Excellent Dimensional Stability Research Articles

Fabrication and properties of glass cloth reinforced multifunctional acrylic polymer substrate

Transparent glass cloth reinforced composite films were fabricated by ultraviolet (UV) light which induced chemical crosslinking of composite materials consisting of glass cloth and UV curable resin in film state. UV curable resin has been recognized to be the general trend of transparent glass cloth reinforced plastic (GCRP) resins because of its excellent heat resistance and chemical stability resulted from the dense network structure by UV curing of oligomers and monomers. But when GCRP is fabricated by UV curing of matrix resin, there exist three different refractive indices from cured resin, uncured resin, and glass cloth. To minimize uncured matrix resin and improve the transmittance of GCRP, the composite films were treated by heat after UV curing. As a result of heat treatment, optical properties of the composite films were enhanced and the excellent thermal and dimensional stability at the high temperature more than 300 °C were achieved.

Development of the fire retardant glass fabric/carbonized phenolic composite

Because fiber reinforced polymeric composite materials have the advantages of high specific strength and stiffness, their potential for replacing concrete, aluminum and steel. However, the poor fire resistance of fiber reinforced polymeric composite materials is one of the obstacles for their applications.In this study, a fire retardant glass fabric/carbonized phenolic composite was developed using the carbonization of the phenolic resin. Although the glass fiber is not combustible, it melts at approximately 800°C on exposure to fire, whereas the phenolic resin has good fire resistance with minimum smoke levels, excellent dimensional stability and thermal strength. Moreover, the phenolic resin is carbonized at high temperature (above 500°C), which prevents the spread of flames. However, shrinkage during the carbonization process weakens its strength and stiffness.To improve the pristine- and post-fire mechanical properties of the glass fabric/phenolic composite, flame and silane treatments were applied to the glass fabrics. The carbonization and impregnation of the phenolic resin matrix of the composite was repeated several times to develop the glass fabric/carbonized phenolic composite, from which the post-fire tensile strength and the carbonized phenol matrix ratio were measured with respect to the number of carbonization processes.

A Study on Dimensional Stability and Thermal Performance of Superheated Steam Treated and Thermal Compressed Wood

Recently, wood is attracting attention as green building interior decoration material. When wood is used as building interior decoration material, excellent dimensional stability and thermal performance is required. In this study, superheated steam treatment process and thermal compression process were applied to flat sawn Pinus koraiensis wood panel in order to improve dimensional stability and thermal performance. According to results of this study, superheated steam treatment process and thermal compression process improve thermal performance and dimensional stability of wood, especially in tangential direction. The spring back in radial direction reduces the effect of thermal compression on dimensional stability of wood in radial direction.

Developing high-performance hybrid green composites

Abstract Particleboards made of a mixture of wood particles and short glass fibers as the core and two layers of woven jute fabric as skin layers were fabricated using a vacuum-assisted resin transfer mold. The modulus of rupture (MOR), modulus of elasticity (MOE), and internal bonding (IB) were evaluated as indicators of mechanical performance. The vertical density profile, water absorption, and thickness swelling were analyzed to evaluate the physical performance. The results revealed that the proposed panels have excellent mechanical properties as compared to commercial wood composites. The MOR, MOE, and IB values for commercial particleboard composites are 14.69 MPa, 2.54 GPa, and 0.53 MPa, respectively, whereas the MOR, MOE, and IB for the proposed hybrid structure with zero glass fibers and no skin were 18.04 MPa, 2.99 GPa, and 2.18 MPa. Higher values were obtained by adding short glass fibers or using woven jute fibers as skin or both. The results indicated that the proposed sandwich composites exhibited excellent water resistance and dimensional stability as compared to commercial wood composites. The results also showed that these hybrid green composites with enhanced performance could be used in the construction and automotive industries.

In-situ self-crosslinked sulfonated poly(arylene ether ketone) with alkyl side chain for enhanced performance

We successfully synthesized a novel self-crosslinkable, pendent sulfonated poly(arylene ether ketone) for proton exchange membranes with high proton conductivity, excellent dimensional stability, and extraordinary methanol resistance. The chemical structure of the self-crosslinkable polymer SQNPAEK-AC-x was analyzed by 1H NMR. Without using any catalysts or a separate cross-linker, crosslinked SC-SQNPAEK-x membranes can be obtained by thermal treatment. The crosslinked network greatly suppresses the swelling ratio as well as water uptake of the membrane, meanwhile keeping the proton conductivity of the membrane at a high level. The highest proton conductivity is achieved by SC-SQNPAEK-2.5 membrane with a conductivity of 0.220Scm−1 at 80°C after crosslinking, which is much higher than commercial Nafion 117 membrane under the same conditions. The low water uptake depresses methanol crossover, which results in low methanol permeability. Mechanical property and oxidation stability also increased. Overall, the superior performance of these self-crosslinked membranes demonstrates the potential application of these materials as polyelectrolytes for proton exchange membrane fuel cells (PEMFCs).

Rigid Polyurethane Foam: A Versatile Energy Efficient Material

Rigid polyurethane foam (RPUF) is typically prepared by the reaction of an isocyanate, such as methyl diphenyl diisocyanate (MDI) with a polyol blend. During the polymerization reaction, a blowing agent expands the reacting mixture. The finished product is a solid, cellular polymer with a high thermal resistance. RPUF is an outstanding material for different applications. It has many desirable properties such as low thermal conductivity, low density, low water absorption, low moisture permeability, excellent dimensional stability, high strength to weight ratio. So, it is the best insulating material for industrial buildings, cold storages, telecom and defense shelters due to low thermal conductivity, low density, low moisture permeability and high porosity. It works to reduce heating and cooling loss, improving the efficiency of the building envelope. Thus, RPUF insulation in building envelopes brings additional benefits in energy savings, resulting in lower energy bills and protecting the environment by cutting CO2 emissions.

Chairside technique for expediting indirect interim restorations

Figure 2. Hot melt adhesive-made flexible cast. The use of flexible casts and dies for the chairside fabrication of interim restorations has been reported to overcome the drawbacks of the direct technique and provide a safe and biocompatible fabrication process. Because of the elasticity of these casts, removing the interim restoration after complete setting is easy, and the integrity of the casts is maintained. Unlike stone casts, the flexible cast can be reused if a new interim restoration is needed later. Different elastomeric impression materials and consistencies have been used to make flexible casts. Although materials such as polyvinyl siloxane have excellent dimensional stability, they are relatively expensive and adhere to the already set impression material. For this reason, a second alginate impression is usually made to produce the flexible cast. To overcome these limitations, this article proposes the use of hot melt adhesive material (HMA) for the fabrication of flexible casts. HMA is a thermoplastic material usually supplied in sticks, which are melted using an electric gun. It typically consists of a base material such as an ethylene-vinyl acetate copolymer with additives such as wax, resins, plasticizers, and pigments. HMAs do not adhere to elastomeric impression materials. This allows easy separation of impressions made with any material, including polyvinyl siloxane without the need for a separating agent. Obtaining the flexible cast from the definitive impression eliminates the need for an additional impression, reduces the time needed for the procedure, and improves the accuracy of flexible cast details. HMAs are also less expensive than elastomeric impression materials.

Guanidine hydrochloride embedded polyurethanes as antimicrobial and absorptive wound dressing membranes with promising cytocompatibility

Preparation and assessments of novel absorptive wound dressing materials with efficient antimicrobial activity as well as very good cytocompatibility were described in this work. An amine terminated poly(hexamethylene guanidine hydrochloride) was prepared and used as curing agent of different epoxy-terminated polyurethane prepolymers. The structures of prepared materials were elucidated by evaluation of their 1H NMR and FTIR spectra. The recorded tensile strength of membranes confirmed the excellent dimensional stability of the film type dressings even at fully hydrated conditions. Therefore, these dressings could protect the wound bed from external forces during the healing period. The structurally optimized dressing membranes could preserve the desired moist environment over the wounded area, as a result of their balanced equilibrium, water absorption and water vapor transmission rate. Therefore, a very good condition for stimulation of self-healing of wound bed was attained. Also, owing to the presence of guanidine hydrochloride moieties embedded into the structure of dressings, efficient antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans were detected. In vitro cytotoxicity assay of the prepared dressings revealed cytocompatibility of these materials against fibroblast cells. Therefore, they could support cell growth and proliferation at the wounded area.

Anion exchange membranes based on tetra-quaternized poly(arylene ether ketone)

A series of novel tetra-quaternized poly(arylene ether ketone)s (QPAEK-x) with high densely quaternized pendants are investigated in this work. As polymer electrolyte precursors, the four benzyl units containing poly(arylene ether ketone)s are prepared from 4,4′-difluorobenzophenone, 4,4′-(hexafluoroisopropylidene) bisphenol and designed bisphenol monomer. Then, the objective ionomer is successfully obtained via free-radical bromination, followed by quaternization of the four benzyl units containing poly(arylene ether ketone)s. These anion exchange membranes show excellent dimensional stability, adequate thermal stability and high hydroxide conductivity, owing to the pendent quaternary ammonium structures concentrated on the side chain. The highest hydroxide conductivity (0.0653S cm−1) appears in QPAEK-0.8 (IEC=1.69mmolg−1), and the swelling ratio of length is 11.7% at 80°C. The suitable morphology is investigated using SAXS, which should be a possible reason for the enhancement.

A Comparison of Al(OH)3 and Mg(OH)2 as Inorganic Porogenic Agents for Alumina

Castable porous ceramics combine the high refractoriness of ceramics, the useful characteristics of porous materials and the straightforward installation of castable systems. In this study, particles of aluminium hydroxide (Al(OH)3) and magnesium hydroxide (Mg(OH)2) of similar average size were added separately to an alumina castable (up to 67 vol.-%). During thermal treatment (1100–1500°C), variations occurred in their porosity levels, mechanical properties, phase composition and microstructure. These were related to physical-chemical changes and Al2O3-MgO solid-state reactions. Both systems have potential to be technologically useful. AH-based structures showed intermediate levels of porosity (around 60%) and higher compression strength (above 10 MPa), which enable them to be employed as sintered lightweight aggregates for refractory insulating mortars. The MH-based castables, on the other hand, exhibited higher porosity levels (above 60%) and excellent dimensional stability. They can therefore be used as primary thermal insulators for long-life services at steelmaking, cement production and petrochemical plants.

A Novel Methodology to Synthesize Highly Conductive Anion Exchange Membranes.

Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH− conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH− conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology.

Research on the Application Properties of Tpe/Ommt as Mold Materials

The aim of this work was to select one type of polymer as an alternative to room-temperature-vulcanizated silicone rubber (RTV) which was used in the preparation of rubber molds. Thermoplastic elastomer (TPE) and its organo-montmorillonite (OMMT) filled composites were chosen as candidates. Their structure and properties were researched and compared. The properties such as tensile strength, elongation at break, dimensional stability, and thermal stability were studied. The composite with 1 wt% OMMT showed the highest tensile strength and elongation at break, 10.9 MPa and 1313.6%, which was 172.5% and 30.3% higher than that of pure RTV. In addition, this TPE composite exhibited excellent thermal and dimensional stability. At room temperature, the coefficient of linear expansion (COLE) and coefficient of volume expansion (COVE) of the TPE/OMMT-1 wt% was 2.3×10−5 and 7.2×10−4, respectively. This was 87% and 86% lower compared to that of pure RTV, 1.7×10−4 and 5.1×10−3. This dimensional stability was superior to the pure RTV, indicating this composite can be used as an alternative to RTV as mold material to improve the texture fineness of the culture stone. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used in the investigation of the microtopography of the TPE composites. It was revealed that the layered silicates exhibited partial exfoliation with the addition of 1 wt% OMMT in the matrix.

Effect of heat-treatment on stress relief and dimensional stability behavior of SiCp/Al composite with high SiC content

Abstract In this paper, the effects of heat treatment processes on microstructure, residual stress and dimensional stability of 70 vol.% SiC p /Al composites were investigated by using a field emission gun scanning electron microscope (SEM), the X-ray stress analyzer and the thermal cycling test method. The results showed that the matrix of the as-cast composite is in compression. After the solution-quenching (SQ), aging and thermal-cold cycling (TCC) treatment, the residual stress was reduced due to the plastic deformation of the matrix. With the increase in the numbers of the SQ treatment, the long rod Al(MnFe) 3 Si 2 phase and the blocky CuAl 2 phase decreased while the spheroidization of these intermetallics increased. The TCC treatment refined the size of these intermetallics. As the number of the TCC treatments is increased, the resistance to micro-plastic deformation of the composite was also enhanced. The composite, which experienced the three-step SQ and aging and 12 times TCC treatment, presented the optimum thermal stability. Its hysteresis strain achieved 0.26 × 10 − 5 , and remained constant during the second and third cycling tests. The excellent dimensional stability shows a promising potential to be used as mirror materials for preparing mirror substrates in industry.

Preparation and properties of film materials of poly(aryl ether ketone)-based phthalonitrile resins

A series of poly(aryl ether ketone) polymers (m-PAEK-CN) containing phthalonitrile were synthesized by a direct solution polycondensation and characterized by Fourier-transform infrared spectroscopy and hydrogen nuclear magnetic resonance. Thermal crosslinking of m-PAEK-CN, catalyzed by p-BAPS, was then performed via heating their films up to 350oC. Dynamic rheology results showed that the rate of diamine-catalyzed crosslink reaction could be easily controlled by varying the content of cyano groups in the polymer. The uncured synthesized polymers had good solubility, whereas the cured ones became insoluble in common organic solvents. Spectra measurement demonstrated the trimerization reaction of terminal cyano groups to form triazine rings. The resulting cured samples had higher glass transition temperatures, better thermal, and thermo-oxidative stability with high char yield than the uncured ones. Gel content measurements demonstrated that the cured polymers had high crosslinking density with significantly high gel content over 96.0%. Thermal mechanical analysis indicated that the cured phthalonitrile resins possessed excellent thermal mechanical properties and dimensional stability at increased temperatures. The tensile modulus and strength of the cured m-PAEK-CN increased up to 2101–2104 MPa and 96–100 MPa, respectively, which were about 21–23% and 32–56% higher than the uncured ones’. This kind of phthalonitrile resins may be used as a candidate for high-performance polymeric film materials. POLYM. ENG. SCI., 55:2313–2321, 2015. © 2015 Society of Plastics Engineers

Soluble sulfonated polybenzothiazoles containing naphthalene for use as proton exchange membranes

Two series of sulfonated polybenzothiazoles containing naphthalene, derived from either 2,2-bis(4-carboxyphenyl) hexafluoropropane (6FA) or 2,6-naphthalene dicarboxylic acid (NA) were synthesized by polycondensation with non-sulfonated monomer 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) and sulfonated monomer 4,8-disulfonyl-2,6-naphthalene dicarboxylic acid (DSNA). The sPBT-6FA series polymers containing DSNA were soluble in polar aprotic solvents such as dimethyl sulfoxide or 1-methyl-2-pyrrolidinone, whereas sPBT-NA65 with NA was not soluble in common polar aprotic solvents. Therefore, the incorporation of both the naphthalene and flexible hexafluoroisopropylidene units enhanced the solubility of the sPBT polymer series. The polymers were evaluated as proton exchange membranes and exhibited excellent dimensional stability, high thermal and oxidative stabilities, good mechanical properties, and high proton conductivities. The proton conductivities of sPBT-6FA65 were 0.25Scm−1 at 80°C in water and 0.018Scm−1 at 120°C under 35% RH.

A pragmatic approach to methyl methacrylate based solid polymer electrolyte processing: A case study for electrochromism

Development of inexpensive and flexible solid polymer electrolytes (SPEs) is critically important for the cost-effective electrochromic device (ECD) fabrication. The SPEs are also an integral part of the flexible ECDs which are projected to boost up the ECD's usability in several unexplored areas. Here we report the synthesis of polymethyl methacrylate (PMMA) based aprotic salt (LiClO4) containing SPEs, which are more or less electrochemically benign in the normal ECD operational voltage window. Experiments verified that the developed SPEs have good luminous clarity (transmittance>92%), high ionic conductivity of the order of 10−4S/cm and excellent dimensional stability, all of which are required for the ideal ECD operations. Impedance spectroscopy showed an enhancement in the ionic conductivity and decrease in the solid electrolyte interface (SEI) resistance with increasing salt loading. Two different device configurations using these SPEs were fabricated and then subjected to detailed electrochemical studies. Comprehensive analysis established long term cyclic durability of the SPEs. Prototype ECDs fabricated using these SPEs rendered excellent optical modulation and coloration reversibility.

Synthesis and properties of fluorene-containing sulfonated poly (ether ether ketone) as proton-exchange membrane for PEM fuel cell application

A series of sulfonated poly(ether ether ketone)s were successfully synthesized via nucleophilic displacement condensation. The membranes are accordingly cast from their DMSO solutions, and fully characterized by determining the ion-exchange capacity, water uptake, dimensional stabilities, proton conductivity and mechanical properties. Among membranes, the block-7c-3 was successfully synthesized by the reaction of Block-6c with chlorosulfonic acid, with the feed ratio of repeated unit to chlorosulfonic acid of 1:8. The experimental results show that the membrane from block-7c-3 has good mechanical, oxidative and dimensional stabilities together with high proton conductivity (5.15 × 10−2 Scm−1) at 80 °C under 100 % relative humidity. The membranes also possess excellent thermal and dimensional stabilities, in this respect, they are potential and promising proton conducting membrane material for PEM full cell applications.

Graft octa-sulfonated poly(arylene ether) for high performance proton exchange membrane

A novel octa-sulfonated poly(arylene ether) was combined with a longer hydrophobic backbone and grafted with ionic clusters, exhibiting high proton conductivity and excellent dimensional stability.

Enhanced proton conductivity of sulfonated poly(p-phenylene-co-aryl ether ketone) proton exchange membranes with controlled microblock structure

A new series of sulfonated poly(p-phenylene-co-aryl ether ketone)s (s, m, l-SPP-co-PAEKs) microblock polymers containing different hydrophobic units with precisely defined lengths have been prepared via the nickel (0) catalyzed coupling copolymerization and characterized to act as proton exchange membranes. By controlling the length and chemical structure of the hydrophobic units in the copolymers, these novel microblock polymers can exhibit well-developed nanophase morphologies and large length-scale of the ionic channels, resulting in the improvement of the proton conductivity in both the wet and dry state. Moreover, the membrane l-SPP-co-PAEK 1.80 with the largest hydrophobic micro-block length shows high proton conductivity, excellent dimensional stability, low glass-transition temperature (Tg), good oxidative stability and superior cell performance.

Bacterial cellulose nanofibrous membrane as thermal stable separator for lithium-ion batteries

Thermal shrinkage is a severe problem for the conventional polyolefin separators. In this work, we report the excellent performance of bacterial cellulose (BC) nanofibrous membranes as separators for lithium (Li) ion batteries. Properties of BC separator including morphology, ionic conductivity, electrochemical stability, thermal stability, mechanical strength and battery charge–discharge performance are characterized and compared to a commercial separator membrane (Celgard® 2325). Because of the unique fibrous and cross-linked three-dimensional network structure, BC separator shows excellent dimensional stability up to 180 °C, good ionic conductivity and competitive battery performance.