Release of nano TiO2 from quasi-ceramic coatings

V. Golja1,2, G.Dražić2,3, M. Lorenzetti4, J.Vidmar 2, 4 , J.Ščančar4 , M.Zalaznik5, M.Kalin5, S.Novak2,4

1National Institute of Public Health Slovenia, 2Jožef Stefan International Postgraduate

school, 3 National Institute of Chemistry, Jožef Stefan Institute 4 , University of Ljubljana5

- FCMs containing NPs and concerns

- Characterisation of quasi-ceramic coatings

- Study of nanoTiO2 release:

- migration testing

- mechanical degradation

- Estimated exposure to released NPs

- Conclusions

FCMs containing NPs

- Better properties then conventional materials: non-stick /

self cleaning properties, mechanical properties (increased hardness, scratch resistance), antimicrobial properties, barier properties…

- NPs: nano Ag, nano TiO2, nano SiO2, nano ZnO, nano clays… - packaging, machinery parts, conveyor belts, cookware, A&I

FCMs - Different physico-chemical and biological properties then

bulk counterparts - Presence in FCMs and possible transfer to foods raised

safety concerns

Characterisation of quasi-ceramic pan coatings

Coatings on aluminium substrate, containing

micron- and nano-sized rutile TiO2 particles and quartz SiO2 embedded in a silicone polymer matrix.

SEM + EDXS, FTIR, XRD

Characterisation of quasi-ceramic pan coatings

• Size distribution of nano TiO2 used for production of the coating is not known (commercial sample)

• Size distribution in the coating (assessed from SEM image): 70 to 200 nm

Study of nanoTiO2 release:

Migration tests into simulants (three succesive tests, 2 h at 100 oC):

- 3 % acetic acid,

- deionised water and

- 5g/l citric acid

Particles were separated from ions by ultrafiltration, Ti conc. was determined by ICP MS and max. conc. Of particles recalculated to TiO2

Concentration of Ti in µg /l

Simulant

deionised water

3% acetic acid

citric acid 5g/l

Ions 1st migration 0.058 261 250

2nd migration 0.152 272 675

3rd migration 0.483 247 3636

Particles 1st migration 39 405 100

2nd migration < LOQ 791 7

3rd migration < LOQ 861 0*

LOQ = 0.117 µg/l, *titanium was present only in ionic form

861 µg Ti /l = 1437 µg TiO2 /l =1,4 µg TiO2 /g

Migration into 3% acetic acid : DLS: broad size distribution (polydispersity index 0,480), Deff (effective hydrodynamic diameter): 536 nm (agglomeration)

Study of nanoTiO2 release: • Matrix degradation studies:

Thermal stability: DSC/TG MS analysis

Study of nanoTiO2 release: • Matrix degradation studies:

Mechanical wear: - Scratch test A and B - Tribo test C and D

Results:

• Release of TiO2 particles and Ti ions into food simulants (dissolution from the surface)

• Difference between release into 3 % acetic acid and 5g/l citric acid, the former showing the highest particle migration (861 µg Ti/kg simulant or 1437 µg TiO2/kg simulant or 1,4 µg TiO2/ g food)

• Release due to matrix degradation (mechanical abrasion of matrix due to chipping nature of the coating)

Characterisation of food contact non-stick coatings containing TiO2 nanoparticles and study of their possible release into food, (2017) V.Golja et.al, Food Additives & Contaminants: Part A, 34(3), 421-433.

Real use

1,7 – 3,3 mg of nano TiO2 released in 2 years of use (2 times/week) 8-16 µg nano TiO2 per day Probably underestimation : Release from the surface is not visible