Strength Behaviour “Within Length”

StrengthBehaviour &quotWithin Length&quot


5.1Staple Strength (SS)

Basedon strength, Staple Strength (SS) ranks second after Fiber Diameter(FD) based on wool characteristics that influence its price andquality. While spinning a yarn, staple strength is a determinantfactor, as well as a determinant of the sale price of the wool(Pfeiffer and Lupton, 2001 Brown et al., 2002 Friend and Robards,2005 Botha and Hunter, 2010). According to Thompson and Hynd (2009),staple strength is the force that breaks a given thickness of woolstaple. It is the degree of wool staple resistance upon forceincrement. Further, Cottle (1991) states that staple strength as themaximum force that breaks a staple. This force is recorded in termsof Newton’s per Kilotex (N/Ktex). Essentially, staple strength isthe measurement of cross thickness (area) and linear staple densityof the wool that has been standardized into one gram per meter. Atfirst, the staple strength values were determined through a “flicktest” whereby the wool handler would personally consider the woolto be of quality based on his or her own experience (Denney, 1990Cottle, 1991). However, today, this is longer the case. The AutomaticTester for Length and Strength (ATLAS) machine is used for staplestrength qualification (Thompson et al., 1988 Pfeiffer and Lupton,2001).

Accordingto this ATLAS machine, at least forty measured staples should confirmwith the Australian standard (Reis, 1992 Masters et al., 1999 Joneset al., 2004). Less than thirty Newton per Kilotex, the wool isconsidered tender, while that above forty Newton per Kilotex areconsidered as “sound wools” and are most preferred and attract apremium from wool handlers. For the purpose of Staple Strength valuedetermination, wools are allotted into four main categories:

  1. Sound – between 25-30 N/ktex

  2. Part-tender- approximately 20N/ktex

  3. Tender – approximately 15N/ktex

  4. Rotten – less than 10N/ktex

Normally,the wool quality and prices decrease down from sound to rotten wherethe strength difference is because of intrinsic fiber strength(Cottle, 2010).

5.2Staple Breakage Region (SBR)

TheStaple Breakage Region (SBR) refers to the location where the staplebreaks during staple strength evaluation (Snowder, 1992 Wood, 2003Cottle, 2010). According to Cottle (2010), Staple Breakage Region isvital in estimating the performance of the wool processing. Further,Cottle relates staple breakage region as a linkage to the woolwastage level. A shorter fiber fragment is formed when SBR isestimated at the staple tip, and vice versa (Snowder, 1992 Wood,2003 Cottle, 2010). Commercially, the wool is more desirable whenthe SBR is in the middle of the staple (Cottle, 1991 Snowder, 1992Wood, 2003). Nevertheless, middle SBR can cause a mean decline in thestaple length.

Thompsonand Hynd (2009) investigated Staple Breakage Region, and they foundthat staple surface fractures are smooth and they occur either inoblique or in perpendicular to the fiber. In addition, they reportedthat there is a strong relationship between FDP (Fibre DiameterProfile) and SBR (Staple Breakage Region), with staples of varied FDPhaving greater breakage prevalence (Deng et al., 2007). This isespecially where fiber diameters are fine. Further, Deng et al.(2007) urge that fine regions are more flexible compared to thecoarser regions. Nonetheless, Staple Breakage Region is dependent onStaple Strength value (Jackson and Downes, 1979 Cottle, 1991Gourdie et al., 1992).