Poly (ethylene terephthalate) was modified by a KrF excimer laser 248nm. It was observed that the PET surface developed a very often periodic roughness or ripple. The roughness size is in the micron range and the surface shows some sign of global melting. Irradiated samples were imaged and studied using atomic force microscopy (AFM) and scanning electronic microscopy (SEM). AFM was used to follow the morphological changes caused by subsequent laser pulses on the very same area of the irradiated PET samples. AFM also provided quantitative data on the laser induced surface and allowed three-dimensional imaging of nonconducting surfaces. Changes in surface morphology of PET fibres were found in relation to laser energy applied. The mean roll to roll distance increased with increasing laser energy. Merging of ripples was observed and believed to be a major reason of increased roll to roll distance. With approximately 50 to 200 pulses, ripple almost approached parallelism. No further change of PET surface was observed with more laser pulses applied since the fibre has disintegrated into “ellipsoidal segments”. Meander-like structures superimposed onto the top of the ripples were observed. The wetting property of PET due to laser treatment was also studied.

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Polyester microfibre fabrics were treated with UV Excimer Laser and Low Temperature Plasma (LTP) and then dyed with four commercially available disperse dyes of both high- and low- energy. Polyester irradiated with laser developed some kind of ripple like structures of micron size on the surface whereas sample treated with LIP produced some granules and smaller ripple. Ripples developed from either laser or LTP treatments shared the same characteristic as they are strictly perpendicular to the stress direction of the fibre. Dyeing results revealed that the dyeing rate of all dyes on polyester increased remarkably after treatments. Large improvement observed especially for half-time dyeing, T_1/2. The improvement in coloration is believed to be closely related with the ripple structure since it is expected that dyes particles are captured more in the ripple structure of the modified surface area. Lower crystallinity of both laser and LTP treated samples may also be the reason for the improved dyeability. A slightly colour fastness improvement on both treated samples was also observed.

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This paper describes a study on the development of stainless steel/polyester knitted fabrics for electromagnetic shielding applications. To facilitate knitting of stainless steel wires and to reduce the material cost, initially blended yarns of staple stainless steel and polyester fibers were fabricated by using the ring and open-end friction spinning methods. The stainless steel/polyester produced by ring and open-end friction spinning methods, and their knitted fabrics made from 14G flat knitting machine were developed successfully. Using a coaxial transmission line holder set-up, the electromagnetic shielding effectiveness (EMSE) of various knitted fabrics was carried out in the frequency range from 30kHz to 3000MHz. The variations of EMSE with the knitted structures, yarn type, and the blend ratio of stainless steel fiber and wire to the polyester fiber in the yarns are discussed. The results indicate that the proposed knitted fabric having higher EMSE can be used for the purpose of EMI shielding, as well as for some electronic and electrical applications.

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In order to clarify the size effect of an interlacer and easily choose conditions to process interlaced yarns with a desired number of tangles, we made 16 interlacers with various sizes of both yarn duct diameter d and air jet nozzle diameter d_n and measured the number of tangles of interlaced raw yarn. Then the number of tangles was formulated as a function of the interlacer sizes d and d_n the supplied air pressure p and the feed ratio F. Results obtained are as follows: (1) The polynomial combined with a Heaviside's step function expresses satisfactorily the distribution of the number of tangles, which takes maximum values as a function of p, F, d and d_n. It represents very well the distributions of the maximum number of tangles and both supplied air pressure and feed ratio which give the maximum number. (2) The maximum number of tangles does not monotonously vary with d and d_n, but theoptimum values of d and d_n exist. Both the supplied air pressure and the feed ratio which give the maximum number of tangles monotonously increase with an increase in d and a decrease in d_n.

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