Moisture Absorption Characteristics Research Articles

Mechanical, morphological and biodegradation studies of microwave processed nanostructured blends of some bio-based oil epoxies with poly (vinyl alcohol)

Bioresource based blends exploit the synergy between polymers derived from renewable resource and commercial polymers to obtain desirable physical, mechanical, and biodegradable properties. With the aim to develop a sustainable resource based biodegradable mulch films, nanostructured blends of epoxies of linseed oil (LOE) and dehydrated castor oil (DCOE) with poly (vinyl alcohol) (PVA) were prepared in the weight ratios of 20/80, 50/50 and 80/20. Microwave-assisted blending was used for the synthesis of DCOE/LOE blends with PVA and the results were compared with conventional solution blending using FT-IR, TGA-DTA and optical measurements. The results revealed that microwave-assisted blending proved to be an efficient method for the formation of compatible blends in a short span of time as compared to conventional solution blending. Transmission electron microscopy (TEM) analysis of DCOE/PVA and LOE/PVA blends synthesized by microwave-assisted method confirmed the formation of a nanostructured blend. Scanning electron microscopy (SEM), respirometry and mechanical measurements were carried out to compare the morphology, biodegradability, and the mechanical strength of DCOE/PVA and LOE/PVA blends. It was observed that DCOE/PVA blends exhibited higher biodegradability, better mechanical properties, and lower moisture absorption characteristics as compared to LOE/PVA blends. The mechanical strength, moisture absorption, and biodegradability of these blends were also compared with blends of other bioresource based polymers such as sugarcane bagasse (SCB), waste gelation (WG), apple peal (AP), and starch/glycerol with PVA, as available from the cited literature in the text.

P‐78: DOE Approach to Elimination of Display Mura Induced by LGP Warpage in HTHH Environment

AbstractIn this article, the mura issue of LCD panel induced by LGP warpage in high temperature and high humidity (HTHH) environment is discussed. From experiments, it is validated that insufficient gap between LGP and plastic mold frame, housing, will lead to deform the LGP. Due to the LGP has high moisture absorption and low thermal stability characteristics, it is easy to have volume expansion occurred. Obviously, the elongation of LGP will compress housing, thus LGP warping causes mura while panel in display mode. Experimental design (DOE) method is thus performed to generate a mathematical model to predict the displacement of LGP caused by hygrothermal effect. Finally, from experiment results, it is approved that the mura phenomenon has been eliminated. Furthermore, the mathematical construction model can provide the suitable design tolerance in module design phase.

Ba(Mg 1/3Ta 2/3)O 3 filled PTFE composites for microwave substrate applications

Phase pure Ba(Mg 1/3Ta 2/3)O 3 (BMT) ceramic filler has been prepared through solid-state ceramic route and characterized using XRD. Planar BMT filled PTFE composites were fabricated through SMECH process comprising of Sigma Mixing, Extrusion, Calendering followed by Hot pressing. Morphology and filler distribution of the composites were studied using Scanning Electron Microscopic technique. The microwave dielectric properties of the composites at X-band were measured using waveguide cavity perturbation technique. BMT filled PTFE composite exhibits a dielectric constant of 6.7 with loss tangent 0.003 at optimum filler loading. Dielectric constant of the composites shows better matching with the theoretically predicted values using Litchnecker model. The moisture absorption characteristics of the samples were ascertained as per IPC-TM-650 2.6.2.1. The loss tangent of the PTFE/BMT composites was improved to 0.0018 while incorporating long range ordered BMT fillers.

Effect of nano- and micro-particle additions on moisture absorption in thixotropic room temperature cure epoxy-based adhesives for bonded-in timber connections

The in-situ bonding of pultruded fibre-reinforced plastic rods into timber structural members is a commonly used technique for making timber-to-timber connections and for the strengthening and repair of timber structures. Ideally, the adhesive should be thixotropic, shear thinning, room temperature cure, environmentally stable, solvent-free and applied without pressure. This study investigates the moisture absorption characteristics of three adhesives, specially formulated for bonded-in timber connections, where two of the adhesives are modified with nano- or micro-particles. The three adhesives are denoted as CB10TSS (standard adhesive), Albipox (standard adhesive with CTBN rubber additions) and Timberset (standard adhesive filled with ceramic particles). The aim of the additions is to improve the environmental stability of the standard adhesive as well as enhancing mechanical properties and raising the glass transition temperature. The effect of high temperatures and high humidity on the properties of the three adhesives was determined following conditioning at different combinations of temperature and relative humidity (20, 30 and 50 °C/95% RH) and soaking in water at 20 °C. In all cases the moisture uptake for the rubber-modified adhesive was less than for the standard adhesive, but the ceramic particle-filled adhesive exhibited the lowest moisture uptake overall. Exposure to humid environments at temperatures lower than T g resulted in water uptake characterized as Fickian, which had only a modest effect on properties. However, exposure to humid environments at temperatures higher than T g resulted in non-Fickian uptake of water and significant changes to the diffusion and permeability coefficients.

Effects of silane coatings in aqueous and non-aqueous media on the properties of magnesia filled PTFE laminates

Silane coated on magnesia particulates in isopropyl alcohol (IPA) medium, precluded the formation of brucite phase, which hitherto existed in silane coated on magnesia filler in aqueous medium. Both the types of coated MgO powders were separately filled in the PTFE matrix, and microwave flexible substrates were made by the process comprising of sigma mixing, extrusion, calendering and hot pressing (SMECH process). Filler content in the PTFE matrix was varied from 10 to 70 wt% and microstructures of the composites were analyzed using SEM technique. The dielectric properties of the planar substrates were measured at X-band using waveguide cavity perturbation technique. The IPC-TM-650 procedure was employed to evaluate the moisture absorption characteristics.

Preparation and microwave characterization of BaWO4 filled polytetrafluoroethylene laminates for microwave substrate applications

Phase pure BaWO4 ceramic filler has been prepared through solid state ceramic route. Planar BaWO4 filled Polytetrafluoroethylene (PTFE) composite substrates were fabricated through Sigma Mixing (SM), Extrusion (E), Calendering (C) followed by Hot pressing (H) (SMECH) processes. Morphology and filler distribution of the composites were analyzed using particle size analysis and scanning electron microscopy. The effect of BaWO4 ceramic filler content on the dielectric properties of the composites was measured at microwave frequency using X-band waveguide cavity perturbation technique. Optimum BaWO4 filler loading in the PTFE matrix has been found out as 74 wt%. The moisture absorption characteristics of the composite samples were ascertained as per IPC-TM-650 2.6.2.1 method. PTFE/BaWO4 composite exhibits a dielectric constant of 4.3 and a loss tangent of 0.004 at optimum filler loading.

Moisture Degradation of Cyanate Ester/S2 Glass Composite Insulation Systems

The fusion devices currently being developed present several challenges for magnet designers. One challenge lies within the electrical insulation, which must be able to withstand extreme temperatures, large shear and compressive stresses, high operating voltages, and high levels of incident radiation. To address the need for better performing insulation systems, Composite Technology Development (CTD), Inc. has developed CTD-403, a cyanate ester resin with increased radiation resistance, ease of processing and fabrication, low moisture absorption characteristics, and high mechanical and electrical strength at cryogenic and elevated temperatures. The moisture absorption trends of CTD-403/S2 glass composite insulation were studied. The effects of humidity exposure on interlaminar shear strength (ILSS), compressive strength, dielectric strength, and glass transition temperature were also studied. The saturation level of the insulation was seen to increase with the relative humidity of the aging environment. Fickian behavior was seen at room temperatures below 97% relative humidity exposure. Non-Fickian behavior was seen at elevated temperatures. Saturation levels after 6 months exposure were seen to be below typical epoxy-based insulation systems, averaging 0.5% weight gain. Degradation of mechanical and electrical properties was seen with increased humidity exposure and moisture absorption. ILSS showed an average retention rate of 75% after 6 months exposure. The compressive strength showed no decrease after 6 months exposure at room temperature, and show retention rates greater than 90% at 75°C/79% RH. An average dielectric strength of 98.6 kV/mm was seen for all specimens at room temperature (above 90% retention) after 6 months exposure.

Effect of moisture absorption on the mechanical properties of randomly oriented natural fibers/polyester hybrid composite

In this work, the variation of mechanical properties such as tensile, flexural, and impact strengths of roselle and sisal fibers hybrid polyester composite at dry and wet conditions were studied. The composites of roselle/sisal polyester-based hybrid composites with different weight% of fibers were prepared. Roselle and sisal fibers at a ratio of 1:1 had been incorporated in unsaturated polyester resin at various fiber lengths. When the fiber content and length of the roselle and sisal fibers were increased, the tensile and flexural strength of the composite increased. When the samples were subjected to moisture environment, decrease in tensile and flexural strength was observed. The maximum percentage of strength reductions in tensile and flexural strength were observed for the composites having the fiber length of 150 mm and 30 wt% fiber content. For impact strength, it was with the composites of 20 wt% and 150 mm at wet conditions compared to dry conditions. The percentage of strength reductions increased with fiber content and length in wet conditions. A scatter in the impact strength values was identified on both the conditions. The moisture absorption characteristics of the natural fibers are very important to produce the natural fiber hybrid composite materials with the positive hybrid effect. The experimental results are compared with theoretical and empirical or statistical results and found to be in good agreement.

Experimental studies on the physico-chemical properties of banana fibre from various varieties

Natural cellulosic fibres from various varieties of banana plants such as Red Banana, Nendran, Rasthaly, Morris and Poovan have been extracted manually and the physico-chemical properties of these fibres are investigated. The tensile strength of these fibres varies from 176 MPa to 525 MPa. The untreated fibres have more tensile strength than the treated one. The thermal properties of these fibres are studied by Differential Scanning Calorimetry (DSC). Two DSC thermal peaks, one is around 25°C to 180°C and the other is around 155°C to 240°C, are noticed. The tensile strengths have a direct correlation with the area of the lower thermal peak (enthalpy) and activation energy of the DSC, and also with the moisture absorption characteristics. The FTIR shows characteristic bands corresponds to cellulose. The reflections of the X-ray fibre diffraction pattern recorded for the banana fibre have been correlated with the mechanical strength.

Microwave dielectric properties of PTFE/rutile nanocomposites

The effects of nano-size rutile filler on the microwave dielectric properties of PTFE composites were investigated and the results were compared with that of micron size rutile filled composites. Nano-size rutile powder was prepared through sol–gel route and the filled PTFE composites were fabricated through SMECH process. Different characterization techniques such as powder X-ray diffraction, SEM, BET, TEM and TG/DSC were employed to analyze the nature of ceramic filler. The dielectric properties of filled composites were evaluated at microwave frequency region using waveguide cavity perturbation technique. Different theoretical models have been employed to predict the variation of dielectric constant with respect to filler loading. The moisture absorption characteristics of nano-rutile filled PTFE composites were measured as per IPC-TM-650 2.6.2 standards. Composites show high dielectric constant at X-band frequency region with relatively high loss tangent compared to micron size counterpart.

Effects of Hygrothermal Conditions and UV Radiation on UHMWPE Fibers/Nanofiber—Epoxy Composites

Nanofiber-epoxy with reactive graphitic nanofibers (r-GNFs) showed an improvement in adhesion properties in ultra-high molecular weight polyethylene (UHMWPE) fibers/epoxy resin composite (bundle/tow form) in our previous experiments. In this study, moisture absorption characteristics of pure-epoxy, nanofiber-epoxy materials and their UHMWPE bundle composites were investigated under hygrothermal aging and UV conditions. For the matrix specimens the weight gain deviated from Fick's law, and thus, a two-stage model, which includes both diffusion and structural relaxation, was applied to analyze the moisture absorption behaviors. For the bundle composites the results indicated that the weight gain showed compatibility with Fick's law. The UHMWPE fiber composite with nanofiber-epoxy containing 0.3 wt% r-GNF loading resulted in the lowest rate of water absorption. Bundle composites were also exposed to accelerated UV aging conditions. The UV test results showed that the plateau stress and ultimate tensile strength of the bundle composites have been reduced. However, the ductility of the UHMWPE composites was increased due to the plasticization in hygrothermal aging tests.

Printed circuit boards for lead‐free soldering: materials and failure mechanisms

PurposeThis paper aims to evaluate the influence of previous exposure to moisture on delamination and formation of CAF (conductive anodic filament) in printed circuit boards used for lead‐free soldering.Design/methodology/approachThe moisture absorption and desorption characteristics of printed circuit boards were evaluated according to the IPC/JEDEC J‐STD‐020C standard for handling of moisture sensitive components. The CAF test was performed according to IPC‐TM‐650, Test Method 2.6.25.FindingsPrinted circuit boards used for lead‐free soldering must be treated as moisture sensitive components. Severe delamination occurred on test boards that had been exposed to JEDEC level 1 conditions prior to soldering, while no delamination was observed on boards exposed to level 3. Furthermore, previous moisture and thermal exposure had a strong influence on CAF formation. The insulation resistance dropped three decades in less than 15 h in the worst case.Research limitations/implicationsThere are considerable stresses on printed circuit boards in lead‐free soldering processes. The influence from materials and processes is very large on the CAF formation. Therefore, a useful strategy is to evaluate the CAF properties for each supplier and material.Originality/valueThe paper pin‐points previous moisture exposure as a very important factor for delamination and CAF formation and confirms that printed circuit boards must be treated as moisture sensitive components.

Moisture Absorption Characteristics of Porous Calcium Oxide Powders Produced by Calcination of Pulverized Limestone with Inorganic Salts Using a Powder-Particle Fluidized Bed

Small amounts of inorganic salts like sodium carbonate and calcium acetate were used as impregnants to pulverized limestone, which was then calcined in a powder-particle fluidized bed (PPFB) in nitrogen atmosphere at ambient pressure. Impregnation of 6-μm limestone with 1 mass% sodium carbonate and 1 mass% calcium acetate lowered the decomposition temperature by 30 K, making a 10% increase of calcination conversion at 1073 K. Additive impregnation involving calcium acetate produced macropores of larger than 50 nm in the reactant powders. Calcination with additive impregnation at 1073 K broadened the size of pores of the calcines to larger ones, newly producing 10-100 nm pores. These changes enhanced the ultimate moisture absorptivity by up to 20% as compared to the case without additive impregnation. However, calcination at 1173 K improved only the initial absorption rate.

Moisture absorption characteristics of food thickeners used for the management of swallowing dysfunctions

Six commercial food thickeners, based on starch, and guar and xanthan gums, were investigated for their moisture absorption properties. The thickeners were exposed to 100% relative humidity as well as soaked in water for selected time periods. The gum-based thickeners dissolved in water to yield 100% water solubility index. The water absorption index of the starch-based thickeners ranged from 14.7 to 18.0 g/g dry solids of thickener. The starch-based thickeners sorbed less moisture than the gum-based ones, with the xanthan gum-based thickeners having the highest sorptive ability on mass basis. The Peleg model was the most suitable (r2=0.966–0.997) of the sorption models investigated to describe the sorption data. The diffusion rate constant of the thickeners ranged from 8.7 to 13.5 day%−1, while the equilibrium moisture content was between 35.7 and 46.8%. The sorptive ability explained viscosity development in some of the thickeners, but was unsuitable in fully describing comparisons of the solutions viscosities of starch-based and xanthan gum-based thickeners.

The Effect of Rapid High Temperature Excursions on the Moisture Absorption and Dynamic Mechanical Properties of Carbon Fibre Epoxy Composite Materials

AbstractThe effect of elevated temperature excursions (thermal spiking) on the moisture absorption characteristics and dynamic mechanical properties of Cycom 8 HS carbon fibre epoxy laminates was investigated. Cured laminate samples were preconditioned (65d̀C, 95%R.H.) and these samples were exposed to various thermal spiking (150d̀C/2min) programmes. Dynamic mechanical thermal analysis (DMTA) techniques measured the changes in glass transition temperature (Tg) storage modulus (log E') and damping (Tan δ max) of the laminates as a result of exposure to these environments. The thermal spiking programme was shown to cause an increase in both the amount and rate of moisture absorption of the laminates. These increments were accompanied by a significant decrease in Tg, log E', and Tan δ max. Scanning Electron Microscopy (SEM) analysis also showed the progressive growth of both interlaminar and translaminar micro‐cracks as a result of thermal spiking.

Evaluation of the Film-Forming Property of Hydrogenated Rosin

The film-forming and coating properties of a new biomaterial, hydrogenated rosin (HR), is investigated in the present communication. Films produced by casting method are studied for mechanical, (tensile strength, elongation, and Young's modulus), water vapor transmission, and moisture absorption characteristics. Type of plasticizer and its concentration were observed to play an important role in modifying the film characteristics. Dibutyl sebacate (DBS), a hydrophobic plasticizer, was found to be suitable for development of flexible and smooth films. Film formulations plasticized with DBS were investigated for coating the drug layered nonpareil seeds where plasticization facilitated development of smooth and uniformly coated pellets. The increase in coat buildup, however, did not sustain the drug release significantly. The studies conclude that HR films promise utility as moisture-protective hydrophobic, film-coating materials.

Polymerized rosin: novel film forming polymer for drug delivery

Polymerized rosin (PR) a novel film forming polymer is characterized and investigated in the present study for its application in drug delivery. Films were produced by a casting/solvent evaporation method from plasticizer free and plasticizer containing solutions. Films prepared from different formulations were studied for their mechanical (tensile strength, percent elongation and Young's modulus), water vapour transmission and moisture absorption characteristics. Neat PR films were slightly brittle and posed the problem of breaking during handling. Hydrophobic plasticizers, dibutyl sebacate and tributyl citrate, improved the mechanical properties of free films with both the plasticizers showing significant effects on film elongation. Release of diclofenac sodium (model drug) from coated pellets was sustained with high coating levels. Concentration of plasticizer was found to affect the release profile. PR films plasticized with hydrophobic plasticizers could therefore be used in coating processes for the design of oral sustained delivery dosage forms.

Moisture absorption studies of fluorocarbon films deposited from pentafluoroethane and octafluorocyclobutane plasmas

The moisture absorption and diffusion characteristics of fluorocarbon films deposited from pentafluoroethane (PFE) and octafluorocyclobutane C4F8 plasmas are presented. The moisture absorption studies were carried out using a quartz crystal microbalance in a controlled environment. X-ray photoelectron spectroscopy and Fourier transform infrared (IR) spectroscopy were used to monitor the changes in bulk and surface chemical structure and composition of the deposited films. The equilibrium moisture uptake at relative humidity >90% was lower than 0.13 wt.% for films deposited from PFE or C4F8 monomers. Humidity cycling measurements showed no moisture chemisorption in the deposited films. Attenuated total reflectance infrared spectroscopy (ATR-IR) spectra of the deposited films indicated negligible change in the bulk composition of the deposited films. The estimated diffusivities of water in the deposited fluorocarbon films were of the order of 10-10 cm2/sec, and films deposited from C4F8 monomer showed higher diffusivity as compared to films deposited from PFE monomer. The equilibrium moisture uptake is affected by the presence of polar groups, the F/C ratio, and the O/C ratio. The relatively high diffusivity of water in the fluorocarbon films is attributed to the lack of polar groups in the deposited films. Adsorption onto the surface followed by diffusion into the bulk is proposed as the mechanism for moisture absorption in the fluorocarbon films. Finally, the moisture uptake of the fluorocarbon and hydrofluorocarbon films is compared to that of a conventionally used microelectronic polymer, polyimide (PI 2611), in order to evaluate the effect of polar groups and fluorine content on diffusion and equilibrium moisture uptake.

Hygrothermal Effects on RT-Cured Glass-Epoxy Composites in Immersion Environments. Part A: Moisture Absorption Characteristics

A study on the effect of moisture absorption characteristics of RT-cure glass/epoxy composite and epoxy casting specimens immersed in freshly prepared artificial seawater and distilled water maintained at 333º K are presented in this paper. Results showed that the equilibrium moisture absorption value and the diffusion rate (slope of the moisture absorption curve) are higher in specimens immersed in distilled water than those of artificial seawater. The mixture rule for moisture absorption estimates has been verified for specimens immersed in both environments. These theoretically calculated values compared well with those experimentally obtained. The time of saturation for specimens immersed in seawater was found to be higher than that for those immersed in distilled water.

Hygrothermal Effects on Painted and Unpainted Glass/EpoxyComposites—Part A: Moisture Absorption Characteristics

Hygrothermal Effects on Painted and Unpainted Glass/EpoxyComposites—Part A: Moisture Absorption Characteristics