Evaluation of the synergistic effect of layered double hydroxides with micro- and nano-CaCO₃ on the thermal stability of polyvinyl chloride composites

Abstract

Synergistic stabilizing effect of layered double hydroxides (LDHs) with micro-as well as nano-sized calcium carbonate (CaCO 3 ) on thermal stability of polyvinyl chloride (PVC) was studied and evaluated. Nano-sized CaCO 3 was prepared in the laboratory by matrix-mediated growth and controlled (in situ deposition) technique. Crystal size of nano-CaCO 3 was estimated by studying x-ray diffraction pattern. The PVC composites were prepared using Brabender Plastograph instrument. Various formulations were prepared by taking fixed amount of LDH and varying the concentration of micro-/nano-sized CaCO 3 . PVC sheets of 1 mm thickness were prepared on compression molding machine. Thermal stability in terms of thermal degradation was studied by thermogravimetric analyzer. Surface morphology and mechanical property were studied using scanning electron microscopy and universal tensile machine. Increase in the onset temperature of the PVC sheets was considered as imparting a better thermal stability to PVC. Better synergistic effect on the stabilization of PVC was observed in case of LDH with nano-sized CaCO 3 and compared with micro-sized CaCO 3.

Principles of Thermal Degradation

“…Braun and Kraemer 356 proposed to use addition of calcium carbonate in PVC recycling. 361 When wood flour is used as a filler, degradation begins at lower temperature 357,359 when the content of wood flour increases but maximum degradation temperature is constant for each tested wood flour content and higher than for control (Figure 4.67). 31,356 Calcium carbonate the nanoparticles were modified with poly(acrylic acid) and poly(butadiene-coacrylonitrile-co-acrylic acid).…”

Principles of Stabilization

“…197 This stabilizer used as single thermal stabilizer enhanced both the long-term and initial thermal stability of PVC. 201 11.3.4 ORGANOTIN STABILIZERS Organotin stabilizers are purely synthetic products; therefore, the major consideration is to use common raw materials, which are the most economically feasible. 200 Synergistic stabilizing effect of layered double hydroxides with nano-sized calcium carbonate on thermal stability of polyvinyl chloride was observed.…”

“…Hydrotalcite, modified zeolite and montmorillonite are effective stabilizers of PVC compositions [195][196][197][198][199][200][201][202][203][204][205]. 11.3.3.1 Properties and applications of commercial stabilizers…”

Unprecedented exploration of ionic liquids as additives which astonishes the thermal stability of PVC formulations

“…Notably, the stabilizing mechanism for PVC accentuates for an irreversible bonding between the stabilizing material and the eliminated HCl; such interactions are responsible for the delayed degradation of the formulations. At present, lead salts, metal soaps and organotin compounds as well as organic heterocyclic motifs are highly exploited for this purpose [4,5], but certain limitations have been advocated to define the scope of these organic and inorganic materials, such as their toxicity, environmental issues related to these metallic pollutants, their efficiency and, of course, their expensiveness. Additionally, the lead salts are found to be toxic and pose severe environmental issues, whereas organotin compounds are very expensive.…”