Notes on Packaging Materials

jiCharacteristics of Various Packaging Materials

Overview of Packaging Materials

• Different types of packaging materials include:

  • Paper and paperboard

  • Plastics

  • Glass containers

  • Earthware and ceramics

  • Metals

  • Natural materials (wood, straw, leaves, jute, textiles, bamboo, cane)

Paper and Paperboard

History

• Key raw materials for paper and board production include:

  • Bamboo

  • Softwood

  • Cane bagasse

  • Straw

  • Used paper

• Wood pulp is derived from any of the above materials.

Methods of Producing Wood Pulp

1. Mechanical Wood Pulp (G sound wood pulp)

   • Obtained by mechanically grinding timber.

   • Can be either bleached or unbleached.

2. Chemical Wood Pulp

   • Wood chips treated with chemicals at high temperatures to remove lignin.

   • Produces nearly pure cellulose fibers.

   • Types:

     • Sulphate Pulp (Kraft Pulp): High strength.

     • Sulphite Pulp: General purpose material.

3. Semi-Chemical Pulp

   • Combines milder chemical processing with mechanical treatment.

Coatings for Paper and Carton Boards

• Common coatings:

  • Clay and Calcium Carbonate: Enhance appearance and printability.

  • Fluorocarbon: Improves grease resistance for contact with fatty foods.

  • Silicone: Provides release properties for ovenable boards.

  • Polyethylene (PE): Water-resistant, grease-resistant, heat sealable.

  • Polypropylene (PP): Improved grease and heat resistance.

  • PET (Polyethylene Terephthalate): Strong and heat resistant.

  • Varnish: Provides high gloss/matte finish and protection.

  • Wax: Water-resistant qualities.

Boards for Food Packaging

• Types of boards:

  • Solid White Board: Made from bleached chemical wood pulp.

  • Folding Box Board:

  • Duplex: Liner from bleached chemical pulp; core from unbleached mechanical wood pulp.

  • Triplex: Outer liners from bleached pulp; middle from ground wood pulp.

  • Chip Board: Composed entirely of recycled waste paper; not food-safe.

  • White Lined Chipboard: Contains inner recycled plies; not suitable for strong odors or taint.

Carton

Definition and Making

• Carton: A receptacle made from carton board, thickness 250-1000 microns.

• Making Process (3 Stages):

  1. Printing: Usually in sheet form, via offset lithography.

  2. Cutting and Creasing: Carton blanks are cut out, and folding lines are created.

  3. Folding and Gluing: The flat carton is folded and glued into the final shape.

Varieties of Cartons

• Folding Cartons: Made from 10 to 36 point board, can fold flat.

• Rigid Boxes: Made from thicker boards (36-120 point), do not fold flat.

Corrugated Fibre Board Boxes

• Definition: Consists of one or more corrugated sheets faced with flat paper on both sides.

• Components:

  • Corrugating Medium: Fluted paper.

  • Liner: Flat paper glued to the corrugated sheet.

• Double Wall Board: 3 facings, using 2 fluted sheets.

• Triple Wall Board: 7 layers; 3 fluted, 4 liners.

Types of Flutes

• Flute Forms and Characteristics:

  • A Flute: 105-125 corrugations/meter, height 4.5-4.7 mm

  • B Flute: 150-185 corrugations/meter, height 2.1-2.9 mm

  • C Flute: 120-145 corrugations/meter, height 3.5-3.7 mm

  • E Flute: 290-320 corrugations/meter, height 1.1-1.2 mm

Advantages of Corrugated Fibre Board Containers

• Lightweight and reduces freight costs

• Space-efficient for storage and transportation

• Printable and decorative

• Resistant to infestation

• Versatile in shapes

• Can be tamper-evident or pilfer-proof

• Reusable and environmentally friendly

Disadvantages

• Not fully water-resistant

• Not puncture-resistant

• Low resale value

Plastics for Packaging

Common Types of Plastic Materials

• Flexibility in Packaging: Used for films, containers (rigid/semi-rigid).

• Types Include:

  • LLDPE: Linear Low-Density Polyethylene

  • HDPE: High-Density Polyethylene

  • PP: Polypropylene

  • PVC: Polyvinyl Chloride

  • PVDC: Polyvinylidene Chloride

  • PET: Polyester or Polyethylene Terephthalate

  • PA: Polyamides or Nylons

  • Regenerated Cellulose Film

Properties and Limitations of Specific Plastics

• LDPE (Low Density Polyethylene):

  • Properties: Low cost, good mechanical strength, water vapor barrier.

  • Limitations: Hazy, softens at 90°C, poor oxygen barrier, not oil/gas resistant.

• HDPE (High Density Polyethylene):

  • Stiffer, higher barrier properties.

  • Can be used in thin films and is waterproof; used for butcher wrapping.

• PP (Polypropylene):

  • Higher softening point (140-150°C), good grease resistance; used in snacks packaging.

Special Plastics for Specific Uses

• PVC:

  • Used for cling films, liquid bottles, sensitive to cancer causing substances from plasticizers.

• PVDC:

  • Low permeability; costly, used for foods sensitive to moisture.

• EVOH:

  • Excellent barrier attributes; high expense; used in sensitive food packaging.

Additional Plastics

• PET:

  • High tensile strength; good gas and oil resistance; widely used for carbonated drinks and food packaging.

• Polyamides/Nylons:

  • High vapor permeability, excellent strength, resistant to many solvents.

• Regenerated Cellulose Film:

  • Versatile in packaging, subject to specific quality codes based on properties.

Flexible Packaging

Types and Processes

• Laminated Materials: Multiple layers of materials for unique properties (e.g., plastic to paper).

  • Adhesives: Used to bond layers.

  • Extrusion Laminating: Involves molten polymer coating two webs being laminated.

Testing Packaging Materials

Tests Include:

• Grammage: Measurement of grams per square meter (g/m²)

• Calipers: For thickness; indicates compression strength.

• Cobb Test: Measures water absorption in papers.

• Bursting Strength: Indicates robustness of material.

• Puncture Resistance: Energy needed for material penetration.

• Compression Strength: Most significant measure for performance testing.