DuPont Packaging & Industrial Polymers

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1 DuPont Packaging & Industrial Polymers Tools for Optimizing Flexible Packaging W H I T E P A P E R Barry A. Morris, Senior Technology Associate DuPont Packaging Introduction Optimizing the design and manufacture of a flexible package takes time and money. In considering alternative materials, designs and production processes, the package engineer must understand the suitability of these options in order to design and produce a package that performs its mission, is cost-effective both in cash terms and in its impact on the environment. Developing or optimizing a package structure usually requires several iterations of making and testing prototypes and alternatives. Computer modeling and simulation can help reduce development time and cost by eliminating iterations and allowing the engineer to optimize function and cost on the computer before any film is made. Modeling can also help determine if problems such as poor extrusion, flow instabilities or curl may occur during film fabrication. If so, potential solutions in material selection, structure and process can be scoped out prior to running on the production line. DuPont has developed a number of computer modeling and simulation tools to aid in optimizing package design and the manufacturing process. These are listed in Table 1. This paper focuses on three DuPont tools. They are the Sealant Selector, Sealant Value Estimator (SaVE), and a tool for downgauging and life cycle analysis. Table 1. DuPont Models for Package Optimization Package Design Sealant Selector Cost Calculator Downgauging/Life Cycle Heat Seal/Hot Tack Permeability Calculator Processing/Converting Flow Instability in Coextrusion Curl (coextruded blown film) Blown Film Scale-up (process time) Extrusion Coating Stress Heat Transfer Friction Modeling

2 Tools for Optimizing Flexible Packaging - 2- Figure 1. Ranking Attributes Choosing the Right Sealant The DuPont Sealant Selector helps the user select the sealant best suited for a given application. The user first inputs key attributes of the package and processes employed to make it. He or she then rates sealants based on their performance in the selected attributes (Figure 1). The model then compares different sealants according to the user s attribute rankings. Table 2 shows an example of a ranking of attributes for a bacon shingle pack. The scale is from 1 to 10, with 10 being of highest importance. Table 2. Inputs to Sealant Selector Tool for Bacon Package Attribute Importance Rating (1-10 scale) Blown film processibility 5 Adhesion to PE in coextrusion 5 Low seal initiation temperature 8 Broad hot tack temp range 8 Seal around greasy/particulate contamination 10 Secondary sealing 7 Good formability 6 High stiffness 5 Optics, clarity & gloss 10 Grease and oil resistance 10 Abrasion/scratch resistance 3 Flex crack resistance 3 Perforation resistance, static puncture 8 High-speed (dynamic) puncture resistance 4 Easy-to-open seal technology 5 The results comparing various sealants according the selected attributes are shown in Figure 2. The functional score for each sealant type has been normalized to a scale of 0 to 10. The width of each bar is the sum of the importance

3 Tools for Optimizing Flexible Packaging - 3- factors multiplied by the matrix score for each attribute. The individual contribution from each attribute is highlighted by color and can be used to quickly see why one sealant is scoring better than another. In this example, ionomers and EVA have the highest scores. Ionomer scores highest because of its grease resistance, ability to seal around contamination and perforation resistance all of which are very important in bacon packs in combination with other desired attributes. It s no wonder then that ionomer is widely used as a sealant for bacon packages. Ionomer often rises to the top whenever the sealant must perform functions in addition to sealing. Figure 2. Sealant Selector Tool Results for Bacon Shingle Pack How Much Does Your Package Really Cost? The new DuPont Sealant Value Estimator, called SaVE, calculates and compares total packaging costs of alternative materials. Its focus goes beyond material costs by including other major cost components that vary according to the sealant used, namely filling-line costs, rewraps, off-machine losses and in-store package failures. The model for SaVE is based on more than 20 years of DuPont experience in performing such calculations for customers. SaVE is now available on-line at so that converters and packagers can perform their own analyses. The model is fully transparent; its underlying formulas are freely available to users. Here s how SaVE works. The user inputs actual cost data for his or her packaging plant and estimated and actual data for films using alternative sealants. As an example, inputs for a hypothetical cereal box liner are summarized in the top part of Figure 3. The program then analyzes the inputs and produces a cost analysis. The example shown in Figure 3 simulates a comparison of packaging costs for a film with a sealant such as PE with one using DuPont Surlyn ionomer. In this case, switching to Surlyn significantly reduces off-machine and in-store package failures, providing a saving of $4.71 per thousand packages, or about 5.9% (Figure 4).

4 Tools for Optimizing Flexible Packaging - 4- Figure 3. SaVE, Sealant Value Estimator, Input Summary and Analysis* *Hypothetical Data For Demonstration Purposes Only

5 Tools for Optimizing Flexible Packaging - 5- Figure 4. Switching to Surlyn Produces Estimated Saving of 5% in Total Packaging Cost of Cereal Liner* *Hypothetical Data For Demonstration Purposes Only Another valuable feature of SaVE is its capability for performing sensitivity or breakeven analysis for key cost components. The breakeven point for each cost parameter is compared as all other variables are held constant. Figures 5 and 6 show typical analyses for two variables, roll stock price and line speed. Data for off-machine and instore losses can be analyzed in the same way.

6 Tools for Optimizing Flexible Packaging - 6- Figure 5. Sensitivity (Break-Even) Analysis, Roll Stock* Figure 6. Sensitivity (Break-Even) Analysis, Line Speed* *Hypothetical Data For Demonstration Purposes Only

7 Tools for Optimizing Flexible Packaging - 7- Downgauging and Life Cycle Analysis A third tool enables DuPont to assist customers in downgauging films while maintaining desired levels of performance, calculating the cost of alternative materials and performing life cycle analysis (LCA) to calculate and compare non-renewable energy consumption, and greenhouse gas emissions of film materials of different thickness. The analysis model computes the bending stiffness of multilayer structures and makes it possible to keep bending stiffness constant when designing and evaluating downgauged structures. This is required in order to maintain performance in packaging equipment, minimize package failures and avoid negative consumer perception of flimsy packages. The stiffness model for the downgauging analysis is well validated. DuPont has been using it for more than 15 years in downgauging projects for customers. Nevertheless, the model does not negate the need to test downgauged structures. The conditions on a filling line can have a significant impact on heat-sealing performance. The model calculates and compares costs, but only of the materials in a given multilayer film. It does not take converting costs into account. The materials-only approach also applies to the model s life cycle analysis. Its calculations of non-renewable energy consumption and greenhouse gas emissions do not take into account the effects of downstream processing, consumer use or end-of-life scenarios. The LCA model has been peer-reviewed by a third party. The reviewer does not endorse assertions based on comparative results, however. The LCA results are a suitable tool for quickly exploring technology options. They cannot be used as a basis for advertising claims, and more comprehensive studies are needed for making business decisions. An analysis begins with entering data for each layer in the structure. Inputs include secant modulus, thickness, material price, non-renewable energy consumption (material only) and greenhouse gas emissions (also material only). The DuPont customer only needs to provide material type, thickness and prices for each layer. DuPont has data for most other variables. Output from the model includes package weight per 1000 in2 or m2, overall thickness, stiffness factor (related to bending stiffness), total material cost, total non-renewable energy (materials) and total greenhouse gas emissions (materials). Figure 7 shows an example of output from analysis of a five-layer film structure for a barrier bag in a box that uses EVA as the sealant. Figure 8 shows the same structure substituting Surlyn as the sealant layer. Figure 7 Example Output Screen, EVA sealant* *Hypothetical Data For Demonstration Purposes Only

8 Tools for Optimizing Flexible Packaging - 8- Figure 8 Example Output Screen, Surlyn sealant* The downgauging LCA model includes provisions for plotting and comparing the stiffness, non-renewable energy consumption and greenhouse gas production of different materials and grades of materials. The charts in Figures 9, 10 and 11 do just that. In this example, switching from an EVA sealant to a Surlyn ionomer sealant allowed a reduction in total thickness, non-renewable energy consumption and greenhouse gas emissions while keeping the bending stiffness constant. Figure 9* Figure 10* Figure 11* *Hypothetical Data For Demonstration Purposes Only

9 Tools for Optimizing Flexible Packaging - 9- Summary Drawing on its knowledge of science and vast experience in packaging, DuPont has developed a number of models and tools for computer-aided analysis and optimization of multilayer packaging films and of the processes employed to make them. Three such tools have been described in this paper. The DuPont Sealant Selector assists packagers and converters in selecting the sealant best suited for a given application. It allows users to compare materials according to the importance of specific attributes, cost and performance for a given application. The DuPont SaVE Sealant Value Estimator allows users to quickly compare the total packaging cost of structures using different sealants. Going beyond material costs, it employs the packager s own data and estimates for costs of labor, overhead and package failures on the filling line and in the field. The DuPont Downgauging and LCA model is a computational tool for maintaining the stiffness of multilayer structures when considering downgauging options. It further assesses the impact of downgauging on material cost, nonrenewable energy consumption and greenhouse gas emissions. Americas DuPont Company, BMP Lancaster Pike & Route 141 Wilmington, DE U.S.A. Telephone Toll-free (USA) DuPont do Brasil, S.A. Alameda Itapecuru, Barueri, SP Brasil Telephone Toll-free: Fax packaging.dupont.com Asia Pacific DuPont China Holding Co., Ltd. Shanghai Branch 399 Keyuan Road, Bldg. 11 Zhangjiang Hi-Tech Park Pudong New District, Shanghai P.R. China (Postcode: ) Telephone Fax Europe/Middle East/Africa DuPont de Nemours Int'l. S.A. 2, Chemin du Pavillon Box 50 CH-1218 Le Grand Saconnex Geneva, Switzerland Telephone Fax CAUTION: The technical data contained herein are guides to the use of DuPont resins. The advice contained herein is based upon tests and information believed to be reliable, but users should not rely upon it absolutely for specific applications because performance properties will vary with processing conditions. It is given and accepted at user s risk and confirmation of its validity and suitability in particular cases should be obtained independently. The DuPont Company makes no guarantees of results and assumes no obligation or liability in connection with its advice. This publication is not to be taken as a license to operate under, or recommendation to infringe, any patents. Copyright 2011 DuPont. The DuPont Oval Logo, The miracles of science, DuPont, and Surlyn are registered trademarks or trademarks of E. I. du Pont de Nemours And Company or its affiliates. K-25342