How to design PVC pipe formula

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

PVC pipe formula includes: PVC resin, impact modifier, stabilizer, processing modifier, filler, color and external lubricant.

1. PVC resin

In order to obtain rapid and uniform plasticization, the suspension method loose resin should be used.

——The resin used for double wall corrugated pipe shall have good molecular weight distribution and impurity quality, so as to reduce the "fish eye" in the pipe and avoid the collapse of pipe corrugations and the rupture of pipe wall.

——The resin used for water supply pipe shall be of "sanitary grade", and the residual vinyl chloride in the resin shall be within LMG / kg. In order to ensure the quality of pipes and reduce the defective rate, the source of resin should be stable.

2. Stabilizer

At present, the main heat stabilizers used are: metal soaps, composite lead salt stabilizers, rare earth composite stabilizers and organotin stabilizers.

Stabilizers containing heavy metals (such as Pb, Ba and CD) are harmful to human health, and the amount of these stabilizers in the water supply pipe formula is limited. In the single screw extrusion process, the heating history of the material is longer than that in the twin-screw extrusion process, and the amount of stabilizer used in the former is more than 25% higher than that in the latter. The head temperature of the double wall corrugated pipe is higher, the material stays in the head for a long time, and the amount of stabilizer in the formula is more than that of the ordinary pipe formula.

3. Filler

The function of the filler is to reduce the cost. Try to use ultra - fine active filler (higher price). The amount of pipe is larger than that of profile Too much filler will reduce the impact resistance and pipe pressure resistance. Therefore, in chemical pipes and water supply pipes, the filler amount is less than 10 parts. The amount of filler in drain pipe and cold bending threading sleeve can be increased, and the amount of CPE can be increased to change the decline of impact performance.

For pipes with low requirements for pipe performance, and downcomers, the amount of filler can be large, but the wear of the twin-screw extruder is serious.

4. Modifier

（1）Processing modifier: ordinary pipes can be used less or not; Bellows and thin-walled pipes are versatile

（2）Impact modifier: less than profile, two reasons: 1. Performance, low temperature resistance, tensile strength 2. Cost

（3）Other additives, colors, etc.: titanium white powder must be added to the profile as an anti - aging agent The formulation of rigid PVC pipe is mainly pigment, mainly titanium dioxide or carbon black, which can be selected according to the appearance requirements of the pipe.

5. Matching of external lubricant and stabilizer

（1）According to the stabilizer, select the matching external lubricant

a. Organotin stabilizer. Organotin stabilizer has good compatibility with PVC resin and has a tendency to adhere to metal walls. The cheapest external lubricant matched with it is the paraffin calcium stearate system based on paraffin.

b. Lead salt stabilizer. The lead salt stabilizer has poor compatibility with PVC resin and is only attached to the surface of PVC particles, hindering the fusion between PVC particles. Usually, lead stearate calcium stearate external lubricant is used to match it.

（2）Amount of external lubricant. If the amount of external lubricant cannot meet the requirements of material processing after adjustment, a small amount of internal lubricant can be added. When the impact toughening modifier is used, because the melt viscosity is large, the possibility of adhering to the metal surface is large, and it is often necessary to increase the amount of external lubricant; The thin-walled pipe extruded by the same equipment needs more external lubricant than the thick-walled pipe of the same specification. When the processing temperature is high, the melt tends to adhere to the metal surface, and more external lubricants are added.

If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.