GB/T 18742.1-2017Polypropylene (PP) piping systems for hot and cold-water installations -- Part 1: General (English PDF)

3.1 Terms and definitions related to geometric dimensions

3.1.1 Nominal size; DN

It represents the nominal value of a component's size.

[GB/T 19278-2003, Definition 3.4]

3.1.2 Nominal outside diameter; dn

The specified value of the outside diameter of a pipe or fitting socket, in mm.

NOTE. The nominal diameter of fittings that mate with the outside diameter of the pipe is also expressed as the nominal outside diameter of the pipe.

[GB/T 19278-2003, Definition 3.5]

3.1.3 Outside diameter (at any point); de

The outside diameter measured through a cross-section at any point on the pipe, in mm.

3.1.4 Mean outside diameter; dem

The value obtained by dividing the outer circumference of any cross-section of a pipe or fitting socket end by 3.142 (pi) and rounding-off to the nearest 0.1 mm; the unit is in mm.

[GB/T 19278-2003, Definition 3.8]

3.1.5 Mean inside diameter

The arithmetic mean of two or more mutually perpendicular measurements of the inside diameter; the unit is in mm.

[GB/T 19278-2003, Definition 3.11]

Where.

sigmaD - design stress, in MPa;

MRS - minimum required strength, in MPa;

C - Overall service (design) coefficient (3.3.2), a dimensionless value greater than 1 (see 3.3.2).

NOTE. GB/T 19278-2003, 6.11 uses "sigmaS". The design stress code for pipe materials is sigmaDP; and for pipe fitting materials it is sigmaDF.

3.3.4 Polypropylene compound

Granular material conforming to the predicted strength reference curve, produced by extrusion of the base polymer polypropylene (PP) and additives such as antioxidants and colorants.

3.3.5 Pipes with barrier layer

Polypropylene pipes with a very thin barrier layer, for example, used to prevent or reduce the passage of gas and light through the pipe wall, where the design stress requirements are entirely borne by the polypropylene material layer.

NOTE. The maximum thickness of the outer barrier layer (including the adhesive layer) of a typical barrier-layered pipe is 0.4 mm. Pipes with an outer layer thickness exceeding 0.4 mm are called multi- layered pipes (see Bibliography [7] ~ [10]). The outermost layer is often considered to be the first layer of the multi-layered pipe, rather than just a barrier layer.

4.1 Symbols and Codes

C. Overall service (design) coefficient

DN. Nominal size de. Outside diameter (at any point) dem. Mean outside diameter dem, max. Maximum mean outside diameter dem, min. Minimum mean outside diameter

sigmaLPL. Lower confidence limit of the predicted hydrostatic strength

sigmaP. Hydrostatic stress of plastic pipe material

4.2 Abbreviation

PP. Polypropylene

PP-H. Polypropylene homopolymer

PP-B. Polypropylene block copolymer

PP-R. Polypropylene random copolymer

PP-RCT. Polypropylene random copolymer with modified crystallinity

6.1 Polypropylene compounds

6.1.1 Polypropylene compounds for pipes and fittings shall use the following four base resins suitable for pipes.

a) Polypropylene homopolymer (PP-H). A propylene homopolymer.

b) Polypropylene block copolymer (PP-B). A two- or multi-phase propylene copolymer formed from PP-H and/or PP-R with a rubber phase. The rubber phase is composed of a copolymer of propylene and another olefin monomer (or multiple olefin monomers). The olefin monomer has no functional groups other than olefins.

c) Polypropylene random copolymer (PP-R). A random copolymer formed by copolymerizing propylene with another olefin monomer (or multiple olefin monomers);

the olefin monomer having no functional groups other than olefins.

d) Polypropylene random copolymer with modified crystallinity (PP-RCT). Crystallization- improved PP-R.

NOTE 1.For the classification and nomenclature of base resins, see Bibliography [1].

NOTE 2.On the differential scanning calorimeter (DSC) curve, traditional PP-R materials show only one melting peak; while beta-crystalline PP-H and beta-crystalline PP-RCT materials show two melting peaks.

6.1.2 Polypropylene compounds for pipes and fittings shall contain only necessary additives, and the additives shall be uniformly dispersed. Polypropylene compounds for pipes and fittings

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