Heat stabilizers for poly (vinyl chloride). I. Synergistic systems based on calcium/zinc stearate

Abstract

Synergism in poly(vinyl chloride) stabilization was studied by the determination of the dynamic and static stability of 34 different formulations. Nine ratios of Ca/Zn stearate were tested. Both the static and the dynamic stability increased almost linearly with the calcium stearate content, but unfortunately the initial discoloration increased as well. Melt viscosity decreased with an increasing content of calcium stearate. This was mainly caused by the difference in lubrication effect between calcium stearate and zinc stearate. Several co‐stabilizers (synergists) for the Ca/Zn system were also evaluated. Among these, polyols were found to be the most effective. The addition of Polyol T 34, which was prepared through a coprecipitation of trimethylol propane and pentaerythritol, resulted in excellent initial color and improved transparency. Trimethylol propane and di‐trimethylol propane were also powerful in this respect. The best static stability was observed for compounds containing mannitol and sorbitol, although these formulations were slightly discolored. Pentaerythritol and di‐pentaerythritol were very effective in extending the static stability, but they were not useful for the improvement of initial color. Well‐known complexing agents like EDTA and dimethylglyoxime were surprisingly ineffective as synergists. The addition of tris(nonylphenyl) phosphite resulted in a somewhat higher thermal stability, but not in any significant color improvement.

The effect of (natural) polyols on the initial colour of heavy metal- and zinc-free poly(vinyl chloride)

“…In these heavy metal-stabilised PVC formulations, however, the polyol additive still appears to exert a detrimental effect on the initial colour [5,7]. Since natural polyols may significantly contribute to the development of environmentally benign (next generation) stabiliser systems, we have investigated their effect on the initial colour of a heavy metal-and zinc-free PVC formulation.…”

“…To inhibit discolouration during long-term heat exposure (natural) polyols are already applied as secondary heat stabilisers in heavy metal-stabilised PVC compounds [1e7]. Unfortunately, however, in these PVC formulations the polyol additives exert a detrimental effect on the initial colour [5,7]. We recently reported that for heavy metal-and zinc-free PVC formulations (natural) polyols, especially those containing primary hydroxyl groups, act as HCl scavengers by substitution of the primary hydroxyl moieties by chloride ions [8].…”

Effects of epoxidized sunflower oil on the mechanical and dynamical analysis of the plasticized poly(vinyl chloride)

“…The epoxy group of the plasticizer is excellent hydrochloric acid scavenger; hydrochloric acid absorption occurs readily. [18][19][20] The formation of polyene sequences was investigated by UV-visible spectroscopy. The influence of the weight of the epoxidized oil and the amount of oxirane oxygen in the ESO were considered.…”

Effect of Di(2‐ethyl hexyl phthalate)/Epoxidized Soybean Oil and Calcium Stearate/Zinc Stearate Ratios on the Tensile Properties of Plasticized PVC Formulations. A Study for Calcium Stearate Rich Formulations

“…[22] b) Modification of molecular weight distribution, which is produced by the chain scission reactions [3,5,11] (which produce a decrement in E and s, and an increment of e [23]) and the chain branching reactions (which produce the opposite effect [23] ) occurring simultaneously during the heating process. c) Decrease of the magnitude of intermolecular interactions, due to a decrement in the global polarity of the system, which occurred as a consequence of the elimination of many C-Cl polar bonds; this produces a softening of the material.…”

“…[8,[10][11][12] Besides, Thomas [12] suggested that ZnCl 2 formation is prevented, when enough calcium stearate (CaSt 2 ) is present in the system. It has also been reported that mixtures of CaSt 2 and ZnSt 2 are able to form a complex through heating.…”