Laser Transmission Welding Research And Numerical Simulation Of Grafted Polyethylene And Nylon 66

Laser transmission welding has been widely used in the welding of polymers. Nylon 66 and polyethylene, common plastics, are widely used in the automotive and other industries. However, because the polarity difference between nylon 66 and polyethene is too large, they cannot be welded by the laser directly. Thus, polyethylene has been modified to improve the laser transmission welding performance between polyethylene and nylon 66. Then, the laser transmission weldability mechanism of the graft modified polyethylene and nylon 66 has been researched. Also, the welding process and numerical simulation of temperature field of the graft modified polyethylene and nylon 66 have been studied.Firstly, two ways of the graft modified polyethylene that the strong polar and reactive maleic-anhydride(MAH) and glycidyl- methacrylate(GMA) are grafted polyethylene respectively are introduced. The mechanical and thermal performances of the graft modified polyethylene was tested which show that the grafting modification has few influences on them. And the optical properties of the grafting modification were measured and it proves that the modification is good for the laser transmission welding between nylon 66 and polyethylene.Then, the laser transmission weldability mechanism of the graft modified polyethylene and nylon 66 has been researched. The micro morphology of the weld region between them displays that the affinity and the compatibility between polyethylene and PA66 are greatly improved. Thus, some locking holes, being similar to the rivet lock, are formed, which is one of the reasons why the welding performance is so high. And the welding strength of the MAH modified polyethylene and PA66 is higher than the GMA modified ones. To a certain extent, the bubbles in the welding region are good to improve the welding strength. But the too large bubbles caused by the large laser power are bad for the welding. Under the tensile force, the failure of the welding between the GMA modified polyethylene and PA66 is the combination of the plastic fracture and the brittle fracture while the failure of the welding between the MAH modified polyethylene and PA66 is the plastic fracture. Through the measurement of contact angle, it was found that because the modification inproves the polarity of polyethylene, the polarity difference between nylon 66 and polyethylene becomes small and the compatibility between them becomes strong, which are benifical to the diffusion of them in the hot melt condition. The X-ray photoelectron spectroscopy proves that PA66 may react with the MAH and GMA on the side chain of the graft modified polyethylene under the heating effect of laser, which is another reason for the high welding performance.Subsequently, the effect of the laser transmission welding process parameters on the welding performance between them has been studied. Then, the experimental welding strength-line energy plot of the graft modified polyethylene and nylon 66 has been researched, which shows that the welding strength between the MAH modified polyethylene and nylon 66 is higher, and the experimental welding strength- line energy plot of the MAH modified polyethylene and nylon 66 is at the right because of the smaller transmissivity. Through response surface method, the mathematical models of the laser transmission welding quality(welding width and welding strength) between the MAH modified polyethylene and nylon 66 have been established. The interactive effects of the welding process parameters on the welding quality have also been explored. Then, the models were verified and then used to optimize the welding process. At last, the optimal process parameters were given to guide the industrial production.At last, the finite element software was used to simulate the temperature field in the laser transmission welding of the MAH modified polyethylene and nylon 66. The temperature field distribution under different process parameters has been studied. The effect of the laser power and scanning speed on the maximum temperature and the welding width has been researched. The simulated welding width was compared with the experimental welding width, proving that the model is reliable.