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In this study, novel polyurethane/silica (PU/SiO2) hybrid materials, prepared without an external crosslinking agent, were developed via the chemical reaction between urethane groups of PU prepolymer and hydroxyl groups at the surfaces of silica. The added inorganic filler-silica thus played the dual roles not only inorganic chain extender but also reinforcing agent in the preparation of the hybrid. Two different blending methods, were compared with respect to the mechanical properties of the PU/SiO2 hybrid materials: stirring mixing and three-roller shear mixing. The hybridization mechanism was confirmed using Fourier-transform infrared spectroscopy (FT-IR), solid-state 29Si NMR spectroscopy and X-ray diffraction (XRD). The dispersion of silica particles in the PU matrix was investigated by scanning electron microscopy (SEM). Because of the shear effect of three-roller shear process, the size of the silica aggregates tended to be more uniform. The tensile strength and elongation at break of the PU/SiO2 hybrid were 51 MPa and 590%, respectively, which represent increases of fourfold and 39% compared to those of neat PU. The thermogravimetric analysis (TGA) results for the PU/SiO2 hybrids indicated greater thermal stabilities and lower decomposition rates after hybridization. This work contributes new insights into the preparation of high-performance PU/SiO2 hybrids. Keywords: Polyurethane, Silica, Hybrid material, Chain extender, Preparation

Interfacial compatibility plays a key role in the performances of natural fiber-reinforced composites. The measures commonly used to improve the interfacial compatibility focus more on the addition of various compatibilizers than on the structural modification of the natural fiber. In this paper, an attempt was made to enlarge the interfacial interaction areas of the recycled polyethylene (rPE)/wood flour (WF) composites by steaming the WF. Multi-monomer graft copolymers of polyethylene (GPE) were used as compatibilizers for the composites. How the enlarged interfaces affected the morphology, mechanical properties, water resistance, thermal stability, and dynamic rheological properties of the rPE/WF composites was investigated. The steaming process was able to enlarge the voids of the WF and therefore activate more interfaces for interactions. It was found that the interfacial morphology of the composites was affected by the degree of interfacial compatibility of the composites and so was characterized by various distinctive blossom shapes having a variation of compositions. With the help of GPE, the steaming process was able to significantly improve the interfacial compatibility of the composites and therefore improve the mechanical properties, water resistance, thermal stability, and dynamic rheological properties of the composites.

Antioxidants are normally utilized to extend the service life of polymers due to the strong reducibility of the phenolic hydroxyl group of the hindered phenol structure. Inspired by this characteristic, we have introduced green tea polyphenol (TP) supported on a silica surface containing considerable phenolic hydroxyl groups to obtain a novel biomass anti-aging filler (BAF, denoted as silica-s-TP) to reinforce and improve the anti-aging property of rubber composites. The applying of silica-s-TP to enhance the thermal-oxidative stability and ultraviolet light (UV) aging resistance of styrene-butadiene rubber (SBR) was evaluated. The hybrid biomass anti-aging filler could not only uniformly disperse in the rubber matrix, giving rise to the excellent mechanical properties, but also enhance the properties of thermal-oxidative stability and UV aging resistance with the increasing silica-s-TP content of SBR distinctly. This study provides a mild and environmentally friendly strategy to prepare the functional biomass filler, which could be applied as not only a reinforcement filler but also an anti-aging additive in “green rubber”.

In this study, a nitrogen–phosphorus intumescent flame-retardant 3-(N-diphenyl phosphate) amino propyl triethoxy silane (DPES), the ionic liquid (IL) of 1-butyl-3-methyl-imidazole phosphate, and a phosphorous-containing ionic liquid-modified expandable graphite (IL-EG), were synthesized, and their molecular structures were characterized. The flame-retardant rigid polyurethane foams (RPUFs) were compounded with synergistic flame-retardant IL-EG/DPES to study the effects of the combination IL-EG and DPES on the pore structure, mechanical properties, thermal decomposition behavior and thermal decomposition mechanism of RPUF. The results showed that IL-EG/DPES had good thermal stability, and an excellent expansibility and char yield. The flame-retardant RPUF, modified with IL-EG and DPES at the ratio of 1:1, had a relatively uniform pore size, the highest compressive strength, and an excellent flame-retardant performance due to the form interwoven hydrogen bonds between IL-EG and DPES, as well as the new synergistic flame-retardant coating on the RPUF surface to restrict the transfer of gas or heat into the PU matrix.

Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes–silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes–silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail.

In this paper, rigid polyurethane foams that were filled with expandable graphite (RPUF/EG) composites were prepared by the liquid blending method, and then the structure and flame retardancy performance of materials were investigated through optical microscope, scanning electron microscope, limit oxygen index, cone calorimeter, thermogravimetric analysis coupled to fourier transform infrared spectrum, and X-ray photoelectron spectroscopy. The results showed that a large number of EG could be good to the exhibition of flame retardancy of RPUF, where the optimal material was found at loading 15 phr EG that showed an increased limit oxygen index value and a decreased calorific or fuming value. TGA coupled FTIR and XPS revealed that EG could disassembled before RPUF under heating treatment, and it could form a pyknotic and enahnced residual carbon layer on RPUF surface after the fire, which restricted the transfer of gas, like oxygen or heat into PU matrix, finally resulting in the promotion of flame retardancy of RPUF.

Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle (silica-s-VA7). Functional nanoparticles can not only effectively crosslink rubber without sulfur as a novel vulcanizator, but are also evenly dispersed in the rubber matrix and improve the dispersion of the remaining pristine silica as an interfacial compatibilizer. In addition, the thicker immobilized polymer layer and prominent crosslinking density of SBR nanocomposites simultaneously demonstrate that the novel vulcanizing agent silica-s-VA7 gives rise to significant improvement on the rubber–filler interfacial adhesion on account of the covalent linkages of organic and inorganic interfaces between elastomer and nanofillers. We envisage that this strategy may provide a new avenue to implement high-efficiency design for a multifunctional rubber-vulcanizing agent through an organic and inorganic hybridization mechanism.

A novel Flame-Retardant N-(P,P′-diphenyl) phosphorus-based-(3-triethoxysilicon) propylamine (DPTP) was synthesized in this study. The impact of DPTP on the mechanical properties, thermal stability, and flame retardancy of rigid polyurethane foam (RPUF) was studied. The addition of DPTP to RPUF can significantly reduce the undesirable thermal effects and smoke density during combustion, as well as increasing the limiting oxygen index. Compared with pure RPUF, the peak heat release rate of RPUF containing 10 phr of DPTP decreased by 39.4%, while its peak smoke production rate decreased by 49.9%. However, it was also found that the addition of DPTP reduced the compressive strength of RPUF.

Flame retardant modification of leaf fibers was carried out to solve the technical problem of poor fire resistance of plant fibers and improve the utilization rate of urban fallen leaves in building materials. The modification scheme adopts three flame retardants, i.e., ammonium polyphosphate (APP), magnesium hydroxide (MH), and aluminum hydroxide (ATH), and two covering layers, i.e., pure acrylic polymer lotion and water glass (Na2O · nSiO2) solution. The modified leaf fiber's combustion behavior and pyrolysis properties were tested and analyzed. The physical and mechanical characteristics, as well as the thermal insulation qualities, of leaf fiber cement-based composites (LFCC) were studied at high temperatures. The findings revealed that the three flame retardants had an effect on the chemical structure of leaf fibers. In comparison to leaf fibers without flame-retardant modification, flame-retardant-modified leaf fibers have a much greater thermal stability. and its LOI is greater than 27.0%, which is a fire-retardant material. Except for the sample with water glass as the modified cover layer, at high temperatures, the composite flame-retardant fiber LFCC's mass-loss rate is lower compared with fibers without flame-retardant modification or fibers modified with only one kind of flame-retardant. In the composite flame-retardant modified fiber LFCC, the samples with better strength at high temperature are those with ATH replacing 30% and 50% MH. The thermal conductivity of LFCC is negatively correlated with the range of temperature change.

To solve the poor fireproof performance of plant fibers, one of the technical difficulties, and use more straw fibers as construction materials, wheat straw fibers (WSFs) have been subject to flame-retardant modification. Then, tests and analysis over the modified WSFs per the burning behavior and pyrolysis performance have been made. The physical and mechanical, and thermal insulation properties of wheat straw fiber cement-based composites (WSFCC) at high temperatures were characterized. The results are as follows: Ammonium polyphosphate (APP), magnesium hydroxide (MH), and aluminum hydroxide (ATH), three fire retardants, all affect the chemical structure of WSFs. P, Mg, and Al elements of the three retardants are successfully adsorbed onto the fibers' surface subject to modification. Flame-retardant WSFs significantly outperforms the non-flame-retardant ones per thermostability and flame retardancy. The heat release rate (HRR), total heat release (THR), effective heat of combustion (EHC), and mass loss rate (MLR) of most flame-retardant WSFs are obviously lower than those of non-flame-retardant ones. The APP-modified WSFs demonstrate higher total smoke production (TSP), while WSFs modified with composite flame retardants perform better in flame retardancy and smoke suppression. The MLR of WSFCC at high-temperature increases as the temperature goes higher. The compressive and flexural strengths of WSFCC decrease with the increase of temperature and the decrease mitigates after 350 °C. In terms of thermal conductivity, composite-flame-retardant fiber WSFCC are much higher than non-flame-retardant fiber and APP-modified fiber WSFCC. As the temperature rises, the thermal conductivity of composite-flame-retardant fiber WSFCC tends to decrease.

ABSTRACT The aggregation structure of lignin in aqueous solution had an important effect on the dispersion of lignin and the properties of lignin/styrene-butadiene rubber (SBR) composites. This article revealed the relationship between aggregation structure and chemical structure of modified lignin. Unmodified lignin was amorphous; however, our results showed that aldehyde-modified lignin was transformed into spherical aggregates, while propylene-oxide-modified lignin self-aggregated into supramolecular domains. The relationships between aggregation structure, filler dispersion, filler-rubber interaction, and performance were also studied by investigating the microstructure, viscoelastic behavior, and mechanical properties of lignin/SBR composites. Meanwhile, a solution to improve the coprecipitation efficiency of lignin and SBR latex was proposed. In this article, epoxidized natural rubber (ENR) was also used as compatibilizer to improve the interfacial adhesion between polar lignin and nonpolar SBR. The results showed better lignin dispersion for the ENR-containing rubber composites, as well as superior wet skid resistance and lower rolling resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45759. [ABSTRACT FROM AUTHOR]

To improve the resource level of agricultural and forestry waste straws and fallen leaves, straw and fallen leaves fibres were used as organic thermal insulation components (TICs). Vitrified beads and closed-pore expanded perlite were used as inorganic TICs to prepare plant fibre cement-based composite thermal insulation mortar (TIM). The effects of TICs on physical and mechanical properties of TIM were studied by altering the types and contents of TICs. The results show that the fluidity of the TIM decreases with the incorporation of plant fibres in the vitrified bead + expanded perlite TIM. With the addition of wheat straw fibre and straw fibre, the homogeneity of TIM mixture is improved. Plant fibres have the characteristics of lightweight, porosity, water absorption and heat preservation, which increases water absorption and heat retention and a decrease in strength of the TIM. With the incorporation of three plant fibres of leaves, wheat straw and straw, the water absorption of TIM increased by 15.84, 5.47, and 4.54% respectively. At the same time, thermal conductivity decreased by 0.17, 0.19, and 0.20 W/(m.K), respectively, flexural strength decreased by 3.99, 2.63, and 2.44 MPa, and compressive strength decreased by 20.91, 17.13, and 19.25 MPa, respectively. After the expanded perlite and vitrified microbeads are modified with pure acrylic emulsion, the polymer film retains more pores inside the fibres, enhances the interface bonding with the cement-based material, which is helpful to improve the thermal insulation properties and strength of the TIM.

Rice husks are the fine crop residue used to prepare the industrial wood-like products by melt-blending with polymers. However, most wood-like products are highly filled with natural fibers in order to decrease the cost of the products, as it causes weak interfacial compatibility between the natural fibers and polymers. To successfully prepare a high performance wood-like product, the interfacial compatibility is the key problem that need to be solved. Moreover, the interfacial interactions at the gaps and voids around the natural fibers can enhance the interfacial compatibility of the composites. There is little research focusing on the interfacial interactions at these gaps and voids. In this paper, the multi-monomer graft copolymers of polyethylene (GPE) were used as the compatibilizers for the rice husk (RH) highly filled recycled polyethylene (rPE) composites. How the GPE affected the interfacial compatibility of the composites and the resulting mechanical properties, water resistance, thermal stability and rheological properties of rPE/RH composites were investigated. Results show that GPE could enhance the interfacial interactions of rPE/RH composites by infiltrating into the gaps and voids around RH. The strong interfacial interactions of the composites primarily came from the chemical reactions and physical interactions between RH and GPE. The mechanical properties, water resistance and thermal stability of the composites increased with the increase in GPE loadings. The preferable loadings of GPE were approximately at 8 phr. Meanwhile, GPE could improve the processing properties of the composites. [ABSTRACT FROM AUTHOR]

Introduction: The roles of some indicators in the prognosis of patients with coronavirus disease-19 (COVID-19) remain unclear and controversial. This study aimed to explore the epidemiologic characteristics of and prognostic factors for COVID-19 to provide updated recommendations for its prevention, diagnosis, and treatment.Methods: For this retrospective study, demographic, epidemiologic, and clinical data were extracted from the medical records of patients admitted to the Maternal and Child Hospital of Hubei Province (Optical Valley) with COVID-19 between February 19, 2020, and March 19, 2020. The primary outcome was the prognosis that was determined at discharge as mentioned in the medical records. Descriptive statistics, univariate analyses, and stepwise logistic regression analysis were used for data analysis.Results: Of the 1,765 patients included, 93.1% were cured and the mortality was 1.8%. Univariate analyses identified 63 factors significantly associated with COVID-19 prognosis. Logistic regression analysis revealed that a poorer prognosis was associated with undergoing resuscitation, complex disease manifestations, consultation with outside specialists, elevated basophil or lymphocyte counts, an albumin (ALB)/globulin (A/G) ratio > 2.4, and elevated levels of serum aspartate aminotransferase (AST) or creatinine. Patients had a better prognosis if the following conditions were met: dry cough reported as an initial symptom, fatigue as a clinical manifestation, and a diagnosis based on laboratory testing.Conclusion: To prevent clinical deterioration, clinicians should provide special care to patients who underwent resuscitation, with a critical disease, or requiring consultation with outside specialists. Extra attention should be paid to patients with high basophil or lymphocyte counts, a high A/G ratio, and elevated AST or creatinine levels.

To improve the utilization of crop straws as a resource and the compatibility between straw fibers and cement-based materials, the hydration of modified straw fiber cement-based composite (SFCC) was studied. The structural characteristic of SFCC was investigated by FTIR, SEM, and XRD. The results show that the setting time of several modified straw fiber SFCC pastes was shorter than that of the unmodified straw fiber SFCC paste, and the best method of fiber modification to improve the setting time of the SFCC paste is Na2O·nSiO2 treatment. The recommended fiber modification method for improving the compatibility between straw fibers and cement-based materials is alkali modification, followed by pure acrylic emulsion modification and Na2O·nSiO2 modification. To improve the strength of SFCC, the straw fiber should be modified by alkali, followed by pure acrylic emulsion and Na2O·nSiO2 modification and the method of water modification is also recommended. The phase types and relative contents of crystalline hydration products mixed with the modified straw fiber SFCC are significantly higher than those of the unmodified fiber SFCC. The fiber treatment method that was most helpful to increase the structural density of hydrates of SFCC was alkali treatment and pure acrylic emulsion treatment, followed by Na2O·nSiO2 treatment.

Five modification methods are adopted for wheat straw fibers (WSFs). The effects of modification methods on the water absorbency of wheat straw fiber/wheat straw fiber cement-based composite (WSFCC) and the mechanical properties of WSFCC are analyzed. The crystallinity, chemical structure, and micromorphology of WSFs and WSFCC 28-day specimens are characterized by XRD, FTIR, and SEM methods. The results show that the water absorption of WSFs modified with sodium silicate solution, pure acrylic acid emulsion, and silicone waterproof emulsion surface spraying is 10.67%, 5.18%, and 1.05% lower than that of unmodified WSFs, respectively. Alkali modification is the ideal method for improving the strength of WSFCC. Establishing a fitting formula of the relationship between water absorption of WSFs and strength of WSFCC specimens has important theoretical and practical guiding significance for development and application of WSFCC.

A novel intrauterine devices material, polyurethane/nano-copper (PU/NC) nanocomposite, was prepared. The structure, morphology, copper ion (Cu2+) release rate, and water absorption of PU/NC nanocomposites were investigated. The results indicated that the nanocoppers were uniformly dispersed in the matrix. The release rates of Cu2+ of PU/NC nanocomposites remained stable during the experimentation time. These results indicated that the PU/NC nanocomposites have a great potential to replace current commercial intrauterine devices materials. [ABSTRACT FROM AUTHOR]

The bisphenol AF/benzyltriphenylphosphonium chloride (BPP) vulcanization system is the most commonly used fluoroelastomer (FPM) vulcanization system. In this article, polyphenol hydroxy acrylic rubber (PHACM) was prepared through a two-step reaction: grafting polymerization and condensation. The properties of FPM/PHACM/acrylic rubber (ACM) blends including vulcanization properties, mechanical properties, aging properties, oil resistance and thermal properties were studied. The results of vulcanization properties show that under the bisphenol AF/BPP vulcanization system, the FPM can achieve covulcanization with PHACM without adding bisphenol AF and get longer scorch time than that of FPM with the same level of bisphenol AF, which means that FPM/PHACM/ACM blends have better processability and curing security. Furthermore, the blends show better mechanical properties and thermal stability. The results of differential scanning calorimeteric analysis show that the FPM and PHACM achieve co-cross-linking and have good compatibility. The glass transition temperature (Tg) of the blends has been reduced to −18.57°C, which is 8.33°C lower than that of pure FPM, when the content of blends is equal to 100/100. The scanning electron microscopy shows that PHACM can improve interfacial adhesion between the FPM and ACM. [ABSTRACT FROM PUBLISHER]

The ionic liquid, 1-butyl-3-methylimidazole hexafluorophosphate (BmimPF6), was utilized to modify carbon black (CB) via microwave (MW) irradiation. The conditions for the preparation of the modified CB (m-CB) were optimized. The reinforceability of the m-CB in styrene-butadiene rubber (SBR), butadiene rubber (BR) and nitrile rubber (NBR) composites were evaluated. The curing behaviour, morphology and tensile properties of the rubber/m-CB composites were studied and compared with those of composites filled with unmodified CB. Rubber/m-CB compounds showed a significant increase in the curing rate for a generated zinc complex with the alkylimidazoles. Compared with CB, m-CB exhibited a significantly improved reinforceability of the rubbers at lower filler loading, although the mechanical properties were changed slightly at higher filler loading. A possible mechanism was proposed, based on the molecular slippage theory in which the interfacial bonding, the filler loading and the chain flexibility of the rubber molecules were all considered. [ABSTRACT FROM AUTHOR]

In this study, a new trimethacrylate monomer α, α,α'-tri[4-(2′- hydroxy-30-methacryloyloxy-propoxy)phenyl]-1-ethyl-4-isopropylbenzene (α,α'- THMPEIB) with a molecular weight of 850 and a large molecular volume was designed and synthesized. The structure of monomer a,a,a0-THMPEIB was confirmed by FT-IR, ¹H NMR, and elemental analysis. Degree of double-bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, and flexure strength of α, α,α'-THMPEIB/tri(ethylene glycol) dimethacrylate- (TEGDMA) based resin were measured. 2,2-Bis[4-(2′-hydroxy-3′-methacryloyloxy- propoxy)-phenyl]-propane (bis-GMA)/TEGDMA monomer mixture was used as reference. The result showed that the α, α,α'-THMPEIB/TEGDMA-based resin had the lower double-bond conversion, polymerization shrinkage, and water solubility than bis-GMA/TEGDMA-based resin. Water sorption and diffusion coefficient value of α, α,α'-THMPEIB/TEGDMA-based resin were nearly the same as those of bis-GMA/TEGDMA-based resin. Flexural strength of α, α,α'-THMPEIB/TEGDMA-based resin was higher than that of bis-GMA/ TEGDMA-based resin. [ABSTRACT FROM AUTHOR]

Methacrylate resin-based sealers have attracted wide attention because of their easy handling, superior aesthetic qualities, good mechanical properties and excellent adhesive ability with dentin. 2,2-Bis[4-(2′-hydroxy-3′-methacryloyloxypropoxy)-phenyl]-propane (Bis-GMA) is the main component of the newly developed commercial root canal sealer 'Epiphany', which is one of the methacrylate resin-based sealers. In order to further reduce the polymerization volume shrinkage of Bis-GMA, 4,4′-(α-methylbenzylidene)-bis(2′-hydroxy-3′-methacryloyloxy-propoxy)benzene (4,4′-AMBHMB) with higher molecular weight and larger molecular volume was synthesized to replace Bis-GMA as one of the components of the root canal sealer used in this study. The structure of monomer 4,4′-AMBHMB was confirmed by FT-IR, 1H-NMR, mass spectrum and elemental analysis. The photopolymerization behavior of mixture of 4,4′-AMBHMB and triethylene glycol dimethacrylate (TEGDMA) was investigated by FT-IR. Degree of double bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, flexure strength and glass transition temperature of 4,4′-AMBHMB/TEGDMA system with a mass ratio of 50:50 were measured. A 50:50 Bis-GMA/TEGDMA formulation was used as reference. The results illustrated that 4,4′-AMBHMB/TEGDMA system had the same double bond conversion and water sorption with Bis-GMA/TEGDMA system. Polymerization shrinkage, water solubility and diffusion coefficient of 4,4′-AMBHMB/TEGDMA system were lower than that of the Bis-GMA/TEGDMA system, whereas the flexural strength and glass-transition temperature of 4,4′-AMBHMB/TEGDMA system were higher than that of the Bis-GMA/TEGDMA system. [ABSTRACT FROM AUTHOR]

In this study, a new dimethacrylate monomer 5,5′-bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)-phenyl]-hexahydro-4,7-methan-oindan (5,5′-BHMPHM) with molecular weight of 640 and large molecular volume was designed and synthesized. The structure of monomer 5,5′-BHMPHM was confirmed by FT-IR, 1H-NMR and elemental analysis. Degree of double bond conversion, volume shrinkage, contact angle, water sorption and solubility, diffusion coefficient value, flexure strength and modulus of 5,5′-BHMPHM/tri(ethylene glycol) dimethacrylate (TEGDMA) based resin were measured. 2,2-bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)-phenyl]-propane (Bis-GMA)/TEGDMA based resin was used as reference. The result illustrated that the double bond conversion, polymerization shrinkage, and diffusion coefficient value of 5,5′-BHMPHM/TEGDMA based resin were significantly lower than that of Bis-GMA/TEGDMA based resin ( P < 0.05). Water sorption, solubility, flexure strength and modulus of 5,5′-BHMPHM/TEGDMA based resin were higher than that of Bis-GMA/TEGDMA based resin ( P < 0.05). There was no statistical difference between 5,5′-BHMPHM/TEGDMA based resin and Bis-GMA/TEGDMA based resin in contact angle ( P > 0.05). [ABSTRACT FROM AUTHOR]

Chemical mechanical polishing (CMP) pads are generally designed to play a passive role in terms of chemical reactions that occur on the surface to be polished. For copper CMP, a pad that is capable of initiating and controlling various chemical reactions on the copper surface can bring another dimension of flexibility to the CMP process. This work investigates such a model pad for its potential applications in copper CMP. More specifically, the physical and chemical properties of a polyurethane pad containing 1H-benzotriazole (BTA) are examined. When applied to Cu blanket wafers, the BTA-containing pad yielded a higher removal rate compared to the conventional CMP process with the reference pad. For patterned wafer polishing, the results indicate that the BTA-containing pad is effective in improving the step height reduction efficiency and in minimizing dishing and erosion. The potential applications of a pad with such a design for gaining a fundamental understanding of the copper CMP process are discussed based on these experimental results. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs), a kind of naturally occurring silicates possessing typical fibular structure, were introduced to fabricate polypropylene (PP)/HNTs nanocomposites. The non-isothermal crystallization behaviors were investigated by differential scanning calorimetry (DSC) method according to different treatments. The results suggest, with the inclusion of HNTs in PP matrix, the nanocomposites crystallize at higher temperature regime, which are correlated with the heterogeneous nucleating effects of HNTs during the crystallization process of PP. The kinetics studies of crystallization show that PP nanocomposites possess faster crystallization process and higher activation energy due to the nucleating effect and hindrance effect of HNTs to the motion of PP chains. The polarized light microscopy (PLM) observations further show that HNTs serve as nucleation sites and accelerate the crystallization process. [ABSTRACT FROM AUTHOR]

Hyperbranched epoxy resin (HTDE) has relatively low viscosity and high molecular mass and holds great promise as a functional additive for enhancing the strength and toughness of thermosetting resins. In this work, the curing and thermal degradation kinetics of HTDE/diglycidyl ether of bisphenol-A epoxy (DGEBA) hybrid resin were studied in detail using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) techniques by Coats–Redfern model. The effect of molecular mass or generation and content of HTME on the activation energy, reaction order, and curing time were discussed; the results indicated that HTDE could accelerate the curing speed and reduce the activation energy and reaction order of the curing reaction. [ABSTRACT FROM AUTHOR]

The effects of polypropylene-grafted-dibutyl maleate (PP-g-DBM) used as compatibilizer on mechanical, rheological and morphological properties of polypropylene (PP) and nylon 6 (PA6) blends was systematically investigated in this paper. The results of Molau test, solvent extraction and differential scanning calorimetry (DSC) indicated the formation of PP-g-PA6 in vicinity of interfaces during melting extrusion. Owing to the reaction between the reactive groups of PP-g-DBM and amine (-NH2) end groups of PA6, the tensile and impact strength of the PP-g-DBM compatibilized PP/PA6 blends were much higher than that of the uncompatibilized PP/PA6 blends. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the domain sizes of the dispersed phase in the compatibilized PP/PA6 blends decreased and the interfaces become more indistinct, which indicated a clear compatibiliting effect was induced by the PP-g-DBM in the immiscible PP/PA6 blends, i.e. the PP-g-DBM was an effective compatibilizer for the PP/PA6 blends. In addition, the rheological measurements showed the PP-g-DBM compatibilized PP/PA6 blends possessed higher pseudo plasticity, melt viscosity and flow activation energy. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs) are chemically modified via silylation with 3-(trimethoxysilyl)propyl methacrylate. The modified HNTs (m-HNTs) are characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, solid state 13C NMR spectroscopy, thermogravimetric analysis (TGA) and extraction experiment. It is showed that the silane has been effectively grafted onto HNTs surface and renders the hydrophobicity to m-HNTs. The nanocomposites consisting of polyamide 6 (PA6) and m-HNTs show significantly improved mechanical properties and heat distortion temperature, which are attributed to the covalent interfacial bonding and the excellent dispersion state of m-HNTs. M-HNTs are found to disperse individually into PA6 matrix. The nucleation effect by m-HNTs is verified by the lowered fold-surface free energy of PA6/ HNTs nanocomposites and the observation of polarized optical microscopy (POM). Both high cooling rate and high m-HNTs loading are beneficial to the formation of gamma-crystals of PA6. The polymorphism could be correlated to the heterogeneous nucleation effects of m-HNTs and the interfacial interactions between m-HNTs and PA6 matrix. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs) were used to compound with linear low density polyethylene (LLDPE) to prepare composites with better mechanical properties and higher flame retardancy. The PE graft was used as interfacial modifier in the LLDPE/HNTs composites. HNTs were showed to be a promising reinforcing and flame retardant nano-filler for LLDPE. The mechanical properties and flame retardancy as well as thermal stability of the composites can be further enhanced by the addition of the graft copolymer. Morphological observation revealed that the graft copolymer could facilitate the dispersion of HNTs in LLDPE matrix and enhance the interfacial bonding. [ABSTRACT FROM AUTHOR]

In this article, the organically modified clay (organoclay) was prepared by treating Na-montmorillonite with alkylammonium ions through a solid state method. Polypropylene (PP)/organoclay nanocomposites were prepared by melt intercalation. X-Ray Diffraction (XRD) and Transmission Election Microscopy (TEM) indicated that PP chains could intercalate into the gallery of organically modified clay to form the exfoliated PP/organoclay nanocomposites. The crystallization peak temperature of PP/organoclay nanocomposites was higher than that of neat PP by Differential Scanning Calorimetry (DSC). According to XRD, the addition of organoclay did not change the crystal structure of PP. Thermalgravimetric analysis showed that the thermal decomposition temperature of PP/organoclay nanocomposite was higher than that of PP. A mechanical properties test indicated that the impact strength of PP/organoclay nanocomposites were better than that of neat PP when the organoclay content was below 7 wt%. [ABSTRACT FROM AUTHOR]

The isothermal crystallization behavior of neat polypropylene (PP) and solid-phase graft copolymers of PP with maleic anhydride and methyl methacrylate (PPMM) were compared by differential scanning calorimetry. The Avrami equation and Hoffman theory were applied to describe the isothermal crystallization kinetics. The results show that the fitted isothermal crystallization parameters are similar to the experimental data, and suggest that the Avrami equation is suitable to describe the isothermal crystallization process of PP and PPMM. The grafted side chains on PP can change the nucleation and growth of crystallization. They caused a decrease in the apparent crystallization activation energy and lateral surface free energy, and an increase in the nucleation rate. This was attributed to the grafted side chains not only acting as nucleating agent but also hindering the motion of the molecular chains and reducing the growing rate of crystallization. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs) were utilized to prepare polypropylene (PP) nanocomposites by simple melt-compounding approach. Compared with other silicates such as montmorillonite and kaolinite, HNTs show much better dispersion property. The PP nanocomposites with HNTs exhibit concurrence increase in tensile and flexural strength, flexural modulus and impact toughness. Surface modification of HNTs lends the PP nanocomposites higher strength, modulus and lower toughness. The increase in mechanical properties is correlated with the well dispersion of the high aspect ratio HNTs and the orientation of HNTs in PP matrix. Morphology studies show that HNTs can be dispersed in PP uniformly at lower HNTs loading and excessive loading of HNTs causes a little aggregation. Surface modification of HNTs can alleviate the aggregation effectively. The storage modulus of the nanocomposites increases consistently with the HNTs concentration. The surface modification is beneficial to the further improvement in storage modulus. Similar to other silicates, HNTs facilitate the crystallization of PP due to the heterogeneous nucleation. [ABSTRACT FROM AUTHOR]

In present work, the effect of novel blocked mercaptosilane(3-propionylthio-1-propyltrimethoxylsilane) (called hereafter PXT) on structure and dynamic mechanical properties of natural rubber/silica (NR/silica) composites was studied in efficient, semi-efficient and conventional vulcanization systems. Equilibrium swelling method investigation indicates that PXT is able to enhance crosslinking density of composites. The investigation of properties shows that PXT can strengthen the reinforcement of silica for NR vulcanizates and substantially enhance the resistance to flex cracking and abrasion of NR/silica composites. Since PXT possess two functionally active end groups which can chemically react with both silica and rubber, at 2 phr of the PXT content, NR/silica composites possess optimum comprehensive dynamic mechanical properties. [ABSTRACT FROM AUTHOR]

Natural occurred nanotubes, halloysite nanotubes, were modified by silane and incorporated into epoxy resin to form nanocomposites. The morphology of the nanocomposites was characterized by transmission electron microscopy (TEM). Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were performed on the nanocomposites. Flexural property and coefficient of thermal expansion (CTE) of the nanocomposites were also determined. Comparing with the neat resin, about 40% increase in storage modulus at glassy state and 133% at rubbery state were achieved by incorporating 12 wt% modified HNTs into the epoxy matrix. In addition, the nanocomposites exhibited improved flexural strength, char yield and dimensional stability. TEM examination revealed a uniform dispersion of the nanotubes in the epoxy resin. The remarkably positive effects of the HNTs on the performance of the epoxy resin were correlated with the unique characteristics of the HNTs, the uniform dispersion and the possible interfacial reactions between the modified HNTs and the matrix. [ABSTRACT FROM AUTHOR]

A method of chemical modification in situ of ethylene-propylene-diene rubber (EPDM) filled with carbon black was studied. A bifunctional monomer, glycidyl methacrylate (GMA), was used as the modifier to improve the dispersibility of carbon black in the rubber and to enhance the mechanical properties of EPDM vulcanizates. The effects of GMA on the structure and properties of EPDM vulcanizates such as determination of cross-linking density and vulcanizing properties as well as mechanical properties were investigated by FT-IR, SEM, and DMTA. The results showed the addition of GMA into carbon black filled EPDM compounds could remarkably improve the mechanical properties of the vulcanizates. The optimum content of GMA was about 5.0 phr when the content of carbon black was 50 phr. The reason for improvement of the mechanical properties might be attributed to the chemical combinations between rubber macromolecular chains and carbon black surfaces by GMA. The action of GMA was similar to a cocuring agent and a coupling agent. [ABSTRACT FROM AUTHOR]

The thermal decomposition and oxidation ageing behaviour of polypropylene (PP) and PP/halloysite nanotube (HNT) nanocomposites were studied. The kinetics of thermal decomposition were calculated by integral models. The thermal oxidation ageing was investigated by Fourier transform infrared spectroscopy (FTIR). The PP nanocomposites showed a higher activation energy of thermal decomposition than neat PP. Their surface treatment and lower HNT loading led to a higher activation energy of decomposition. Their improved thermal stability in nitrogen was attributed to entrapment of decomposition products at initial decomposition stage and to barrier effects. Nanocomposites made by using silane-modified HNT(m-HNT) and also those with lower quantities of (unsilanated) HNT showed improved resistance to thermo-oxidative ageing. The rate of thermo-oxidative ageing was correlated with the number of acidic sites and the volume of entrapped oxygen in the lumen of the HNT and in cavities. [ABSTRACT FROM AUTHOR]

Dynamic rheology, differential scanning calorimetry and in situ Fourier transform infrared spectroscopy were used to study the cure behavior of unsaturated polyester/modified montmorillonite nanocomposites. The results showed that their gel times increased markedly at the same cure temperature, and that the activation energy of the nanocomposites was higher than that of the pure unsaturated polyester. Their peak temperatures of enthalpy increased as well. The total exotherm of the cure reaction declined and the cure rate decreased. In the curing process of pure unsaturated polyesters, the conversion of styrene was higher than that of the double bonds on unsaturated polyester macromolecular chains. The cure mechanism of the unsaturated polyester/modified montmorillonite changed because of the presence of double bonds in the layers of modified montmorillonite. However, the conversion of styrene in the nanocomposites was lower than that of double bonds on unsaturated polyester chains during cure at room temperature, and the conversion of styrene was increased after post‐curing and was higher than that of the double bonds on unsaturated polyester chains at the end of the cure reaction. Moreover, the degree of reaction of double bonds on unsaturated polyester chains of the nanocomposites was higher than that of unsaturated polyesters. Copyright © 2006 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The nanocomposites of natural rubber (NR) and organoclay with unsaturated carbon-carbon double bonds (C=C) on interlayer surfaces (USMMT) are prepared by the grafting and intercalating method in latex in the presence of butyl acrylate (BA) monomer. The conversion, grafting efficiency, and grafting percentage of BA onto NR and USMMT are determined. The structure and morphology of the nanocomposites are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmitted electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling experiments. The mechanical properties of the nanocomposites are measured. The results show that graft copolymerization of BA monomer onto NR molecular chains can take place with high conversion, grafting percentage, and grafting efficiency. At the same time, BA can intercalate into the interlayer galleries of USMMT and polymerize in situ together with C=C bonds on the interlayer surfaces. As a result, the interlayer spacing of organaclay is increased and the interfacial combination between the silicate layers and rubber is strengthened. The results of XRD and TEM demonstrate the formation of the nanocomposites of NR-M-USMMT. The glass transition temperatures of the nanocomposites are higher than that of the NR vulcanizate. The mechanical properties of the nanocomposites are remarkably improved compared with those of the NR and NR-USMMT vulcanizate. [ABSTRACT FROM AUTHOR]

The scrap rubber powder (SRP) could be compression moulded to form elastomer via in situ interfacial reactions. In this study, SRP/NR (85/15) blends with good performance could be prepared by incorporating a little amount (lower than 5 phr of SRP and NR) of m-phenyl bismaleimide (BMI) in the compositions. The mechanical properties and the interface of SRP/NR (85/15, w/w) blends (base blend) were investigated. The results showed that the processing temperature, time, and BMI content have significant effects on the mechanical properties of the blends. The optimum BMI content and processing condition were determined as 5 wt.% and 180 ○C/10 min. The mechanical properties, especially the elongation at break, of the elastomers could be improved further by ultraviolet (UV) exposure. With UV exposure, the tensile strength, elongation at break and tear strength of the modified base blend were determined as 10.4 MPa, 260% and 24 KN/m respectively. The FTIR results indicated that the BMI could be grafted onto the SRP surface under UV exposure. The composition with UV exposure had more uniform dispersion of the BMI and improved interfacial adhesion. The glass transition temperature ( Tg) of the blends was increased by increasing the processing temperature, processing time or the introduction of UV exposure. [ABSTRACT FROM AUTHOR]