Functional plastic packaging materials emerging as the times demand.
Brief of plastic packaging materials in China: the plastic packaging materials are closely related to all kinds of products from industries to our daily lives. Because of their advantages of high performance, low cost and loss pollution, the plastic packaging materials are the kinds with fastest development and broadest applications among the current plastic products, making up at least a half of the total plastic products. It is reported that the domestic demand in 2005 will amount to 4,800,000 tons. The plastic packaging industry in China was still very weak in the 1980s’, and boomed in the 1990s. Within the 10 years from 1991 to 2001, the net increase on output amounted to 1,800,000 tons, symbolizing that the Chinese plastic packaging industry has entered a few stage of fast development. Besides, the continuous and cumulative increase on output has also shown that the plastic packaging industry is the rising sun in the field of plastic products.
Functional packaging materials.
The high-efficient, energy-saving and environmental plastic packaging materials are the current goal for manufacturers in such industry in the world, and the highly separated and multi-functional composite packaging materials processed with modern technology by wonderfully combining the functions of all kinds of materials have come into vogue rapidly. Such packaging materials can suit the different market demands, and realized the selective combination of different functions such as damp resistance, anti-oxygen, anti-carbon dioxide, aroma preservation, freshness preservation, sterilization, slow release, electrostatic resistance, high and low-temperature resistance, and anti aging.
Separated packaging film.
Structure of separated packaging film. Highly separated packaging materials are mostly used for foods. Today, the consumption of packaging films for various foods in China is 80t or so (about 50% of total packaging materials for foods). Because the application of separated packaging films can prolong the preservation period and shelf period of the foods, and keep the foods fresh during the storage, transportation and distribution, they have become the hot spot in the research and development of plastic packaging materials. The separated packaging films are usually compounded by multi-layer composite films, including the base resin (such as LDPE, LLDPE and PP), highly separated materials (such as EVOH, PA and PVDC) and binding resin (such as EVA and EAA). The highly separated packaging films commonly seen are of three layers and five layers, i.e., the three-layer packaging films composed of PA/binding agent/PE, EVOH/binding agent/PE, or PAJ/binding agent/PP, and five layer packaging films composed of LDPE/binding agent/EVOH /binding agent/LDPE, LDPE/binding agent/PA/binding agent/LDPE, or PP/binding agent/EVOH /binding agent/PP.
It shall be noted that m-LLDPE has the superior features of narrow distribution of molecular weight, low hot seal temperature, high strength and strong anti-pierce performance. Therefore, adding a small amount of (such as 25%) m-LLDPE in LDPE or LLDPE can not only improve the physical and mechanical performances of LDPE and LLDPE, but also benefit the hot sealing and printing process. Some separating agent such as PA and EVOH are inapplicable for the inner layer of the multi-layer composite film because of their descending separation performance due to moisture absorption and poor hot seal performance.