Rula M Allaf | German Jordanian University (original) (raw)

Papers by Rula M Allaf

Journal of Nanomaterials, 2014

The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite ... more The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite aerogels in the zinc-to-copper molar ratios of 50 : 50 to 90 : 10. A two-step mixing approach has been employed to produce aerogels composed of nano-to micrometer sized particles. The aerogels were characterized by ultrahigh resolution scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The as-synthesized aerogels had a thin flake-or petal-like microstructure comprised of clustered flakes on two size scales; they were identified as being crystalline with the crystalline species identified as copper nitrate hydroxide, zinc hydroxide chloride hydrate, and zinc hydroxide nitrate hydrate. Annealing of the aerogel materials at a relatively low temperature (400 ∘ C) resulted in a complete phase transition of the material to give highly crystalline ZnO-CuO aerogels; the aerogels consisted of networked nanoparticles in the ∼25-550 nm size range with an average crystallite size of ∼3 nm and average crystallinity of 98%. ZnO-CuO aerogels are of particular interest due to their particular catalytic and sensing properties. This work emphasizes the versatility of this sol-gel route in synthesizing aerogels; this method offers a possible route for the fabrication of aerogels of different metal oxides and their composites.

Materials Characterization, Sep 1, 2011

... On the preparation of as-produced and purified single-walled carbon nanotube samples for stan... more ... On the preparation of as-produced and purified single-walled carbon nanotube samples for standardized X-ray diffraction characterization. Rula M. Allaf a , Iris V. Rivero a , low asterisk , E-mail The Corresponding Author , Shayla S. Spearman a and Louisa J. Hope-Weeks b. ...

Journal of Applied Statistics, Aug 10, 2016

ABSTRACT Polyvinyl chloride (PVC) products are typically complex composites, whose quality charac... more ABSTRACT Polyvinyl chloride (PVC) products are typically complex composites, whose quality characteristics vary widely depending on the types and proportions of their components, as well as other processing factors. It is often required to optimize PVC production for specific applications at the highest cost efficiency. This study describes the design and analysis of a statistical experiment to investigate the effects of different parameters over the mechanical properties of PVC intended for use in electrical wire insulation. Four commonly used mixture components, namely, virgin PVC, recycled PVC, calcium carbonate, and a plasticizer, and two process variables, type of plasticizer and filler particle size, were examined. Statistical tools were utilized to analyze and optimize the mixture while simultaneously finding the proper process parameters. The mix was optimized to achieve required strength and ductility, as per ASTM D6096 while minimizing cost. The paper demonstrates how statistical models can help tailor complex polymeric composites in the presence of variations created by process variables.

Elsevier eBooks, 2018

The successful regeneration of functional tissue in scaffold-based tissue engineering heavily rel... more The successful regeneration of functional tissue in scaffold-based tissue engineering heavily relies on the scaffold design and fabrication. Generally acknowledged material, chemical, mechanical, and structural requirements of scaffolds have placed strict pre-requisites and challenges on the fabrication technologies. In general, a feasible and practical technology is anticipated to simultaneously form the internal and external architecture of the scaffold in a scalable, reproducible, controllable, and cost-effective manner. During the past two decades, biomedical research has advanced extensively to develop potentially applicable scaffolds. From a manufacturing and ecological point of view, the preparation of porous structures from a thermoplastic polymer melt is a convenient route; it allows feasible, reproducible and rapid production of scaffolds of many shapes and sizes in an economical way without involving any solvents. Melt-based scaffold fabrication technologies are derived from the conventional polymer fabrication methods; however, they are combined with other means to produce porosity in the product. Pore-generating techniques include the use of particulate porogens, gas foaming, and/or phase separation methods. Most melt-based technologies involve, in one way or another, the use of molds to produce complex 3D external shapes. These techniques typically include compression molding, extrusion, and injection molding, in addition to several modifications typically for the generation of porosity. They offer several advantages for clinical applications. For instance, scaffolds of any desired shape can be created by simply changing the mold. Moreover, various solid fillers such as hydroxyapatite fibers, as well as bioactive molecules can be employed as additives. However, drawbacks of these techniques include the possibility of excessively high molding temperatures, which can degrade and inactivate the biodegradable polymer or the bioactive molecules.

Transactions of The Canadian Society for Mechanical Engineering, Jun 1, 2017

In this paper, the effects of shot peening on the performance of TIG welded 6061-T6 Al alloy are ... more In this paper, the effects of shot peening on the performance of TIG welded 6061-T6 Al alloy are investigated. Six different scenarios are evaluated utilizing two levels of high/low shot peening intensities. The hardness profiles demonstrate a “W” shaped distribution, with low hardness values in heat affected zone, implying coarsening of precipitates. Except for ductility, the results indicate that all shot peening scenarios enhance the tensile properties of the welded specimens with respect to the unpeened control, with enhancements ranging from approximately 3 to 35%. Pre-weld low intensity shot peening results in the highest increase of tensile strength. The coefficient of friction ranges from approximately 0.4 to 0.9 compared to the unpeened control with a coefficient of approximately 0.6.

Journal of Biomedical Materials Research Part B, Apr 4, 2013

Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a no... more Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a novel solventless scaffold fabrication approach combining cryomilling and compression molding/porogen leaching techniques. This study investigated the effects of processing parameters on scaffold morphology and properties for tissue regeneration. Specifically, the effects of molding temperature, cryomilling time, and porogen mix were examined. Fifty percentage of porous scaffolds were fabricated with a range of properties: mean pore size from ∼40 to 125 μm, water uptake from ∼50 to 86%, compressive modulus from ∼45 to 84 MPa, and compressive strength at 10% strain from ∼3 to 4 MPa. Addition of 60 wt % NaCl salt resulted in a ∼50% increase in porosity in multimodal pore-size structures that depended on the method of NaCl addition. Water uptake ranged from ∼61 to 197%, compressive modulus from ∼4 to 8.6 MPa, and compressive strength at 10% strain from ∼0.36 to 0.40 MPa. Results suggest that this approach provides a controllable strategy for the design and fabrication of 3D interconnected porous biodegradable scaffolds for load-bearing tissue regeneration.

Materials, May 7, 2019

In this study, machine learning algorithms (MLA) were employed to predict and classify the tensil... more In this study, machine learning algorithms (MLA) were employed to predict and classify the tensile strength of polymeric films of different compositions as a function of processing conditions. Two film production techniques were investigated, namely compression molding and extrusion-blow molding. Multi-factor experiments were designed with corresponding parameters. A tensile test was conducted on samples and the tensile strength was recorded. Predictive and classification models from nine MLA were developed. Performance analysis demonstrated the superior predictive ability of the support vector machine (SVM) algorithm, in which a coefficient of determination and mean absolute percentage error of 96% and 4%, respectively were obtained for the extrusion-blow molded films. The classification performance of the MLA was also evaluated, with several algorithms exhibiting excellent performance.

International Journal of Polymeric Materials, Jul 20, 2016

ABSTRACT Novel nanocomposite porous scaffolds based on poly(ϵ-caprolactone) (PCL) and multiwalled... more ABSTRACT Novel nanocomposite porous scaffolds based on poly(ϵ-caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were manufactured by a compression-molding/polymer-leaching approach utilizing cryomilling for homogeneous dispersion of nanotubes and blending of polymers. Addition of MWCNTs to PCL and PCL/polyglycolide (PGA) blends resulted in significant changes to scaffold morphology compared to control samples despite persistent interconnected porosity. Several structures exhibiting rough and nanotextured surfaces were observed. Mean pore sizes were in the range of ∼3–5 µm. The nanocomposites presented good mechanical and water uptake properties. The results of this research provide significant insight into a strategy for producing nanocomposite scaffolds with interconnected porosity. GRAPHICAL ABSTRACT

Journal of Applied Polymer Science, Jun 6, 2015

ABSTRACT The apparent inability of a single biomaterial to meet all the requirements for tissue e... more ABSTRACT The apparent inability of a single biomaterial to meet all the requirements for tissue engineering scaffolds has led to continual research in novel engineered biomaterials. One method to provide new materials and fine-tune their properties is via mixing materials. In this study, a biodegradable powder blend of poly(ε-caprolactone) (PCL), polyglycolide (PGA), and poly(ethylene oxide) (PEO) was prepared and three-dimensional interconnected porous PCL/PGA scaffolds were fabricated by combining cryomilling and compression molding/polymer leaching techniques. The resultant porous scaffolds exhibited co-continuous morphologies with ∼50% porosity. Mean pore sizes of 24 and 56 μm were achieved by varying milling time. The scaffolds displayed high mechanical properties and water uptake, in addition to a remarkably fast degradation rate. The results demonstrate the potential of this fabrication approach to obtain PCL/PGA blend scaffolds with interconnected porosity. In general, these results provide significant insight into an approach that will lead to the development of new composites and blends in scaffold manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42471.

Processes, Oct 30, 2020

The present study explores solid-state cryomilling for the compounding of green composites. Herei... more The present study explores solid-state cryomilling for the compounding of green composites. Herein, wood plastic composites (WPCs) composed of sawdust (SD) and poly(ε-caprolactone) (PCL) with various compositions were prepared. Two compounding techniques, namely, extrusion and cryomilling, were utilized to prepare WPC raw material pellets and powders, respectively, for comparison purposes. Flat pressing was further utilized to prepare WPC films for testing. Morphological, structural, thermal, mechanical, and surface wettability properties were investigated. Results indicate the advantages of cryomilling in producing WPCs. Scanning electron microscopy (SEM) along with optical micrographs revealed well ground SD particles and uniform distribution in the PCL matrix. Tensile strength and elongation at break of the composites declined with increasing SD content, however, the modulus of elasticity significantly increased. Water contact angles averaged less than 90 • , implying partial wetting. Visual observations and thermo-gravimetric analysis (TGA) indicated thermal stability of composites during processing. In conclusion, PCL/SD WPC is a potential candidate to replace conventional plastics for packaging applications. This would also provide a much better utilization of the currently undervalued wood waste resources.

Processes, Jan 11, 2020

Recently, consumer markets have shown great interest in sustainable products. Considerable resear... more Recently, consumer markets have shown great interest in sustainable products. Considerable research efforts are headed towards developing biodegradable and recyclable polymers and composites. In this study, the fabrication of a wood-plastic composite (WPC) via solid state compounding has been examined. Polyethylene terephthalate (PET) and wood sawdust waste as major components of waste and challenging materials for the manufacturing of WPCs have been explored. Furthermore, the addition of poly(ε-caprolactone) as a biodegradable plasticizing agent was investigated. Composite powders were prepared by cryogenic solid-state milling (cryomilling) according to a statistical mixture design. Mechanical and water absorption properties were inspected on film samples obtained by hot pressing. Different formulations resulted in a variety of colors, textures, water interactions and mechanical properties. A sawdust content of approximately 25 vol.% was optimal for the best combination of properties. The results indicated that cryomilling is technically advantageous in the production of WPCs.

Journal of The Mechanical Behavior of Biomedical Materials, Sep 1, 2019

Solid-state milling is a promising ecologically friendly method for fabricating polymeric blend a... more Solid-state milling is a promising ecologically friendly method for fabricating polymeric blend and composite powder raw materials for several subsequent manufacturing processes. Biodegradable polymers, blends, and composites are expected to find extensive use by industry due to their environmental friendliness and acceptable mechanical and thermal properties for several applications. Poly-ε-caprolactone (PCL), poly-ethylene-oxide (PEO), and their blends have attracted so much attention to replace commodity polymers in future applications. Therefore, in the current research, bulk compounding of PCL-PEO blends with various compositions using solid-state cryomilling was investigated. Structural, mechanical, thermal, and hydrophilicity properties were examined on samples obtained by compression molding to explore the capabilities of the milling process for various applications. Morphology of the blends was explored by scanning electron microscopy (SEM), which showed a clear phase separation in blends after heating. Dispersed as well as co-continuous morphologies were achieved by varying composition. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) of the blends indicated insignificant amorphization by milling. Tensile strength, modulus, and percentage elongation at break of the blends demonstrated significant variations due to processing parameters.

Journal of Materials Science: Materials in Medicine, Jun 14, 2011

In this study, poly(e-caprolactone) (PCL)/ poly(ethylene oxide) (PEO) (50:50 wt%) immiscible blen... more In this study, poly(e-caprolactone) (PCL)/ poly(ethylene oxide) (PEO) (50:50 wt%) immiscible blend was used as a model system to investigate the feasibility of a novel solventless fabrication approach that combines cryomilling, compression molding and porogen leaching techniques to prepare interconnected porous scaffolds for tissue engineering. PCL was cryomilled with PEO to form blend powders. Compression molding was used to consolidate and anneal the cryomilled powders. Selective dissolution of the PEO with water resulted in interconnected porous scaffolds. Sodium chloride salt (NaCl) was subsequently added to cryomilled powder to increase the porosity of scaffolds. The prepared scaffolds had homogeneous pore structures, a porosity of *50% which was increased by mixing salt with the blend (*70% for 60% wt% NaCl), and a compressive modulus and strength (e = 10%) of 60 and 2.8 MPa, respectively. The results of the study confirm that this novel approach offers a viable alternative to fabricate scaffolds.

Journal of Plastic Film & Sheeting

Cryomilling is a promising method for fabricating polymeric blend and composite powder raw materi... more Cryomilling is a promising method for fabricating polymeric blend and composite powder raw materials for various subsequent manufacturing processes. In this study, biodegradable porous membranes were fabricated from poly (ε-caprolactone) (PCL) using the cryomilling/hot pressing/porogen leaching approach. Powder mixtures of six different model compositions were compounded by cryomilling; thereafter, films were fabricated by hot-pressing. Poly (ethylene-oxide) (PEO) and salt were utilized as eco-friendly porogens in these mixtures, which were dissolved in water to introduce porosity in the films. Wood sawdust (WSD) and alum were investigated as fillers potentially capable of manipulating the hydrophilicity, mechanical and antimicrobial properties of the membranes. The morphological, hydrophilicity, mechanical, and filtration efficiency properties were explored and compared to those of commercial laboratory microfiltration (MF) membranes. SEM analysis revealed dense membrane skins for ...

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2013

Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a no... more Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a novel solventless scaffold fabrication approach combining cryomilling and compression molding/porogen leaching techniques. This study investigated the effects of processing parameters on scaffold morphology and properties for tissue regeneration. Specifically, the effects of molding temperature, cryomilling time, and porogen mix were examined. Fifty percentage of porous scaffolds were fabricated with a range of properties: mean pore size from ∼40 to 125 μm, water uptake from ∼50 to 86%, compressive modulus from ∼45 to 84 MPa, and compressive strength at 10% strain from ∼3 to 4 MPa. Addition of 60 wt % NaCl salt resulted in a ∼50% increase in porosity in multimodal pore-size structures that depended on the method of NaCl addition. Water uptake ranged from ∼61 to 197%, compressive modulus from ∼4 to 8.6 MPa, and compressive strength at 10% strain from ∼0.36 to 0.40 MPa. Results suggest that this approach provides a controllable strategy for the design and fabrication of 3D interconnected porous biodegradable scaffolds for load-bearing tissue regeneration.

Materials Characterization, 2011

... On the preparation of as-produced and purified single-walled carbon nanotube samples for stan... more ... On the preparation of as-produced and purified single-walled carbon nanotube samples for standardized X-ray diffraction characterization. Rula M. Allaf a , Iris V. Rivero a , low asterisk , E-mail The Corresponding Author , Shayla S. Spearman a and Louisa J. Hope-Weeks b. ...

Biomedical sciences instrumentation, 2011

Several widely used techniques for the fabrication of three dimensional (3D) scaffolds utilize th... more Several widely used techniques for the fabrication of three dimensional (3D) scaffolds utilize the particulate leaching method to achieve a porous structure. This method involves the selective leaching of a mineral or an organic compound to generate pores. However, scaffolds prepared by this technique tend to exhibit limited interconnectivity. Therefore, to enhance the interconnectivity of the scaffolds fabricated by particulate leaching, a polymeric porogen can be added during processing. Typically porogens are mixed into a polymer solution, powder, or melt. The mixture is subsequently cast, molded, or extruded, and then leaching the porogens results in porous scaffolds. Still, even though scaffold interconnectivity is improved through the addition of polymer porogens, particulate leaching does not yield scaffolds with uniform properties. This research introduces a new solventless approach, cryomilling, to blend porogens and attain interconnected porous scaffolds with uniform morph...

Functional 3D Tissue Engineering Scaffolds

Journal of Nanomaterials, 2014

The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite ... more The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite aerogels in the zinc-to-copper molar ratios of 50 : 50 to 90 : 10. A two-step mixing approach has been employed to produce aerogels composed of nano-to micrometer sized particles. The aerogels were characterized by ultrahigh resolution scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The as-synthesized aerogels had a thin flake-or petal-like microstructure comprised of clustered flakes on two size scales; they were identified as being crystalline with the crystalline species identified as copper nitrate hydroxide, zinc hydroxide chloride hydrate, and zinc hydroxide nitrate hydrate. Annealing of the aerogel materials at a relatively low temperature (400 ∘ C) resulted in a complete phase transition of the material to give highly crystalline ZnO-CuO aerogels; the aerogels consisted of networked nanoparticles in the ∼25-550 nm size range with an average crystallite size of ∼3 nm and average crystallinity of 98%. ZnO-CuO aerogels are of particular interest due to their particular catalytic and sensing properties. This work emphasizes the versatility of this sol-gel route in synthesizing aerogels; this method offers a possible route for the fabrication of aerogels of different metal oxides and their composites.

Materials Characterization, Sep 1, 2011

... On the preparation of as-produced and purified single-walled carbon nanotube samples for stan... more ... On the preparation of as-produced and purified single-walled carbon nanotube samples for standardized X-ray diffraction characterization. Rula M. Allaf a , Iris V. Rivero a , low asterisk , E-mail The Corresponding Author , Shayla S. Spearman a and Louisa J. Hope-Weeks b. ...

Journal of Applied Statistics, Aug 10, 2016

ABSTRACT Polyvinyl chloride (PVC) products are typically complex composites, whose quality charac... more ABSTRACT Polyvinyl chloride (PVC) products are typically complex composites, whose quality characteristics vary widely depending on the types and proportions of their components, as well as other processing factors. It is often required to optimize PVC production for specific applications at the highest cost efficiency. This study describes the design and analysis of a statistical experiment to investigate the effects of different parameters over the mechanical properties of PVC intended for use in electrical wire insulation. Four commonly used mixture components, namely, virgin PVC, recycled PVC, calcium carbonate, and a plasticizer, and two process variables, type of plasticizer and filler particle size, were examined. Statistical tools were utilized to analyze and optimize the mixture while simultaneously finding the proper process parameters. The mix was optimized to achieve required strength and ductility, as per ASTM D6096 while minimizing cost. The paper demonstrates how statistical models can help tailor complex polymeric composites in the presence of variations created by process variables.

Elsevier eBooks, 2018

The successful regeneration of functional tissue in scaffold-based tissue engineering heavily rel... more The successful regeneration of functional tissue in scaffold-based tissue engineering heavily relies on the scaffold design and fabrication. Generally acknowledged material, chemical, mechanical, and structural requirements of scaffolds have placed strict pre-requisites and challenges on the fabrication technologies. In general, a feasible and practical technology is anticipated to simultaneously form the internal and external architecture of the scaffold in a scalable, reproducible, controllable, and cost-effective manner. During the past two decades, biomedical research has advanced extensively to develop potentially applicable scaffolds. From a manufacturing and ecological point of view, the preparation of porous structures from a thermoplastic polymer melt is a convenient route; it allows feasible, reproducible and rapid production of scaffolds of many shapes and sizes in an economical way without involving any solvents. Melt-based scaffold fabrication technologies are derived from the conventional polymer fabrication methods; however, they are combined with other means to produce porosity in the product. Pore-generating techniques include the use of particulate porogens, gas foaming, and/or phase separation methods. Most melt-based technologies involve, in one way or another, the use of molds to produce complex 3D external shapes. These techniques typically include compression molding, extrusion, and injection molding, in addition to several modifications typically for the generation of porosity. They offer several advantages for clinical applications. For instance, scaffolds of any desired shape can be created by simply changing the mold. Moreover, various solid fillers such as hydroxyapatite fibers, as well as bioactive molecules can be employed as additives. However, drawbacks of these techniques include the possibility of excessively high molding temperatures, which can degrade and inactivate the biodegradable polymer or the bioactive molecules.

Transactions of The Canadian Society for Mechanical Engineering, Jun 1, 2017

In this paper, the effects of shot peening on the performance of TIG welded 6061-T6 Al alloy are ... more In this paper, the effects of shot peening on the performance of TIG welded 6061-T6 Al alloy are investigated. Six different scenarios are evaluated utilizing two levels of high/low shot peening intensities. The hardness profiles demonstrate a “W” shaped distribution, with low hardness values in heat affected zone, implying coarsening of precipitates. Except for ductility, the results indicate that all shot peening scenarios enhance the tensile properties of the welded specimens with respect to the unpeened control, with enhancements ranging from approximately 3 to 35%. Pre-weld low intensity shot peening results in the highest increase of tensile strength. The coefficient of friction ranges from approximately 0.4 to 0.9 compared to the unpeened control with a coefficient of approximately 0.6.

Journal of Biomedical Materials Research Part B, Apr 4, 2013

Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a no... more Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a novel solventless scaffold fabrication approach combining cryomilling and compression molding/porogen leaching techniques. This study investigated the effects of processing parameters on scaffold morphology and properties for tissue regeneration. Specifically, the effects of molding temperature, cryomilling time, and porogen mix were examined. Fifty percentage of porous scaffolds were fabricated with a range of properties: mean pore size from ∼40 to 125 μm, water uptake from ∼50 to 86%, compressive modulus from ∼45 to 84 MPa, and compressive strength at 10% strain from ∼3 to 4 MPa. Addition of 60 wt % NaCl salt resulted in a ∼50% increase in porosity in multimodal pore-size structures that depended on the method of NaCl addition. Water uptake ranged from ∼61 to 197%, compressive modulus from ∼4 to 8.6 MPa, and compressive strength at 10% strain from ∼0.36 to 0.40 MPa. Results suggest that this approach provides a controllable strategy for the design and fabrication of 3D interconnected porous biodegradable scaffolds for load-bearing tissue regeneration.

Materials, May 7, 2019

In this study, machine learning algorithms (MLA) were employed to predict and classify the tensil... more In this study, machine learning algorithms (MLA) were employed to predict and classify the tensile strength of polymeric films of different compositions as a function of processing conditions. Two film production techniques were investigated, namely compression molding and extrusion-blow molding. Multi-factor experiments were designed with corresponding parameters. A tensile test was conducted on samples and the tensile strength was recorded. Predictive and classification models from nine MLA were developed. Performance analysis demonstrated the superior predictive ability of the support vector machine (SVM) algorithm, in which a coefficient of determination and mean absolute percentage error of 96% and 4%, respectively were obtained for the extrusion-blow molded films. The classification performance of the MLA was also evaluated, with several algorithms exhibiting excellent performance.

International Journal of Polymeric Materials, Jul 20, 2016

ABSTRACT Novel nanocomposite porous scaffolds based on poly(ϵ-caprolactone) (PCL) and multiwalled... more ABSTRACT Novel nanocomposite porous scaffolds based on poly(ϵ-caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were manufactured by a compression-molding/polymer-leaching approach utilizing cryomilling for homogeneous dispersion of nanotubes and blending of polymers. Addition of MWCNTs to PCL and PCL/polyglycolide (PGA) blends resulted in significant changes to scaffold morphology compared to control samples despite persistent interconnected porosity. Several structures exhibiting rough and nanotextured surfaces were observed. Mean pore sizes were in the range of ∼3–5 µm. The nanocomposites presented good mechanical and water uptake properties. The results of this research provide significant insight into a strategy for producing nanocomposite scaffolds with interconnected porosity. GRAPHICAL ABSTRACT

Journal of Applied Polymer Science, Jun 6, 2015

ABSTRACT The apparent inability of a single biomaterial to meet all the requirements for tissue e... more ABSTRACT The apparent inability of a single biomaterial to meet all the requirements for tissue engineering scaffolds has led to continual research in novel engineered biomaterials. One method to provide new materials and fine-tune their properties is via mixing materials. In this study, a biodegradable powder blend of poly(ε-caprolactone) (PCL), polyglycolide (PGA), and poly(ethylene oxide) (PEO) was prepared and three-dimensional interconnected porous PCL/PGA scaffolds were fabricated by combining cryomilling and compression molding/polymer leaching techniques. The resultant porous scaffolds exhibited co-continuous morphologies with ∼50% porosity. Mean pore sizes of 24 and 56 μm were achieved by varying milling time. The scaffolds displayed high mechanical properties and water uptake, in addition to a remarkably fast degradation rate. The results demonstrate the potential of this fabrication approach to obtain PCL/PGA blend scaffolds with interconnected porosity. In general, these results provide significant insight into an approach that will lead to the development of new composites and blends in scaffold manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42471.

Processes, Oct 30, 2020

The present study explores solid-state cryomilling for the compounding of green composites. Herei... more The present study explores solid-state cryomilling for the compounding of green composites. Herein, wood plastic composites (WPCs) composed of sawdust (SD) and poly(ε-caprolactone) (PCL) with various compositions were prepared. Two compounding techniques, namely, extrusion and cryomilling, were utilized to prepare WPC raw material pellets and powders, respectively, for comparison purposes. Flat pressing was further utilized to prepare WPC films for testing. Morphological, structural, thermal, mechanical, and surface wettability properties were investigated. Results indicate the advantages of cryomilling in producing WPCs. Scanning electron microscopy (SEM) along with optical micrographs revealed well ground SD particles and uniform distribution in the PCL matrix. Tensile strength and elongation at break of the composites declined with increasing SD content, however, the modulus of elasticity significantly increased. Water contact angles averaged less than 90 • , implying partial wetting. Visual observations and thermo-gravimetric analysis (TGA) indicated thermal stability of composites during processing. In conclusion, PCL/SD WPC is a potential candidate to replace conventional plastics for packaging applications. This would also provide a much better utilization of the currently undervalued wood waste resources.

Processes, Jan 11, 2020

Recently, consumer markets have shown great interest in sustainable products. Considerable resear... more Recently, consumer markets have shown great interest in sustainable products. Considerable research efforts are headed towards developing biodegradable and recyclable polymers and composites. In this study, the fabrication of a wood-plastic composite (WPC) via solid state compounding has been examined. Polyethylene terephthalate (PET) and wood sawdust waste as major components of waste and challenging materials for the manufacturing of WPCs have been explored. Furthermore, the addition of poly(ε-caprolactone) as a biodegradable plasticizing agent was investigated. Composite powders were prepared by cryogenic solid-state milling (cryomilling) according to a statistical mixture design. Mechanical and water absorption properties were inspected on film samples obtained by hot pressing. Different formulations resulted in a variety of colors, textures, water interactions and mechanical properties. A sawdust content of approximately 25 vol.% was optimal for the best combination of properties. The results indicated that cryomilling is technically advantageous in the production of WPCs.

Journal of The Mechanical Behavior of Biomedical Materials, Sep 1, 2019

Solid-state milling is a promising ecologically friendly method for fabricating polymeric blend a... more Solid-state milling is a promising ecologically friendly method for fabricating polymeric blend and composite powder raw materials for several subsequent manufacturing processes. Biodegradable polymers, blends, and composites are expected to find extensive use by industry due to their environmental friendliness and acceptable mechanical and thermal properties for several applications. Poly-ε-caprolactone (PCL), poly-ethylene-oxide (PEO), and their blends have attracted so much attention to replace commodity polymers in future applications. Therefore, in the current research, bulk compounding of PCL-PEO blends with various compositions using solid-state cryomilling was investigated. Structural, mechanical, thermal, and hydrophilicity properties were examined on samples obtained by compression molding to explore the capabilities of the milling process for various applications. Morphology of the blends was explored by scanning electron microscopy (SEM), which showed a clear phase separation in blends after heating. Dispersed as well as co-continuous morphologies were achieved by varying composition. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) of the blends indicated insignificant amorphization by milling. Tensile strength, modulus, and percentage elongation at break of the blends demonstrated significant variations due to processing parameters.

Journal of Materials Science: Materials in Medicine, Jun 14, 2011

In this study, poly(e-caprolactone) (PCL)/ poly(ethylene oxide) (PEO) (50:50 wt%) immiscible blen... more In this study, poly(e-caprolactone) (PCL)/ poly(ethylene oxide) (PEO) (50:50 wt%) immiscible blend was used as a model system to investigate the feasibility of a novel solventless fabrication approach that combines cryomilling, compression molding and porogen leaching techniques to prepare interconnected porous scaffolds for tissue engineering. PCL was cryomilled with PEO to form blend powders. Compression molding was used to consolidate and anneal the cryomilled powders. Selective dissolution of the PEO with water resulted in interconnected porous scaffolds. Sodium chloride salt (NaCl) was subsequently added to cryomilled powder to increase the porosity of scaffolds. The prepared scaffolds had homogeneous pore structures, a porosity of *50% which was increased by mixing salt with the blend (*70% for 60% wt% NaCl), and a compressive modulus and strength (e = 10%) of 60 and 2.8 MPa, respectively. The results of the study confirm that this novel approach offers a viable alternative to fabricate scaffolds.

Journal of Plastic Film & Sheeting

Cryomilling is a promising method for fabricating polymeric blend and composite powder raw materi... more Cryomilling is a promising method for fabricating polymeric blend and composite powder raw materials for various subsequent manufacturing processes. In this study, biodegradable porous membranes were fabricated from poly (ε-caprolactone) (PCL) using the cryomilling/hot pressing/porogen leaching approach. Powder mixtures of six different model compositions were compounded by cryomilling; thereafter, films were fabricated by hot-pressing. Poly (ethylene-oxide) (PEO) and salt were utilized as eco-friendly porogens in these mixtures, which were dissolved in water to introduce porosity in the films. Wood sawdust (WSD) and alum were investigated as fillers potentially capable of manipulating the hydrophilicity, mechanical and antimicrobial properties of the membranes. The morphological, hydrophilicity, mechanical, and filtration efficiency properties were explored and compared to those of commercial laboratory microfiltration (MF) membranes. SEM analysis revealed dense membrane skins for ...

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2013

Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a no... more Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a novel solventless scaffold fabrication approach combining cryomilling and compression molding/porogen leaching techniques. This study investigated the effects of processing parameters on scaffold morphology and properties for tissue regeneration. Specifically, the effects of molding temperature, cryomilling time, and porogen mix were examined. Fifty percentage of porous scaffolds were fabricated with a range of properties: mean pore size from ∼40 to 125 μm, water uptake from ∼50 to 86%, compressive modulus from ∼45 to 84 MPa, and compressive strength at 10% strain from ∼3 to 4 MPa. Addition of 60 wt % NaCl salt resulted in a ∼50% increase in porosity in multimodal pore-size structures that depended on the method of NaCl addition. Water uptake ranged from ∼61 to 197%, compressive modulus from ∼4 to 8.6 MPa, and compressive strength at 10% strain from ∼0.36 to 0.40 MPa. Results suggest that this approach provides a controllable strategy for the design and fabrication of 3D interconnected porous biodegradable scaffolds for load-bearing tissue regeneration.

Materials Characterization, 2011

... On the preparation of as-produced and purified single-walled carbon nanotube samples for stan... more ... On the preparation of as-produced and purified single-walled carbon nanotube samples for standardized X-ray diffraction characterization. Rula M. Allaf a , Iris V. Rivero a , low asterisk , E-mail The Corresponding Author , Shayla S. Spearman a and Louisa J. Hope-Weeks b. ...

Biomedical sciences instrumentation, 2011

Several widely used techniques for the fabrication of three dimensional (3D) scaffolds utilize th... more Several widely used techniques for the fabrication of three dimensional (3D) scaffolds utilize the particulate leaching method to achieve a porous structure. This method involves the selective leaching of a mineral or an organic compound to generate pores. However, scaffolds prepared by this technique tend to exhibit limited interconnectivity. Therefore, to enhance the interconnectivity of the scaffolds fabricated by particulate leaching, a polymeric porogen can be added during processing. Typically porogens are mixed into a polymer solution, powder, or melt. The mixture is subsequently cast, molded, or extruded, and then leaching the porogens results in porous scaffolds. Still, even though scaffold interconnectivity is improved through the addition of polymer porogens, particulate leaching does not yield scaffolds with uniform properties. This research introduces a new solventless approach, cryomilling, to blend porogens and attain interconnected porous scaffolds with uniform morph...

Functional 3D Tissue Engineering Scaffolds