Yanqin Shi

Effect of allantoin on the stabilization efficiency of Ca–Zn thermal stabilizers for poly(vinyl chloride)

The influence of allantoin (ALL) combined with zinc stearate (ZnSt2), calcium stearate (CaSt2), and ZnSt2–CaSt2 (1:1), respectively, in different mass ratios on thermal stability of poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, and thermogravimetric analysis. The results indicated that ALL behaved as a good long-term thermal stabilizer for PVC, which was attributed to its ability to absorb hydrogen chloride released from the degradation of PVC. Moreover, ALL was able to extend the stabilization time of PVC containing ZnSt2–CaSt2 and postpone “zinc burning.” Fourier transform infrared spectra confirmed that ALL can react with ZnCl2 to produce an inert complex, which is responsible for postponing “zinc burning.”

Novel organic antibacterial thermal stabilizers for transparent poly(vinyl chloride)

A novel kind of antibacterial thermal stabilizers for transparent poly(vinyl chloride), bis-uracil compounds with different alkyl chain length, was synthesized by the condensation of 6-amino-1,3-dimethyluracil with aliphatic aldehydes and characterized with 1H NMR spectra. Not only high stabilization efficiency which increased with the increasing of alkyl chain length was obtained to prevent PVC from degradation, special antibacterial properties could also be acquired in the mean time of keeping PVC highly transparent. The results of discoloration test, thermogravimetric analysis, Fourier transform infrared spectra, visible spectroscopy and scanning electron microscopy revealed that the bis-uracil compounds could absorb HCl through acid–base reaction and chemical bonding, and the amine group played a key role in reacting with the inherent structural defects in PVC chains, meanwhile the long alkyl chain of the bis-uracil compounds could reduce their melting points and improve the compatibility with PVC. Comparing with the referential films stabilized by 6-amino-1,3-dimethyluracil and Ca/Zn stabilizers, PVC films stabilized with bis-uracil compounds had excellent transparency. In addition, the measurement of antimicrobial activity suggested that the bis-uracil compounds had the biological activity to inhibit growth of bacteria. We believe that PVC stabilized by such multifunctional stabilizers may widen its applications in biomedical field.

Highly efficient and antibacterial zinc norfloxacin thermal stabilizer for poly(vinyl chloride)

A novel kind of highly efficient and antibacterial thermal stabilizer, zinc norfloxacin (Zn(C16H17FN3O3)2·4H2O, represented as ZnNo2), for poly(vinyl chloride) (PVC) was first reported in this paper; the structure of which was characterized by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and laser particle size analysis. ZnNo2 extended the thermal stability of PVC and had good synergetic effects with calcium stearate (CaSt2) on decreasing the releasing rate of HCl from PVC, which were confirmed by the results of thermal stability research including the Congo red test, discoloration, dehydrochlorination test and visible spectroscopy. The thermal stability mechanism of ZnNo2 and CaSt2 on PVC was proposed in this paper. The best auxiliary thermal stabilizer was the compound of dibenzoylmethane (DBM), pentaerythritol (PET) and triphenylphosphate (TPP) for ZnNo2/CaSt2 with both acceptable initial color and long-term stability for PVC products. Importantly, the inhibition zone test showed that ZnNo2 had good antibacterial activity against Escherichia coli and Staphylococcus aureus, even in PVC with low concentrations.

Topological structure influences on the gel formation process and mechanical properties of L-lysine based supramolecular gels

The influence of a minor modification of the topological structure of a gelator’s core on the mechanism of the gel formation process and the resultant gel properties were researched by comparing the gelation ability of three L-lysine based gelators with the same arm structures and totally different topological core structures, one of which has a cubic topological polyhedral oligomeric silsesquioxane (POSS) core, one has a regular tetrahedron topological pentaerythritol core and the other has an organic linear topological dodecane core (denoted as POSS-Lys, PER-Lys and C12-Lys). Gelation tests, DSC, rheology measurements, SEM and POM investigations indicate that the gel obtained from C12-Lys with an organic linear topological dodecane core in the same solvent has a much greater strength of hydrogen bonding formed between the gelator molecules and much higher mechanical strength. What is more, POSS-Lys with a cubic topological core has a rather strong recovery ability, while PER-Lys cannot form a gel in any of the solvents tested. The key effect of such an obvious difference is in the self-assembly mechanisms which are influenced by the topological structure of the gelators.

High transparency and toughness PMMA nanocomposites toughened by self-assembled 3D loofah-like gel networks: fabrication, mechanism, and insight into the in situ polymerization process

Novel types of transparent PMMA composites were toughened with 3D loofah-like gel networks obtained via the in situ polymerization of methyl methacrylate (MMA) gel with POSS-based supramolecular POSS-Lys(BOC) gelators that have excellent compatibility with the polymerized matrix for the nanoscale nature of supramolecular gel fibers. The “gel networks-energy dissipation” toughening mechanism was investigated using SEM, tensile testing and DMA, the results of which demonstrate that a favorable architecture formed by the gel nanofibres through hydrogen bonding interactions contributes to the toughness improvement in these nanocomposites. In particular, UV-Vis spectrometry and haze meter tests indicate that the PMMA nanocomposites maintain the advantage of good optical transparency. In addition, the physical self-assembly nature of the gel networks allows them to be easily extracted from the polymer matrix, the result of which clearly demonstrates the framework formed by the nanofibres has not only been retained during the in situ polymerization process, but also has an outstanding capacity for the dissipation of energy. As a result, a special type of nanoporous materials with stable pore shapes was obtained, which has potential applications in optical sensors, energy storage and as a Li-ion battery separator.

Room temperature optical image storage devices based on novel photo-responsive chiral azobenzene liquid crystal dopants

A room temperature optical image storage device based on a novel kind of chiral azobenzene liquid crystal compound (Azo-CC) dopant was reported in this paper, which could realize room temperature photocatalytic phase transition when doping in host liquid crystal E7. With a comparation of the referential achiral compound (Azo-ACC), the chemical structure, liquid crystalline and photoresponsive properties of the compounds were characterized by 1H-NMR, POM and UV–vis, respectively. The result showed that the compound with chiral group (Azo-CC) exhibited better photoresponsive properties than the referential achiral compound (Azo-ACC), indicating the introduction of chiral group is the key factor to provide E7 host room temperature photosensitive properties, which could not only made the liquid crystal molecular reoriented but also could change the whole nematic host liquid crystal to helical-twisted matrix. In addition, to understand the optical-switching behavior into detail, the photoisomerization dynamics of the systems o was also analyzed.

Mechanical Properties and Tensile Deformation Behavior of Polyamide 6/Maleated and Unmaleated Ethylene Propylene Diene Terpolymer/Nano-CaCO3 Ternary Composites

Ternary composites composed of polyamide 6 (PA6), a mixture of maleated (EPDM-g-MA) with unmaleated ethylene propylene diene terpolymer (EPDM) rubber at weight ratio 80/20 (defined as EPDM-M), and nano-calcium carbonate (nano-CaCO3) were prepared by a two-step compounding route. Sandbag microstructure, in which nano-CaCO3 agglomerates were embedded EPDM-M, were observed by scanning electron microscopy (SEM). Deformation of the composites was studied by video-aided tensile tests during uniaxial tension. The microstructural morphology and interfacial interaction were investigated through SEM and dynamic mechanical analysis (DMA). Compared to PA6/EPDM-M/nano-CaCO3 ternary composites without sandbag microstructure (E2), the microstructural morphology of PA6/EPDM-M/nano-CaCO3 ternary composites with sandbag microstructure (E3) showed that numerous microfibrils and cavitations were formed by simultaneously stretching and debonding of nano-CaCO3 agglomerates and EPDM-M in the sandbag microstructure, which resulted in a higher volume strain and larger quantity of energy dissipation. Additionally, better interfacial interaction between the sandbag microstructure and PA6 matrix in E3 caused a lower α-relaxation temperature and easier external energy transmission than E2 without sandbag microstructure. Consequently, the presence of the sandbag particles in PA6/EPDM-M/nano-CaCO3 ternary composites changed the tensile yield deformation of PA6 from a more deviatoric plasticity to a more dilatational plasticity.