Study On Aging Discipline And Life Time Prediction Of TPEE

The weather ageing and experimental aging have been taken to the thermoplasticpolyester elastomer which is formed by polybutylene terephthalate（PBT） andpolytetrahydrofuran(PTMG). The tensile character and situation of surface crack arechoosen to do the study of aging order. The mathematical model has been built toanalyze the image of cracks.A direct analyzing method of TPEE aging based on thecrack situation is proposed. And by the comparing of wearthing and accelerated aging,the aging rules of different TPPE in different environment are studied. The specificresults are as follows:1、In the same wearth condition, the mechanical properties of TPEE whose shorehardness is40and63both decreased to50%of the original sample. While the othersample (D55) changes slower. After2months, the properties have decreased to50%of the original sample. For this reason, the TPEE sample whose hardness is55isrecommened to take use of in the area accompany with higy temperature andmoisture.2、Although after artificial controlling, the environmental condition is much moreharmful to TPEE sample, the truth is sample aging faster in natural environment. TakeD40sample as example，in natural circumstance，both mechanical properties andsurfacecrack situation have changed largely. While in the UV testing machine whichassembled with310nm UV lights,the changing is slower. Comparatively, the NaOHsolution (PH9) is more harmful to TPEE sample. In the solution, after30days, theelongation at break decreased to less than50%of the original sample. And the tensilestrength maintain above60%after2months. This is different with the aging behaviorin natural condition. In nature, sunlight motivates the appearance of crack.3、In the same aging circumstance, samples with different hardness expressdifferent aging behavior. In the condition of310nm UV light mechine, there arecracks beening observed on the surface of TPEE samples(D40), while no crack hasbeen observed on the surface of TPEE whose hardness is63. On the contrary, themechanical properties chang fast. In the NaOH solution of90℃，the glossiness ofsample surface decrease quickly, and the bigger hardness leads to easier changing ofglossiness. Which means the appearance of TPEE with more soft segments is moreeasily to be affected by outside environment, and the image recognition is moreeffective.4、The mechanism of TPEE varyfing according to different circumstances. Underthe UV light, the degradation of soft segment happened which leads to cracksappearance and decrease of mechanical properties. In hydrosis environment, estergroup of hard and soft segments are both destroyed and lead to decrease of crystallineand mechanical properties. Aging behavior in natural environment is much morecomplicated, the aging mechanism on different sample side is not identical. Softsegments on the positive side is affected by sunlight severely which leads to morecracks; while on the other side, both hard and soft segments are damaged by optical and thermal radiation, water, dust, pitch and so on.5、The cracks images on TPEE surface(D40) are analyzed by mean filter andsupervised crack detection. The resules show that when tensile strength decreased to73%of the original samples, the cracks’ area take11.2%of the whole image area.This can be used to determine the aging terminal point of TPEE sample (D40).