falling dart impact, haze, and 45° gloss. The data is provided in the graphs, Figures 3-3 through 3-12. The first data set in each of the graphs compare the structures i-PPC / LLDPE / i-PPC and LLDPE / i-PPC / LLDPE.
Figure 3-3: Figure 3-4: MD Elmendorf Tear Resistance
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TD Elmendorf Tear Resistance
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Figure 3-5: Figure 3-6:
1% MD Secant Modulus
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Figure 3-7: Figure 3-8:
MD Tensile Strength
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Figure 3-9: Figure 3-10: Falling Dart Impact
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Figure 3-11: Figure 3-12:
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Table 3-1 provides an overview of blend vs. co-extrusion comparison. As in the previous experiment it lists a count of the number of samples exhibiting “better” properties.
Table 3-1: Summary comparisons of i-PPC to i-PPC co-extrusions Property No. of Samples Exhibiting Advantage Better i-PPC Co-ex LLDPE Co-ex Elmendorf Tear Resistance MD 1 5 TD 3 2 1% Secant Modulus MD 6 TD 6 Tensile Strength MD 6 TD 4 2 Falling Dart Impact 1 5 Protrusion Puncture Resistance 5 1 45° Gloss 6 Haze 6
- Higher value is considered to be better - Lower value is considered to be worse
6 - The number of samples (out of 6) that are considered to be better - advantage
The LLDPE based co-extruded structures provide advantages in MD tear resistance, haze, 45° gloss and dart impact resistance. The i-PPC based co-extruded structures provide advantages in MD & TD secant modulus and MD tensile strength as well as a slight advantage in puncture resistance. Experiment #4: Making a Clear, Tough Blown Polypropylene Film As seen in the earlier examples the optical properties of blown films made from standard PP materials are not very good, exhibiting high haze and low gloss. This would seem to exclude PP in applications requiring transparency and sparkle. Experiments were completed to address these deficiencies by incorporating a clarifying additive into the PP. An unmodified PP film and a PE film were produced as comparative control samples. The PE film structure selected is typically targeted for use in stand up pouch applications. The key properties reported for this application are low haze, high gloss, high modulus, high dart impact, high puncture resistance, high Elmendorf tear resistance, and high heat seal strength. Several types of PP were used in this example: an HPP (the same used in experiment #2), several random copolymers (r-PPC) and the TPO-B used in experiments #1, #2 and #3. The r-PPCs and TPO-B were included to improve the film’s tear resistance, dart impact and protrusion puncture resistance. The clarifying additive was added to each layer of the test samples to obtain the maximum effect. The materials used in this experiment are listed in Tables 4-1 and 4-2. Table 4-3 contains a listing of the film structures produced. The clarified film samples are identified as Sample #1, Sample #2 and Sample #3. Table 4-1: Polyethylene materials used in Clear PP Film Experiment #4 Material ID Description MFR 2.16 kg / 190 °C
(g/10 min) Density (g/cc)
mMDPE mMDPE 0.8 0.933 HDPE HDPE 1.2 0.961
Table 4-2: Polypropylene materials used in Clear PP Film Experiment #4 Material ID Description MFR 2.16 kg / 230 °C
(g/10 min) Flexural Modulus
(MPa) HPP Homopolymer PP 1.2 1420 r-PPC-A Clarified random copolymer 2.0 1000 r-PPC-B Random copolymer 5.5 650 r-PPC-C Clarified random copolymer 6.0 na TPO-B Thermoplastic olefin 0.6 80 Table 4-3: Experimental Film Structures in Clear PP Film Experiment #4 Layer PE Control PP Control Sample #1 Sample #2 Sample #3 Skin mMDPE r-PPC-B r-PPC-C r-PPC-C r-PPC-C Core HDPE HPP 70% HPP +
30% r-PPC-C r-PPC-A 70% r-PPC-A +
30% TPO-B
Skin mMDPE r-PPC-B r-PPC-C r-PPC-C r-PPC-C The 0.003 inch (76.2 m) thick co-extruded films were produced on the 3 layer blown co-extrusion film line similar to that described in experiment #2 and #3. A list of the process set up conditions is provided in Table 4-4. The layer ratios of the ABA co-extruded film structure were set at 10% - 80% - 10%. The bubble BUR was set at 1.7:1. Table 4-4: Blown Film Line Set Up Extruder Name A B C Nominal Extruder Diameter 60 mm 3.5 in 2.5 in Screw L/D Ratio 24:1 30:1 24:1 Number of Heating Zones 3 5 4 Layer Position in Co-extrusion Outer Core Inner Screw Type Single, Barrier Single, Barrier Single, Barrier Mixing Section Type Maddock Maddock Maddock Special Features Grooved Feed
Section
Die Size 11 inch (279.4 mm) Die Lip Gap 0.080 inch (2.032 mm) Cooling Dual Lip Air Ring with Chilled Air The films were tested and the data summarized in Figures 4-1 through 4-8. Film physical properties tested included: Elmendorf tear resistance, 1% secant modulus, tensile strength, protrusion puncture resistance, falling dart impact, % haze, 45° gloss and heat seal strength.
Figure 4-1: Figure 4-2:
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Figure 4-5: Figure 4-6
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Figure 4-7: Figure 4-8 45° Gloss
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PP ControlSample #3PE Control
sample width: 25.4 mmseal force: 2.757 barseal dwell: 0.5 speel rate: 5.08 mm/s
The clarifying additive performed as hoped, resulting in very low haze and high gloss for the experimental samples. Even for a fairly thick film, 0.003 inches thick (76.2 m), the haze values compare favorably to blown clarity films or films made on a cast or water quench processes. The experimental films modified with the r-PPC and TPO exhibited lower modulus and tensile strength while providing greater dart impact and protrusion puncture resistance with a modest improvement in Elmendorf tear resistance. The sample with properties most comparable to the PE control was sample #3 that had the TPO modified core layer. This is most interesting since the addition of a TPO would normally result in a very hazy film. In this case, the combination of the clarifying additive and encapsulation of the TPO in the core layer has provided for a good balance of optics, toughness and process bubble stability. In addition to good optics, the use of a PP terpolymer as the skin layer also provides for strong heat seals. The seal initiation temperatures for the materials were estimated to be ~121°C for the PP control film, ~126°C for the Clarity film, and ~143°C for the PE film. CONCLUSIONS: The experiments demonstrate that PP materials can be used to produce a variety of blown film structures. The properties of these films can be modified by combining materials in either blends or co-extruded film structures. In the simple two component systems described, there does appear to be a trade off between properties such as stiffness (modulus) and toughness (tear resistance, dart impact and puncture resistance). The addition of a TPO or PE into the film structure also improved the process bubble stability. As shown in the last example, through careful material selection and combining the techniques described, it is possible to create films with very interesting properties - in this case, an uncommonly clear, tough PP film. In conclusion, though often overlooked, it would be wise to reconsider PP materials as essential building blocks for blown film applications. ACKNOWLEDGEMENTS: Special thanks and acknowledgement to Bill Brown, Andy Gillan, Bill Snyder and Tracey Meder for their considerable efforts in preparing the materials, producing the films and completing the lab film testing.
DISCLAIMER: All technical assistance and advice is furnished by Basell without compensation. Basell assumes no obligation or liability with respect to such advice and assistance and disclaims any and all warranties with respect to such advice and assistance. APPENDIX: Table A-1: Film Test Characteristics
Test Method Elmendorf Tear Resistance ASTM D 1922 1% Secant Modulus ASTM D 882 Tensile Strength ASTM D 882 Protrusion Puncture Resistance ASTM D 5748 Falling Dart Impact ASTM D 1709 Haze ASTM D 1003 45° Gloss ASTM D 2457 Heat Resistance Internal Method Heat Seal Strength Internal Method
2007 PLACE Conference
September 16-20
St Louis, MO
Polypropylene Polypropylene –– Building Blocks for Building Blocks for Blown Film ApplicationsBlown Film Applications
Presented by:Spencer HirataTechnical Service & Applications DevelopmentBasell USA Inc.
Types of Polypropylene (PP)
• Homopolymer HPP
• Random copolymer r-PPC
• Impact copolymer i-PPC
• Thermoplastic olefin TPO
PP Material Characteristics
• Stiffness
• Heat resistance
• i-PPCs and TPOs provide toughness and improved bubble stability
Potential Use As Building Block
• Alone
• Blends
• Co-extrusions
Experiments – Blown Film Properties
• Effect of blending
• Blending vs co-extrusion
• LLDPE vs i-PPC in co-extruded structures
• Application example
Experiment #1: Experiment #1: Effect of BlendingEffect of Blending
Modification of HPP and i-PPC
• Blended with TPOs
• Monolayer film thickness 25.4 µm
800.6TPO-B
4000.65TPO-A
12000.45i-PPC
14201.2HPP
Flex Mod (MPa)MFR (g/10 min)Material
Equipment Set Up
• Extruder: 3.5 inch
• Die: 8 inch diameter0.080 inch gap
• Air ring: dual lip with chilled air
• BUR: 2 : 1
1% MD Secant Modulus
0
200
400
600
800
1000
1200
0 20 40 60 80 100% TPO
Mod
ulus
(MP
a)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
Heat Resistance
0
40
80
120
160
200
0 20 40 60 80 100% TPO
Hea
t Res
ista
nce
(°C
)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
Falling Dart Impact
0
200
400
600
800
0 20 40 60 80 100% TPO
Dar
t Im
pact
(g)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
Protrusion Puncture Resistance
0
2
4
6
8
10
0 20 40 60 80 100% TPO
Ene
rgy
to B
reak
(J)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
Haze
0
20
40
60
80
100
0 20 40 60 80 100% TPO
Haz
e (%
)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
MD Elmendorf Tear Resistance
0
60
120
180
240
300
0 20 40 60 80 100% TPO
Tear
Res
ista
nce
(g)
HPP + TPO-A Blend i-PPC + TPO-A BlendHPP + TPO-B Blend i-PPC + TPO-B Blend
Summary
————MD Tear Resistance
—/ —Haze
—Heat Resistance
——Protrusion Puncture
—Falling Dart Impact
1% MD Secant Modulus
TPO-BTPO-ATPO-BTPO-A
i-PPC BlendHPP Blend
Experiment #1 Conclusions
• Blending affects some film properties
• TPO-B exhibits greater influence on film properties as compared to TPO-B
• Observation - increasing TPO level improved bubble stability
Experiment #2:Experiment #2:Blending vs CoBlending vs Co--extrusionextrusion
Comparison of 2-Component Systems
• Monolayer blend vs ABA co-extrusion
– i-PPC combined with 2nd component (2nd)
– TPO or PE
• Film thickness 90 µm
ii--PPCPPC
ii--PPCPPC22ndnd60% i60% i--PPC + PPC +
40% 240% 2ndnd
} 30%} 40%} 30%
vs
2nd Component Materials: PP
200.6TPO-C
800.6TPO-B
4000.65TPO-A
Flex Mod (MPa)MFR (g/10 min)Material
2nd Component Materials: PE
0.8630.5POE
0.9181.0mLLDPE
0.9181.0LLDPE
Density (g/cc)MIE (g/10 min)Material
Equipment Set Up
• Extruders: 3.5 inch2.5 inch60 mm
• Die: 11 inch diameter0.060 inch gap
• Air ring: dual lip with chilled air
• BUR: 2 : 1
1% MD Secant Modulus
0
200
400
600
800
1000
LLDPE mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Mod
ulus
(MP
a)
i-PPC blend with 2ndi-PPC / 2nd / i-PPC co-ex
Protrusion Puncture Resistance
0
6
12
18
24
30
LLDPE mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Ene
rgy
to B
reak
(J)
i-PPC blend with 2ndi-PPC / 2nd / i-PPC co-ex
Haze
0
20
40
60
80
100
LLDPE mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Haz
e (%
)
i-PPC blend with 2ndi-PPC / 2nd / i-PPC co-ex
MD Elmendorf Tear Resistance
0
50
100
150
200
250
300
LLDPE mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Tear
Res
ista
nce
(g)
i-PPC blend with 2ndi-PPC / 2nd / i-PPC co-ex
Falling Dart Impact
0
200
400
600
800
1000
LLDPE mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Dar
t Im
pact
(g)
i-PPC blend with 2ndi-PPC / 2nd / i-PPC co-ex
Advantage Comparison
Falling Dart Impact
MD Tear Resistance
Haze
Protrusion Puncture
1% MD Secant Modulus
Co-extrusionBlend
Experiment #2 Conclusions
• How materials are combined affects final properties
• 2nd component characteristics can greatly influence film properties
• Observation - both TPO and PE modified structures exhibited good bubble stability
Experiment #3:Experiment #3:LLDPE vs iLLDPE vs i--PPCPPC
in Coin Co--extruded Structuresextruded Structures
Compare Co-extruded Film Properties
• Replicate ABA i-PPC co-extruded structures with LLDPE as primary component
• Film thickness 90µm
ii--PPCPPC
ii--PPCPPC2nd component
LLDPELLDPE
LLDPELLDPE2nd component
} 30%} 40%} 30%
vs
1% MD Secant Modulus
0
200
400
600
800
1000
mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Mod
ulus
(MP
a)
i-PPC / 2nd / i-PPCLLDPE / 2nd / LLDPE
i-PP
CLL
DPE
Protrusion Puncture Resistance
0
6
12
18
24
30
mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Ene
rgy
to B
reak
(J)
i-PPC / 2nd / i-PPCLLDPE / 2nd / LLDPE
i-PP
CLL
DPE
MD Elmendorf Tear Resistance
0
200
400
600
800
mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Tear
Res
ista
nce
(g)
i-PPC / 2nd / i-PPCLLDPE / 2nd / LLDPE
i-PP
CLL
DPE
Falling Dart Impact
0
200
400
600
800
1000
mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Dar
t Im
pact
(g)
i-PPC / 2nd / i-PPCLLDPE / 2nd / LLDPE
i-PP
CLL
DPE
Haze
0
20
40
60
80
100
mLLDPE POE TPO-A TPO-B TPO-C2nd Component
Haz
e (%
)
i-PPC / 2nd / i-PPCLLDPE / 2nd / LLDPE
i-PP
CLL
DPE
Advantage Comparison
1% MD Secant Modulus
Haze
Falling Dart Impact
MD Tear Resistance
Protrusion Puncture
LLDPEi-PPC
Experiment #3 Conclusions
• Each type of co-extruded structure exhibits advantages but for different properties
– i-PPC: 1% MD secant modulusPuncture resistance
– LLDPE: MD Tear resistanceDart impactHaze
Experiment #4:Experiment #4:Application ExampleApplication Example
Film for Stand Up Pouch
• Film properties to consider
– Stiffness modulus
– Toughness dart impact, puncture & tear resistance
– Optics haze & gloss
– Heat sealable
– Heat resistance
Targeted Structure
• Co-extruded PE film
• Film thickness 76.2 µm
mMDPEmMDPE
mMDPEmMDPEHDPEHDPE
} 10%} 80%} 10%
Strategy
• Use building block approach to design experimental film structures
• Combine techniques of blending and co-extrusion
• Use additives to further modify characteristics
Building Blocks Thought Process
haze & glossClarifying additive
toughnessr-PPC and or TPO blended into core
heat sealabler-PPC skin layer
stiffness & heat resistancePP material
rr--PPC Heat Seal LayerPPC Heat Seal LayerPP Core Layer
} 10%} 80%} 10%
• Structure similar to PE film
• Same film thickness 76.2 µm
Experimental Film Structure
rr--PPC Heat Seal LayerPPC Heat Seal Layer
PP Materials
800.6TPO-B
na6.0r-PPC-C*
6505.5r-PPC-B
10002.0r-PPC-A*
14201.2HPP
Flex Mod (MPa)MFR (g/10 min)Material
* contains clarifier
PE Materials
0.9611.2HDPE0.9330.8mMDPE
Density (g/cc)MIE (g/10 min)Material
Proposed Film Structures
r-PPC-Cr-PPC-Cr-PPC-Cr-PPC-BSkin
70% r-PPC-A +30% TPO-Br-PPC-A70% HPP +
30% r-PPC-CHPPCore
r-PPC-Cr-PPC-Cr-PPC-Cr-PPC-BSkin
Sample #3Sample #2Sample #1PP Control
Equipment Set Up
• Extruders: 3.5 inch2.5 inch60 mm
• Die: 11 inch diameter0.080 inch gap
• Air ring: dual lip with chilled air
• BUR: 1.7 : 1
1% MD Secant Modulus
0
200
400
600
800
1000
1200
PE Control PP Control Sample #1 Sample #2 Sample #3
Mod
ulus
(MP
a)
MD Elmendorf Tear Resistance
0
25
50
75
100
125
150
PE Control PP Control Sample #1 Sample #2 Sample #3
Tear
Res
ista
nce
(g)
Falling Dart Impact
0
40
80
120
160
200
PE Control PP Control Sample #1 Sample #2 Sample #3
Dar
t Im
pact
(g)
Protrusion Puncture Resistance
0
4
8
12
16
PE Control PP Control Sample #1 Sample #2 Sample #3
Ene
rgy
to B
reak
(J)
Haze
0
5
10
15
20
25
30
PE Control PP Control Sample #1 Sample #2 Sample #3
Haz
e (%
)
45° Gloss
0
20
40
60
80
100
PE Control PP Control Sample #1 Sample #2 Sample #3
Glo
ss
Heat Seal Strength
0
10
20
30
40
50
80 90 100 110 120 130 140 150 160Sealing Temperature (°C)
Sea
l For
ce (N
)PP ControlSample #3PE Control
sample width: 25.4 mmseal force: 2.757 barseal dwell: 0.5 speel rate: 5.08 mm/s
Advantage Comparison to Target
PP
Falling Dart Impact
45° Gloss
Haze
Protrusion Puncture
≈1% MD Secant Modulus
Heat Seal
MD Tear Resistance
#3#2#1PE
Experiment #4 Conclusions
• Experimental PP films
– Excellent optical properties
– Balance of stiffness and toughness
– Heat sealable
• TPO modified structure adds
– Improved tear resistance
– Enhanced bubble stability
In Conclusion
• Polypropylenes can provide a balance of stiffness, toughness and heat resistance to blown film structures
• The range of film properties can be expanded by blending and or co-extruding with other materials
• A polypropylene building block strategy is an effective way to produce unique application solutions
Acknowledgements
A special thank you to Bill Brown, Andy Gillan, Bill Snyder, and Tracey Meder for their contributions in producing the film samples and completing the physical property testing.
Disclaimer
All information contained herein, including, but not limited to, all information developed, prepared or otherwise presented by a third party, is provided by Basell without any warranty whatsoever, and Basell specifically disclaims all express and implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose, to the fullest extent allowable by law. In no event shall Basell be liable for any damages, including, but not limited to, direct, indirect, special, consequential, incidental, punitive, or exemplary damages, arising from or related to the information contained herein.
Thank YouPRESENTED BY
Spencer HirataTechnical Service & Applications DevelopmentBasell USA Inc.
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