Differences in waterproof properties of plastic foils: Exploration of materials science and application

Polyester film (PET): a model of high-performance waterproofing
Polyester film, with its high strength, high transparency, good heat resistance and excellent chemical stability, has become the preferred material for many high-end packaging and electronic product protection. The ester bond structure in the PET molecular chain gives it a tight molecular arrangement, which can effectively block the penetration of water molecules. In addition, PET film can be further enhanced through surface coating or composite treatment technology to meet more stringent moisture-proof requirements. For example, in food packaging, PET film can effectively extend the shelf life of the product and prevent food from deteriorating due to moisture.

Polypropylene film (PP): the preferred choice for balancing cost and performance
Polypropylene film is widely used in food packaging, agricultural covering, stationery manufacturing and other fields due to its good processability, light weight and relatively low cost. The waterproof performance of PP is mainly due to its non-polar molecular structure, which makes it difficult for water molecules to penetrate through the molecular gap. Although PP may be less water-resistant than PET, the water-resistant properties of PP films can be significantly improved through special processing, such as adding water-repellents or multi-layer co-extrusion. In agriculture, modified PP films can effectively prevent rainwater from directly penetrating the soil, while maintaining soil moisture and promoting crop growth.

Polyethylene film (PE): a trade-off between cost and performance
Polyethylene film is one of the most common plastic foils on the market due to its low cost, good flexibility and wide applicability. However, the water-resistant properties of PE are generally more limited than those of PET and PP. This is mainly because PE's molecular chains are looser, and water molecules can more easily penetrate through the tiny gaps between molecules. Nevertheless, its water-resistant properties can be significantly improved through the production technology of high-density polyethylene (HDPE). HDPE's molecular chains are more tightly arranged, which can effectively block water, so it is often used in underground pipes, waterproof membranes and some high-end packaging materials.

The relationship between material science and water-resistant properties
The water-resistant properties of plastic foils depend not only on the characteristics of their base materials, but also on a variety of factors such as processing methods, additives used, and surface treatment. For example, through physical treatments such as stretching and orientation, the molecular orientation of plastic foil can be enhanced, thereby improving its waterproof performance. In addition, chemical modification methods such as adding nanoparticles and waterproofing agents can also effectively improve the waterproof level of materials. The scientific principles behind these technologies involve multiple disciplines such as polymer physics, chemical modification, and interface science, and are one of the hot spots in materials science research.

Application prospects and challenges
As the concept of sustainable development has become more popular, the development of environmentally friendly, degradable and waterproof plastic foil has become a future trend. New materials such as bio-based plastics and PLA (polylactic acid) are gradually entering the market. They not only have excellent waterproof properties, but also can be naturally degraded after being discarded, reducing environmental pollution. However, how to reduce production costs, improve production efficiency, and solve the stability problems of degradable plastics during processing and use while maintaining waterproof performance are the current challenges.