Evaluating the Chemical Resistance and Performance of Thermochromic Polymers for Food Packaging

Abstract

The use of thermochromic pigments in food packaging offers several advantages, including improved food safety, waste reduction, and temperature change monitoring. However, little is known about how chemically resilient these materials are, especially regarding optical stability, thermochromic activation, and mechanical integrity following exposure to acidic, alkaline, oil-based, and neutral food-contact environments. This study evaluates the chemical resistance, thermal cycling effects, and mechanical durability of thermochromic pigment-polymer blends. Thermochromic polymer samples were subjected to multiple chemical environments, repeated thermal cycling, and mechanical analysis to assess degradation behavior. The findings show that virgin food-grade polymer with no thermochromic pigment sustains its performance stability throughout chemical exposure with little degradation. However, thermochromic polymer blends experienced reduced thermochromic functionality. This study offers insight into how well thermochromic pigment can be incorporated into intelligent food packaging despite the limitations associated with chemical exposure.

Keywords: chemical resistance; food packaging; mechanical durability; thermal cycling; thermochromic pigments.

Figure 1

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure to lemon juice. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 2

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure to orange juice. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 3

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure to tap water. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 4

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure hydroalcoholic solution. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 5

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure to vegetable oil. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 6

Visual color changes in (A) HDPE100/TP0, (B) HDPE98/TP2, and (C) HDPE92/TP8 before and after exposure to bleach solution. Each set shows samples in the following order: unexposed (control), 24 h, 48 h, and 72 h. Images are representative of five replicate specimens per condition (n = 5).

Figure 7

SEM micrographs of HDPE100/TP0 post-72 h exposure at 100× magnification: (A) lemon juice, (B) orange juice, (C) tap water, (D) hydroalcoholic solution, (E) vegetable oil, and (F) bleach solution.

Figure 8

SEM micrographs of HDPE98/TP2 post-72 h exposure at 100× magnification: (A) lemon juice, (B) orange juice, (C) tap water, (D) hydroalcoholic solution, (E) vegetable oil, and (F) bleach solution.

Figure 9

SEM micrographs of HDPE92/TP8 post-72 h exposure at 100× magnification: (A) lemon juice, (B) orange juice, (C) tap water, (D) hydroalcoholic solution, (E) vegetable oil, and (F) bleach solution.