Preparation, Blending Modification Of PETG, TPU Based Invisible Orthodontic Materials

The rejection attitude of patients to orthodontic treatment is changed by the unique advantages of the bracketless invisible aligner. Since 1998 more than a million patients has got a good treatment effect by invisible appliance. However, the orthodontic materials domestic patients used all need to be imported from abroad. And there is no standard for the materials which is suitable for the preparation of invisible aligner.First, the imported materials used for the preparation of invisible aligner were analyzed, and the performance standard of materials applied to the preparation of invisible aligner was formulated. In this paper, polyurethane(TPU), and amorphous copolyester polyethylene terephthalate glycol(PETG) were chosen as the matrix materials. TPU was modified by adding AS. And PETG was modified by adding PC and TPU. By blending modification, the materials were developed to meet the orthodontic standard and were using for preparing invisible aligner.The results are as follows:(1) The performance standards of materials which are suitable for the preparation of the invisible aligner were formulated, by analyzing transparent properties, saliva absorption properties, mechanical properties and other properties of the imported thermoplastic materials.(2) The compatibility of TPU and AS is poor; the mechanical property of the TPU/AS system is reduced with the addition of AS; and the haze is large. The comprehensive performance of the blends isn’t meeting the orthodontic standard.(3) The yield stress of PETG was improved with the addition of the PC, and thermal stability and saliva absorption properties were ameliorated, meanwhile, without affecting the transparency properties. When the component of PC is 40, the yield stress of blends is 54.7MPa, which is increased by 15.6% than the pure PETG, the light transmittance is 88.2%, the haze is 3.1%, the saliva absorption is 5.871mg/g, the elongation at break is 145%, which is decreased by 28.8% than the pure PETG(4) With the content of PC being 40%, PETG was modified by the different mass ratio of PC/TPU complex. The study found that when the content of TPU is 15, the comprehensive performance of the system is most excellent, the yield stress is 52.7MPa, the elongation at break is 159%, the light transmittance of blends is 87.9%, the haze is 3.3%, the saliva absorption is 6.868mg/g. The blends could be used for the preparation of invisible aligner.