## 2 Results
### Migration, Weight Increase and Visual Changes of GPPS and HIPS with Food Simulants
#### 2.2.2 Migration Kinetics and Weight Increase Using the Food Simulant 95% Ethanol  
The migration kinetics and the weight increase of GPPS and HIPS into 95% ethanol at 60 \({}^{\circ}\)C are shown in Figure 4.  
The relative migration of the model substances and styrene into 95% ethanol are high. However, for both investigated polymers, significant differences in the migration behavior of the volatile substances compared with the lower volatiles were observed. In case of the volatile substances toluene, chlorobenzene and styrene, the migration curves are steeply rising and reach approx. 80% after 10 days of contact from both GPPS and HIPS approaching plateau after approximately 14 days. The migration curves of the lower volatiles increased more slowly and were still increasing after 115 days contact. Migration was at most 30% for benzophenone after 10 days. Migration of styrene oligomers from GPPS in 95% ethanol was drastically lower compared to isootcane tested at the same temperature. Also in case of HIPS, it was significantly lower. After 100 days oligomer migration reached max. 40% for GPPS and 20% for HIPS.  
Figure 3: Migration and swelling kinetics in isootcane at 20 \({}^{\circ}\)C from HIPS: (**a**) Model substances and styrene; (**b**) Styrene oligomers.  
As regard the weight increase in 95% ethanol at 60 \({}^{\circ}\)C, in an initial step (after 1 day contact) the measured weight increase for both polymers reaches 3% and approaches more slowly up to 15% after 200 days in case of GPPS and up to 34% after 273 days for HIPS (see Supplementary material: Tabulated data). At the testing conditions 60 \({}^{\circ}\)C for 10 days or 60 \({}^{\circ}\)C for 1 day using 95% ethanol as food simulant, the GPPS and HIPS polymers are significantly swollen. Additionally, the test specimens of both polymers used for the migration experiments were deformed (curved) already after 1 day contact (see Supplementary material: Photos of visual changes).  
The migration kinetics and weight increase of GPPS and HIPS into 95% ethanol at 40 \({}^{\circ}\)C are depicted in Figure 5. The relative migration of oligomers into 95% ethanol at 40 \({}^{\circ}\)C was below 1% after 10 days (see Supplementary material: Tabulated data).  
As at 60 \({}^{\circ}\)C, the relative migration of the volatiles at 40 \({}^{\circ}\)C is higher compared to the lower volatiles, reaching up to 20% (GPPS) and 30% (HIPS) after 10 days. The migration of the other compounds increases slowly and remains below 10% after 100 days.  
Regarding the weight increase using 95% ethanol at 40 \({}^{\circ}\)C, an initial linear rapid increase was observed. After 10 days the weight increase reached approx. 3% for both poly-mers. However, significant visible changes of the test specimens were not noted. Only the HIPS samples appeared slightly yellow only after 44 days contact with 95% ethanol at 40 \({}^{\circ}\)C (see Supplementary material: Photos of visual changes).  
The migration kinetics and weight increase of GPPS and HIPS into 95% ethanol at 20 \({}^{\circ}\)C are depicted in Figure 6. Relative migration of styrene oligomers from GPPS and HIPS in 95% ethanol at 20 \({}^{\circ}\)C (see Supplementary material: Tabulated data) was below 1% until 105 days (GPPS) and 202 days (HIPS).  
Figure 4: Migration kinetics and weight increase in 95% ethanol at 60 \({}^{\circ}\)C: (**a**) Model substances and styrene from GPPS; (**b**) Styrene oligomers from GPPS. (**c**) Model substances and styrene from HIPS; (**d**) Styrene oligomers from HIPS.  
Figure 5: Migration kinetics and weight increase in 95% ethanol at 40 \({}^{\circ}\)C: (**a**) Model substances and styrene from GPPS; (**b**) Styrene oligomers from GPPS. (**c**) Model substances and styrene from HIPS; (**d**) Styrene oligomers from HIPS.  
Figure 6: Migration and weight increase in 95% ethanol at 20 \({}^{\circ}\)C: (**a**) Model substances and styrene from GPPS; (**b**) Model substances and styrene from HIPS.