Improving Manufacturability Through Part and Mold Design for Eastman Tritan ™ Copolyester

1. Improving Manufacturability Through Part and Mold Design for Eastman Tritan™ Copolyester Jeffrey Skelton and Krish Rajagopalan Eastman Specialty Plastics jskelton@eastman.com| 423-224-9694 krish@eastman.com| 919-717-2420

2. What are TritanTM Copolyesters? cyclohexane dimethanol (CHDM) monomer dimethylterephthalate (DMT) monomer tetramethylcyclobutanediol (TMCD) monomer • Basis of Eastman copolyester chemistry; modification of PET with CHDM provides: • Clarity (slow crystallization) • Toughness • Chemical resistance • Slight thermal resistance Critical to Tritan; provides significantly increased thermal resistance Building block for PET, particularly when combined with ethylene glycol (EG; a basic diol) 2

3. Eastman Tritan™ copolyesterBalancing processing and performance properties • Toughness – balancing high visual impact with enduring impact resistance • Tough • Durable • Maintains functional and aesthetic integrity over product life • Clarity – balancing lively aesthetics and long-lived performance • A high level of light transmittance • A low level of haze • High gloss provides vibrant appearance in colored or tinted products Toughness Heat Resistance Clarity Easy processing Chemical resistance • Chemical resistance and hydrolytic stability – tipping the balance in your favor • Eastman Tritan™ copolyester can withstand many harsh chemical environments without crazing, cracking or hazing • Glass transition temperature – balancing heat resistance and easy processing • Reduced molding and sheet-thermoforming cycle times • No need for separate annealing step

4. Eastman Design and Technical Services MATERIAL SELECTION PART DESIGN TOOL DESIGN SECONDARY OPERATIONS PROCESSING

5. Part Design

6. Part design—keys to success

7. Part design—predicted fill pressure • Excessive fill pressure results in: • High clamp tonnage requirements • Reduced life of mold components due to high stress loading • Higher ejection force requirements—possible part deformation or breakage • Running excessive melt temperature to reduce pressure can result in resin degradation. • Eastman Design Services uses mold-filling simulation to estimate required fill pressure. • Guideline of 15,000 psi maximum fill pressure for new part designs

8. Part design—fill pattern • Evaluate fill pattern with mold-filling simulation. • Eliminate potential fill-pattern issues, such as: • Flow-front hesitation • Air traps • Weld lines—locate in unstressed areas if possible.

9. Part design—volumetric shrinkage • Minimize volumetric shrinkage to avoid shrinkage defects such as sinks/voids. • Minimize thick sections to reduce cycle time.

10. Part design—gate location considerations • Aesthetics • Gate leaves a “witness” where the part is separated from the runner system. • This appearance defect is typically hidden in an inconspicuous location. • Mechanical properties • Gate locations typically exhibit mechanical properties inferior to the rest of the cavity. • Gates should be located in areas that are not subjected to externally applied high tensile loading.

11. Part design—eliminate sharp notches • Notches act as stress concentrations during impact loading. Food pan with rim Rounded rim preferred Sharp “notchy” rim

12. Tooling Design

13. Tooling design—keys to success

14. Tooling design—cold gating systems • Successful gate designs for copolyester injection molding include sub, pin, fan, edge, sprue, and diaphragm gates. • Self-degating styles (sub gate, pin gate) typically require smaller gate sizes.

15. Tooling design—sprue gating • High-heat-transfer sprue bushings recommended • Design cooling lines in close proximity. • Slight press fit between sprue bushing/tool steel • Sprue length < 3” • Reduces required ejection force • Reduced pressure losses during fill • Extended machine nozzles can be used to reduce sprue length. • Draw polish existing sprues to improve ejection.

16. Tooling design—hot gating systems • Valve gates recommended when using hot runner systems with Eastman Tritan™ copolyester. • Provide excellent thermal control around gate area • Cooling water circuit in close proximity to gate • Many gate suppliers offer water-jacketed gate. • Consider an independent water supply to control gate water temperature independent from cavity cooling circuit. Cooling water jacket insert

17. Tooling design—need for cooling Coefficient of friction/ejection is significantly higher as steel temperature approaches the glass transition temperature of the material. Higher-Tᶢ copolyesters, such as Eastman Tritan™ copolyester, reduce sticking issues in tooling with cavity “hot spots” compared with lower-Tᶢ copolyesters, such as PET, PETG.

18. Tooling design—cooling techniques Cavity Gate area

19. Tooling design—ejection • Eastman Tritan™ copolyester is more flexible than some competitive resins. • Provide adequate support during ejection • Minimize ejection force requirements. • Polish—polish mold cavity features in the direction of draw • Cooling—no hot spots • Mold steel coatings Part Ejector Ejector

20. Processing

21. Molding essentials: drying Eastman Tritan™copolyester • Drying is critical for efficient processing and retaining polymer molecular weight (IV). • Desiccant drying • Minimum 4 hours at 190°F • Aim for under 0.03% moisture content.

22. Molecular weight as measured by inherent viscosity (IV) affects many polymer properties: • Tensile properties • Impact properties • Heat resistance and creep • Chemical resistance • Viscosity Impact and tensile properties Heat resistance and creep Chemical resistance Property Viscosity Molecular weight/IV Drying is absolutely necessary to maintain properties.

23. Other factors that affect inherent viscosity (IV): • Extreme heat in combination with moisture can cause excessive molecular weight (IV) loss. • Recommended processing conditions for Eastman Tritan™ copolyester: • Under normal conditions, IV loss is ≤ 0.05 or 8%. Effect of melt temperature and residence time

24. Processing tips—injection molding Eastman Tritan™ copolyester • Injection molding recommendations for Tritan • Target melt temperatures in the 520–540°F range • Tool steel surface temperatures 130–150°F to reduce part stress and be below HDT for ejection • Linear part shrinkage in the 0.005–0.007 in./in. range

25. Q&A

26. Technical information disclaimer Any technical information or assistance provided herein is given and accepted at your risk, and neither the sender, Eastman Chemical Company, nor its affiliates makes any warranty relating to it or because of it. Neither Eastman nor its affiliates shall be responsible for the use of this information, or of any product, method or apparatus mentioned, and you must make your own determination as to its suitability and completeness for your own use, for the protection of the environment, and for the health and safety of your employees and purchasers of your products. No warranty is made with respect to the merchantability or fitness of any product; and nothing herein waives or modifies any of Eastman’s conditions of sale.