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Tbs                                                    TDC3 (6306 ) P3 
 
                              
  
 
 
DRAFT TANZANIA STANDARD  
 
 
 
Textiles – High Density Polyethylene (HDPE)/Polypropylene (pp) 
Woven Leno Sacks for packaging and storage of fruits and 
vegetables – Specification.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
Foreword  
 
 
This Draft Tanzania Standard has been prepared to help the users and traders of leno woven bags 
in proper packaging and storage of food stuffs.  
 
In preparation of this  Draft  Tanzania Standard assistance was derived from the following:  
 
IS 16187: 2014 Textiles — High Density Polyethylene (HDPE)/ Polypropylene (PP) Leno Woven 
Sacks for Packaging and Storage of Fruits and Vegetables — 
 
Acknowledgement is hereby made for the assistance derived from these sources.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
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 1. SCOPE   
This Draft  Tanzania Standard specifies the  specific  requirements and test methods for  High Density 
Polyethylene ( HDPE)/ Polypropylene ( pp) (excluding cordage) woven sacks  for packaging and storage of 
various fruits and vegetables . 
 
2. NORMATIVE REFERENCES  
The following referenced documents are indispensable for the app lication of this Draft Tanzania  
Standard. For dated references, only the edition cited applies. For undated references, the latest edition 
of the referenced document (including any amendment) applies.  
 
TZS 4, Rounding off numerical values  
 TZS 26 , Textiles – Determination of the conductivity, pH, water soluble matter, chloride and 
sulphate in aqueous extracts   
TZS 44, Textiles – Woven fabrics - determination of length and width of woven or knitted fabrics.  
TZS138, Textiles – Method for determination of colour fastness of textile material to rubbing.  
TZS 21, Textiles - Textiles – Woven or knitted fabrics \-determination of mass per unit length and 
per unit area  
IS 9833, List of Colorants for Use in Plastics in  Contact with Foodstuffs and Pharmaceuticals . 
IS 10910, Polypropylene and its copolymer for its safe in use in contact with foodstuffs, 
pharmaceuticals and drinking water.  
IS 7328, High density Polyethylene materials for moulding and extrusion.  
 
3. TERMS AND DEFINITIONS  
For the purpose of this Draft Tanzania Standard, the following  terms and  definition s shall apply:   
3.1 Weave  
form (fabric or a fabric item) by interlacing long threads passing in one direction with others at a right 
angle to them.  
 
3.2 Leno Weave  
is a weaving pattern in which adjacent warp tapes are twisted around consecutive weft tapes to form a 
spiral pair, effectively locking each weft in place . 
3.3 Leno Bags /leno sacks  
bags/ Sacks made from Leno weave fabric.  
3.4 Ends  
yarns running along the length of and parallel to the sacking selvedge.  
3.5 Picks  
yarns running across the width of the fabric and “perpendicular” to the sacking selvedge.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
 
4. CONSTRUCTION OF PP LENO BAGS  
PP Leno bags are constructed using plain weave in  which two warp yarns are twisted around the weft 
yarns to provid e a strong yet sheer fabric. The standard warp yarn is paired with a skeleton or 'doup' 
yarn; these twisted warp yarns grip tightly to the weft which causes the durability of the fabric. Leno 
weave produces an open fabric with almost no yarn slippage or mi splacement of threads . The paired 
warp tapes look like figure ‘8’ as shown schematically in Fig. 1.  
 
 
  
  
 
    Fig 1. Schematic representation of leno weave pattern  
 
5. Manufacture.  
5.1 Raw material.  
The tape shall be manuf actured from virgin food grade H igh Density Polyethylene 
(HDPE)/P olypropylene (PP) of the required quality.  If required by buyer, the tapes shall be manufactured 
from combination of HDPE/PP with Linear Low Density Polyethylene ( LLDPE )/Low Density Polyethylene 
(LDPE ) to get desired softness. The tapes can also be manufactured by using only Polypropylene. 
Tapes shall also be manufactured from UV stabilized HDPE/PP if desired by the buyer.  
 
5.2 Fabric  
The fabric used in the manufacture of HDPE/PP leno woven sacks shall be woven as a tube on a 
circular loom from the HDPE/PP tapes having width 3mm; Linear density 850 denier (weft) and width 
2mm; Linear density 600 denier (warp).  
If manufactured  from the combination of PP tapes and HDPE multifilament strands , the PP tapes shall 
have a width 3mm; lin ear density 850 denier(weft) and the weft shall have two strands of HDPE 
filaments with a linear density of 450 deniers .   
The denier of HDPE/PP tape used in the manufacture of leno woven fabric/sacks shall be subjected to 
the following tolerances:  
a) 10 percent ( %) on individual value, and  
b) 5 percent ( %) on average.  
 
The fabric shall be woven in accordance with leno weave with low weave density. The constructional 
particulars of fabric are given in Table 1.  
 
5.3 Sack  
5.3.1 Seam  
Leno sacks fabricated out of woven fabric shall have seam at the bottom and/or side. The stitching shall 
be done with two rows of either lock stitch or chain stitch. The two rows of stitches shall be separated 
from each other by about 5 mm and the outer ro w of stitching shall be approximately 8 mm from the 
outer edge of the sack. The stitching shall be done with single fold or double fold over seam to a depth of 
25 mm, so that the stitches pass through a minimum of four or six layers of the fabric respectiv ely as the 
case may be. The number of stitches/dm shall be 14 ± 2.  
 
5.3.2 Stitching Thread  
The material used for stitching shall be HDPE/PP tape or any other thread suitable for the purpose, 
compatible to the product being packed in the sack. The tape or thread used for stitching shall have at 
least 20 percent higher denier than that used for making of the sack. The stitching shall be uniform 
without any loose thread or knot.  
 
 
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 5.3.3 Bag Mouth  
The completely open mouth of the sack shall be hemmed with a fol d of minimum 25 mm and tapes shall 
not fray. Leno woven sacks shall be made available with a drawstring if required by the buyer. The 
drawstring shall be made of HDPE/PP narrow woven tapes or flat braided cords.  
 
5.3.4 Bag Dimensions and Carrying Capacity  
Type 1, sacks shall have nominal holding capacities of 25 kg and Type 2, sacks shall have nominal 
holding capacities of 50 kg as given in Table 1. The dimensions of the leno woven sack shall be as 
agreed to between  the buyer and the seller depending on sha pe, size and bulk density of the fruit or 
vegetables to be packed.  
 
6. REQUIREMENTS  
6.1 Sack Specifications  
The leno sacks shall conform to the requirements specified in Table 1.  
6.2 UV Resistance  
As agreed to between the buyer and the seller, the leno bags shall be made from UV stabilized 
HDPE/PP. The leno woven fabric or sacks made out of UV stabilized material shall have at least 50 
percent of the original breaking strength when tested after exposure to UV radiation as per the method 
given in Annex B.  
 
6.3 Mass of Bale  
The mass of bale of sacks (excluding packing materials) shall be within ± 3 percent of the mass 
calculated by multiplying the number of sacks with the average mass of sack specified in Table 1 or as 
agreed to between the buyer and seller.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 Table 1 – Requirements for PP Leno Bags.  
7. MARKING AND PACK ING.  
7.1 Marking on Sacks  
The Identification mark of the manufacturer, along with any information required by the buyer, shall be 
printed on the sacks, using ink or another suitable method that will ensure legibility during use.  
7.2 Packing  
The sacks shall be packed to form a bale using a covering layer of plastic woven fabric and suitably 
secured. The bale shall contain sacks as agreed to between the buyer and the seller preferably 500 and 
in multiples of 100 thereafter.  
 
7.3 Marking on bales  
The bales shall be marked with the following information:  
a) Name of the manufacturer,  
b) Type and size of sacks,  
c) Gross weight of the bale,  
d) Net weight of the bale,  
e) Month and year of manufacture,  
f) Any other inform ation required by the buyer, and;  
g) Recycling logo as given below for HDPE/PP  sacks . 
 
 
               
                      Fig 2. Recycling Logo.  
 
SN Parameter  Requirements  Tolerance  Test Method  
1 Mass per unit area (g/m2), min  45  TZS 21  
2 Dimensions  and capacity  
  
As agreed to between 
the buyer and seller  but 
the capacity of the bag 
shall  not exceed 100kg  
 
 ±2cm  - 
3 Mesh size , min  
Warp x weft (per inch)  
  
5 x 5  - TZS 20  
4 Breaking strength  N, min 
i) Warp way  
ii) Weft way   
530 
267 - TZS 22  
5 Seam strength ( both bottom 
and/or side seam),  N, min   
295 - IS 9030:  1979  
6 Ash content (for UV stabilized 
fabrics), Max, Percent  2.2 - ISO 3451 - 1: 
2008, Method 
A 
7 Average  Breaking strength and 
elongation at break of UV 
stabilized HDPR/PP fabric after 
been exposed to UV ra diation 
and weathering, min (N ). Not less than 50%  of original strength  Annex B .  
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 8. SAMPLING AND CRITERIA FOR CONFORMITY  
8.1 Lot  
All sacks of the same construction in a consignment shall be grouped together to constitute a lot.  
8.2 Lot Conformity  
The conformity of the lot to the requirements of the standard shall be determined on the basis of the test 
carried out on the samples selected from it.  
8.3 Sample Size  
The number of samples to be sel ected depends on the size of the lot and number of bales to be sampled 
shall be in accordance with col 2 and col 3 of Table 2. The number of sacks to be selected from the 
bales sampled shall be in accordance with col 4 of Table 2 for visual inspection, dime nsions, ends, picks 
and mass requirements. The number of sacks shall be in accordance with col 5 of Table 2 for breaking 
load of fabric and seam strength requirements. The number of sacks to be selected for breaking strength 
of sacks after exposure of UV r adiation shall be in accordance with col 6 of Table 2.  
8.4 Criteria for Conformity  
The lot shall be considered as conforming to the requirements of the standard if the following conditions 
are satisfied:  
a) The number of defective sacks in case of visual inspection, ends, picks and dimensions is up to 10 
percent of the sample size subject to rounding off the fraction to next higher integer.  
b) None of the bales of sacks weighs less than the respective lower specified limit after allowing 
tolerance of ±6 perce nt on individual Sack and ± 3 percent on the bale (6.3).  
c) The average seam strength is not less than the value specified and none of the individual value is 
more than 10 percent below the specified value.  
d) None of the samples after exposure to UV radiation an d weathering shall have breaking strength 
less than 50 percent of the original breaking strength.  
 
Table 2 Sample size and criteria for conformity   
SN 
 No. of 
PP/HDPE  
Sacks in a 
Lot No. of 
Bales to be 
Sampled  Sample Size for 
VisualInspection, 
Dimensions,Ends, 
Picks and Mass  
Requirements  Sample Size for 
BreakingStrength 
of PP/HDPEFabric 
before Exposing 
toUV Radiation and 
BreakingStrength 
of 
SeamRequirements  Sample Size for 
BreakingStrength of 
PP/HDPE  
Fabric after Exposing 
toUV 
RadiationRequirement  
i Up to 12 500  
 3 13 8 1 
ii 12 501 to 25 
000 
 5 20 8 1 
iii 25 001 to 50 
000 
 8 32 13 2 
iv 50 001 and 
above  
 12 50 20 2 
 
 
 
 
 
 
 
  
  
 
 
 
ANNEX A  
(Informative)  
METHOD FOR CALCULATION OF MASS OF SACKS  
 
A-1 CALCULATION OF MASS OF LENO SACKS  
A.1.1 Total mass of sacks comprises of:  
a) Mass of fabric;  
b) Mass of stitching tape or threads  
A.1.1.1 Calculate the mass of sacks with the help of the following formula as the case may be:  
a) Mass of tubular fabric:  
1) Single fold stitching = ( L + 30 mm + 25 m m) × 2 W × M × 10–6 
2) Double fold stitching = ( L + 55 mm + 25 mm) × 2 W× M × 10–6 
b) Mass of flat fabric:  
3) Single fold stitching  = (L + 30 mm +25 mm) × 2 ( W+ 30 mm)× M × 10–6 
4) Double fold stitching = ( L + 55 mm + 25 mm) × 2 ( W+ 55 mm) × M× 10–6 
c) Mass of stitching tape = L1 × T × 10–6 
 
or thread where ; 
 L= length of sack, in mm;  
L1 = approximate length of stitching tape or thread, in mm (top and bottom stitch);  
W= width of sack, in mm;  
M= mass of fabric, in g/m2and T = linear density of stitching tape, in tex.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
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ANNEXB  
(Normative)  
UV RESISTANCE TEST  
B – 1 To determine the effect of UV radiation and weathering on the breaking strength, the 
HDPE/PP Woven fabrics shall be exposed as given in A - 2 and A – 3. 
B – 2 TEST PROCEDURE  
The test shall be carried out with fluorescent UV – Lamp type B (313nm or its equivalent).  
The duration of the test shall be 192h (that is eight days) in continuous mode.  
The test cycle shall be: 8h at 60 ℃ ± 3 ℃ with UV – radiation alternating with 4h at 50 ℃ ±3℃ 
condensation. Irradiance level throughout the test shall be maintained at 0.63 (+0.04/ -0) W/m2. 
B – 3 TEST PROCEDURE  
B – 3.1 Determine the original average breaking strength of fabric as per test method specified in IS 
1969 (part 1)  
B – 3.2 Expose the specimens alternately to ultraviolet light and condensation in respective test 
cycle in continuous mode for total 192h.  
The type of fluorescent UV lamp, the timing of the UV and condensation exposure and the 
temperature of the UV exposure and c ondensation shall be specified in A -2. 
B – 3.3 Determine the average breaking strength of the fabric separately after UV exposure as 
mentioned above.  
B – 3.4 Determine the p ercent retention of original strength as follows:  
Percentage retention of original breaking strength = 𝑎
𝑏  𝑥 100 
Where  
a) a= average breaking strength before UV exposure as obtained in A – 3.1 
b) b= average breaking strength after UV exposure as obtained in A – 3.3 
NOTES  
1. The UV source is an array of fluorescent lamps (with lamp emission co ncentrated in the UV range).  
2. Condensation is produced by exposing the test surface to a heated, saturated mixture of air and water 
vapour, while the reverse side of the test specimen is exposed to the cooling influence of ambient room air.