Process for fabricating polymeric articles
Process for the production of a polymeric article by: (a) forming a ply having successive layers, namely (i) a first layer made up of strands of an oriented polymeric material; (ii) a second layer of a polymeric material; (iii) a third layer made up of strands of an oriented polymeric material, wherein the second layer has a lower peak melting temperature than that of the first and third layers; (b) subjecting the ply to conditions of time, temperature and pressure sufficient to melt a proportion of the first layer, to melt the second layer entirely, and to melt a proportion of the third layer; and to compact the ply; and (c) cooling the compacted ply. The resultant articles have good mechanical properties yet may be made at lower compaction temperatures than articles not employing the second layer, leading to a more controllable manufacturing process.
1. A process for the production of a polymeric article, the process comprising:
a) forming a ply comprised of layers of the same type of polymeric material including:
i) a first layer derived from strands of an oriented polymeric material selected from the group consisting of polyethylene, polypropylene, polyoxymethylene or polyester;
ii) a second layer derived from a polymeric material selected from the group consisting of polyethylene, polypropylene, polyoxymethylene or polyester;
iii) a third layer derived from strands of an oriented polymeric material selected from the group consisting of polyethylene, polypropylene, polyoxymethylene or polyester;
wherein the second layer has a lower degree of molecular orientation and a lower peak melting temperature than that of the first and third layers;
(b) subjecting the ply to conditions of time, temperature and a single pressure sufficient to melt at least 10% but no more than 30% by volume of the first layer, to substantially melt the second layer and to melt at least 10% but no more than 30% by volume of the third layer; and to compact the ply; and
(c) cooling the compacted ply.
2. The process of claim 1 wherein the second layer has a peak melting temperature at least 5° C. lower than the peak melting temperature of the first and third layers.
3. The process of claim 1 wherein the second layer is of thickness not exceeding 100 μm.
4. The process of claim 1 wherein the second layer is of thickness of at least 5 μm.
5. The process of claim 1 wherein the second layer is preformed, and laid onto the first or third layer in step (a).
6. The process of claim 5 wherein the second layer comprises multiple layers.
7. The process of claim 1 wherein the compaction pressure does not exceed 10 MPa.
8. The process of claim 1 wherein the strands are in the form of tapes.
9. The process of claim 1 wherein not more than 20% of each of the first and third layer melts.
10. The process of claim 1 wherein the proportion of the total ply which melts in the process is in the range 1-35% (vol/vol of the total ply).
11. The process of claim 1 wherein the second layer comprises a film.