Plastics are among the most commonly used materials in the three major synthetic polymer categories—plastics, rubbers, and synthetic fibers. Their applications have become deeply embedded in various sectors of the national economy. Globally, the annual production of plastics has surpassed 1.6 billion tons. However, there remains a significant disparity in how plastic products are consumed across different industries. Currently, the two most widely used areas for plastic products are the packaging and construction industries. Plastic packaging stands out as the leading application, accounting for the largest share, which is nearly 30% of all plastic products. This is about 10% higher than the total amount of plastic building materials, giving it a clear advantage over other uses.
When it comes to packaging materials, plastic has far exceeded traditional options like glass, metal, and wood, ranking just behind paper products. In terms of development speed, plastic packaging materials have outpaced all other types of packaging materials, securing the top position. It’s evident that plastic packaging plays a crucial role in the overall national economy. However, compared to traditional materials, plastic is still a relatively new and emerging material with limited usage history. Many of its potential benefits remain untapped, and some of its performance shortcomings are not yet fully understood, which can lead to improper use. Therefore, it's essential to objectively evaluate and introduce plastic packaging materials during scientific research, production, and application to promote their continued development.
Other notable packaging plastics include polyvinylidene chloride (PVDC), ethylene-vinyl alcohol (EVOH), high acrylonitrile (PAN), and polyvinyl alcohol (PVA). These materials are known for their excellent barrier properties against non-polar gases such as carbon dioxide and nitrogen. Additionally, they exhibit remarkable oil resistance.
In addition to these features, PVDC also offers strong moisture-proof and water-resistant properties, making it an ideal choice for food packaging. It can be applied as a solution or emulsion on films or hollow containers to create a thin protective layer that effectively blocks oxygen and moisture. Despite its high cost and difficulty in processing, as well as the potential release of harmful substances like hydrogen chloride when incinerated, PVDC is still widely used in packaging today.
Ethylene-vinyl alcohol copolymer is considered one of the best barrier plastics and is the top choice for high-barrier materials. It does not emit toxic substances when incinerated, making it environmentally friendly. As a result, it is regarded as an excellent and promising packaging material. However, due to its high price, its use is currently limited to high-end composite bottles, multilayer films, and composite sheets.
High acrylonitrile resins and polyvinyl alcohols are difficult to shape and process, limiting their widespread use. High acrylonitrile resins are mainly used to produce biaxially oriented bottles with good barrier properties, while polyvinyl alcohol is primarily used for film production. Biaxially stretched PVA film serves as the base material for high-barrier composite films, whereas non-stretched PVA film is used for single-layer bags. It is commonly used for high-quality clothing packaging, offering excellent transparency, gloss, vivid printing, and anti-static properties. Unlike regular plastic bags, PVA films do not suffer from static issues, ensuring a better display of the packaged goods.
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