Dimensional Stability Tests Research Articles

Evaluation of the microstructural and physico-mechanical characteristics of cement-stabilized termite hill soil for construction application

This study investigates the potential of termite hill soil (TS) as an environmentally friendly alternative to cement. By reducing reliance on cement, this approach could decrease the environmental footprint of the construction industry. Portland cement was used to stabilize TS at contents of 5%, 10%, and 15% by weight (wt%). Key engineering properties of the stabilized and un-stabilized specimens were analyzed to assess the suitability of TS for construction applications. Physical properties were evaluated using particle size distribution analysis, dimensional stability testing, and density measurements. Microstructural analysis employed Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray fluorescence (XRF) to investigate the effects of stabilization on the microstructure and its influence on bulk properties. Compressive and flexural strength tests were conducted to assess the mechanical properties of the specimens. Compressive strength results showed that the 10–15 wt% stabilization level achieved the highest values, reaching 3.81 MPa, 4.58 MPa, and 5.91 MPa at 7, 14, and 28 days, respectively. Flexural strength values for the same specimens at these curing times were 0.98 MPa, 1.72 MPa, and 1.94 MPa, respectively. The findings of this investigation can serve as a reference for treating other soils to achieve properties similar to TS, making them suitable for durable construction applications. Additionally, this study demonstrates the feasibility of developing and using TS as construction material for housing solutions in regions with abundant and currently undervalued termite hill resources.

Study of the effect of heat temperature on the chemical changes and hygroscopicity of eucalyptus wood by FT-IR and prediction of mechanical properties by the MLR regression method

This study describes the effect of heat treatment on some physical, chemical, and mechanical properties of Eucalyptus Camaldulensis (EC) wood at different temperatures and treatment times (200 °C–260 °C for 5, 60, and 90 min). The evaluation of hygroscopic properties was determined by relative humidity, mass loss, dimensional stability tests, and density. The results showed that the heat treatment leads to an increase in mass loss of 5.2 %–11.9 % at 200 °C. The density changed significantly for this studied species as well as the dimensional stabilization. Chemical changes in wood structure were assessed by Fourier Transform Infrared Spectroscopy.To verify the validity of the superposition “Mass loss-Density-water absorption” on the mechanical properties (modulus of elasticity (MOE) and modulus of rupture (MOR)) during heat treatment, we have developed a mathematical model based on Multiple Linear Regression (MLR), in order to establish a relationship between the independent parameters and the dependent parameters (MOE and MOR). The evaluation of the quality of the models developed was based on several statistical tools, namely R = 0.99, R2 = 0.99, R2adj = 0.98, and F = 132.33. The results demonstrated that elaborate models of mechanical properties have a high predictive capacity (MOR and MOE). The wood’s carbohydrates (particularly hemicelluloses) are then degraded during the heat treatment. The % of carbon increases from 47.8 to 49.8 %, which is proportional to mass loss, while the % of oxygen decreases by 46.1 %, which is inversely proportional to mass loss. Furthermore, FTIR analysis revealed that the effect of heat-treated wood chemical changes was related to the hydroxyl OH function of cellulose, functional groups, and aromatic system of lignin. In conclusion, the results demonstrated that at 200 °C, heat treatment caused a 5.2–11.9 % increase in mass loss; dimensional stability and density underwent considerable changes. FTIR spectroscopy confirmed the chemical changes in the wood structure during heat treatment. Furthermore, the “MLR” mathematical model showed that density contributed to the increase in MOR and MOE properties, while water absorption and mass loss contributed to the decrease in MOR and MOE properties. Finally, the % of oxygen decreased by 46.1 %, which is inversely proportional to the loss of mass, and the % of carbon increased from 47.8 % to 49.8 %, which is proportional to the loss of mass.

Enhancing the fire resistance of light gauge steel framed floor-ceiling systems through external insulation

Light Gauge Steel Framed (LSF) floor-ceiling systems, composed of thin-walled cold-formed steel (CFS) structural components, offer a high strength-to-weight ratio and cost-effectiveness, leading to their widespread adoption in modern construction. However, research on the fire behaviour of LSF floor-ceiling systems is limited. The industry-standard approach of using two 16 mm gypsum plasterboards for ceilings achieves a maximum Fire Resistance Level (FRL) of 90 min, mainly due to the significant fall-off associated with gypsum plasterboard. Traditional methods for increasing FRL involve adding more layers of gypsum plasterboard; however, the efficacy of achieving a 120-min FRL with three 16 mm gypsum plasterboards remains uncertain. This paper addresses these issues by developing innovative LSF floor-ceiling systems that incorporate external insulation (rigid stone wool) to mitigate the impact of critical ceiling fall-off behaviour and enhance FRL. The research includes dimensional stability tests of rigid stone wool, thermal and structural finite element modelling, and load-bearing small-scale fire tests. The new LSF floor-ceiling system has been shown to achieve an FRL of 130 min, approximately 45 % higher than conventional floor-ceiling systems, offering enhanced fire resistance and increased thermal comfort as a single, integrated solution.

Comparative Effect of Biofillers in pMDI Resin Performance

Abstract This study investigated the feasibility of using wood flour (WF) as a partial substitute in polymeric methylene diphenyl diisocyanate (pMDI) resin and compared its performance with soy flour (SF) substituted in pMDI resin. The physical and mechanical properties of experimental particleboards made with WF and SF substituted in pMDI resin at different substitution percentages were evaluated. The viscosity for the WF at different substitution ratios (5%, 10%, 20%, and 30%) ranged from 314.7 to 6,256.3 cP, whereas SF-substituted resin ranged from 249.7 to 1,291.8 cP. During the production of the boards, it was observed that because of the high viscosity of WF substituted in pMDI resin above 10 percent, it was exceedingly difficult to apply it through spraying and brushing, either to wood particles or veneers. Dimensional stability test results established that the incorporation of SF assisted in mitigating board thickness swelling. The results from the study showed that panels made with SF substituted in pMDI resin at 5 and 10 percent exhibited the overall best performance in all the properties considered compared with panels made with WF substituted in pMDI resin.

Antibacterial activity and physicochemical properties of a sealer containing copaiba oil

This study aimed to evaluate the antimicrobial activity and physicochemical properties of a novel dual-cure endodontic sealer containing copaiba oil. The copaiba oil was obtained and characterized by gas chromatography (GC), and the minimum inhibitory concentration (MIC) was performed. The experimental sealers were formulated with copaiba oil concentrations of 0, 0.5, 1, and 2%, and the RealSeal™ (Sybron endo, Orange, USA) and AH Plus (Dentsply De Trey Gmbh, Konstanz, Germany) were used as the commercial references. The antimicrobial activity of the sealers was evaluated by the direct contact test for 1h and 24h. To evaluate the physicochemical properties of the sealers, the degree of conversion, setting time, film thickness, dimensional stability, and radiopacity tests were performed. The data were statistically analyzed by one-way ANOVA and Tukey’s test (α = 0.05). Concerning the results, the sealers containing copaiba oil showed antimicrobial activity without harming the physicochemical properties.

Properties of cross-laminated oriented bamboo scrimber board (CL-OBSB)

Physical and mechanical properties were evaluated for cross-laminated oriented bamboo scrimber board (CL-OBSB). Results of non-destructive testing revealed a linear relationship of parallel grain content with ultrasonic-wave velocity, dynamic modulus of elasticity (DMOEu), tap-tone velocity, and DMOEt values. In terms of the ratio of parallel grain, CL-OBSB 80%(//) possessed the highest modulus of elasticity and modulus of rupture values along with the greatest strength. The high grain content compressed in a parallel direction contributed to superior strength performance. Regarding the perpendicular compressive (C┴) strength, because both the CL-OBSB 40%(//) configuration and CL-OBSB have a mid-layer consisting of 60% parallel grain, CL-OBSB 40%(//) holds the largest C┴ value. Furthermore, the shear bond strength (S) showed that the S// value was 1.03 times that of the S┴ value with a wood failure frequency of 97%. After the dimensional stability test, the water absorption and volumetric swelling of the four CL-OBSB types ranged between 15.3% and 17.7% and 9.5% to 10.6%, respectively. In conclusion, the orthogonal configuration of CL-OBSBs can improve balance expansion and contraction in different directions, thus increasing its dimensional stability.

Effect of Extrinsic Pigmentation on Dimensional Stability, Hardness, Detail Reproduction, and Color of a Silicone.

The aim of the study is to evaluate the effect of extrinsic pigmentation on the dimensional stability, hardness, detail reproduction, and color of a silicone after thermocycling. Sixty samples of MDX4-4210 silicone (Dow Corning Corporation Medical Products) with intrinsic pink pigment (H-109-P, Factor II) and intrinsic opacifier (TiO) were fabricated. Two groups were created: Group 1-only intrinsic pigmentation (H-109P, Factor II + TiO) (Control); and Group 2-intrinsic (H-109P, Factor II + TiO) and extrinsic (Tan FE - 215, Factor II) pigmentation. The following tests were performed for each group: dimensional stability, Shore A hardness, detail reproduction, and color. Readings for the tests were taken before and after thermocycling (2,000 cycles). For dimensional stability and hardness, two-way analysis of variance (ANOVA) was used. One-way ANOVA was used for the color test. In case of significant statistical difference, the Tukey test was applied (p <0.05). All samples achieved the same detail reproduction score, therefore, no statistical evaluation was performed. For the dimensional stability test, comparing the initial time with the final time, there was a significant contraction in both groups after thermocycling. For the hardness test, comparing the time points, only group 1 showed a significant reduction in hardness after thermocycling. Groups 1 and 2 scored 2 for the detail reproduction test, before and after thermocycling. Comparing group 1 with group 2, there was no significant difference for color change. Based on the tests performed, extrinsic pigmentation did not show a negative effect on silicone, and therefore it can be indicated. The results of the dimensional, hardness, detail reproduction and color evaluations of the MDX4-4210 silicone were clinically acceptable in all cases in the groups with and without extrinsic pigmentation.

Alkil keten dimer / borik asit kombinasyonları ile emprenye edilen sarıçam (Pinus sylvestris L.) örneklerinin boyutsal kararlılığı ve mekanik özellikleri

Alkil Keten Dimer (AKD); ıslak mukavemet ve kâğıdın basılabilirlik özelliklerini değiştirdiği için çoğunlukla kağıt endüstrisinde kullanılır. AKD, odunun hidroksil gruplarıyla reaksiyona girer ve hidrokarbon zincirlerinin etkili bir şekilde esterleşmesine katkıda bulunur. Oduna AKD ilavesi ile boyutsal kararlılığın arttırılması hedeflenmiştir. Ayrıca çevre dostu olan bor bileşikleri ahşabın biyolojik zararlılara karşı korunmasında oldukça etkilidir. Ancak bor bileşikleri odundan kolayca yıkanabilmektedir. AKD/BA sinerjik etkisi ile birlikte bu olumsuz özelik giderilmeye çalışılıp odunun boyutsal kararlılığı arttırılmaya çalışılmıştır. &#x0D; Bu çalışmada AKD (%5, %10, %18) ve borik asit (%3 BA) kombinasyonları ile emprenye edilmiş sarıçam (Pinus sylvestris L.) odun örnekleri kullanılmıştır. Örneklerin su alma ve boyutsal kararlılıkları ile mekanik özellikleri belirlenmiştir. Su alma ve boyutsal kararlılık testi için AWPA E4, liflere paralel basınç direnci için TS 2471 standartları kullanılmıştır. Elde edilen sonuçlara göre AKD/BA kombinasyonunun daha düşük su alma oranına sahip olduğu görülmüştür. Mekanik testte AKD ve BA sinerjik etkisi ile birlikte örneklerin mekanik özellikleri bir miktar iyileşmiştir.

Dimensional stability and mechanical properties of extruded-compression biopolymer composites made from selected Nigerian grown wood species at varying proportions

250 µm particle size of wood and polyethylene (PE) materials were compounded at mixing proportions of 60/40, 70/30, and 80/20 (with an increase in polymer to decrease in wood content) and extruded using a single screw extruder at a temperature range of 110–135 °C. The particles of Gmelina Arborea, Tectona grandis, Cordiamilleni, and Nauclea diderichii with recycled Polyethylene were compounded and compressed at 175 N/mm to produce biopolymer composites. The biopolymer composites were subjected to dimensional stability test at 24 h of the water soak method and the ability to withstand load-bearing capacity was investigated. The outcome of the results shows that extruded-compressive biopolymer composites had values ranging from 0.06–1.43 g/cm3, 0.38–3.41%, and 0.82–6.85% for observed density, water absorption, and thickness swelling at 24 h of a water soak test. The mechanical properties values ranged from 0.28 Nmm−2–21.35 Nmm−2 and 0.44–550.06 Nmm−2 for flexural modulus and strength; and 191.43 Nmm−2–1857.24 Nmm−2 and 0.35 Nmm−2–243.75 Nmm−2 for tensile modulus and strength respectively. It was observed that moisture uptake and strength displayed by the composites vary accordingly in values obtained for wood species at different mixing proportions. As observed that the more polyethylene content is compounded to wood, the better its dimensional stability, and flexural and tensile properties. The wood particles of Cordiamilleni compounded at a proportion of 60 to 40 (polyethylene/wood) performed best in dimensional stability and load-bearing capacity. This study confirmed the effect of methods on wood species and recycled PE for manufacturing wood polymer-based composite for both indoor and outdoor applications.

Effect of alginate impression disinfection with sodium hypochlorite and castrol oil on Candida albicans counts and dimensional stability of the study model

Alginate is the most common used material because it is easy to use, affordable, and well accepted by patients. When impressing, alginate would be in contact with the surface of the oral cavity and saliva. It caused the microflora, like Candida albicanswould adhere to the surface so that it can cause cross-infection. Cross-infection prevention could be done by disinfecting the impression material before filling with gypsum. The main things of choosing a disinfectant is that the disinfectant material could eliminate microorganisms and affect the dimensional stability of impression material. This study aimed to determine the effect of alginate impression disinfection with sodium hypochlorite and castor oil (Ricinus communis oil) on the Candida albicanscounts and the dimensional stability of the study model. The samples of Candida albicanswas counted by colony counter andthe dimensional stability test by digital caliper. This study showed that alginate impression desinfection with castor oil had almost the same effectiveness as sodium hypochlorite in reducing the Candida albicanscounts, but dimension was changed even though the value of the dimensional changes is still within the tolerance limit.

EFFECT OF ADDITIONAL TRISODIUM PHOSPHATE 2% AS A RETARDER TO DIMENSIONAL STABILITY TESTS DENTAL MATERIAL ALGINATE AFTER HARDENING

The alginate moulding material is a negative mold of the teeth and oral cavity tissue. The alginate molding material is hydrophilic and is used as a pre-elimination mold to a custom tray for a more accurate second mold. The dimensional stability of the alginate mold is essential for the success of making a precise mold model. Changes in alginate dimensions are related to the contraction during the hardening process of the alginate molding material or the setting time. The addition of Trisodium Phosphate (TSP) is known to prolong the hardening time of alginates by slowing down the reaction of alginate salts and calcium sulfate. The purpose of this study was to compare the dimensional stability test of the alginate molding material with the addition of 2% trisodium phosphate and those without 2% trisodium phosphate after hardening. This research is pure laboratory experimental research. Alginate was divided into two groups: the group according to the manufacturer's provisions and the group added with 2% trisodium phosphate. The results of this study were analyzed using the unpaired T-test, and the results showed a p-value &lt;0.05, namely (0.00 &lt;0.05), so there was a significant difference in the dimensional stability of alginate without TSP 2% with the addition of TSP 2%. This study showed that the addition of 2% TSP improved dimensional stability in the group with the addition of 2% TSP.

Chemical, hygroscopic, and mechanical properties of various wood species heat treated via the ThermoWood® method

Fourier-transform infrared spectroscopy (FTIR), energy dissipation spectrometry, dimensional stability, and compressive strength tests were conducted parallel to the fibers on various heat-treated trees, i.e., narrow-leaved ash (Fraxinus angustifolia Vahl), aspen (Populus tremula L.), Oriental spruce (Picea orientalis (L.) Link.), and Uludağ fir (Abies bornmüelleriana Mattf.), which grow naturally in forests in Turkey. Panels made from these trees were first heat treated via the ThermoWood® method, producing ThermoWood® panels. Then, FTIR, as well as energy dissipation spectrometry analysis, dimensional stability, and compressive strength tests were performed on test samples prepared from the panels. The FTIR data showed that the hemicelluloses were degraded in the ThermoWood® test samples and the proportion of cellulose increased. The energy dissipation spectrometry results showed that the amount of carbon increased, the amount of oxygen decreased, while the amount of hydrogen remained approximately the same in the ThermoWood® panels compared to the control samples. It was determined that the proportion of silicon increased in the narrow-leaved ash panels. In addition, among the physical properties, the amount of shrinkage and swelling decreased in all the tested ThermoWood® panels compared to the control samples, whereas the compressive strength values, which are considered a mechanical property, increased.

The effects of mixing slurry water with type III gypsum on setting time, compressive strength and dimensional stability

Background: Type III gypsum is a material used to make dental master casts. It may be added to an accelerator, such as slurry water, to shorten setting time. Calcium sulphate in slurry water may affect setting time, compressive strength and dimensional stability. Purpose: The study evaluated the effect of slurry water on the setting time, compressive strength and dimensional stability of type III gypsum. Methods: Eighty-one samples were made of type III gypsum, divided into three groups: group A was gypsum mixed with 1% slurry water, group B, gypsum mixed with 2% slurry water and group C, gypsum mixed with distilled water. Each sample was formed using a standardised master mould. For testing setting time, a cylindrical mould 25 mm in diameter and height was used; for compressive strength testing, the cylindrical mould was 20 mm in diameter and 40 mm in height; and for dimensional stability testing, a pair of cylindrical, ruled block and mould were used. Setting time was tested using Vicat’s apparatus; compressive strength was tested using a universal testing machine; and dimensional stability was tested using digital callipers. The data were analysed by one-way analysis of variance (ANOVA) and least significant difference (LSD) tests. Results: One-way ANOVA and LSD tests showed significant differences in the effect of slurry water on the setting time, compressive strength and dimensional stability of type III gypsum (p&lt;0.05). Conclusion: The use of slurry water can shorten setting time, decrease compressive strength and increase dimensional change of type III gypsum.

Characterization of Thermal Bio-Insulation Materials Based on Oil Palm Wood: The Effect of Hybridization and Particle Size.

Oil palm wood is the primary biomass waste produced from plantations, comprising up to 70% of the volume of trunks. It has been used in non-structural materials, such as plywood, lumber, and particleboard. However, one aspect has not been disclosed, namely, its use in thermal insulation materials. In this study, we investigated the thermal conductivity and the mechanical and physical properties of bio-insulation materials based on oil palm wood. The effects of hybridization and particle size on the properties of the panels were also evaluated. Oil palm wood and ramie were applied as reinforcements, and tapioca starch was applied as a bio-binder. Panels were prepared using a hot press at a temperature of 150 °C and constant pressure of 9.8 MPa. Thermal conductivity, bending strength, water absorption, dimensional stability, and thermogravimetric tests were performed to evaluate the properties of the panels. The results show that hybridization and particle size significantly affected the properties of the panels. The density and thermal conductivity of the panels were in the ranges of 0.66–0.79 g/cm3 and 0.067–0.154 W/mK, respectively. The least thermal conductivity, i.e., 0.067 W/mK, was obtained for the hybrid panels with coarse particles at density 0.66 g/cm3. The lowest water absorption (54.75%) and thickness swelling (18.18%) were found in the hybrid panels with fine particles. The observed mechanical properties were a bending strength of 11.49–18.15 MPa and a modulus of elasticity of 1864–3093 MPa. Thermogravimetric analysis showed that hybrid panels had better thermal stability than pure panels. Overall, the hybrid panels manufactured with a coarse particle size exhibited better thermal resistance and mechanical properties than did other panels. Our results show that oil palm wood wastes are a promising candidate for thermal insulation materials.

Investigation of the Effect of Weft Yarn Parameters on the Elasticity and Recovery Properties of Stretch Denim Fabrics

ABSTRACT The aim of this study was to examine the effect of weft yarn parameters on the elasticity and recovery properties of stretch denim fabrics. For this purpose, frequently used denim fabric was taken as a reference point, and to study the elasticity, and dimensional change properties of the reference fabric, the production of new denim fabrics was designed with the use of different core yarns in the weft direction with different ratios. As a result, five different denim fabrics containing three different weft yarns with different sequences in Twill 3/1 Z weave type were produced. All fabric samples were prepared as half legs form and rinse washing, stone washing and stone+bleaching washing processes were applied. Elasticity, residual extension, and dimensional stability tests of the samples were performed, and the results were analyzed regarding the weft yarn properties and finishing processes. In addition to these tests, mass per unit area was examined to observe the weight changes of the fabrics due to shrinkage after washing. All tests were evaluated statistically. According to the analysis, it was found that the fabric performance was affected by the weft yarn type, and the different washing processes.

COMPARISON OF THE ADDITION OF Manihot utilisima (PATI UBI WOOD) TO DIMENSIONAL STABILITY OF IRREVERSIBLE HYDROCOLLOID MOLD

Alginate impression material is used to print the teeth and the oral tissues; alginate molding material is from abroad and expensive. Modification to the impression material alginate with cassava starch with 1: 1 obtained detailed reproduction of the same printed material alginate without added with cassava starch. The study's objective was to get an alternative form of printed material alginate plus Manihot utilisima (cassava starch) with the nature of the physical properties following the standard. The study methods used laboratory experiments. The materials used in this study were printed material alginate (Hydrogum fast setting), starch cassava starch cap dua kelinci, water, and tools calliper inside digital. There were four groups of a control group, a group cassava starch ratio of 50: 50, groups of cassava starch ratio of 60: 40, and a comparison group of cassava starch 70: 30. The results were dimensional stability of printed materials Alginate without additions were (73.72, 48.77, 30.51), the dimensional stability of the printed material alginate with a ratio of 50: 50 were (74.24, 40.82, 30.76), the dimensional stability of the printed material alginate with a ratio of 60: 30 were ( 75.39, 49.67, 31.57), and the results of dimensional stability alginate ((irrevesible hydrocolloid ) molding material with a ratio of 70: 30 were (76.36, 50.94, 32.86). The conclusion is the addition of Manihot utilisima on standard printed material alginate (irrevesible hydrocolloid) obtained dimensional stability test results that met the standards at a ratio of 50: 50 of ANSI/ADA no.18/1992. Manihot utilisima was one of the appropriate alternatives as a mixture in impression material alginate (irrevesible hydrocolloid).

Extended-pour and conventional alginates: effect of storage time on dimensional accuracy and maintenance of details.

ABSTRACTObjective: This study aimed to evaluate the dimensional stability and maintenance of details of conventional and high stability alginates up to 5-day storage. Methods: Two types of alginates were selected (n=10) for this study, conventional (Hydrogum) and high stability alginates (Hydrogum 5), which were produced with the aid of a cylindrical metal block and a ring-shaped metal mold (Specifications 18, 19, and 25, ANSI/ADA). Ten images were obtained from the molds for the dimensional stability test, which were taken immediately after their production and at each different storage periods (15 min, 24 h, 48 h, 72 h, 96 h, and 120 h) by a digital camera. The specimens were kept hermetically sealed in plastic bags (23°C) and then used to obtain 140 (n=70) dental stone models, used in the detail reproduction test, in which the angular accuracy of three grooves (20 µm, 50 µm, and 75 µm) was observed at each period. The details reproduction accuracy was classified using a predetermined score classification. Measurements of dimensional changes were made in the Corel DRAW X6 program. The data were submitted to the Student’s t-test (α?#8197;= 0.05). Results: A statistically significant difference concerning the size of the matrix was observed after 24h for both alginates, and a statistically significant negative linear dimensional change (contraction) was verified after 24 h of storage (1.52% for the high stability alginate, and 1.32% for the conventional alginate). The high stability alginate kept the full details for 72 hours, while the conventional alginate, for 24 h. Both alginates reproduced the 75 µm groove at all storage periods. Conclusion: Impressions made with both alginates presented satisfactory clinical results when the alginates were immediately poured.

Influence of the Order of Incorporation of Sulfur in the Mechanical Properties of Vulcanized Nr Compounds

The objective of this work was to evaluate the influence of the order of sulfur addition on the mechanical properties of vulcanized natural rubber compounds. The addition of sulfur was carried out by two methodologies: (I) sulfur was added at the beginning of the mastication process, and (II) sulfur was added at the end of the mixing process. The compounds were obtained in open cylinder, and vulcanized in a press at 150°C. The vulcanization parameters were determined by rheometry, where as the mechanical properties were evaluated by testing samples for their tensile strength, tear strength, resilience, and Shore-A hardness. The dimensional stability of the vulcanized samples was also evaluated experimentally, by comparing specimens not heat-treated to those submitted to 100°C for 4 hours. Comparing the results of method (I) to method (II), the results, indicate that the addition of sulfur at the beginning of the mastication process (method I) yielded increases of 20 and 11% in tensile strength and tear strength, respectively, followed by a 9% increase in hardness, and 6% in resilience, without significant losses in maximum elongation. The dimensional stability test showed a reduction of 75% in the contraction for the vulcanized samples which had sulfur addition at the beginning of the mastication process of the unvulcanized NR rubber.

Economic polymer-based waterproofing membranes by incorporation of wastes to form eco-friendly material

Waste recycling is a way to produce innovative low cost eco-friendly materials to solve environmental problems caused by different types of industrial by-product and polymeric wastes. Natural rubber loaded with different types of waste materials Calcium Hydroxide Ca(OH)2, Calcium Carbonate (CaCO3), Fly Ash (class F) and Waste rubber (WR) by mixing through open mill and then pressed in hot press to obtain low cost eco-friendly waterproofing membranes with desired properties. All samples pass the water penetration test up to 6 bars. The samples water absorption coefficients ranged from (0.1 to 0.3%) for all investigated samples. UV weathering and thermal aging tests were done to the samples while no changes on mechanical properties appeared before and after the tests. Dimensional stability test was done for all samples; a slight dimension change occurs. The mechanical and hardness measurements for all samples were done while good mechanical properties obtained. The price of square meter of 2 mm thickness for all samples was calculated in order to estimate its feasibility. A comparison of our samples with other waterproofing membranes from two famous Egyptian companies was done. Low cost and qualified waterproofing material can be obtained from recycling of some wastes.

The effect of three different pulp capping cements on mineralization of dental pulp stem cells.

This study evaluated the osteogenic differentiation of human dental pulp stem cells in response to substances released by the pulp capping agents, Biodentine (BD), mineral trioxide aggregate (MTA) and two-paste calcium hydroxide cement (CHC), along with their physicochemical characteristics. The dimensional stability test showed that of the materials studied, only BD met the standards recommended by the International Organization for Standardization (ISO) for pulp capping materials and thus can be used safely. In the chemical tests, BD was the most stable material. In the Alizarin red S test, BD formed the higher amount of mineralized nodules in the mineralizing medium and also formed mineralized nodules in a non-mineralizing medium. BD releases substances that can significantly induce formation of the human dental pulp stem cell-mineralized extracellular matrix, with physicochemical characteristics that are more conducive to pulp repair than those of MTA and CHC.