Inventory of the advantages and disadvantages of PLA and its application in the packaging industry
PLA, an acronym for polylactic acid, is used in three main areas of the market: packaging, medical and textile (fibers), with applications in the packaging industry being particularly prominent.We have PLA sheet extrusion line, which can directly extrude PLA.We have PLA sheet extrusion line, which can directly extrude PLA.We also have other plastic profile extrusion line products.
Compared with traditional PE and PP materials, PLA melting point (about 180 ℃) is higher, better processability. PLA hardness, mechanical properties and traditional resins (such as PS) is similar to a better transparency and excellent gloss, etc., more suitable for use as packaging materials. But the disadvantages are also more prominent, and commonly used high-barrier nylon, polyvinylidene chloride (PVDC), etc., compared to PLA’s oxygen and water vapor barrier is insufficient, the protection of food containing grease is not enough.
Together with the poor toughness, low Tg and poor impact resistance, PLA is destined to be temporarily unsuitable for the packaging field with high durability. In addition, the degradation cycle of PLA is not well controlled, and it is easy to have different degrees of degradation or hydrolysis in use, and its performance will be reduced, and the material cost is more than 2.5 times of traditional PE and PP, which cannot be ignored.
Main performance parameters of PLA
PLA in the packaging industry is mainly benchmarked against modified PP, PE and PET, in addition to cushioning materials benchmarked against EPS, EPE and EPU. in view of the advantages of PLA as a packaging material can be made into films, foam materials and containers, such as flexible packaging bags, plastic bottles, cushioning materials, disposable tableware, etc., from the form of mainly film, followed by containers and sheet materials.
The degradability, barrier properties, mechanical properties, optical properties, antibacterial properties, electrical conductivity and piezoelectricity of PLA are mostly related to the crystallinity. If the crystallinity of PLA is increased, its barrier properties and mechanical properties will generally improve, but the processability, degradability and transparency will usually decrease. Therefore, when modified PLA is used as packaging material, the key is to control its crystallization behavior to optimize all aspects of performance.
(1) PLA film
PLA cast film (left) biaxially oriented film (right)
PLA film mainly has high transparent film, heat-shrinkable film, granular blown film bags and PLA-based composite film. PLA film can replace traditional film materials as new packaging materials, such as Wal-Mart supermarkets require the use of fully degradable PLA film bags to replace the traditional non-degradable PE bags, Japanese electronic products have also begun to use PLA nano-composite film packaging.
(2) PLA containers
PLA bottle (disposable) and water cup
PLA is used in the production of water and juice bottles due to its degradability, but this market is limited. injection-stretch-blow molding is the typical production method for PLA bottles, mostly used in short shelf food packaging. PLA bottles have better transparency and oxygen barrier than PE bottles, and the application of PLA bottles is limited to non-carbonated beverages due to PLA’s lack of creep behavior and low barrier to CO2.
NatureWorks uses PLA bottles to package organic juice drinks with a guaranteed shelf life of 60 days. Faerch Plastics in Denmark uses PLA to package fresh foods such as pasta, meat and salads at low temperatures, which can achieve a long shelf life. The European market has launched yogurt cups and beverage packaging bottles made of PLA that can meet the relevant EU standards for food containers. Some companies have developed highly transparent heat-resistant grade PLA water bottles that can meet the application conditions of both transparency and heat resistance (heat-resistant temperature ≥ 100°C). In the domestic market, PLA is coated on paper to make laminated paper cups, which are used for a variety of waterproof and oil-proof food packaging.
NatureWorks PLA in food and beverage packaging (official website)
(3) PLA foam material
PLA foam tableware
PLA foam is biodegradable and can be used to produce disposable tableware (such as fast food boxes, instant noodle bowls, etc.) and cushion packaging liners without producing white pollution, especially PLA heat-resistant tableware will become more practical. The “Graft” series of disposable tableware is designed with PLA foam in the shape of realistic fruits and vegetables, which is both environmentally friendly and aesthetically pleasing. It is worth noting that foaming is an effective way to use PLA at low cost. The melt strength of pure PLA is low and the melt viscosity is not obvious to shear, so it is not suitable for extrusion coating, foaming and other processing means, but its melt strength can be improved by changing the molecular chain topology, such as long chain branching.We have plastic recycling machine products,for example,plastic recycling machine.If you need, please contact us machine manufacturer.