Effects of mixing technique and filler content on physical properties of bovine bone‐based CHA/PLA composites

This study presented influence of mixing technique as well as filler content on physical and thermal properties of bovine bone‐based carbonated hydroxyapatite (CHA)/poly(lactic acid) (PLA) composites. CHA/PLA composites at various contents of CHA were prepared by either melt‐mixing or solution‐mixing techniques. Thermal properties, morphologies, and mechanical properties of the CHA/PLA composites including molecular weight deterioration of PLA matrices were investigated. Average molecular weights of PLA in the composites prepared by both techniques decreased with increasing CHA content, whereas their molecular weight distributions (MWDs) increased. Nonetheless, average molecular weights of PLA in melt‐mixed composites were lower than those of solution‐mixed composites. With increasing CHA content, elongation at break, tensile strength, and impact strength of the composites were decreased, whereas the tensile moduli of the composites were increased. In comparison between two mixing techniques, the melt‐mixing distributed and dispersed CHA into PLA matrix more effectively than the solution‐mixing did. Therefore, tensile moduli, tensile strength, and impact strength of the melt mixed composites were higher than those of the solution‐mixed composites of the corresponding CHA content. Moreover, decomposition temperatures and % crystallinity of the melt‐mixed composites were higher than those of the solution‐mixed composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Properties of novel PMMA‐co‐EHA bone cements filled with hydroxyapatite

To design bone cements with predictable intraoperative and postoperative behavior, researchers must understand how cement formulations affect the polymerization reaction and specially the properties of the end product. In this study, a bioactive filler (commercial hydroxyapatite, HA) was incorporated into poly(methyl methacrylate)‐co‐ethyl hexyl acrylate (PMMA‐co‐EHA) matrices to prepare new bone cement formulations. The new PMMA‐co‐EHA/HA composites were obtained by varying the relative contents of the monomers, MMA, and EHA. The resulting composites were evaluated in terms of the curing parameters, water uptake and weight loss in phosphate buffer solution and mechanical properties. The results obtained showed that incorporation of 25% HA particles induced major changes in the final properties of the bone cements comparing with the unfilled parent matrices. In particular, the peak temperature decreased and the setting time and the bending elastic modulus increased in all formulations containing HA particles. Composites with low EHA content exhibited a decrease in strength after HA incorporation, which was attributed to the poor interfacial adhesion between the components of the composites. Additionally, the immersion results showed that the amount of 25% HA (regarding the total mass) in the composites was not enough to induce in vitro bioactive properties in the materials. POLYM. COMPOS., 35:759–767, 2014. © 2013 Society of Plastics Engineers     

Bottom‐up vs reactive sintering of Al2O3–YAG–YSZ composites via one or three‐phase nanoparticles (NPs). Bottom‐up processing wins this time

The bottom‐up approach describes the synthesis of bulk materials from the finest possible length scales to obtain the best global properties. This approach was adapted to the synthesis of multi‐phase ceramic composites produced from metal oxides produced by liquid‐feed flame spray pyrolysis (LF‐FSP). The effect of length scale of mixing was tested through two processing schemes, mixed single metal‐oxide nanopowders (NPs) and nanocomposite NPs having the desired composition within single particles. For the Al₂O₃–Y₂O₃–ZrO₂ ternary system, composites prepared from nanostructured nanoparticles sinter to finer grain sizes (<410 nm) at equivalent densities of 95%TD than those prepared from mixed nanoparticle processing. These contrast with our previous studies in this area where mixed NP processing gave the best or equivalent results. The nanocomposite NPs produced in this study exhibit novel nanostructures with three phases contained within single particles <26 nm average particle size (APS). This nanostructure may directly explain the enhanced sintering of the nanocomposite NPs and may provide an impetus for future synthesis of similarly structured NPs.     

聚苯乙烯纤维轻质混合土的抗压强度特性

通过室内无侧限抗压强度实验,研究在聚苯乙烯(EPS)轻质混合土中加入改性聚丙烯纤维,对聚苯乙烯轻质混合土强度特性的改良作用.实验材料为淤泥质粉质黏土、球状EPS颗粒、普通硅酸盐水泥、改性聚丙烯纤维,总含水率为60%,水泥掺入量为15%,EPS掺入量分别为1%、2%、3%,聚丙烯纤维掺入量分别为0、0.05%、0.1%、0.2%、0.4%.结果表明:在水泥掺入量一定时,抗压强度随纤维掺入量的增加显著提高,纤维掺入量达0.4%可以明显提高轻质混合土的无侧限抗压强度;在轻质土中加入纤维,能够提高其残余强度,提高其韧性,试样变形15%后还能保持其完整性,破坏时为塑性破坏.     

The influences of siliceous waste on blended cement properties

The influences of siliceous waste on the properties of fly ash and blast furnace slag cement were studied, and its optimum mixing amount in blended cement was determined. The strength, setting time, resistance to chemical attack, dry shrinkage, and impermeability of blended cement mixed with siliceous waste were also investigated by different experiments. The measurement of pore size distribution for hardened cement pastes made by Poremaster-60 was recorded and analyzed in this article.     

Effect of temperature and mixing conditions on quality and consistency of poly(methyl methacrylate) bone cement

Abstract

The mixing of poly(methyl methacrylate) (PMMA) bone cement has been studied to develop methods for preparing a consistently high quality cement. A novel droplet test experimental procedure was developed that characterised the wetting characteristics involved in bone cement mixing. Using this technique it was established that increased wetting occurred by mixing bone cement at a lower temperature (-28°C) than normal mixing at room temperature.

The effect of temperature on viscosity of the cement mix was also investigated. An increase in viscosity with mixing time was found for all temperatures (owing to dissolution of PMMA in the monomer). However, the rate of increase in viscosity was a function of the initial temperature of the cement components. Cooling of the components initially to -12·6°C resulted in a better mix than room temperature samples, due to the cooled components having more mixing time at a lower viscosity (less than 1000 cP).

Automated mixing of the cement was also investigated. A high speed ‘figure of eight’ mixing machine (Kerr^® Automix^TM computerised mixing dental amalgamator) was used in a comparison with traditional hand held mixing devices. The effect of initial component cooling was also investigated in the high speed unit and cement samples were analysed for porosity and homogeneity of mix (using scanning electron microscopy). Results indicate that the combined effects of low initial temperature and automated mixing produces a bone cement that is more homogeneous and of lower porosity than hand mixed cement.     

Chitosan graft copolymers‐HA/DBM biocomposites: Preparation,characterization, and in vitro evaluation

The combination of biopolymer with a bioactive component takes advantage of the osteoconductivity and osteoinductivity properties. The studies on composites containing hydroxyapatite (HA), demineralized bone matrix (DBM) fillers and chitosan biopolymer are still conducted. In the present study, the bioactive fillers were loaded onto p(HEMA‐MMA) grafted chitosan copolymer to produce a novel biocomposites having osteoinductive and osteoconductive properties. The produced composites were assessed by TGA, XRD, FTIR, and SEM techniques to prove the interaction between both matrices. In vitro behavior of these composites was performed in SBF to verify the formation of apatite layer onto their surfaces and its enhancement. The results confirmed the formation of thick apatite layer containing carbonate ions onto the surface of biocomposites especially these containing HA‐DBM mixture and pMMA having bone cement formation in their structure. These a novel biocomposites have unique bioactivity properties can be applied in bone implants and tissue engineering applications as scaffolds in future. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

石灰石粉复合粉煤灰水泥的制备及对混凝土性能影响

采用石灰石粉和Ⅲ级粉煤灰作为混合材制备复合水泥,通过粉煤灰和石灰石粉的复合比例和掺量来优化水泥性能,并用所制备的水泥配制混凝土,研究其对混凝土强度和抗裂性能的影响。结果表明:随着石灰石粉掺量的增加,复合水泥的标准稠度用水量明显下降,饱和掺量点提前,对外加剂的适应性表现良好;粉煤灰和石灰石粉的复合比例在7:3～6:4,混合材掺量为20%～40%时,可以配制出42.5和32.5的复合硅酸盐水泥;自制复合水泥所配制混凝土的工作性和强度与重庆涪陵腾辉生产的水泥差别不大,裂缝数目和面积减少,抗裂性明显改善。     

混炼方式对螺旋纳米碳纤维增强天然橡胶复合材料力学性能的影响

采用干法和湿法两种混炼工艺制备了螺旋纳米碳纤维(HCNFs)/炭黑(CB)/天然橡胶(NR)复合材料,通过扫描电镜、拉伸试验机和应变扫描仪分别对所制备复合材料的界面形貌、力学性能和Payne效应进行了测试分析,考察了混炼方式对复合材料宏观力学性能及Payne效应的影响。结果表明,与纯CB填料相比,在干湿两种混炼方式下,添加适量的HCNFs(1～6份)能提高HCNFs/CB/NR复合材料的300%定伸应力、扯断伸长率、拉伸强度和硬度。与干法混炼相比,湿法混炼能明显增强HCNFs/CB/NR复合材料的Payne效应,并提升在HCNFs高添加量(2～6份)条件下的拉伸强度和扯断伸长率,这主要源于湿法混炼能够有效改善HCNFs在橡胶基质中的分散性。     

Setting behavior,mechanical property and biocompatibility of anti-washout wollastonite/calcium phosphate composite cement

In this study, a calcium phosphate-based composite cement was fabricated by incorporating wollastonite (WS) into calcium phosphate cement (CPC). The setting behavior, microstructure, injectability, porosity, compressive strength, anti-washout property, in vitro degradation, and cell behavior of the WS/CPC composite cement were systematically investigated. The results revealed that the addition of WS promoted the hydration reaction but without affecting the hydration product of CPC. The injectability of the WS/CPC composite cement declined with the incorporation of WS to a certain extent, especially when the content of WS was higher than 20 wt%. By incorporating appropriate amount of WS into CPC, the composite cement obtained feasible setting time, enhanced compressive strength, improved anti-washout performance, and favorable biocompatibility. On the basis of its improved comprehensive application-relevant properties, the WS/CPC composite cement is prospective to be a promising biomaterial for bone defect repairing.     

Erratum

Abstract

Abstract

The physical, physicochemical and antimicrobial properties of novel cement type calcium hydroxide/nanohydroxyapatite composites were evaluated by measuring setting time, compressive strength, phase analysis, pH, water solubility and bacterial inhibition zone. Different cement pastes were obtained by mixing biphasic powders (comprising mixtures of calcium hydroxide and nanohydroxyapatite in various weight ratios) and ester of salicylic acid as liquid. Cements with different amounts of nanohydroxyapatite set at approximately 4-14?min and had a compressive strength of 8-16?MPa. The crystalline phases of the set cements were hydroxyapatite and calcium hydroxide. Finally, all composite samples showed antibacterial activity, and the larger zone of bacterial inhibition was observed in composites with higher amount of Ca(OH)₂.     

Dispersion of polymer-grafted magnetic nanoparticles in homopolymers and block copolymers

The dispersion of magnetic nanoparticles (NPs) in homopolymer poly(methyl methacrylate) (PMMA) and block copolymer poly(styrene-b-methyl methacrylate) (PS-b-PMMA) films is investigated by TEM and AFM. The magnetite (Fe₃O₄) NPs are grafted with PMMA brushes with molecular weights from M = 2.7 to 35.7 kg/mol. Whereas a uniform dispersion of NPs with the longest brush is obtained in a PMMA matrix (P = 37 and 77 kg/mol), NPs with shorter brushes are found to aggregate. This behavior is attributed to wet and dry brush theory, respectively. Upon mixing NPs with the shortest brush in PS-b-PMMA, as-cast and annealed films show a uniform dispersion at 1 wt%. However, at 10 wt%, PS-b-PMMA remains disordered upon annealing and the NPs aggregate into 22 nm domains, which is greater than the domain size of the PMMA lamellae, 18 nm. For the longest brush length, the NPs aggregate into domains that are much larger than the lamellae and are encapsulated by PS-b-PMMA which form an onion-ring morphology. Using a multi-component Flory-Huggins theory, the concentrations at which the NPs are expected to phase separate in solution are calculated and found to be in good agreement with experimental observations of aggregation.     

The effect of tricalcium silicate incorporation on bioactivity,injectability, and mechanical properties of calcium sulfate/bioactive glass bone cement

The conventional Polymethyl methacrylate (PMMA) bone cement is not biodegradable and not bioactive to bond with the native bone and causes tissue necrosis resulting from its high exothermic polymerization. Hence, biodegradable bioactive bone cements with suitable setting time and mechanical properties should be introduced. In this study, novel bioactive bone cements containing Calcium Sulfate Hemihydrate (CSH), Bioactive Glass (BG), and Tricalcium Silicate (TSC) were developed. Firstly, CSH and BG binary system was optimized based on preliminary setting and mechanical tests. Secondly, the composite bioactive bone cements were obtained by adding different quantities of TCS to the optimized CS-BG (1.3:1 wt % ratio) system. All groups exhibited desirable handling properties, an initial setting time of lower than 15 min, injectability of greater than 85%, and controlled degradability. Moreover, they demonstrated initial compressive strength values of higher than 12 MPa, superior to trabecular bone. After 28 days of hydration, the compressive strength of the cement containing 30% TCS reached 51.04 MPa. Furthermore, the present bone cements showed favorable bioactivity and bone-bonding ability as a result of calcium carbonate and hydroxyapatite (HA) formation. Furthermore, this novel bone cement exhibited appropriate biocompatibility and mesenchymal stem cell attachment, suggesting its potential for clinical applications.     

Adsorption of Silver Nanoparticles onto Different Surface Structures of Chitin/Chitosan and Correlations with Antimicrobial Activities

Size-controlled spherical silver nanoparticles (Ag NPs) can be simply prepared by autoclaving mixtures of glass powder containing silver with glucose. Moreover, chitins with varying degrees of deacetylation (DDAc < 30%) and chitosan powders and sheets (DDAc > 75%) with varying surface structure properties have been evaluated as Ag NP carriers. Chitin/chitosan-Ag NP composites in powder or sheet form were prepared by mixing Ag NP suspensions with each of the chitin/chitosan-based material at pH 7.3, leading to homogenous dispersion and stable adsorption of Ag NPs onto chitin carriers with nanoscale fiber-like surface structures, and chitosan carriers with nanoscale porous surface structures. Although these chitins exhibited mild antiviral, bactericidal, and antifungal activities, chitin powders with flat/smooth film-like surface structures had limited antimicrobial activities and Ag NP adsorption. The antimicrobial activities of chitin/chitosan-Ag NP composites increased with increasing amounts of adsorbed Ag NPs, suggesting that the surface structures of chitin/chitosan carriers strongly influence adsorption of Ag NPs and antimicrobial activities. These observations indicate that chitin/chitosan-Ag NPs with nanoscale surface structures have potential as antimicrobial biomaterials and anti-infectious wound dressings.     

Synthesis,characterization and in-vitro behavior of natural chitosan-hydroxyapatite-diopside nanocomposite scaffold for bone tissue engineering

Composite materials based on a combination of biodegradable polymers and bioactive ceramics, including chitosan and hydroxyapatite are discussed as suitable materials for scaffold fabrication. Diopside is a member of bioactive silicates; it is a good choice for hard tissue engineering because of its biocompatibility with host tissue and high mechanical strength. Chitosan and hydroxyapatite were extracted from shrimp shell and bovine bone, respectively and diopside nanoparticles were prepared by the sol-gel method. The present study reports on a chitosan composite which was reinforced by hydroxyapatite and diopside; the scaffolds were fabricated by the freeze-drying method. The so-produced chitosan-hydroxyapatite-diopside (CS-HA-DP) scaffolds were further cross-linked using tripolyphosphate (TPP) to achieve enhanced mechanical strength. The ratios of the ceramic components in composites were 5-58-37, 10-55-35, and 15-52-33 (diopside-hydroxyapatite-chitosan, w/w %). The physicochemical properties of scaffolds were investigated using Fourier-transform infrared spectrometry (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The effect of scaffolds composition on bioactivity and biodegradability were studied well. To investigate mechanical properties of samples, compression test was done. Results showed that the composite scaffold with 5% DP has the highest mechanical strength. The porosity of composites dropped from 92% to 76% by increasing the amount of DP. Cytocompatibility of the scaffolds was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase (ALP) activity, and cell attachment studies using human osteoblast cells. Results demonstrated no sign of toxicity and cells were found to be attached to the pore walls within the scaffolds; moreover, results illustrated that the developed composite scaffolds could be a potential candidate for tissue engineering.     

Evaluating chitosan/β‐tricalcium phosphate/poly(methyl methacrylate) cement composites as bone‐repairing materials

This study related to the preparation of chitosan microspheres by means of reacting chitosan with β‐tricalcium phosphate (β‐TCP) and glutaraldehyde by crosslinking reaction in the oil phase, followed by de‐oil and purification processes to get the product. Three cement composites, Pure P, C1P1, and C2P1, were prepared by the polymerization of poly(methyl methacrylate) (PMMA) bone cement in the presence of 0, 50, and 66.7% chitosan/β‐TCP microspheres, respectively. The result revealed the chitosan/β‐TCP microspheres obtained was in the size range of 50–150 μm. The presence of chitosan/β‐TCP microspheres in the prepared composites decreased the ultimate tensile strength, whereas the modulus remained the same as compared with the commercial PMMA bone cement. Addition of chitosan/β‐TCP microspheres into commercial PMMA cement significantly improved the handling property of the cement paste—that is, the increased setting time and less stickiness behavior of this paste was beneficial, in manipulation, to the operation and easier fittings to the shape and gap of the bony defect and interface. The decreased curing temperature was also less harmful to the surrounding tissues. From scanning electron micrograph observations, chitosan/β‐TCP microspheres can completely mix with bone cement powder and the prepared composites could provide scaffold for osteoblast cells growth and thus improve defects of commercial PMMA bone cement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3897–3904, 2003     

Properties of polycarbonate/acrylonitrile‐butadiene‐styrene/talc composites

The morphology, tensile, impact properties, and thermal expansion behavior of polycarbonate (PC)/acrylonitrile‐styrene‐butadiene (ABS)/talc composites with different compositions and mixing sequences were investigated. From the studies of morphology of the PC/ABS/talc composites, it was observed that some talc particles were located in both the PC and the ABS phases of the blend but most were at the interface between the PC and ABS phases for every mixing sequence. Aspect ratios of the talc particles determined by TEM image analysis reasonably matched values computed from tensile modulus using composite theory. The thermal expansion behavior, or CTE values, was not significantly influenced by the mixing sequence. The impact strength of the PC/ABS/talc composites depended significantly on the mixing sequence; a premix with PC gave the poorest toughness. The molecular weight of the PC in PC/talc composites was found to be significantly decreased. It appears that the impact strength of the PC/ABS/talc composites is seriously compromised by the degradation of the PC caused by talc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

利用荧光分析快速确定水泥混合材掺量的方法

本文通过X射线荧光仪快速检测水泥的化学组成,对多组水泥化学组分与混合材掺加比例进行分析,确定两者之间的线性关系,利用Excel中的规划求解功能建立混合材掺量预测模型。根据建立的预测模型对水泥中混合材掺量进行推算验证,从而为水泥中混合材掺量的实时监控提供一种新方法,同时可对方法进行推广,为生产企业监测混合材掺量提供参考数据,加强水泥质量控制,提升产品质量。     

Synthesis,characterization, and properties of flexible magnetic nanocomposites of cobalt ferrite–polybenzoxazine–linear low‐density polyethylene

A simple method for the preparation of magnetic nanocomposites consisting of cobalt ferrite (CF; CoFe₂O₄) nanoparticles, polybenzoxazine (PB), linear low‐density polyethylene (LLDPE), and linear low‐density polyethylene‐g‐maleic anhydride (LgM) is described. The composites were prepared by the formation of benzoxazine (BA)–CF nanopowders followed by melt blending with LLDPE and the thermal curing of BA. The composites were characterized by X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, universal testing machine measurement, and vibrating sample magnetometry. The composites consisting of LLDPE, PB, and LgM (47.5L–47.5PB–5LgM) exhibited a higher tensile strength (23.82 MPa) than pure LLDPE and a greater elongation at break (6.11%) than pure PB. The tensile strength of the composites decreased from 19.92 to 18.55 MPa with increasing CF loading (from 14.25 to 33.25 wt %). The saturation magnetization of the composites containing 33.25 wt % CF was 18.28 emu/g, and it decreased with decreasing amount of CF in the composite. The composite films exhibited mechanical flexibility and magnetic properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cytocompatibility,bioactivity and mechanical strength of calcium phosphate cement reinforced with multi-walled carbon nanotubes and bovine serum albumin

This paper reports on the in vitro cytotoxicity, bioactivity behaviour and mechanical properties of novel injectable calcium phosphate cement filled with hydroxylated multi-walled carbon nanotubes and bovine serum albumin (CPC/MWCNT-OH/BSA). To predict the in vitro bioactivity of the calcium phosphate composites, we investigated apatite formation on CPC/MWCNT-OH/BSA composites after soaking in simulated body fluid (SBF) for up to 28 days. Compressive strength tests, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and cell culture experiments with human CCD-18Co fibroblasts cell lines were performed to evaluate the effect of SBF pre-treatment on the mechanical, structural and biological properties of the CPC/MWCNT-OH/BSA composites. Although apatite formation increased significantly with SBF immersion period, the results showed that all soaked CPC/MWCNT-OH/BSA composites exhibited up to 2.5 times lower compressive strength (13–20 MPa), which were however higher than values reported for the strength of trabecular bone (2–12 MPa). Cell culture experiments showed that low concentrations (6.25 and 12.5 μg/ml) of bio-mineralised CPC/MWCNT-OH/BSA composites led to cell proliferative rather than cytotoxic effects on fibroblasts, evidenced by high cell viabilities (104–113%). The novel CPC/MWCNT-OH/BSA composites presented in this study showed favourable cytocompatible and bioactive behaviour along with high compressive strength (13–32 MPa) and are therefore considered as an attractive bone filling material.