Properties of bamboo flour/high-density polyethylene composites reinforced with ultrahigh molecular weight polyethylene

In order to improve the properties of bamboo-plastic composites (BPCs), bamboo flour/high-density polyethylene (HDPE) composites were reinforced with ultrahigh molecular weight polyethylene (UHMWPE). The effects of UHMWPE on properties of composites were studied. The crystallinity of composites decreased slightly. Compared with non-UHMWPE added bamboo powder/HDPE composite, the composite with 6 wt % UHMWPE, showed decrease in water absorption to 0.41%, whereas its tensile strength and flexural strength increased to 34.51 and 25.88 MPa, respectively, a corresponding increase of 34.59 and 12.87%. The temperatures corresponding to initial degradation temperature (T_initial) and maximum degradation temperature (T_max) of the composite increased from 282.7 and 467.4 °C to 288.5 and 474.7 °C respectively. Scanning electron microscopic images showed that UHMWPE was well dispersed and fully extended as long fibers in the composite, forming a “three-dimensional physically cross-linked network structure,” which contributed to the improved properties of the composites. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48971.     

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.     

Mechanical properties and stem cell adhesion of injection‐molded poly(ether ether ketone) and hydroxyapatite nanocomposites

A nanocomposite of poly(ether ether ketone) (PEEK) with 10 wt % hydroxyapatite (HA) was produced by extrusion and injection molding. Afterward, the samples were thermally treated. Thermal and short‐ and long‐term mechanical characterizations of the samples were made. The adhesion of human adipose stem cells (h‐ASCs) on the samples was also monitored. The ultimate tensile strength (UTS) and elastic modulus values of the nanocomposite were found to be much higher than those of trabecular bone. The impact strength of PEEK was not modified by HA; this suggested that there was no formation of large agglomerates of nanoparticles that could concentrate the stresses. With regard to fatigue life, both the thermally and nonthermally treated nanocomposites did not fail after 10⁶ cycles when maximum stresses of 30 and 50% of the UTS were applied, but they failed when the maximum applied stress was 75% of the UTS and behaved as cortical bone. After 5 days of culturing, the h‐ASCs had a higher proliferation in the nanocomposite than in pure PEEK because of the presence of HA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41748.     

Carbon nanofibre‐reinforced ultrahigh molecular weight polyethylene for tribological applications

Carbon nanofibre (CNF)‐reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of nanofibres were prepared by a novel solvent‐assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the carbon nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed carbon nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007     

Polyoxymethylene‐homopolymer/hydroxyapatite nanocomposites for biomedical applications

In this article, new polyoxymethylene (POM)/hydroxyapatite (HAp) nanocomposites for bone long‐term implants have been obtained and characterized by using FTIR, WAXD, SEM, TG, DSC, tensile tests, and in vitro evaluation. Characteristic bands both for extended chain crystals (ECC) and folded chain crystals (FCC) were observed in FTIR profiles for both pure POM and POM in POM/HAp nanocomposites. From WAXD analysis it has been found that the addition of HAp does not change the hexagonal system of POM in POM/HAp nanocomposites. Moreover, degree of crystallinity of POM increases with an increase of HAp content up to 1.0% and next decreases with an increase HAp content. It indicates that HAp nanoparticles up to 1.0% content act as effective nucleating sites. Mechanical tests revealed that Young's modulus increases, whereby, elongation at break and tensile strength decrease with increasing hydroxyapatite concentration. Results of in vitro investigations show that an increase of HAp content in POM nanocomposites facilitates formation of apatite layer on the sample surface and improves in vitro stability POM/HAp nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical characterization of high‐performance graphene oxide incorporated aligned fibroporous poly(carbonate urethane) membrane for potential biomedical applications

In this article, we report the development of graphene oxide (GO) reinforced electrospun poly(carbonate urethane) (PCU) nanocomposite membranes intended for biomedical applications. In this study, we aimed to improve the mechanical properties of PCU fibroporous electrospun membranes through fiber alignment and GO incorporation. Membranes with 1, 1.5, and 3% loadings of GO were evaluated for their morphology, mechanical properties, crystallinity, biocompatibility, and hemocompatibility. The mechanical properties were assessed under both static and dynamic conditions to explore the tensile characteristics and viscoelastic properties. The results show that GO presented a good dispersion and exfoliation in the PCU matrix, contributing to an increase in the mechanical performance. The static mechanical properties indicated a 55% increase in the tensile strength, a 127% increase in toughness for 1.5 wt % GO loading and the achievement of a maximum strength reinforcement efficiency value at the same loading. Crystallinity changes in membranes were examined by X‐ray diffraction analysis. In vitro cytotoxicity tests with L‐929 fibroblast cells and percentage hemolysis tests with fresh venous blood displayed the membranes to be cytocompatible with acceptable levels of hemolytic characteristics. Accordingly, these results highlight the potential of this mechanically improved composite membrane's application in the biomedical field. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41809.     

Multilayered ultrahigh molecular weight polyethylene/natural graphite/boron nitride composites with enhanced thermal conductivity and electrical insulation by hot compression

A scalable strategy to fabricate thermally conductive but electrically insulating polymer composites was urgently required in various applications including heat exchangers and electronic packages. In this work, multilayered ultrahigh molecular weight polyethylene (UHMWPE)/natural graphite (NG)/boron nitride (BN) composites were prepared by hot compressing the UHMWPE/NG layers and UHMWPE/BN layers alternately. Taking advantage of the internal properties of NG and BN fillers, the UHMWPE/NG layers played a decisive role in enhancing thermal conductivity (TC), while the UHMWPE/BN layers effectively blocked the electrically conductive pathways without affecting the thermal conductive pathways. The in-plane TC, electrical insulation, and heat spreading ability of multilayered UHMWPE/NG/BN composites increased with the increasing layer numbers. At the total fillers loading of 40 wt%, the in-plane TC of multilayered UHMWPE/NG/BN composites with nine layers was markedly improved to 6.319 Wm⁻¹ K⁻¹, outperforming UHMWPE/BN (4.735 Wm⁻¹ K⁻¹) and pure UHMWPE (0.305 Wm⁻¹ K⁻¹) by 33.45% and 1971.80%, respectively. Meanwhile, the UHMWPE/NG/BN composites still maintained an excellent electrically insulating property (volume resistance~5.40×10¹⁴ Ω cm ; breakdown voltage~1.52 kV/mm). Moreover, the multilayered UHMWPE/NG/BN composites also exhibited surpassing heat dissipation capability and mechanical properties. Our results provided an effective method to fabricate highly thermal conductive and electrical insulating composites.     

Preparation and characterization of ethanol-induced chitosan-glutaric anhydride hydrogel for biomedical applications

Here we report a novel, fast, and facile sythesis of chitosan-based hydrogels by ethanol directly inducing. In the present of ethanol, chitosan (CS) with glutaric anhydride (GA) could form hydrogels (CS-GA-Hs) just in few minutes. The results of ¹H NMR and FTIR confirmed N-acylation substitution of chitosan. Furthermore, the relative concentration of GA was also the critical parameter for formation and properties of CS-GA-Hs. When the concentration was 1.5, CS-GA-Hs showed the highest swelling (253.6%) and release degree (99.9%). The porous structure of CS-GA-Hs were observed by SEM and the pore size of the gels decreased from 500 to 200 μm, when the relative concentration of GA was changed from 1.5 to 4. And all the hydrogels were demonstrated a good mechanical properties. Additionally, the CS-GA-Hs showed in vitro antimicrobial activity against Staphylococcus aureus and Escherichia coli, and no cytotoxicity toward L929 mouse fibroblasts, meaning it has potential applications in biomedical fields.     

Enhanced mechanical and thermal properties of nanodiamond reinforced low density polyethylene nanocomposites

In this study, the reinforcement effects of low-content hydrophilic nanodiamond (ND) on linear low-density polyethylene (PE) nanocomposites were investigated. ND was incorporated in PE via simple solution blending. The obtained PE/ND nanocomposites were characterized using scanning electron microscopy, ultraviolet–visible spectra, X-ray diffraction, tensile test, thermogravimetry, and differential scanning calorimetry. Generally, PE/ND nanocomposites with poor interfacial interaction cause large agglomerates, resulting in brittle and poor mechanical properties. Owing to the different natures of non-polar PE and polar ND, the higher the ND content, the larger the agglomerates formed in the nanocomposites. However, PE/ND nanocomposites show unique mechanical properties, that is, the Young's modulus, tensile strength, elongation at break, and toughness increased upon the incorporation of ND. The Young's modulus of the PE/ND nanocomposites exceeded the theoretical value calculated using the Halpin–Tsai model. In addition, the toughness increased by 18% at only 0.5 wt% ND loading. Furthermore, there was an increase in the thermal degradation temperature, melting temperature, and crystallization temperature.     

宽峰聚乙烯／蒙脱土纳米复合材料的制备

利用2种不同的方法制备了2种氢调敏感性不同的蒙脱土／氯化镁／四氯化钛（MMT／MgCl2／TiCl4）催化剂,利用这2种催化剂及其混配催化剂,通过原位聚合法,制备出一系列宽峰聚乙烯纳米复合材料,采用X_射线衍射仪（XRD）、凝胶色谱测试分析（GPC）及力学性能测试等方法对催化剂及聚合产物进行分析,结果表明,2种催化剂以及按照不同比例混合的混配催化剂均表现出较高的聚合活性,XRD测试结果表明,蒙脱土片层在乙烯聚合过程中发生了插层及剥离,以单片层或几层共存的形式分散于聚乙烯基质中;用混配催化剂可制得宽峰聚乙烯纳米复合材料,Mw／Mn=7．23,并且聚合物的堆积密度达到工业生产的标准,宽峰聚乙烯纳米复合材料的综合力学性能较工业产品5000S及工业上应用的管材料有很大的提高。     

Recent advances in nanocellulose for biomedical applications

Nanocellulose materials have undergone rapid development in recent years as promising biomedical materials because of their excellent physical and biological properties, in particular their biocompatibility, biodegradability, and low cytotoxicity. Recently, a significant amount of research has been directed toward the fabrication of advanced cellulose nanofibers with different morphologies and functional properties. These nanocellulose fibers are widely applied in medical implants, tissue engineering, drug delivery, wound‐healing, cardiovascular applications, and other medical applications. In this review, we reflect on recent advancements in the design and fabrication of advanced nanocellulose‐based biomaterials (cellulose nanocrystals, bacterial nanocellulose, and cellulose nanofibrils) that are promising for biomedical applications and discuss material requirements for each application, along with the challenges that the materials might face. Finally, we give an overview on future directions of nanocellulose‐based materials in the biomedical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41719.     

Preparation,dynamic rheological behavior,crystallization, and mechanical properties of inorganic whiskers reinforced polylactic acid/hydroxyapatite nanocomposites

The novel inorganic SiO₂–MgO–CaO whiskers (SMCWs) were incorporated into nano hydroxyapatite (HA) contained polylactic acid (PLA) system to prepare the reinforced PLA/HA/SMCWs nanocomposite. Maleic anhydride grafted PLA (PLA‐g‐MAH) was then used to modify the interface between filler and matrix. The morphology, rheological behavior, crystallization, and mechanical property of the prepared nanocomposites were systematically investigated using scanning electronic microscope, dynamic rheometer, differential scanning calorimeter, polarized light microscope, and mechanical test, respectively. The results showed that the introduced PLA‐g‐MAH obviously improves the filler dispersion and the filler–matrix interfacial compatibility. Interestingly, the incorporated whiskers obviously decrease the complex viscosity and hence could significantly improve the processability of system. However, the introduction of PLA‐g‐MAH increases the complex viscosity to a greater extent. In addition, the added whiskers were found to have complicated influences on the PLA crystallization. On one hand, the incorporated whiskers can enhance the melt crystallization capability of PLA macromolecular chains; on the other hand, the introduced whiskers also show the inhibitive effect on the nucleation of PLA polymer chains and the inhibition degree is related to the loading of whiskers. The combination of whiskers and PLA‐g‐MAH could remarkably improve the mechanical performance of PLA/HA nanocomposite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43381.     

Effect of polyethylene glycol molecular weight on cell growth behavior of polyvinyl alcohol/carboxymethyl cellulose/polyethylene glycol hydrogel

Polyvinyl alcohol (PVA)/carboxymethyl cellulose (CMC)/polyethylene glycol (PEG) hydrogel scaffolds are synthesized using cyclic freezing/thawing and subsequent γ-ray irradiation to evaluate the effect of the molecular weights of PEG (200, 400, 1,000, and 2,000) on strength and cell growth behavior of the hydrogels. As the PEG weight increases from 200 to 2,000, the compressive strength and the pore size decreases gradually from 58.0 ± 8.2 kPa to 17.7 ± 6.1 kPa and from 22.7 ± 3.9 μm to 8.5 ± 1.6 μm, respectively. However, the highest swelling rate is obtained for PVA/CMC/PEG400 hydrogels. The irradiated PVA/CMC/PEG400 hydrogels exhibit tailored properties of the swelling rate of 1,148 ± 34.0%, the compressive strength of 42.5 ± 6.6 kPa, the pore size of 14.6 ± 1.9 μm, and cell viability of 184%. In addition, the fastest L-929 cell proliferation and growth with time, verified by the cell proliferation (0–48 hr) and the scratch assay (0–15 hr), was observed for the PVA/CMC/PEG400 hydrogels, indicating that they are highly suitable for potential wound dressings that require fast healing regeneration.     

Viscous behavior of ultrahigh molecular weight polyethylene solution

The viscous behavior of the decalin solution of ultrahigh molecular weight polyethylene (UHMEPE) was studied. The influence of the concentration of polymer as well as the temperature was investigated. The flow curve can be described by the power-law model. The dependence of the viscosity on the temperature can be described by the Arrhenius–Frenkel–Eyring equation. The dependence of viscosity on the concentration can also be described by a power-law correlation. The addition of aluminum stearate increased the activation energy of flow of the solution. The viscosity of UHMWPE solution was decreased at lower concentration and increased at higher concentration of UHMWPE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:289–293, 1997     

Reversible control of biomaterial properties for dynamically tuning cell behavior

In the past decade, significant advances in chemistry and manufacturing have enabled the development of increasingly complex and controllable biomaterials. A key innovation is the design of dynamic biomaterials that allow for user-specified, reversible, temporal control over material properties. In this review, we provide an overview of recent advancements in reversible biomaterials, including control of stiffness, chemistry, ligand presentation, and topography. These systems have wide-ranging applications within biomedical engineering, including in vitro disease models and tissue-engineered scaffolds to guide multistep biological processes.     

Plasticized P(VDF-TrFE): A new flexible piezoelectric material with an easier polarization process,promising for biomedical applications

In this work, flexible ferroelectric films of P(VDF-TrFE) softened by a plasticizer are elaborated. Morphology, piezoelectric, mechanical, thermal, and crystalline properties of the films are studied. We show that the elastic constant is reduced up to 30% while increasing the remanent polarization and the piezoelectric coefficient thanks to the lubricant property of the plasticizer, helping the orientation of the crystallites. Plus, the decrease of the coercive field from 46 to 32 V/μm after an annealing at 138°C for a plasticizer content ranging between 20 and 50 wt% is observed and an explanation by based on a polymer/plasticizer demixing is provided. It leads to an easier polarization process with a significant saving in time and applied electric field reducing the breakdown voltage. Both effects could be interesting for an industrial production. Finally, a first sensor is elaborated and characterized electrically with homemade test bench. We show that the softening of the P(VDF-TrFE) offers to the device a larger amplitude range of deformations. The combination of the flexibility with high ferroelectric properties of the plasticized P(VDF-TrFE) make it a very promising material for biomedical sensor applications.     

Zirconia ceramics with additions of Alumina for advanced tribological and biomedical applications

The results of an investigation on slip cast and sintered Y₂O₃ (3 wt%)- stabilized ZrO₂ with additions of 5, 10, 15 wt% Al₂O₃ are reported. The surface roughness, porosity and density of the samples were measured. The hardness HRc and Hv, fracture toughness K_1C, and friction coefficients were also measured using standard methods. The structural properties of the samples were observed by Scanning Electron Microscopy (SEM). The surface topography was evaluated by means of Chromatic White Light Interferometry using MicroSpy® Topo of FRT Rauheit Kontur before and after tribological tests. The phase and chemical composition were analyzed by X-Ray Diffractometry (XRD), Energy Dispersive X-ray (EDX) spectroscopy, and Raman spectroscopy. Results show that the addition of Al₂O₃ into YSZ ceramics in the range of 5–10% allows the mechanical and tribological characteristics of the material that can be applied in different mechanical machines for different metallurgical processes to be improved, as well as in chemical engineering or medicine.     

Xanthan gum: A versatile biopolymer for biomedical and technological applications

Xanthan gum is an extracellular polymer produced mainly by the bacterium Xanthomonas campestris. Traditionally it plays an important role in industrial applications as thickener, emulsion stabilizer and it has been added to water‐based drilling fluids due to its pseudoplastic behavior and thermal stability. The structural properties of xanthan in solution can be tuned by the temperature and ionic strength; under high ionic strength or low temperature, xanthan chains are arranged in helical conformation, whereas under low ionic strength or high temperature, xanthan chains are coiled. Xanthan high molecular weight favors the building up of physical and chemical networks, which have been used as carriers for drugs and proteins and as scaffolds for cells. In combination with other polymers xanthan has been applied as excipient in tablets or as supporting hydrogels for drug release applications, particularly due to its acid resistance. The large versatility of xanthan gum opens the possibility for the creation of new architectures and additional applications involving this fascinating polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42035.     

Oxidation resistance and abrasive wear resistance of vitamin E stabilized radiation crosslinked ultra‐high molecular weight polyethylene

The effect of gamma radiation on the oxidation and wear resistance of ultra‐high molecular weight polyethylene (UHMWPE) has been extensively studied since these properties are critical for the longevity of UHMWPE components of total joint replacement prostheses. While gamma radiation increases wear resistance of UHMWPE, the free radical generated in the lamellar regions by radiation must be stabilized before oxidative degradation occurs as the polymer ages. Initially, post‐radiation melting conducted to quench free radicals but this treatment also decreases its mechanical properties. Recently, it has been replaced by incorporation of Vitamin E into UHMWPE to combat oxidative degradation. In this study, we assessed wear resistance of Vitamin E stabilized UHMWPE under abrasive wear conditions and oxidation resistance by shelf‐aging irradiated components for 2 years. Equilibrium swelling experiments showed that Vitamin E decreased crosslink density, which affected wear resistance, but oxidation resistance was better preserved with increasing concentration of Vitamin E. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44125.