Polybutylene adipate terephthalate (PBAT) is a material composed of rigid aromatic chains (terephthalic acid butanediol ester) and flexible aliphatic chains (adipic acid butanediol ester). It is a biodegradable material that can be degraded by microorganisms into water and carbon dioxide. PBAT replaces traditional plastics in the production of packaging materials, medical products, agricultural films, etc.

Polybutylene adipate terephthalate (PBAT) is a typical aliphatic-aromatic copolyester. Its structural formula is:

PBAT is a linear aliphatic-aromatic random copolyester. It is synthesized from 1,4-butanediol (BDO), adipic acid (AA), terephthalic acid (PTA), or dimethyl terephthalate (DMT). There are three esterification methods for preparing PBAT:

 
1) Co-esterification

Schematic diagram of co-esterification process

2) Esterification

Schematic diagram of the esterification process

3) Esterification in Series

Schematic diagram of series esterification process

The high production cost and inadequate comprehensive performance of PBAT limit its market acceptance. Therefore, it is necessary to improve the comprehensive performance and reduce the application cost of PBAT by methods such as adding fillers and biodegradable polymers for melt blending. For example, blending biodegradable materials such as polylactic acid (PLA) and PBAT can improve the rigidity of PBAT while ensuring biodegradability. Blending polypropylene carbonate (PPC) and PBAT can reduce the water vapor permeability of PBAT while ensuring biodegradability, thus improving the tear strength of film bags. Blending organic fillers such as thermoplastic corn starch, cellulose, lignin, organic clay, as well as inorganic fillers such as calcium carbonate, talcum powder, calcium sulfate, silica, titanium dioxide, graphene, etc., with PBAT can ensure the various performance of film bags on the basis of reducing production costs, thus promoting its market application.

Due to the differences in filler composition, modification process formula, and product demand indicators, the recommended addition amounts of different fillers vary. Currently, the recommended addition amounts for film bags are as follows: biodegradable materials PLA (10%), PPC (15%), organic fillers such as thermoplastic corn starch (25%), cellulose (20%), lignin (15%), organic clay (5%). Inorganic fillers such as calcium carbonate (30%), talcum powder (30%), calcium sulfate (25%), silica (15%), titanium dioxide (15%), graphene (2%).

PBT is polybutylene terephthalate, one of the five major engineering plastics. It belongs to the polyester series and is produced by the polycondensation of 1.4-butanediol and phthalic acid (PTA) or terephthalate (DMT). It is a milky white translucent to opaque, crystalline thermoplastic polyester resin made through a mixing process and is widely used in the electronics, electrical and automotive industries.

Polybutylene terephthalate (PBT) is a crystalline thermoplastic engineering plastic polymerized from terephthalic acid and 1,4-butanediol. The molecular structure of the polymer is as follows:

The synthesis of PBT resin is carried out in two steps. The first step is to synthesize butylene terephthalate (BHBT) and its oligomers, and the second step is to condense BHBT into PBT resin under reduced pressure.

Although PBT has excellent comprehensive properties, when used alone, it also has shortcomings such as low heat distortion temperature, easy combustion, shrinkage and warping of parts, and poor mechanical properties, especially the low notch impact strength of products. Therefore, PBT is rarely used alone. Most of them must be modified before they can be used. The modification of PBT mainly starts from two aspects: one is to use chemical modification, that is, to make it have better performance and new functions through chemical methods such as copolymerization, grafting, blocking, cross-linking or degradation; the other is to Physical modification methods are used, that is, by filling and reinforcing inorganic materials, blending with other resins, and adding various additives to improve and improve the comprehensive properties of PBT. Physical modification is extremely effective in developing varieties with different properties. . Common physical modification directions include glass fiber reinforcement, flame retardant and other functional resin blending, and chemical modification directions include chemical chain extension and reaction with low molecular organic compounds and liquid crystals.

Due to differences in filler ingredients, modification process formulas, and product demand indicators, there are certain differences in the amount of different fillers. Currently, the recommended amount of glass fiber for more conventional PBT resin modified products is (20%-40%), and the flame retardant Depending on the flame retardant grade and type of flame retardant, the added amount varies greatly. For example, the added amount of halogen-free flame retardant is generally between 3% and 10%, and the added amount of chain extender during chemical chain extension is generally 3%. About ‰, the general dosage of low molecular organic compound liquid crystal reaction is about 1%.