## 2 Results
### Migration, Weight Increase and Visual Changes of GPPS and HIPS with Food Simulants
#### 2.2.4 Weight Increase Using the Food Simulants 20% Ethanol, 10% Ethanol and 3% Acetic Acid  
The results of the weight increase of GPPS and HIPS in contact with the aqueous food simulants are given in Figures 10 and 11.  
Figure 8: Migration kinetics and weight increase in 50% ethanol at 40 \({}^{\circ}\)C: (**a**) Model substances and styrene from GPPS; (**b**) Model substances and styrene from HIPS. Note: Due to analytical interferences, migration of methylslearate from GPPS and HIPS and of phenylylohexane from GPPS in 50% ethanol at 40 \({}^{\circ}\)C can not be measured.  
Figure 9: Migration kinetics and weight increase in 50% ethanol at 20 \({}^{\circ}\)C from HIPS. Note: Due to analytical interferences, migration of methyl slearate from HIPS in 50% ethanol at 20 \({}^{\circ}\)C can not be measured.  
In case of GPPS, weight increase was measurable only after contact with 20% ethanol while remained \(<\) 0.1% using 10% ethanol and 3% acetic acid. With 20% ethanol it was found constant at 60 \({}^{\circ}\)C and it increases at 40 \({}^{\circ}\)C until 20 days reaching a weight increase of 0.5%. At 20 \({}^{\circ}\)C, the weight of GPPS increases from 0.2% after 10 days to 0.4 after 90 days. Regarding HIPS, a weight increase was measurable at all tested conditions. With 20% and 10% ethanol at 60 \({}^{\circ}\)C the weight increase showed two sequential linear regions: in the first part (until approx. 100 days) weight increased slowly remaining \(<\) 1% while in the second part it increases faster without reaching a plateau. At the end of the storage time, a weight increase of 3.8% after 200 days for 20% ethanol and 3.3% after 273 days for 10% ethanol was detected. After 10 days contact with the food simulant 20% ethanol, the weight increase of the HIPS polymer was determined to be 0.4% at 20 \({}^{\circ}\)C, 0.6% at 40 \({}^{\circ}\)C and 0.7% at 60 \({}^{\circ}\)C. After 10 days contact with the food simulant 10% ethanol, the weight increase of the HIPS polymer was determined to be 0.25% at 20 \({}^{\circ}\)C, 0.3% at 40 \({}^{\circ}\)C and 0.4% at 60 \({}^{\circ}\)C. In the food simulant 3% acetic acid the higher weight increase was determined after 273 days at 60 \({}^{\circ}\)C (1.2%). After a storage time of only 10 days the weight increase was 0.2% at 20 \({}^{\circ}\)C and 40 \({}^{\circ}\)C, respectively, and 0.4% at 60 \({}^{\circ}\)C.  
Figure 11: Weight increase of HIPS in aqueous food simulants at 20, 40 and 60 \({}^{\circ}\)C for storage times up to 250 days.  
Figure 10: Weight increase of GPPS in 20% ethanol at 20, 40 and 60 \({}^{\circ}\)C for storage times up to 140 days.  
Concerning visual testing after migration experiments, for GPPS no visual changes were observed after contact with the food simulants 20% ethanol, 10% ethanol and 3% acetic acid at 20 \({}^{\circ}\)C, 40 \({}^{\circ}\)C and 60 \({}^{\circ}\)C within the storage of up to 140 days. For HIPS, some visual changes were observed with these simulants only at 40 and 60 \({}^{\circ}\)C after prolonged times of exposure. With 20% ethanol the samples changed color to slightly yellow after 16 days at 60 \({}^{\circ}\)C and after 126 days at 40 \({}^{\circ}\)C. With 10% ethanol and 3% acetic acid samples become slightly yellow after 30 days at 60 \({}^{\circ}\)C and after 126 days at 40 \({}^{\circ}\)C.