Induction sealing is the process of bonding

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

materials by

induction heating Induction heating is the process of heating electrically conductive materials, namely metals or semi-conductors, by electromagnetic induction, through heat transfer passing through an induction coil that creates an electromagnetic field within th ...

. This involves controlled heating an electrically conducting object (usually aluminum foil) by

electromagnetic induction Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1831, and James Cle ...

, through heat generated in the object by

eddy current Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnet ...

s. Induction sealing is used in many types of manufacturing. In

packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a c ...

it is used for package fabrication such as forming tubes from flexible materials, attaching plastic closures to package forms, etc. Probably the most common use of induction sealing is ''cap sealing'', a non-contact method of heating an ''inner seal'' to hermetically seal the top of

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...

and

glass Glass is a non- crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenchin ...

containers. This sealing process takes place after the container has been filled and capped.

Sealing process

The closure is supplied to the bottler with an

aluminum foil Aluminium foil (or aluminum foil in North American English; often informally called tin foil) is aluminium prepared in thin metal leaves with a thickness less than ; thinner gauges down to are also commonly used. Standard household foil is typ ...

layer liner already inserted. Although there are various liners to choose from, a typical induction liner is multi-layered. The top layer is a

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distribu ...

pulp that is generally spot-glued to the cap. The next layer is wax that is used to bond a layer of aluminum foil to the pulp. The bottom layer is a polymer film laminated to the foil. After the cap or closure is applied, the container passes under an

induction coil An induction coil or "spark coil" ( archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 ...

, which emits an oscillating

electromagnetic field An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classical ...

. As the container passes under the induction coil (sealing head) the conductive

liner begins to heat due to

s. The heat melts the wax, which is absorbed into the pulp backing and releases the foil from the cap. The polymer film also heats and flows onto the lip of the container. When cooled, the polymer creates a bond with the container resulting in a hermetically sealed product. Neither the container nor its contents are negatively affected, and the heat generated does not harm the contents. It is possible to overheat the foil causing damage to the seal layer and to any protective barriers. This could result in faulty seals, even weeks after the initial sealing process, so proper sizing of the induction sealing is vital to determine the exact system necessary to run a particular product. Sealing can be done with either a hand held unit or on a conveyor system. A more recent development (which suits a small number of applications better) allows for induction sealing to be used to apply a foil seal to a container without the need for a closure. In this case, foil is supplied pre-cut or in a reel. Where supplied in a reel, it is die cut and transferred onto the container neck. When the foil is in place, it is pressed down by the seal head, the induction cycle is activated and the seal is bonded to the container. This process is known as direct application or sometimes "capless" induction sealing.

Reasons that induction sealing may be useful

There are a variety of reasons companies choose to use induction sealing: * Tamper evidence * Leak prevention * Freshness Retention * Protection against package pilferage * Sustainability * Production Speed

Tamper evidence

With the U.S. Food and Drug Administration (FDA) regulations concerning

tamper-resistant Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and ti ...

, pharmaceutical packagers must find ways to comply as outlined in Sec. 450.500 Tamper-Resistant

Packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a c ...

Requirements for Certain over-the-counter (OTC) Human Drug Products (CPG 7132a.17). Induction sealing systems meet or exceed these government regulations. As stated in section 6 of Packaging Systems:

“…6. CONTAINER MOUTH INNER SEALS. Paper, thermal plastic, plastic film, foil, or a combination thereof, is sealed to the mouth of a container (e.g., bottle) under the cap. The seal must be torn or broken to open the container and remove the product. The seal cannot be removed and reapplied without leaving visible evidence of entry. Seals applied by heat induction to plastic containers appear to offer a higher degree of tamper-resistance than those that depend on an adhesive to create the bond…”

Leak prevention/protection

Some shipping companies require liquid chemical products to be sealed prior to shipping to prevent hazardous chemicals from spilling on other shipments.

Freshness

Induction sealing keeps unwanted pollutants from seeping into food products, and may assist in extending

shelf life Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a ...

of certain products.

Pilferage protection

Induction-sealed containers help prevent the product from being broken into by leaving a noticeable residue on plastic containers from the liner itself. Pharmaceutical companies purchase liners that will purposely leave liner film/foil residue on bottles. Food companies that use induction seals do not want the liner residue as it could potentially interfere with the product itself upon dispensing. They, in turn, put a notice on the product that it has been induction-sealed for their protection; letting the consumer know it was sealed upon leaving the factory and they should check for an intact seal before using.

Sustainability

In some applications, induction sealing can be considered to contribute towards sustainability goals by allowing lower bottle weights as the pack relies on the presence of an induction foil seal for its security, rather than a mechanically strong bottle neck and closure.

Induction heating analysis

Some manufacturers have produced devices which can monitor the magnetic field strength present at the induction head (either directly or indirectly via such mechanisms as pick up coils), dynamically predicting the heating effect in the foil. Such devices provide quantifiable data post-weld in a production environment where uniformity - particularly in parameters such as foil peel-off strength, is important. Analysers may be portable or designed to work in conjunction with conveyor belt systems. High speed power analysis techniques (Voltage and Current measurement in near real time) can be used to intercept power delivery from mains to generator or generator to head in order to calculate energy delivered to the foil and the statistical profile of that process. As the thermal capacity of the foil is typically static, such information as true power, apparent power and power factor may be used to predict foil heating with good relevance to final weld parameters and in a dynamic manner. Many other derivative parameters may be calculated for each weld, yielding confidence in a production environment that is notably more difficult to achieve in conduction transfer systems, where analysis, if present is generally post-weld as relatively large thermal mass of heating and conduction elements combined impair rapid temperature change. Inductive heating with quantitative feedback such as that provided by power analysis techniques further allows for the possibility of dynamic adjustments in energy delivery profile to the target. This opens the possibility of feed-forward systems where the induction generator properties are adjusted in near real-time as the heating process proceeds, allowing for a specific heating profile track and subsequent compliance feedback - something that is not generally practical for conduction heating processes.

Benefits of induction vs. conduction sealing

Conduction sealing requires a hard metal plate to make perfect contact with the container being sealed. Conduction sealing systems delay production time because of required system warm-up time. They also have complex temperature sensors and heaters. Unlike conduction sealing systems, induction sealing systems require very little power resources, deliver instant startup time, and have a sealing head which can conform to “out of specification” containers when sealing. Induction sealing also offers advantages when sealing to glass: Using a conduction sealer to seal a simple foil structure to glass gives no tolerance or compressibility to allow for any irregularity in the glass surface finish. With an induction sealer, the contact face can be of a compressible material, ensuring a perfect bond each time

Variety of products that use induction sealing

Pharmaceutical A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...

*Nutraceutical *

Food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is in ...

Dairy A dairy is a business enterprise established for the harvesting or processing (or both) of animal milk – mostly from cows or buffaloes, but also from goats, sheep, horses, or camels – for human consumption. A dairy is typically located on ...

Beverage A drink or beverage is a liquid intended for human consumption. In addition to their basic function of satisfying thirst, drinks play important roles in human culture. Common types of drinks include plain drinking water, milk, juice, smoo ...

Cosmetics Cosmetics are constituted mixtures of chemical compounds derived from either natural sources, or synthetically created ones. Cosmetics have various purposes. Those designed for personal care and skin care can be used to cleanse or protec ...

, health & beauty * Automotive

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

products *Chemical *Agricultural and ag chem. *Animal care and medicines *

Sporting goods Sports equipment, sporting equipment, also called sporting goods, are the tools, materials, apparel, and gear used to compete in a sport and varies depending on the sport. The equipment ranges from balls, nets, and protective gear like helmets. ...

supplies *Children’s toys (clays, bubbles, etc.) *Pastes *

Paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

s *Home remodeling products *Musical instrument supplies (cleaners, resins, lubricants, polishes) *Dental *Personal pleasure products *

Hunting Hunting is the human activity, human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products (fur/hide (skin), hide, ...

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from fish stocking, stocked bodies of water such as fish pond, ponds, canals, park wetlands and reservoirs. ...

aids *

Computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...

aids/ inks *

Laundry detergent Laundry detergent is a type of detergent (cleaning agent) used for cleaning dirty laundry (clothes). Laundry detergent is manufactured in powder (washing powder) and liquid form. While powdered and liquid detergents hold roughly equal share o ...

/products *Manufacturing shop supplies *School supply products *Inks,

dyes A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

, carbon products…. *Condoms

History

*1957-1958 - Original concept and method for Induction Sealing is conceived and proven by Jack Palmer (a process engineer at that time for the FR Corporation - Bronx, NY) as a means of solving liquid leakage from polyethylene bottles during shipment *1960 - is awarded to Jack Palmer, in which his concept and process of Induction Sealing is made public *Mid-1960s - Induction sealing is used worldwide *1973 – First solid state cap sealer introduced *1982 –

Chicago Tylenol murders The Chicago Tylenol murders were a series of poisoning deaths resulting from drug tampering in the Chicago metropolitan area in 1982. The victims had all taken Tylenol-branded acetaminophen capsules that had been laced with potassium cyanide. S ...

*1983 – First

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

ized air-cooled power supply for induction cap sealing *1985 – Universal coil technology debuted *1992 – Water-cooled,

IGBT An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily used as an electronic switch, which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating lay ...

-based sealer introduced *1997 – Waterless cap sealers introduced (half the size and relatively maintenance free) *2004 – 6 kW system introduced

References

External links

FDA’s regulations concerning tamper-resistant packaging
* http://www.enerconind.co.uk/ {{packaging Induction heating Packaging machinery