PE-g-MAH与铝片粘接机理的研究

Study on Bonding Mechanism between Maleic Anhydride Grafted Polyethylene and Aluminium Sheet

本文采用双螺杆熔融接枝法,制备马来酸酐(MAH)接枝聚乙烯(PE-g-MAH)和马来酸酐/苯乙烯(St)接枝聚乙烯(PE-g-(MAH-St)),考察St用量对PE-g-(MAH-St)和铝片粘接强度的影响.FTIR测试表明,St的加入使羰基峰发生“红移”现象,PE-g-MAH,PE-g-(MAH-St=1:0.5),PE-g-(MAH-St=1:1)分别为1791cm^(-1)、1786 cm^(-1)和1782 cm^(-1),原因是MAH和St易生成电荷转移络合物(CTC),CTC使羰基双键减弱导致.同时,相比PE-g-MAH,PE-g-(MAH-St=1:1)接枝率最高且界面粘合功最大,而与铝片的粘接强度却显著下降,这主要是因为CTC使MAH环内电子离域成大π键,相应氧原子上的孤对电子呈现与大π键共轭的趋势,导致氧原子孤对电子与铝片“空轨道”配位能力减弱,导致粘接强度下降,因此证明PE-g-MAH与铝片间生成的配位键是粘接的主要机理。

In this paper,free-radical melt grafting of the maleic anhydride(MAH)onto polyethylene(PE-g-MAH)and second comonomer styrene(St)onto polyethylene(PE-g-(MAH-St))were studied using a corotating twin-screw extruders.The effects of St concentrations on bonding strength be tween PE-g-(MAH-St)and aluminium sheet were investigated.It was shown that there is a“red shift”phenomenon in the FTIR spectra,in which the position of carbonyl(C=O)stretching vibration peak in PE-g-MAH,PE-g-(MAH-St=1:0.5)and PE-g-(MAH-St=1:1)is 1791cm^(-1),1786cm^(-1)and 1782cm^(-1),respectively.This“red shift”phenomenon is caused by the charge transfer complex(CTC)carrying alternating MAH and St,which weakens the carbonyl double bond.Furthermore,compared to PE-g-MAH,PE-g-(MAH-St=1:1)has the biggest melt index,highest MAH grafted as well as the biggest work of adhesion calculated from surface free energy,but the lowest bonding strength.The decrease in bo nding strength largely results from the fact that the CTC structure causes the electrons in the MAH ring structure to delocalize into largeπbonds,then the lone pair electrons on the corresponding oxygen atoms show a trend of conjugation with the largeπbond,which leads to the weakening of the coor dination ability to"unoccupied orbital"of aluminum sheet,resulting in the decrease of bonding strength.There is good agreement between the“red shift”in FTIR spe ctra and decease of bonding strength.Therefore,experimental evidence demonstrates that the coordination bond between PE-g-MAH and aluminum sheet is the main bonding mechanism.