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.

Mechanical, Thermal and Crystallization Properties of Polypropylene (PP) Reinforced Composites with High Density Polyethylene (HDPE) as Matrix

Our work aims to evaluate a complete outlook of virgin high density polyethylene (HDPE) and polypropylene (PP) polyblends. Virgin PP of 20, 30 and 50 weight% is compounded with virgin HDPE. The properties like tensile strength, flexural strength, Izod impact strength are examined. Scanning electron microscopy (SEM) and polarised light microscopy (PLM) are used to observe the surface and crystal morphology. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) tests verify the non compatibility of both polymers. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques are used to study the thermal behaviour of composites. The results manifest co-occurring spherulites for polyblends;indicating the composite to be a physical blend of continuous and dispersed phases, but on the other hand PP improves the tensile and flexural properties of HDPE.

HDPE/改性蛭石复合材料的制备与气体阻隔性能研究

利用改性后的蛭石作为填充材料,通过熔融共混法制备了高密度聚乙烯(HDPE)/改性蛭石复合材料。研究了改性蛭石的添加量对复合材料热稳定性能、结晶性能、力学性能和氧气阻隔性能的影响。结果表明,相比纯HDPE,HDPE/改性蛭石复合材料仍能保持较好的拉伸强度,当含量为1%时拉伸强度为24.1 MPa,断裂伸长率先提高后下降,当含量为0.5%时断裂伸长率达到最高为535%;改性蛭石的加入提升了材料的韧性,当改性蛭石含量为1%时材料缺口冲击强度达到最高为45.8 kJ/m^(2);HDPE/改性蛭石复合材料的氧气阻隔性能明显提升,当改性蛭石含量为1%时材料的氧气阻隔性能达到最优,氧气渗透系数为6.9×10^(-15)cm^(3)·cm/(cm^(2)·s·Pa)。

低MFR双峰HDPE标准试样的研制及应用

以低熔体流动速率(MFR)、相对分子质量分布呈双峰(简称双峰)的高密度聚乙烯(HDPE)100N粉料为原料,先用筛网除去大颗粒和微小粉末,再加入0.2%(w)抗氧剂1010和0.2%(w)抗氧剂168混匀造粒,并除去大、小粒子及异形粒子制备标准试样。对标准试样进行均匀性、稳定性检验,并进行了氧化诱导时间、熔点、结晶点、白度的稳定性实验,以及对标准试样进行了定值及统计允许区间值的确定。结果表明:低MFR双峰HDPE标准试样的MFR标称值为(0.226±0.007)g/10 min,标准试样MFR均匀、稳定。

MAPPING THE DAMAGED ZONE AROUND THE CRACK TIP IN HIGH DENSITY POLYETHYLENE WITH SYNCHROTRON MICROFOCUS SMALL ANGLE X-RAY SCATTERING TECHNIQUE

The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.

PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-BLOCK-POLY(ETHYLENE GLYCOL)COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

Study on the Basic Mechanical Behaviors of High Density Polyethylene Electrofusion Welded Joints at Different Temperature

The basic mechanical behaviors of high density polyethylene electrofusion welded joint at different temperatures were studied by using differently designed specimens in this paper. The results show that the strength of weld bonding plane is higher than that of the pipe and socket materials at room temperature. In order to get the shear strength of electrofusion welded joint, the effective bond lengths were reduced by cutting artificial groove through the socket. The effective bonding length of welded joint to get the shear strength is decreased with decreasing testing temperature. The shear strength and the sensibility to sharp notch of HDPE material increased with decreasing temperature.

HDPE/钛酸钾晶须复合材料的制备与性能研究

利用双螺杆挤出制备了高密度聚乙烯(HDPE)/钛酸钾晶须(PTW)复合材料,研究了PTW不同填充量对HDPE复合材料性能的影响。结果表明:HDPE/PTW复合材料的弯曲模量和弯曲强度随PTW含量的增加而明显增加,拉伸强度略有增加,抗冲击强度有所降低,说明钛酸钾晶须对HDPE具有较好的增刚增韧作用。同时,PTW提高了材料的耐热性能,在PTW质量含量为25%,复合材料的负荷热变形温度提高了近20℃。另外,DSC分析表明,PTW对HDPE有结晶成核作用,结晶峰温度随PTW的增加而增加,在PTW质量含量为20%时,结晶峰温度提高了3.7℃。

High density porous polyethylene material (Medpor) as an unwrapped orbital implant

Objective: To introduce the clinical effect among patients who received an unwrapped orbital implant with high density porous polyethylene material (Medpor) after enucleation or evisceration. Methods: Retrospective analysis of a series of 302 patients with anophthalmia who underwent placement of an unwrapped high density porous polyethylene orbital implant. We compared the patients (n=180) who accepted primary implant placement with those (n=122) who accepted secondary implant placement. Parameters evaluated included: age at time of surgery, date of surgery, sex, implant type and size, surgery type, the surgical procedure and technique performed, and complications. Results: The time of follow-up ranged from 2.0 to 58.0 months (mean 32.5 months). A total of 5 of 302 (1.66%) cases had documented postoperative complications. The following problems were noted after surgery: implant exposure, 3 patients (0.99%); implant removed due to orbital infection, 1 patient (0.34%); ptosis, 1 patient (0.34%). There were no significant complications observed in other 297 cases and all implants showed good orbital mo- tility. The clinical effect of primary implant placement is better than that of secondary placement. Conclusion: High density porous polyethylene material can be used successfully as an unwrapped orbital implant in anopthalmic socket surgery with minimal complications. The material is well tolerated, nonantigenic and has low rate of infection and migration.

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.

One step graft copolymerization of acrylic acid and sodium styrene sulfonate onto high-density polyethylene film by preirradiation method

High-density polyethylene (HDPE) films were irradiated by 60Co gamma ray with a dose of 100 kGy in air and then immersed in aqueous solution of acrylic acid (AA) and sodium styrene sulfonate (SSS) at different temperature. The effects of grafting conditions such as temperature, reaction time, Mohr’s salt concentration, and total concentration of monomer on grafting yield were studied. Both grafting yield of AA and SSS onto HDPE respectively increases with total concentration of monomers. The highest grafting yield was observed at 3 mol/L monomers where the grafted PE swelled to the largest extent in the monomers mixture. The grafting yield increases with reaction time and then levels off. At higher temperature, the grafting yield decreases with Mohr’s salt concentration, but increases at low temperature when Mohr’s salt concentration is 0.083%. Which can be interpreted that in the presence of Fe2+ diperoxides and hydroperoxides may decompose at low temperature to form radical which can initiate the grafting. The physical and chemical properties of grafting films were also investigated.

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。

EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. An innovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheological properties of HDPE. HDPE with higher initial molecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index. Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than for unmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flow activation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque during single screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreased markedly with increasing milling times.

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.

Study on fracture characteristic of welded high-density polyethylene pipe

Crack opening displacement(COD) was applied to characterize the fracture initiation of the tough high density polyethylene. Normal single side notched three point bend specimens and silica rubber replica techniques were used to study the characteristic COD of high density polyethylene pipe and its butt fusion joints including the weld fusion zone and heat affected zone at different temperature from -78 ℃ to 20 ℃ . Testing results show that the characteristic COD appears to depend on the structural features that are determined by welding process and the testing temperature. As the temperature is lowered, the characteristic COD of all zones studied decreases. Because the welding process significantly changes some structural feature of the material, characteristic COD of the weld fusion zone is the smallest one among those of the three zones. The results can be used for the engineering design and failure analysis of HDPE pipe.

辐照交联LDPE/HDPE发泡材料的制备与性能

采用熔融共混法和辐照交联技术制备了低密度聚乙烯(LDPE)/高密度聚乙烯(HDPE)发泡材料,研究了HDPE用量对LDPE/HDPE发泡材料加工流动性、热性能、流变性能、发泡行为、力学性能和导热性能的影响。结果表明:HDPE的加入显著提高了LDPE/HDPE发泡材料的熔体流动速率和结晶度。与纯LDPE发泡材料相比,当HDPE的质量分数为30%时,LDPE/HDPE发泡材料的拉伸强度提高了32.3%,压缩强度提高了67.5%,邵氏硬度提高了14.3%,回弹性下降了16.0%,综合性能最佳。

Improving the Dielectric Properties of High Density Polyethylene by Incorporating Clay-Nanofiller

Polymer nanocomposites have been used for various important industrial applications. The preparation of high density polyethylene composed with Na-montmorillonite nanofiller using melt compounding method for different concentrations of clay-nanofiller of 0%, 2%, 6%, 10%, and 15% has been successfully done. The morphology of the obtained samples was optimized and characterized by scanning electron microscope showing the formation of the polymer nanocomposites. The thermal stability and dielectric properties were measured for the prepared samples. Thermal gravimetric analysis results show that thermal stability in polymer nanocomposites is more than that in the base polymer. It has been shown that the polymer nanocomposites exhibit some very different dielectric characteristics when compared to the base polymer. The dielectric breakdown strength is enhanced by the addition of clay-nanofiller. The dielectric constant (εr) and dissipation factor (Tan δ) have been studied in the frequency range 200 Hz to 2 MHz at room temperature indicating that enhancements have been occurred in εr and Tan δ by the addition of clay-nanofiller in the polymer material when compared with the pure material.

桥梁拉索HDPE护套老化机理及服役寿命研究

本研究旨在探究高密度聚乙烯(high density polyethylene,HDPE)护套的老化机理及其在自然环境下的服役寿命。对HDPE护套在湿热气候(海南琼海市)和干热气候(新疆吐鲁番市)下进行了3a的自然老化试验和在干热气候(美国凤凰城)下进行1a的太阳跟踪聚光加速老化试验,对HDPE老化试验中的力学性能、分子结构、热性能、反应动力学、反应级数进行分析。结果表明,黑色HDPE护套在自然老化和太阳跟踪聚光加速老化过程中产生的特征官能团相似,热分解活化能基本相同,反应机理也一致;基于试验数据,提出了HDPE护套服役寿命模型,得出HDPE护套在中东特殊干热地区的服役寿命为15~28a,东南亚特殊湿热地区为14~20a,气候环境温和地区超过40a。本研究为预测HDPE护套在各种环境下的服役寿命提供了理论依据,也为HDPE护套材料的研发与应用提供了参考。

Characterization and Lifetime Estimation of High Density Polyethylene Containing a Prodegradant Agent

High density polyethylene (HDPE) samples, containing different concentrations of prodegradant additive d2w?, were prepared. The properties of the samples were evaluated through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheometry, and scanning electron microscopy (SEM). The work contributes to decreasing the products made of non-biodegradable polymeric materials derived from fossil sources which are have become a problem due to their increasingly inappropriate disposal and long degradation time in the environment. The obtained results indicated that there was no degradation of the samples due to processing. No significant changes in melting temperature, crystallinity, viscoelastic behavior, molecular weight and chemical composition were observed. Images from SEM analysis showed particles on HDPE surface, attributed to prodegradant additive d2w?. Oxidation Onset Temperature (OOT) results showed that the additive d2w? accelerated the degradation of HDPE. The activation energy (Ea) was determined by Ozawa-Wall-Flynn method. The obtained values were used for lifetime estimation of the samples. At 25°C, HDPE with d2w? showed a lifetime 50% higher than that of HDPE without this additive. This fact is attributed to the presence of stabilizers in masterbatch d2w? and the absence of oxygen in thermogravimetric analysis.