PVC-CChlorinated 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.
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.
PP-EL
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.
PVDF
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.