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Classification, processing and application of hydrogels: A review

Ullah F, Othman MB, Javed F, Ahmad Z, Md Akil H

Mater Sci Eng C Mater Biol Appl, 2015 Dec 1;57:414-33.
PMID: 26354282 DOI: 10.1016/j.msec.2015.07.053

This article aims to review the literature concerning the choice of selectivity for hydrogels based on classification, application and processing. Super porous hydrogels (SPHs) and superabsorbent polymers (SAPs) represent an innovative category of recent generation highlighted as an ideal mould system for the study of solution-dependent phenomena. Hydrogels, also termed as smart and/or hungry networks, are currently subject of considerable scientific research due to their potential in hi-tech applications in the biomedical, pharmaceutical, biotechnology, bioseparation, biosensor, agriculture, oil recovery and cosmetics fields. Smart hydrogels display a significant physiochemical change in response to small changes in the surroundings. However, such changes are reversible; therefore, the hydrogels are capable of returning to its initial state after a reaction as soon as the trigger is removed.

Matched MeSH terms: Compressive Strength
Structure-property relationships of iron-hydroxyapatite ceramic matrix nanocomposite fabricated using mechanosynthesis method

Nordin JA, Prajitno DH, Saidin S, Nur H, Hermawan H

Mater Sci Eng C Mater Biol Appl, 2015 Jun;51:294-9.
PMID: 25842138 DOI: 10.1016/j.msec.2015.03.019

Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone-implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12h milling in the presence of HPO4(2-) ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis.

Matched MeSH terms: Compressive Strength
Surface morphological and mechanical properties of zinc oxide eugenol using different types of ZnO nanopowder

Bakhori SKM, Mahmud S, Mohamad D, Masudi SM, Seeni A

Mater Sci Eng C Mater Biol Appl, 2019 Jul;100:645-654.
PMID: 30948101 DOI: 10.1016/j.msec.2019.03.034

Zinc oxide eugenol (ZOE) cements are generally made up of 80%-90% ZnO powder while the remaining content consists of eugenol bonding resin. ZnO structure plays a major role in the morphology and mechanical properties of ZOE. In this study, we investigated the effects of different particle sizes/shapes of ZnO particles on the surface and mechanical properties of ZOE. Three samples were prepared namely ZnO-Ax, ZnO-B and ZnO-K. The crystallite sizes calculated from XRD were 37.76 nm (ZnO-Ax), 39.46 nm (ZnO-B) and 42.20 nm (ZnO-K) while the average particle sizes obtained by DLS were 21.11nm (ZnO-Ax), 56.73 nm (ZnO-B) and 2012 nm (ZnO-K). Results revealed that the compressive strengths of ZOE-Ax and ZOE-B were improved by 87.92% and 57.16%, respectively, relative to that of commercial ZOE-K. Vickers hardness test demonstrated that the hardness of ZOE-Ax and ZOE-B also increased by 74.9% and 31.1%, respectively. The ZnO-Ax nanostructure possessed a small average particle size (21.11 nm), a homogeneous size distribution (DLS) and an oxygen-rich surface (from EDS and elemental mapping). Meanwhile, ZnO-B exhibited a slightly larger average particle size of 56.73 nm compared with that of other samples. Sample ZnO-Ax demonstrated the highest compressive strength which was attributed to its large particle surface area (21.11 nm particle size) that provided a large contact area and greater interfacial (or interlock) bonding capability if compared to that of ZnO-K sample (2012 nm particle size).

Matched MeSH terms: Compressive Strength
An injectable poly(caprolactone trifumarate-gelatin microparticles) (PCLTF-GMPs) scaffold for irregular bone defects: Physical and mechanical characteristics

Al-Namnam NM, Kutty MG, Chai WL, Ha KO, Kim KH, Siar CH, et al.

Mater Sci Eng C Mater Biol Appl, 2017 Mar 01;72:332-340.
PMID: 28024594 DOI: 10.1016/j.msec.2016.11.086

Recently, a modified form of a three-dimension (3D) porous poly(caprolactone-trifumarate) (PCLTF) scaffold has been produced using a fabrication technique that involves gelatin microparticles porogen leaching. This poly(caprolactone trifumarate-gelatin microparticles) (PCLTF-GMPs) scaffold has been shown to be biocompatible, more flowable clinically, and has a shorter degradation time as compared to its existing predecessors. In this report, a detailed characterization of this new scaffold was performed by testing its cytocompatibility, analyzing the surface topography, and understanding its thermal, physical and mechanical properties. The result showed that the PCLTF-GMPs has no critical cytotoxic effect. To confirm improvement, the surface properties were compared against the older version of PCLTF fabricated using salt porogen leaching. This PCLTF-GMPs scaffold showed no significant difference (unpaired t-test; p>0.05) in mechanical properties before and after gelatin leaching. However, it is mechanically weaker when compared to its predecessors. It has a high biodegradability rate of 16weeks. The pore size produced ranges from 40 to 300μm, and the RMS roughness is 613.7±236.9nm. These characteristics are condusive for osteoblast in-growth, as observed by the extension of filopodia across the macropores. Overall, this newly produced material has good thermal, physical and mechanical properties that complements its biocompatibility and ease of use.

Matched MeSH terms: Compressive Strength
Mechanical, thermal and morphological characterisation of 3D porous Pennisetum purpureum/PLA biocomposites scaffold

Revati R, Abdul Majid MS, Ridzuan MJM, Normahira M, Mohd Nasir NF, Rahman Y MN, et al.

Mater Sci Eng C Mater Biol Appl, 2017 Jun 01;75:752-759.
PMID: 28415525 DOI: 10.1016/j.msec.2017.02.127

The mechanical, thermal, and morphological properties of a 3D porous Pennisetum purpureum (PP)/polylactic acid (PLA) based scaffold were investigated. In this study, a scaffold containing P. purpureum and PLA was produced using the solvent casting and particulate leaching method. P. purpureum fibre, also locally known as Napier grass, is composed of 46% cellulose, 34% hemicellulose, and 20% lignin. PLA composites with various P. purpureum contents (10%, 20%, and 30%) were prepared and subsequently characterised. The morphologies, structures and thermal behaviours of the prepared composite scaffolds were characterised using field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The morphology was studied using FESEM; the scaffold possessed 70-200μm-sized pores with a high level of interconnectivity. The moisture content and mechanical properties of the developed porous scaffolds were further characterised. The P. purpureum/PLA scaffold had a greater porosity factor (99%) and compression modulus (5.25MPa) than those of the pure PLA scaffold (1.73MPa). From the results, it can be concluded that the properties of the highly porous P. purpureum/PLA scaffold developed in this study can be controlled and optimised. This can be used to facilitate the construction of implantable tissue-engineered cartilage.

Matched MeSH terms: Compressive Strength
Co-incorporation of graphene oxide/silver nanoparticle into poly-L-lactic acid fibrous: A route toward the development of cytocompatible and antibacterial coating layer on magnesium implants

Bakhsheshi-Rad HR, Ismail AF, Aziz M, Akbari M, Hadisi Z, Khoshnava SM, et al.

Mater Sci Eng C Mater Biol Appl, 2020 Jun;111:110812.
PMID: 32279830 DOI: 10.1016/j.msec.2020.110812

Magnesium (Mg) alloys present great potential for the development of orthopedic implants, whereas, their high degradation rate and poor antibacterial performance have restricted orthopedic applications. In this work, PLLA/GO-AgNP (poly-L-lactic acid/graphene oxide- silver nanoparticle) with different concentration of GO-AgNPs were deposited on Mg alloy via electrospinning method for enhancement of corrosion resistance and antibacterial performance. The result revealed that incorporation of GO into PLLA fibrous considerably slowed down the degradation rate of Mg alloy substrate and reduced the H2 release rate from the substrate. Also, co-incorporation of GO and AgNPs into PLLA fibrous resulted in substantial escalate in compressive strength after immersion in simulated body fluid (SBF). Antibacterial activity test exhibited that Mg alloy and neat PLLA fibrous presented minimal inhibition area toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In contrast, using PLLA/GO-AgNPs fibrous improved antibacterial performance against both bacteria. Cytocompatibility results indicated that PLLA/GO-AgNPs fibrous with a low amount of GO-AgNPs enhanced cell proliferation and growth while high co-incorporation of GO-AgNPs showed a negative effect on cell proliferation. Taken together, PLLA/1GO-AgNPs fibrous coating shows suitable corrosion resistance, cytocompatibility, and antibacterial function for use in orthopedic applications.

Matched MeSH terms: Compressive Strength
Mechanical and microarchitectural analyses of cancellous bone through experiment and computer simulation

Syahrom A, Abdul Kadir MR, Abdullah J, Öchsner A

Med Biol Eng Comput, 2011 Dec;49(12):1393-403.
PMID: 21947767 DOI: 10.1007/s11517-011-0833-0

The relationship between microarchitecture to the failure mechanism and mechanical properties can be assessed through experimental and computational methods. In this study, both methods were utilised using bovine cadavers. Twenty four samples of cancellous bone were extracted from fresh bovine and the samples were cleaned from excessive marrow. Uniaxial compression testing was performed with displacement control. After mechanical testing, each specimen was ashed in a furnace. Four of the samples were exemplarily scanned using micro-computed tomography (μCT) and three dimensional models of the cancellous bones were reconstructed for finite element simulation. The mechanical properties and the failure modes obtained from numerical simulations were then compared to the experiments. Correlations between microarchitectural parameters to the mechanical properties and failure modes were then made. The Young's modulus correlates well with the bone volume fraction with R² = 0.615 and P value 0.013. Three different types of failure modes of cancellous bone were observed: oblique fracture (21.7%), perpendicular global fracture (47.8%), and scattered localised fracture (30.4%). However, no correlations were found between the failure modes to the morphological parameters. The percentage of error between computer predictions and the actual experimental test was from 6 to 12%. These mechanical properties and information on failure modes can be used for the development of synthetic cancellous bone.

Matched MeSH terms: Compressive Strength/physiology
Design and validation of a bi-axial loading bioreactor for mechanical stimulation of engineered cartilage

Yusoff N, Abu Osman NA, Pingguan-Murphy B

Med Eng Phys, 2011 Jul;33(6):782-8.
PMID: 21356602 DOI: 10.1016/j.medengphy.2011.01.013

A mechanical-conditioning bioreactor has been developed to provide bi-axial loading to three-dimensional (3D) tissue constructs within a highly controlled environment. The computer-controlled bioreactor is capable of applying axial compressive and shear deformations, individually or simultaneously at various regimes of strain and frequency. The reliability and reproducibility of the system were verified through validation of the spatial and temporal accuracy of platen movement, which was maintained over the operating length of the system. In the presence of actual specimens, the system was verified to be able to deliver precise bi-axial load to the specimens, in which the deformation of every specimen was observed to be relatively homogeneous. The primary use of the bioreactor is in the culture of chondrocytes seeded within an agarose hydrogel while subjected to physiological compressive and shear deformation. The system has been designed specifically to permit the repeatable quantification and characterisation of the biosynthetic activity of cells in response to a wide range of short and long term multi-dimensional loading regimes.

Matched MeSH terms: Compressive Strength
Fulltext Influence of Glass Silica Waste Nano Powder on the Mechanical and Microstructure Properties of Alkali-Activated Mortars

Samadi M, Shah KW, Huseien GF, Lim NHAS

Nanomaterials (Basel), 2020 Feb 14;10(2).
PMID: 32075038 DOI: 10.3390/nano10020324

The recycling of millions of tons of glass bottle waste produced each year is far from optimal. In the present work, ground blast furnace slag (GBFS) was substituted in fly ash-based alkali-activated mortars (AAMs) for the purpose of preparing glass bottle waste nano-powder (BGWNP). The AAMs mixed with BGWNP were subsequently subjected to assessment in terms of their energy consumption, economic viability, and mechanical and chemical qualities. Besides affording AAMs better mechanical qualities and making them more durable, waste recycling was also observed to diminish the emissions of carbon dioxide. A more than 6% decrease in carbon dioxide emissions, an over 16% increase in compressive strength, better durability and lower water absorption were demonstrated by AAM consisting of 5% BGWNP as a GBFS substitute. By contrast, lower strength was exhibited by AAM comprising 10% BGWNP. The conclusion reached was that the AAMs produced with BGWNP attenuated the effects of global warming and thus were environmentally advantageous. This could mean that glass waste, inadequate for reuse in glass manufacturing, could be given a second life rather than being disposed of in landfills, which is significant as concrete remains the most commonplace synthetic material throughout the world.

Matched MeSH terms: Compressive Strength
Minimum level of jumping exercise required to maintain exercise-induced bone gains in female rats

Ooi FK, Singh R, Singh HJ, Umemura Y

Osteoporos Int, 2009 Jun;20(6):963-72.
PMID: 18839049 DOI: 10.1007/s00198-008-0760-6

SUMMARY: This study determines the minimum level of exercise required to maintain 8 weeks of jumping exercise-induced bone gains in rats. It was found that the minimum level of exercise required for maintaining the different exercise-induced bone gains varied between 11% and 18% of the initial exercise intensity.
INTRODUCTION: This study ascertains the minimum level of follow-up exercise required to maintain bone gains induced by an 8-week jumping exercise in rats.
METHODS: Twelve groups of 12-week old rats (n = 10 rats per group) were given either no exercise for 8 (8S) or 32 weeks (32S), or received 8 weeks of standard training program (8STP) that consisted of 200 jumps per week, given at 40 jumps per day for 5 days per week, followed by 24 weeks of exercise at loads of either 40 or 20 or 10 jumps per day, for either 5, or 3, or 1 day/week. Bone mass, strength, and morphometric properties were measured in the right tibia. Data were analyzed using one-way analyses of variance.
RESULTS: Bone mass, strength, mid-shaft periosteal perimeter and cortical area were significantly (p < 0.05) higher in the rats given 8STP than that in the 8S group. The minimal level of exercise required to maintain the bone gains was 31, 36, 25, and 21 jumps per week for mass, strength, periosteal perimeter and cortical area, respectively.
CONCLUSIONS: Eight weeks of jumping exercise-induced bone gains could be maintained for a period of 24 weeks with follow-up exercise consisting of 11% to 18% of the initial exercise load.

Matched MeSH terms: Compressive Strength/physiology
Fulltext Experimental study on shear behaviour of high strength reinforced recycled concrete beam

Lian, Oh Chai, Wee, Lee Siong, Mohd Asha’ari Masrom, Hua, Goh Ching

Pertanika Journal of Science & Technology, 2013;21(2):601-610.
MyJurnal

Recently, there has been great interest on the applicability of Recycled Concrete Aggregate (RCA) as a new ecological construction material that can be sustainable in a gradually expanding construction industry. This paper reports the structural performance particularly on shear behaviour of high strength reinforced recycled concrete beams. Compressive cube strength of the tested beams ranged from 65-74 MPa at the age of 28-days. The experimental program compared conventional concrete mix with concrete mix having substitution of 25% recycled concrete aggregates of grade 25-30 MPa. In this study, three 150 mm x 200 mm x 1200 mm simply supported rectangular concrete beams in each mix were tested under a four-point bending static load with various shear span to effective depth ratios (a/d = 1.0, 1.5, 2.0). Subsequently, the shear behavior of the beams was investigated through studies of load-deflection responses, effect of a/d ratios and crack patterns. The test results reported that the substitution of 25% recycled concrete coarse aggregates barely affects the shear capacity of the high strength reinforced concrete beams with a/d of 1.5 onwards. Finally, experimental results were compared using existing design codes by ACI 318, Eurocode-2 and AS3600 which lie on the safe side.

Matched MeSH terms: Compressive Strength
Fulltext Incinerated domestic waste sludge powder as sustainable replacement material for concrete

Dahlia Lema, A.M., Kartini, K., Dyg. Siti Quraisyah, A.A., Anthony, A.D., Nuraini, T., Siti Rahimah, R.

Pertanika Journal of Science & Technology, 2015;23(2):193-205.
MyJurnal

Sludge is an unavoidable product of wastewater treatment that creates problems of disposal. Increasingly, strict environmental control regulations have resulted in limitations on sludge disposal options.Disposal by incineration has been found to be a good option. In this research, application of domestic waste sludge powder (DWSP) was used as cement replacement in concrete mix. This study utilised replacement of 3 %, 5 %, 7 %, 10 % and 15 % by weight of OPC with water binder (w/b) ratio of 0.60, 0.55 and 0.40 for Grade 30, Grade 40 and Grade 50 respectively. The performance of DWSP concrete in terms of its compressive strength, water absorption, water permeability and Rapid Chloride Ion penetration were investigated. All values of compressive strength for DWSP concrete were lower compared to the OPC control, and the strength decreased as the percentage of replacement with DWSP increased for Grade 30 and Grade 50, except for Grade 40 at replacement of 7 %. Meanwhile, water absorption and water permeability for the DWSP concrete increased as the replacement increased. Overall, with further research in producing quality DWSP, the potential of using this waste as a cement replacement material is very promising.

Matched MeSH terms: Compressive Strength
Fulltext Improvement of engineering properties of peat with Palm Oil Clinker

Rahman, M. E., Leblouba, M., Pakrashi, V.

Pertanika Journal of Science & Technology, 2014;22(2):627-636.
MyJurnal

The aim of this study is to investigate the effects of Palm Oil Clinker (POC) added as a stabilizer for improving the strength of peat. Cement and POC are added into peat up to 50% of the maximum dry unit weight. Treated peat achieved higher dry unit weight, almost 2.5 times as compared to untreated peat. Unconfined compressive strength (UCS) of treated peat is also investigated for soaked and unsoaked conditions. The results show that curing time improved the unconfined compressive strength of treated sample and increased by a factor of 20 and 11 for unsoaked and soaked conditions after 28 days of curing, respectively. The treated samples added with POC can be related to an increase in unconfined compressive strength for long time curing.

Matched MeSH terms: Compressive Strength
Fulltext Properties of laterite brick reinforced with oil palm empty fruit bunch fibres

Sallehan Ismail, Zaiton Yaacob

Pertanika Journal of Science & Technology, 2011;19(1):33-43.
MyJurnal

The development of a new, low-cost building material that is composed of non-fired, pressed laterite bricks incorporating oil palm empty fruit bunches (OPEFB) fibre was investigated in this study. The main aim of this research was to study the physical and mechanical properties of laterite brick reinforced with OPEFB fibre, including dimensions, weight, density, water absorption and compressive strength. The tests were carried out according to BS 3921:1985 for water absorption and compressive strength tests. The mix proportion of the control bricks was 70% soil, 24% sand, and 6% cement. Meanwhile, the OPEFB fibre contents ranged from 1% to 5% by weight of cement. The specimens were taken from a total of 120 bricks. The findings withdrawn from this research were: firstly, the density of laterite bricks was decreased with the increase in the OPEFB fibre content of the bricks. Secondly, it was found that the addition of the OPEFB fibres improved the compressive strength of the bricks, and the maximum compressive strength determined in this study for bricks was with 3% fibre content. Finally, the water absorption results indicated a small increase in water absorption with the increase in the OPEFB fibre content in laterite bricks.

Matched MeSH terms: Compressive Strength
Fulltext The effects of automotive Windscreen Glass Waste Powder (WGWP) on strength performance of cement mortar

Nik Anisah Nik Ngah, Mohamad Awang, Kartini Kamaruddin

Pertanika Journal of Science & Technology, 2017;25(103):63-72.
MyJurnal

This aim of this study is to study the effects of various contents of Automotive Windscreen Glass Waste Powder (WGWP) as a cement replacement. Mortar incorporating several compositions of WGWP (0%, 5%, 10%, 15% and 20%) by weight of cement was prepared. Three batching systems of cement to sand (C:S) ratios of 1:2.5 superplasticizers (SP), 1:3.0 SP and 1:3.5 SP was also employed. Fixed water to cement (w/c) ratio of 0.5 was used. The samples were water cured and the assessment of the strength performance of mortar cubes carried out at 7 and 28 days. Studies conducted have shown that WGWP has good pozzolanic properties. In term of compressive strength, it was observed that employing C:S ratio of 1:3.5 SP is better than 1:2.5 SP and 1:3.0 SP.

Matched MeSH terms: Compressive Strength
Fulltext Evaluation of cold in-place recycling mix using polymer modified Asphalt emulsion

Ahmad Kamil Arshad, Juraidah Ahmad, Mohd Izzat Asyraf Mohamad Kamal

Pertanika Journal of Science & Technology, 2017;25(107):219-226.
MyJurnal

This paper details a study conducted to evaluate the performance of cold in-place recycling (CIPR) using polymer modified asphalt emulsion (PMAE). The asphalt emulsion was modified using natural rubber latex (NRL). Four proportions of reclaimed asphalt pavement (RAP) which are 0%, 25%, 50% and 75% were mixed with natural aggregates and modified asphalt emulsion using natural rubber latex (NRL). The results showed that the optimum modified asphalt emulsion for each proportion of RAP decreased due to the increase in RAP content. Results obtained from Indirect Tensile Strength (ITS) and Uniaxial Compressive Strength (UCS) test for the mixes complied with the requirements of the Road Engineering Association of Malaysia (REAM) specifications. The unsoaked and soaked ITS values obtained were 0.2 MPa and 0.15 MPa respectively, and the minimum compressive strength of CIPR mix obtained was 0.7 MPa. Based on the evaluation of performance for the four RAP proportions, it was determined that 50% of RAP gave the best combination of the CIPR mixture.

Matched MeSH terms: Compressive Strength
Fulltext The effects of POFA and SF as TBC binder on the heat of hydration and compressive strength of mortar

Nor Umairah Abd Rahim, Mohd Fadzil bin Arshad

Pertanika Journal of Science & Technology, 2017;25(105):163-168.
MyJurnal

Ordinary Portland Cement (OPC) is widely used by the construction industry. Research to find the precise proportion of cement replacement material which can be used to produce a product called Ternary Blended Cement (TBC) is not new. The objective of this study is to determine the effect of POFA and SF as TBC on the heat of hydration and compressive strength of mortar. Before producing TBC, specimens using BBC is required. Mix design proportion for POFA and SF are 5%, 10%, 15%, and 20%. Mix design proportion TBC are chose from the highest compressive strength value achieved at 7 days of curing. This research found the heat of hydration of TBC containing 20% POFA and 5% SF is high in the beginning to drop at the end of hydration process in addition to producing lower compressive strength.

Matched MeSH terms: Compressive Strength
Fulltext The influence of Sulphate Reduction Bacteria on the durability of concrete in seawater condition

Teddy, T., Irwan, J.M., Othman, N.

Pertanika Journal of Science & Technology, 2017;25(105):117-122.
MyJurnal

Strength and durability are important characteristics of concrete and desired engineering properties. Exposure to aggressive environment threatens durability of concrete. Previous studies on bio-concrete using several types of bacteria, including sulphate reduction bacteria (SRB), had to increase durability of concrete have shown promising results. This study used mixtures designed according to concrete requirement for sea water condition with SRB composition of 3%, 5% and 7% respectively. The curing time were 28, 56 and 90 days respectively. The mechanical properties, namely compressive strength and water permeability, were tested using cube samples. The results showed compressive strength had higher increase than the control at 53.9 Mpa. The SRB with 3%composition had maximum water permeability. Thus, adding SRB in concrete specimens improves compressive strength and water permeability. This is particularly suitable for applications using chloride ion penetration (sea water condition) where corrosion tends to affect durability of concrete constructions.

Matched MeSH terms: Compressive Strength
Fulltext Structure, Properties, and In Vitro Behavior of Heat-Treated Calcium Sulfate Scaffolds Fabricated by 3D Printing

Asadi-Eydivand M, Solati-Hashjin M, Shafiei SS, Mohammadi S, Hafezi M, Abu Osman NA

PLoS One, 2016;11(3):e0151216.
PMID: 26999789 DOI: 10.1371/journal.pone.0151216

The ability of inkjet-based 3D printing (3DP) to fabricate biocompatible ceramics has made it one of the most favorable techniques to generate bone tissue engineering (BTE) scaffolds. Calcium sulfates exhibit various beneficial characteristics, and they can be used as a promising biomaterial in BTE. However, low mechanical performance caused by the brittle character of ceramic materials is the main weakness of 3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the starting powder and binder solution causes products to have high toxicity levels. A post-processing treatment is usually employed to improve the physical, chemical, and biological behaviors of the printed scaffolds. In this study, the effects of heat treatment on the structural, mechanical, and physical characteristics of 3DP calcium sulfate prototypes were investigated. Different microscopy and spectroscopy methods were employed to characterize the printed prototypes. The in vitro cytotoxicity of the specimens was also evaluated before and after heat treatment. Results showed that the as-printed scaffolds and specimens heat treated at 300°C exhibited severe toxicity in vitro but had almost adequate strength. By contrast, the specimens heat treated in the 500°C-1000°C temperature range, although non-toxic, had insufficient mechanical strength, which was mainly attributed to the exit of the organic binder before 500°C and the absence of sufficient densification below 1000°C. The sintering process was accelerated at temperatures higher than 1000°C, resulting in higher compressive strength and less cytotoxicity. An anhydrous form of calcium sulfate was the only crystalline phase existing in the samples heated at 500°C-1150°C. The formation of calcium oxide caused by partial decomposition of calcium sulfate was observed in the specimens heat treated at temperatures higher than 1200°C. Although considerable improvements in cell viability of heat-treated scaffolds were observed in this study, the mechanical properties were not significantly improved, requiring further investigations. However, the findings of this study give a better insight into the complex nature of the problem in the fabrication of synthetic bone grafts and scaffolds via post-fabrication treatment of 3DP calcium sulfate prototypes.

Matched MeSH terms: Compressive Strength
Fulltext A Comprehensive Study of the Polypropylene Fiber Reinforced Fly Ash Based Geopolymer

Ranjbar N, Mehrali M, Behnia A, Javadi Pordsari A, Mehrali M, Alengaram UJ, et al.

PLoS One, 2016;11(1):e0147546.
PMID: 26807825 DOI: 10.1371/journal.pone.0147546

As a cementitious material, geopolymers show a high quasi-brittle behavior and a relatively low fracture energy. To overcome such a weakness, incorporation of fibers to a brittle matrix is a well-known technique to enhance the flexural properties. This study comprehensively evaluates the short and long term impacts of different volume percentages of polypropylene fiber (PPF) reinforcement on fly ash based geopolymer composites. Different characteristics of the composite were compared at fresh state by flow measurement and hardened state by variation of shrinkage over time to assess the response of composites under flexural and compressive load conditions. The fiber-matrix interface, fiber surface and toughening mechanisms were assessed using field emission scan electron microscopy (FESEM) and atomic force microscopy (AFM). The results show that incorporation of PPF up to 3 wt % into the geopolymer paste reduces the shrinkage and enhances the energy absorption of the composites. While, it might reduce the ultimate flexural and compressive strength of the material depending on fiber content.

Matched MeSH terms: Compressive Strength

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