Recovery of recycled acrylonitrile–butadiene–styrene,through mixing with styrene–ethylene/butylene–styrene

Recovery of recycled acrylonitrile–butadiene–styrene (ABS) through mixing with styrene–ethylene/butylene–styrene (SEBS) has been studied in this paper. To simulate recycled ABS, virgin ABS was processed through 5 cycles, at extreme processing temperatures, 220 °C and 260 °C. The virgin ABS, the virgin SEBS, the recycled ABS and the mixtures were mechanically, thermally and rheologically characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. With these data and using Computer Aided Engineering (CAE) the injection process was simulated by obtaining the optimal injection process parameters. Mixtures were injected at two temperatures in a sensorised mold correlating the shrinkage of the parts with temperature.The results show that tensile strength of ABS remains practically constant as the number of reprocessing cycles increases, while in the material injected with SEBS the tensile strength decreases. Concerning the Charpy notched impact strength; the values of the ABS reprocessed at 220 °C remain more or less unchanged, while the values for 260 °C show a significant decrease. The adhesion of the SEBS causes, in both cases, an increase in impact strength. DSC techniques enabled us to observe how the glass transition temperature (T_g) remains more or less constant regardless of the number of cycles or the temperature, whereas the crosslinking is much greater in the samples reprocessed at 260 °C.Finally, the viscosity decreases with each cycle and this decrease becomes even more noticeable with the addition of SEBS, and also that the parts molded at lower temperatures have less shrinkage.     

Influence of temperature and shear rate on the rheology and processability of reprocessed ABS in injection molding process

The effects of reprocessing on the processability of two Acrylonitrile–Butadiene–Styrene (ABS) grade thermoplastic polymers have been investigated. Reprocessing in an injection molding process of a low and a high viscosity ABS grade has been done changing operating temperatures and shear rates, design of experiments (DOE) techniques were applied to plan experiments and later analysis. The flow properties of virgin and reprocessed materials have been evaluated by capillary rheology.Experimental results clearly indicate a qualitatively different behavior of the two polymers upon reprocessing. Low viscosity grade shows a reduction of viscosity upon increasing the number of processing cycles, thus confirming the degradation of this polymer. High viscosity grade, conversely, shows an increase of melt viscosity as the number of injection molding cycles is increased. It has been confirmed that applied shear rates in injection molding process affect material behavior as well as applied temperatures.     

The effect of reprocessing on the mechanical properties of the waste fabric reinforced composites

In this study, waste cotton fabric reinforced polymer matrix composite plate has been processed by a-custom-made recycling extruder. Two different (12.5% and 25% fibers by weight) waste fabric reinforced composite plates were produced and reprocessed six times to assess repetition effect of processing on the mechanical and rheological properties on plates. Effects of reprocessing were evaluated by the tensile testing and impact testing besides SEM, DSC, XRD and MFI rheological and characterization analysis. Test results of composite plates were compared with the pure low density polyethylene (LDPE) plate. Test results show that the tensile strength was increased till the 4th reprocessing step while reducing impact properties. In further reprocessing, tensile properties have been decreased as a consequence of the fabric/fiber damage. Thermal effect of reprocessing was limited according to the comprehensive characterization and rheological analysis.     

Optimization of mechanical properties of recycled plastic products via optimal processing parameters using the Taguchi method

The large amount of plastic products presently produced necessitates recycling and reuse of these non-biodegradable materials. However, the degradation in the mechanical properties of products made from recycled plastic is a major drawback that limits their use. This study aims to improve the mechanical properties of products made from recycled plastic by utilizing the Taguchi optimization method, instead of coupling the products with additives. By adopting L₉ Taguchi OA, products made from various compositions of virgin and recycled plastic are produced by injection moulding. Four controllable factors (i.e., melt temperature, packing pressure, injection time, and packing time), each at three levels, are tested to determine the optimal combination of factors and levels in the manufacturing process. By determining the optimal combination of factors and levels, the appropriate blending ratio of virgin and recycled plastic can be evaluated from the mechanical performance exhibited by the compound. The effects of the optimal processing parameters and the addition of recycled plastic in various compositions on the mechanical properties and melt flow index of the produced parts are also investigated. The results reveal that the product made of 25% recycled polypropylene (PP) and 75% virgin PP exhibits a better flexural modulus compared to the virgin form. The same product exhibits a 3.4% decrease in flexural strength. The degradation in mechanical properties of products produced from recycled plastic can be improved by optimizing the influence processing parameters during the manufacturing process.     

Reclamation and additional alloying of 18Ni(350) maraging steel

The possibility of gainfully utilizing grade 18Ni(350) maraging steel scrap has been investigated, along with the effect of additional alloying with niobium. A vacuum induction melting and casting furnace was used for melting and additional alloying. The cast ingots were hot forged and their properties compared with those of the stock material. The composition of the reprocessed material was found to be within the prescribed range for 18Ni(350) steel, except for some loss in titanium content. The hardness and tensile strength of the recycled steel were similar to those of the stock material. A slight decrease in hardness in the aged condition could be attributed to loss of titanium during remelting. Charpy V- notch impact test-ing indicated significantly higher toughness in the remelted material; this has been attributed to a homo-geneous, refined microstructure and a lower level of inclusions. Additional alloying with 2% Nb not only improved the mechanical properties but also affected the amount of reverted austenite obtained after ag-ing.     

超声辐照对碳纳米管增强环氧树脂黏度和力学性能的影响

采用超声辐照处理多壁碳纳米管增强环氧树脂复合材料,分析了超声辐照条件对复合材料的黏度、力学性能及拉伸断口显微形貌的影响。结果表明:温度一定时,多壁碳纳米管增强环氧树脂体系的黏度随超声辐照时间的延长而逐渐降低;超声辐照时间为5min时,环氧树脂的拉伸强度、弯曲强度、拉伸剪切强度达到最大值,较处理前分别提高了37%,167%和86%;经超声辐照后,拉伸断口形貌显示出更多的韧性断裂特征。     

Fluidity,Microstructure, and Tensile Properties of Sub-rapidly Solidified Mg-6Al-4Zn-xSn(x=0,0.6,1.2,1.8) Alloy

In this paper, the infl uence of the Sn element on the melt viscosity, grain size, shrinkage, and tensile properties of the subrapidly solidified Mg-6Al-4Zn alloy was studied. The results showed that the melt viscosity of the Mg-6Al-4Zn alloy was greatly decreased because of the addition of Sn. As the content of Sn increased from 0 to 1.8 wt.%, the grain size of the alloy was refined, and the dendrite microstructure was changed to rose-shaped ones simultaneously. The decreased melt viscosity and refined microstructure were conductive to the feeding of melt, which contributed to the reduction in volume fraction of shrinkage. The volume fraction of shrinkage of the Mg-6Al-4Zn-1.2 Sn alloy was reduced by 30.8%, compared with that of the alloy without Sn addition. Tensile properties of the Mg-6Al-4Zn-x Sn alloys were increased firstly and then decreased with the augmented Sn content. The yield strength, ultimate tensile strength, and elongation of the alloy containing 1.2 wt.% Sn were 21.4%, 39.5%, and 259.0% higher than those of the alloy without Sn addition, respectively. The addition of Sn was considered to reduce the shrinkage of the sub-rapidly solidified Mg-6Al-4Zn magnesium alloy and thus improved its tensile properties. To identify the mechanism, the effect of Sn on the volume fraction of shrinkage was discussed from three aspects of melt viscosity, grain refinement, and volume fraction of eutectic phases.     

Effect of reprocessing and accelerated ageing on thermal and mechanical polycarbonate properties

The feasibility of reprocessing has been investigated as a possible alternative of polycarbonate recycling. The effect on thermal and mechanical properties of polycarbonates after up to 10 reprocessing cycles and the effect of the combined reprocessing and accelerated weathering were analyzed. Measurements collected after each molding cycle revealed a slight decrease of thermal properties. The same behaviour was observed from accelerated weathering tests. Neither the modulus of elasticity nor the tensile strength was affected in the first seven reprocessing cycles, whereas the impact strength decreased sharply. However, accelerated weathering showed that only after the first reprocessing cycle there was an important influence of the number of reprocessing cycles on the mechanical properties.     

Comparison Between Structures and Properties of ABS Nanocomposites Derived from Two Different Kinds of OMT

In the present work, the hexadecyl triphenyl phosphonium bromide (P16) and cetyl pyridium chloride (CPC) were used to modify montmorillonite (MMT) based on the structural characteristic of the engineering thermoplastic acrylonitrile-butadiene-styrene copolymer (ABS) and the principle of “like dissolves like”, and then used to prepare the ABS/organic-modified montmorillonite (OMT) nanocomposites by melt-intercalation method. The influences of two different kinds of OMT on the structures and properties of the ABS nanocomposites were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), thermogravimetric analyses (TGA), Cone calorimetry and dynamic mechanical analyses (DMA), respectively. The increased basal spacing showed that ABS intercalated into the gallery of the OMT. The morphology indicated that the OMT dispersed well in the ABS resin and the intercalated structure for ABS/OMT-P16 nanocomposites and intercalated-exfoliated structure for ABS/OMT-CPC nanocomposites were respectively formed. The TGA results revealed that onset temperature of thermal degradation and charred residue at 700 °C of the ABS nanocomposites was remarkably enhanced compared to the pure ABS. It was also found from the Cone calorimetry tests that the peak of heat release rate (PHRR) decreased significantly, contributing to the reduced flammability. The DMA measurements indicated that the loading of silicate clays improved the storage modulus of the ABS resin. The partial exfoliation of the OMT-CPC within ABS nanocomposites was advantageous to increasing thermal stability properties, decreasing flammability properties, and improving mechanical properties.     

行波磁场对ZL205A合金薄壁铸件凝固缺陷和力学性能的影响

研究了凝固过程中局部加载行波磁场对ZL205A合金薄壁件缩孔、缩松和力学性能的影响。利用扫描电子显微镜对制备试样的显微组织进行分析,采用电子万能材料试验机对铸件力学性能进行测试。结果表明:与相同条件下获得的未施加行波磁场的铸件进行对比,施加行波磁场的铸件缩孔、缩松缺陷得到大幅改善;经过T6热处理后,抗拉强度、屈服强度、延伸率分别由436.61 MPa、390.22 MPa、3.29%提高到470.24 MPa、416.97 MPa、4.15%,抗拉强度和屈服强度分别提高了33.63 MPa、26.75 MPa,延伸率提高了26.14%。     

Fatigue strength and microstructure evaluation of Al 7050 alloy wires recycled by spray forming,extrusion and rotary swaging

Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7xxx alloys. The 7050 alloy machining chips were spray formed, hot extruded, rotary swaged and heat-treated in order to improve mechanical properties. Microstructures, tensile properties and fatigue strength results for a 2.7 mm-diameter recycled wire are presented. Secondary phases and precipitates were investigated by XRD, SEM, EBSD, TEM and DSC. As-swaged and heat-treated (solution and aging) conditions were evaluated. Mechanical properties of both conditions outperformed AA7050 aerospace specification. Substantial grain refinement resulted from the extensive plastic deformation imposed by rotary swaging. Refined micrometric and sub-micrometric Al grains, as well as coarse and fine intermetallic precipitates were observed. Subsequent solution treatment resulted in a homogeneous, recrystallized and equiaxed microstructure with grain size of 9 μm. Nanoscale GP(I) zones and η′ phase precipitates formed after aging at 120 °C, imparting higher tensile (586 MPa) and fatigue (198 MPa) strengths.     

ABS塑料与6082铝合金搅拌摩擦点焊工艺及机理

针对2 mm厚的ABS塑料板和6082-T6铝合金进行搅拌摩擦点焊可焊性试验,并将成形较好的试件的横截面的形貌进行了观察分析,并对其进行力学性能的测试.结果表明,将铝合金板放在上,塑料板放在下的搭接方式可以实现良好的连接;最优工艺参数为搅拌头旋转速度为400 r/min,焊接时间为30 s,所得焊接接头的抗拉剪载荷最大为3.31 kN;点焊接头有两种断裂模式.     

热镀锌法提高B82 MnQL材料的抗拉强度研究

目的增强B82Mn QL材料的抗拉强度。方法以B82Mn QL盘条作为热镀锌的试验材料,利用拉伸试验机、反复弯曲试验机对其力学性能进行测试,借助金相显微镜、扫描电镜分析几种镀锌工艺下的横截面和轴向截面以及拉拔断口的组织形貌,同时测试显微硬度。结果 B82Mn QL盘条拉拔后钢丝的抗拉强度由原来的1250 MPa提高至1670 MPa。断面收缩率由32.5%下降至7%。采用新镀锌工艺和助镀配方,B82Mn QL钢丝镀锌后抗拉强度下降幅度为8%,低于传统的10%~15%。稳定化后B82Mn QL的扭转次数为20次左右,反复弯曲次数为6次左右,强度由1650 MPa提高至1710 MPa,硬度值比镀锌后有较大提高,由镀锌后的430HV升高至450HV,而且分布均匀。结论通过优化镀锌工艺,能大幅提高B82Mn QL盘条的抗拉强度。     

多次返回对镍基合金K446组织与性能的影响

研究返回次数对K446合金成分、组织与力学性能的影响。结果表明:随返回次数的增加,返回合金的N含量随之增加,组织中疏松数量也随之增多。返回次数对K446合金高温断裂特征和高温拉伸性能没有明显影响,但降低持久性能。通过控制冶炼过程并在重熔时补加适量C、Al、Ti等活泼元素,多次返回合金性能仍高于技术条件指标要求。     

水热式RHCM成型工艺对熔接痕性能影响

根据水热式RHCM注射工艺特点,以工程应用广泛的ABS和PP为研究对象,利用Taguchi实验设计方法,研究水热式RHCM注射成型工艺对熔接痕性能影响。实验结果表明:在常规注射工艺和加热工艺中双浇口试样的拉伸强度依然比单浇口试样的拉伸强度低;模具温度的增大使单浇口试样的拉伸强度稍微降低了,使单浇口ABS试样的拉伸强度降低了0.5MPa,使单浇口PP试样的拉伸强度降低了0.27MPa。而水热式RHCM注射工艺,确使模具温度的增大使双浇口试样的拉伸强度有了明显的提升,使单浇口ABS试样的拉伸强度提升了1.57MPa,使单浇口ABS试样的拉伸强度提升了1.56MPa,这对改善熔接痕的性能具有重要的意义。     

Effect of vacuum on porosity and mechanical properties of high-pressure die-cast pure copper

Pure copper tensile bars were produced by conventional die casting(HPDC) and vacuum-assist die casting(VADC) processes. Porosity and mechanical properties were investigated by using optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray computed tomography(XCT) and tensile tester. Results show that porosities including gas porosity and shrinkage porosity could be observed in copper castings. Since the application of vacuum could reduce filling related gas entrapment and facilitate solidification due to the increased heat transfer between metal and die, both number and size of the entrapped gases, as well as shrinkage porosities were significantly reduced in vacuum-assist die castings of pure copper. The porosity fraction decreased from 2.243% to 0.875% compared with that of the conventional die casting. Besides, mechanical properties were improved significantly, i.e., by 15% for ultimate tensile strength and three times for elongation.     

铝/聚合物薄膜复合材料力学性能及其应变速率影响

研究了铝／聚合物薄膜复合材料的力学性能及其变化规律。实验得出铝／聚合物薄膜和组分材料的强度和弹性模量。采用不同的拉伸速率对复合材料加载，分析了加载速率对复合材料性能的影响。     

Microstructure and mechanical properties of ultrafine WC–Ni–VC–TaC–cBN cemented carbides fabricated by spark plasma sintering

Ultrafine WC–Ni–VC–TaC cemented carbides with different amounts of cubic boron nitride (cBN) were fabricated by spark plasma sintering, and the microstructure and mechanical properties of the as-prepared cermets were investigated. Scanning electron microscopy observations showed that the size of WC grains in the cermet samples was 0.2–0.4 μm. After the addition of cBN, the samples were still quite dense with the highest relative density of almost 98% when the addition fraction of cBN was 50 vol.%, although some micropores might exist in the samples. X-ray diffraction results indicated that no phase transformation of cBN was detected. The relative density and hardness of the cemented carbides increased with the addition fraction of cBN, but their strength decreased. When the fraction of cBN increased from 0 up to 50 vol.%, the hardness of the samples increased from 2100 to 3200 HV, but the flexural strength decreased from 1950 to 1250 MPa.     

Properties of alumina-based ceramic cores

Fused corundum is a rather promising raw material for preparing an alumina-based ceramic core due to its excellent high temperature resistance and chemical inertness.In this study,alumina-based ceramic cores were prepared using fused corundum as the matrix material,and the effect of varying silica powder contents on the properties of the alumina-based ceramic cores,including the sintering shrinkage,the flexural strength,and the high temperature deformation was investigated.The mineralization mechanisms of the silica on the alumina-based ceramic core were also analyzed.The optimum addition amount of silica in this experiment is 8% in weight.At that moment,the aluminum-based core has both a low sintering shrinkage coefficient of 0.66% and better properties:the room temperature flexural strength is 22.19 MPa,the high temperature flexural strength is 21.54 MPa,the high temperature deformation is 0.93 mm,and the residual flexural strength is 47.41 MPa.     

Effects of Re-Melting Processes on the Tensile Properties of K452 Alloy at High TemperatureEI北大核心CSCD

K452 alloy is a nickel-based cast superalloy having the good tensile properties at high temperature and excellent corrosion resistance. It has been applied as a blade material of engines when environmental temperature is not above 950 degrees C. It is found that the tensile properties of the alloy have become more scattered and unstable although its chemical compositions are not changed. Hence, the tensile properties of the alloy were studied in order to increase its stability at high temperature and improve its applied properties. Tensile specimens were prepared using the different re-melting processes. Tensile tests were done at 900 degrees C. When the pouring temperature was 1430 degrees C, tensile properties were not only lower than expected, but also had great degree of dispersion, i.e., the vales of ultimate strengths changed in the range of 410 MPa and 510 MPa, and the elongations changed in the range of 3.5% and 22.0%, the average contents of O and N were the highest among three tested conditions. The highest N content was 0.0028%. And the shrinkage area was higher than those in other two re-melting processes. When the pouring temperature was 1500 degrees C, the tensile properties were improved, and their changing scopes became small, the average contents of O and N decreased, the shrinkage area decreased. When the refining temperature was 1590 degrees C and the holding time was 5 min, both average contents of O and N were decreased greatly, the shrinkage was not seen in the fracture surfaces. And the tensile properties were improved. Furthermore, their changing scopes were very small.