Glossary

App (Atactic Poly propylene)

Additive based on elastomers perfectly compatible with the bituminous mass. Gives the membranes excellent characteristics of plasticity and resistance to high and low temperatures. Membranes modified with APP thermoplastic polymers are commonly used in many types of structures and in areas with warm climates.

Cold Flexibility

Cold flexibility is surely one of the most important quality characteristics of polymer bitumen membranes. It indicates the lowest temperatures in which a membrane can resist without cracking whilst being bent 180° on an expanding machine with constant sections and a 20mm diameter, at a predetermined bending speed as indicated by norm UNI 8202 part 15. In general SBS membranes have a flexibility of between -20°C and -25°C. Good quality APP membranes have a flexibility of between -10°C and -15°C.

Compound

This is the term which indicates the mix that makes a membrane. The compound is mainly composed of three elements:

bitumen, (produced from oil craking)
Chemical additives (APP or SBS resins)
Mineral filler

Fibreglass reinforcement

This reinforcement is made of fine glass fibres of between 6 and 12 mm in length, with longitudinal reinforcements.

Fully bonded membranes

Fully bonded membranes require the total soldering of the waterproofing membranes to the underlaying support. This kind of application is used on existing coverings or when particular underlaying support movement is not foreseen.

Laying polymer bitumen membranes

Polymer Bitumen membranes are normally soldered to the underlaying support using torching or light propane gas flames; the torching provokes the softening of the inferior membrane and thus permits its adhesion to the support system. In some special cases the membranes can also be glued using specific bitumen glues.

Loose laid membranes

The application of loose laid membranes require the polymer bitumen membrane to only be soldered on its lengthways flaps, side end flaps and on the perimeter parts of the area to be covered. This fact allows the waterproofing system to be independent from the underlying support. Whilst carrying out posa in indipendenza it is necessary to provide a heavy protection system, (gravel or paving) to avoid the possibility that the covering may be lifted up by the wind.

Membranes with metallic self-protection

Membranes with metallic self-protection are made with a bonding process between a membrane and an adequately thick metal laminate (copper or aluminium). When placed on the surface the laminate embosses to compensate any thermal expansion. It is fundamentally important that the polymer bitumen membrane is made with distilled bitumen (not oxidised bitumen) as distilled bitumen has an excellent resistance to high temperatures and thus favours adhesion between the laminate and the membrane over time.

Mineral Membranes

Mineral (or slated) membranes are polymer bitumen membranes with an upper surface covered in a layer of non-igroscopic minerals composed of slate flakes which completely cover the bitumen layer, thus preventing premature ageing.

Overlapping Ends

The overlapping ends are found on self-protecting mineral membranes. They are between 7 and 12cm wide which is left mineral-free in order to create a seal between the adjacent membranes both lengthways and widthways. It is a good idea to pre-calculate this in the planning stage in order to avoid any precarious seal problems that the mineral may create.

Paint

Membrane protection can also be achieved by painting the external covering with the appropriate highly reflective paint, in this case periodical paint layer maintenance is important.

Polyester reinforcement

Non-woven material is made of polyester and is used as a support material for the majority of polymer bitumen membranes. The non-woven material can be:

As a staple, made of polyester thread segments of a length not normally less than 6cm.
As continuous thread (or SPUNBOND) made of continuous polyester thread assembled in a predetermined way.

Primer

Bitumous primer is a mixture of oxidised bitumen and solvents; it is applied to the membrane in order to guarantee that the membrane adheres to the support perfectly.

Protection from UV rays

Polymer bitumen membranes must always be protected from UV rays, so an outer layer must always be applied. The required membranes are self-protected with minerals, metallic laminates or the correct paints

SBS (Styrene-butadiene-styrene)

SBS is an additive with an elastomer base which is perfectly compatible with the bitumen mass. It gives the membrane both excellent flexibility characteristics and resistance characteristics at low temperatures. SBS based membranes are used for very exposed structures or in very severe climates.

Slip layer

The slip layer is usually composed of a layer of non-woven polyester material which allows the flow of the waterproofing layer with respect to the underlaying support without compromising the integration of the cover.

Spot-bonded

Vapour Barriers

This layer is normally made up of a polymer bitumen membrane with an inserted aluminium laminate which prevents vapour passing through. The vapour barrier is always used with particularly fibrous insulating material, in order to prevent the vapour from condensing inside the insulating panel and leading to the degradation of the thermal insulating characteristics.

Polyglass’ glossary

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