SAFI manufactures its products in a wide range of materials. Depending on the characteristics of the fluid (pressure, temperature, chemical composition) and on the external environment (temperature, UV rays, …), it is important to choose carefully the materials of the valve
The PVC-U (unplasticised) is one of the oldest and the most used plastic materials in the industry and in consumer products. This amorphous thermoplastic does not react to humidity and is dimensionally very stable at room temperature.
This material is the most widely used in the valve industry and plastic piping, thanks to its good chemical behaviour at moderate temperature (0-60°C) and its low cost.
This material, which can be glued and welded, presents however a low shock resistance and cannot withstand UV light, which limits its use in various applications. It is the same for its moderate thermal behaviour and we would rather use PVC-C.
Chlorinated polyvinyl chloride (PVC-C) with its superior density presents a greater range of thermal behaviour (up to approximately 90°C) than PVC-U.
Because of the presence of chlorine in the PVC-C, its use is more and more contested. In this case, it is often replaced by ABS or PP.
Polypropylene (PP) is a thermoplastic partially crystalline, from the polyolefin group. Due to its good mechanical and chemical properties, it is one of the most widely used materials in the plastic valve industry.
There are three main polypropylene families:
. Type 1: PP-H (Homopolymer)
. Type 2: PP-B (Block-copolymer)
. Type 3: PP-R (Random-copolymer)
SAFI’s valves exclusively use Type 1 PP.
The polypropylene presents a good thermal stability from 0°C up to 90°C (particularly compared to PVC-U), as well as a good shock resistance. PP’s non-polarized nature provides a good chemical resistance.
It particularly resists to salts, acids and alkalis and numerous organic solvents. The polypropylene is non-toxic and can be easily welded.
Polyethylene (PE) is a thermoplastic polymer with various crystalline structures which results in a wide range of properties. Polyethylene has a good impact strength (shock resistance), good chemical and UV resistance. This material can be easily welded and used at very low temperatures down to -40°C. On the other hand, its mechanical strength,
lower than the one of polypropylene, decreases rapidly when temperature increases.
There are various applications for polyethylene in which certain types are more or less well suited. SAFI has selected PE-HD in its products. High density polyethylene has a high crystalline structure and offers excellent impact strength, low moisture absorption and a good tensile strength.
This polypropylene contains 20 % of borosilicate glass reinforced of type «C» chemically resistant.
It has a very good mechanical resistance, a good dimensional stability, can be easily machined and it is resistant to temperatures from -10 up to 100°C.
Its resistance to UV is improved by the addition of carbon pigments and UV stabilizers.
This polypropylene contains 20% of carbon fibres.
Thus, its surface resistivity (105 Ω) is significantly reduced compared to standard PP (minimum 1017 Ω), so it can better conduct electricity while keeping its other properties.
It enables a whole range of SAFI valves to comply with zones 1 and 2 ATEX regulation.
PolyVinyliDene fluoride has an excellent chemical and physical resistance. Such as other fluorinated polymers, it supports temperature variations from -20°C up to +120°C, ultra-violets and the most corrosive chemical agents. The PVDF is a homopolymer without additives, non-toxic, has a particularly smooth surface, which avoids the development of micro-organisms.
SAFI has selected a highly crystalline grade of PVDF, with a strong mechanical resistance and an excellent long term stability at high temperature. This grade has particularly good resistance in wet chlorine applications.
The main advantages of PVDF are :
1. High chemical resistance,
2. Temperature range (-20°C up to 120°C),
3. Abrasion resistance,
4. High temperature stability,
5. Welded easily,
6. UV resistance,
7. Smooth finish surface.
EPDM has excellent mechanical characteristics, and excellent resistance to both temperature and ageing. Its chemical resistance is also good, particularly concerning bases and diluted acids.
However, it doesn’t resist mineral oils or hydrocarbons in general.
We offer certain assemblies equipped with food-quality EPDM seals compliant with EU regulation No. 10/2011, issued by the Commission on 14th January 2011, relating to plastic materials and objects likely to be in contact with foodstuffs.
FPM ou FKM
(fluoro elastomer like Viton®)
FPM is prepared by polymerising several fluorinated substances (notably vinylidene fluoride) and offers excellent resistance to both corrosive fluids and high temperatures.
Conversely, its cold resistance is somewhat limited. SAFI has adopted a mixture that is particularly aimed at resisting concentrated acids (fluorine content: 70 %), while retaining its original resistance to mineral oils and hydrocarbons.
FFPM ou FFKM
(perfluoroelastomer like Dynalast® or Kalrez®)
FFPM is based on fluorinated monomers. It delivers outstanding performance in aggressive process environments, such as acids, amines, plasma, ultrapure de-ionized water or strong bases.
It can resist extreme volume swell when exposed to a wide variety of chemicals and solvents, including concentrated nitric acid, sodium hydroxide or ethylene diamine.
PTFE (Poly Tétra Fluoro Ethylène)
FEP (Fluorinated Ethylene Propylene)
SAFI uses PTFE diaphragm and FEP (injectable copolymer equivalent to PTFE) coated seals. The FEP o’ring comprises a silicone elastomer core coated with an FEP seal envelope, offering the chemical resistance of PTFE.
FEP and PTFE are used in the pharmaceutical and foodstuffs industries, due to their physiologically neutral characteristics.