 
 
     
          
 
 
 
DRAFT TANZANIA STANDARD  
 
 
 GDC 4 (2) DTZS  Stretch  Cling Film -Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 
 
 
©TBS 202 1                                                                                                      1st    Edition
 
1 
 1 Scope  
This draft Tanzania standard specifies requirements, method s of sampling and test for stretch  cling film  
used for wrapping  food to keep it fresh,  boxes, luggage  and palletized  products, such as tea, chemicals , 
machinery  and other similar applications for storage and safe transportation . 
This standard cover s flexible unsupported films made from natural  or synthetic  compound s of linear low-
density  polyethylene or any other polymeric m aterials or blend s. 
2 Normative references  
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document. For dated references, only the edition cited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies.  
ISO 527-3 :2018 Plastics — Determination of tensile properties — Part 3: Test conditions for films and 
sheets . 
ISO 7765 -1:1988 Plastics film and sheeting — Determination of impact resistance by the free -falling dart 
method — Part 1: Staircase methods . 
ISO 14782:1999 Plastics — Determination of haze for transparent materials . 
3.Terms and definitions  
For the  purpose of this document, the following terms and definitions shall apply ; 
 
3.1 cling 
 property of material’s  ability to adhere to itself or another surface  
3.2 flex resistance  
resistance of a material to crack or otherwise fail at flexing creases  
3.3 stretch cling film 
material that elongates when applied under tension and which, through elastic recovery, conforms to the 
item(s) packaged  
3.4 stress retention  
residual load expres sed as a percentage of the original load on the material a fter the test specimen has 
been maintained at a constant elongation for a specified time  
3.5 power stretch cling 
mode of stretch wr ap machinery operation in which wrap material elongation is achieved through the use  
of power assist pre  stretch device and relati ve load motion  
3.6 elastic recovery  
extent that a material  returns to its original length after being subjected to an extension , and  is expressed 
as a percentage  
 
3.7 linear low density polyethylene (LLDPE)   
2 
 copolymer or terpolymer of ethylene produced by catalytic polymerization of ethylene with other  1-alkenes  
3.8 manual stretch cling film 
mode of stretch cling film wrapping manually  
3.9 tear propagation resistance  
It is a force required to extend  a tear of stretch cling  film 
4. Types  
 
 Stretch film shall be classified into the following grades , 
a)  Grade 1 — Manual stretch cling  film. 
b) Grade 2 — Power stretch cling film. 
5. Requirements  
5.1 General requirements  
 
5.1.1 The material shall be  uniform in colour, texture and finish. The material  shall be free from streaks and 
foreign particles. There shall be  no other visible defects, such as holes, tea rs or blisters. The edges shall 
be free from nicks a nd cuts visible to unaided eye. The natural films s hall be free from pin h oles and free 
from defects that may  affect  the serviceability such as wrinkles, fold -over creases and gels.  
 
5.1.2 The material used fo r manufacturing natural stretch cling  film shall be linear low density polyethylene, 
having dens ity between 910 to 940 kg/m3 at 27°C or any polymeric material or blend that need s the 
requirement of this standard. Any additive, to impart clin g properties of the film may be added to the resin 
in qu antity as agreed to between the supplier and purchaser.  
 
5.1.3 The film shall be furn ished in the form of roll or in any other form as agreed to between the supplier 
and the purchaser.  
 
5.1.4 The film shall be free from any objectionable odour.  
 
5.1.5 The film shall have n o splices  or air bubbles . 
 
5.1.6  For food applications, only transparent stretch cling films made from food  grade non -recycled resins 
shall be used . 
 
5.2 Specific requirements  
5.2.1 Dimensional requirements  
5.2.1.1 Nominal thickness  
When tested in accordance with Annex A , tolerance on nominal  thickness at any one point for the average 
of five consecutive points across the width measured in a minimum of 25 mm increments for  various 
thickness shall be as given in Table 1 . 
Table 1 Tolerance on thickness  
Nominal Thickness  Tolerance, Percentage  
Up to and including 25 μm  ± 20 
Above 25 μm  ± 15 
  
3 
 5.2.1.2 Tolerance on width  
The tolerance on width shall be as given in Table 2 unless otherwise agr eed to between the supplier and 
the purchaser.  
Table 2  Tolerance on width  
Nominal width  Tolerance ,Percentage  
Up to 500 mm ± 5 
Above 500 mm and up to 1250 mm ± 8 
Above 1250 mm  ± 20 
 
5.2.2 Impact strength (Falling dart) 
When tested by the method determined in ISO 7765 -1:1988 , the impact failure load obtained from the dart 
of 66 cm ( ± 1 cm) shall not be less than the values given in Table 3 for appropriate average thickness of 
the film.  
Table 3 Impact Strength (Falling Dart)  
 
 
NOTE —The value of impact failure load for intermediate  thickness  may be obtained by interpolation  
5.2.3 Clarity and haze for transparent film  
Haze of the stretch cling film, when  tested in accordance with ISO 14782:1999 , shall conform to the 
requirements given in Table 4.  
Table 4 Clarity and Haze  
Clarity  45°Gloss  Haze, Percentage  
Normal clarity  30 to 35  10 to 15  
High clarity  >55 <10 
 
5.2.4 Ultimate tensile strength  
The minimum tensile s trength at break when tested in accordan ce with ISO  527-3 for various thicknesses 
of stretch cling film, at different levels of impact stre ngth shall be as given in Table 5. 
 
 
  
Average thickness  of the film (μm)  
Impact Failure Load Min (gf), 
Grade 1  Grade 2  
10 50 70 
15 60 80 
25 80 100 
35 100 120 
45 120 140 
50 130 150  
4 
  
Table 5  Ultimate Tensile Strength  
 
Direction   Tensile Strength  at break , Min (kg/cm2) 
Grade 1  Grade 2  
Machine direction (MD ) 200 300 
Transverse direction (TD)  175 250 
 
5.2.5 Elongation at break 
The elongation at break when tested i n accordance with I SO 527-3 for various  thicknesses  of stretch cling 
film, at different levels of impact strength shall no t be less than the values given in Table 6.  
Table 6  Elongation at Break  
 
Thickness  of the Film ( μm) Elongation at Break , Min (% ) 
Grade 1  Grade 2  
MD TD MD TD 
10 up to 20 300 400 400 500 
Above 20 up to 40  400 500 500 600 
Above  40  500 600 700 800 
 
5.2.6 Elastic recovery  and stress retention  
When tested by t he method given in Annex B , the elastic recovery and the stress retention in machine 
direction obtained at 150 percent elongation shall not exceed 60 and 70 percent respectively.  
5.2.7 Tear propagation  
When tested by the method given in Annex C , the tear propagation of stretch cling film shall not be less 
than the values given in Table 7  for appropriate average  thicknesses  of the film.  
Table 7  Tear Propagation  
 
Thickness  of the film (μm) Tear Propagation , Min (g/cm ) 
Grade 1  Grade 2  
MD TD MD TD 
10 up to 30 70 80 80 100 
Above  30 80 90 100 120 
 
5.2.8 Flex resistance  
When the film tested in accordance with ASTM  F392/F392M -11 (2015 ), it shall not show any sign of cut 
growth and/or initiati on of cracks and tears.  
 
5.2.9 Force of elongation  
The force taken by the specimen of 25 mm width at 150 mm/min when tested in accordance with IS O 527-
3, to an extension of 100, 150,  200 percent for various thicknesses of stretch cling film at different level s of 
impact strength, shall not be less than the values given in Table 8.   
5 
 Table 8  Force of elongation in machine direction  
Thickness of film 
(μm)  Elongation , Percent   Force ,Min( kg/cm2)  
10 to 30  100 50 
150 70 
200 100 
Above 30  100 80 
150 100 
200 125 
 
5.2.10  Self cling (Shear and peel strength)  
The shear and peel strength for cling stretch film shall be not less than 0.5  N/cm2 when tested with 
accordance with Annex D . 
5.2.11  Deviation  of gas transmission rate , %  
The determination of Oxygen  and Carbon dioxide  transmission rate for cling stretch film  used in food 
application  shall be conducted in accordance with  ISO 2556 . The deviation of the gas transmission rate 
shall be  20% wh en determined by  formula  shown in Annex E . 
5.2.12 Deviation of wate r vapour permeance, %  
The determination of water transmission rate  for cling stretch film  used in food application  shall be 
conducted in accordance with  ISO 2528 . The deviation of the gas transmission rate shall be  20% when  
determined by  formula  shown in Annex E.  
6.  Packing and marking  
 
6.1  Packing  
The roll of stretch cling film shall be packed as agreed between  the supplier and the purchaser.  
6.2  Marking  
 
Each roll shall be marked legibly with the following information:  
a) Manufacturer’s name and /or recognized trade mark . 
b) Type of material . 
c) Batch number . and date of manufacture . 
d) Product name .  
e) dimensions (width, length  and thickness)  
f) Application (food application  or non -food application ) 
 
  
6 
 7 Sampling  
7.1 Lot 
In any consignment, all rolls of stretch cling film of the same grade shall be grouped together to constitute 
a lot.  
7.1.1 Test for determining the conformity of the lot to the requirements of the specification shall be done on 
each lot separately. The number of rolls of the film to be selected for this purpose shall be in accordance 
with column 2 of Table 9. 
7.1.2 The rolls of stretch cling films shall be selected at random f rom the lot.  In order to ensure randomness 
of selection,  the following procedure may be adopted:   
Starting from any rol l of the film in the lot, count them in one order as 1, 2 .........etc. up  to r and so 
cm, where r is the integral part of N/n. Every rth roll of the film thus counted shall be withdrawn till 
the required n umber of rolls of the films are taken from the lot.  
7.2 Number of tests and criteria for Conformity  
7.2.1 From each of the roll of the film selected according to 7.1.2 approximately 10 m2 of the film of  full 
width shall be cut; care being taken to exclude not less than 2 metre lengths of film (or three full turns of 
the roll) from either end. The test specimen s for the various tests shall be cut from different parts of each 
of the 10 m2 pieces.  
7.2.2 Each of the pieces as obtained in 7.2.1 from a lot shall be examined for general requirements (see 
5.1), and dimensional r equirements (see 5 .2.1). Any piece which does not meet the requirement of any of 
the above characteristics shall be considered as defective.  
7.2.3 If the number of  defective found (see 7.2.2) is less than or equal to the corresponding permissible 
number of defective given in column 3 of Table 9, the lot shall be tested for the remaining requirements of 
the specification. If the number of defective found is more than the corresponding permissible number given 
in col umn 3 of Table 8 , one more lot of samples may be examined.  
7.2.4 The lot having been found satisfactory according to 7.2.3 shall be tested for specific requirements 
(see 5.2 ). For this purpose, the rolls already tested according to 7.2.2 and found satisfactory shall be used 
for testing any of these characteristics. Specim en(s) for these tests shall be cut from 10 m2 piece already 
taken from each roll/folded film selected (see 7.2.1),  
7.2.4.1  The lot shall be deemed to have satisfied these requirements if all the test results for different 
characteristics given  in 7.2.4 are  found meeting the relevant requirements of the specification.  
7.2.5 The lot shall be declared as conforming to the requirements of the specification, if the requirements 
for various characterist ics as given in 7.2.3 and 7.2.4 are satisfied.  
 
 
 
 
 
 
  
7 
 Table 9 Scale of Sampling and Permissible  Number of Defective  
 (Clauses 7.1.1 and 7.2.3) 
Lot Size  Number of rolls  Permissible number of Defectives  
1 1 0 
2 to 15  2 0 
16 to 40  3 0 
41 to 65  5 0 
66 to 110  7 0 
111 to 180  10 0 
181 to 300  15 0 
301 to 500  25 1 
501 to 800  35 2 
801 to 1300  50 3 
13001 and above  75 4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
8 
 Annex A  
(clause 4.2.1.1)  
DETERMINATION OF THICKNESS  
A-1 APPARATUS  
A-1.1 A dead weight dial micrometer with a flat anvil of 6 mm diameter or larger in area and 4.8 mm diameter 
flat surface on the head of the spindle or a spring dial micrometer (dial thickness gauge) which has been 
calibrated against a dead weight dial micrometer shall be used. In case of dispute, only dead weight dial 
micrometer shall be used and the reading shall b e taken between 15 s and 2 min after the load is applied.  
A-2 SPECIMENS  
Test five specimens, at least 5 × 5 cm2 in area, taken uniformly across the width of the test piece . 
A-3 PROCEDURE  
Dry and clean the surface of the anvil and spindle head, and of the s pecimen. Place the specimen on the 
anvil and lower the spindle head on to it slowly. The total load applied  by the spindle shall be 110 g.Make 
one measurement on each specimen approximately at the centre of the specimen. Take mean of the 
measurements of all  the specimens of a sample to obtain the average thickness of the sample.  
A-4 ASSESSMENT OF RESULTS  
The thickness of the film shall be determined on the basis of the mass per square meter of the film. 
Specimen  size 10 x 1 0 cm piece of the film. Balance capable of measuring to the nearest 0.1 mg mass of  
the film by the following equation:  
𝑻=𝑾
𝑨×𝑫 
where  
T= Thickness in microns;  
W =Mass of the specimen in  g; 
A= Area of specimen ( m2); 
D= Density in g /cm3. 
 
A-5 ACCURACY  
This method is capable of producing measurements with a maximum error of + 0.000 25 cm.  
 
 
 
 
 
  
9 
 Annex  B 
 
(Clause 5.2.6) 
 
DETERMINATION OF ELASTIC RECOVERY AND STRESS RETENTION IN MACHINE DIRECTION  
 
B-1 General  
This test method covers the measurement of recovery for extension and retention of stretch cling film . It is 
related to the tightness of a package.  
B-2 Apparatus  
B-2.1 Tensile Testing Machine, with a reversible chart . 
B-2.2 Specimen Cutter, capable of producing nick free 25 mm ± 0.03 mm testing strips.  
B-2.3 Micrometer, cap able of measur ing the thickness of the specimens.  
B-3 Test specimen  
B-3.1 Test specimen are taken from several rolls of the film and when possible, from several production  
runs of a product. Str ong conclusion about a specific property of a film cannot  be based on  a single roll of  
product.  
B-3.2 Cut five specimens parallel to the machine direction that ar e 25 mm wide and long enough to provide 
for an initial grip separation of 127 mm,  measure the thickness of each specimen. Condit ion the test 
specimens at  standard atmospheric condition for not less than 24 h prior to testing.  
B-4 Procedure  
B-4.1 Clamp the first sp ecimen in the grips so that it is free to slack but is not under tension.  
B-4.2 Start the testing machine and chart and elongate  the specimen at 15 0 mm/mi n to a n extension of 
100,150, and 200 perce nt and stop the testing m/c and chart.  
B-4.3 Wait 60 s or 24 h, during which time specimen will relax .  
B-4.4 When testing  materials of unknown response,  investigate  a series of times of recovery.  
B-4.5 Return  the crosshead to the original grip separation simultaneously reversing the chart .  
B-4.6 Wait 180 secon ds, re -elongate the specimen to the same extension .  
B-4.7 Repeat the pro cedure for other four specimens also.  
B-5 Assessment of results  
B-5. 1 Determine t he length of DE and AE in chart units and calculate the elastic recovery percent using  
following equation:  
Elastic recovery percent = (DE/AE) x 100  
B-5.2 Determine the length BE and GE in chart units and calculate the stress retention percent using the  
following equation:   
10 
 Stress retention percent = (GE/BE) x 100  
B-5.3 Read and record the force at point G in kg of  different percentage of elongations. Stress  retention at 
150 % elongation: the average stress  retention at 150 % elongation is 70% . Elastic  recove ry at 150 % 
elongation is 60 %. 
 
 
 
 
Figure 1: Load Versus Extension Curves  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
11 
 ANNEX C  
(Clause 5.2 .7) 
DETERMINATION OF TEAR PROPAGATION  
C-1 General  
This method covers the determination of the force measuring to propagate a tear in stretch cling film. 
C-2 Apparatus  
C-2.1 Tensile Testing Machine, with a reversible chart.  
C-2.2 Specimen Cutter,  
C-2.3 Micrometer,  
C-3 Test specimen  
The specimen shall be of  the single tear type and shall consists of strip 75 mm long by 25 mm wide and 
shall have a clean  longitudi nal slit of 50 mm long cut with a sharp cutter. Thi ckness to be measured below 
the slit. Minimum five strips to be tested each in the machine direction and transverse direction of the 
material being used.  
C-4 Procedure  
Secure tongue ‘A’ in one g rip and tongue ‘B’ ( see Fig. 2) in the other grip of the tensile testing machine 
using  an initial grip separat ion of 50 mm align the specimen so that its major axis c oincides with an 
imaginary line joining centre of the  grips. Using a grip separation speed  of 150 mm/mi n, start the machine 
and record the load necessary to the  tear through the entire unslit 25 mm portion o f the specimen. Take 
the average results of five specimen s in each of the principle film in each direction and report.  
 
 
Figure 2: Grips  
 
 
 
 
12 
 ANNEX D  
(Clause 5.2.10)  
DETERMINATION OF SELF CLING (SHEAR AND PEEL STRENGTH)  
D.1 Sample preparation  
Cut 10 sheets of sample 50 mm long and 25 mm wide, with every two sheets forming a set. Place the 
adhesive  sides of each set of samples face to face in a lap joint, the length of a lap joint being 15mm and  
the width of the lap joint being 25mm. Lay the samples on a smooth surface, us e a rubber roller (diameter 
of 40mm, length of 100mm, mass of 300g) and carry out reciprocation rolling and press on the lap joint  
three times, until there is no air left between the lap jointed layers of cling wrap film. Leave the prepared  
samples in an environment under test conditions for 20 minutes and then conduct the test . 
D.2 Procedure  
Stretch out each set of the samples on a tension machine and determine the force needed to separate  the 
two sheets of sample. The arithmetic mean value of the five sets shall be regarded as the result. The  
stretching velocity, using an appropria te test instrument, shall be 250± 50 mm/min. The self -cling (shear  
and peel strength) shall be determined by the formula ; 
 
𝑻=𝑷
𝒂×𝒃 
Where  
T – The self -cling (shear and peel strength), in Newton/centimetre2 (N/cm2) 
P - The force needed to separate the sample, in Newton  N 
b -The width of the lap joint in cm  
a - The length of the lap joint in cm  
 
 
 
 
 
 
 
 
 
 
 
  
13 
 ANNEX E  
(Clause 5.2.11 and 5.2.12 ) 
Determination of deviation of Gas Transmission rate and Water Transmission rate  
 
E.1 Deviation of  Oxygen Transmission rate (OTR ), % 
The deviation of the Oxygen  transmission rate shall be determined by formula ; 
𝜟𝒀=𝒀−𝒀𝟎
𝒀𝟎 
in which,  
Y – The actual measured oxygen transmission rate, in cm3/m2/day 
Y0 – The nominal oxygen transmission rate, in cm3/m2/day  
ΔY – The deviation of the oxygen transmission rate, percentage (%)  
 
E.2 Deviation of  carbon dioxide Transmission rate (OTR), %  
The deviation of the carbon dioxide  transmission rate shall be determined by formula ; 
 
𝜟𝑹=𝑹−𝑹𝟎
𝑹𝟎 
in which,  
R – The actual measured oxygen transmission rate, in cm3/m2/day 
R0 – The nominal oxygen transmission rate, in cm3/m2/day  
ΔR – The deviation of the oxygen transmission rate, percentage (%)  
 
E.3 Deviation of  Water Transmission rate (WTR), %  
The deviation of the  Water  transmission rate shall be determined by formula ; 
 
𝜟𝑾=𝑾−𝑾𝟎
𝑾𝟎 
in which,  
W – The actual measured oxygen transmission rate, in cm3/m2/day 
W0 – The nominal oxygen transmission rate, in cm3/m2/day  
ΔW – The deviation of the oxygen transmission rate, percentage (%)   
14 
 Bibliography  
1. ASTM F392/F392M -11(2015) — Standard Practice for Conditioning Flexible Barrier Materials for 
Flex Durability.  
 
2. KS 2437:2013 Stretch Cling Film -Specification.  
 
3. IS 14995:2001 Stretch Cling Film -Specification.  