Safety requirements and special polypropylene grades

Maximum safety requirements
Polypropylene is a thermoplastic material of the polyolefins group. These polymers have been in successful use for production of piping systems for decades. Polypropylene is also used, and is subject to high safety standards, in the automotive industry and in tank farms. Its hygienic safety, resistance to corrosion and good workability, along with many other aspects, provide the basis for a broad range of applications. 
Its physiological safety makes polypropylene an optimum material for drinking-water piping and for other applications subject to food-law regulations.

Special PP grades
The numerous specific requirements in chemical piping-system and processing equipment engineering have led to the development of special low-flammability and electrically conductive grades. The flow of liquids or particulates can, for example, result in static charging during operation of thermoplastic piping systems. This was the reason for the development of electrically conductive grades of polypropylene, to permit earthing (grounding) of such systems. The modified properties are achieved by the inclusion of certain additives. This, however, causes changes in mechanical, thermal and chemical properties vis-?-vis the standard grade. It is therefore vital to check and clarify all projects with the Technical Service department.

Differences vis-a-vis standard PP grades

PP-R, black:
(Polypropylene Random Copolymerisate, black coloration)
The essential benefit of this black-coloured material grade can be found in its UV resistance, which is not a characteristic of grey PP. A slight loss of impact toughness does occur, however.

PP-R, natural:
(Polypropylene Random Copolymerisate, natural) 
PP-R natural contains no colorant additives and is used, in particular, for ultra-pure-water piping systems. This material is not UV-resistant, however.

Polypropylenes with enhanced stiffness (PP-HM, modulus of elasticity > 1700 N/mm2) are part of the Polypropylene Block Copolymerisate (PP-B) class of materials and are notable for their comparatively high modulus of elasticity combined with a high notched impact strength up to 20? C. These characteristics make PP-HM the ideal material for non-pressurized waste-water systems. A further benefit is apparent, for example, upon comparison of PP-HM and PVC-U: Here, the low density of the PP-HM materials (around 0.9 g/cm3) results in the SN 8 ring-stiffness class in approx. 25 % lower per meter weights. 

(Polypropylene homopolymerisate, low flammability) 
PP-H-S is suitable, due to its greater stiffness, for ventilation and waste-gas pipelines, in particular. It is not suitable without additional protective provisions for outdoor use, due to its lack of UV stabilization.

(Polypropylene Random Copolymerisate, low-flammability, electrically conductive)
This material combines the positive properties of the low-flammability and electrically conductive PP grades. It is therefore used, for safety reasons, for conveyance, in particular, of readily flammable media. Reduced impact toughness and creep strength, and also a slightly modified resistance to chemicals, must be taken into account in design.

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