Cost‐effective porous ceramic tubes fabricated through a phase inversion/casting process using calcined bauxite

Cost‐effective ceramic tubes based on low‐price commercial calcined bauxite for economical separation were fabricated by a new phase‐inversion casting method. The thermal shrinkage and weight loss during heating of the green tubes were characterized by dilatometric analysis and TG, respectively. Three shrinkage stages appear successively, corresponding to the viscous deformation of polymeric binder at 200‐300°C, significant combustion loss of ~5.2 wt% at 500‐620°C and sintering shrinkage over 800°C, respectively. However, due to high enough viscosity of the casting suspension that can guarantee the green tube against collapse or deformation during the phase inversion/casting process, the sintered tubes display nearly uniform microstructure instead of characteristic asymmetrical structure of the phase inversion process. The influence of sintering temperature on the pore property (including pore size and porosity) and mechanical strength was investigated. As the sintering temperature increases from 1200 to 1400°C, the porosity and average pore size decrease from 46.4% to 37.0% and from 0.98 to 0.81 μm, respectively, and the flexural strength increases from 25.8 to 65.1 MPa. The cost‐effective ceramic tube sintering at the range of 1250‐1400°C can be capable of functioning as a microfiltration membrane or an ultrafiltration membrane support.     

Thermal and mechanical behaviors of poly(vinyl alcohol)–lactose blends

Thermal and mechanical behaviors of poly(vinyl alcohol) (PVA)–lactose blends were studied by differential scanning calorimetry, thermal gravimetric analysis, and stress–strain analysis. The increase in glass transition temperature of the PVA–lactose blends with lactose contents suggests the formation of hydrogen‐bonded PVA–lactose complex in the PVA matrix. The hydrogen bonding interactions can improve thermal and mechanical properties of the blends. Results of this study demonstrate that lactose, a byproduct of dairy industry, can be used directly and in substantial quantity (33%) as a modifier to enforce the physical properties of PVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 929–935, 2002     

Axial‐feed thermoforming of oriented polypropylene tubes

The effect of newly developed axial feed thermoforming process (AFTF) on mechanical properties and morphology were investigated to gain a better understanding of structure–properties–process relationship. The starting material for AFTF is an oriented polypropylene tube (OPP) produced in uniaxial direction by using solid state extrusion process. Morphological changes from solid‐state extrusion are briefly reported. A die‐less bulge testing system was designed to bulge OPP tube at a high temperature in biaxial direction. Wide‐angle X‐ray diffraction, field emission scanning electron microscope, and optical microscopy were used to characterize the microstructure of the extruded and bulged samples of OPP. In addition, tensile tests were carried out at room temperature of samples machined from the extruded and bulged tubes along the axial and hoop directions. The results show that tensile strength increases with draw ratio in extruded samples as well as improvements in ductility were obtained in die‐less bulge tests with an increase in axial feed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Development of a poly(N‐vinyl‐2‐pyrrolidone)/poly (ethylene glycol) hydrogel membrane reinforced with methyl methacrylate‐grafted polypropylene fibers for possible use as wound dressing

A hydrogel is a polymeric material that exhibits the ability to swell in water and retains a significant fraction of water within its structure, but does not dissolve in water. One of the major problems in the application of these materials is their relatively poor mechanical strength, attributed to the high degree of hydration of the gel. This work was directed to the study of the interactions between hydrophobic and hydrophilized fibers, with the objective of optimization of the mechanical properties of poly(N‐vinyl‐2‐pyrrolidone) membranes. The membranes were prepared by electron‐beam irradiation of an aqueous polymer solution. A nonwoven cloth made of polypropylene matted fiber, grafted with methyl methacrylate, was employed as a reinforcement. The changes in the main properties of the membranes, such as the gel content, swelling characteristics, cytotoxicity, and mechanical behavior, were investigated. The results showed an increase of 800% in tensile strength, without changes in the swelling and cytotoxicity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 662–666, 2002     

Thermal and mechanical properties of liquid silicone rubber composites filled with functionalized graphene oxide

To improve the thermal and mechanical properties of liquid silicone rubber (LSR) for application, the graphene oxide (GO) was proposed to reinforce the LSR. The GO was functionalized with triethoxyvinylsilane (TEVS) by dehydration reaction to improve the dispersion and compatibility in the matrix. The structure of the functionalized graphene oxide (TEVS‐GO) was evaluated by Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, X‐ray diffraction (XRD), and energy dispersive X‐ray spectroscopy (EDX). It was found that the TEVS was successfully grafted on the surface of GO. The TEVS‐GO/LSR composites were prepared via in situ polymerization. The structure of the composites was verified by FTIR, XRD, and scanning electron microscopy (SEM). The thermal properties of the composites were characterized by TGA and thermal conductivity. The results showed that the 10% weight loss temperature (T₁₀) increased 16.0°C with only 0.3 wt % addition of TEVS‐GO and the thermal conductivity possessed a two‐fold increase, compared to the pure LSR. Furthermore, the mechanical properties were studied and results revealed that the TEVS‐GO/LSR composites with 0.3 wt % TEVS‐GO displayed a 2.3‐fold increase in tensile strength, a 2.79‐fold enhancement in tear strength, and a 1.97‐fold reinforcement in shear strength compared with the neat LSR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42582.     

Construction of porous cellulose tubes and the evaluations of mechanical properties and cytocompatibility

In this work, regenerated cellulose (RC) tubes with the porous structure were successfully fabricated for constructing the non-invasive detection platform of vascular microenvironment. Polyethylene oxide (PEO) as a porogen was applied to induce porous structure of cellulose tubes. Tensile and burst pressure tests were carried out to evaluate the effects of PEO molecular weight and amount on the mechanical properties of cellulose tubes. The results showed that tensile strength of RC tubes was increased with increasing PEO molecular weight. The compliance of cellulose tubes decreased with increasing the PEO content. When 120 kDa PEO was applied, the average tensile strength of RC tubes could reach 1.27 MPa. The maximum burst pressure and compliance of RC tubes could reach 488.25 ± 35 mmHg and 7.50 ± 3.7%/100 mmHg, respectively. Human umbilical vein endothelia cells (HUVECs) exhibited obvious proliferation on cellulose tubes, and the collagen coating further improve the biocompatibility. The incorporated collagen further improved adhesion of the cells and growth on cellulose tubes. This work provided a kind of cellulose-based tube material with potential application for the construction of the vitro vascular microenvironment.     

Influence of fly ash cenospheres on performance of coir fiber‐reinforced recycled high‐density polyethylene biocomposites

Recycled high‐density polyethylene (RHDPE)/coir fiber (CF)‐reinforced biocomposites were fabricated using melt blending technique in a twin‐screw extruder and the test specimens were prepared in an automatic injection molding machine. Variation in mechanical properties, crystallization behavior, water absorption, and thermal stability with the addition of fly ash cenospheres (FACS) in RHDPE/CF composites were investigated. It was observed that the tensile modulus, flexural strength, flexural modulus, and hardness properties of RHDPE increase with an increase in fiber loading from 10 to 30 wt %. Composites prepared using 30 wt % CF and 1 wt % MA‐g‐HDPE exhibited optimum mechanical performance with an increase in tensile modulus to 217%, flexural strength to 30%, flexural modulus to 97%, and hardness to 27% when compared with the RHDPE matrix. Addition of FACS results in a significant increase in the flexural modulus and hardness of the RHDPE/CF composites. Dynamic mechanical analysis tests of the RHDPE/CF/FACS biocomposites in presence of MA‐g‐HDPE revealed an increase in storage (E′) and loss (E″) modulus with reduction in damping factor (tan δ), confirming a strong influence between the fiber/FACS and MA‐g‐HDPE in the RHDPE matrix. Differential scanning calorimetry, thermogravimetric analysis thermograms also showed improved thermal properties in the composites when compared with RHDPE matrix. The main motivation of this study was to prepare a value added and low‐cost composite material with optimum properties from consumer and industrial wastes as matrix and filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42237.     

A commercial production route to prepare polymer‐based nanocomposites by unmodified multilayer graphene

In this study, we report our progress toward an effective method to prepare polyamide 6 (PA6)/multilayer graphene (MLG) nanocomposites via in situ polymerization. The thermal and mechanical properties of PA6 nanocomposites were investigated with low unmodified MLG content of 0.01–0.5 wt %. The dispersion of MLG sheets in the host matrix was studied in extensive detail while the properties of the resultant nanocomposites were systematically measured. Results indicate that the mechanical properties of the nanocomposites were significantly enhanced; the flexural modulus, flexural strength and impact strength increased by ～97%, ～69%, and ～76% relative to pristine PA6. Furthermore, the thermal stability of nanocomposites was enhanced and the weight loss temperature of PA6 was increased ～15°C at 0.5 wt % content of MLG. Moreover, incorporation of low loading of MLG can increase the crystallization speed of PA6 composites and promote the formation of the γ‐crystalline phase while also improving the crystallization temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42742.     

Kudzu fiber‐reinforced polypropylene composite

Kudzu fiber‐reinforced polypropylene composites were prepared, and their mechanical and thermal properties were determined. To enhance the adhesion between the kudzu fiber and the polypropylene matrix, maleic anhydride‐grafted polypropylene (MAPP) was used as a compatibilizer. A continuous improvement in both tensile modulus and tensile strength was observed up to a MAPP concentration of 35 wt %. Increases of 24 and 54% were obtained for tensile modulus and tensile strength, respectively. Scanning electron microscopy (SEM) showed improved dispersion and adhesion with MAPP. Fourier transform infrared (FTIR) spectroscopy showed an increase in hydrogen bonding with an increase in MAPP content. Differential scanning calorimetry (DSC) analysis indicated little change in the melting temperature of the composites with changes in MAPP content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1961–1969, 2002     

Effects of UV exposure and thermal history on properties of a preimidized photosensitive polyimide

The structure and properties of a preimidized photosensitive polyimide (Probimide PSPI, a copolyimide of benzophenonetetracarboxylic dianhydride with alkyl groups substituted aromatic diamines) were studied with variations of UV exposure energy and bake temperature by means of wide angle X-ray diffraction, dynamic mechanical thermal analysis, stress-strain analysis, and residual stress analysis. The X-ray diffraction patterns patterns indicate that the PSPI is amorphous in the solid state. The T_g was 378°C ～ 410°C, depending upon the thermal history over the range of 350°C ～ 400°C. At the glass transition region, the dynamic storage modulus E′ was very sensitive to both i-line exposure energy and thermal history. However, the mechanical stress-strain behavior at room temperature was primarily dependent on the thermal history. The mechanical properties were 2.6 GPa ～ 2.9 GPa Young's modulus, 131 MPa ～ 168 MPa tensile strength, 10% ～ 12% yield strain, and 16% ～ 74% elongation at break, depending upon the baking or annealing. These dynamic and static mechanical properties indicate that on the PSPI backbone, crosslinks are formed thermally as well as photochemically. The thermal crosslinks might be formed through thermal liberation of the labile alkyl groups of aromatic diamine moieties and subsequent coupling of the radicals. The thermal degradation was also evidenced in the mechanical properties degraded by baking above 375°C or annealing above 350°C. In addition, during baking and cooling, the residual stress was dynamically measured on Si wafers as a function of temperature. The stress at room temperature was 48 MPa ～ 52 MPa for the PSPI films baked at 350°C or 400°C, regardless of i-line exposure.     

Electrical,physicomechanical, and X‐ray studies on ethylene‐vinyl acetate copolymer/polyaniline blends

The conductive blend consisting of ethylene‐vinyl acetate (EVA) and a polyaniline/p‐toluene sulfonic acid (PAn/TSA) complex were prepared by a thermal doping process using a Brabender plasticorder at 150°C. The conductivity, dielectric constant, dissipation factor, mechanical behavior, and structural aspects of these blends were investigated. A higher percentage of the PAn/TSA complex in the EVA matrix resulted in an increase in the electrical properties and a decrease in the mechanical properties like the tensile strength and percentage of elongation. These results were compared with the microcrystalline parameters of the blend obtained from X‐ray profile analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1730–1735, 2002     

Investigation on flammability of rigid polyurethane foam‐mineral fillers composite

This study investigates the incorporation of castor oil–based rigid polyurethane foam with mineral fillers feldspar or kaolinite clay in order to enhance the mechanical, thermal, and flame retardant properties. Influence of mineral fillers on the mechanical strength was characterized by compressive strength and flexural strength measurement. Thermogravimetric analysis (TGA) was performed to diagnose the changes in thermal properties, while cone calorimeter test was performed to ascertain the flame retardancy of the mineral filler–incorporated rigid polyurethane foam composites. Results showed that the foams incorporated with mineral filler demonstrated up to 182% increase in compressive strength and 351% increase in flexural strength. Thermal stability of these composite foams was also found to be enhanced on the incorporation of kaolinite clay filler with an increase in 5% weight loss temperature (T_5%) from 192°C to 260°C. Furthermore, peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decreased on the incorporation of mineral filler in the rigid polyurethane foam. So mineral fillers are ascertained as a potential filler to enhance the mechanical, thermal, and flame retardant behaviors of bio‐based rigid polyurethane foam composites.     

The characterization of organic modified clay and clay‐filled PMMA nanocomposite

Recently, polymer–clay hybrid materials have received considerable attention from both a fundamental research and application point of view. 1 - 3 This organic–inorganic hybrid, which contains a nanoscale dispersion of the layered silicates, is a material with greatly improved physical and mechanical characteristics. These nanocomposites are synthesized through in situ polymerization or direct intercalation of the organically modified layered silicate (OLS) into the polymer matrix. Thus, understanding the relationship between the molecular structure and the thermal stability (decomposition temperature, rate, and the degradation products) of the OLS is critical. In this study, modern thermal analysis techniques combined with infrared spectroscopy and mass spectrometry (TGA‐FTIR‐MS) were used to obtain information on the thermal stability and degradation products of organic modified clay. Furthermore, the thermal and mechanical properties of clay‐filled PMMA nanocomposites were determined by using TGA and DSC. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1702–1710, 2002     

Bismaleimide‐modified methyl‐di(phenylethynyl)silane blends and composites: Cure characteristics,thermal stability,and mechanical property

Reactive blends of organic‐inorganic hybrid monomer, methyl‐di(phenylethynyl)silane (MDPES) and a modified bismaleimide resin (BMI/DBA) have been prepared. The thermal and oxidative stabilities of MDPES‐BMI/DBA blends were characterized by thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis, dynamic mechanical analysis, and flexural strength retention at 240°C. Scanning electron microscopy was employed to study the surface morphology of MDPES‐BMI/DBA composite after thermal oxidative treatment. With the increase of concentration of BMI/DBA, flexural strength of composites increased from 78 to 331 MPa. The results showed that MDPES‐BMI/DBA blends exhibited excellent thermal and thermal oxidative properties, and the interface between MDPES and glass fiber was improved by the incorporation of BMI/DBA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of Heterocyclic Aramid Fiber Based on Solid‐Phase Cross‐Linking of Oligomers with Reactive End Group

Low compressive strength of aramid fiber is one of the major obstacles for its application in advanced composite materials. In this study, poly‐(benzimidazole‐terephthalamide) (PABI) fibers are fabricated by solid‐phase cross‐linking of corresponding oligomers end‐capped with norbornene anhydride (NA). Concentration of the spinning solution increases and apparent viscosity is reduced significantly through this method, which improves its processability. Reactivity and thermal stability of the NA group are measured by in situ Fourier transform infrared (FTIR) and thermogravimetric analysis and it shows high reactivity at 360 °C and adequate thermal stability under 400 °C. Results of solubility test and dynamic mechanical analysis indicate cross‐linking degree increases with decrease of molecular weight of the corresponding oligomer. Results of both 2D wide angle X‐ray diffraction and polarized FTIR illustrate orientation will be affected by cross‐linking and it decreases with the increase of cross‐linking degree. PABI fibers fabricated through this method can maintain outstanding mechanical properties and compressive strength is improved by 67% at most. Interestingly, interfacial shear strength of PABI fibers is improved by nearly 20% and damage between skin–core layers after debonding of fiber and resin is not observed.     

Effects of nanotube modification on the dielectric behaviors and mechanical properties of multiwall carbon nanotubes/epoxy composites

Multiwall carbon nanotubes (MWNTs) were modified by three methods, namely, oxidizing the tubes and opening both ends, filling the tubes with Ag, and grafting the tubes with hexamethylene diamine. Modified MWNTs/epoxy composites were prepared by melt‐mixing epoxy resin with the tubes. Transmission electron microscope images showed that the modified MWNTs can be dispersed in the epoxy matrix homogeneously. The dielectric behaviors and mechanical properties of the composites were investigated. The dielectric and mechanical properties of the modified MWNTs/epoxy composites were considerably improved compared with those of the epoxy matrix. The tensile strengths of the Ag‐filled, opened, and grafted MWNTs composites at the same filler content of 1.1 wt% were higher by ～30.5%, 35.6%, and 27.4%, respectively, than that of neat epoxy. The Izod notched impact strength of the grafted MWNTs/epoxy composite with filler content of 1.1 wt% was approximately four times higher than that of neat epoxy. A dielectric constant of ～150 of the composite with 1.1 wt% Ag‐filled nanotubes was observed in the low‐frequency range, which was ～40 times higher than that of the epoxy matrix. The proper modification of nanotubes provides a way to improve the properties of the polymer‐based composites. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Improvement of thermal properties of biodegradable polymer poly(3‐hydroxybutyrate) by modification with acryloyloxyethyl isocyanate

Poly(3‐hydroxybutyrate) (PHB) is one type of polyhydroxyalkanoates often used as a biomedical material due to its biodegradable and biocompatible nature. However, the mechanical and thermal properties of PHB must be improved before it can be used in a wider variety of biomedical applications. To improve the thermal properties of biodegradable PHB, various reaction conditions were studied. Results demonstrate that reacting PHB with acryloyloxyethyl isocyanate (AOI), a monomer with dual functional groups, produces a modified PHB material with markedly improved thermal properties. The 10% thermal decomposition temperature for PHB modified with 5% AOI was 297°C, which was 26.8°C higher than original PHB. The T_g also increased from 4°C to around 30°C for AOI‐modified materials. Additionally, due to the poly(ester‐urethane) structure and hydrogen bonding of polymer materials, the mechanical properties also improved. Thus, this modified PHB biodegradable polymer may have greater application as a biomedical material due to its enhanced thermal and mechanical properties. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Synthesis of silane‐grafted ethylene vinyl acetate copolymer and its application to compatibilize the blend of ethylene‐propylene‐diene copolymer and silicone rubber

Vinyltrimethoxysilane‐grafted ethylene vinyl acetate copolymer (EVA‐g‐VTMS) was synthesized and applied to compatibilize ethylene‐propylene‐diene copolymer (EPDM)/methyl vinyl silicone rubber (MVQ) blends. The silane‐grafting was successfully proved by differential scanning calorimetry, FTIR spectroscopy and XPS spectroscopy. The additive amount of the compatibilizer (EVA‐g‐VTMS) was optimized to be 10 phr (parts per hundred of rubber in weight) based on analysis of scanning electron microscopy, mechanical properties, aging properties, dynamic mechanical properties, rheological properties and thermal properties. Compared with the blend without EVA‐g‐VTMS, results show that the blend with 10 phr of EVA‐g‐VTMS exhibits the finest morphology. Tensile strength, elongation at break, modulus at 100% elongation, tear strength and TE index increase by 82.5%, 16.9%, 60.0%, 40.9%, and 41.9%, respectively. Dynamic mechanical analysis reveals storage modulus increase and glass transition temperatures of EPDM and MVQ move closer to each other. Rheological analysis shows a decrease in complex modulus and complex viscosity, and the processibility of the blend was improved. Furthermore, thermogravimetric analysis shows enhancement of thermal stability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Thermal shock resistance and hoop strength of triplex silicon carbide composite tubes

Multi‐layered SiC composites have been considered as a nuclear fuel cladding material of light water reactors, LWRs, because of their excellent high temperature strength and corrosion resistance under accident conditions. During a design basis accident of a LWR such as a loss‐of‐coolant accident, the peak temperature of the fuel clad rapidly increases as the production of decay heat continues. The emergency core cooling systems then automatically supply the reactor core with emergency cooling water. The fuel clad consequently suffers from thermal shock. In this study, the structural integrity of multi‐layered SiC composite tubes after thermal shock was investigated. Several kinds of multi‐layered SiC composite tubes consisting of CVD SiC and CVI SiC_f/SiC were water‐quenched from 1200°C to room temperature. The triplex SiC composite tube retained its tubular geometry during quenching. The strength degradation after thermal shock was <13% for the specimens with a PyC interphase. The residual stress distribution within the tubes during thermal shock was evaluated by a finite element method.     

Enhancement of physical properties of electroactive polyimide nanocomposites by addition of graphene nanosheets

Electroactive polyimide (EPI) nanocomposites with amino‐capped aniline trimer and 4′‐(4,4′‐isopropylidene‐diphenoxy)bis(phthalic anhydride) as monomers, and functionalized with carboxyl‐graphene nanosheets, were prepared by thermal imidization. The as‐prepared electroactive polyimide/graphene nanocomposite (EPGN) materials were then characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. In situ monitoring of the redox behavior of the as‐prepared EPGN materials was performed by cyclic voltammetry studies. The effects of material composition on the mechanical, thermal, thermal transport, dielectric and molecular barrier properties of EPGN membranes were investigated by dynamic mechanical analysis, TGA, DSC, the transient plane source technique, LCR meter and gas permeability analyzer, respectively. It should be noted that all the properties of the EPGN membranes were found to improve substantially over those of non‐electroactive polyimide and EPI. For example, upon loading of 1 wt% graphene, EPGN membranes were found to have an increase of over 20%, 5%, 65% and 20% in mechanical strength, thermal stability, thermal conductivity and dielectric constant, respectively, and a reduction of over 20% in gas permeability. © 2013 Society of Chemical Industry