1.What is polylactic acid?

Polylactide (polylatic acid), abbreviated as PLA, is also called polylactide. It is a thermoplastic polymer obtained by artificial chemical synthesis of lactic acid produced by biological fermentation. It has good biocompatibility and biodegradability.

Chinese alias: polylactide

English name: polylactide, polylactic acid, PLA

English alias: polytrimethylenecarbonate;1,3-Dioxan-2-one homopolymer

Molecular formula: (C3H6O3)n

A single lactic acid molecule has a hydroxyl group and a carboxyl group, multiple lactic acid molecules together, -OH is dehydrated and condensed with the -COOH of other molecules, and -COOH is dehydrated and condensed with the -OH of other molecules. In this way, they are formed hand in hand. The polymer is called polylactic acid. Polylactic acid is also called polylactide and belongs to the polyester family. Polylactic acid is a polymer obtained by polymerization of lactic acid as the main raw material. The raw material source is sufficient and can be regenerated. The production process of polylactic acid is pollution-free, and the product can be biodegraded to realize the circulation in nature, so it is an ideal green polymer material.

2. Basic performance

Polylactic acid (H-[OCHCH3CO]n-OH) has good thermal stability, processing temperature 170～230℃, good solvent resistance, and can be processed in many ways, such as extrusion, spinning, biaxial stretching , Injection blow molding. In addition to being biodegradable, products made of polylactic acid have good biocompatibility, gloss, transparency, hand feel and heat resistance. They can be used as packaging materials, fibers and nonwovens, etc., and are mainly used for clothing (underwear) , Outerwear), industry (construction, agriculture, forestry, papermaking) and medical and health fields.

2.1 Properties

Chinese alias: polylactide

Flexural modulus: 100-150MPa

CAS NO.:26100-51-6

Tensile strength: 40-60MPa

Elongation at break: 4-10%

Elastic modulus: 3000-4000MPa

Physical properties:

Density: 1.20-1.30 kg/L

Melting point: 155-185°C

Intrinsic viscosity IV: 0.2-8 dL/g

Glass transition temperature: 60-65°C

Heat transfer coefficient: 0.025 λ(w/m*k)

Mechanical properties:

Tensile strength: 40-60 MPa

Elongation at break: 4%-10%

Elastic modulus: 3000-4000 MPa

Flexural modulus: 100-150 MPa

Izod impact strength (unnotched): 150-300 J/m

Izod impact strength (notched): 20-60 J/m

Rockwell hardness: 88
2.2 advantages

(1) Polylactic acid is a new type of biodegradable material. It has good biodegradability. After use, it can be completely degraded by microorganisms in nature, and finally carbon dioxide and water are generated without polluting the environment. This is very beneficial to environmental protection. It is recognized as an environmentally friendly material.

(2) Good mechanical and physical properties. Polylactic acid is suitable for various processing methods such as blow molding and thermoplastic, and is easy to process and has a wide range of applications.

(3) Good compatibility and degradability. Polylactic acid is also widely used in the field of medicine, such as the production of disposable infusion equipment, non-dismantling surgical sutures, etc., and low-molecular-weight polylactic acid as a drug sustained-release packaging agent.

(4) In addition to the basic characteristics of biodegradable plastics, polylactic acid also has its own unique characteristics. The strength, transparency and resistance to climate change of traditional biodegradable plastics are not as good as ordinary plastics.

(5) The basic physical properties of polylactic acid and petrochemical synthetic plastics are similar, that is to say, 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, and cannot be provided by other biodegradable products.

(6) Polylactic acid has the best tensile strength and ductility. Polylactic acid can also be produced in various common processing methods.

(7) Polylactic acid film has good air permeability, oxygen permeability and dioxydicarbon permeability, and it also has the characteristics of odor isolation.

(8) When polylactic acid is incinerated, its combustion calorific value is the same as that of incineration paper, which is half of that of traditional plastics (such as polyethylene). In addition, incineration of polylactic acid will never release toxic gases such as nitrides and sulfides. The human body also contains lactic acid in the form of monomer, which shows the safety of this decomposable product.

2.3 Disadvantage

(1) Polylactic acid has a large number of ester bonds and poor hydrophilicity, which reduces its biocompatibility with other substances;

(2) The relative molecular weight distribution of the product obtained by polymerization is too wide, and the polylactic acid itself is a linear polymer, which makes the strength of the polylactic acid material often unable to meet the requirements, high brittleness, and low heat distortion temperature (54°C under a load of 0146MPa) , Poor impact resistance;

(3) The degradation cycle is difficult to control;

(4) The price is too expensive. The price of lactic acid and the polymerization process determine the higher cost of PLA.

3.Application field

3.1 package

Mainly used in packaging bags, packaging films, medical films, foam plastics, tableware, etc.

PLA material has a smooth surface and a high degree of transparency, so it can compete with polystyrene and PET in some applications. PLA has been applied to rigid packaging such as fruits and vegetables, eggs, cooked food and baked goods.

3.2Polylactic acid used in agricultural film

3.3 Polylactic acid is used in the textile field

3.4 Medical treatment

Drug controlled release system, orthopedic fixation, tissue adsorption materials, surgical sutures, oral fixation materials, ophthalmic materials

3.5 3D printing

3.6 Other durable goods (electronics, auto parts, etc.)

The modified polylactic acid PLA can improve the impact resistance, heat resistance, rigidity and flame retardancy of PLA. It has been widely used in the manufacture of computer parts, portable notebook casings, mobile phone parts, DVD player casings, optical discs and home appliance parts, auto parts, etc. PLA and other resins, inorganic materials and other materials can be mixed and compounded to produce New plastic "alloys" with excellent physical properties. These materials have excellent characteristics in terms of antistatic, dimensional stability, tear strength, compressive strength, tensile strength, impact strength, etc., which are ideal new types Environmentally friendly synthetic materials.