Abstract
Despite the advantages of the non-flammable, good performance and low price, poly (vinyl chloride) (PVC) still suffer from poor thermal stability, restricting its melting process and applications. Although addition of some heat stabilizers can be used to improve the low thermal stability, so far, they normally compromise the environmental issues and smoke density of PVC during combustion. In this work, a series of La doping Mg-Al layered double hydroxides (LaLDHs) with different molar ratio of La3+ / Al3+ were successfully synthesized by coprecipitation-hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), Scanning Electron Microscopy (SEM) and Transmission electron microscopy (TEM). The results showed that the as-prepared LaLDHs exhibit plate-like morphology with a lateral size around 100-180 nm. The different as-prepared LaLDHs were introduced into PVC as heat stabilizer to prepare PVC nanocomposites. The thermal stability and smoke suppression of PVC nanocomposites were investigated by TGA, thermal aging, Congo red and smoke density rating test (SDR), respectively. All the results demonstrated that PVC-LaLDHs2 nanocomposites containing 2% LaLDHs2 (the molar ratio of La3+ / Al3+ is 1 / 3) were optimized, which achieved the maximal T50% value of 337.2 oC, minimal SDR value of 45.6%, and prolonged the thermal aging time from less than 10mins to 90mins, respectively thermal stability time from 1242s to 2751s. In addition, the tensile strength and elastic modulus of PVC-LaLDHs2 respectively increased by 84.4% (56.6 MPa) and 75.5% (1019.4 MPa) with little affecting elongation at break of PVC. LDHs (layered double hydroxides); rare earth ions; thermal stability; smoke suppression; poly (vinyl chloride)
Highlights
(vinyl chloride) (PVC) is one of the five biggest general thermoplastics and widely applied in various fields such as construction, chemical, decoration, packaging, and cable industry for its desirable physicochemical properties, easy acceptance and workability [1,2,3,4]
The diffraction peaks at 15.5o, 27.3o, 28.1o, 29.5o, 39.4o, 48.6o and 56.4o of the La doping Mg-Al layered double hydroxides (LaLDHs) are attributed to the characteristic peaks of La(OH)3, implying that LaLDHs with different La3+ / Al3+ molar ratio are successfully synthesized and result in different crystalline structures with Mg-Al Layered double hydroxides (LDHs)
The intensity of Metal-O peaks of LaLDHs is weaker than that of Mg-Al LDHs (Figure 1b a), indicating that the lattice structure of Mg-Al LDHs is partially replaced by La3+
Summary
(vinyl chloride) (PVC) is one of the five biggest general thermoplastics and widely applied in various fields such as construction, chemical, decoration, packaging, and cable industry for its desirable physicochemical properties, easy acceptance and workability [1,2,3,4]. PVC, under the influence of heat source and energy radiation, suffers autocatalytic dehydrochlorination reactions and initial reactions of dehydrochlorination, further accelerating the decomposition of the polymer, even resulting in great black smoke and toxic gases during combustion, PVC is well known self-extinguishing polymer [6]. To overcome these limitations, addition of heat stabilizer during the processing is a key factor to improve the thermal stability of PVC. As a high-efficiency, non-toxicity, and synergetic effect with other heat stabilizers, Rare-earth stabilizer attracts increasing attention and share fascinating prospect [9, 10]
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