Effect of Preparation Methods on Mechanical Properties of PVA/HA Composite Hydrogel

Poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) composite hydrogel specimens were prepared with 15% PVA and 1%,2%, 3%, 4% and 5% HA by repeated freezing-thawing. The tests of static and dynamic mechanical properties were carried out todiscuss the influence of different contents of HA and freezing-thawing cycles on the mechanical properties of PVA/HA compositehydrogel. The results of static mechanical tests showed that the PVA/HA composite hydrogel with 3% HA and ninefreezing-thawing cycles had excellent stress relaxation properties, higher relaxation ratio, lower stress equilibrium value andpresented better properties of creep and recovery. The results of dynamic mechanical test showed that the PVA/HA compositehydrogel with nine freezing-thawing cycles had higher storage modulus and loss modulus, so was the PVA/HA compositehydrogel with 3% HA.

Properties of paper mill sludge–wood fiber–HDPE composites after exposure to xenon-arc weathering

We used paper mill sludge（PMS） to substitute for part of the wood fibers（WF） used to reinforce high density polyethylene（HDPE）.The resulting composites were subjected to xenon-arc weathering.The composite filled with limited PMS（under 10 %） had mechanical properties and aging resistance similar to those without PMS.The composites containing more PMS faded and cracked more readily than those without PMS.Based on the carbonyl index,crystallinity,and wood index,PMS appeared to accelerate the degradation of composites during weathering.Adding PMS to WF–HDPE composites reduced the weathering resistance,and this reduction was not significant if the PMS content did not exceed 20 % of the wood fibers.Therefore,PMS could be used as a reinforcement in wood-plastic composites at levels less than20 % of the wood fiber content.

Degradation Characteristic of PDLLA/HA Composite Fiber in vitro

The in vitro degradation characteristic of the poly D, L-lactic acid （ PDLIA ）/ hydroxyapatite （ HA ） compound were investigated. The compoundfibers were immersed in static phosphate buffer at 37℃ to degrade for 22 weeks. The changes in pH value of the buffer solution, the mechanical strength and morphological of inside and outside of composite fibers with degrurlation characteristic were observed. Results show that pH value of the buffer solution stabilized to aboat 7.0 before 12 weeks, however after 20 weeks that pH value quick declined. After 7 weeks that composite fibers of mechanical strength cannot mensuration. SEM observation revealed ttua bimodal degradation occurred in composite fibers.

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste

In this paper, a continuous polymeric matrix highly filled with fiber of sugarcane bagasse has been obtained and its feasibility as an ink-absorbing material has been evaluated. In order to study the effect of the amount of cellulose fiber on the surface printability, contact angle measurement using different liquids—water-based inks, ethanol and ink for ink-jet printers—and printing tests were performed on composites of high density polyethylene (HDPE) and sugarcane bagasse (SCB). The composites were processed in a Haake internal mixer, using the SCB without any previous chemical treatment or compatibilizer. The differential scanning calorimetry (DSC) and derivative thermogravimetry (TG/ DTG) revealed an increase in the thermal stability and in the degree of crystallinity of the HDPE. The optical microscopy (OM) and scanning electron microscopy (SEM) showed that the cellulosic material was homogeneously embedded within the HDPE matrix. In order to assess the resistance of the composite sample to the pull strength of the printer, tensile tests were applied to the composites and the results were compared to known paper samples. The best result was achieved in the composite with the highest content of SCB, as well as the shortest drying time.

HA/Ti composite for biomedical application by mechanical milling

In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti, HA/Ti composites with various compositions were prepared by mechanical milling. The effects of milling condition and the composition on the microstructure, the density and the hardness of the composites were studied. The results show that during the ball milling process, Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved; HA will partially decompose due to the existence of Ti and high sintering temperature. The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition. In the microstructure, Ti phase connects to be a continuous network, and HA/Ti mixtures disperse in the network. The longer the milling time, the finer the network will be. The density of HA/Ti composites decreases with the content of HA increasing and the milling time prolonging, because HA deteriorates the sinterability of Ti.The hardness of HA/Ti composites increases firstly with the content of HA increasing, and then drops when the content of HA exceeds 30%. Addition of HA will strengthen the HA/Ti composite but will decrease the density of the composite, which accounts for the effect of HA on the hardness of the composites.

Effect of porous structure on mechanical properties of C/PLA/nano-HA composites scaffold

Nonporous and porous C/PLA/nano-HA composites were fabricated by the process of solvent blending and freeze-drying technique, and the effect of porous structure on the mechanical properties of C/PLA/nano-HA composites scaffold was investigated and analyzed. The results show that the effects of porous structure on the bending strength, modulus and curves of stress and strain were obvious. Compared with nonporous sample, the curves of stress and strain of porous sample show more rough, and alternative phenomenon of stress increase and stress relaxation appears. It is strongly suggested that the fracture model of C/PLA/nano-HA composites scaffold transforms from the local to global load due to the porous structure.

The effect of Poly-ethylene-co-glycidyl methacrylate efficiency and clay platelets on thermal and rheological properties of wood polyethylene composites.

Global ecological concerns have resulted in an interest in renewable natural materials. Composites based on high density polyethylene (HDPE), wood fiber (Veneer) and containing coupling agents like nanoclay (NC) and poly-ethylene-co-glycidyl methacrylate (PEGMA) were made by melt compounding and then injection molding. In this study, the effects of two variable parameters namely nanoclay and coupling agent on the rheological and thermal properties of wood polyethylene composites (WPECs) were investigated. The study investigates the morphology phase, rheology behaviors and thermal properties by scanning electron microscope, capillary rheometer and thermal gravimetric analyzer. The SEM micrographs of the composites showed that the outer surfaces of the wood were coated by a section of amorphous lignin. The state of dispersion in HDPE/pine/clay composites was improved by EGMA because it could interact with pine flour in addition to clay. The interaction of reinforcement with coupling agent and HDPE matrix is strong based on the observation of the fracture surface of composites when EGMA is present. However the addition of 2.5% clay slightly lowered the initial degradation temperature (Td) but did not improve the thermal stability. Obviously, all the composites materials exhibit viscoelastic values greater than those of neat HDPE.

Improvement of Mechanical,Dynamic-Mechanical and Thermal Properties for Noil Ramie Fiber Reinforced Polyethylene Composites

Noil discarded fibers from fiber production for textile industry have short length and are always considered less valuable.Here,noil ramie fibers/HDPE composite is prepared using twin-screw extruder and the dynamic mechanical and thermal properties are studied.The influence of ramie fiber and maleic anhydride-grafted polyolefin(MA-g-PO)on mechanical,dynamic mechanical and thermal properties is investigated.It is observed that the tensile,flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites.Dynamic mechanical properties of the composite with MA-g-PO show an increase in the storage modulus with a higherαrelaxation peak,together with the micromorphology analysis,indicating an improved interfacial bonding between fiber and matrix by the MA-g-PO addition.Furthermore,the change in TGA thermograms of composite caused by MA-g-PO exhibits that the addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.

COMPUTATION OF FLEXURAL PROPERTIES OF HA/PLLA COMPOSITE USING A CELL MODEL APPROACH

A three-dimensional finite element analysis was conducted to evaluate the feasibility of predicting the flexural properties of hydroxyapatite-reinforced poly-L-lactide acid （HA/PLLA） biocomposite using three different schemes. The scheme 1, originated from a beam analysis, was used to determine the flexural modulus analytically while the scheme 2 and 3 were designed to have different loading and boundary conditions using a finite element cell modeling approach. An empirical approach using Chow＇s formula and experimental data were used for comparison with the predicted results. In order to reduce the computational time and save the storage space involved in determining the effect of varying particle volume fractions on the flexural properties of HA/PLLA, a superelement technique was applied. The results using the scheme 3 and the Chow＇s formula were found to be in reasonable agreement with experimental results over the range of particle volume fraction. In addition to the Chow＇s formula, local stress distribution and the failure processes in HA/PLLA were simulated using the finite element technique.

HDPE管内衬盾构隧道复合式衬砌结构极限承载力试验研究

为研究采用HDPE双壁缠绕管作为内衬的盾构隧道复合衬砌结构的破坏机理,依托桃浦污水处理厂初期雨水调蓄工程涉铁段排水隧道工程,开展整环足尺试验研究,得到如下结论:(1)复合衬砌结构破坏过程经历协调变形阶段和各自承载阶段,弹性极限点为顶底部纵缝处界面的剥离脱开,各纵缝及管片本体相继发生破坏,纵缝处填充层混凝土发生拉剪或压剪破坏;(2)复合衬砌结构的薄弱位置为各纵缝处的界面及填充层混凝土,其中顶部和腰部纵缝处最为薄弱;(3)复合衬砌结构不同位置纵缝处的界面破坏和填充层破坏形态均源自于纵缝转动变形导致刚度差异引起的界面应力和填充层应力突变。

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

Preparation and Characterization of Nano-hydroxyapatite/polyvinyl Alcohol Gel Composites

Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle process.The microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and FTIR.The results showed that the size of HA particles synthesized in PVA solution was on the nanometer scale.Both the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled water.The nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the composites.On the contrary,with high content of nano-HA particles in the composites,the particles tended to aggregate.The result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix existed.The conformation and degree of tacticity of PVA molecule changed because of the addition of HA particles.Furthermore,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.

HA/HDPE多尺度生物复合材料的制备与力学性能

采用原位矿化复合-固相挤出技术制备羟基磷灰石/高密度聚乙烯(HA/HDPE)复合材料。结果表明,原位矿化-固相挤出制备的HA/HDPE复合材料是一种纳米HA颗粒均匀分散、界面结合强度高、HA/HDPE复合纤维定向排列的多尺度结构复合材料,在纳米尺度上HA均匀分散在HDPE基体中,在微米尺度上形成HA/HDPE复合纤维,在显微尺度上定向排列的HA/HDPE复合纤维形成织构结构。该HA/HDPE多尺度结构复合材料的力学性能与传统的熔融挤出的HA/HDPE复合材料相比有显著提高,拉伸强度达到245MPa,弯曲强度达到165MPa,拉伸模量为18.1GPa,力学性能均达到人体皮质骨的力学要求。

偶联改性纳米HAP/HDPE挤出复合生物材料的力学性能和微观结构

通过化学共沉淀-水热合成法制备纳米级羟基磷灰石(HAP),再用自制模具制备出偶联剂改性纳米HAP/高密度聚乙烯(HDPE)挤出复合材料。通过SEM观察以及力学性能测试,研究了偶联剂改性纳米HAP/HDPE复合材料的微观结构和力学性能。结果表明:添加硅烷偶联剂后,HAP/HDPE复合材料的力学性能获得提高,偶联剂含量为2%(质量分数)时拉伸强度最高。而当HAP含量为20%(质量分数)时,复合材料的拉伸强度和抗弯强度最高。添加了偶联剂,HAP微粒表面与HDPE有较好的亲和性,断裂过程中应力诱发的塑性变形增加,裸露的HAP颗粒明显减少。通过口模挤出可以使得聚乙烯分子链在应力作用下伸直取向,大量平行于长轴且紧密排列的微纤维形成。

HAP／HDPE／UHMWPE复合材料的制备和表征

通过化学共沉淀-水热合成法制备纳米级羟基磷灰石(HAP),再用自制模具制备HAP/高密度聚乙烯(HDPE)/超高相对分子质量聚乙烯(UHMWPE)复合材料。通过扫描电镜观察、X射线衍射分析、热重分析、燃烧实验以及力学性能测试,研究HAP/HDPE/UHMWE复合材料的微观结构和力学性能。研究结果表明:通过口模挤出可使HDPE分子链在应力作用下伸直取向,大量平行于长轴且紧密排列的微纤维形成。UHMWPE的加入可以改善材料的微观结构,增加材料的串晶互锁结构。而HAP和聚乙烯之间只是机械地混合在一起,呈层状结构,HAP被聚乙烯组分紧紧包裹在一起,且在同一样品中HAP含量比较均匀;随着HAP含量增加,拉伸强度和抗弯强度下降,分别从170.7 MPa和160.8 MPa下降到99.2 MPa和94.3 MPa,而弹性模量有所增加,从4.9 GPa上升到5.9 GPa。

Ti-Sn-HA骨科材料的发展现状

材料科学的突破性进展,为生物医学的发展提供了更多的可能。由于Ti/HA具有的优良力学性能、生物相容性和活性,Ti/HA在生物医用材料领域备受青睐,但Ti/HA材料仍存在不少问题。主要介绍了Ti/HA存在的界面问题及改善方法,介绍了几种Ti-Sn合金在生物医用材料方面的应用,并对Ti-Sn/羟基磷灰石复合材料进行了展望。

SBS/HDPE复合高强改性沥青流变特性及微观机理研究

为了解决苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青路面抗高温性能不足及易产生车辙病害的问题,通过在SBS改性沥青中分别加入3%、4%、5%的高密度聚乙烯(HDPE),考察HDPE对SBS改性沥青性能的影响,并与单一SBS改性沥青进行对比。采用常规性能指标、温度扫描实验、频率扫描实验、荧光显微镜技术、红外光谱(FTIR)表征对复合高强改性沥青的性能进行研究。结果表明,复合高强改性沥青体系中发生了交联反应,形成了致密的网状结构,且随着HDPE掺量的增加,复合高强改性沥青的软化点、布氏黏度与车辙因子等指标呈上升趋势;与SBS改性沥青相比,其抗高温变形的能力得到显著提升。但是当HDPE掺量增加到5%时,改性剂开始产生团聚现象,对复合改性沥青的低温性能造成负面影响,基于此推荐HDPE的最佳掺量为4%。

PMMA/HA-GF复合材料

对玻璃纤维 (GF)增强聚甲基丙烯酸甲酯 (PMMA) /羟基磷灰石 (HA)复合材料的组成、成形条件和力学性能进行了研究。在PMMA中添加 5 % (质量分数 )HA微粉的复合基体与增强材料GF复合 ,70～ 10 0℃的固化和模压成形 ,可得到密度为 1.48g/cm3 ,具有生物相容性好、力学强度高、性能稳定和成形简单等特点的复合材料 。