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:
² 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.
² 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.
² 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 |
