Dingsheng Yu

Morphology and mechanical properties of clay/styrene‐butadiene rubber nanocomposites

Based on the character of a clay that could be separated into many 1-nm thickness monolayers, clay styrene-butadiene rubber (SBR) nanocomposites were acquired by mixing the SBR latex with a clay/water dispersion and coagulating the mixture. The structure of the dispersion of clay in the SBR was studied through TEM. The mechanical properties of clay/SBR nanocomposites with different filling amounts of clay were studied. The results showed that the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4–10 nm and its aggregation formed by several or many layer bundles. Compared with the other filler, some mechanical properties of clay/SBR nanocomposites exceeded those of carbon black/SBR composites and they were higher than those of clay/SBR composites produced by directly mixing clay with SBR through regular rubber processing means.

Preparation and characterization of Rubber-Clay nanocomposites

Rubber–clay nanocomposites were prepared by two different methods and characterized with TEM and XRD. The TEM showed clay had been dispersed to one or several layers. The XRD showed that the basal spacing in the clay was increased. It was evident that some macromolecules intercalated to the clay layer galleries. The clay layer could be uniformly dispersed in the rubber matrix on the nanometer level. The mechanical tests showed that the nanocomposites had good mechanical properties. Some properties exceeded those of rubber reinforced with carbon black, so the clay layers could be used as an important reinforcing agent as the carbon black was.

Synthesis and Characterization of a Novel 2-Oxazoline-Benzoxazine Compound with Incorporated Polyhedral Oligomeric Silsesquioxane

A novel 2-oxazoline-benzoxazine compound (POB) was synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR and MS. Simultaneously, octa(aminophenyl)silsesquioxane was also synthesized and incorporated in POB to prepare the nanocomposites. The 1H-NMR spectra of the formulated POB and OAPS solution showed the reaction of 2-oxazoline ring and amino group at room temperature, the reaction mechanism was suggested for the first time, and finally the product containing benzamidine structure was obtained. DMA results showed that little content of OAPS (0.5 wt%) remarkably enhanced the thermal properties of PolyPOB; however, excessive content of OAPS may be impair the thermal properties of the nanocomposite. It is speculated that the introduced OAPS decreased the packing density of PolyPOB, which led to the decreasing of char yield (at 800°C) with the increasing of OAPS contents. The TEM micrographs indicated that 0.5 wt% content of OAPS dispersed homogenously in PolyPOB matrix, while aggregation will occur in the nanocomposites containing 5 wt% OAPS.

Polybenzoxazine-POSS Nanocomposites

Publisher Summary POSS exhibits an intramolecular hybrid structure that can be incorporated into the polymers without further surface treatment. Many kinds of POSS compounds are employed to modify polybenzoxazine resin. The POSS is well dispersed in the poly(BA-a) matrix, the poly(BA-a)-POSS composites exhibit higher glass transition temperatures, better thermal degradation temperature, and higher char yield than pristine polybenzoxazine resin. Great efforts are taken to find facile synthesis routes of POSS compounds to obtain inexpensive, designed POSS structures. On the other hand, many synthesis methods, especially click reaction, which received increasing attention from the field of polymer science, can be employed to prepare novel POSS compounds and POSS containing PBZ resin. These newly reported novel POSS compounds and benzoxazine monomers can be used to prepare PBZ resin with better overall properties. Designed POSS compounds and benzoxazine monomers will definitely lead to a bright future for the study of PBZ-POSS nanocomposites. The concept of utilizing POSS to modify polybenzoxazine resin aimed to obtain high performance PBZ-POSS nanocomposites is an exciting area that is just beginning to be explored. The tailorability and versatility of the POSS compounds make them ideally suited for this purpose. The incorporation of POSS into some polymers has offered the opportunity to develop new types of materials that combine many desirable properties; POSS-containing polymer is still one of the hottest spots in the field of organic–inorganic hybrid materials.

Viscoelastic Properties and Determination of Plateau Modulus for Ziegler‐Natta Catalyzed Ethylene‐Propylene Random Copolymer

The viscoelastic behavior of ethylene‐propylene random copolymer with ultra‐high molecular weight (UHPPR) and broad molecular weight distribution (MWD), produced with Ziegler‐Natta catalyst, was investigated by means of oscillatory rheometry at 180°C, 200°C, and 220°C. The loss modulus (G″) curves of 180°C and 200°C present a pronounced peak at 38.10 rad/s and 84.70 rad/s, respectively, while the peak of G″ curve at 220°C locates beyond 100 rad/s. Compared with UHPPR, G″(ω) curves at 180°C and 200°C for Ziegler‐Natta catalyzed ethylene‐propylene random copolymer (PPR) with conventional molecular weight and broad MWD, did not show a peak at 0.01–100 rad/s, respectively. This fact indicates that high molecular weight is responsible for a peak of G″ curves for UHPPR. On the other hand, the activation energy of crossover relaxation time τ c (ΔH a,c) and terminal relaxation time τm (ΔH a,m) is 57.4 kJ/mol and 57.7 kJ/mol, respectively, and shows the same dependence of temperature, which also gives another evidence of the presence of a peak in the G″(ω) curves at 180°C and 200°C. For UHPPR, the plateau modulus (G N 0) which was determined to be 4.51×105 Pa and 3.67×105 Pa at 180°C and 200°C, respectively, decreases with increasing temperature and is independent of molecular weight and MWD. The entanglement points of each molecular chain for UHPPR are much higher than those for PPR with conventional molecular weight, which is a partial reason why the melt viscosity increases with increase of molecular weight.