Packaging Materials PDF

Packaging Materials Plastics Polyolefins Copolymers of ethylene Substituted olefins Polyesters Polyamides Glass Metal Paper  Packaging Materials: Glass It is an inert packaging material with absolute barrier to gases and moi...

Packaging Materials Plastics Polyolefins Copolymers of ethylene Substituted olefins Polyesters Polyamides Glass Metal Paper  Packaging Materials: Glass It is an inert packaging material with absolute barrier to gases and moisture making it versatile packaging material to retain the flavor and freshness of delicate food products like beer and wine. The other advantages of using glass are that it can withstand high ADVANTAGE thermal processing conditions, provides good insulation, can be formed into different shapes, and can be supplied in different colors with an optical transmission between nearly opaque and nearly transparent. Additional oxide coatings help to improve the mechanical properties and give a barrier against chemical attack. Heavy weight, and fragility to internal pressure, impact and thermal shock are some of the limitations for their extensive DISADVANTAGE use in food industry. Packaging Materials: Glass An amorphous, inorganic product of fusion that has been cooled to a rigid condition without crystallizing. Although rigid, glass is a highly viscous liquid that exists in a vitreous or glassy state. A typical formula for soda-lime glass o silica, SiO2 68–73% o calcia, CaO 10–13% o soda, Na2O 12–15% o alumina, Al2O3 1.5–2% o iron oxides, FeO 0.05–0.25% Packaging Materials: Glass ✓ Excellent barrier to water vapor, gases, and odors. × Incorrectly designed or applied closure may negate the benefits that glass packaging offers in protecting foods from deterioration. - The two main types of glass containers used in food packaging are; Bottles (which have narrow necks) Jars (which have wide mouths or openings) - Approximately 75% of all glass food containers are bottles. - Approximately 80% of glass container is clear, the remainder being mainly amber or green. Today’s glass containers are lighter but stronger than their predecessors, that is how glass container has remained competitive and continues to play a significant although declining role in the packaging of foods.  Glass Container Preferences Glass Packaging Institute  Glass Container Preferences Glass Packaging Institute  Glass Packaging Production Glass Packaging Institute  Glass Container Trends Lightweighting – 1966 beer bottle: 11 oz – 2000 beer bottle: 6.5 oz Development of Narrow Neck Press & Blow Process – Better distribution of glass throughout the bottle – Glass thickness varies with need for strength Improvement of Surface Treatments (reduced scratching) Innovative Container Shapes, Labels & Decorating Packaging Materials: Metals - Four metals that are commonly used for the packaging of foods: Aluminum (Al) Chromium (Cr) Steel Tin (Sn) - Tin and steel, and chromium and steel, are used as composite materials in the form of tinplate and electrolytically chromium-coated steel (ECCS) or tin-free steel (TFS). - Aluminum is used in the form of purified alloys containing small and carefully controlled amounts of magnesium and manganese.  Packaging Materials: Metals The basic metals used for food packaging are steel and aluminum. Steel has to be plated against corrosion by tin (thus giving tinplate) or chromium. Tin resists corrosion from water, but can be corroded by acids and alkalis They offer excellent barrier properties, physical protection, printability, consumer acceptance, and recyclability. Tinplate is produced from low-carbon steel, coated on both sides with a thin layer of tin. In most applications, they are further coated with epoxy or polyester resins to provide an additional barrier to the food materials against corrosion. Containers from tinplate or aluminum are commonly used in retort processing of fruit and vegetables, meat, fish, pulses, cans for drinks, containers for baby foods or powders, confectionery, etc. Aluminum is further used to produce flexible packaging materials like foil, laminated paper/plastic films, and metalized films. It has several advantages over other metals such as light weight, corrosion resistance and good recycling properties. Packaging Materials: Metals Aluminum, the earth’s most abundant metallic constituent, is used to manufacture both metal cans and thin foil in thicknesses ranging from 4 to 150 µm; foils thinner than 20 µm contain minute pinholes that are permeable to gases and water vapor. In both applications, alloying agents including silicon, iron, copper, manganese, magnesium, chromium, zinc, and titanium are added to impart strength, and improve formability and corrosion resistance.  Metal Containers Steel Cans – Food Cans (most) – Beverage Cans (few) – Aerosol Cans (minor use) Aluminum Cans – Food Cans (few) – Beverage Cans (most) – Aerosol Cans (minor use) Aluminum Trays and Pans Aluminum Foils Aluminum “Bottles”  Metal Container Advantages Metal impervious to H2O, O2, CO2, aromas, etc. Lighter weight than glass – Glass bottle ~220g, steel can ~ 35g, aluminum can ~15g. Can double-seam closure hermetically sealed Impervious to light High heat resistance High resistance to physical and thermal shock Faster heat processing than glass container Tamper evident Recyclable Metal Container Disadvantages Multi-step manufacturing One shape (shaped cans expensive & difficult to run) Cylindrical shape occupies excess space in storage Do not allow viewing of product Non-hygienic to drink from can Not microwaveable Perceived as “old fashioned” &/or do not add value Not refillable or reclosable/resealable (generally)  Metal Container Utilization Al Soft Drink Al Beer St Human Food St Pet Food Can Manufacturers Institute Paper Packaging Packaging Materials: Paper Paper is another commonly used material in the packaging of several food products. Plain paper is hardly ever used for food packaging alone. It has to be modified with several additives (lacquers, waxes, resins, etc.) or extrusion coated with other polymers to improve the barrier properties. Paper and paper boards are used in several forms such as corrugated boxes, cartons, bags, sacks, and wrapping paper. Packaging Materials: Paper Selected forms of paper used for packaging: 1. Kraft paper - Available as natural brown, unbleached, and bleached white. It is the strongest type of paper and is used for bags and wrappings. 2. Sulfite paper - It is usually glazed to improve the appearance, wet strength, and oil resistance. Sulfite paper is lighter and weaker than kraft paper but has high print quality. It is often used in plastic or foil laminates. 3. Densified and greaseproof papers of different types For example, glassine or parchment is used to package biscuits, confectionery, and fats. They are resistant to fat but have high moisture permeability. 4. Paperboard - Available in several forms (whiteboard, solidboard, chipboard, fiberboard, and paper laminates), mainly used as secondary packages to improve the handling and distribution of food products. Packaging Materials: Paper ❑Almost all paper is converted after manufacture by undergoing further treatment such as embossing, coating, laminating, and forming into special shapes and sizes such as bags and boxes. ❑Further surface treatment involving the application of adhesives and printing inks are common, depending on the end use. ❑Disadvantage: Paper and paperboard are poor barriers to gases and water vapor; uncoated paper packaging provides little more than protection from light and minor mechanical damage. Packaging Materials: Paper In many packaging applications, a barrier is needed against water vapor and/or gases such as O2. A water barrier can be formed by changing the wettability of the paper surface with sizing agents, whereas coating the paper with plastic polymers provides a good barrier to gases and water vapor. Beverage cartons consist of layers of paperboard coated internally and externally with low density polyethylene (LDPE), resulting in a carton that is impermeable to liquids and in which the internal and external surfaces may be heat sealed. There may also be a thin layer (6.5 µm) of aluminum foil, which acts as a gas and light barrier. Paper/board Advantages ❑ Provide barrier to light ❑ Paper can be made into a variety of single-wall bags (e.g., grocery bags) and multi-wall bags (e.g., flour, sugar) ❑ Paperboard provides strength and mechanical protection in many packages ❑ Paper and paperboard can be coated or laminated with wax, ❑ LDPE, PP or PET to improve H2O and O2 barrier properties and/or allow heat-sealability (LDPE) or heat-resistance (PP or PET) ❑ Uncoated/unlaminated paper and paperboard can be recycled Paper/board Disadvantages Negligible moisture, gas, or microorganism barrier properties when not coated or laminated Not heat sealable when not coated or laminated Coated or laminated paper and paperboard are, in general, not recyclable  Paper Plastic Glass Metal Paper and cardboard / Plastic / Aluminium Plastic Metal  Paper Plastic Foiled paper lid Plastic Glass lid lid  Plastics / aluminum Glass Paper Polypropylene Low Density Poly Ethylene Plastics / aluminum- Paper and cardboard / Polyethylene Smooth Cardboard Polypropylene plastics/aluminum- terephthalate Paper  Polyethylene Paper and cardboard / White Glass Terephthalate plastics/aluminum- Paper Packaging Material Properties Mechanical Properties Optical Properties of Glass and Plastic Packaging Barrier Properties of Plastic Packaging Factors Affecting Permeability ADDITIVES IN PLASTICS Early in the development of the plastics industry it was realized that to obtain better products, additives needed to be added to the base polymer. Within the context of thermoplastics materials technology, the term additive is used to denote an auxiliary ingredient that enhances the properties of the parent polymer without appreciably altering its chemical structure. In food packaging, all additives should have received clearance by the appropriate food regulatory authority. Processing Additives The degradation of polymers frequently involves oxidation reactions by a free radical mechanism, and at high temperatures, interaction of O2, with C-H bonds leads to the formation of hydroperoxide groups. These decompose into very reactive OH radicals and lead to molecular scissions. Because it is practically impossible to eliminate O2 from the system, additives are used to inhibit oxidation reactions. This is accomplished by using primary stabilizers or antioxidants such as hindered phenols or aromatic amines, which interrupt the chain reaction by combining with the free radicals; secondary stabilizers or peroxide decomposers such as organic thioesters, phosphites and metal thiocarbamates, which react with hydroperoxides as they are formed; and chelating agents or metal deactivators such as organic phosphites and hydrazides, which protect the polymer by immobilizing metal ions through coordination reactions. Processing Additives With PVC, heat stabilizers or acid absorbers must be used to retard the decomposition of PVC into HCl and dark, degraded polymers The tendency for polymers such as PVC and polyolefins to stick to metal parts during processing can be reduced by adding lubricants such as PE waxes, fatty acid esters and amides, metallic stearates such as zinc and calcium stearate, and paraffin. Plasticizers Brittle polymers such as PVC must be plasticized to obtain flexible films and containers. The plasticizer also gives the material the limp and tacky qualities found in "cling" films. About 80% of all plasticizers are used in PVC. Typically, phthalic esters are used, as well as epoxidized oils and low- MW polyesters. Internal plasticization may be brought about by copolymerization as in the case of PVC, which can be copolymerized with vinyl acetate, ethylene or methylacrylate. Antiaging Additives Aging is the process of deterioration of materials resulting from the combined effects of atmospheric radiation, temperature, O2, water, microorganisms and other atmospheric agents (e.g., gases), indicating that a chemical modification in the structure of the material has occurred. Antioxidants have already been mentioned under processing aids, but they are also necessary in polymeric films such as PP, which degrade in the atmosphere. BHT has been cleared by the FDA and acts as a free radical scavenger. Organophosphites act as hydroperoxide decomposers. It is common for different antioxidants to be used together for synergistic effects. UV stabilizers are used to prevent the deterioration of polymeric films by photooxidation. They act by absorbing high-energy UV radiation and releasing it as lower-energy radiation.  Antifogging films In some food packaging applications, moisture tends to condense as small droplets on the internal surface. Antifogging films also let consumers see food in packages clearly. Antifogging polymeric films prevent the formation of fog inside the food packages, for example fresh produce and raw meat packages. The antifogging property is essential for the packaging film when it is used for packaging of frozen products. Untreated LDPE and pullulan-coated antifogging film after removal from the refrigerator (7 days at 4 °C) at 20 °C.  Antifogging agents Antifogging materials are typically surface-active agents which consist of two parts: a hydrophilic head and a lipophilic tail; examples include glycerol fatty acid ester, polyglycerol fatty acid ester, a fatty acid ester of polyethylene glycol, alkyl ether of polyethylene glycol, ethoxylated alkyl phenol, sorbitan ester, ethoxylated sorbitan ester, and alkanol. When the antifogging agent incorporated in a polymer matrix, the antifogging agent migrates from the matrix to the film surface, reducing the interfacial tension between the polymer and the water drops. As a result, the water drops spread across the film surface and form a continuous thin layer. These so-called antifogging agents can be applied on the surface of the material or compounded internally in the packaging material at levels ranging from 0.5% to 4%.  Antistatic agents Static electricity is generated on a polymer surface by friction or by rubbing it against another surface. It can also be generated on fast-moving film during converting operations or on filling lines. Antistatic agents are used to prevent the accumulation of electrical charges in polymeric films, an undesirable effect caused by the fact that polymers are nonconductors of electricity. Electrification of films results from a segregation of charges (electrons and ions), which occurs when two surfaces are parted after close initial contact. The addition of ethoxylated fatty amines, polyhydric alcohols and derivatives, and nonionic and quaternary ammonium compounds overcomes the problem; they migrate to the surface and form a conducting layer through the absorption of atmospheric moisture, which permits the discharge of electrons. Antistatic agents Antiblocking agents Many packaging films or sheets tend to stick together because they are nonconductors of electricity, a phenomenon known as blocking. Anti-block agent reduces the friction between packages so that they can be easily separated from each other. It also ensures that exactly one cup or tray is picked up at automated filling lines. Blocking (which may develop under pressure during storage or use) can be reduced by colloidal silica, clays, starches and silicones that may be applied to the surface either during or after processing to reduce blocking. Anti-blocking agents are used at levels ranging from 0.1% to 0.5%. Recommendations for Antiblock Additives  Antiblocking agents Chemically inert, inorganic antiblock additives are most commonly used. Inorganic antiblock additives migrate to the film surface, partially stick out and create a microroughness of the film surface A barrier layer is formed on the plastic film surface, thus inhibiting the two adjacent plastic film layers’ adhesion. Slip agents Slip is when polymeric films slide parallel over each other. Slip is a surface effect. Slip is quantified via the coefficient of friction (COF). If films have a high COF, individual film layers have a high surface friction and tend to stick together instead of sliding over one another. Most commonly, migrating slip agents are fatty acid amides. Optical Property Modifiers The optical properties of a material from a technological aspect are normally described in terms of their ability to transmit light, exhibit color and reflect light from the surface (i.e., gloss). The majority of food packaging films are not pigmented, although some are colored by the addition of colorants that can be dyes (which are soluble in the plastic and tend to migrate, thus limiting their use) and pigments (which are insoluble in the plastic matrix). The principal pigments for use as colorants in packaging are carbon black, white titanium dioxide, red iron oxide, yellow cadmium sulfide, molybdate orange ultramarine blue blue ferric ammonium ferrocyanide, chrome green (Cr2O3). The FDA has questioned the use of some of these colorants in packaging material in contact with food, its concern being with colorants that can migrate from the packaging into the food.  Foaming Agents Foaming or blowing agents are used for the production of cellular products and are normally classified into physical and chemical types, according to whether the generation of gases to produce the cells Micrographs showing the cellular takes place through a physical blowing agent (i.e., structure of polypropylene foams inert gases) or by a chemical process (i.e., thermal produced using CO2 as blowing agent decomposition reactions that result in evolution of gases). Today, expanded and extruded PS foams are made using mainly CO2 or sometimes a light aliphatic hydrocarbon such as pentane or butane as the blowing agent. Expanded PET, PP and PVC foams are produced using chemical blowing agents such as CO2 and N2. Cellular structure of PP foams produced using different amounts of azodicarbonamide Plastic Food Packaging Material Advantages Low-cost (package manufacturing and storage) Often practical for in-line package formation Moldable Heat sealable (most) Light weight Transparent (most) Microwaveable (some) Dual-ovenable (some) Non-corrodible Physical and thermal shock-resistant Stronger and better flexible barrier than paper Recyclable (some) Plastic Food Packaging Material Disadvantages Permeable to moisture, O2, CO2, ethanol & aromas Lower compressive strength than glass & metal Less heat resistant than glass & metal Potential for interaction with food Some plastics not recyclable Multi-layer plastic packages not recyclable