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How Do I Choose the Right Material for a Bag, Sheet, Cover or Liner?

The chart listed below describes important characteristics of the most popular film types

             Gas Permeability      
  A B B      
Type of Film Water Vapor Transmission O² CO² Specific Gravity Min. Film Heat Seal Temp. ºF Elongation % D-882
Polyethylene LDPE 1.2 250-840 495-5000 .910-.925 250 400
MDPE .6-1.0 165-335 500-840 .926-.940 260 350
LLDPE 1.2 250-840 495-5000 .915-.925 250 500-700
EVA Copolymer 12% 3.9 515-645 2260-2900 0.94 200 300-500
High Density .3-.65 33-250 250-645 .941-.965 275 100
Polypropylene, Oriented .3-.4 110 240-285 0.905 needs coating 60-100
Non-Oriented .5-.65 84-415 495-1350 .88-.9 325-400 250-500
Ionomer 1.3-2.1 226-484 656-1150 .94-.96 190-400 350-450
PVDC (Saran) .05-.3 .08-1.7 .04-10 1.6-1.7 250-300 40-100
Polyester, Uncoated 1.3 5   1.35   120-140
Polycarbonate 9.7 260 775 1.2 400-430 100
Nycon, Uncoated 24-26 2.6 4.7 1.1 350-500 250-500

A = Gas loss /24 hours /100 sq. inches /mil. @ 95°F, 90% RH (relative humidity)
B =cc /24 hr. /100 sq. in. /mil. @ 77°F, 50% RH, American Society for Testing and Materials D1434-63

How Do I Figure the Weight of a Bag?

Flat Bag: Opening = 20”, Length = 45”, Thickness = .0035

Formula: {Opening x Length x (Thicknessx1000)} /15 = Weight per thousand bags
Example: (20 x 45 x 3.5) / 15=3150 / 15 = 210 lbs per thousand bags

Gusset Bag: Opening = 30”x25”, Length =65”, Thickness = .004

Example: {(30+25) x 65 x 4} /15 = 1430 / 15 = 953.3 lbs per thousand bags

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