Preparation And Production Technology Of The Cu/LDPE/LLDPE Composite Films

The low density polyethylene(LDPE)150E was chosen to blend,extrude and blow into a series of films with the linear low density polyethylene(LLDPE)118W and 7042 respectively.Blown film production process was studied.The optimal formula of 40wt%LDPE 150E and 60wt%LLDPE 118W was obtained by capillary rheometer and mechanical tests.The extrudate of the formula had smooth appearance without ’shark skin’.The film produced from this formula had good mechanical properties.The copper powders named as Cu-a,Cu-b and Cu-c with different shapes and sizes were added into PE matrix to blow into the composite films using a single layer extrusion blowing machine.The blown film production process was also studied.The prepared composite films were named PE-Cu-a,PE-Cu-b and PE-Cu-c.By mechanical,ageing,water vapor and oxygen permeance tests et al,it was founded that the tensile strength of the composite film was higher than 25MPa and the elongation at break was more than 800%.The mechanical properties of composite films were kept well after two weeks’ aging test.The thermal conductivity of composite films was improved and the thermal conductivity coefficient of PE-Cu-b was 1.426 W/(m.K),which was almost five times more than that of pure PE film.The volume resistivity of PE-Cu-b was 1.6×1011 Ω·cm and was decreased by five orders of magnitude compared with pure PE film.The improvement in thermal conductivity and reduction of volume resistivity were due to formation of conductive pathways with the good dispersion of copper powders.The water vapor and oxygen permeance of composite films were also reduced.The water vapor permeance of PE-Cu-b was 2.6 g/m3,which showed that the ability of blocking water vapor was increased by 35%compared with pure PE film.Five periods of damp and heat test passed for the steel and copper samples encapsulated with the composite film.The three layer co-extrusion blowing machine was used to produce pure PE film and Cu composite film,named as PE-T and PE-Cu-T,to improve the performance of the films further.The best production conditions were obtained through the investigation of the production process.The films made by three layer co-extrusion blowing machine had better performances compared with that by the single layer extrusion blowing process.The thermal conductivity coefficient of PE-Cu-T was increased 32.9%and the volume resistivity was decreased one order compared to the single films.The oxygen permeance and water vapor of PE-Cu-T-were 780 cm3/m2 and 2.5 g/m3 respectively,which were reduced by 25.5%and 3.9%compared with the single films.Six periods of damp and heat test passed for the steel and copper samples encapsulated with the composite film.