The state of water in the series of sulfonated poly (phthalazinone ether sulfone ketone) (SPPESK) proton exchange membranes

The different states of water in a series of SPPESK membranes, including sulfonated poly (phthalazinone ether sulfone ketone) (SPPESK) membrane, cross-linked (XL) SPPESK membrane and SPPESK/polyacrylic acid (PAA) semi-interpenetrating polymer network (sIPN) membrane were investigated by low temperature differential scanning calorimetry (DSC) measurements. Only one melting peak was observed for each DSC curve, therefore the free water cannot be distinguished from freezing bound water in the experimental condition. The melting temperature of the freezable water was found to decrease when the content of the freezable water reduced. The content of non-freezing bound water decreased with the increase in total water uptake in each type of the membranes. It indicates that the total water uptake cannot exactly reveal the ability of tight water retention of the membranes. As compared with SPPESK/PAA membrane, SPPESK and XL-SPPESK membranes presented a higher ability of water retention because of higher content of non-freezing bound water measured. A schematic structural model is given to explain the interrelation of distribution of ionic groups (hydrophilic groups) and structure of polymers to the content of non-freezing bound water.     

水在聚乙烯醇/水体系中的状态及氢键作用

水在聚乙烯醇(PVA)中的状态直接影响PVA的热塑加工.采用DSC和Raman光谱研究了水含量对其在PVA中的状态及氢键作用的影响.结果表明:水在PVA中以3种状态存在,随水含量增加,非冻结合水比例减小,可冻结合水和自由水比例增加.通过高斯分峰可将Raman光谱水的羟基伸缩振动峰分为5种羟基振动峰叠加,分别代表多氢键结合水分子的羟基对称与反对称伸缩振动,双氢键结合水分子羟基伸缩振动,单氢键结合水分子羟基伸缩振动,无氢键或弱氢键相互作用水分子的羟基伸缩振动.水含量增加,单氢键结合与多氢键结合水分子含量增加,而双氢键结合与无氢键结合水分子含量减少.     

PVA水凝胶中水的状态研究

用环氧氯丙烷作交联剂,制备了聚乙烯醇（PVA）亲水水凝胶。并用示差扫描量热法（DSC）对不同含水量的此种亲水水凝胶进行了测试,获得了各种状态水进入水凝胶聚合物网络体系的先后顺序情况,并研究了PVA水凝胶中三种状态水的含量随水凝胶含水量的变化而变化的规律。     

The investigation on states of water in different hydrophilic polymers by DSC and FTIR

The interaction between polymers and water in four hydrophilic polymer aqueous solutions were investigated by DSC and FTIR. DSC result shows that the different hydrophilic polymer/water mixtures have various water calorimetric behaviors in the melting temperature range of freezable bound water as well as free water. The melting temperature of freezable water and the amount of non-freezable water in the mixtures vary with the change of chemical structure of polymers. The melting point of the freezable bound water doesn’t change with the water content, revealing that water bound weakly to polymer chains can form a stable crystalline structure at high water content. For the three hydrophilic polymer/water mixtures with C=O group, the weight ratio of non-freezable water to polymers is constant, but varies with polymer chemical structures. The FTIR spectra confirmed the formation of the hydrogen bonds and it was found that there exist different states of water based on various strengths of hydrogen bonds. The OH stretching bands indicated the fraction of strongly bound water decreases with increasing water content. It was concluded that at least in hydrophilic polymer aqueous solutions with polar sites in polymer chains, the formation of non-freezable water is ascribed to the hydrogen bonds between hydrophilic polymers and water molecules. Different strengths of hydrogen bonds can affect the thermal behaviors of water in the hydrophilic polymer/water mixtures.     

Structure and mechanical properties of nanodispersed fibrous silicate‐reinforced ethylene–propylene–diene monomer nanocomposites

In this study, ethylene–propylene–diene monomer (EPDM)/fibrillar silicate (FS) nanocomposites were successfully prepared by mechanically blending EPDM with FS, which was modified by silane coupling agent KH570 containing methacryloxy group. The effects of silane content and modified FS on the dispersion of FS and mechanical properties of the composites were investigated. The impact of water in FS on mechanical properties of the composites was also evaluated. The results showed that modified FS could be dissociated into nanofibers dispersing evenly in the EPDM matrix by increasing substantially the loading of silane through the mechanical blending. The optimum loading level of silane coupling agent was up to 24 phr/100 phr FS. Silane KH570 could improve the dispersion of FS and strengthen nanofibers–rubber interfacial adhesion even at the loading of as high as 50 phr FS, making FS to exhibit excellent reinforcement to EPDM. Too much FS could not be completely dissociated into nanofibers, slowing down further improvement. The EPDM/FS composites exhibited the similar stress–strain behavior and obvious mechanical anisotropy with short microfiber‐reinforced rubber composites. With the increase in silane coupling agent and modified FS, the number of nanofibers increased because of the exfoliation of FS microparticles; thus, the mechanical behaviors would become more obvious. It was suggested that the free water in FS should be removed before mechanically blending EPDM with FS because it obviously affected the tensile properties of the composites. Regardless of whether FS was dried or modified, the EPDM/FS composites changed little in tensile strength after soaked in hot water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and NMR investigation of the change in the states of water caused by volume phase transition of gelatin gel

The occurrence of volume phase transition (VPT) of a polymer gel is often accompanied by the loss of water. In view of the fact that few studies have been made on the change in different states of water during VPT, in this paper, DSC and NMR are used to check the variation in states of water during VPT of glutaraldehyde crosslinked gelatin gel caused by the variation in composition of water–acetone mixture. The results indicate that the volume of gel collapses at 50 % acetone concentration. The contents of free, intermediate and bound water absorbed by gelatin gel decrease with an increase in the amount of acetone. At 50 % and 60 % acetone content, free water disappears; because acetone accounts for 70 % and 85 %, there remains only bound water. Near VPT the relative content of bound water to total water increases sharply. The spin–lattice relaxation times (T₁) determined by NMR show that the T₁ values of intermediate and bound water, respectively, decrease by approximately four and ten times compared with that of free water. Before VPT, most of the water is freezable and highly mobile. After VPT, bound water gradually plays a dominant role in the mobility of water in the gel. The findings are helpful in understanding the dehydration process of protein induced by poor solvent. © 2000 Society of Chemical Industry     

Studies on the preparation and mechanical properties of esthetic polymeric dental restoratives using silane treated silica microfiller via freeze‐drying

Polymeric dental restorative composites were prepared using silica filler where the surface was treated with γ‐methacryloxypropyltrimethoxysilane and decanted solvents by the freeze‐drying method. This treatment improved the miscibility of the filler with 2,2′‐bis‐[4‐(methacryloxy‐2‐hydrbxypropoxy)‐phenyl]‐propane/triethyl‐eneglycoldimethacrylate resin matrix and enhanced the esthetic properties of the composite. Diametral tensile strength (DTS) and flexural strength (FS) of the dental composite were measured, and the effect of drying methods in the surface treatment of filler on the mechanical properties of the composite was also investigated. Dental restorative composites prepared by the freeze‐drying method showed substantially higher DTS and FS values than those prepared by the conventional heat‐drying method. This resulted in increasing the loading percentage of filler in the resin matrix, and thereby, DTS values were increased dramatically. Dispersion of silica filler in the resin matrix and surface characteristics were examined by scanning electron microscopy. Various esthetic grades of dental composites were successfully prepared using iron oxide pigments, and its Hunter L. a. b. values of vita color‐shade were also investigated.     

Dynamic rheology and morphology of HDPE‐fumed silica composites: Effect of interface modification

In the present study, high density polyethylene (HDPE)‐based composites containing different amounts of fumed silica (FS) were prepared by melt compounding in a corotating twin screw extruder. Polyethylene‐g‐maleic anhydride copolymer (PE‐g‐MA) containing 1 wt% maleic anhydride was used for interface modification between filler and polymer. The interaction between the surface hydroxyl groups of fumed silica nanoparticles with maleic anhydride groups of PE‐g‐MA led to a finer dispersion of the filler in the HDPE matrix. The terminal complex viscosity and terminal storage modulus were highest at 1 wt% filler loading due to widely spread network formation by FS nanoparticles. This filler network plausibly got disturbed at higher filler content and/or interface modification which was reflected in their stress relaxation behavior also. The dynamic rheological behavior of the composites was explained in terms of morphological observations. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Study of matrix–filler interaction through correlations between structural and viscoelastic properties of carbonous-filler/polymer-matrix composites

Polymer matrix composites reinforced with carbonous fillers are of significant commercial importance thanks to their vast application base. As the performance of such composites largely depends on matrix–filler interaction, the present study is focused on the impact of surface chemical states of polymer matrix and carbonous filler on the viscoelastic performance of the composites. Here we report investigation of the filler–matrix interface through spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Viscoelastic properties of various polymer matrix composites prepared by varying the filler volume fraction and/or the matrix/filler type have been studied through dynamic mechanical thermal analysis. Further, to understand the matrix–filler interaction, correlations between viscoelastic parameters and various structural parameters such as the surface area of filler and the surface chemical states of filler/matrix obtained through XPS have been studied. Strong correlations between the viscoelastic parameters and the matrix/filler surface chemical states have been observed, suggesting the XPS as an important tool to study the role of the surface functionalities present on the matrix/filler surface to define the matrix–filler interaction. The filler surface functionalities such as C bound O have been found more compatible with the polymers having aromatic ring in the repeat unit. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48660.     

EFFECTS OF GLASS MICROFILLERS ON THE WATER-TRANSPORT BEHAVIOR OF POLYURETHANE COMPOSITES

Glass microspheres with unique composition and diameter, and modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the liquid transport properties of the PU composites. Transport properties such as diffusion, permeability, and sorption coefficient were measured on various filler-filled PU composites at three different temperatures. These temperature-dependent parameters were used to provide a quantitative way to examine the effects of filler loading and the surface properties on the improvement of the water transport properties of PU composites. Results show that due to trapping at interfacial boundaries between filler and polymer, a high water affinity and large space for water activity is expected inside all the filler-filled composites. As a result, lower water diffusion (or high water resistivity) was found among all the filler-filled composites compared to that of filler-free composites. Besides, the more filler present in the composite, the longer the paths of the water molecules within the composites as the water penetration proceeds. Thus, lower diffusion coefficient values were observed for composites with large amounts of filler addition.     

Damping behavior of wood filled polypropylene composites

The damping coefficient (tanδ) of wood flour filled polypropylene composites, having varying filler concentrations were measured using the free vibration decay of disk‐shaped specimen, vibrating in flexural vibration mode. The damping coefficients decreased with the increase of filler load in composites. There was no significant difference in damping behavior of composites with and without compatiblizer at low filler level (upto 30%). At higher filler loading (>30%), composites with compatiblizer had lower damping coefficient suggesting improved interfacial adhesion between wood and polypropylene. The damping in composite is attributed to the damping because of the composite constituents and damping at the interface. The damping because of interface was estimated using a model and was found to increase with the increase in filler loading. At higher filler content, damping due to interface in composites with compatiblizer was significantly lower than in composites without compatiblizer suggesting a better interfacial adhesion between the wood filler and polypropylene matrix with compatiblizer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Relationship between hydrogen bonding and bound water in polyhydroxystyrene derivatives

Crystallization of water sorbed on polyhydroxystyrene was studied by differential scanning calorimetry (d.s.c.). Two exothermic peaks of crystallization of water sorbed on the polymer were observed. One was a sharp peak (Peak I) observed at about 255 K in a d.s.c. curve; the other was a small broad peak (Peak II) observed at about 235 K. Judging from the amount of water calculated from the enthalpies of crystallization, there seems also to be some non-freezing water which does not crystallize. Therefore, we have categorized water sorbed on the polymer into three different kinds: free water (Peak I), freezable bound water (Peak II) and non-freezing water. The bound water content increases as the amount of hydroxyl groups in the polymer increases. Moreover, the maximum amount of water bound to a monomer unit of the polymer is about 0.7 mol. These facts indicate that there is less than a mole of bound water attached to a hydroxyl group and that part of this bound water does not crystallize. The bound water content estimated above was found to agree well with the critical water content, which was estimated from the decrease in the glass transition temperature of water sorbed polymers. Consequently, the bound water is defined as the water molecules which act to break the intermolecular hydrogen bonding and then are attached closely to hydroxyl groups of polymers. Thus, the bound water content evaluated from d.s.c. correlates with the degree of hydrogen bonding of polymers.     

Preparation and properties of poly(dimethyl siloxane)–colloidal silica/functionalized colloidal silica nanocomposites

Aqueous spherical colloidal silica (CS) particles with a diameter of 15 ± 5 nm were modified with three different types of monofunctional silane coupling agents to prepare functionalized colloidal silica (FCS) particles. The effects of the surface chemistry of the FCS were studied as a function of the CS/FCS loading in the poly(dimethyl siloxane) (PDMS) polymer. The prepared PDMS–CS/FCS composites were investigated for their physical properties both in the cured and uncured states. The extent of filler–filler and filler–polymer interactions was found to vary with the type of functionalizing agent used to treat the surface of the CS. The filler–filler interaction appeared to be predominant in the PDMS–CS composites, and improved filler–polymer interaction was indicated in the case of the PDMS–FCS composites. The composites containing CS treated with methyltrimethoxysilane exhibited relatively better optical and mechanical properties compared to the other PDMS–FCS composites. This study highlighted the importance of judiciously choosing functionalizing agents to achieve PDMS–FCS composites with predetermined optical and mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

DSC studies on states of water in crosslinked poly(methyl methacrylate-co-n-vinyl-2-pyrrolidone) hydrogels

Mixtures of methyl methacrylate (MMA) with N-vinyl-2-pyrrolidone (VP) of various composition in the presence of fixed concentration of ethylene glycol dimethacrylate (EDMA) have been copolymerized to 100% conversion by γ-irradiation. The resultant solid xerogels were swollen in water to yield hydrogels of equilibrium water contents ranging from 15 to 76wt%. The state of water in the poly(MMA-co-VP) hydrogels has been studied by differential scanning calorimetry (DSC) and the percentages of free freezing, freezable bound and nonfreezing water were found to vary with the xerogel composition, i.e. the degree of hydration of the hydrogels. At low equilibrium swelling, most of the water exists as a non-freezing type, whereas at higher equilibrium swelling the majority of water exists as free freezing water. The maximum number of non-freezing water molecules per VP unit in the hydrogel is about 7.5.     

Non equilibrium annealing behavior of poly(vinyl acetate)

The water absorbed by poly(vinyl acetate), PVAc, at 23°C was found in two states. The first, which can account for up to 4 weight percent, was bound to the polymer. The second was in a freezable or clustered form. The latter type of water had no effect on PVAc's glass temperature, whereas, the former kind plasticized T_g. In annealing studies, the enthalpic and dielectric response of PVAc when held at a fixed temperature increment, ΔT, below T_g, was observed to be independent of the amount of bound water. The time dependence of the shift in the dielectric relaxation spectrum and the recovery of the enthalpy towards its equilibrium value as PVAc approached its equilibrium glassy state from a lower temperature as compared to a higher temperature was initially slower. This delayed response to expansion was of the order of the polymer's average relaxation time at the lower temperature. A model was proposed to explain this asymmetric behavior based upon changes in the polymer's free volume as well as its occupied volume.     

Jatropha deoiled cake filler‐reinforced medium‐density polyethylene biocomposites: Effect of filler loading and coupling agent on the mechanical,dynamic mechanical and morphological properties

This work focuses on the performance of Jatropha deoiled cake (JOC) as filler for medium‐density polyethylene. The biocomposites were prepared using a melt‐compounding technique. Maleated polyethylene (MPE) was used as a reactive additive to promote polymer/filler interfacial adhesion. The mechanical, thermodynamic mechanical and morphological properties of the resultant composites were investigated. The results show that the incorporation of JOC into the matrix reduced tensile, flexural, and impact strengths compared with the pure matrix. Moreover, tensile and flexural moduli were increased. The composites prepared with MPE had better mechanical properties and lower water uptake, indicating an enhancement in the interfacial interaction between JOC and polyethylene systems. The storage modulus was increased by the increase in filler loading and decreased when MPE was used. The composites loss modulus curves revealed two glass transitions indicating partial miscible blends. Scanning electron microscopy analysis for maleated composites showed a relatively homogeneous morphology with few left cavities, and the filler particle size is smaller compared to nontreated composites. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Filler-immobilization assisted designing of hydroxyapatite and silica/ hydroxyapatite filled acrylate based dental restorative composites: Comparative evaluation of quasi-static and dynamic mechanical properties

The comparative effect of filler combinations on the quasi-static and thermo-mechanical properties of light cured acrylate based restorative composites is addressed in the study. Two series of acrylate based restorative composites filled with hydroxyapatite (Hap) and silica/Hap combination were prepared. FTIR spectroscopy showed the filler-assisted functional interference with the chemical structure of the resin, whereas SEM–EDX revealed the state of micro-dispersion/distribution morphology of the filled composites. The silica/Hap combination filled (micro-hybrid) composites with 30 wt.-% filler showed highest compressive strength (CS) and composites with 20 wt.-% filler showed highest diametral tensile strength (DTS) as well as flexural strength (FS). Dynamic mechanical properties revealed reinforcement effectiveness correlated to extent of filler immobilization effects estimated from Kerner equation. Our study conceptually establishes the possibility of manipulating the mechanical and thermo-mechanical strength requirements, by catering to the extent of filler induced bulk hardening contributions, as characterized by immobilized volume fraction of the polymer chains. It was imperatively deduced that at very high amount of overall filler content (e.g. > 50 wt.-%) the reinforcement effectiveness is filler-controlled whereas the same extent of effectiveness may be obtained by manipulating the filler induced immobilization effects (e.g. < 20 wt. - %).     

Preparation and properties of reduced graphene oxide/fused silica composites

An in situ strategy for fabrication of reduced graphene oxide/fused silica (rGO/FS) composites using 3-aminopropyltriethoxysilane as surfactant is reported. GO nanosheets were bound to FS particles by an electrostatic assembly between ultra thin negatively charged GO sheets and positively charged amino-modified FS particles. After spark plasma sintering, rGO/FS bulk composites have been produced from the GO and FS composite particles with GO being reduced to rGO in vacuum at high temperatures. Results show that rGO sheets were well dispersed in the matrix, and conductivity of these rGO/FS composites at room temperature was strongly dependent on the rGO nanosheet concentration. i.e., the conductivity of rGO/FS was increased to 10⁻⁴ S/cm when a conducting network was formed inside the composites. The effect of GO nanosheets on the mechanical properties of rGO/FS bulk composites was also investigated. The addition of 1 wt.% GO sheets to FS resulted in 72% increase in Vickers hardness, indicating the stress transfering from the FS matrix to the rigid rGO sheets. With the same rGO content, the fracture toughness of the as-prepared composites was increased by 74%. The main toughening mechanisms were thought to be crack deflection, crack branching, pulling-out and bridging of the rGO sheets.     

The states of water in cellulose acetate membranes

Differential scanning calorimetric melting endotherms of wet and half-dried cellulose acetate membranes and salt distribution coefficients were studied to clarify the states of water in membranes. We have suggested that (a) there are four states of water in cellulose acetate membranes; (b) these states of water are those of completely free water, free water very weakly interacting with polymer, bound water which can contain salts, and bound water which rejects salts; (c) the semipermeability of membranes depends on the ratio of four states of water in membranes.     

The Physical Properties of Oil Palm Empty Fruit Bunch (EFB) Composites Made from Various Thermoplastics

Abstract

Oil palm empty fruit bunch (EFB)-based composites were produced using different types of thermoplastic as matrices. The composites were produced by using an internal mixer. The mechanical and water absorption properties of composites were investigated. Overall, the incorporation of EFB into the polymer matrix has resulted in the reduction of flexural strength. The poor performance has been attributed to the poor filler-matrix interaction. Both flexural and tensile modulus of PE and PP composites have been improved upon the addition of fillers, however, both PS and PVC composites showed a decreasing trend. Tensile strength and elongation at break results for all composites have been reduced as the result of incorporation of filler. This has been attributed to the poor filler-matrix interaction or compatibility, size irregularity and also decreased ductile deformation. Water absorption and thickness swelling increased as the filler loading is increased. This has been attributed to the presence of hyrophillic hydroxyl groups of the filler.