Under the influence of the global “plastic restriction” and “plastic prohibition” laws, large-scale plastic restriction has begun in some parts of the world, and domestic plastic prohibition policies have been gradually implemented. The demand for fully degradable plastics continues to grow. Due to its outstanding advantages in other degradable materials, PLA fully degradable plastic bags have become the commonly used degradable plastic bags for hot doors, Can PLA degradable plastic bags alleviate the environmental pressure caused by “white pollution”? The key is that the whole people can afford to use, promote, and the product quality is excellent and stable. Due to the fact that fully degradable plastic bags are not yet popular, you probably don’t know much about them. Today, shunxingyuan packaging, a professional flexible packaging manufacturer, will bring you a detailed understanding of the “popular” PLA fully degradable plastic bag material PLA.
1. PLA degradable plastic bag — what kind of material is PLA
Polylactic acid is a kind of aliphatic hydroxy acid polymer. It is a hard material in glassy state at room temperature. It is converted into carbon dioxide, CH4 and water under the decomposition of microorganisms. It is a typical linear and completely biodegradable material.
PLA can be processed by injection, blow molding, molding, thermoforming and extrusion. The monomer lactic acid of PLA is a chiral molecule. There are two optical enantiomers, L-lactic acid and D-lactic acid. PLA has three configurations. PDLLA and PLLA are two common polymers. The crystallinity of PLLA is related to the content of L monomer. The crystallization rate and crystallinity depend on nucleating agent, time and temperature. The physical properties of PLA are related to the enantiomeric purity of lactic acid stereocopolymer. The homopolymer PLLA and pdla have high regularity and crystallinity.
2. PLA degradable plastic bag — Synthesis of polylactic acid
Lactic acid is the initial raw material for the synthesis of poly (lactic acid). At present, most of the lactic acid producers in China use the microbial fermentation method to produce lactic acid from food crops rich in starch.
2.1 direct method
At 140-210 ℃, in the presence of dehydrating agent, lactic acid molecules were dehydrated and condensed to oligomer by heating, and then the low molecular weight PLA chain was extended to poly (lactic acid) with higher molecular weight.
2.2 indirect method
It is difficult to obtain high molecular weight polylactic acid by direct polycondensation. One of the reasons is that the viscosity of the system increases continuously in the process of polycondensation, so that the generated water cannot be removed. In order to obtain high molecular weight PLA, the first step is to oligomerize lactic acid into low molecular weight PLA. The second step is to decompose lactic acid into cyclic dimer lactide under high temperature and high vacuum. The crude lactide is separated and purified, and the high molecular weight PLA is obtained by ring opening polymerization in the presence of initiator.
3. PLA degradable plastic bag — modification of PLA
3.1 physical modification
Nucleating agent: the addition of nucleating agent can improve the problem of imperfect crystallinity of PLA, improve the crystallinity, and improve the heat resistance and physical properties of PLA.
Plasticizers: adding plasticizers such as glycerol, sorbitol, oligomer peg can improve the processing and mechanical properties of PLA, enhance the toughness and impact resistance of PLA.
Inorganic fillers: commonly used PLA inorganic fillers include kaolin, montmorillonite, calcium carbonate and hydroxyapatite. The addition of fillers can improve the impact strength and thermal decomposition temperature of PLA and reduce the cost.
Blending with other biodegradable plastics: blending PLA with PCL, PBAT, PBS and other biodegradable materials can change the melting point and crystallinity of PLA, so as to improve the mechanical properties.
3. Chemical modification
Chemical modification is to combine the active monomer or group of some compounds with PLA molecule in the form of covalent bond. Compared with physical modification, chemical modification has stronger binding force, mainly including copolymerization modification, grafting modification, chain extension modification and cross-linking modification.
4. PLA fully degradable plastic bag — comparison of properties between polylactic acid (PLA) and main degradable plastics
Polylactic acid (PLA) is a new biodegradable material, which is suitable for extrusion, injection molding, film drawing, spinning and other processing methods. It is easy to process, so it can be used in food packaging, clothing packaging, clothing packaging, fast food lunch boxes, non-woven fabrics, industrial and civil fabrics, agricultural fabrics, 3D printing and other fields.
Radar biotechnology, a professional flexible packaging manufacturer, found that the development and application of polylactic acid (PLA) is particularly rapid. According to statistics, from 2015 to 2020, the annual growth rate of global polylactic acid market will reach 20.9%, and the global polylactic acid consumption market will reach US $5.16 billion by 2020.
Driven by environmental protection policies, biodegradable plastics such as PLA, PBAT, PHA, PCL and PBS are facing new market development opportunities in disposable tableware, packaging, agriculture, automobile, medical treatment, textile and other fields. The biodegradable plastic bags of wuhu radar plastic products Co., Ltd. have passed multiple tests, and have been certified by various industries, which can efficiently meet the mass production. At the same time, shunxingyuan packaging has also made remarkable achievements in the field of recycling packaging bags and degradable packaging bags, and has obtained GRS, d2w and other international certification certificates.
Post time: May-13-2021