CARPET FIBRE

The repeat length in the triclinic polymer crystals (75.3 nm) is significantly less than for PBT (86.3 nm) and PET (99.5 nm). This has been claimed to make the crystal more spring-like in the long axis resulting in enhanced resilience and wear resistance in carpet fibres to a level approaching that of polyamide fibres. 

In America there are promising signs for certain polymers. For example, poly(ethylene terephthalate) drinks bottles can be cleaned and recycled to give an acceptable grade of PET resin in a process that is economically viable. The recycled polymer is used as carpet fibre, furniture stuffing, or insulation. Waste nylon can also be recycled profitably. 

A process for the depolymerisation of Nylon 6 carpet fibre in the presenee of steam under medium pressure (800 to 1500 KpA, 100 to 200 psig) is described. The feasibility of the seheme was demonstrated using a small laboratory apparatus and the best run produced a 95% yield of crude eaprolaetam. The data obtained were used to construct a computer model of the process for both batch and continuous flow stirred reactors. 6 refs. 

The use is described of a process involving both hydrolysis and pyrolysis to recover caprolactam from nylon 6 used in carpet fibres. By means of precise temperature control and the use of a catalyst, nylon 6 can be isolated from the PP backing. The process has been developed by the National Renewable Resource Laboratory, and interest has been shown by AlliedSignal who are considering a cooperative research and development project. 

EDXRF has been used for comparison of the elemental composition of some 100 carpet fibres (both automotive and residential) for forensic source classification [260]. SEM-EDS is too insensitive for this... 

DuPont recovers used nylon carpets and converts them into new raw material either by mechanical or chemical recycling. The mechanically recycled material has already been approved for high-performance applications such as fan shrouds and other under-the-bonnet automotive applications. The chemical process generates virgin-quality material with up to 50% recycle content to give a new carpet fibre with the same wear resistance, stain resistance, and dyeability as the virgin material. 

The volume of discarded carpets may exceed the capacity of the engineering resin market. In this case, it would be necessary to turn discarded carpets into new carpet fibre. Fibre spinning demands the highest resin quality and tolerances. By chemically recycling the nylon feedstock generated by the separation process, DuPont can obtain a material that as is good as virgin for a recycle content of maximum 50 per cent (ammonolysis only produces hexamethylene diamine (HMD) and the other precursor of PA 66, adipic acid, must be made from oil to obtain PA 66). 

Figure 9.7 Photomicrographs of PA carpet fibres. (Reproduced with permission from E Hensen, Advances in Polymer Technology, 1984, 4, 3, 339, Figure 21.

It was determined that the carpet fibres were manufactured by the Wellman Corporation, and it was confirmed that no other fibre manufacturer was known to have made fibres similar in all respects - composition, cross-section and... 

Gries, T., Heintze, A. (1997), Status and Prospects of Polyester Carpet Fibres, Chemical Fibers International, 47, pp. 292-294... 

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