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PVC Stabilizer


n  Factors affecting optimum stabilizer selection

The factors to consider in making an optimum stabilizer selection for a given vinyl process can be divided into three broad categories:

√ Formulation variables 

Such as PVC resin, impact modifier, processing aids, plasticizers, fillers, pigments, lubricants, foaming agents, and other miscellaneous ingredients can all have an effect upon or be affected by the stabilizer.

√ Process Variables

which can be a determinant in stabilizer selection include consideration of compounding procedures (Banbury, Dryblend, Plastisol Mixing), calendering, extrusion (single or twin screw), injection molding, blow molding, foamed vinyls ,and so on. Other considerations of processing include melt rheology, plastisol viscosity properties, plate-out, scrap re-work, etc.

√ End Use Properties 

that affect stabilizer selection include clarity, outdoor weathering, toxicity, stain resistance, impact strength, heat distortion, electrical properties, odor, effects of moisture, heat-sealing and printability, and “fogging” (automotive and food wrap film).

 

n  Ca-Zn based stabilizers

Ca-Zn based stabilizers are widely used in many flexible and rigid PVC applications. This type of stabilizing system can give products which have a high degree of clarity, good mechanical and electrical properties, excellent organoleptic properties and good outdoor weatherability. 

Ca-Zn based stabilizer systems have low toxicity or are regarded as non-toxic. There are no risks to human health or the environment arising from the use of zinc stearate in PVC heat stabilizers.


Tab.1 the selection guide of Wellstab™ Ca-Zn stabilizer

Grade

Appearance

Recommended

Dosage(PHR)

Product Features

Application



CZ505S

White-yellow powder

2.6-3.2

Endowing PVC products with excellent initial hue, better processibility

PVC water supply pipe


CZ505D

White-yellow powder

3.0-3.5

Endowing PVC products with excellent initial hue, better processibility

PVC drainage pipe


CZ506

White-yellow powder

4.0-5.0

Superior stability, Endowing PVC products with excellent initial hue, and processibility

PVC water supply fitting and drainage fitting


CZ507W

White-yellow powder

4.0-5.0

Good stability and weatherability, better processibility

PVC window profile


CZ507E

White-yellow powder

4.0-5.0

Endowing PVC products with excellent initial hue, better processibility

PVC edge banding


CZ508

White-yellow powder

3.0-3.5

Superior processibility

PVC foam board



n  Pb-based stabilizers

Pb-based stabilizers do not decrease the mechanical properties of PVC and they exhibit low extraction values when incorporated in the PVC matrix. Therefore, Pb-based stabilizers are used to produce articles requiring good mechanical properties, e.g., high impact strength, high heat distortion temperatures, and no migration, such as pressure pipes, sewage pipes, drainage pipes, electrical conduit, gutters, sheets, boards, profiles for indoor and outdoor applications, and, especially, building profiles.


Tab.2 the selection guide of Wellstab™ Pb-based stabilizer

Grade

Appearance

Recommended

Dosage(PHR)

Product Features

Application



SP-102H

Powder/flake

4.0-5.0

Content of Lead Oxide: 40±1.5%;

Melting Temperature: 94-100°C

PVC profiles.


SP-202F

Powder/flake

3.0-5.0

Content of Lead Oxide: 35±1.5%;

Melting Temperature: 94-100°C

PVC boards


SP-802C8

Powder/flake

3.0-5.0

Content of Lead Oxide: 29±1.5%;

Melting Temperature: 94-100°C

PVC pipes