No abstract

Influence of heat treatment and fillers on the heat distortion temperature (HDT) of poly(lactic acid) hybrid biocomposites was intensively studied through HDT testing, polarizing microscope (POM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). With loading 20 wt % BF or 20 wt % talc, improvement of HDT in PLA composite was about 10 C comparing with neat PLA after heat treatment. Moreover, there was a great improvement (above 45 C) of HDT in PLA composites with loading 20 wt % BF and 20 wt % talc simultaneously after heat treatment. Transcrystallization was observed during heat treatment and isothermal crystallization of PLA composites with loading BF and talc simultaneously. There was no similar phenomenon in other PLA composite with loading only one filler. The possible mechanism of forming transcrystallization was proposed. DSC and DMA were also used to clarify the variation in HDT before and after heat treatment, and the results suggest that the crystallinity, modulus and glass transition changed, especially formation of transcrystallization played a key role in improvement of HDT in PLA composites.

No abstract

This article reports on the relationship between the variation of hydrogen bonding and macroscopic properties of composites composed of hydrogenated nitrile butadiene rubber (HNBR) and 3,9‐bis {1,1‐dimethyl‐2 [β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl) propionyloxy] ethyl}‐2,4,8,10‐tetraoxaspiro [5,5]‐undecane (AO‐80). Hydrogen bonding of the composites was studied by Fourier‐transform infrared (FT‐IR) and ultraviolet (UV) spectroscopies. FT‐IR spectra at room temperature revealed that the stretching vibration peak of OH and CO of AO‐80 red shifted with increasing AO‐80 content, whereas that of C≡N of HNBR blue shifted only when the AO‐80 content exceeded 10 parts per 100 resin (phr). At elevated temperatures, the shift was the opposite for CO and C≡N bands resulting from hydrogen bonding dissociation. In the UV spectra, the E2 band of benzene ring of AO‐80 exhibited two peaks differing in shape. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

In this study, miscibility and dynamic mechanical properties of hydrogenated nitrile butadiene rubber (HNBR) and 3,9‐bis{1,1‐dimethyl‐2‐[β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl) propionyloxy]ethyl}‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) composites were investigated. The composites with low‐AO‐80 content showed the incomplete miscibility, and a part of AO‐80 dissolved into HNBR, while the rest was dispersed into HNBR in the form of deep‐submicron‐sized microspheres based on the micromorphological and thermal analyses. However, with the increasing AO‐80 content, the system became completely miscible. When blending with AO‐80, the resulting composite exhibited the remarkably improved dynamic mechanical property. The loss tangent (tan δ) peak of the composites gradually shifted to room temperature with the increasing AO‐80 content. In this work, two classical equations (Gorden‐Taylor and Fox) were used to predict the glass transition temperature of the HNBR/AO‐80 composites. The calculated value based on Fox equation was more close to the experimental data. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

In this work, a straightforward method of vulcanizing acrylate rubber (AR) was explored via the introduction of in situ coordination crosslinking. An inorganic metal salt, copper sulfate (CuSO 4 ), was mechanically mixed with AR and heat pressed to prepare a novel crosslinkable AR/CuSO 4 composite. The determination of the coordination bonding between the ester groups of AR and copper (II) ions was performed with Fourier transform infrared spectroscopy based on the red shifts of the ester group absorption bands and the disappearance of the coordinated sulfate absorption bands, as well as by electron spin resonance based on the changes in the g-factor of copper (II). The crosslinking procedure of the composite was investigated through dynamic mechanical analysis. In addition, the extent of the crosslinking of the AR/CuSO 4 composites was evaluated by observing the swelling behaviors. Scanning electron microscopy was used to investigate the morphology of the composite. The vulcanizates exhibited improved physical properties with high elongation at break due to exchange reaction between the ester groups of AR and Keywords: acrylate rubber; coordination; polymer composites; vulcanization INTRODUCTION Acrylate rubbers (AR) exhibit the favorable qualities of weatherability, high temperature serviceability and good oil resistance. These qualities make the rubbers useful for under-the-hood automotive applications and outdoor applications. However, because AR is a saturated rubber, it is impossible for it to be vulcanized through traditional sulfur-vulcanizing systems like unsaturated rubbers. A considerable amount of research has been accomplished in the past years to introduce various types of active cure-site monomers into AR chains during the polymerization process. The most common curesite monomers include those containing a labile halogen atom, a carboxyl group, an epoxide moiety, an unsaturated double bond, and a combination of two or more monomers resulting in dual or multiple cure sites, which require different curing systems as shown in Table 1. Despite significant advances in cure technology, all of the current acrylic elastomers require a relatively long cure cycle or must be post-cured.In this work, we aimed to develop a straightforward method to vulcanize AR by introducing coordination-bond crosslinking. Ester carbonyl is capable of coordinating with metal ions, especially in solution systems. Metal complexes with carboxylic esters as ligands have long been in practice. A brief overview of low-molecular-weight organic compound complexes that contain coordinated ester groups was presented by Schreiner et al. 20 Multidentate ligands containing esters and other functional groups have been recently attracting the

Taken together, our data provide a novel evidence for the biological and clinical significance of CHD1L as a potential biomarker, and we demonstrate that CHD1L-Wnt/β-catenin might be a novel pathway involved in pancreatic cancer progression.

No abstract