Brief introduction of PVC-DWV foam core pipes-3

(6) Since the density of the middle foam layer is only 0.7-0.9g/cm3, which is 10%-35% lower than that of ordinary solid wall pipes, the larger the diameter of the pipe, the greater the proportion of the foam core layer to the wall thickness, and the more material is saved. On average, PVC-U core foam drainage pipes with the same wall thickness save about 25% of materials compared with PVC-U solid wall pipes, and the cost per meter is reduced by 32%.

(7) The Vicat softening point of the inner and outer solid wall layers is ≥83℃; the tensile strength is ≥45.5MPa; the elongation at break is ≥92%.

3.  Raw material selection and material formula

The main raw material for PVC core foam tube is suspension PVC resin, but because the fluidity and formability of the inner and outer skin layers and the foam core layer of the core foam tube are different during molding, the grade numbers of PVC resin used is also different. 

Generally, SG5 type PVC resin is used in the material formula of the inner and outer skin layers, and SG7 or SG8 type PVC resin is used in the foam core layer. 

Similarly, in order to meet the needs of the extrusion process, a certain proportion of stabilizers, lubricants and other additives should be added to the formula, and foaming agents must also be added to the material formula of the foam core layer.

3.1 Reference formula based on one-pack Lead stabilizer:

A. Inner/outer layer formula (based on SG-5 resin)

- PVC resin: 100PHR, 

- Heavy calcium:200-250PHR, 

- Lead stabilizer: 4.6-5.6PHR, 

- Stearic acid:1.0-1.8PHR,

- Paraffin: 0.3-0.8PHR

- CPE (Optional): 6-10PHR

B. Foam core layer formula (based on SG-7 resin)

 - PVC resin: 100PHR;

 - Light calcium/heavy calcium (For adjusting density): 50-125PHR

 - Foaming agent:  Appropriate dosage (need to match the extrusion process) 

 - Lead stabilizer: 4.0-5.0PHR

To be continued....