Durability of in-plant recycled glass fiber reinforced polyamide 66

A study of the effect of in-plant recycling on the durability of glass fiber reinforced polyamide 66 is reported. Injection-molded test bars were exposed to thermal agin, coolant aging, and creep testing. It was shown that thermal aging and coolant aging induced similar effects. The onset of embrittlement was revealed by both a reduction in elongation at break and loss of impact resistance. Samples based on 100% in-plant regrind exhibited a more intense embrittlement compared to virgin samples during both thermal and coolant aging. For samples based on 25% recycled material, the deterioration rate was similar to that of virgin samples during thermal aging but slightly faster during coolant aging. Creep experiments indicated that inplant recycled materials can display reduced dimensional stability, which may be explained by a reduced degree of reinforcement due to fiber breakage during the recycling operation. Knock-down (KD) factors were defined and determined for the in-plant recycled samples. For creep resistance, tensile strength and modulus, the KD factors were strongly affected by fiber length. The highest KD factor, as determined for samples based on 25% and 100% recycled material, was 8% and 16% respectively.     

Recyclability of a glass fiber poly(butylene terephthalate) composite

The recyclability of a fiber-reinforced poly(butylene terephthalate) (PET) composite has been studied. After treatment with a suitable silane, processed regrind composites are successfully recycled, with mechanical properties as good as a comparable, commercial composite. The three processing techniques investigated are injection molding, extrusion compression molding and compression molding. As expected, processing technique and processing parameters are important in determining the mechanical properties of the molded regrind. Our results show that injection- and extrusion-compression-molded regrind composites have good fiber bundle dispersion and fiber alignment, resulting in tensile properties better than the compression-molded samples. On the other hand, compression-molded samples, which show random fiber orientation and low fiber bundle dispersion, have lower tensile properties, but better impact strength than injection- and extrusioncompression-molded composites.     

Recyclability of a continuous e-glass fiber reinforced polycarbonate composite

Fiber reinforced plastics are multi-component materials for which physical properties are strongly dependent on fiber and resin structure. Despite the disruptive nature of recycling methods on such structures, these materials nevertheless can be recycled. In this report, the recyclability of a fiber-reinforced cyclic BPA polycarbonate has been studied. It is found that ground up composite is recyclable and possesses properties as good as or better than a comparable commercial composite. The processing techniques investigated herein are injection, extrusion compression, and compression molding. As expected, processing technique and parameters are important in determining the mechanical properties of the molded regrind. Our results show that injection and extrusion compression molding yield recycled composites with good tensile properties, though the impact strengths are relatively low. This is due to high fiber orientation and fiber bundle dispersion. On the other hand, compression molded samples, which show random fiber orientation and low fiber bundles dispersion have relatively low tensile properties, but excellent impact strength. Results are discussed in terms of microstructural details, which include resin molecular weight and fiber length and orientation.     

Durability study of recycled glass-fiber-reinforced polyamide 66 in a service-related environment

A study of the mechanical properties in an accelerated service-related environment of recycled glass-fiber-reinforced polyamide 66 is reported. Material reinforced with 30 wt % of short fibers was reground and remolded up to seven times. Thermal aging in air at 140°C for up to 3000 h and coolant aging at 110°C for up to 1000 h showed no significant differences in behavior pattern. In addition to mechanical testing, the fiber length measured directly and the matrix stability measured by differential scanning calorimetry (DSC) were used to determine the influence of process-induced degradation on the durability of recycled samples compared with that of virgin samples. The results indicate that fiber length controls the initial properties. The differences in tensile strength and modulus between recycled and virgin samples were similar within the examined times of aging and could be explained by process-induced fiber shortening. The onset of embrittlement during both aging conditions is revealed first in a decrease in tensile elongation at break. Because of a lower degree of fiber reinforcement, the elongation at break of recycled samples was always as good as that of virgin reference samples. However, increasing the number of molding operations up to four to five times resulted in a faster deterioration rate in elongation at break of recycled samples. Further processing had less effect on the deterioration rate. The oxidative stability of the matrix as determined by DSC decreased as a result of repeated processing. The results suggest that matrix stability is related to changes occurring in elongation at break during accelerated aging of samples remolded up to about four times. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1631–1641, 1997     

Reprocessing of fiberglass reinforced polyamide 66: Influence on short term properties

The fiber length distribution was found to control the overall short term performance of reprocessed heat-stabilized short fiberglass reinforced polyamide 66. Length changes, and matrix and interface degradation were studied. Fiber shortening dominates during compounding and during the first injection molding cycle. Further regrinding and remolding has a lesser effect. The short term mechanical strength decreased for reprocessed samples. Using a modified Kelly-Tyson model, the lower tensile strength of reprocessed samples, compared with virgin samples, can be explained by fiber shortening. Reprocessing had a negligible effect on the strength for both the fiber matrix interface and the matrix of this system. Studies on unreinforced samples confirmed that thermal degradation of the matrix during reprocessing had a negligible effect on short term mechanical performance.     

Influence of impurities on mechanical properties of recycled glass fiber reinforced polyamide 66

This work investigates the influences of impurities on the durability and the reliability of the mechanical properties of recycled glass fiber reinforced polyamide 66. A critical size-concentration zone could be determined based on changes in tensile properties of samples containing untreated glass beads of different size and concentrations, which were used as simulated impurities in in-plant reprocessed material. Characterization of samples based on recyclate from post-use radiator end-caps, which contained residues of EPDM rubber, showed that the tensile strength was almost unaffected by rubber particles up to an equivalent diameter, d, of ～700 μm. However, a significant strength reduction commenced for rubber particles larger than 1200–1300 μm, and the strength showed a correlation with d^?1/2. Furthermore, large simulated impurities (425–590 μm) in in-plant material and rubber residues in post-use recyclate showed a negative effect on the mechanical reliability.     

Study of the effect of regrinding on the cumulative damage to the mechanical properties of fiber-reinforced nylon 66

An experimental study of the tensile strength of nylon 66 regrind, with and without short-fiber reinforcement, is reported. For nylon 66 without reinforcement, a uniform increase in tensile strength has been observed with increasing number of moldings. This is due to a further condensation reaction which occurs during molding. For short fiber-reinforced nylon 66 composite, the tensile strength decreases with increasing number of moldings, which is attributed to the cumulative breakage of fiber length through mechanical working. A model based on fiber length analysis is proposed, and the semiempirical equation can be used to predict experimental results and balance cost–end use properties.     

Evaluating recyclability of fly ash reinforced polyvinyl chloride foams

Using fly ash as a reinforcing filler can be very cost effective; however, the recycling of postconsumer products containing fly ash is of a considerable concern. In this study, the recycling of processed polyvinyl chloride (PVC) foam reinforced with fly ash was investigated by evaluating the effect of regrind content (up to 40 wt%) and fly ash content (up to 20 wt%) on the physical, mechanical, microstructural, and processing properties of the composites. Experimental results show an increase in the foam density with increasing regrind and fly ash contents. The melt viscosity increased with increasing the regrind concentration; however, it dropped with increasing the fly ash content. The tensile strength increased with increasing the regrind content, indicating a good degree of gelation in the composites. Meanwhile, the charpy impact strength of the composites decreased due to the high rigidity of fly ash particles. Dynamic mechanical analysis show that the storage modulus improved with both the addition and increasing the amount of regrind, which confirmed good stress transformation between the polymer foam matrix and the fly ash particles. The polymer matrix morphology, as was determined by scanning electron microscopy (SEM), confirmed uniform foam structure even with the addition of 40 wt% regrind in the virgin PVC. J. VINYL ADDIT. TECHNOL., 24:154–161, 2018. © 2016 Society of Plastics Engineers     

Reprocessing of thermoplastics. II. Polycarbonate

The effect of recycling on the properties of injection molded polycarbonate was investigated. One unreinforced and two glass-reinforced grades were studied. Fiber degradation was distinguished from molecular scission by spiral flow measurements and molecular weight analysis. During the first cycles the average fiber length was significantly reduced, but at later stages it approached an equilibrium. The number of scission per original polymer molecule increased linearly with the number of recycles for all systems studied, but the degradation reaction did not follow random scission kinetics. The glass reinforced grades exhibited degradation rates which were at least twice as high as that of an unreinforced polymer. This discrepancy was most probably the result of a more extensive viscous heating in the glass-reinforced systems. The decrease in molecular weight as well as in fiber length greatly affected the impact strength of the material. The effect of processing temperature on polymer degradation during recycling was evaluated. The fraction of virgin material that has to be added to the regrind to maintain a certain property level was determined. On a 90 percent property level, an icrease in melt temperature by 1°C corresponded to an increase of 1 percent in the required amount of virgin material. Aging tests indicated that there was no significant difference in degradation rate between recycled and virgin material, although the former certainly exhibited lower absolute values of the measured property (impact strength).     

One step forward to a sustainable green solution for extruded foam PVC building products

This paper is dedicated to the development of a robust and cost‐effective formulation to maximize the use of recycled poly(vinyl chloride) (PVC) back into its virgin compounds. This study concludes that a balanced stabilizer and lubricant formulation will overcome the detrimental effects of repeated heat history on the recycled/regrind PVC. The developed formulation using up to 70% of recycled/regrind PVC has been successfully implemented in the extrusion process for manufacturing high‐quality foam PVC profiles for the building industry. As a result, this study takes a huge step forward toward a green and sustainable solution for PVC applications. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

基于NSGA-Ⅱ与熵权TOPSIS法的混杂纤维再生混凝土配合比多目标优化

制备以钢纤维(SF)、塑钢纤维(MPPF)为骨料的高性能道面混杂纤维再生混凝土(HFRAC),研究改善再生混凝土(RAC)强度及耐磨性能,采用响应面法(RSM)中Box-Behnken试验设计方法,以SF体积掺量、MPPF体积掺量和砂率为因素,以HFRAC抗折强度、抗压强度和磨损量为评价指标,建立各评价指标的预测模型,分析各因素对评价指标的影响,并构建基于NSGA-Ⅱ耦合熵权TOPSIS法的HFRAC配合比优选模型,确定综合性能最优时的配合比方案。结果表明:在试验范围内各评价指标的响应面模型拟合效果良好,预测精度高;各评价指标不仅受单因素影响,而且受因素间交互作用影响,SF体积掺量与MPPF体积掺量交互作用对抗折强度、抗压强度影响极显著,对磨损量影响显著,MPPF体积掺量与砂率交互作用对抗折强度影响显著;当SF体积掺量为1.39%、MPPF体积掺量为0.97%、砂率为36.10%时,HFRAC综合性能最优。该方法能够实现HFRAC性能的综合改善,可为HFRAC在道路工程中的推广应用提供一定理论依据和技术支撑。     

Effect of alumina fiber content on pore structure and properties of porous ceramics

Porous Al₂O₃ ceramics with different contents of alumina fibers were prepared by gel-casting process. The effects of Al₂O₃ fiber content on pore size distribution, porosity, compressive strength, and load-displacement behavior of the ceramic materials were investigated. Initial results showed that with the increase of Al₂O₃ fiber content, the pore size and porosity of the material is increased, and the compressive strength is decreased. However, upon increasing the fiber content from 50 wt% to 67 wt%, the performance of the samples changed greatly. The compressive strength of the material increased, while the porosity remained unchanged, the pore size increased greatly, and the shape of the load displacement curve changed. It showed that when the fiber content increased from 50 wt% to 67 wt%, the loading body in the fiber-reinforced porous ceramics changed from particles to fibers.     

黄麻纤维增强聚丙烯的力学性能

本文讨论了注塑成型黄麻纤维增强聚丙烯的制备方法和力学性能.将纤维重量含量分别为10%、20%和30%的复合材料进行比较,分析纤维含量对复合材料拉伸、弯曲和冲击性能的影响;将纤维分别切成约3mm、5mm和10mm长制成复合材料进行比较,分析纤维长度对复合材料拉伸、弯曲和冲击性能的影响.掺入黄麻纤维能使聚丙烯的拉伸和弯曲性能提高,但使其冲击强度降低;随纤维含量的增加或纤维长度的增加,复合材料的强度和模量是递增的,而冲击强度是递减的.     

Visualization analysis of reciprocating‐screw plastication process of glass fiber‐reinforced resins in a glass‐inserted heating cylinder

One challenge in injection molding of long fiber‐reinforced resins is minimizing the fiber breakage during resin plastication and resin flow into a mold. Such fiber breakage reduces the strength of the molded product. Reciprocating plastication is subjected to periodic positional fluctuations of the screw and cylinder in the molding cycle. In this study, visualization experiments were conducted on the reciprocating plastication of long glass fiber (GF)‐reinforced polypropylene with 50 wt% GF. It was found that: (1) temporary voids form in the resin during the metering process, and the pellets rotate from an orthogonal to parallel orientation in the flight direction; (2) length of the weight‐averaged fiber temporarily decreased in the middle stage of the injection process; (3) length of the weight‐averaged fiber was most strongly influenced by the waiting time; and (4) for constant waiting time, the fiber breakage could be minimized by lowering the rotation speed, lowering the back pressure, and shortening the charge stroke. POLYM. ENG. SCI., 59:846–853, 2019. © 2018 Society of Plastics Engineers     

基于正交试验的透水再生混凝土性能优化试验研究

透水混凝土在缓解城市内涝、噪音效应和热岛效应等方面具有广泛的应用前景,但多孔导致的强度偏低限制了其进一步推广应用。本文采用再生粗骨料和聚丙烯纤维配制高性能透水再生混凝土,设计五因素四水平正交试验,采用极差法分析水胶比、目标孔隙率、再生粗骨料取代率、粉煤灰掺量和聚丙烯纤维掺量对透水再生混凝土抗压强度、有效孔隙率、透水系数的影响规律。结果表明：透水再生混凝土抗压强度影响因素的主次顺序为目标孔隙率>再生粗骨料取代率>水胶比>聚丙烯纤维掺量>粉煤灰掺量;透水再生混凝土抗压强度最大为48.26 MPa,此时透水系数为1.96 mm/s;随着目标孔隙率的提高抗压强度呈线性下降的趋势;40%再生粗骨料等质量取代天然粗骨料后,透水再生混凝土的抗压强度达到28.7 MPa,提高119.08%,透水系数增加9.44%;掺入0.11%体积掺量的聚丙烯纤维后透水再生混凝土的抗压强度达到27.4 MPa,提高幅度为10.48%,而且透水性能不会降低。研究结果可以为高性能透水再生混凝土的制备提供依据。     

Effect of Coupling Agent Concentration,Fiber Content,and Size on Mechanical Properties of Wood/HDPE Composites

In this study, the influence of coupling agent concentration (0 and 3 wt%), wood fiber content (50, 60, 70, and 80 wt%), and size (40–60, 80–100, and 160–180 mesh) on the mechanical properties of wood/high-density-polyethylene (HDPE) composites (WPCs) was investigated. WPC samples were prepared with poplar wood-flour, HDPE, and polyethylene maleic anhydride copolymer (MAPE) as coupling agent. It was found that the tensile properties and the flexural properties of the composites were improved by the addition of 3 wt% MAPE, and the improved interfacial adhesion was well confirmed by SEM micrographs. It was also observed that the best mechanical properties of wood/HDPE composites can be reached with larger particle size in the range studied, while too-small particle size was adverse for the mechanical properties of wood/HDPE composites. Moreover, the tensile modulus, tensile strength, and flexural strength of WPCs decreased with the increase in fiber content from 50 to 80 wt%; the flexural modulus of WPCs increased with the increase in fiber content from 50 to 70 wt% and then decreased as the fiber content reached 80 wt%. The variances in property performance are helpful for the end-user to choose an appropriate coupling agent (MAPE) concentration, wood fiber content, and particle size based on performance needs and cost considerations.     

An investigation on the rheology,morphology, thermal and mechanical properties of recycled poly (ethylene terephthalate) reinforced with modified short glass fibers

This work was done with the aim to solve an important environmental issue regarding poly (ethylene terephthalate), (PET) wastes. Samples of recycled PET (r-PET) were reinforced with 10 to 30 wt% modified short glass fibers (SGF) through a melt mixing process in an internal mixer and their performance were assessed and compared with those of commercial glass reinforced PET through investigation of their rheology, morphology, thermal, and mechanical properties. It was found that the mechanical properties of the glass reinforced r-PET composites in most cases were comparable or even higher than those of the commercial grades. The impact strength of the 30 wt% SGF filled r-PET composite was about 30% higher than the commercial grades. This led to a conclusion that the PET wastes can be successfully converted to easily moldable thermoplastic materials by incorporation of 30 wt% SGF having a good balance of properties. Through investigation of rheological and morphological properties the optimum conditions for the best reinforcement performance were determined. The r-PET with 30 wt% glass fiber content showed the highest level of orientation and improved interaction with the r-PET matrix while having an acceptable flow behavior and processability. In spite of significant fiber breakage during the melt mixing process, leading to about 20 times reduction in the fiber aspect ratio, the composites maintained their good mechanical properties and showed a shear thinning behavior at high shear rates. The incorporated glass fibers acted as nucleating agents and improved the crystallization rate of r-PET leading to an overall increase in the crystallinity. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

热定形对并列复合再生聚酯短纤维性能的影响

以再生聚酯瓶片料和泡料混合料为原料进行并列复合纺丝,并经后纺工艺处理得到并列复合再生聚酯短纤维。通过对纤维进行干热定形,研究热定形温度、时间对并列复合再生聚酯短纤的强伸性能、卷曲性能和热收缩性能的影响。结果表明:聚酯短纤维的断裂强度和断裂伸长率随着热定形温度升高而增大;断裂强度随热定形时间的延长逐渐下降,断裂伸长率先增大后减小,在20 min时达到最大值,为17.4%,声速取向因子则随着热定形时间的延长呈现下降趋势。纤维的卷曲性能随着热定形温度的升高而改善,较短的时间内,纤维的卷曲性能已经达到最佳;热定形温度的升高使纤维的热收缩率增大;并列复合再生聚酯短纤维的最佳热定形温度是140～160℃,最佳定形时间为10 min。     

Physical,mechanical, and water absorption behavior of coir/glass fiber reinforced epoxy based hybrid composites

Fiber reinforced polymer composites has been used in a variety of application because of their many advantages such as relatively low cost of production, easy to fabricate, and superior strength compare to neat polymer resins. Reinforcement in polymer is either synthetic or natural. Synthetic fiber such as glass, carbon, etc. has high specific strength but their fields of application are limited due to higher cost of production. Recently there is an increase interest in natural composites which are made by reinforcement of natural fiber. In this connection, an investigation has been carried out to make better utilization of coconut coir fiber for making value added products. The objective of the present research work is to study the physical, mechanical, and water absorption behavior of coir/glass fiber reinforced epoxy based hybrid composites. The effect of fiber loading and length on mechanical properties like tensile strength, flexural strength, and hardness of composites is studied. The experimental results reveal that the maximum strength properties is observed for the composite with 10 wt% fiber loading at 15 mm length. The maximum flexural strength of 63 MPa is observed for composites with 10 wt% fiber loading at 15 mm fiber length. Similarly, the maximum hardness value of 21.3 Hv is obtained for composites with 10 wt% fiber loading at 20 mm fiber length. Also, the surface morphology of fractured surfaces after tensile testing is examined using scanning electron microscope (SEM). POLYM. COMPOS., 35:925–930, 2014. © 2013 Society of Plastics Engineers     

结合均匀化理论对钢纤维混凝土梁的疲劳性能分析

钢纤维混凝土(SFRC)在工程中应用日益广泛,为了探究其疲劳破坏现象内在机理,本文结合Mori-Tanaka均匀化理论预测了不同体积掺量下钢纤维混凝土的弹性模量,并以此为基础建立钢纤维混凝土梁四点弯曲有限元模型,采用Miner疲劳损伤准则,分别进行了静力抗弯试验和疲劳试验的数值模拟。模拟结果与相关试验结果拟合较好,验证了模型的可靠性。利用疲劳分析软件,预测了钢纤维混凝土梁的疲劳寿命和疲劳强度,分析了纤维掺量、尺寸效应和纤维长度对疲劳寿命的影响。结果表明:钢纤维可以大幅提高混凝土梁的疲劳寿命,应力水平越低、纤维掺量越大,增幅越大;尺寸效应对疲劳强度和疲劳寿命有一定影响,但随着构件尺寸增加对疲劳性能影响减小;纤维长度越长,梁的抗疲劳性能越好。