Ldpe Heterogeneous Photo-grafting Acrylic Acid And The Product Structure And Performance

In this thesis, a photografting system was studied mechanically with LDPE film as the matrix, AA as monomer and benzophenone(BP) as photoinitiator, The diffusion of BP into LDPE film, the photoreduction of BP under different condition were measured. The kinetics of the photografting process, and the co current crosslinking reaction, the heat degradation, the mechanic properties and surface characters of LDPE-g-AA were investigated.These work showed: the diffusion coefficient of BP from its acetone solution to the film, decreased with the increasing of the concentration, from 0.8 to 2.0*10'12m2 ?sec"1; The far UV( <300nm) plays an important part in the photoreduction of BP, ie, when it was filtered by a PET film, this process slow down apparently, and this tendency became more obvious when the oxygen was present; the photoreduction had little dependence on the temperature, and it resulted in the creation of benzpinakol and the crosslinking of LDPE film also, as well as the percent of gel depended on the radiating condition and the amount of BP in LDPE film.During two-step vapor phase photografting, the percent of graft (G) increased quickly at first, and then leveled off. While the far UV was filtered, G became lower at the beginning of the reaction than that while it was present, but about 5 minutes later, there was little difference. The raising temperature could increase the percent of graft remarkably. Because the content of monomer was restricted, the reaction time and G were small, the law of which was similar to that of the former part of vapor phase photografting.An enhanced crosslinking has been discovered during photografting, and the IR spectrum of the dissolved LDPE-g-AA implied that the gel contained most of the grafted chains, the present of far UV, the rise of temperature and content of BP could increase yield of gel apparently. After photografting AA, the tensile strength and break elongation of LDPE decreased but the modulus increased. The presence of far UV, theincreasing of content of BP and the elevate of temperature could make this trend more obvious. At low temperature, the degradation of LDPE-g-AA was more rapid than that of pure LDPE, and the present of oxygen had little influence on it. The activation energy was similar to that of PAA. At high temperature, its degradation became a bit slower. With the increasing of the content of BP the tendency became more obvious. The contract angle( )to water of LDPE surface declined with the increasing of graft yield and then leveled off. While the far UV was filtered by PET film, the surface modification became weak obviously. The suitable content of BP and the concentration of AA were also needed to get a good modification effect.After photografting, the AA grafted LDPE film could be dyed by cationic dyer, and its area and thickness increased too. These features were more obvious in vapor phase process than in liquid phase process in which the G was so small that those changes were nearly imperceptible.