Performance of plastic film. Plastic film is the base material of composite geomembrane. The root of its performance is mainly determined by the nature, type, specification, processing technology and processing method of the processing resin, and is also related to parameters such as the flow performance and mechanical properties of the molten viscous flow state. At present, one of the most widely used base material raw materials in engineering materials is the blown film used in thermoplastic polyethylene-based (PE) plastic film materials, which can be co-melted, mixed and extruded from linear low-density polyethylene film (LDPE) and linear low-density polyethylene gel (LDPE), and then respectively compounded by infrared and radiation heat treatment. Among them, linear low-density cross-linked polyethylene glue (LDPE) glue is a type of monomer polymerized by copolymerization reaction of ethylene monomer and poly A-poly-diene monomer. Because the average molecular weight distribution of the monomer is relatively narrower than that of polyethylene monomer (LDPE) glue, and the average molecular mass is relatively larger, the regularity and uniformity in its single macromolecular chain structure is between high-density polyethylene glue (LDPE) glue and ultra-high-density cross-linked polyethylene gel (HDPE) gel, and is a short branched chain structure. Therefore, it usually has a higher tensile yield strength value, maximum elongation value, good tensile toughness, environmental stress cracking resistance, and impact resistance and impermeability better than low-density polyethylene (LDPE). The quality of the mechanical properties of the plastic film directly affects the mechanical properties of the entire composite. In the plateau region of the tensile curve, the tensile strength of the plastic film is large, indicating that its mechanical properties are good. Therefore, improving the strength of the plastic film has a great contribution to improving the mechanical properties of the entire composite. The strength of the plastic film is related to the orientation degree of the molecular chain. In engineering, in order to improve the strength of the plastic film, the method of improving the orientation degree of the molecular chain to make the orientation straight is usually adopted. For blown films, the strength can be improved by improving the longitudinal and transverse strength ratio, which is achieved by adjusting the transverse blow-up ratio and longitudinal stretch ratio during processing.
Performance of base fabric. The base fabric material is one of the two main structural materials used to prepare composite geomembranes. Its own main types and structural properties will not only indirectly affect the tensile and shear properties, waterproof and anti-seepage properties of the prepared composite geomembrane system, but also directly affect the structure of the membrane-base composite transition zone of the composite geomembrane. Improving the strength of the base fabric can significantly improve the mechanical performance indicators of the composite geomembrane. The surface flatness of the base fabric surface material is the most basic, direct and important factor that directly affects the quality of its processing performance. The more uniform and flat the base fabric surface material is, the fewer the fine fiber clusters, cluster points and needle trace stripes carried on the needle surface. The fibers are evenly attached to each other and the color depth when the fibers are squeezed into the conjunctival tissue is the most uniform. There are generally no obvious structural weak links in the entire fiber composite material, and the hydrostatic pressure resistance value is high. The thicker the nylon fiber thickness covered on the surface of the base fabric, the deeper the impregnation degree squeezed into the membrane body, and the easier the product is to seep water. During the hot-pressing composite process, when the base fabric is relatively thick and the structure is relatively fluffy, the base fabric has no obvious needle trace stripes and fiber clusters caused by needling, the fiber attached hairiness is relatively less, and the fiber aggregate (fabric) is first compressed to produce compression deformation, making the aggregate tight and sturdy. Therefore, the time required for the compressive stress to be transmitted to the membrane body is prolonged, the number of fibers on the surface layer of the base fabric bonded to the membrane body is reduced, the bonding action time becomes shorter and the bonding area decreases, resulting in poor bonding effect. Conversely, when there are many attached hairiness and many fibers on the fabric surface, during hot-pressing composite, the number of fibers squeezed into the plastic film is large, the bonding area of the bonding points also increases, and the bonding effect is improved. In addition, some base fabrics are ironed and polished, without fibers with sharp protruding head ends, the surface is flat and smooth, and the fibers are not easy to embed into the membrane material under pressure during thermal composite, reducing the new structural defects brought to the membrane material. Therefore, in construction production, the base fabric with flat surface and tight structure after hot-rolling and polishing treatment is more used to composite with plastic film material to improve the anti-seepage performance of the composite geomembrane.
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