1.2-6D*38-51mm PET staple fibers for spinning,white

The product designated 1.2-6D*38-51mm PET staple fibers for spinning,white identifies a solid, optical white poly(ethylene terephthalate) cut staple supplied for short- and medium-staple yarn formation. The first field specifies the nominal linear density range from 1.2 D to 6.0 D; the second field specifies the cut length range from 38 mm to 51 mm. The descriptor “white” indicates an unconverted, non-dope-dyed stock that may be optically brightened; it does not state a specific titanium dioxide addition, luster classification, spin finish chemistry, or virgin/recycled polymer origin. Under ISO 2076:2021, the generic fibre identity is poly(ethylene terephthalate) fibre. The product designation therefore functions as a dimensional and application code rather than a complete producer specification.

The values in the table are class-level commercial indicators for virgin, solid, optical white PET staple of this type, not a universal lot guarantee. A producer’s certificate of analysis should state whether the product is virgin or recycled, bright or semi-dull, and whether the finish is antistatic, cohesive, or low-fogging. The white designation alone does not establish compliance with food-contact regulations such as FDA 21 CFR 177.1630 or Commission Regulation (EU) No 10/2011; such compliance must be confirmed by the supplier against the intended application.

Spin finish is a boundary parameter. At 0.10 % finish, fibre cohesion in carding may be reduced and static fly may increase; at 0.20 %, the risk of finish transfer to drafting rollers and rotor deposits increases. The producer’s finish selection must therefore be matched to the intended spinning system: an antistatic cohesive finish may be suitable for ring spinning but not necessarily for high-speed air-jet lines where a low-fogging finish is required. The product designation does not define finish chemistry; the safety data sheet and the producer’s application approval establish compatibility with downstream processes such as knitting lubricants or sizing agents.

What drafting and carding limits are introduced by the 1.2 D to 6.0 D denier span?

On a mass basis, a sliver comprising 1.2 D fibre contains five times as many individual fibres as the same mass of 6.0 D fibre. The calculated circular diameter is approximately 11 µm for 1.2 D and 25 µm for 6.0 D at a PET density of 1.38 g/cm³. Bending rigidity scales with diameter to the fourth power, so the 6.0 D fibre is roughly 27 times stiffer in bending than the 1.2 D fibre. This ratio is a geometric consequence of the denier span rather than an empirical adjustment factor.

The higher fibre count per unit mass in 1.2 D increases the number of fibre-fibre contacts in the card web. If a high-speed card with metallic card clothing is operated at constant sliver weight, the fine denier fraction requires lower cylinder load per unit area or higher card clothing point density to maintain fibre separation; otherwise nep formation and flat waste can increase. The card clothing supplier’s recommended point density should not be exceeded. Conversely, the 6.0 D fibre is easier to open and card, but its higher bending rigidity can create sliver stiffness and drafting friction in ring frames. Draft-zone settings established for 1.2 D should not be transferred to 6.0 D without revising the break draft and cradle spacing.

Within the denier range, 1.2 D fibre is typically assigned to yarns requiring a fine count and a high fibre count per yarn cross-section, while 6.0 D fibre is assigned to coarser yarns and technical fabrics where stiffness and resilience are functional properties. Textile spinning practice commonly maintains a minimum of 40 fibres per yarn cross-section for ring-spun yarns. Because of this, finer denier permits a smaller yarn linear density without falling below the limiting fibre count.

Cut-length selection across 38 mm and 51 mm staple variants

The 38 mm cut is matched to cotton-system ring and compact spinning lines, where top roller drafting settings are typically staple length plus 5 mm to 8 mm. It also blends without excessive fibre length differential with combed cotton having an upper quartile length of approximately 31 mm to 33 mm. The 51 mm cut is used for semi-worsted, air-jet, and open-end lines where longer staple increases fibre retention in the drafting zone and can reduce yarn hairiness. The cut-length designation does not state the length distribution; a producer should report fibre length data per ASTM D5103-07, including upper quartile length and short-fibre content, because short-fibre content of 2 % to 5 % can shift spinning efficiency even when the mean length is unchanged.

For rotor spinning, the product is commonly introduced as a PET/cotton blend at 20 % to 65 % PET by mass. The 38 mm variant is generally better suited to rotor diameters below 32 mm, where longer fibres can increase wrapper formation in the rotor groove; the 51 mm variant is more commonly applied on larger rotor machines and in air-jet spinning, where nozzle entanglement benefits from longer fibre length. At high rotor speeds, the finish-on-fibre content should be kept at the lower end of the specified range to reduce rotor deposit formation; production-scale lines show that finish dropout and fibre fly are more sensitive to ambient humidity than to the denier value.

Before opening, the bales should be conditioned at 20 °C to 25 °C and 55 % to 60 % RH for 24 h to 48 h. Although PET has a moisture regain of approximately 0.4 %, freezing or high-humidity storage can create surface condensation on bale surfaces, which transfers to the opener and can cause lap-ups on the feed rolls. Pre-drying of the fibre is not required for moisture removal; thermal exposure above the glass transition temperature of approximately 70 °C should be avoided during handling because it can alter crimp geometry and increase static propensity. The product should not be stored in direct sunlight or in proximity to amine-based additives, which can promote aminolysis of PET and reduce molecular weight.

When the product is compared with dope-dyed, recycled, and hollow PET staple fibres

The optical white designation means that the product is not solution-dyed; it can be dyed with high-energy disperse dyes at approximately 130 °C under pressure. Unlike dope-dyed PET staple, the white fibre carries no pre-incorporated colorant that limits shade flexibility, but it also lacks the colour-fastness advantage of solution-dyed stock. For dark shades and critical wet-fastness applications, dope-dyed product may show less dye migration; for pastel shades and bright whites, the optical white version is used.

The product name does not differentiate between virgin and recycled polymer. If a buyer requires recycled content, the supplier must provide a claim under ISO 14021:2016, and the spinner should verify intrinsic viscosity. Virgin PET staple of this class is commonly produced from polymer with IV in the range 0.60 dL/g to 0.68 dL/g; recycled material may require solid-state polycondensation to maintain this range. A lower IV below 0.55 dL/g can reduce fibre tenacity and increase fibre breakage in high-speed drafting. The white designation therefore should not be read as a virgin-polymer mark.

The product classification as a spinning fibre in the 1.2 D to 6.0 D range implies a conventional solid round or solid cylindrical cross-section; it is not a high-bulk hollow filling fibre. Hollow PET staple, often produced in 7 D to 15 D, provides higher insulation and compressional recovery but can collapse during carding if the void fraction is high, producing waste and nep. This product is therefore distinct from hollow filling fibre even though both may be offered as white PET staple.

The comparative values are calculated from geometry and do not replace a mill trial. Actual yarn tenacity, hairiness, and nep count are yarn-structure-dependent and should be evaluated on the target spinning machine. For air-jet spinning of polyester-rich blends, the 1.2 D fibre provides the fibre count needed for high yarn uniformity, while the 51 mm length reduces lost fibres at the nozzle. The 6.0 D fibre is reserved for coarser counts and textured hand effects. Published data for this exact configuration is limited; lot-specific selection should therefore be confirmed on the intended equipment rather than inferred solely from the product designation.