Attachment System for Reinforcing Glass Yarns
The invention relates to a method of connecting the ends of at least two glass yarns, in which the ends are impregnated with a material comprising a thermoplastic or thermosetting material or with a mixture of a thermoplastic material and a thermosetting material in an overlapping area which is calibrated using calibration means such as a mould/counter-mould assembly. According to the invention, the material is introduced into the calibration means either in the molten form or in the solid form. The overlapping zone of said material and the ends of the yarns is subsequently subjected to means for the at least partial and preferably-complete fusion of the material. The invention also relates to the continuous filament yam that can be obtained using said method and to the use of one such yam in a method in which it is used under strong tensile strain and/or in which it is passed through a calibrated nozzle.
1 . A method of joining the ends of at least two glass strands together, in which said ends are impregnated with a material comprising a thermoplastic or a thermoset, or with a blend of a thermoplastic and a thermoset, in an overlap region calibrated by calibrating means, said material being introduced into the calibrating means:
in molten form;
or in solid form, said material and the ends of the strands then being exposed, in the overlap region, to means for at least partially, and preferably completely, melting the material.
2 . The joining method as claimed in claim 1 , in which the length of the overlap region is between 1 and 5 cm.
3 . The joining method as claimed in claim 1 , in which the material is deposited over a length greater than the overlap region of the strands.
4 . The joining method as claimed in claim 1 , in which a coupler, consisting of or comprising a thermoplastic or a thermoset, or a blend of a thermoplastic and a thermoset, which is sensitive to ultrasound, is applied in the overlap region to the ends of the strands to be joined and then said coupler and the ends of the strands are subjected in the overlap region to mechanical vibrations within the ultrasound range, the frequency, amplitude and duration of which allow the coupler and the join between the strands to be at least partially, and preferably completely, melted.
5 . The joining method as claimed in claim 4 , in which the frequency of the vibrations is between 20 and 100 kHz, preferably between 20 and 40 kHz.
6 . The joining method as claimed in claim 4 , in which the vibration amplitude is between 0.1 and 1 mm, preferably between 0.1 and 0.5 mm.
7 . The joining method as claimed in claim 4 , in which the duration is between 1 and 3 seconds, preferably around 1 second.
8 . The joining method as claimed in claim 4 , in which the mechanical vibrations are obtained by employing a device comprising a sonotrode set in vibration by a piezoelectric transducer.
9 . The joining method as claimed in claim 8 , in which the device includes a calibrated, cavity defining and surrounding the overlap region in order to check the shape and regularity after employing the sonotrode.
10 . The joining method as claimed in claim 1 , in which the thermoplastic is selected according to the subsequent conversion process carried out on the joined strand or process for manufacturing a composite from the joined strand, especially according to the compatibility of said thermoplastic with the matrices used in the conversion or manufacturing processes.
11 . The joining method as claimed in claim 1 , in which the thermoplastic comprises a matrix based on a polymer chosen from polypropylenes (PP), polyamides (PA), polyethylene terephthalates (PET), polybutylene terephthalates (PBT), and acrylonitrile-butadiene-styrene copolymers (ABS).
12 . A continuous strand able to be obtained by the method as claimed in claim 1 , comprising an overlap region in which the ends of two base strands are joined by means of a thermoplastic, thermoset or a blend of a thermoplastic and a thermoset present between the constituent filaments of said strands.
13 . The method of using the continuous strand as claimed in claim 12 in a process in which said strand is subjected to a high tensile force and/or passes through a calibrated die, such as processes of the thermoplastic pultrusion type for obtaining long-fiber granulates, or direct, injection molding or compression molding, long-fiber processes resulting in the direct production of a part made of a composite, or processes for manufacturing textile surfaces, such as knitting and weaving, or processes for manufacturing chopped-strand or continuous-strand mats.