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Why is it said that PET plastic bottles have good chemical stability
source：m.tiandisuo.com.cn | Release time：2025-07-28
The good chemical stability of PET (polyethylene terephthalate) plastic bottles is mainly due to their molecular structure characteristics and the physical and chemical properties of the material itself. The specific reasons are as follows:
1. Stable molecular structure and chemical corrosion resistance
PET is formed by the condensation reaction of terephthalic acid and ethylene glycol, and its molecular chain contains a large number of ester groups (- COO -) and benzene ring structures.
The benzene ring is a rigid structure that endows the molecular chain with high stability and is not easily damaged by general chemical substances;
Although ester groups are polar groups, the overall molecular chain arrangement is regular and the crystallinity is high (especially for PET bottles after stretch blow molding, the crystallinity can reach 30% -50%). The intermolecular forces are strong, making it difficult for most acids, bases, and organic solvents to penetrate or decompose their structure.
For example, PET has good corrosion resistance to water, alcohol, weak acids (such as carbonic acid in carbonated beverages), neutral solutions, etc., and will not dissolve, swell, or degrade due to long-term contact.
2. Wide temperature resistance range and resistance to environmental aging
The glass transition temperature of PET is about 70-80 ℃, and the softening point is about 240 ℃. Its performance is stable at room temperature (-40 ℃ to 60 ℃), and it will not undergo significant deformation or chemical decomposition due to temperature fluctuations.
Its molecular structure has strong tolerance to ultraviolet radiation and oxygen, and is not easily oxidized or degraded when exposed to air for a long time. Therefore, PET bottles have a longer shelf life and can effectively protect their contents (such as beverages, cosmetics, etc.) from contamination.
3. Do not react with most of the contents
In common usage scenarios, PET bottles have good compatibility with their contents:
For common liquids such as water, fruit juice, carbonated beverages, edible oil, cosmetics, etc., PET does not release harmful substances, nor does it change the composition or flavor of the contents due to chemical reactions;
Compared to other plastics such as PVC, which is prone to release plasticizers, and PC, which may contain bisphenol A, PET has higher chemical inertness and is particularly suitable for fields such as food and pharmaceuticals that require strict safety requirements.
4. Enhance stability during processing
The production of PET bottles requires stretch blow molding technology, which further orients and arranges the molecular chains, improves crystallinity, and not only enhances the mechanical strength (impact resistance, deformation resistance) of the bottle body, but also further improves its chemical stability - the tightly arranged molecular structure is more difficult to be eroded by external chemical substances.
1. Stable molecular structure and chemical corrosion resistance
PET is formed by the condensation reaction of terephthalic acid and ethylene glycol, and its molecular chain contains a large number of ester groups (- COO -) and benzene ring structures.
The benzene ring is a rigid structure that endows the molecular chain with high stability and is not easily damaged by general chemical substances;
Although ester groups are polar groups, the overall molecular chain arrangement is regular and the crystallinity is high (especially for PET bottles after stretch blow molding, the crystallinity can reach 30% -50%). The intermolecular forces are strong, making it difficult for most acids, bases, and organic solvents to penetrate or decompose their structure.
For example, PET has good corrosion resistance to water, alcohol, weak acids (such as carbonic acid in carbonated beverages), neutral solutions, etc., and will not dissolve, swell, or degrade due to long-term contact.
2. Wide temperature resistance range and resistance to environmental aging
The glass transition temperature of PET is about 70-80 ℃, and the softening point is about 240 ℃. Its performance is stable at room temperature (-40 ℃ to 60 ℃), and it will not undergo significant deformation or chemical decomposition due to temperature fluctuations.
Its molecular structure has strong tolerance to ultraviolet radiation and oxygen, and is not easily oxidized or degraded when exposed to air for a long time. Therefore, PET bottles have a longer shelf life and can effectively protect their contents (such as beverages, cosmetics, etc.) from contamination.
3. Do not react with most of the contents
In common usage scenarios, PET bottles have good compatibility with their contents:
For common liquids such as water, fruit juice, carbonated beverages, edible oil, cosmetics, etc., PET does not release harmful substances, nor does it change the composition or flavor of the contents due to chemical reactions;
Compared to other plastics such as PVC, which is prone to release plasticizers, and PC, which may contain bisphenol A, PET has higher chemical inertness and is particularly suitable for fields such as food and pharmaceuticals that require strict safety requirements.
4. Enhance stability during processing
The production of PET bottles requires stretch blow molding technology, which further orients and arranges the molecular chains, improves crystallinity, and not only enhances the mechanical strength (impact resistance, deformation resistance) of the bottle body, but also further improves its chemical stability - the tightly arranged molecular structure is more difficult to be eroded by external chemical substances.
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