Melt characteristics,mechanical, and thermal properties of blown film from modified blends of poly(butylene adipate‐co‐terephthalate) and poly(lactide)

Blown films from poly(butylene adipate‐co‐terephthalate) and poly(lactide) (PLA) blends were investigated. The blends were prepared in a twin‐screw extruder, in the presence of small amounts of dicumyl peroxide (DCP). The influence of DCP concentration on film blowing, rheological, mechanical, and thermal properties of the blends is reported in this article. Rheological results showed a marked increase in polymer melt strength and elasticity with the addition of DCP. As a consequence, the film homogeneity and the stability of the bubble were improved. The modified blend films, compared with the unmodified blend, showed an improvement in tensile strength and modulus with a slight loss in elongation. Fourier transform infrared and gel results revealed that chain scission and branching were more significant than crosslinking when the DCP loadings in the blends were not higher than 0.7%. A reduction in melt temperatures of PLA was observed due to difficulty in chain crystallization. The concentrations of DCP strongly affected the melting temperatures but had an insignificant effect on the decomposition behavior of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cotton fibers reinforcement of HNBR: Control of fiber alignment and its influence on properties of HNBR vulcanizates

This article focuses on the reinforcement of hydrogenated acrylonitrile butadiene rubber (HNBR) by cotton fiber as natural reinforcing filler. The effect of fiber alignment on the properties of HNBR compounds and vulcanizates is investigated. Properties of interest include rheological behavior, cure, tensile, abrasion, and dynamic mechanical properties which are correlated to the magnitudes of state‐of‐mix, bound rubber content, crosslink density and fiber alignment. Results obtained reveal that mechanical properties of rubber composites are improved dramatically by the addition of cotton fiber due to the enhanced hydrodynamic effect in association with crosslink density. Furthermore, the degree of fiber alignment is found to depend strongly on shear strain. The results demonstrate the importance of fiber alignment controlled efficiently by shear strain. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41090.     

Properties of tire tread compounds based on functionalized styrene butadiene rubber and functionalized natural rubber

Tire tread compounds based on various rubber types, that is, solution styrene-butadiene rubber (SSBR), functionalized (propylamine and dimethoxysilane) solution styrene-butadiene rubber (F-SSBR), natural rubber (NR), chloroacetate-modified natural rubber (CNR), and their blends, were prepared and used as raw rubbers. Properties of tire tread compounds and tire performance were then investigated. Due to the presence of chloroacetate group on its mainchains, CNR demonstrates increases in glass transition temperature and rubber-filler interaction compared to NR leading to a significant improvement in tire performance, particularly wet grip (WG; ~88%), fuel-saving efficiency (FSE; ~15%), and abrasion resistance (~11%). Similarly, F-SSBR shows a greater tire performance than SSBR (~20, ~13, and ~7% improvements in WG, FSE, and abrasion resistance, respectively). Among the rubber blends, F-SSBR/CNR gives the highest tire performance, followed by F-SSBR/NR, SSBR/CNR, and SSBR/NR, respectively. The results suggest the significant enhancement in properties of tire tread compounds by the presence of active functional groups in NR and SSBR molecules. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48696.     

Reprocessable silane-crosslinked polyethylene: property and utilization as toughness enhancer for high-density polyethylene

Silane-crosslinked polyethylene (Si-XLPE) has been increasingly used as a replacement of polyvinyl chloride for use as residence water pipes and hydronic heating systems. Unfortunately, good management of Si-XLPE wastes originated in the manufacturing processes or from already used products is limited. This article presents a melt-recycling (remelting and remolding) of waste Si-XLPE and its use to produce the high-density polyethylene (HDPE) composition of improved thermal endurance, along with attractive balance of stiffness and toughness. Experiments were carried out with a series of Si-XLPE of different gel fraction and crosslink structure, either loose or tight, aiming at understanding the factors which dictate the reprocessability and properties of crosslinked waste. Tensile and impact properties, crystallization, and heat stability of the HDPE and waste blends were investigated. It is found that waste Si-XLPE materials of loosely network structure can be remelting and remolding as thermoplastic PE. Interestingly, the results showed that crosslink gel in the wastes could be as high as 70 %. Both tensile modulus and impact strength of the HDPE systematically increased with increasing loading and content of gel in the crosslinked materials. The addition of 50 % crosslinked waste led to a rise of heat distortion temperature of HDPE by 20 °C, without evitable change in the melting and crystallization temperatures.     

Viscoelastic properties of fly ash‐filled natural rubber compounds: Effect of fly ash loading

Fly ash (FA) as a by‐product of power station plants is known to consist of silicon dioxide similar to precipitated silica. The use of FA as filler in natural rubber (NR) was of interest to reinforce and/or reduce product cost. In this article, viscoelastic properties of FA‐filled NR composites with various FA loadings were investigated with the utilization of two different modes of shear flow, namely, oscillatory and steady shear flow. It is found that the addition of FA to NR increases storage modulus (G′) and shear viscosity under both oscillatory and steady shear flow. Moreover, the oscillatory test results exhibit the unexpected increase in magnitude of viscous response with increasing FA loading in FA‐filled NR compounds. The explanation is proposed in terms of the ball‐bearing effect of FA with spherical shape associated with the occurrence of molecular degradation induced by inorganic constituents particularly manganese, iron, and copper in nonrubber component of NR as well as the small amount of heavy metals including iron, copper in FA. An isoprene rubber (IR) containing no nonrubber component was used to validate the proposed explanation. In addition, with the use of Cox‐Merz concept, the results of both complex viscosity under oscillatory shear flow and apparent shear viscosity under steady shear flow can effectively be superimposed in the case of FA‐filled compounds, supporting the promotion of viscous response by FA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Assessment of crosslink network and network defects of unfilled and filled ethylene‐propylene‐diene terpolymer using solid state nuclear magnetic relaxation spectroscopy

Reinforced rubbers are complex compared to unfilled systems. There are differences in the mechanisms affecting network molecular structure as well as properties of the rubber materials. In this article investigation of crosslink network and untied network defects on a molecular level of unfilled and carbon black filled ethylene‐propylene‐diene terpolymer was carried out using proton solid‐state double‐quantum NMR spectroscopy. The results show that the filled system demonstrates lower cure efficiency in conjunction with more noncoupled network defects than the unfilled one. In addition, the filled system yields the greater spatial heterogeneity because of the localization of the free radicals at the rubber–filler boundary. These strongly influence the mechanical properties of the filled rubber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44224.     

Changes in morphology and properties by grafting reaction in PP/EOR/CaCO3 ternary composites

The phase morphology and mechanical properties of polypropylene (PP) composites containing ethylene–octene elastomer (EOR) and calcium carbonate (CaCO₃) filler were investigated by comparing the toughening effect of unmodified EOR with EOR grafted with maleic anhydride (EOR–MA). EORs of various MA contents were prepared by free‐radical grafting of MA onto the EOR backbone using a reactive extrusion process. The composite morphology was directly explored by scanning electron microscopy technique and indirectly explored by differential scanning calorimetry and dynamic mechanical analysis. Separate dispersion of the elastomer and filler particles was achieved by using unmodified EOR. Modification of EOR by maleic anhydride grafting resulted in encapsulation of the filler particles. The mechanical properties of the composites were found to depend mainly on composite morphology and composition and, to a lesser degree, on maleic anhydride concentration. The results of this study showed that when composites contained an equal or higher amount of elastomer relative to filler, a composite with a separate dispersion structure was preferred. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3557–3562, 2003     

Establishment and characterization of cell lines from liver fluke-associated cholangiocarcinoma induced in a hamster model

Cholangiocarcinoma (CCA) is a relatively rare tumor that occurs primarily in tropical countries and particularly in those with a high incidence of liver fluke infection. A hamster model for a liver fluke-associated CCA has been described previously. In the present study, hamster cholangiocarcinoma cell lines were established and characterized in order to obtain information regarding diagnostically useful tumor marker which could shed light for a future investigation for human cholangiocarcinoma. Two related cell lines, one from the original intrahepatic bile duct tumor and one from an allotransplanted tumor, were established. The established cell lines were found to have population doubling times of 31 and 26 hours respectively, and were maintained in Ham's F12 medium supplemented with 10% fetal bovine serum for over 80 passages. The cell monolayers were subjected to scanning and transmission electron microscopic study and found to have ultrastructural characteristics, including cytoplasmic lumens, consistent with those of adenocarcinoma cells of epithelial origin. An immunoperoxidase study using monoclonal antibodies (MAbs) specific for tumor antigens showed the cytoplasm and membrane of both cell lines to be positive. These antigens were also secreted in soluble form into the culture medium, judging from polyacrylamide gel electrophoresis in the presence of SDS and from immunoblot analyses. Different lines of evidence presented suggested that a 200 kDa glycoprotein produced and secreted by the tumor cell lines could be considered a cholangiocarcinoma-associated marker which has diagnostic potential.     

Influence of precipitated silica on dynamic mechanical properties and resistance to oil and thermal aging in CPE/NR blends

Blends of 80/20 CPE/NR filled with various silica loadings were prepared, and their properties were determined. It was found that cure properties are influenced significantly by the addition of precipitated silica. Scorch time and cure time decrease with increasing silica loading, which could be explained by the thermal history attributed to the shear heating in the blending stage. An increase in crosslink density as a function of silica loading is believed to be caused by a migration of curatives to the NR phase. In terms of phase morphology, with increasing silica loading, the NR dispersed phase size decreases due to the increase in compound viscosity and, thus, the shear stress available for efficient blending. An increase in silica loading also enhances resistance to oil due to the decrease in the NR dispersed phase size associated with the dilution effect, but gives no significant impact on thermal aging resistance. According to the change in damping peak height associated with the shift in T_g of the CPE phase, silica appears to preferentially migrate to the CPE phase due to the strong interaction between CPE and silanol groups of the silica surfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2218–2224, 2005     

Rheological properties,oil, and thermal resistance in sulfur‐cured CPE/NR blends

The use of natural rubber (NR) for partly substituting elastomeric chlorinated polyethylene (CPE) was carried out. Sulfur curing was used to vulcanize NR phase in the blends. Mechanical, rheological, and thermal aging properties as well as oil resistance of the blends were investigated. The amount of NR in blends significantly affects properties of the blends. With NR content in blends up to 20 wt %, tensile properties are similar to those of the pure CPE, even after either oil immersion or thermal aging. Rheological properties of CPE/NR blends determined from the rubber process analyzer (RPA 2000) and parallel‐plate rheometer are controlled strongly by the blend composition. The viscoelastic behavior of pure CPE and the blends with CPE as a major component is governed by the viscous response, which could be seen from the high damping factor, particularly at high strain, the short linear viscoelastic range, and the high degree of pseudoplasticity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1129–1135, 2004