Report a data issue, formatting problem, or request follow-up. Our team responds within one business day.
Be the first to review this report.
Stretch film packaging comprises thin extensible polymer films that secure individual products, bundles, rolls, trays, and palletized loads through tensile deformation, elastic recovery, surface cling, and overlapping wrap geometry. Mechanical elongation stores elastic energy within the film. Subsequent molecular recovery generates circumferential containment force around the load, while adhesion between overlapping layers maintains package continuity. Load restraint derives from the retained tensile stress of the film, the number and distribution of effective layers, wrap angle, contact friction, and the mechanical response of the packaged goods. Industrial stretch film is produced predominantly from linear low density polyethylene containing butene, hexene, or octene comonomers. Short chain branching reduces crystal packing efficiency and forms a semicrystalline structure combining extensibility, toughness, impact resistance, and recoverable deformation. Metallocene linear low density polyethylene and polyethylene plastomers provide narrower molecular weight and comonomer distributions, permitting thinner gauges, more uniform deformation, higher puncture resistance, and controlled stress retention. Formulations may also contain low density polyethylene, very low density polyethylene, ethylene vinyl acetate, polyisobutylene cling agents, polymeric tackifiers, slip agents, antiblock agents, processing aids, pigments, ultraviolet stabilizers, antistatic additives, and recycled polyethylene. Typical polymer density lies between approximately 0.90 and 0.94 g/cm³. Modern stretch films commonly use three, five, seven, or nine coextruded layers. Microlayer structures may contain several dozen discrete layers. The internal core carries most of the tensile load and governs elongation, toughness, puncture resistance, elastic recovery, and stress relaxation. The cling surface contains migratory or permanent tack components that produce adhesion between successive wraps. The external surface controls slip, pallet contact, abrasion, blocking, unwind force, and surface friction. Layer thickness ratios, resin compatibility, crystallinity, molecular orientation, interfacial bonding, and cooling history determine the mechanical balance between stretchability, stiffness, toughness, recovery, and retained force. Cast stretch film is produced by melting and homogenizing polymer streams in separate extruders, combining them through a feedblock or multilayer die, discharging the melt through a flat die, and rapidly cooling the web on a chilled roll. Typical polyethylene melt temperatures are approximately 180 to 250 °C. Rapid quenching limits crystal growth and produces high clarity, uniform thickness, stable roll geometry, controlled cling distribution, and low unwind noise. Blown stretch film is extruded through an annular die into a tubular bubble, expanded by internal air pressure, drawn longitudinally, cooled, collapsed, slit, and wound. The combined blow up ratio and haul off ratio create biaxial molecular orientation, producing a different balance of puncture resistance, tear propagation, toughness, optical properties, and elastic recovery. Die geometry, melt temperature, output rate, cooling rate, draw ratio, layer distribution, edge trim, web tension, and winding pressure determine film uniformity and roll integrity. Commercial pallet stretch films commonly have nominal thicknesses of approximately 8 to 35 µm. Thin gauge high performance products may fall below this range, while heavy duty and specialty films may exceed it. A nominal width near 500 mm is common for pallet wrapping. Narrow bundling films, hand rolls, wide machine webs, jumbo rolls, and converted prestretched films use different dimensions. Ultimate elongation commonly ranges from approximately 300 to 700 percent, with tensile strength frequently falling between approximately 20 and 60 MPa according to formulation, thickness, test speed, and orientation. Applied elongation generally ranges from approximately 50 to 150 percent for hand film and approximately 150 to 300 percent for machine film. Certain high performance machine grades operate above 300 percent. Prestretched film is mechanically drawn before rewinding, partially relaxed, and wound at a reduced effective gauge while retaining recoverable molecular strain. Stretch film performance is defined by tensile strength in the machine and transverse directions, elongation at break, yield behavior, elastic modulus, puncture energy, tear initiation, tear propagation, dart impact resistance, cling force, coefficient of friction, haze, gloss, unwind force, permanent deformation, elastic recovery, stress relaxation, and retained force. Initial wrap force determines the immediate tensile load applied to the package. Polymer recovery maintains containment after application. Viscoelastic stress relaxation progressively reduces retained force with time, temperature, and sustained strain. Film stiffness affects load compression and corner pressure. Toughness and puncture resistance control survival around sharp edges and irregular surfaces. Surface friction influences interaction between the film, the load, adjacent pallets, and handling equipment. Manufacturing and service failures include gauge bands, gels, contamination, die lines, interlayer instability, weak edges, wrinkles, blocking, irregular cling, excessive slip, telescoping, core deformation, roll edge damage, nonuniform elongation, necking, puncture initiation, tear propagation, web rupture, creep, permanent set, and loss of containment through stress relaxation. The resulting package is a coupled mechanical structure in which polymer formulation, layer architecture, film geometry, molecular orientation, residual stress, surface properties, load shape, edge condition, and environmental temperature collectively determine stability during handling, storage, vibration, acceleration, impact, and transport.
You may also be interested in
