Method for stake-fastening an accessory (4) into a plastic fuel tank, whereby: the accessory (4) is equipped with at least one orifice (5) which passes right through the accessory (4); at least some of the plastic of which the wall of the tank (1) is made is melted; and some of the molten plastic is forced through the orifice (5) of the accessory without becoming detached from the remainder of the molten plastic; the protruding molten plastic is given an appropriate shape (8) to obtain a self-formed plastic rivet, and is left to solidify;
the size and shape of the orifice (5) and/or of the solidified plastic (8) being such that the accessory (4) is mechanically fastened to the tank by at least some of the solidified plastic (8), the stake-fastening of the accessory (4) occurring at the time of manufacture of the tank (1) through the moulding of a split or at least two-part parison.

Aspects of the disclosure relate to manufacturing a balloon envelope for use in a stratospheric balloon system. For instance, a stream of polyethylene mixture is extruded through an extruder in order to orient molecules of polymer chains of polyethylene and to provide an oriented film. The oriented film is passed through an electron beam and thereby crosslinking the polymer chains to provide a cross-linked film. The cross-linked film is heat sealed to form the balloon envelope.

Described is an insect net strip produced from a wide insect net which has been cut in a warp direction (xnet) by means of a one-step ultrasonic cutting and welding process. The insect net strip includes warp yarns and weft yarns extending substantially perpendicular to each other and at least 90% of the warp and weft yarns are monofilament yarns made of a thermoplastic material. After cutting and welding process the insect net strip has a first and a second edge extending parallel to said warp yarns each including a deformation zone being constituted by consolidated thermoplastic material deriving at least from said weft yarns. The deformation zone has a width (wdz) in the transverse direction (ystrip) of between 0.5-35 times the weft yarn diameter (we). At least 90% of gaps between adjacent weft yarns in the deformation zone are closed by consolidated thermoplastic material at least from the weft yarns which has been melted together to form a continuous or substantially continuous reinforced band-shaped edge portion of said insect net strip. The insect net strip is suitable for use in accordion-style constructions in greenhouse ventilation openings. A method for producing the insect strips is also described.

Aspects of the disclosure relate to manufacturing a balloon envelope for use in a stratospheric balloon system using an improved double-bubble blown-film extrusion process with water quenching and electron beam processing. A stream of polyethylene mixture is extruded through an extruder to orient molecules of polymer chains and provide an oriented film. The oriented film is passed through an electron beam, crosslinking the polymer chains to produce a cross-linked film with enhanced mechanical properties. The cross-linked film is heat sealed to form the balloon envelope comprising multiple gores. The resulting balloon envelope exhibits superior characteristics including crystallinity greater than 50%, strength to weight ratio greater than 1 MPa/(dtg/cm.sup.3), thickness less than 1.5 mil, thermal emissivity less than 0.03 at 193K, and optical clarity greater than 95%. The manufacturing process may include water quenching to enhance optical clarity and dual electron beam treatment for uniform crosslinking throughout the film thickness.