Case Study

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Here are 2 standard requirements of woven polypropylene bags from the official government. We’ll take it as case study, for better understanding packaging specifications.

1. USDA Agriculture Commodity Requirements for woven polypropylene bags
2. Pakistan standard specification for polypropylene woven sacks for packing (sugar)


Case study 1: USDA Agriculture Commodity Requirements for woven polypropylene bags

50-KILOGRAM WOVEN POLYPROPYLENE BAGS (Pinch Bottom Open Mouth Bags)

1.1 Woven polypropylene fabric and circular-woven style bags.

A. The color of the fabric shall be white, unless otherwise specified.

B. The polymer in the fabric shall be 100 percent virgin polypropylene with norecycled material.

C. The fabric in an unstressed state shall permit a minimum air flow of 3 cubic feet per minute per square foot and a maximum of 30 cubic feet per minute per square foot, when tested in accordance with ASTM Test Method D737, as amended.

D. The fabric shall be finished by coating or other suitable method to prevent slippage. Individual test results shall be 28 degrees or greater, when tested in accordance with TAPPI Test Method T-503-OM-84. The fabric shall accept and retain printing ink that will not rub or flake off to a degree where legibility is impaired.

E. The fabric shall be capable of resisting ultraviolet deterioration for a minimum of
200 hours of exposure in a weatherometer, when tested in accordance with Test Method 5804-Federal Standard 191, as amended. The fabric shall retain 70 percent of its original minimum tensile strength in each direction, after 200 hours exposure, when tested in accordance with Test Method ASTM D 5034 (Grab Test), as amended.

F. Bags may be flat tube or gusseted.

1.2 Sewing of bag seams

A. All bag seams shall be sewn in a manner which prevents the product from leaking through the seams during handling, storage, and distribution.

B. The color of the sewing thread shall be natural or white. The tensile strength of the sewn seams shall not be less than the tensile strength of the fabric in the body of the bag.

C. The top and bottom of the bag shall be heat cut or otherwise finished to prevent fraying or unraveling of the fabric during distribution. The bottom seam shall be constructed in accordance with Federal Standard 751a, SSn-1 Single Turnover, as amended. A minimum of 4 stitches per inch is required.

1.3 Bas size requirements

Circular woven polypropylene bags shall have the finished bag size of 23 inches by 39 inches, unless otherwise specified by the contracting officer.

1.4 Baling requirements

A. Bags shall be baled with 1,000 polypropylene bags to the base.

B. Bags designed to be top loaded with bulk grain shall be baled for export with a minimum 14 gauge steel wire, or a minimum of 3/8 inch wide by 0.015 inch thick steel strapping, or minimum 1/2 inch polypropylene strap of sufficient strength to withstand export distribution. The bags shall be baled in a manner that would protect the finished product during storage and shipment.

C. Required dimensions and counts shall be verified by in-plant quality control processes.


Case stydy 2: Pakistan standard specification for polypropylene woven sacks for packing (sugar)

  • 0. FOREWORD
  • 1. SCOPE
  • 2. CONDITIONING
  • 3. MANUFACTURE
  • 4. REQUIREMENTS
  • 5. PACKING & MARKING
  • 6. LABELLING
  • 7. SAMPLING AND CRITERIA FOR CONFORMITY
  • 8. APPENDIX-A
  • 9. APPENDIX-B

0. FOREWORD

0.1 ThisPakistanStandard was adopted by the Standards Development Centre on 21.08.2008 on the endorsement by National Standards Committee for Textile (NSCT), the draft having been finalized by the Technical Committee for Synthetic Textiles (Bags & Cordages) TC-15.

0.2 This standard was first published in 1992, since then many suggestions were received for improvements which after the consideration have been incorporated in this revision.

0.3 It is recognized that this standard does not attempt to cover all the varieties of Polypropylene bags that may be in demand either in the local or foreign market or official agencies. It is therefore; in no way implied that such varieties are not to be manufactured. This standard does not purport to include all the provision of a contract.

0.4 In drawing up this standard the views of the consumers, manufacturers, traders, and the technologists have been taken in to consideration by the technical committee the need for international co-ordination of standard enforced in different countries of the world for promotion and easy flow of international trade has been kept in view. The development of standard is a continuous process and therefore, it is hoped to review this standard periodical on the basis of experience gained and studies made.

0.5 In order to keep abreast of the progress in industry the Pakistan Standards are subject to periodically reviews suggestions for improvements shall always be welcomed and put up to the relevant committee for its consideration.

0.6 For the purpose of deciding whether a particular requirement of this standard is complied with final value, observed or calculated expressing the result of a test, shall be rounded off in accordance with PS: 103-1991 “Method & rules for rounding off numerical value”. The number of significant places retained in the rounded of values shall be the same as that of the specific value of the standard.

1. SCOPE

1.1 This standard prescribes the requirements of Polypropylene woven sacks suitable for packing Sugar.

2. CONDITIONING

Before testing all samples shall be conditioned in accordance with PS: ISO 139-2008 i.e. temperature 27 + 2 0C and relative humidity 65 + 2 %.

2.1 The period of conditioning of the samples shall be not less than 4 hours.

3. MANUFACTURE

3.1 Tape:

The polypropylene tapes used shall be made by virgin food grade granules, without addition of colour giving translucent look, and shall be polypropylene tape having minimum width of 2.5 mm. The linear density shall not be less than 920 Denier.

3.2 Fabric:

The fabric used in the manufacture of polypropylene sacks shall be produced from tapes (3.1) either in shape of tube or a circular loom or woven in a flat loom. The constructional details found suitable are given Table-1. The cloth shall be evenly woven and generally free from rips, tears, and mended area.

3.2.1Tubular Woven:

The sack tube is produced, in a continuous length on circular loom. The weft is passed via the shuttle through each layer, in turn; in such a way that it forms a tube in which the weft is continuous and it lies in the transverse direction of the finished sack.

3.3 Flat Woven:

In this form, polypropylene sheet are to be formed by weaving in plain weave, and the width so adjusted that when sacks are stitched out of it, shall conform to the sizes are prescribed in Table-1.

3.4 Sacks:

The may be produced from material woven as a tube (3.2.1) and cut the required length or converted from woven material (3.3) and stitched accordingly.

3.5 Seam:

If the sack is to be fabricated out of a flat fabric (as distinct from fabrication of a sack from tubular woven fabrics) the side and bottom of the sack shall be sewn and in case of tubular woven sack the stitching will only be done at the bottom. The stitching shall be done with single row of either lock stitch of chain stitch. The row stitching should be approximately 8 mm (min. 5 mm) from the outer edge of the sack. Stitching should be done with fold over seam to a depth of minimum 20 mm, so that the stitching passes through a minimum of four layers of the fabric. The number of stitch per decimeter shall be 16-20, the lock or chain stitches may be as recommended in PS: ISO 4915-2002 “Types of stitches”.

3.5.1

The material used for stitching shall be nylon / polyester, polypropylene filament or any other thread suitable for the purpose, compatible to the product being packed in the sack. The stitching shall uniform without any loose thread of knot.

3.6

Mouth of the sack: The mouth of the sack should be selvedged, hammed or heat cut, so that the tapes do not fray.

3.7 Capacity:

The sack shall have nominal capacity of 50 kg for Sugar.

4. REQUIREMENTS

4.1 Joint bags: The sacks shall not be made from joint pieces.

4.2 Mass: The mass of the sack as given in Table -1

4.3 UV-resistance test: It is desirable by buyer and seller that the sacks are stabilized for U/V light. The procedure is described in Appendix-A.

4.4 Drop test: It is desirable by buyer and seller that the drop test shall be carried according to PS: 4879-2008 and the related parameter are prescribed in Appendix-B.

5. PACKING AND MARKING

5.1 The sacks shall be marked with information as required by the buyer using suitable ink, and printing should be clear without any major smudges or missed portions.

NOTE: The common practice of marking involves the use of silk screens or stencil for printing the matter when the number of sack ordered is small. When large numbers of sacks are required, the accepted method is flex-printing. The inks found suitable for printing are those based on polyamide resin. The shade of the inks should be uniform.

5.2 100 sacks will be tied to form a bundle and these bundles will be gathered so that 1000 sacks shall be packed to constitute a bale, which shall be formed using a layer HDPE or PP woven fabric or any other suitable material and suitable secured.

5.2.1The Polypropylene sacks may also be marked with Standard Mark PSQCA.

NOTE: Note: The use of the Standard Mark is governed by the provision of the section XIII of PSQCA Act VI of 1996 and details of conditions, under which a Licence for the use of Standard Mark may be granted to manufacturers or processors, may be obtained from Director (Conformity Assessment) Standard Development Centre PSQCA Karachi.

6. LABELLING

6.1 Each bag shall be marked with the following:

i) Name of the inside material. ii) Net and gross weight of the material. iii) Name of the mill, initials or trade mark. iv) Date of manufacture/crop year. v) Date of expiry vi) Any other information required by the buyer or by the law enforce.

7. SAMPLING AND CRITERIA FOR CONFORMITY

7.1Lot: In any consignment, all the sacks of the same construction shall be grouped together to constitute a lot.

7.2 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.

7.3 The number of bales to be selected depends on the size of the lot and shall be in accordance with col. 1 and col. 2 of Table-2. The number of sacks to be selected from the bales sampled shall be in accordance with col. 3 of Table-2.

7.4 Criteria for Conformity: The lot shall be considered as conforming to the requirements of this 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 number to next higher integer.

b)   Mass of none of sacks tested shall be less than 6 percent of specified mass. However, mass of 1000 sacks constituting a bale or multiples thereof shall not be less than -3 percent of specified mass of the bale.

APPENDIX – A

A-1 UV-resistance test: The determination of the influence of UV-radiation and weathering on the breaking strength of woven polypropylene fabric shall be carried out in accordance with ASTM G 53-1988. The requirement may be matter of mutual agreement between the buyer and seller.

A-2 Test procedure: The test shall be carried out with fluorescent UV-lamp type-B. The duration of the test shall be 144 hours (i.e. 6 days). The test cycle shall be 8 hours at

+ 60 0C with UV-radiation, alternating with 4 hours + 50 0C with condensation.

A-3 Criteria for passing the UV-resistance test: After the test, the breaking strength of the tested material shall be at least 50 % of the original breaking strength.

APPENDIX – B

B-1 Drop test: The drop test shall be carried out on three sacks and shall comprise of following sequence.

a)    Flat dropping.

B-3 Flat dropping: The sack shall be dropped from a height of 1800 mm twice on one flat face and twice on the opposite flat face.

B-4 Criteria for passing the drop test: After each drop there shall be no rupture or less of contacts. A slight discharge e.g. from closures, upon impact shall not be considered a failure of the sack provided that no further leakage occurs after the sack has been raised clear of the ground.

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Specialized in producing international standard woven polypropylene bags for over 20 years. Custom sizes and printed bags made to order and shipped worldwide. - By Denzel Fan @google+
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