Xianru He

Crystallization and molecular dynamics of ethylene-vinyl acetate copolymer/butyl rubber blends

In this article, butyl rubber (IIR) was blended with ethylene-vinyl acetate copolymer (EVA) through a molten method. The crystal structure, morphology, crystallization and segmental dynamics were characterized. The crystal structure test indicated that IIR had no influence on the crystal form of EVA. Furthermore, the morphology showed that the blends changed from sea-island to a co-continuous structure. Moreover, the non-isothermal crystallization kinetics given by Mo’s model showed that the rate of crystallization became fast as the content of EVA increased. In addition, the segmental dynamics characterization illustrated that EVA suppressed the molecular motions of IIR to a different degree. Longer units were more influenced than shorter units. It was also found that both crystallization and molecular dynamics had a close relationship with the morphology.

A review of the slow relaxation processes in the glass–rubber transition region of amorphous polymers

This article is a review that introduces several articles about slow relaxation processes, also known as slower segmental dynamics. According to the literature, the coupling effect and free volume holes are two important elements for slower micro-dynamics. In addition, the slower processes of many-body systems (blend and diluted systems) are summarised. A good numerical method for detecting multiple modes in the glass–rubber transition region is introduced.

Influence of graphene/ferriferrous oxide hybrid particles on the properties of nitrile rubber

The reinforcement of rubber by graphene has generated great interest in recent years. The dispersion of graphene in a rubber matrix, however, remains a challenge. In this study, ferroferric oxide (Fe3O4) was used as a carrier to prepare graphene/Fe3O4 hybrid particles, in order to improve the dispersion of graphene in nitrile rubber (NBR). The graphene hybrid particles prepared by co-precipitation synthesis was added into NBR solution to prepare composites. Results show that there was about 90% improvement in tensile strength when 4 phr of graphene hybrid particles (equally only 0.5 phr of graphene in NBR) were added to the matrix. In contrast, the tensile strength of NBR decreased when 4 phr of Fe3O4 were added. SEM and XRD both explained the mechanism for the reinforcement of graphene hybrid particles. The DMA results show higher Tg and a higher value of tanδ for the modified NBR, further proving the reinforcement mechanism, i.e. the hybridization of graphene and Fe3O4 improves the dispersion of graphene in NBR and the interfacial action of graphene with NBR. Moreover, addition of graphene hybrid particles gives NBR extra properties such as surface wettability and magnetism, providing a useful guide for the preparation of functional graphene/rubber composites.

Crystallization Kinetics of Functionalized Fe3O4/Ethylene-vinyl Acetate Copolymer Nanocomposites Adhesives

ABSTRACT In the present paper, the crystallization behaviors of six different functional Fe3O4/ethylene-vinyl acetate (EVA) copolymer nanocomposite adhesives were studied. Crystal structures of the nanocomposite adhesives were characterized by wide-angle X-ray scattering, and the results showed that both functionalized and non-functionalized Fe3O4 nanoparticles had only a small influence on the crystal structure of EVA. The cystallization kinetics was investigated through differential scanning calorimetry. The Ozawa and Mo methods were applied to analyze the crystallization behaviors, and the nucleating effect was estimated through the Dobreva and Gutzow method. Finally, the crystallization energy barrier was studied by the Kissinger method.

Non-Isothermal Crystallization Behaviors of Ethylene Vinyl Acetate Copolymer and Ethylene Vinyl Acetate Copolymer-Graft-Maleic Anhydride

Maleic anhydride (MAH) was melt-grafted on ethylene-vinyl acetate copolymer (EVA) with a grafting degree of 6.3%. Through studying the crystal structure of the resulting EVA-g-MAH, the MAH groups had little influence on crystal structure. According to the Owaza model analysis of the non-isothermal crystallization kinetics of EVA-g-MAH and EVA, the MAH groups had a large blocking effect on crystallization. However, the Mo model showed that the crystallization rate of EVA-g-MAH was slightly faster than EVA. The crystallization activation energy was calculated by the Takhor and Kissinger models, and both results indicated that EVA had a larger effective energy barrier than EVA-g-MAH.

Macromolecular interactions and synergy in xanthan/HPAM aqueous solutions

It is known that the rheological properties of a polymer solution are strongly dependent on the polymer structure, composition, conformation and interactions between the polymer and the solvent. Indeed, the macromolecular interactions change the polymer conformation which can result in an improvement of rheological behavior. Herein, the synergy and interactions between hydrolyzed polyacrylamide (HPAM) and xanthan were explored by rheology experiments and dynamic light scattering. The results indicated that hydrogen bonding interactions occur between the HPAM and xanthan existing in saline solution. It was showed that negative or positive synergistic effects occurred when the proportions of partially hydrolyzed polyacrylamide and xanthan were changed and the maximum positive synergy occurred when the content of xanthan was ca. 80% for the present experimental conditions. In addition, the synergy of mixed solution was markedly influenced by temperature and the HPAM molecular weight and mineralization degree. The two types of synergistic effects tended to recede with increasing shear rate in the rheological experiments. It is noted the calculation of relaxation time (t) for the mixed solutions also demonstrated an interaction between the HPAM and xanthan in aqueous solutions.

Influence of molecular interplay on the HPAM/UR rheological properties in an aqueous solution

Herein, the interaction between partially hydrolyzed polyacrylamide (HPAM) and urea (UR) in an aqueous solution was characterized via differential scanning calorimetry (DSC) and two-dimension correlation spectra (2DCOS). The rheological properties of the HPAM solution (2000 and 2500 mg L−1) were studied as a function of the addition of the UR content (50, 100, 200, 300, and 400 mg L−1). The results indicate that the HPAM/UR solution exhibits higher intrinsic viscosity, apparent viscosity, first normal stress difference, and modulus than the HPAM solution due to the larger hydraulic size of HPAM in the aqueous solution. From the DSC and 2DCOS results, a stronger hydrogen bonding interaction between carbonyl and amino groups was observed in the vicinity of 45 °C. Dynamic light scattering (DLS) was employed to directly analyze the hydrodynamic diameter, and it further confirmed that a certain amount of UR enabled the blending solution to increase the hydraulic size. Moreover, an interplay model was put forward based on the rheology and dynamic light scattering data.

Aging-Resistant Functionalized LDH–SAS/Nitrile-Butadiene Rubber Composites: Preparation and Study of Aging Kinetics/Anti-Aging Mechanism

With the aim of improving the anti-aging properties of nitrile-butadiene rubber (NBR), a functional organic filler, namely LDH–SAS, prepared by intercalating 4-amino-benzenesulfonic acid monosodium salt (SAS) into layered double hydroxides (LDHs) through anion exchange, was added to nitrile-butadiene rubber (NBR), giving the NBR/LDH–SAS composites. Successful preparation of LDH–SAS was confirmed by XRD, TGA and FTIR. LDH–SAS was well dispersed in the NBR matrix, owing to its strong interaction with the nitrile group of NBR. The obtained NBR/LDH–SAS composites exhibited excellent thermo-oxidative aging resistance as shown by TGA-DSC. Further investigation by ATR-FTIR indicated that SAS can capture the radical groups, even during the aging process, which largely accounts for the improved aging resistance.

Damping Analysis of Some Inorganic Particles on Poly(butyl-methacrylate)

Viscoelastic polymers can be used as damping materials to control unexpected vibration and noise through energy dissipation. To investigate the effect of an inorganic filler on damping property, a series of inorganic particles, Ferriferous oxide(Fe3O4), Graphene/Fe3O4(GF), and Fe3O4 of demagnetization(α-Fe2O3) were incorporated into poly(butyl-methacrylate) (PBMA). The effects of the dispersion of particles, as well as the interaction between particles and the PBMA matrix on the damping property of composites, were systematically studied. Results revealed that the addition of three types of particles can effectively improve the damping properties and broaden the effective damping temperature range. Dispersion of α-Fe2O3 in the PBMA matrix is better than that of Fe3O4. As a result, the damping peak can be increased more. The interaction between GF and the PBMA matrix is stronger than that between Fe3O4 and the PBMA. The damping peak of the composites can be suppressed by GF, which is opposite to Fe3O4 and α-Fe2O3. In addition, glass transition temperature (Tg) of all composites in the study shifted to low temperatures.

Mesoporous Titanium Dioxide: Synthesis and Applications in Photocatalysis, Energy and Biology

Mesoporous materials are materials with high surface area and intrinsic porosity, and therefore have attracted great research interest due to these unique structures. Mesoporous titanium dioxide (TiO2) is one of the most widely studied mesoporous materials given its special characters and enormous applications. In this article, we highlight the significant work on mesoporous TiO2 including syntheses and applications, particularly in the field of photocatalysis, energy and biology. Different synthesis methods of mesoporous TiO2—including sol–gel, hydrothermal, solvothermal method, and other template methods—are covered and compared. The applications in photocatalysis, new energy batteries and in biological fields are demonstrated. New research directions and significant challenges of mesoporous TiO2 are also discussed.