Modification Of Polyethylene And Applied In The Cable Sheath

At present, high-density polyethylene (HDPE) is used generally the bridge jacket, but its durability is not long .So the following aspects have been studied in the this article.UHMWPE with excellent weatherability and UV-resistance was employed to improve the anti-ultraviolet property of HDPE. As the long time of aging test under natural conditions, a self-made UV aging chamber of 310nm in wave length, high-power (3KW), high radialization and irradiation intensity (89w/m~2) was used to accelerate the aging test. Artificial accelerated aging of 300h approximately equivalents to more than 100 years under natural conditions. The results showed that the elongation at break of UHMWPE and HDPE blend (weight ratio: UHMWPE: HDPE=1:1) still remained 80% compared with that of pristine HDPE after UV irradiated for 7h, which excelled the Japanese resin, but its processing performance is poor. Although the UV-resistance of UHMWPE and Bimodal polyethylene (BPE) blend (weight ratio: UHMWPE: BPE =3:7) was slightly poorer than that of UHMWPE and HDPE blend (weight ratio: UHMWPE: HDPE=1:1), its UV-resistance was improved compared with the pristine BPE.Samples of different irradiation time were analyzed by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), the results suggested that the characteristic absorption peek of C=O in aging layer and the cracks in the surface were caused by the break and partial oxidation of polyethylene main chains. Crystallinity analysis showed random changes, which may due to the complicated physical - chemical reactions under high-intensity UV irradiation.To improve the anti-aging properties of the modified samples further, the influences of different carbon blacks and their amounts on UV-resistance were investigated based on the previous matrix material with fixed amounts antioxidant and anti-UV dosage. The results showed that the material with carbon black content of 2.5phr and additive content of no more than 0.5phr had the best UV-resistance.By comparing the tests, it is found that the UV-resistances of both the matrix and black jacket material were prior to Japanese resin and Japanese black jacket material. Therefore, UHMWPE markedly improves the UV-resistance of HDPE, which could meet the requirements of the bridge sheath.