Every Fiber Counts
The First Long Glass Fiber PVC Composite
Until recently, the use of glass fibres was restricted to products made by traditional PVC processes (extrusion, injection moulding) or to products made by pultrusion. In the first case, the fibres are cut during processing and resulting properties are limited. In the second case, the continuous fibres give very high properties in one direction but this technique is not really adapted to viscous.
PVC. The new developed process by SolVin and the French company Fibroline uses long glass fibres (50 to 100 mm long) without any shearing step like conventional granulation or extrusion. The main advantage is the fibre length remaining unchanged, resulting in amazing properties for the products called "FibroVin".
The patented Fibroline Process is a dry process allowing impregnation of fibrous structures with powders thanks to an alternating electrical field. The impregnation phenomenon takes place between the electrodes with the help of a plasma.
The fibres are placed on a rigid PVC film set on a conveyor belt, then the powder is scattered on the surface. A second rigid PVC film recovers the product to form a sort of "sandwich". This material is thus entering between two plane electrodes connected to an alternating high tension generator. The sandwich is then compressed into a flat calender at high temperature and pressure to make a continuous sheet. The gelation of the PVC dry blend is obtained by compression only. SolVin has developed a special recipe able to gelate without shearing.
The sheets produced on the Fibroline line in Lyon are 0.8 or 1.6 mm thick and 90 cm width having a weight of 1 or 2kg/m². The material contains 40 w/w % of glass fibres and 60 w/w % of formulated PVC (including films). The glass fibres are randomly distributed in the plane so the properties are completely isotropic.
Some mechanical properties have been measured directly on the plates and for HDT, on hot pressed plates to have a thickness of 4mm. Several HDT methods (1.8 MPa or 0.45 MPa; edgewise or flatwise) are possible. However, in the flatwise position, a sliding occurs between the layers of FibroVin. The edgewise position avoids this problem. The more logical method is thus to apply a load of 1.8MPa edgewise.
The highest tensile modulus and tensile strength have been obtained with 100mm fibres length. The thickness of the plates has also an influence on the tensile properties. The HDT is around 25°C higher than for unfilled PVC.
The fire resistance is one of the advantages of PVC. The addition of long glass fibres will even improve this effect. Sandwich panels made of Nidacell honeycomb PVC structure covered by PVC layers or FibroVin layers have been tested in the cone calorimeter (ISO 5660). The results show that in spite of higher speed of heat and smoke releases, the FibroVin covered sample leads to significantly much lower total heat and smoke quantities. The presence of glass fibres prevents from heat and smoke release by creating a kind of "char".
Other properties clearly confirm the interest of this material. It is perfectly adapted to thermoforming. It can be glued or welded. The transparency of Fibrovin enables the laser welding on a PVC base like honeycomb structure Nidacell. It can be UV resistant to be used outdoor. And last but not least, it is recyclable after grinding and possibly re-used in a traditional extrusion process.
Figure 3 shows some lab samples made by thermoforming, gluing, bending, in combination or not with Nidacell honeycomb.
The Expected Markets
The FibroVin product can be used in various applications mainly in building as door panels, ceiling panels and partition walls. It can be used in transportation and marine applications, possibly in combination with Nidacell, owing to its high rigidity/weight ratio and its fire resistance. It can be used to reinforce plates by co-lamination, profiles by pultrusion and pipes as external layer. Finally, it can be over moulded on injected parts to give additional rigidity to PVC covers or boxes.