What are the Advantages of Polylactic Acid?
Polylactic acid (PLA) is thermoplastic aliphatic polyester. Polylactic acid has many advantages as a material.
1. Polylactic acid is a new type of biodegradable material made from starch raw materials derived from renewable plant resources (such as corn). The starch raw material is saccharified to obtain glucose, which is then fermented with glucose and a certain strain of bacteria to produce high-purity lactic acid, and then polylactic acid with a certain molecular weight is synthesized through chemical synthesis. It has good biodegradability and can be completely degraded by microorganisms in nature after use, eventually generating carbon dioxide and water without polluting the environment. This is very beneficial to protecting the environment and is a recognized environmentally friendly material. Ordinary plastics are still disposed of by incineration, which causes a large amount of greenhouse gases to be released into the air, while polylactic acid plastics are buried in the soil and degraded. The carbon dioxide produced directly enters the soil organic matter or is absorbed by plants, and is not released into the air.
2. Polylactic acid has good mechanical and physical properties. Polylactic acid is suitable for various processing methods such as blow molding and thermoplastic. It is easy to process and has a wide range of applications. Polylactic acid can be used to process various plastic products, packaged foods, agricultural fabrics, health care fabrics, floor mats, etc.
3. Polylactic acid has good compatibility and degradability. Polylactic acid is also widely used in the medical field. For example, it can produce disposable infusion equipment, disassembly-free surgical sutures, etc., and low-molecular polylactic acid can be used as drug sustained-release packaging agents.
4. The basic physical properties of polylactic acid and synthetic plastics are similar, which means that it can be widely used to manufacture various application products. Polylactic acid also has good gloss and transparency, which is comparable to films made of polystyrene, which other biodegradable products cannot provide.
5. Polylactic acid has good tensile strength and ductility. Polylactic acid can also be produced by various common processing methods, such as: melt extrusion molding, injection molding, blown film molding, foam molding and vacuum molding. In addition, it has the same printing performance as traditional films. In this way, polylactic acid can be made into a variety of application products to meet the needs of different industries.
6. Polylactic acid film has good air permeability, oxygen permeability and carbon dioxide permeability. It also has the property of isolating odors. Viruses and mold easily adhere to the surface of biodegradable plastics, so there are concerns about safety and hygiene. Polylactic acid is a biodegradable plastic with excellent antibacterial and antifungal properties.
7. When polylactic acid is incinerated, its combustion calorific value is the same as that of incinerated paper, which is half of that of incinerated traditional plastics (such as polyethylene). Moreover, incinerated polylactic acid will never release toxic gases such as nitrogen compounds and sulfides.
What are the Production Methods of Polylactic Acid?
Polylactic acid production uses lactic acid as raw material. Traditional lactic acid fermentation mostly uses starchy raw materials to produce polylactic acid.
1. Condensation polymerization method
The condensation polymerization method is to directly condense lactic acid monomers. In the presence of a dehydrating agent, the hydroxyl and carboxyl groups in the lactic acid molecule are heated and dehydrated, and are directly condensed to form oligomers. Add a catalyst and continue to raise the temperature, and the polylactic acid with a low relative molecular weight will polymerize into a polylactic acid with a higher relative molecular weight.
2. Two-step method
Lactic acid is formed into a cyclic dimer, which is then ring-opened and condensed into polylactic acid. The main process is that after the raw materials are fermented by microorganisms to obtain lactic acid, they are then refined, dehydrated, oligomerized, and cracked at high temperatures, and finally polymerized into polylactic acid.
3. Preparation of high molecular weight polylactic acid by reaction extrusion
Using a combination of a stirring reactor and an extruder to conduct continuous melt polymerization experiments, polylactic acid can be obtained from lactic acid through continuous melt polycondensation. The low molar mass lactic acid prepolymer is further polycondensed on the extruder using an extruder to prepare higher molar mass polylactic acid.
