Innovative Techniques to use EVOH Smartly and Effectively in Gas Barrier Packaging Applications

Transcription

1 Innovative Techniques to use EVOH Smartly and Effectively in Gas Barrier Packaging Applications Guojun Zhang Ph.D. 10/10/2016 FlexPackCon, Tennessee

2 A World Leader, Focused on Innovative Solutions to Meet Our Customers Needs Founded 1928 in Akron, Ohio Expanding footprint with 57 manufacturing sites in 27 countries 4,900 employees More than 800,000 metric tons of annual manufacturing capacity ~$2.5 billion net sales in 2015 % of Revenue 2 Global Headquarters in Akron, Ohio

3 Outline Polymer Morphology and Their Gas Barrier Properties Polymeric Barrier Resins to be used in Multilayer/Monolayer structures EVOH Modifier 3

4 Free Volume and Gas Permeability P 1 P 2 P = S D Free volume Between molecules, Between atoms, Excessive-free volume.. l PE molecules: graph is from internet Thermal Kinetic Where, P is permeability coefficient Gas Size /A Gas Size /A He 2.6 H 2 O 2.8 H CO O N CH C 3 H T S D, usually, smaller the gas molecule, faster the diffusion in the same polymer. t1 [Ref] t2 t3 tz P 1 Ref P 2 Gas molecule fill the free volume holes and spend most of the time there. They only occasionally jump into a neighboring hole. 4

5 Oxygen Permeability of Some Polymers Polymer O2 Barrer (23 o C, 0% RH) Poly(vinyl alcohol) (PVA) ~7Χ10-6 [1,2] Ethylene (EVOH L171 27% ethylene) ~2.6Χ10-5 Ethylene (EVOH E171 44% ethylene) ~ Polyacrylonitrile (PAN) ~ MXD6 Nylon ~ [1] Vectra LCP ~ Barex 210 ~0.005 BOPET ~0.02 [1] Nylon 6 ~0.03 [2] PET ~0.057 Poly(methyl methacrylate) (PMMA) ~0.086 Biaxially Oriented Polypropylen (BOPP) ~0.9 Polycaprolactone (PCL) ~1.0 Polypropylene (PP) ~1.5 1 Barrer = (cm 3 O 2 ) cm/ cm 2.s.mmHg 1 = ~103 cc.mil/100inch 2.day.atm Reference: [1] Critical Reviews in Food Science and Nutrition, 52: (2012). [2] Robeson presentation. 5

6 Motivation/Demand of Improving Barrier of Polymers Many polymers do not have sufficient barrier for food items as packaging materials. One year shelf life. Package dimension: 500 cm3, wall thickness 11 mil, ΔP O2 =20 cmhg Food/beverage Estimated max. tolerable O 2 gain, ppm Required O2 permeability, Barrer Polymer O2 Permeability (Barrer) 25 o C Canned milk, meats, canned vegetables EVOH (27%) Beer, ale, wine PVDC Canned fruits Nitrile resin Fruit juice, drinks PET Dressing, oils PE 2.86 Refs: [1] Table is from the dissertation of Kevin Tung, [2] R. Coles, M.J. Kirwan, Food and Beverage Packaging Technology, 2nd ed., John Wiley & Sons, Ltd, Refs

7 Key Factors of Polymer in Determining Gas permeability Gas Permeability How well can gas dissolve and migrate in polymer S D How much free volume is How well the free volume can connect Crystallinity Density of amorphous region Polymer chain interactions and mobility Orientation and Morphology 7

8 Orientation: Densification and Reducing Chain Mobility Example: BOPET Due to long timescale of required for fully relaxing, glassy polymer like PET has excessive-free volume. Ref Orientation at low temperature, e.g. below Tg of PET, decreases free volume. Orientation at higher temperature induces crystallinity. Both ways result in higher density of polyesters. Sample ƿ g/cm 3 PO 2 Barrer PET film pressed [R1] [R1] PET cold drawn film ƛ=4 PET cold-blown wall ƛ= [R1] [R1] [R1] [R1] Ref 1: Journal of Applied Polymer Science, Vol. 94, (2004) Example: BOPP Sample Xc % PO 2 Barrer PP control 48 [R2] 0.91 [R2] PP 44 [R2] 0.55 [R2] Ref 2: Polymer 49 (2008) Stretching of PP induces crystal orientation and reduces the mobility of molecule chains, despite of decreasing of density and crystallinity. 7

9 Example: PE and PP Polymer Melt Nucleation to Control Morphology Without nucleate: homogeneous nucleation, large spherullites Crystallization in progress Fully Crystallized With nucleate: heterogeneous nucleation, smaller and uniform crystals Polymer Melt with nucleates Crystallization in progress Fully Crystallized Adding nucleators improves PE and PP s barrier properties. 0 OTR cc.mil/m 2.day Effect of Nucleator on HDPE OTR Control 1000 ppm 9

10 Solution coating, chemical vapor deposition (CVD), physical vapor deposition (PVD) Coatings and Scavenger Coating Silicon-oxide Aluminum Silicon-nitride Palladium Disadvantage Brittle, adhesion is poor Clarity, pin holes, environmental concerns Coating defects No clarity Oxygen Scavenger is widely used as food/packaging additives to improve shelf life. 10

11 Inorganic Fillers and Polymer Blends to Improve Gas Barrier Some inorganic materials with decent aspect ratio can be incorporated in polymer for improving barrier properties: Clay, P-glass, layered-silicates, nanotube. Model Filler type Sample OTR/ barrer (23 C, 0% RH) Nielsen Cussler Random array Ribbon Ribbon Ribbon Ref PET 0.36 MXD PET-MXD [Ref] Polymer 46 (2005) Ref [Ref] Polymer nanotechnology: Nanocomposites, D.R. Paul, L.M. Robeson Depending on aspect ratio, dispersion and shape, permeability of the composites can be predicted by different models. Blending higher barrier polymer can improve the barrier property. 11

12 Tailoring Polymer Morphology to Improve Barrier Properties Assumption: Each component s permeability does not change in the system. Miscible Blend Blend with Elongated Morphology Layered Structure Blend Model Ln P=φ 1 Ln P 1 + φ 2 Ln P 2 Better the higher barrier phase elongated, higher the gas barrier. Series Model P=1/(φ 1 /P 1 + φ 2 /P 2 ) The barrier property of a blend can be maximized if the higher barrier component forms a continuous phase, which technically is a layer. 12

13 Example to Show Difference between Layered Morphology and Blend Morphology in Gas Permeability Assumption: Each polymer s permeability does not change in the system. Polymer OTR/Barrer A 1 B 0.01 Note: here we only use two imaginary polymers as an example Based on the calculation, for the same pair of polymer A and Polymer B. Layered morphology usually yields lower permeability (better barrier) than blend morphology. 13

14 Crystalline Morphology of Polymers and Their Barrier in Multilayered Films Example: Hundreds of layers in a thin film can be achieved by multiplication co-extrusion technique [Ref] Carr, J.M., Langhe, D.S., Ponting, M.T., Hiltner, A., Baer. J. Mater. Res., Vol. 27, No. 10, May 28,

15 PEO Layers Under Confinement PEO Layer 1-10 µm PEO Layer nm EAA (110) PEO (032) EAA-PEO Multilayer Films PEO (120) In-plane oriented PEO Lamellae was achieved Ref Ref: H. Wang,etc. Science, 2009(323), Ref 15

16 P(O 2 ) of PEO Layer (barrer) Calculated P(O 2 ) of PEO Layer* Improved OTR Barrier of PEO Layers Due to Confinement PEO Control Oriented PET Nylon6,6 MXD6 EAA/PEO PS/PEO [Ref] PEO Layer Thickness (nm) 1 1 φ *Calculated from series model P E O = φpeo PFilm PEA [Ref] Carr, J.M., Langhe, D.S., Ponting, M.T., Hiltner, A., Baer. J. Mater. Res., Vol. 27, No. 10, May 28, PEO A 1 Cussler Model 2 2 αφc P= Pm [1+ cos θ ] 4(1- φ ) c 2 1 Aspect ratio [Ref] α = L W Parameters: P, permeability of EAA/PEO layered film P m, permeability of EAA as matrix φ c, volume fraction of PEO crystals cos 2 θ =0 for perpendicular orientation 16

17 What Do People Really Need for Barrier in Packaging? 1. How many layers does the industry need? Do people really want to pay for expensive fancy packaging? 2. Do people really need to improve gas barrier for all applications? What type of improvements do people really need? EVOH? Ref Water sensitivity and poor WVTR barrier are the shortages of EVOH resins. In order to effectively use EVOH, a moisture barrier layer is often needed. The water sensitivity of EVOH requires improvement in many applications. [Ref]: Technical brochure from Kuraray. 17

18 Outline Polymer Morphology and Their Gas Barrier Properties Polymeric Barrier Resins to be used in Multilayer/Monolayer structures EVOH Modifier 18

19 Confidential Information Materials and Processing Materials: Resin T m / o C T c / o C LLDPE EVOH E Processing: Compounding: Extrusion: Different compositions 19

20 Mechanism of MOCON units Permeation How to Measure Gas Permeability Test Gas O 2 Carrier Gas N 2 +H 2 Unsteady state P = F L F: flux l: Thickness Steady state Film sample Example of MOCON Oxtran Data Mocon Oxtran and Permeatran units give us the flux data directly. After normalizing by thickness, we get the permeability results. 20

21 Effect of Blend Morphology on the Oxygen Permeability Oxygen permeability of extruded blend films. Extruded blend film (EVOH-LLDPE composition) P O 2 / Barrer 23 o C, 0% RH P O2/ Barrer based on blends model Improvement ratio LLDPE control 3.7±0.1 / / EVOH control ± / / EVOH-LLDPE V 1 EVOH-LLDPE V 2 (EXP-BAR2400) EVOH-LLDPE V ± ± ± LnP = ϕ LnP + ϕ LnP blend Barrer = (cm 3 O 2 ) cm/cm 2.s mmhg -1 LLDPE-EVOH V2 showed the best barrier property due to the extended morphology. 21

22 Blend Shows Excellent Gas Barrier Assumption: Each polymer s permeability does not change in the system. Polymer OTR/Barrer LLDPE 3.7 EVOH Based on the calculation, for the same pair of polymer A and Polymer B. Layered morphology usually yields lower permeability (better barrier) than blend morphology. 22

23 Comparing with Layered Structure EXP-BAR 2400: LLDPE-EVOH V2 blend LLDPE/EVOH Layered Film 0 µm 10 µm 0 µm 10 µm PO2 (barrer): ± ± LLDPE-EVOH V2 compound (BAR 2400) film showed similar oxygen permeability as layered film due to proper composition and processing. 23

24 Other Properties of EXP-BAR 2400 Oxygen Permeability / Barrer Oxygen Permeability as a factor of RH OTR under different RHs RH % UV-vis Spectrum of BAR LLDPE-EVOH V2 compound (BAR 2400) showed decent water sensitivity compared to EVOH resins. It also yields pretty good transparency in all visible light wavelength range. Light Transmissionr ate % Light Wavelength nm 24

25 Typical stress-strain curves for Bar 2400 Other Properties of EXP-BAR 2400 Test method: ASTM D882 Sample EVOH control BAR 2400 LLDPE control Young s modulus (Gpa) ED/TD Yield Strength (Mpa) ED/TD 1.80±0.09 / 1.80± ±3 / 28±4 0.84±0.03/ 0.74± ±2 / 11±2 0.17±0.05 / 0.16±0.03 4±0.3 / 4±0.3 Decent mechanical properties endure that BAR 2400 can be used in many packaging applications. 25

26 EXP-BAR 2400 in 3-layer Structures Our strategy is to incorporate our blend into a three layer structure and test the barrier properties. WVTR g/100 inch 2.day 1.58 ± ± ± 0.01 O2 (0%RH) Barrer TBD O2 (50%RH) Barrer TBD O2 (90%RH) Barrer TBD Haze % 4.9 ± ± ± 1.2 Tensile max load Mpa * 4.8 ± 1.7 / 4.4 ± 1.2 Note: * means ASTM D882 PEEL ONLY WVTR EVOH : 4.5 g.mil/100inch 2.day O 2 EVOH : Barrer (0%RH) Barrer (90% RH) Decent 3-layer films using BAR 2400 as the core layer was successfully fabricated. This suggests that BAR 2400 can be used in multilayer films as well. 26

27 A NEW BARRIER RESIN: EXP-BAR 2500 BAR 2500: Effect of RH on its OTR All samples are cast films BAR 2500 shows decent moisture resistance. As RH increases, Bar 2500 keeps its oxygen barrier effectively. 27

28 EXP-BAR 2500: Excellent WVTR Barrier All samples are cast films BAR 2500 shows excellent WVTR barrier when compared to many traditional barrier resins, e.g. Barex and EVOH. 28

29 Other Properties of EXP-BAR 2500 UV-vis Spectrum of BAR 2500 Light Transmission Rate % Wave length /nm HAZE % 45 o Thickness mil BAR 2500 shows Excellent light transmission rate at all visible light wavelength range. Low gloss value. Decent haze value. Excellent gas and moisture barrier ensures that EXP-BAR 2500 resin can be used to replace many traditional barrier resins. 29

30 Application of EXP-BAR 2500 in multilayer Structures Replaceable By BAR 2500? While EXP-BAR2500 resin offers excellent oxygen barrier, it also yields very high barrier to water vapor. Not all barrier resins exhibit barrier to both gases and moisture. This characteristics ensure BAR2500 can be used in many applications. 30

31 Conclusions for this Part PE and EVOH compound resins with layered-like morphology were successfully fabricated with proper compositions and processing. The preferred morphology within the compounds offers good gas barrier similar to multilayered films. EXP-BAR2400 and EXP-BAR2500 resins yield both excellent oxygen and water moisture barrier compared to many traditional barrier resins. 31

32 Outline Polymer Morphology and Their Gas Barrier Properties Polymer Compound Resins to be used in Multilayer/Monolayer structures EVOH Modifier 32

33 Reducing Water Sensitivity of EVOH by Adding Modifiers Solutions to improve the performance: Add modifier into the polymers. Mechanism of this modifier: EVOH has great gas barrier property due to its high intermolecular/intramolecular cohesive energy. With increased RH, the interactions between excessive water molecules and the hydroxyl groups in the polymer matrix will weaken the existing hydrogen bonds between polymer molecules. As RH increases, EVOH chains segmental motion is enhanced, and its Tg decreases. [Ref] [Ref]. Iwanami, T.; Hirai, Y. Tappi J 1983, 66,

34 Masterbatch and Samples Produced Carrier Resin Loading of Modifier M1323 V1 EVOH 40% Sample ID M1323(1)-F0 M1323(1)-F1 M1323(1)-F2 M1323(1)-F3 % M1323 V % E % active modifier Sample ID M1323(2)-F0 M1323(2)-F1 M1323(2)-F2 M1323(2)-F3 % M1323 V % L % active modifier All films are monolayer with nominal thickness of 1 mil and scarified skin layers. 34

35 WVTR of Modified EVOH M1323 (1) series M1323 (2) series Based on the results, modifier improved EVOH resins WVTR barrier overall speaking. 35

36 Permeability of Modified EVOH M1323 (1) series Based on the results, when the active concentration of modifier is 5%, the oxygen barrier of EVOH (E44) keeps nearly unchanged. 36

37 M1323 (1) series Reduced Water Sensitivity of Modified EVOH As RH increases, films with modifier showed less change compared to EVOH control 37

38 Modified EVOH : Reduced Water Sensitivity Sample 0 RH OTR cc.mil/m 2.day 50RH OTR cc.mil/m 2.day 60RH OTR cc.mil/m 2.day 70RH OTR cc.mil/m 2.day 80RH OTR cc.mil/m 2.day 90RH OTR cc.mil/m 2.day EVOH control 2.30 (1) 1.65 (0.72) 2.56 (1.10) 2.6 (1.13) 3.9 (1.70) 6.5 (2.83) EVOH+5% modifier 2.52 (1) 1.69 (0.67) / 2.58 (1.02) 2.98 (1.18) 5.4 (2.14) EVOH+10% modifier 2.57 (1) 1.87 (0.73) / 2.65 (1.03) 3.74 (1.46) 4.84 (1.88) Note: We set all the data measured at 0 RH as 1 (it does not mean the OTR is really 1), then calculate the ratios for data obtained under other RHs. By doing so, we can detect the degrees of change in OTR under different RHs excluding the baseline difference. Comparing the absolute values here is not meaningful. The trend is our focus. We used the change of OTR under different RHs to describe the water sensitivity of EVOH.

39 Conclusions for this Part EVOH resins with high intermolecular/intramolecular cohesive energy usually show great gas barrier property. But very sensitive to moisture. Adding EVOH modifier masterbatch can improve EVOH s water vapor barrier directly. Adding EVOH modifier masterbatch reduces EVOH s water sensitivity, which enables EVOH to maintain better oxygen barrier at higher relative humidity environments. 39

40 Acknowledgements No matter how you define success, A. Schulman has the materials expertise, processing know-how, market knowledge and application experience to help you achieve it. We not only offer a rich, diverse portfolio of standard products, we work closely with our customers to understand their unique challenges and customize a unique solution that optimizes their processes. Our definition of success is helping you achieve yours. R/D Team at A. Schulman, Inc. MBS solutions Kari MacInnis: Technical Manager Kari.MacInnis@aschulman.com Guojun Zhang: R/D Engineer Guojun.zhang@aschulman.com Kent O Neill: R/D Engineer kent.o'neill@.aschulman.com suc cess [sək-ˈses] Thank You 40

41 Disclaimer The user is not entitled to copy or distribute this document. You may not copy this document to a Web site. Schulman Plastics does not guarantee the typical (or other) values. Analysis may be performed on representative samples and not the actual product shipped. The information in this document relates only to the named product or materials when not in combination with any other product or materials. We based the information on data believed to be reliable on the date compiled, but we do not represent, warrant, or otherwise guarantee, expressly or impliedly, the merchantability, fitness for a particular purpose, suitability, accuracy, reliability, or completeness of this information or the products, materials, or processes described. The user is solely responsible for all determinations regarding any use of material or product and any process in its territories of interest. We expressly disclaim liability for any loss, damage, or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information in this document. There is no endorsement of any product or process, and we expressly disclaim any contrary implication. The terms, we, our, "Schulman Plastics" or Schulman are used for convenience, and may include any one or more of A. Schulman Companies, A. Schulman Plastics Corporation, or any affiliates they directly or indirectly steward. Schulman Plastics, the Schulman Plastics Emblem and Polybatch, Polywhite, Polyblak, Papermatch, Polycolor, are trademarks of A. Schulman 41