N‐substituted maleimides as thermal stabilizers for rigid polyvinylchloride

Abstract

N‐substituted maleimides have been investigated as thermal stabilizers for rigid polyvinylchloride (PVC) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the polymer. The results reveal the higher stabilizing efficiency of these products relative to basic lead carbonate, dibutyl tin maleate, and cadmium‐barium stearate stabilizers commonly used in industry. The induction period (Ts) increases as a function of the positive resonance effect of the substituents (+R). Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the stearate stabilizer. The stabilizer efficiencies are attributed to their radical trapping potency which intervenes with the radical degradation process of PVC, while the good color stability is due to the ability of the stabilizer to interact with the conjugated double bonds formed on the PVC chains as a result of degradation. A mechanism illustrating the stabilizer's action is proposed.

Stabilization of rigid poly(vinyl chloride) by 5,6,7,8‐Tetrahydro‐2‐mercapto‐4‐(p‐methoxyphenyl)‐3‐quinolinecarbonitrile

“…Investigation by U V spectroscopy of the degraded modified polymer (m. 6) showed that the characteristic band (A = 287 nm) of the stabilizer moiety was unchanged. This result means that the stabilizer remained attached to the polymer during the dehydrochlorination process (scheme 1).…”

“…7. The absorbance of each sample was measured at A = 450 nm to provide an indication of the concentration of the polyenes formed as a result of dehydrochlorination.…”

“…Although these classes of stabilizers are quite efficient at the industrial level, the metallic residues from some of these compounds (lead, cadmium, tin) may present serious environmental problems. For this reason, attention has been directed to organic stabilizers (5)(6)(7)(8)(9)(10)(11). The suggested organic compound, TMQC, possesses in its structure a thiol group, which may be able to replace the labile chlorine atoms in the polymeric chains, as well as a nitrile group, which should be able to absorb two molecules of the evolved HC1.…”

Hydrophilic functional copolymers from N‐maleoyl glycine and hydroxymethylacrylamide: Synthesis, characterization, and thermal properties

“…Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been widely used in polymer characterization. 9,10 We also previously reported the thermal behaviors of different polymers containing the maleimide moiety. 11,12 The topics of this article are the synthesis, characterization, and thermal behavior of copolymers of MG and hydroxymethylacrylamide (HMAm) with 25-75 mol % in the feed.…”

Synthesis and characterization of phenacyl methacrylate - acrylonitrile copolymers and determination of monomer reactivity ratios

“…The technique of thermogravimetric analysis (TGA) has been widely used in polymer characterization in thermal stability studies 13…”