Why choose polythene for packaging

  • Polythene is produced more than any other polymer.
  • Polythene can be processed and reprocessed into many different products.
  • Polythene products are not biodegradable. Polythene is phot-odegradable. It will breakdown in sunlight in about 12 months.
  • Our stock polythene is suitable for food use.
  • Polyethylene plastic consists of a thermoplastic material and is used in a variety of consumer products.
  • Polyethylene is strong. Polyethylene can endure excessive temperatures. Polyethylene is lightweight. Polyethylene is water resistant. And polyethylene is economical.
  • Polyethylene has superb moisture resistance and durability make it the ideal choice for industrial packaging supplies.

Low density polyethylene verse high density polyethylene

  • Low density polyethylene (LDPE) is flexible and soft.
  • High density polyethylene (HDPE) is crispy and cloudy in appearance.

Poly bag gusset definition

  • Some bags have a gusset at the sides to help the bag open out more and enable a greater volume of items to be put in.
  • A good example is a refuse sack.
  • If a refuse sack is 16" × 25" × 39" this means it is 16" wide opening to 25" wide when the gusset is opened with a bag length of 39".
  • Some bags have a gusset at the bottom to enable a wide product to fit in.
  • A good example is a carrier bag.
  • If a carrier bag is 15" × 18" + 3" then the bag is 15" wide by 18" long with a bottom gusset of 3".

Poly bag size calculation

Poly bags size calculation
Lining a box
  • 1) Measure the width, depth and height of the box to be lined. The depth should be the shorter side.
  • 2) To determine the width (W) of the bag, add 1" to the width of the box.
  • 3) To determine the depth (D) of the bag, add 1" to the depth of the box.
  • 4) The length (L) of the bag is determined by adding the depth plus 1" to the height plus 1". Add another 5" to allow coverage of the box contents.
Round container
  • 1) Measure the diameter and height of the container to be lined.
  • 2) To determine the circumference (C) of the container, multiply the diameter by 3.14.
  • 3) To determine the width (W) of the bag, divide the circumference (C) by 2. Add 1" for a looser fit.
  • 4) To determine the length (L) of the bag, add the diameter to the height. Add 5" for overhang.
Square container
  • 1) Measure the width, depth and height of the container to be lined. The depth should be the shorter side.
  • 2) To determine the width (W) of the bag, add the width and depth. Add 2" for a looser fit.
  • 3) To determine the length (L) of the bag, add 1/2 the depth to the height. Add 5" for overhang.
Pallet cover
  • 1) Measure the width, depth and height of the pallet to be covered. The depth should be the shorter side.
  • 2) To determine the width (W) of the cover, add 1" to 2" to the width of the pallet.
  • 3) To determine the depth (D) of the cover, add 1" to 2" to the depth of the pallet.
  • 4) The length (L) of the cover is determined by adding 1/2 the depth to the height.

Poly bag seal types

  • Seal is term used to describe bottom of a poly bag.
  • Star seal is a multi-layered seal is full gusseted and then folded prior to sealing, allowing for the weight to be evenly distributed.
  • Gusset seals is a flat-style bag manufactured with both sides tucked in to form gussets.
  • Flat seal is a straight seal along bottom of a poly bag (like a pillow case).

Poly bag weight formula

  • Width × length × gauge / 1500 = lbs per 1000 bags / 2.205 = kgs per 1000 bags
  • Weight for 1000 12 × 18" 100 gauge polythene bags is 12 × 18 × 100g / 1500 = 14.4lbs / 2.205 = 6.53kgs per 1000 bags
  • Weight for 1000 24 × 32 × 60" 100 gauge gusset bags is 32 (full opening) × 60 × 100g / 1500 = 128lbs / 2.205 = 58.04kgs per 1000 bags
  • Weight for 1000 12 × 18 + 2" 150 gauge self seal polypropylene bags (for flap divide by 2 and add into length) is 12 × 19 × 150g / 1500 = 22.8lbs / 2.205 = 10.34kgs per 1000 bags

Poly bag size explanation

  • The size specification of a polythene bag can be confusing.
  • Poly bags are typically defined by size and gauge.
  • For a explanation of gauge please refer to our gauge thickness guide.
  • If two dimensions are specified. For example 20 x 30. This means the bag is 20 inches wide and 30 inches long. These sizes refer to bag being laid flat.
  • If three sizes are specified. For example 18 x 29 x 39. This means the bag has a gusset - i.e. it is tapered in at the bottom. A gusset is used in waste bags as it folds excess polythene into the bottom of the waste bag which is then expanded as the bag is filled. Therefore 18 refers to the width at the bottom of the bag, 29 refers to the width at the top of the bag and 39 refers to the length of the bag.
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