A New Approach to Prepare Poly(ethylene terephthalate)/Silica Nanocomposites with Increased Molecular Weight and Fully Adjustable Branching or Crosslinking by SSP

Abstract

Summary: In the present study, it has been unexpectedly found that solid‐state polycondensation (SSP) can act as a facile method to prepare poly(ethylene terephthalate)/silica (PET/SiO2) nanocomposites with high molecular weight and an adjustable degree of branching or crosslinking. Fumed silica, with its surface silanol groups, seems to participate in some kind of reaction, probably esterification with the hydroxy end‐groups of PET, during SSP, to act as a multifunctional chain extender. Differential scanning calorimetry and FT‐IR spectroscopy reveal this ability of the silanol groups. The molecular weight increase depends on the used temperatures of SSP as well as on the amount of SiO2 added. As the amount of silica increases the rate of increase of the intrinsic viscosity slows because of the higher extent of branching. At 5 wt.‐% SiO2 the extensive branching produces a crosslinked polymeric material. Such polyesters with increased molecular weight and low silica content could be suitable for blown bottle production, while the high SiO2 content and adjustable branching or crosslinking could make them ideal high‐melt‐strength resins suitable for the preparation of low‐density closed‐shell foams.Schematic representation of PET/SiO2 crosslinked macromolecules.magnified imageSchematic representation of PET/SiO2 crosslinked macromolecules.

Thermal degradation kinetics of PET/SWCNTs nanocomposites prepared by the in situ polymerization

“…As shown in Table 1, the intrinsic viscosity increased at the SWCNTs concentration of 0.1 mass%, and, then, gradually decreased at higher concentrations. The similar effect was also observed in nanocomposites containing SiO 2 , which can also act as multifunctional additives, it was found that in small amounts SiO 2 nanoparticles could act as chain extender, increasing the molecular mass of the polymer, while at higher contents, due to the extended degree of the aforementioned reaction, branched and crosslinked macromolecules are formed, leading to a reduce of molecular mass [39,40]. This may explain the gradual decrease observed in molecular mass of the PET samples with concentrations of SWCNTs nanoparticles greater than 0.1 mass%.…”

Novel poly(butylene succinate) nanocomposites containing strontium hydroxyapatite nanorods with enhanced osteoconductivity for tissue engineering applications

“…Due to these interactions at a low concentration the nanoparticles could act as chain extenders, increasing the molecular weight of the polyester, and thus macromolecules with higher molecular weight than pure polyester were produced, as in the nanocomposite containing 0.5 wt% SrHAp nrds. However, at higher concentrations, due to extended reactions, branched and/or cross-linked macromolecules could be formed, since SrHAp nrds, due to the surface hydroxyl groups, can act as a multifunctional agent, leading to a partial reduction of molecular weight [12], as in nanocomposites containing 1.0 and 2.5 wt% SrHAp nanorods. Branched polymers generally have lower intrinsic viscosities than the corresponding linear ones having the same molecular weight.…”

Nanocomposites of isotactic polypropylene with carbon nanoparticles exhibiting enhanced stiffness, thermal stability and gas barrier properties

“…Most products require a balance between stiffness and impact strength, and this need has been met using several nanoparticles, at loadings of 10% or less, increasing the range of the material's applications [13][14][15]. Although nanocomposites can be prepared either through melt compounding [16][17][18][19][20] solution blending [21], in situ polymerization techniques [22,23] and sol-gel reactions [24], due to its compatibility with current industrial processes, such as extrusion and injection molding, the absence of organic solvents, and its suitability with most commodity polymers, melt-mixing is 4 probably the most industrially feasible and versatile technique amongst the various strategies used for the preparation of nanocomposites.…”