PLA in Packaging: Performance Strengths, Barrier Gaps and Modification Routes

The Biodegradable Materials Research Institute reports that packaging has become a significant contributor to white pollution, with waste accumulating over years in express delivery putting heavy pressure on the environment.

In response, the packaging sector has been promoting the 3R1D framework—Reduce, Reuse, Recycle and Degradable—while supporting R&D into degradable packaging materials.

On January 19, 2020, the National Development and Reform Commission issued the Opinions on Further Strengthening the Control of Plastic Pollution, setting phased restrictions on non-degradable plastic packaging.

The document required postal and express delivery outlets in Beijing, Shanghai, Jiangsu, Zhejiang, Fujian, Guangdong and other provinces and cities to take the lead by the end of 2022 in banning non-degradable plastic packaging bags, disposable plastic woven bags and similar items, while cutting 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 comparable products.

Compared with conventional PE and PP packaging materials, PLA offers clear advantages in transparency, processability and printability. It can be converted into films, foamed materials and containers for flexible packaging bags, plastic bottles, cushioning materials and disposable tableware.

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

These films can replace traditional films in new packaging formats. Walmart requires fully degradable PLA film bags instead of conventional non-degradable PE bags, and Japanese electronics makers have begun using PLA nanocomposite film packaging.

Because PLA is degradable, PLA containers are mainly used for food packaging with short shelf life.

PLA bottles outperform PE bottles in transparency and oxygen barrier performance. NatureWorks uses PLA bottles for organic juice drinks, delivering a 60-day shelf life. Denmark’s Faerch uses PLA to package chilled fresh foods such as pasta, meat and salads, achieving a long shelf life. Europe has also introduced PLA yogurt cups and beverage bottles that meet relevant EU food container standards.

Hangzhou Xusheng Technology Co., Ltd. has developed high-transparency, heat-resistant PLA water bottles and baby bottles that meet requirements for both clarity and heat resistance; water bottles and baby bottles need to withstand temperatures of at least 100°C. In China, PLA is also coated onto paper to make extrusion-coated paper cups for water- and oil-resistant food packaging.

PLA foamed materials

PLA foamed materials are biodegradable as well. They can be used for disposable catering items such as fast-food boxes and instant noodle bowls, and for cushioning pads in packaging, without creating white pollution. The Graft series of disposable tableware uses PLA foamed material shaped like realistic fruits and vegetables, combining environmental benefits with visual appeal.

Compared with traditional PE and PP, PLA has a higher melting point of about 180°C and good processability. Its hardness and mechanical properties are close to those of conventional resins, and it offers good transparency and excellent gloss, making it well suited to packaging.

However, versus high-barrier nylon and polyvinylidene chloride, PLA provides weaker oxygen and water vapor barrier performance and insufficient protection for oily foods. It also has poor toughness, a low heat deflection temperature and weak impact resistance, so it often cannot withstand harsh distribution conditions. Its degradation cycle is difficult to control, and its price is higher than traditional resins at about RMB 30,000 per tonne.

At this stage, therefore, PLA does not hold a clear advantage in packaging applications.

Although PLA is relatively brittle, not heat resistant and weak in barrier performance,

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

In recent years, scholars in China and abroad have been actively studying PLA polymerization and modification technologies, developing a range of green packaging materials based on PLA.

Source: China Packaging Network (pack.cn); original article: http://news.pack.cn/show-378079.html