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Reengineering Beauty: The Pros and Cons of Current Crystal Glass Manufacturing Methods Designed to Reduce Lead Migration Presenters: Joseph Pantina Joshua.

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Presentation on theme: "Reengineering Beauty: The Pros and Cons of Current Crystal Glass Manufacturing Methods Designed to Reduce Lead Migration Presenters: Joseph Pantina Joshua."— Presentation transcript:

1 Reengineering Beauty: The Pros and Cons of Current Crystal Glass Manufacturing Methods Designed to Reduce Lead Migration Presenters: Joseph Pantina Joshua Finch Timothy Tirrell Advisors: Dr. Lehman Dr. Crawford

2 ICF Technical Exchange Outline of Presentation Overview of legislation restricting lead exposure and use Summary of the role of lead in crystal –Structure –Migration Review of selected processes to reduce lead migration –Surface Modification –Surface Coatings Discuss advantages/disadvantages

3 ICF Technical Exchange Legislation regarding Lead Proposition 65: California’s Office of Environmental Health Hazard Assessment (OEHHA) Lead leaching must not exceed: ppb (for flatware) -100 ppb (all other tableware) Leaching test use 4% acetic acid solution at 22 o C Products failing to fall below “safe harbor levels” of lead must bear a warning. REACH: Registration, Evaluation, and Authorization of Chemicals European Union initiative Toxic chemicals must be registered upon their production Chemicals must be tracked during all stages of its use in production “Warning: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm.”

4 ICF Technical Exchange Reasons for Lead in Crystal Optical Properties: - Increases index of refraction - Increases dispersion of light Mechanical Properties: - Increases density - Decreases hardness Processing Properties: - Improves glass workability - Increases machinability

5 ICF Technical Exchange Chemical aspects of Lead in Crystal Lead’s role as a glass former: Some fraction of lead atoms occupy glass network positions Covalently bonded to silicon in the silicate structure Lead leaching of lead as a glass former: Negligible for acidic solutions below ph=7 - Due to covalent bonds of lead glass formers Low for alkaline solutions below pH=10 - Slow deterioration of silicate network; releases lead ions High for alkaline solutions above pH=10 - Rapid deterioration of silicate network; releases lead ions Lehman 2002

6 ICF Technical Exchange Chemical aspects of Lead in Crystal (Cont.) Lead’s role as a glass modifier: Large concentrations “open up” the lead silicate structure Modifier lead ions are ionic bonded Effect of acidic solutions: H + /H 3 O + ions compete with Pb 2+ ions, via Coulombic forces Pb 2+ ion replacement forms a silanol layer (non-bridging oxygen) ≡Si-O-Pb-O-Si≡ (s) + 2H 3 O + (sol) 2≡SiOH (s) + Pb 2+ (sol) + 2H 2 O (sol) *Note: 2(≡SiOH) allow for further ion diffusion through the non-bridged structure

7 ICF Technical Exchange Methods to reduce lead leaching must: 1)Maintain the quality and integrity of the original crystal 2)Reduction of lead leach rate below legislative standards 3)Maintain appearance and lowered leach rate after persistent use, including up to 500 dishwasher cycles

8 ICF Technical Exchange Methods for Reducing Lead Leaching Surface Modification: changes the chemical composition of the crystal surface to provide a lead diffusion barrier. Methods: 1) Pre-leaching/acid wash with subsequent annealing 2) Ammonium sulfate Fuming 3) Baccarat Ion Exchange Treatment 4) British Glass Microwave Assisted Ion Exchange Surface Coating: coatings used to provide a lead-free barrier to lead diffusion from a crystal surface Methods: 1) Sol-Gel Coating 2) Chemical Vapor Deposition (CVD) 3) Schott Plasma Impulse Chemical Vapor Deposition (PICVD)

9 ICF Technical Exchange Pre-leaching/acid wash with subsequent annealing Overview: 1)Crystal surface exposed to acidic solution to leach out lead ions 2)Surface layer of silanol is dehydrated by annealing 2(≡SiOH) (s) ≡Si-O-Si≡ (s) + H 2 O (v) 3)Lead deficient silica surface layer is formed Optimized Method: Reduced leach rates 24% Lead Crystal (Lehman 1997) 4% acetic acid solution at 40 o C 9 minute pre-leach time 2 hour annealing at o C Heat

10 ICF Technical Exchange Pre-leaching/acid wash with subsequent annealing (Cont.) Lead leach rates of treated crystal under standard testing with 4% acetic acid solution at 22 o C Lead release in (µg/cm²) as a function of preleach time and annealing temperature Pretreatment Temperature Annealing Temperature0 minutes1 minute9 minute25 minute (ºC) average No detectable lead levels after lead leach test for samples pretreated for 9 minutes and annealed at 200 o C Comparison to lower pre-leach times show that 9 minutes can create a lead deficient silicate layer Annealing temperature trends suggest that a heat treatment of at least 200 o C is needed to densify the lead deficient layer to block further lead leaching

11 ICF Technical Exchange Ammonium Sulfate Fuming Overview: Ammonium sulfate is added to pre-annealed crystal At annealing temperature, ammonium sulfate reacts with lead and potassium cations. (NH 4 ) 2 SO 4 + Pb 2+ + K 1+ PbSO 4 + K 2 SO4 + NH 3 + H 2 Potassium and lead sulfate are precipitated on the crystal surface Precipitates can be washed away to leave a lead depleted crystal surface layer

12 ICF Technical Exchange Ammonium Sulfate Fuming (Cont.) British Glass investigated the addition of 0.1 g ammonium sulfate to crystal before annealing Crystal annealed at 490 o C Precipitates were analyzed by chemical analysis, confirming the composition as potassium and lead sulfate Standard Testing in a 4% acetic acid at 22 o C X-ray photoelectron spectroscopy (XPS) of the treated surface shows a 1/3 of Pb and 1/6 of K ions still remain compared to the untreated surface UntreatedTreated 600 ppb Pb40 ppb Pb

13 ICF Technical Exchange Baccarat Ion-exchange Treatment Details obtained from: “Process for treating lead glass to form a lead diffusion barrier in the surface thereof.” (US Patent # ) Overview: An ion exchange slip is selected to provide non-toxic metal glass forming ions for exchange with lead ions. Crystal surface is coated with ion exchange slip Bulk crystal is heat treated to increase the diffusion rate of ions (Fick’s Law) Non-toxic ions replace lead to form a diffusion barrier to further lead migration in the surface layer Removal of “cemented” slip on the crystal surface

14 ICF Technical Exchange Baccarat Ion-exchange Treatment (Cont.) Type of slip utilized: Kaolin or hydrated aluminum silicate - Both slips provide Al 3+ ions in aqueous solutions - Thixotropic viscous behavior maintains thickness under gravity Heating Cycle: - gradual heating to o C hour hold between o C - 3 hour cooling to room temperature

15 ICF Technical Exchange Baccarat Ion-exchange Treatment: Results Leaching studies done on treated crystal containing between 1%-40% PbO, all show greatly reduced leaching levels compared to untreated crystal Secondary Ion Mass Spectroscopy (SIMS) shows a silico-aluminous layer of at least 20 nm; normally ranging between nm Lead Leaching Test of Baccarat Surface Treated 30% PbO Crystal with a 4% acetic acid solution (pH=2.3) and with an alcohol solution (pH=3.5) Time Elapsed (Months) Lead Concentration (µg/L) Acetic Acid Alcohol

16 ICF Technical Exchange British Glass Microwave Assisted Ion Exchange Overview: Researches at British Glass investigated the use of different non-toxic metal ions (Al, Ti, Zr, Sr) for ceramic ion exchange slips using a microwave heat treatment Crystal is pre-leached in 4% acetic acid at 90 o C for 10 minutes. Crystal is coated with ion exchange slip Microwave exposure of 2.45 Ghz, 500 watt source for 10 minutes Remove hardened slip from the crystal surface.

17 ICF Technical Exchange British Glass Microwave Assisted Ion Exchange (Cont.) Advantages of Microwave Heating: Crystal is transparent at microwave (Ghz) frequency High absorption of radiation from ion-exchange slip at the crystal surface Surface heating increases surface ion diffusion Bulk crystal is not affected by the heat treatment Oscillating electromagnetic wave can assist migration of charged ions

18 ICF Technical Exchange British Glass Microwave Assisted Ion Exchange: Results All slips show superior performance to no treatment or acid washing in long term tests. Prompted the refinement of the crystal surface treatment to reduce processing time and cost. Used 2h leach time and two stage 10min microwave treatment Refined method tested with a titanium ion exchange slip Treatment24 Hour 4% Acetic Acid (ppb Pb) 4 Month 4% Acetic Acid (ppb Pb) Control (no Treatment) Ti (Not Recorded) <25 XPS characterization of treated crystal shows a silica rich surface with small amounts of titania SEM reveals no surface damage after treatment

19 ICF Technical Exchange Sol-Gel Method Hydrolysis of a Silicon Alkoxide: (C 2 H 5 O) 4 -Si +H2O (C 2 H 5 O) 3 -Si-OH + C 2 H 5 OH(1) Condensation Polymerization Reaction: -Si-OH + OH-Si- -Si-O-Si- + H2O (2) Previous tests have shown no detectable lead leaching after coating, but results in unappealing optical qualities. Coatings ≤ 2 µm Possible

20 ICF Technical Exchange Chemical Vapor Deposition CVD of thin films of phosphorous doped titania and zirconia for lead diffusion barrier Tested By: Metaleurop Recherche and the Laboratory of Materials of the Polytechnic Institute, Grenoble Source gas: Metal-organic precursors volatilized by ultrasonication at low pressures Precursor gases mix in proper proportions with carrier gas Pyrolysis of precursor gas take place at the surface of a heated crystal substrate Heterogenous nucleation of film occurs at crystal surface

21 ICF Technical Exchange Chemical Vapor Deposition: Results Process only tested on 2 cm 2 flat crystal samples - Control of film uniformity posses a problem for complex shapes Low leach rates were reported (not replicated by further tests) Thermal expansion of titania and zirconia are different than crystal - Cooling the crystal after coating will cause strain at the interface - Interface strain can lead to delamination

22 ICF Technical Exchange Schott Glass - PICVD Plasma Impulse Chemical Vapor Deposition (PICVD) Developed By: Schott Glass Primary Uses: Coating low melting point glass and polymer tubes and containers with quartz-like coatings Microwave radiation is used to decompose precursor gas

23 ICF Technical Exchange Schott Glass – PICVD (Surface Coating Inspection) Stage 1 - Two in-situ surface characterization methods - Optical Plasma Emission - Temperature Stage 2 - Thickness controlled by online manipulation of gas flow, vacuum pressure, and microwave energy Stage 3 – System Monitoring - Automatic calibration of sensors - Automatic data collection and archiving

24 ICF Technical Exchange Schott Glass – PICVD Durability and Leaching Results: Comparison between Type 1 and Type 1 plus pharmaceutical glassware Coating Maintained after Autoclaving Tests w/ SolutionDuration (Hours) Temperature (°C) 0.1 M HCL6121 NaOH (pH=10)1121 3% EDTA (pH=4.5)1121 3% Citric acid1121

25 ICF Technical Exchange Surface Modification can… Reduce lead leaching below Proposition 65 standards Maintain the crystal’s original optical qualities However, Conventional heating near glass softening temperature is often needed for some processes Processes rely on slow chemical reactions to remove lead from the crystal surface Microwave processes are needed to reduce processing time Lead removed from the crystal surface is a disposal issue

26 ICF Technical Exchange Surface Coating can… Provide a lead-free diffusion barrier to lead migration Be applied using a wide range of processing techniques at different temperatures However, Uniformity of the coating can present difficulties in certain coating processes Incomplete coatings result in high lead leaching rates Optical and mechanical properties of the surface coating must be similar to the properties of the coated crystal

27 ICF Technical Exchange References 1.Copley, G. J., & Kennedy, J. (1993a). British Glass, & Waterford Crystal. Microwave Surface Treatment For Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA. 2.Copley, G. J., Dalton, D. A., & Glendenning, M. D. (1993b). British Glass. Full Lead Crystal: Report on Surface Modification. Paper presented at ICF Technical Exchange Conference, Waterford, Ireland. 3.Cornier, G., & Baccarat, Compagnie des Cristalleries de Baccarat. (1994). U.S. Patent No. 5,308,652. Washington, DC: U.S. Patent and Trademark Office. 4.Kear, B. H. (2007, Fall). Stuctural/Mechanical/Chemical Properties of Nanomaterials. MSE 14:635:401: Rutgers University. 5.Kliokis, J., Lehman, R. L., & Strange, D. J. (1997). Rutgers University: Center for Ceramics Research. Effects of Surface Treatments on Lead Migration from Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Estoril, Portugal. 6.Lehman, R. L., & Rabii, C. (1993a). Rutgers University: Center for Ceramics Research. The Effects of Surface Treatments on Lead Release of Lead Crystal Glass. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA. 7.Lehman, R. L. (1995). Rutgers University: Center for Ceramic Research. The Structure of Lead-Containing Silicate Glasses and Approaches to Improve Durability. Paper presented at ICF Technical Exchange Conference, Orrefors, Sweden. 8.Lehman, R. L., & Strange, D. J. (1996). Rutgers University: Center for Ceramics Research. Surface Treatment Of Lead Crystal: Optimized Stabilization of the Surface Layers of Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Stourbridge, UK. 9.Lehman, R. L. (2002). Rutgers University: Center for Ceramics Research. Lead Migration from Crystal Glassware: Developments From 12 Years of ICF TECs. Powerpoint preseneted at ICF Technical Exchange Conference, Waterford, Ireland. 10.OEHHA. (2007). OEHHA Proposition 65: Proposition 65 FAQs. Retrieved October, 12th, 2007, from Office of Environmental Health Hazard Assessment Website: 11.Perrier, E. (1993a). Metaleurop Recherche. Protective Coating For Crystal Glass. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA. 12.Potts, J. (1992). Lead Migration Reduction at Lenox. Paper presented at ICF Technical Exchange Conference, Colle Val d’Elsa, Italy. 13.Schott Glass (2007). Schott Type 1 Plus®: Container with a quartz-like inner surface [Pamphlet]. US: Schott Glass.


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