Polylactic acid, also referred to as PLA, also known as polylactide. It is a thermoplastic polymer obtained by artificial chemical synthesis of lactic acid produced by biological fermentation, with 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
Plastic Pie: Polylactic Acid PLA Structure
A single lactic acid molecule has a hydroxyl group and a carboxyl group, a plurality of lactic acid molecules are together, -OH is dehydrated and condensed with -COOH of another molecule, and -COOH is dehydrated and condensed with -OH of other molecules, so that they are formed by hand. The polymer, called polylactic acid. Polylactic acid, also known as polylactide, belongs to the polyester family. Polylactic acid is a polymer obtained by polymerizing lactic acid as the main raw material. The raw material source is sufficient and can be regenerated. The production process of polylactic acid is non-polluting. And the product can be biodegraded to achieve circulation in nature, so it is an ideal green polymer material.
Basic performance
Polylactic acid (H-'OCHCH3CO'n-OH) has good thermal stability, processing temperature of 170~230 °C, good solvent resistance, and can be processed in various ways, such as extrusion, spinning, biaxial stretching. , Injection blow molding. In addition to biodegradability, products made of polylactic acid, biocompatibility, gloss, transparency, hand and heat resistance, can be used as packaging materials, fibers and nonwovens, etc. Used in clothing (underwear, outerwear), industry (construction, agriculture, forestry, paper) and health care.
1, physical and chemical properties
Chinese alias Polylactide
Flexural modulus 100-150MPa
CAS NO. 26100-51-6
Tensile strength 40-60MPa
Elongation at break 4-10%
Modulus of elasticity 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%
Modulus of elasticity 3000-4000 MPa
Flexural modulus 100-150 MPa
Izod impact strength (no gap) 150-300 J/m
Izod impact strength (with gap) 20-60 J/m
Rockwell hardness 88
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 produces carbon dioxide and water without polluting the environment. This is very beneficial to protect the environment. It is recognized as an environmentally friendly material.
(2) Good mechanical properties and physical properties. Polylactic acid is suitable for various processing methods such as blow molding, thermoplastic molding, etc. It is easy to process and widely used.
(3) Good compatibility and degradability. Polylactic acid is also widely used in the medical field, such as disposable infusion sets, disposable surgical sutures, etc., low molecular weight polylactic acid as drug release packaging.
(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, it can be widely used in the manufacture of various applications. Polylactic acid also has good gloss and transparency, and films made of polystyrene. Quite, other biodegradable products are not available.
(6) Polylactic acid has the best tensile strength and ductility, and polylactic acid can also be produced in various common processing methods.
(7) Polylactic acid film has good gas permeability, oxygen permeability and dioxane, which also has the property of isolating odor.
(8) When polylactic acid is incinerated, its combustion calorific value is the same as that of incinerated paper, and it is half of the incineration of traditional plastics (such as polyethylene), and incineration of polylactic acid will never release toxic gases such as nitrides and sulfides. It also contains lactic acid in the form of a monomer, which indicates the safety of this decomposable product.
3, shortcomings
(1) Polylactic acid has a large number of ester bonds, which is poor in hydrophilicity and reduces its biocompatibility with other substances;
(2) The relative molecular weight distribution of the obtained product is too wide, and the polylactic acid itself is a linear polymer, which makes the strength of the polylactic acid material often fail to meet the requirements, high brittleness, and low heat distortion temperature (54 ° C under a load of 0146 MPa) , 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.
Application field
1, packaging
Mainly used in packaging bags, packaging films, medical films, foam, tableware, etc.
PLA materials have a smooth surface and a high degree of transparency, so they can compete with polystyrene and PET in certain applications. PLA has been used in hard packaging such as fruits and vegetables, eggs, deli and baked goods.
At present, most agricultural films are made of PE, but if they are replaced by degradable polymers such as PLA, they can reduce environmental problems and reduce plastic film loss.
2, textile
3, medical
Drug controlled release system, orthopedic fixation, tissue adsorption material, surgical suture, oral fixation material, ophthalmic material
4, 3D printing
5, other durable goods (electronic field, 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, notebook case, mobile phone parts, DVD player case, CD and home appliance parts, auto parts, etc., PLA and other resins, inorganic materials and other materials can be multi-component blended to produce new plastic 'alloys' with excellent physical properties. These materials are antistatic and dimensionally stable. It has excellent properties in terms of properties, tear strength, compressive strength, tensile strength and impact strength. It is an ideal new environmentally friendly synthetic material.
