The mechanism of warp breakage during the weaving of polyester-fibre c
ontinuous-filament yarns is described. Techniques for the laboratory e
valuation of the weavability of sized continuous-filament yarn are sug
gested. Correlations between various weavability indices and sized-yar
n and size-material properties are estimated to determine which of the
methods gives a better representation of the relative weaving propert
ies of continuous-filament sized yarn. The performance of various size
materials when applied to polyester-fibre yarn is studied. The perfor
mance of sized microfibre yarn is also highlighted.