Study Of LLDPE/POE/CaCO₃ Waterproof And Moisture-permeable Microporous Film And Its Multilaminate Sheeting

A waterproof and moisture permeable microporous film was prepared from liner low density polyethylene(LLDPE)/ethylene-octene copolymer(POE)/ CaCO₃ system via blend granulation, tape extrusion, driveling ,and uniaxial stretch. The rheological performance and its influencing factors of the system were investigated. Effects of operating conditions, such as stretch ratio, system components on the micropore morphology, waterproof, and moisture permeability of the microporous film were studied experimentally. The structure morphology, micropore size and distribution, and porosity of the microporous film were measured. The properties of waterproof and moisture permeability of the microporous film were simulated. On the basis of microporous film, preparation of a 3-laminate sheeting of PP nonwoven fabric/microporous film/PP nonwoven fabric was carried out using the point hot -pressed composition method at an industrial installation. Effects of technological conditions of hot-pressed composition process on the composition strength, the watertightnees, and moisture permeability were investigated. The preparation of a miacroporous film of LLDPE/POE/ CaCO₃/bamboo charcoal activated carbon was studied preliminarily.The study of the rheological performance of LLDPE/POE/ CaCO₃ system shows that the system is a pseudoplastic fluid. The results indicate that the less the CaCO₃ content, the more pseudoplastic, and that the pseudo-plasticity is more strong while the POE content is 25% in total amount of resin. The results show also that in proper range of temperature and shear rate the apparent viscosity decreases and the mobility is improved due to using of POE.The study of effects of the stretch ratio and technological conditions on the morphology, the watertightness, and the moisture permeability of the microporous film of LLDPE/POE/ CaCO₃ shows that after stretching of the CaCO₃-filled LLDPE/POE film the interface of CaCO₃ and resin occurs debonding to form microporous cracks, and that the pore size and porosity of the microporous film increase with increase of the stretch ratio. The results show also that the porosity of the microporous film is the biggest while the amount of is 100 shares(correspond to 100 shares of resin) , which is beneficial to the moisture permeability of the microporous film.The simulation of the moisture permeability of LLDPE/POE/ CaCO₃ microporous film indicates that the moisture permeability of the microporous film belongs to fickian diffusion. The simulation results show also that the main factor of the increase of moisture permeability is the pore number per unit area of the film, and that the moisture permeability can not be increased by increasing the pore size.The study of the multilaminate sheeting with waterproof and moisture permeability composited via point hot-pressed method indicates that effects of composition temperature, pressure, and POE content on the bonding strength, watertightnees, and moisture permeability are significant. The proper temperature is 85～95℃. The bonding strength between layers is poor while the temperature of roller is too low. At high temperature of roller, the microporous film will be injured partially by the protrusile structures at the surface of the hot roller in hot composition process, which makes the waterproof poor. The proper pressure of hot roller is about 15MPa. Lower pressure of hot roller makes the bonding strength poor. Higher pressure of hot roller makes the microporous film injured, which can lead to poor waterproof property. The proper content of POE is 25% in total amount of resin. Lower content of POE(< 20%) makes the bonding strength of laminate sheeting unsatisfactory although the temperature and pressure of hot roller are proper. Higher content of POE(30%) makes the waterproof property poor due to the microporous film's injury caused by the hot roller.The preliminary study of microporous film of LLDPE/POE/ CaCO₃/bamboo charcoal activated carbon indicates that the waterproof and moisture permeable performance has little change after adding the bamboo charcoal activated carbon. The introduction of the bamboo charcoal activated carbon supplies a basis for preparing a waterproof and breathable film with adsorption function.