Как используется PLA в упаковке? Преимущества и ограничения

Biodegradable Materials Research Institute

According to reports, the packaging industry has now become a major contributor to "white pollution", and in particular the waste accumulated over the years by the express delivery industry has placed a heavy burden on the planet. Therefore, in recent years the packaging industry has strongly advocated the 3R1D principle of packaging reduction (Reduce), reuse (Reuse), recyclable regeneration (Recycle) and degradability (Degradable),

encouraging research on degradable packaging materials.

In the Opinions on Further Strengthening the Control of Plastic Pollution issued by the National Development and Reform Commission on January 19, 2020, it was explicitly proposed that by the end of 2022, postal and express delivery outlets in Beijing, Shanghai, Jiangsu, Zhejiang, Fujian, Guangdong and other provinces and cities should take the lead in banning the use of non-degradable plastic packaging bags, disposable plastic woven bags and the like, and reduce the use of non-degradable plastic tape. By

the end of 2025, postal and express delivery outlets nationwide will be prohibited from using non-degradable plastic packaging bags, plastic tape, disposable plastic woven bags and the like.

Compared with the traditional packaging materials PE and PP, PLA has high transparency, good processability and good printability, giving it advantages when used as a packaging material. It can be made into films, foamed materials and containers, such as flexible packaging bags, plastic bottles, cushioning materials and disposable tableware.

PLA films mainly include high-transparency films, heat-shrink films, pellet-blended blow-molded film bags and PLA-based composite films.

PLA film can replace traditional film materials as a new type of packaging material. For example, Walmart supermarkets require fully degradable PLA film bags to replace traditional non-degradable PE bags, and Japanese electronic products have also begun to use PLA nanocomposite film packaging.

Due to the degradability of PLA, PLA containers are mostly used in food packaging with a short shelf life.

The transparency and oxygen barrier properties of PLA bottles are better than those of PE bottles. NatureWorks uses PLA bottles to package organic juice drinks, ensuring a 60-day shelf life. The Danish plastics company Faerch uses PLA to package chilled fresh foods such as pasta, meat and salads, achieving a very long shelf life. The European market has launched yogurt cups and beverage packaging bottles made of PLA, which can meet the relevant EU standards for food containers.

The highly transparent, heat-resistant grade PLA water bottles and PLA baby bottles developed by Hangzhou Xusheng Technology Co., Ltd. can meet the application conditions of being both transparent and heat resistant (water bottles and baby bottles require a heat resistance temperature of ≥100°C). In the domestic market, PLA is also coated onto paper to make extrusion-coated paper cups for various water-proof and oil-proof food packaging.

PLA foamed materials

PLA foamed materials are also biodegradable and can be used to produce disposable catering utensils (such as fast-food boxes, instant noodle bowls, etc.) and cushioning pads for packaging, without producing white pollution. For example, the "Graft" series of disposable tableware uses PLA foamed material designed in realistic fruit and vegetable shapes, combining environmental friendliness with aesthetics.

Compared with traditional PE and PP materials, PLA has a higher melting point (about 180°C) and better processability. The hardness and mechanical properties of PLA are similar to those of traditional resins, and it has good transparency and excellent gloss, making it particularly suitable for use as a packaging material.

However, compared with high-barrier nylon, polyvinylidene chloride and the like, PLA has poorer oxygen and water vapor barrier properties and does not provide sufficient protection for foods containing oils and fats. In addition, PLA has poor toughness, a low heat deflection temperature and poor impact resistance, and often cannot meet the requirements of circulation in harsh environments. Moreover, the degradation cycle of PLA is difficult to control, and its price is slightly higher than that of traditional resins (about 30,000 yuan per tonne),

so at present it has no advantage for use in packaging.

Although PLA has shortcomings such as being relatively brittle, not heat resistant and having poor barrier properties,

these shortcomings can be corrected through modification such as copolymerization, blending and plasticization.

In recent years, scholars at home and abroad have been actively studying the polymerization process and modification technology of PLA, and have developed a variety of green packaging materials made from PLA.

——This article is reprinted from China Packaging Network (pack.cn). Original link: http://news.pack.cn/show-378079.html