Study on crystallization properties of the hottest

2022-09-22
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With the rapid development of packaging industry, pet is widely used in packaging bottles, especially disposable packaging bottles. At present, China produces hundreds of thousands of waste PET bottles every year, which not only causes a huge waste of resources and energy, but also causes "white pollution". How to effectively recycle waste PET bottles, save resources and reduce environmental pollution has become a global concern. At the same time, the research on the crystallinity of pet is also crucial to the development of PET engineering plastics, and there have been quite a number of research reports

in this experiment, the recycled PET bottle is used as raw material. By adding crystallization nucleating agent and crystallization accelerator, the engineering plastic used as composite material is prepared. In the first half of the year, mtmarion will provide nearly 130000 tons of lithium concentrate resin, and the influence of crystallization nucleating agent and crystallization accelerator on the crystallization performance of recycled PET is mainly studied

1 experimental part

1.1 main raw materials and equipment

pet bottle recycled material: the characteristic viscosity is greater than 0.6dl/g; Tackifying PET: self made, chemically tackifying with recycled PET bottles, with an intrinsic viscosity greater than 0.8dl/g; PBT: intrinsic viscosity 1.0dl/g, Changchun artificial resin factory Co., Ltd; Red phosphorus masterbatch: rpm650, Chenguang Chemical Research Institute; EVA: Korean oil chemical

twin screw extruder: te-35 type, Nanjing kemperon Keya company; Differential scanning calorimeter: Perkin Elmer DSC 7, American PE company

1.2 preparation of composite materials

pet bottle flakes, PBT, nucleating agent and crystallization accelerator are melt blended by twin-screw extruder and granulated to prepare pure resin materials. PET bottle chips, PBT, nucleating agent, flame retardant and toughening agent are melt blended by twin-screw extruder, and continuous glass fiber bundles are added from the second feeding port to obtain pet flame retardant reinforced composites

1.3 performance test

differential scanning calorimetry test: under the protection of N2, the sample is heated from 50 ℃ to 220 ℃ at 10 ℃/min, stayed for 5min, cooled to 50 ℃ at 10 ℃/min, and then heated to 220 ℃ in 256 batches of waste plastics

2 results and discussion

2.1 effect of nucleating agent on crystallization properties of pet

Table 1 shows the crystallization and melting data of tackifying pet; Among them, 4# samples are tackifying pet samples without nucleating agent, 15# and 16# are tackifying pet samples with different amounts of inorganic nucleating agent, and 17#, 18# and 19# are tackifying pet samples with different amounts of carboxylate nucleating agent. It can be seen from table 1 that both organic carboxylate nucleators and inorganic nucleators reduce the cold crystallization temperature TCC and increase the hot crystallization temperature TMC of pet. Compared with the 4# sample without nucleating agent, the organic carboxylate nucleating agent reduced the cold crystallization temperature of pet by about 7 ℃, and increased the hot crystallization temperature by about 11 ℃; The inorganic nucleating agent reduced the cold crystallization temperature of pet by about 4 ℃ and increased the hot crystallization temperature by 13 ℃. It shows that organic carboxylate nucleating agent has strong nucleation and crystallization ability in the cold crystallization process, and inorganic nucleating agent has better nucleation effect in the melt crystallization process

therefore, the organic carboxylate nucleating agent and inorganic nucleating agent were used as the nucleating agent of pet in this experiment. 20 # is a pet sample added with compound nucleating agent. Compared with 4 # sample, its nucleation temperature range is widened to 19 ℃ during heating and cooling

nucleating agent not only reduces the cold crystallization temperature of recycled PET, but also increases the hot crystallization temperature; Moreover, the melting temperature and crystallization heat of pet can be increased (the corresponding crystallinity is increased). 20 # samples not only have low cold crystallization temperature; Moreover, it has high thermal crystallization temperature, melting temperature and crystallization heat. When the specimen is close to destruction, the combination of organic carboxylate nucleating agent and inorganic nucleating agent has synergistic effect

Table 1 crystallization and melting data of tackifying pet

tab 1 data of crystallization and melting of viscosity increased pet

sample number

primary temperature rise

primary temperature drop

secondary temperature rise

TCC/℃

△ HC/J · g-1

TM/℃

△ hm/J · g-1

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