Plastic packaging material

Plastic as Packaging Material

1. Plastic as a Packaging Material Dr. Anil Pethe

2. What are plastics? Plastics may be defined as any group of substance, of natural or synthetic origins, consisting chiefly of polymers of high molecular weight, that can be moulded into a shape or form by heat & pressure. They usually consist of large molecules of organic materials which are based on certain building block molecules, undergo a process known as polymerization, a plastic or long chain polymer is produced. Other material such as accelerators, initiators, solvents & catalyst can be added during polymerization to improve the characteristics.

3. Advantages Light weight Reduced volume (warehousing & distribution cost reduction) No corrosion problems Good resistance to mould & bacteria. Generally inert chemically, but be wary of “solvents” Usually have good impact strength; difficult to break, if breakage occurs fragments tend to be less hazardous than glass. Wide design & decorative possibilities.

4. Disadvantages No plastic is totally impermeable to moisture, gases etc. Most plastics permit some passage of light. Even highly pigmented plastics & those with UV absorber are likely to let certain wavelengths through. Many are difficult to clean or are liable to attract dust & dirt under unfavorable conditions. May be permeable to, or subject to attack by, organic substances, particularly solvents. Subject to adsorption or absorption according to formulation ingredient. Light weight & thin wall section may require specific production line handling. Fully effective closing systems are sometimes difficult to achieve. Certain designs may show panelling or cavitation

5. Types of Plastics 1) Thermoplastic Polymers These are heat softening materials which can be repeatedly heated, made mobile & then reset to a solid state by cooling. Under conditions of fabrication they can be moulded by temperature & pressure. Eg . Polyethylene, PVC, polystyrene, polypropylene, nylon, polyester 2) Thermosetting Polymer These are polymers produced by a polymerization process involving a curing or vulanisation stage during which the material becomes ‘set’ to a permanent state by heat & pressure. Further heating leads to decomposition of the plastic. Eg . Phenolics , melamine, urea, alkyds, epoxides , certain polyesters & polyurathanes , cross linked polymers.

6. Plastics Used For Packaging 1. High Density Polyethylene (HDPE) Characteristics: Low – cost Moderately flexible Stiffer and has better barrier properties Chemical resistant Poor clarity Translucent in natural state and can be tinted with any opaque color. Odorless and tasteless

7. Advantages Low-cost Good moisture barrier Not attack by most solvent Disadvantages Poor barrier for oxygen & other gases Odors and flavors are sometimes lost Perfume or flavoring oil can transpire rapidly Stress-crack in the presence of some product

8. Applications For thin-wall blow- moulded containers Injection moulding of closures Rotational moulding for large containers such as carboys Industrial and consumer bags and thermoformed trays

9. 2. Low Density Polyethylene (LDPE) Characteristics: Odorless and tasteless Easily blended with such copolymers Highly resistant to most solvent Poor barrier for gases Softening temperature is around 210ºF Easily pigmented Good transparency Translucent and waxy in thick-walled container

10. Advantages Flexible Moisture barrier Tough Chemical resistant Light weight Low cost Heat sealable Disadvantages Not practical for rigid container and flexible packages Problem in flavors and odors Stress cracking Not recommended for oily products

11. Applications: Use in squeezable tubes and bottles Wrappers and bags for different products Thermoformed into trays, frozen food containers Coating material for bottle cartons, bacon wrappers and paperboard milk containers

12. 3 . Linear Low Density Polyethylene (LLDPE) Characteristics: Low-cost Light weight Superior toughness Rigid Flexible Moisture barrier Chemical and stress-crack resistant

13. Advantages: - Good tensile strength - Puncture resistance - Good impact and tear properties - Stress cracking and warding resistance Application: - For large-sized bagging and wrapping operations

14. 4. Polypropylene (PP) Characteristics: Heat and chemical resistance Tough & rigid Resist oil and greases Stress-crack resistance Fairly good barrier to moisture and gases High melting point

15. Advantages Light weight Low-cost Less shrinkage Disadvantages Low impact strength Sharp melting point Applications: Widely used in closures of all kinds Suitable for some boil-in-bag packages and containers Standard plastic in moulded container

16. 5. Polyvinyl chloride (PVC) Characteristics: Crystal clear Low in impact strength Tough and has good puncture resistance Good barrier properties (moisture and gases) Retains odors and flavors

17. Advantages Relatively inexpensive Tough clear Disadvantages Corrosive when overheated Yellows when exposed to heat or UV light Scratches easily seen Applications: Blister packaging for pharmaceutical and capsules Garment, box and pallet load wrapping applications

18. 6. Nylon Characteristics: Structurally strong Relatively low moisture absorption Good dimensional stability Heat sealability

19. Advantages Clear Good barrier properties to gases Excellent stability at both high and low temp. Disadvantages Can be oxidized causing nylon to lose strength Applications: Co-extruded with poly-olefins to enhance packaging properties Coating on paperboards, papers and foils Extrusion-blow-molded containers for hard to-hold chemicals

20. 7. Polyester (Polyethylene Tetraphthalate) Characteristics : Excels in strength, toughness and clarity Resistant to weak acids, bases and most solvents Not good barrier for gases

21. Advatages Fairly stiff material Excellent transparency Excellent heat, low temperature and water resistance Excellent oil, chemical and solvent resistance Excellent barrier to aroma and Flavor Disadvatages Poor seal property High cost

22. 8. Polystyrene (PS) Characteristics: Crystal clear and very hard, brittle and rigid Low melting point (190ºF) Poor impact strength Not good barrier for moisture or gases Odorless and tasteless

23. Advantages Clear and light weight Low in cost Easily molded, thermoformed and extruded into film Accept printing, metallizing and hot-stamping Disadvantages Slight tendency to shrink Discolor in strong sunlight Can craze and become cloudy Builds up static changes Easily Applications: Bottles for pharmaceutical tablets and capsules In molded forms for close containment of fragile products

24. 9. Polycarbonate Characteristics: Good clarity, impact strength, ductility and low controllable mold shrinkage Sterilizable and tolerates gamma radiation High-priced material

25. Advantages Great clarity, toughness and high softening temp. Dimensionally stable and processable Odorless and non-staining Disadvantages High- cost High permeation of moisture and gases Sensitive to oxygen and carbon dioxide

26. Plastic Processing : 1. Injection Molding - Grains of polymer are mixed and heated by a screw in a molding machine and injected under a high pressure into a cool mold.

27. 2. Compression Molding - powdered resin is put into a heated mold - mold closes under high pressure - Plastic cures in a minute, then molds open.

28. 3. Rotational Molding - also called rotomolding or rotational casting - Produces seamless, hollow parts of uniform thickness and without the internal stresses that can be created during conventional molding or thermo forming

29. Rotational Moulding Process

30. 4. Blow Molding - similar to glass making and used either a single or two stage process for producing bottles a. Extrusion Blow Molding - continuously extruded tube of softened polymer trapped between two halves of mold and inflated by compressed air to the shape of the mold.

31. b. Stretch Blow Molding - a preform is injection or extrusion - reheated to produce biaxial orientaton of the molecules and finally stretch blown c. Injection Blow Molding - polymer is injection molded around a blowing stick , then transferred to blowing mold. - compressed air is used to form final shape of container

32. 5.Thermoforming - film is softened over a mould, and a vacuum and/ or pressure is applied

33. Typical Technologies of Converting To give new processing to yield new value on the rolls that are wound thin substrates which are plastics film sheet, paper, foil and cloth. 1. Coating - Thin membrane that is coated liquid on the film sheet - Process of applying one or more layers of polymer latices or polymer melt to the surface of a substrate 2. Laminating made multiple layers by adhesives and extrusion molten resin 3. Printing to express conveyance of eye information and ornament 4. Metallizing - metals are vaporized and adhere to substrate

34. 5. Embossing - of set of concave-convex design to substrate by embossing roll - to make soft-feeling and mat surface 6. Slitting - film sheet is continuously slit constant position width of the product for secondary processing 7. Winding - is of set purpose to adjust edge of roll product and get rid rejective part.

35. Constituents in Plastic Plasticizers Fillers, Extenders, Lubricants Stabilizers UV absorber Slip additives/ anti-slip additives Anti-blocking agents Colourants-pigments & dyes Antioxidants Internal release agent Inhibitors (mould or bacteria inhibitor) Toughening agents- impact modifiers Flame-retarding agent eg- opacifiers, whitening agnet

36. Plasticizers Plasticizers improve the flow properties of material, increases softness & flexibility, & are found mainly in polyvinyl chloride (plasticised PVC) and the cellulosics. The most common PVC plasticizers are phthalate esteres, phosphate esters, sebacate & adipate esters, polymeric plasticizers. Fillers Filler is an inert solid substance Eg- carbon black, chalk or calcium carbonate, china clay, silica & magnesium carbonate The maximum limit of filler is upto 1:1 ratio , after which the binding power with the plastic is lost.

37. Toughening agent/ impact modifiers A few plastics which tend to be naturally brittle require an improvement in both Their drop (impact) strength & their top loading (compression) strength. In the case of polystyrene ,rubber is widely used as an impact modifier. Rigid PVC, when used as container may suffer weakness when subjected to 3-4 feet drop test & hence 15% of methyl methacrylate butadiene styrene (MBS) copolymer is added to improve impact strength.

38. Lubricants lubricants may be added either as an additive or at the fabrication stage as a processing aid. In general lubricants prevent adhesion with metal part. Lubricants may also improve the flow & thereby lower the temperature of the moulding operation. Eg in silicone polydimethyl siloxane may be used in LDPE & HDPE films to improve flow. Lubricants may be solid, such as waxes, stearates or liquid such as liquid paraffin.

39. Stabilizers Stabilizers increase the stability of plastic either during processing or during the moulded life of the material Stabilizers are frequently used to combat the combined effects of heat & light. UV Absorber UV absorber may be used for two reason: To protect the plastic from UV degradation To prevent the product degradation due to UV rays passing through the plastic. Chemically UV absorber may be based on substituted phenols or bezophenones. Eg- 2-hydroxy-4-n-octoxybenzophenone, & other benzophenones . Iron oxide & carbon are also used.

40. Slip additives Slip additives are widely used for films either made or used on relatively High speed equipment where any non-slip or drag properties might be detrimental to out put. The most used slip additives are oleamide & stearamide, since they operate at the film surface they can be physically removed by abrassion. Anti-slip additives These were primarily developed to provide good bonding for palletsied loads of plastic sacks & bag Without the additives plastic sacks would tend to destack & slide off when the pallet is moved or jerked.

41. Anti-blocking agent Both reel wound & sheet stacked materials may be difficult to separate due to blocking This may be caused by the smoothness of two surfaces giving rise to surface adhesion. It can be prevented by incorporation of finely divided silica or diatomacous earths eg. Mica Antioxidants Used to prevent oxidative degradation of certain plastics Polymers may be subject to various forms of oxidative attack during all stages of their life cycle. Eg. BHT,BHA Colourants Dyes & pigments are used

42. Extenders These are somewhat similar to fillers They are used as lower cost substitute for plastic Internal release agent These agents are somewhat similar to lubricants in that they provide release, particularly from metals eg mould zinc , calcium & magnesium stearate. Inhibitors Used to prevent microbial growth .

43. Residues in plastics Catalyst, initiators, hardeners Solvents Suspending agents Emulsifiers Accelerators Monomers Dispersing agent

44. Plastics used for pharma packaging Plastic Containers Plastic Collapsible Tubes Plastic Closures Blister Material Plastic Pouch

45. Plastic Containers Advantages Easily Formed Freedom Of Design Extreme Resistant To Breakage Light Weight

46. Plastic Collapsible Tubes Advantages: Low In Cost, Light In Weight, Durable, Flexible Pleasant To Touch, Unbreakable, Leak Proof, Odorless & Inert To Most Chemicals Able To Retain Their Shape Throughout Their Use Unique Suck Back Feature Disadvantages Permeation Of Gases

47. Plastic Closures The closure is an integral part of the pack, hence the word ‘pack’ covers the both the container & the closure system. The pack is only as effective as the closure employed, a successful marriage between container & closure is essential to the product shelf life & its acceptance during use. These are plastic devices which are used to prevent the contents from escaping and allow no substance to enter the container.

48. Types of closures 1.Screw-on closures 2.Crimp-on closures

49. 3.Roll-on closures 4.Friction closures 5.Press on closures

50. Blister Pack Advantages Excellent environmental protection Pleasing & efficacious appearance User convenience Child resistance Tamper resistance Blister Material Polyethylene Polystyrene / Polypropylene PVC Polyvinylidene Chloride Polychlorotrifluoroethylene

51. Plastic Pouch Advantages Ease of handling Used for unit dosage Materials used: Polyethylene Ethylene Vinyl Acetate Polyester

52. Plastic Defects Class-A defects Cracks and breaks anywhere in the container Any spot at heel or shoulder Rough cut off at finish, leading to leaky closure Weld lines that permit stress cracking in contact with product. Class-B Below minimum weight Any dimension outside of limit Uneven colour Rough or orange peel surface Class-C Blotchy or incomplete printing Streaky pigmentation Plastic trim in boxes delivered with closures Improper identification of cases.

53. Evaluation of Plastic Physical Chemical Biological