new developments in plexar® tie-layer adhesives...7680 – m. botros 7 key attributes of new...
TRANSCRIPT
New Developments in Plexar®Tie-Layer Adhesives
Dr. Maged BotrosLyondell Chemicals
Session: Extrusion MaterialsPaper Number: 7680
7680 – M. Botros 2
New Developments in High-Performance Tie-Layers
Topics:
I. High-Clarity Barrier Films• New Developments
• EVOH Applications• Nylon Skin Layer Application
II. High-performance tie-layer development for PS / HIPS Applications
• Advantages of new development
• Compare Theory to Experimental Results• Developed New Analytical Techniques• Correlation of Macro Scale Performance to Molecular Level
7680 – M. Botros 3
Global Trend: Increasing Demand for High-Clarity Barrier Films
• Consumer preference for retail display packages with excellent optics
• Films with poor clarity detract from a quality image
• Intense competition in film-converting industry for distinguishing benefits
• Clarity is a “must-have”feature
• Low-clarity films are at a disadvantage
7680 – M. Botros 4
Transparency Loss in Barrier Coextrusions
Measurement: narrow angle scattering (NAS)
PhenomenaCoextruded barrier films with low optical transparency due to apparent instability at tie-barrier interface- “Ground glass,” “graininess,” “orange peel” appearance
CauseAn uneven interface between tie layer and barrier layer, possibly caused by covalent bonding, that amplifies interfacial stresses that lead to nanometer scale distortions
7680 – M. Botros 5
Adhesion Versus Clarity in Standard Multi-layer Films With EVOH Barrier
0
1
2
3
4
5
6
2MI LLDPE Adh-A Adh-B
Adhesive
Adhe
sion
(N/1
5mm
)
0
5
10
15
20
25
30
35
40
45
50
NAS Adhesion
NAS Clarity
7680 – M. Botros 6
Performance of New Tie-Layer Developments in Multilayer Films With EVOH Barrier
7.9
2118.4
28
42
27
05
1015
20
2530
3540
45
Standard-A Tie-Clarity1 Tie-Clarity-2
5X Adh (N/15 mm) NAS
7680 – M. Botros 7
Key Attributes of New Developments
• LLDPE-based tie-layer: 1.1 MI, 0.92 density
• Specifically designed for EVOH blown film coextrusions where excellent optics and transparency are required
Good viscosity and shear stress matched of most blown film EVOH grades
Optimized anhydride content for adhesion and transparency
Unique structure and graft architecture
Ability to absorb and dissipate interfacial stresses
7680 – M. Botros 8
New Developments in High-Performance Tie-Layers
Topics:
I. High-Clarity Barrier Films• New Developments
• EVOH Applications• Nylon Skin Layer Application
• Theory versus practice!
– The effect of interfacial shear stress and elasticity ratio at the interface of nylon/tie multilayer film structures were found to be insufficient parameters to explain the optical properties measured experimentally
7680 – M. Botros 9
Attempt to Correlate Interfacial Elasticity Ratio with Clarity
7680 – M. Botros 10
New Developments in High-Performance Tie-Layers
Topics:I. High-Clarity Barrier Films
• New Developments• EVOH Applications• Nylon Skin Layer Application
• Theory versus practice!– Theory alone was inadequate in explaining
experimental data– It was predicted that such inadequacy was due to the
neglect of chemical interactions at the Nylon/Tie interface
– A new test was devised to rheologically probe the interaction at the nylon/tie interface
7680 – M. Botros 11
Rheological Probing of Nylon/Tie Interface:Increase in Elastic Modulus as a Function of Time
7680 – M. Botros 12
Effect of Outer Nylon Layer Thickness on Film Clarity
59.0
24.6
56.2
0.0
-10.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
High Clarity Tie-A Low Clarity Tie-B4
% N
AS
20% PA10% PA
7680 – M. Botros 13
New Developments in High-Performance Tie-Layers
Topics:
I. High-Clarity Barrier Films• New Developments
• EVOH Applications• Nylon Skin Layer Application
• Atomic Force Microscopy Study– A closer look at the interface– Additional parameters affecting clarity
7680 – M. Botros 14
Atomic Force Microscopy Images Showing Crystalline Morphology of Nylon
7680 – M. Botros 15
AFM Images Using High Clarity Tie Showing Continuous and Undisturbed Tie/Nylon Interface
7680 – M. Botros 16
AFM Images of Low Clarity Tie in Multilayer Nylon Film. Delamination at the Interface and Interlayer Mixing is Observed
7680 – M. Botros 17
Summary of High-Clarity Development
• The effect of adhesion on multi-layer film clarity was investigated
–Analysis of current tie-layer grades show that higher adhesion typically leads to lower clarity
–By carefully controlling the reaction kinetics and rheological characteristics of tie-layers, we were able to develop new adhesives that maintained high clarity and high adhesion at the same time
7680 – M. Botros 18
II- High-Performance Tie-Layer Development for PS/HIPS Applications
Product characteristics
LLDPE-based tie-layer adhesive
Melt index = 3.30 g/10 min (D 1238)
Density = 0.9335 g/cc (D 1505)
Vicat softening point = 88.3°C (D 1525)
7680 – M. Botros 19
Performance of New Tie-Layer Developments in PS/HIPS Applications
(A) Macro Scale Investigation
Adhesion Performance- Heat Seal- Sheet Co-Extrusion- Effect of Temperature- Thermoforming- Optical Microscopy (Not Shown – Too big to be presented!!)
7680 – M. Botros 20
Effect of PS/HIPS Blends on Heat Seal Adhesion at 260°C
1.2
0.8 0.8
4.6
4 4
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Adh
esio
n (N
/2.5
4 cm
)
Ref Adh-PX
Tie-Layer
HIPS-1/PS-1
HIPS-2/PS-2
HIPS-3/PS-3
7680 – M. Botros 21
Adhesion Performance of New Tie-Layer in Co-Extruded Sheet Application
5.1
9
32
0
5
10
15
20
25
30
35
Adh
esio
n (N
/15
mm
)
Ref-1 Ref-2 Adh-PX
Tie-Layer
Coex Sheet
7680 – M. Botros 22
Effect of Temperature (50 °C) on Adhesion Performance in Co-Extruded Sheet Application
6 5.7
12.3 12.5
0
2
4
6
8
10
12
14
Adhe
sion
(N/1
5 m
m)
Ref-2 Adh-PX
Tie-Layer
3 Min.
5 Min.
7680 – M. Botros 23
Adhesion Performance of New Tie-Layer After Thermoforming
3.43.8
6
0
1
2
3
4
5
6
7
8
Adhe
sion
(N/1
5 m
m)
Side-Vertical Side-Horizontal Cup Rim
Tie-Layer
Adh-PX
7680 – M. Botros 24
Performance of New Tie-Layer in PS/HIPS Applications
(B) Micro Scale Investigation
Atomic Force Microscopy- A closer look at the interface- Effect of Tie-Layer- Effect of Thermoforming- Molecular Orientation due to thermoforming
7680 – M. Botros 25
AFM Images of Low Performance Tie in PS Multilayer Sheet. Large Gap at Tie-PS Interface
7680 – M. Botros 26
AFM images of New Tie-Layer Exhibiting Excellent Adhesion with No Interfacial Delamination at Tie/PS Interface
7680 – M. Botros 27
AFM Images of Reference Tie in Thermoformed Cup: Vertical Gap at Tie/PS Interface
7680 – M. Botros 28
AFM Images of New Tie-Layer in Thermoformed PS Cup Exhibiting Excellent Adhesion in Presence of High Orientation
7680 – M. Botros 29
Technical Summary for PS/HIPS Applications• 300% – 400% improved adhesion compared to references • Optimized MI for sheet extrusion process• LLDPE-based offer advantages over EVA-based
adhesives– Low odor– Easy thermoform-ability– No Stringing– High temperature applications
• New tie-layer could have a cost/performance advantage upon down gauging
• Enhanced performance at high temperature• Retained high performance after thermoforming
7680 – M. Botros 30
Conclusions• Developed new tie-layer adhesives for high-performance
applications:– High-clarity, multi-layer film application
• Maintain high clarity and high adhesion at the same time
– High-performance tie-layer development for PS/HIPS applications
• Maintain high adhesion and container integrity after thermoforming
• Applied new analytical techniques in developing high-performance tie-layer adhesives that are targeted for specific applications
• Related performance on macro scale to micro / molecular level
7680 – M. Botros 31
Acknowledgments
Coauthors: Dr. Harry Mavridis and Dr. Francis Mirabella
The authors would like to thank Mr. Randy McIntosh, Mr. Michael Grubb, Mr. John Leurck, Mr. Daniel Riopell and Mr. William Shumake for their significant contribution and assistance.