Study of the effect of the chloroallyl group content on the thermal dehydrochlorination of PVC

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.

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N‐substituted maleimides as thermal stabilizers for rigid polyvinylchloride

Sabaa

Mikhael

Mohamed

et al. 1989

Angew. Makromol. Chem.

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Crosslinking of poly(vinyl chloride) with metal oxides, sulfur, and organo sulfur compounds

Běhal

Ducháček

1989

J of Applied Polymer Sci

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SynopsisThe crosslinking of poly(viny1 chloride) in the presence of zinc oxide, magnesium oxide, ethylenethiourea (ETU), tetramethylthiuramdulfide (TMTD), and sulfur at 160 and 180°C has been studied. The effects of ETU and sulfur on the crosslinking of PVC in the presence of TMTD have been individually studied. It has been found that zinc dimethyldithiocarbamate (ZnDMDC) is the actual crosslinking agent and heat stabilizer of PVC, formed in the cured polymer mix. Chemical Structure and Thermal Stability of Poly(viny1 Chloride)The field of investigation of the chemical structure and thermal stability of PVC is at present so wide that we can give here only a short survey of the

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Thermal dehydrochlorination of poly(vinyl chloride), 2. Transiently and permanently acting structural defects

Lukáš

Pr̆ádová

1986

Makromol. Chem.

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Samples with an increased content of chloroallyl structures were prepared by chemical degradation of poly(vinyl chloride) (PVC) using potassium tert‐butoxide. The samples were thermally dehydrochlorinated in an inert atmosphere, and their dehydrochlorination curves were determined by the continuous potentiometric method. The results show that the chloroallyl structures affect the dehydrochlorination of PVC only transiently. The same conclusion is obtained by an analysis of experimental data of the dehydrochlorination of PVC samples enriched in structures with the chlorine atom bound to the branching site (structures with the chlorine atom at the tertiary carbon atom). A general conclusion is that all structural defects, which facilitate the elimination of hydrogen chloride along the polymer chain and exist in the polymer before its heat stress, play only a transient role in the thermal dehydrochlorination of PVC. These structural defects initiate the splitting‐off of hydrogen chloride during the induction period of dehydrochlorination and form conditions for a gradually increasing effect of the basic initiation mechanism, which in the course of dehydrochlorination gives rise to chloroallyl structures. The formation of chloroallyl structures is brought about by a reaction between regular structural PVC units and s‐cis‐enone, dienone, or polyenone structures. A possible mechanism of this reaction, consisting in an interchain syn‐elimination of hydrogen chloride, is suggested.

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Study of the effect of the chloroallyl group content on the thermal dehydrochlorination of PVC

Cited by 10 publications

References 8 publications

N‐substituted maleimides as thermal stabilizers for rigid polyvinylchloride

N‐substituted maleimides as thermal stabilizers for rigid polyvinylchloride

Crosslinking of poly(vinyl chloride) with metal oxides, sulfur, and organo sulfur compounds

Thermal dehydrochlorination of poly(vinyl chloride), 2. Transiently and permanently acting structural defects

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