Security Films

Window films delay and deter thieves from entering buildings and homes through the glazing. It constitutes a barrier to forced entry and after breakage.

It is also used to protect you and your family against cutting and piercing injuries caused by accidental breakage in homes, schools and public buildings.

Thanks to its micro-thin and high technology properties, window film can improve ordinary float glass to perform like a safety glass.

Glass is a versatile material. It is used to allow light and warmth to brighten our buildings and improve the aesthetics. It is even used as part of the structural strength of buildings.

However, it can be a hazard when broken, it’s the weak point for deliberate attack. High performance security film can improve resistance to explosive, bullet or repeated impact attack.

Security glazing

Glazing material that passes a suitable test; there are several tests that can be used for security performance of glazing including:

• EN 356: Glass in building – Security glazing – Testing and classification of resistance against manual attack (steel ball simulated attack)

• Explosion testing: Governments – such as the UK – have developed systems of hazard assessment for glazing resistant to explosive attack

• EN 1063: Glass in building – Security glazing – Testing and classification of resistance against bullet attack

Security Film Specification

For all specification of security films it is essential to obtain professional advice.

The following guidance is intended to help you only as a preliminary source of information for security film specification.

The performance and type of security film required often varies considerably from one project to another.

Manual attack

In order to resist the steel ball attack test, the security film has certain attributes:

• The adhesive must bond strongly to the glass to hold broken glass pieces together – acrylic pressure sensitive adhesive is most commonly used

• The base film used must resist stretching, puncture, and tearing – polyester (PET) film is used for this purpose, which, in addition, has excellent optical properties.

• The security film must be a laminate consisting of two, three or more separate layers or micro-layers of PET film adhered together using acrylic pressure sensitive adhesive.

Explosive attack

Many explosion resistant security films are single ply, but the highest performing films are laminated multi-ply or micro-layered products with similar characteristics as above.

Bullet attack

Depending upon the type of security glazing the security film may be single or may be multi-ply with similar characteristics as above.

All types of safety and security film have a high adhesive bond to the glass. The adhesive retains broken glass fragments and helps to absorb some of the energy of the attack.

Security Glazing Performance Resistance to manual attack EN 356

EN 356 is the recognised test standard for assessing the resistance to manual attack of security glazing. The first part of EN 356 uses a 4.11 kg hardened steel ball; the sample of security glazing is positioned horizontally and the steel ball is dropped vertically onto it.

Five samples of the security glazing must pass the test; the drop height and number of impacts then determine the final EN 356 classification.

The effects of the steel ball dropping from 3 metres onto 4 mm glass + security film; the glass breaks but a barrier remains against forced entry.

The velocity the steel ball strikes the security glazing test piece ranges from about 20 kph to almost 50 kph; the impact energy ranges from 60 Joules to 363 Joules.

These values demonstrate the high resistance the security film + glass must have to the impact from the hardened steel ball.

Remember: the glass used above to demonstrate the effectiveness of security film is ordinary 4 mm float glass, which is not even a safety glass let alone a security glass.

Most security films are designed to reach EN 356 Class P2A, but window film manufacturers are constantly developing the technology of security films. It is possible that EN 356 Class P3A will be reached in the near future with Class P4A following some time later.

Security Film Specification Resistance to manual attack

Specify the EN 356 class you want to achieve with security film on annealed glass, either P1A or P2A.

Security Glazing Performance Resistance to explosions Hazard Ranking

A common method of assessing security film on glass for resistance to explosions is via a hazard ranking assessment. This method was developed by the UK Government in the 1980’s as a result of the terrorist explosions being experienced and it has been adapted by the USA Government in the US General Services Administration (GSA) Standard Test Method for Glazing and Glazing Systems Subject to Airblast Loadings. It is being written into forthcoming EN standards.

Security film, installed with a small edge gap, will upgrade plain float glass to hazard level 2 or hazard level 3, depending upon the type of film used and the glazing construction.

Hazard level 2 may be obtained by using security film with an appropriate edge retention system. An edge retention system is simply an attachment that bonds to both the film and to the frame; it may be a structural silicone, a galvanised and powder coated steel section (e.g. in an L shape, Z shape, etc. as required by the frame), or similar system.

In an explosion, the security film retains broken glass fragments and the edge retention system bonds the film to the frame.

This reduces both the risk of broken glass fragments entering into the building and the hazard level. Typical areas that may be treated with both security film and with an edge retention system are escape routes out of a building, safe assembly areas, personnel offices, and computer suites.

Security Film Specification Resistance to explosions

Usually security film is specified for explosion resistance by thickness and EN 12600 impact resistance because these factors are related to the hazard level achieved.

Security Glazing Performance
Resistance to bullets EN1063

Bullet resistant glass may be improved with security film, but the performance of ordinary glass is unlikely to improve.

Bullet resistant glazing is classed either as NS (No Splintering) or S (Splintering); splintering is where particles of glass break away from the surface of the glass opposite the side where the bullet impacted. Security film will usually upgrade an NS type glass to an S type glass.

The increasing technology used in security films means it is possible that one will be developed that will upgrade a non-bullet resistant glass to a true bullet resistant glass.

However, the current window film technology of upgrading to an S type glass from NS is an advantage, because some S type glass can become scratched over time – if the security film (which has a hard scratch resistant coating) is scratched then it can easily and quickly be replaced without having to replace the complete – and very expensive – bullet resistant glass.