Adhesion of polypropylene and polyethylene after plasma processing

Polypropylene(PP) and polyethylene(PE) are treated with radio frequency(RF) glow discharge plasma and dielectric barrier discharge(DBD) plasma. Then the shear strength of the mixing adhesion of PP and PE using polyurethane as adhesive is tested. Results show that the shear strength highly increases when the DBD plasma is applied with 200 W power. The maxium shear strength after DBD plasma processing is 1.58 MPa(20 s) which is 14.36 times that of untreated samples. However, the PP and PE are burned in 10 s when the power is 300 W, and there is no change when the power is 100 W. The effect of air RF discharge with maximum shear strength of 1.60 MPa(100 W, 3 min) is nearly the same as that of N2 RF discharge with maximum shear strength of 1.57 MPa (200 W, 3 min). Through scanning electron microscope analysis, the surfaces of samples treated with plasma are rough as a result of appearance of bubbles on the surfaces whereas the surfaces of untreated samples are smooth. Therefore, the shear strength of the mixing adhesion of PP and PE increases greatly aftertreatment with DBD plasma and RF glow discharge plasma.