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.

A New Selective Neural Network Ensemble Method Based on Error Vectorization and Its Application in High-density Polyethylene (HDPE) Cascade Reaction Process

Chemical processes are complex, for which traditional neural network models usually can not lead to satisfactory accuracy. Selective neural network ensemble is an effective way to enhance the generalization accuracy of networks, but there are some problems, e.g., lacking of unified definition of diversity among component neural networks and difficult to improve the accuracy by selecting if the diversities of available networks are small. In this study, the output errors of networks are vectorized, the diversity of networks is defined based on the error vectors, and the size of ensemble is analyzed. Then an error vectorization based selective neural network ensemble (EVSNE) is proposed, in which the error vector of each network can offset that of the other networks by training the component networks orderly. Thus the component networks have large diversity. Experiments and comparisons over standard data sets and actual chemical process data set for production of high-density polyethylene demonstrate that EVSNE performs better in generalization ability.

Molecular Dynamics-Based Simulation of Polyethylene Pipe Degradation in High Temperature and High Pressure Conditions

High-density polyethylene(HDPE)pipes have gradually become the first choice for gas networks because of their excellent characteristics.As the use of pipes increases,there will unavoidably be a significant amount of waste generated when the pipes cease their operation life,which,if improperly handled,might result in major environmental contamination issues.In this study,the thermal degradation of polyethylene materials is simulated for different pressures(10,50,100,and 150 MPa)and temperatures(2300,2500,2700,and 2900 K)in the framework of Reactive Force Field(ReaxFF)molecular dynamics simulation.The main gas products,density,energy,and the mean square displacement with temperature and pressure are also calculated.The findings indicate that raising the temperature leads to an increase in the production of gas products,while changing the pressure has an impact on the direction in which the products are generated;the faster the temperature drops,the less dense the air;both temperature and pressure increase impact the system’s energy conversion or distribution mechanism,changing the system’s potential energy as well as its total energy;the rate at which molecules diffuse increases with temperature,and decreases with pressure.The results of this investigation provide a theoretical basis for the development of the pyrolytic treatment of polyethylene waste materials.

Fracture Characterization of High-Density Polyethylene Materials Using the Energetic Criterias

Impact behavior of polymers has received considerable attention in recent years,and much work based on fracture mechanic approaches has been carried out.In this paper,fracture behavior in large deformation of a high density polyethylene(HDPE)materials was investigated through experimental impact testing on single edge notched specimen(SENB)and by using theoretical and analytical fracture criteria concepts.Moreover,a review of the main fracture criteria is given in order to characterize the toughness of this polymer in the both cases(static and dynamic).The fractured specimens obtained from the Charpy impact test were characterized with respect to their fracture surfaces.Characteristic zones of the fracture surface can be assigned to different stages and mechanisms of the fracture process.Finally,for a better understanding of fracture and damage mechanisms and to provide the best estimation of fracture toughness in impact,an experimental approach based on microscopic observations(SEM)was used.

Micromechanical analysis on tensile properties prediction of discontinuous randomized zalacca fibre/high-density polyethylene composites under critical fibre length

In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method and micromechanical models.These investigations were used to verify the tensile properties models toward the effect of fibre length and volume fraction on the composites.The experimental results showed that the tensile properties of composites had significantly increased due to the enhancement of fibre length.On the contrary,a decline in the tensile properties was observed with the increase of volume fraction.A comparison was made between the available experimental results and the performances of Tsai-Pagano,Christensen and Cox-Krechel models in their prediction of composites elastic modulus.The results showed that the consideration of fibre's elastic anisotropy in the Cox-Krenchel model had yielded a good prediction of the composites modulus,nevertheless the models could not accurately predict the composites modulus for fibre length study.

Characterization and Comparison of Rheological Properties of Agro Fiber Filled High-Density Polyethylene Bio-Composites

The rheological behavior of composites made with high-density polyethylene (HDPE) and different agro fiber by-products such as corncob (CCF), Rice hull (RHF), Flax shives (FSF) and Walnut shell (WSF) flour of 60 - 100 mesh were studied. The experimental results were obtained from samples containing 65 vol.% agro fiber and 3 wt.% lubricant. Particle sizes distribution of the agro fibers was in the range of 0.295 mm to ?0.125 mm. SEM showed evidence of complete matrix/fiber impregnation or wetting. The melt rheological data in terms of complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss tangent (tanδ) were evaluated and compared for different samples. Due to higher probability of agglomeration formation in the samples containing 65 vol.% of agro fillers, the storage modulus, loss modulus and complex viscosity of these samples were high. The unique change in all the samples is due to the particle size distribution of the agro fibers. The storage and loss modulus increased with increasing shear rates for all the composites, except for Walnut shell composite which exhibited unusual decrease in storage modulus with increasing shear rate. Damping factor (tanδ) decreased with increasing shear rate for all the composites at 65 vol.% filler load although there were differences among the composites. Maximum torque tended to increase at the 65 vol.% agro fiber load for all composites. Corncob and Walnut shell composites gave higher torque and steady state torque values in comparison with Flax shives and Rice hull composites due to differences in particle sizes distribution of the agro fibers.

Accurate detection method of high-density polyethylene fi lm leakage location based on secondary electric potential difference

High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the double-electrode approach.Due to the impact of the complex geoelectric environment,the electric potential and the electric potential difference are not sensitive enough to respond to minimal leakage.The tiny leaking area cannot be precisely located using the electric potential and electric potential difference.Using the COMSOL Multiphysics software,this study created a standard geoelectric model of the double-electrode method.We calculated a new parameter—the G parameter through secondary electric potential difference—based on the response characteristics of the electric potential and the electric potential difference while the HDPEfilm is leaking.The experiment demonstrates that the G parameter is more sensitive than the electric potential and electric potential difference for detecting the leaking area of HDPE film.The G parameter is more effective at detecting leakage than the electric potential and electric potential difference.The results of this study can be used to locate HDPEfilm leakage areas in a landfill.

Decorative Wood Fiber/High-Density Polyethylene Composite with Canvas or Polyester Fabric

Wood-plastic composite is an environmentally friendly material,due to its use of recycled thermoplastics and plant fibers.However,its surface lacks attractive aesthetic qualities.In this paper,a method of decorating wood fiber/high-density polyethylene(WF/HDPE)without adding adhesive was explored.Canvas or polyester fabrics were selected as the surface decoration materials.The influence of hot-pressing temperature and WF/HDPE ratio on the adhesion was studied.The surface bonding strength,water resistance,and surface color were evaluated,and observation within the infrared spectrum and under scanning electron microscopy was used to analyze the bonding process.The results showed that the fabric and WF/HDPE substrate could be closely laminated together depending on the HDPE layer accumulated on the WF/HDPE surface.The molten HDPE matrix penetrates canvas more easily than polyester fabric,and the canvasveneered composite shows a greater bonding strength than does the polyester fabric-veneered composite.A higher proportion of the thermoplastic component in the substrate improved the bonding.When the hot-pressing temperature exceeded 160°C,the fabric-veneered WF/HDPE panels had greater water resistance,although the canvas fabric changed more obviously in terms of fiber shape and color,compared with the polyester fabric.For the canvas fabric,140°C–160°C was a suitable hot-pressing temperature,whereas 160°C–180°C was more suitable for polyester fabric.The proportion of the thermoplastic component in the composite should be not less than 30%to achieve adequate bonding strength.

Studies on the Effects of Bentonite (Nanoclay) on the Mechanical Properties of High-Density Polyethylene

In this work, the effect of Bentonite (Nanoclay) on the mechanical and mor-phology properties of HDPE/Nanoclay composite pipe material was investi-gated. This led to the development of a composite material with improved me-chanical properties. The HDPE/nanoclay composites were produced using an injection moulding machine at 200?C and rotor speed of 50 rpm. The compati-bilizer used in this study was Polyethylene-graft-Maleic Anhydride. Different compositions of nanoclay reinforcements were prepared and added to HDPE resin. A particle size of 425 μm was used in proportions of 0%, 5%, 10%, 15%, and 20% on weight fraction basis. All the composites samples were characterized by Zwick Roell tensile testing machine and Scanning Election Microscopy (SEM). Experimental results obtained showed improvements in the tensile strength, and modulus at the expense of elongation. The maximum tensile strength and modulus was obtained at 10% filler composition. These enhanced properties are due to the homogenous dispersion of nanoclay in HDPE matrix, which is evident from the structure that was evaluated using SEM.

High-Density Polyethylene Based on Exfoliated Graphite Nanoplatelets/Nano-Magnesium Oxide: An Investigation of Thermal Properties and Morphology

In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. The thermal properties and morphological structures of the composites were investigated. The XRD results showed the peaks of xGnP and n-MgO, where the intensity of the xGnP peaks became stronger with adding increasing amounts of xGnP into the polymermatrix. In terms of morphology, some agglomeration of particles was observed within the matrix, and the agglomeration decreased the thermal properties of the composites. The nanocomposites showed less thermal stability than the pristine polymer. The reduction in the onset temperature compared to that of neat HDPE was attributed to less adhesion between the fillers and the matrix. In addition, the crystallinity was reduced by the addition of fillers.

Multifunctional HDPE/Cu biocidal nanocomposites for MEX additive manufactured parts: Perspectives for the defense industry

In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion(MEX)3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis(TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy(SEM), as well as atomic force microscopy(AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy(EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties(for example, it exhibited a 36.7%improvement in the flexural strength, compared to the pure matrix). At the same time, the nanocomposites were efficient against the S. aureus bacterium and less efficient against the E. coli bacterium.The use of such multi-functional, robust nanocomposites in MEX 3D printing is positively impacting applications in various fields, most notably in the defense and security sectors. The latter becomes increasingly important if one takes into account that most firearms encompass various polymeric parts that require robustness and improved mechanical properties, while at the same time keeping the risk of spreading various infectious microorganisms at a bare minimum.

HDPE与木屑热等离子体共蒸汽气化研究

以高密度聚乙烯(HDPE)和木屑为研究对象,结合热力学分析和实验研究,探究等离子体气化过程中输入功率、HDPE质量分数以及水碳比(S/C)3种工况参数对氢气产率、合成气组分、氯的产物分布等影响规律,并基于吉布斯最小自由能原理进行热力学计算。模拟分析表明:输入功率由7.5 kW增至34.0 kW过程中,氢气占比在20 kW(对应温度为800℃)时达到最大值59%;随着原料中HDPE质量分数由0增至100%,氢气占比由65%减少至56%;S/C为0时,氢气占比最高(80%),随着S/C由0增至3.0,氢气占比呈现不断减小的趋势;氯在气相中产物主要以KCl(g)、(KCl)_(2)(g)为主。实验研究表明:输入功率、HDPE质量分数和S/C对产氢量的影响趋势与热力学分析一致,在输入功率为22 kW、HDPE质量分数为80%、S/C为1.0时,最优产氢量分别达到1.52、1.51、1.38 m^(3)/kg。氯的气相占比分别在功率为22 kW、HDPE质量分数为20%、S/C为1.4时达到最高。通过对比实验结果验证了热力学模拟对等离子体气化产物特性进行定性定量分析的潜力,探索了采用热力学计算模拟生物质和HDPE等离子体共气化的可行性,并可为等离子体气化的操作优化和氯控制提供借鉴。

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。

HDPE/EUG弯曲样条的受热形状回复行为

用挤出机将高密度聚乙烯(HDPE)与杜仲胶(EUG)进行熔融共混,研究了共混比对HDPE/EUG的熔融、结晶和热力学性能及弯曲形状回复性能的影响。结果表明,随着HDPE中EUG含量的增加,结晶峰向低温方向移动,而HDPE含量的增加诱导EUG结晶温度提高。当二次升温时,当HDPE中的EUG添加量增大时,熔融峰向高温偏移,当HDPE的含量增大时,EUG的熔融峰向低温偏移。热力学测试和弯曲样品受热回复过程中,变形呈现3个温度区间分别为低温慢速区、中温快速回复区和高温下中速回复区。随着EUG含量的增加,区间转变向低温偏移,这是由于,低熔点EUG更容易发生受热活化回复现象,因此,调整共混比例可以控制形状回复速度,回复程度随加热温度而改变。

氯化聚乙烯专用HDPE树脂L5200的工业化开发及应用

通过对氯化聚乙烯专用高密度聚乙烯(HDPE)树脂市场产品研究、生产技术和下游用户需求调研,结合兰州石化淤浆法高密度聚乙烯装置实际,进行了氯化聚乙烯专用HDPE树脂L5200的工业化开发和加工应用。结果表明,氯化聚乙烯专用HDPE树脂L5200质量控制指标合理,生产方案可行,开发的L5200产品可实现在西北区域的产业化应用,促进兰州石化生产装置降本增效和地方企业扩大生产规模,具有明显的经济和社会效益。

EFFECT OF PAN-MILLING STRESS ON CRYSTAL STRUCTURES OF HIGH DENSITY POLYETHYLENE

A detailed study was performed on the crystal structures of pan-milled high-density polyethylene (HDPE) using differential scanning calorimetry (DSC) and X-ray diffraction. The crystallinity of HDPE first decreased slightly, followed by a gradual increase with increasing milling times. Monoclinic crystals appeared after 4 cycles of milling. With increasing times of milling, the proportion of monoclinic crystals increased significantly while the proportion of orthorhombic crystals decreased gradually. With increasing times of milling, the crystallite size of orthorhombic form decreased greatly, while the size of monoclinic crystallites kept almost constant during milling.

煅烧黑色页岩/HDPE复合材料及其电性能研究

为了解决黑色页岩(BS)在作为聚合物填料应用过程中与偶联剂相互作用差、所含硫元素在加工过程中异味重等问题,本研究对黑色页岩进行煅烧加工,利用XPS、FTIR、SEM等分析了煅烧对页岩组成和形貌的影响。随后制备了煅烧BS/高密度聚乙烯(HDPE)复合材料,并测试了复合材料的热学性能、力学性能和电学性能。结果表明:煅烧去除了BS中的有机质和硫铁矿,600℃下煅烧后BS的碳原子摩尔比由35.95%下降到6.98%,而硫原子摩尔比已经不可测出,页岩保持层状结构并有片层裂碎现象,且页岩层间距略有缩小。煅烧BS/HDPE复合材料的冲击强度比天然BS/HDPE的冲击强度提升显著,这是因为煅烧后的BS与HDPE之间存在大量的界面粘接,而天然BS与HDPE之间完全分离。煅烧BS/HDPE复合材料的体积电阻率维持在4.79×10^(16)Ω·cm及以上,表明煅烧BS的加入对复合材料的介电性能影响较小,复合材料拥有较好的电绝缘性能。

Effect of substrates on crystallization of high density polyethylene

The experimental observations about remarkable influence of the substrates on the isothermal crystallization rate of a high density polyethylene(HDPE) were presented.Two methods were used to characterize the crystallization rate:the change of turbidity of the HDPE specimen and the changes of the complex viscosity and storage modulus measured by a rotational rheometer,which gave consistent results showing that the isothermal crystallization rate decreased in sequence as the specimen contacted with aluminum,brass and stainless steel plates,respectively.As to the dominant influence factor,the chemical composition of the substrates can be excluded via insulating the plate by an aluminum foil.Instead,we propose the plate's ability of removing the latent heat of crystallization from the specimen.Rheological measurement is sensitive to the crystallization process.The colloid like model proposed by BOUTAHAR et al for the crystallization of HDPE gives reasonable predictions of the crystallized fraction from the measured storage modulus.

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.

Selection of Thickness of High Density Polyethylene Film for Mulching in Paddy Rice

In water deficit area, judicious use of water is essential for increasing area under crop production with limited water supply. Film Mulching has been advocated as an effective means for conserving soil moisture in rice production. The effects of high density polyethylene (HDPE) film on increasing rice production, controlling weeds and residue amount of plastic were studied under five treatments, including 5, 10, 15 and 20 μm thickness as well as bare cultivation (CK). The results indicated that the HDPE film mulching mode had significant effects on weed control, soil temperature, soil moisture, photosynthetic rate, seedling biomass, yield and residues of plastic film. Combined with economic effect, it showed that the HDPE film of 10 μm is the best option for rice production.