Study Of Dimer-Acid Based Polyamide/Polypropylene Composite Hot-Melt Adhesive

Adhesive is a material that can be adhered to the surface of an object and the adhesion force is generated through the bonding process,so the same or different materials can be bonded together.As one of the main adhesives,hot melt adhesives have strong adhesion,good weather resistance and can be used without organic solvents.Therefore,hot melt adhesives are more environmental friendly than traditional liquid adhesives.The main components of polyolefin hot melt adhesives are polypropylene(PP)and polyethylene(PE),which are usually used to bond non-polar substrates such as polyethylene and polypropylene.Polyolefin hot melt adhesives are widely used in industries such as packaging and automotive,and are one of the most popular hot melt adhesives.However,polypropylene(PP)is a non-polar polymer,and the adhesion strength is very week when bonded to polar substrates,so the application scenarios of polypropylene hot melt adhesive are greatly limited.What’ s more,with the shortage of petrochemical resources all over the world,it is of great significance to use renewable resources to broaden the application scope of petrochemical products,which can increase the added value of products and reduce the consumption of fossil energy.In order to improve the polarity of polypropylene,the main part of the hot melt adhesive,is first grafted with maleic anhydride.The effect of the proportion of the initiator dicumyl peroxide and the monomer maleic anhydride on the grafting rate of maleic anhydride on polypropylene(PP-g-MAH)is studied by melt grafting method.The results of infrared spectroscopy(FTIR)and titration method show that the highest grafting rate can be obtained when the initiator content is 0.3 wt%and the maleic anhydride content is 4 wt%.On the basis of the result,we research the influence of styrene as a second grafting monomer on the grafting rate of maleic anhydride,and the results show that although the addition of styrene increases the grafting rate of maleic anhydride on polypropylene,the mechanical properties decrease significantly.Then we use the blending method to blend the grafted polypropylene(PP-g-MAH)with the dimer acid polyamide resin,which is prepared from renewable resources and is also one of the usually used hot melt adhesives in electronics industry.By differential scanning calorimetry(DSC),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)tests,we find that the compatibility of the two was good when the content of PP-g-MAH is 80 wt%-90 wt%.The reason for the rapid change in mechanical properties between the different proportions of PP-g-MAH/DAPA composite hot melt adhesives is explained by percolation theory.The results of the tensile shear strength test of the bonded copper foil by different proportions of PP-gMAH/DAPA composite hot melt adhesives show that the tensile shear strength reaches up to 4.05 MPa when the content of PP-g-MAH is 80 wt%and the content of dimer acid polyamide resin is 20 wt%,which is nearly 160%higher than the 1.56 MPa of PPg-MAH.The dielectric constant and dielectric loss tests also show that composite hot melt adhesives have good insulation properties and are expected to be used in the electronics industry.