Performance of long glass fiber‐reinforced polypropylene composites at different injection temperature

Long glass fiber‐reinforced polypropylene composites were prepared using self‐designed impregnation device. Effects of the different injection temperature on mechanical properties, crystallization, thermal, and dynamic mechanical properties of long glass fiber‐reinforced polypropylene composites were discussed. The differential scanning calorimetry (DSC) results indicate that the melting peak temperature of PP/LGF composites gradually reduced, however, the crystallinity of PP/LGF composites gradually increased with increasing injection temperature. Thermo‐gravimetric analyzer (TGA) results demonstrate that with increasing injection temperature, the temperature of the PP/LGF composites melt increased, the viscosity of the PP/LGF composites melt lowered, the mold filling of the PP/LGF composites melt was easy, the shear force of glass fiber was relatively low, which made the residual length of glass fiber in products increase. Dynamic thermal mechanical analyzer (DMA) results show that the storage modulus of PP/LGF composites is the highest while the injection temperature is at 290°C, and the peak value of tan σ of PP /LGF composites at 290°C is minimal, which indicates that the mechanical properties of PP /LGF composites at 290°C is the best. What' more, the injection temperature at 290°C significantly ameliorated “glass fiber rich skin” of products of glass fiber‐reinforced composites. J. VINYL ADDIT. TECHNOL., 24:233–238, 2018. © 2016 Society of Plastics Engineers     

长玻璃纤维增强PA66复合材料的综合性能及其影响因素研究

利用定制的熔融浸渍装置制备了长玻璃纤维增强聚酰胺66(PA66/LGF)复合材料,并对其力学性能、界面黏结性等进行了表征,探讨了玻璃纤维含量、润滑剂含量、相容剂含量以及切粒长度等因素对复合材料性能的影响,得到了PA66/LGF复合材料优化的配方设计与切粒长度.结果表明,当玻璃纤维含量为43％(质量分数,下同)、切粒长度...     

Rheological characterization of HDPE/sisal fiber composites

The present paper summarizes an experimental study on the molten viscoelastic behavior of HDPE/sisal composites under steady and dynamic mode. Variations of the melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. The shear rate γ at the wall was calculated using Rabinowitsch correction applied to the apparent shear rate values. It was observed that the melt viscosity of the composites increased with the addition of fibers and maleic anhydride-grafted PE (MAPE). Die swell of HDPE also decreased with the addition of sisal fibers and MAPE. Further, the dynamic viscoelastic behavior of the composites was measured employing parallel plate rheometer. Time–temperature superposition was applied to generate various viscoelastic master curves. Temperature sweeps were also carried out to study the flow activation energy determined from Arrhenius equation. The fiber–matrix morphology of the extrudates was also examined using scanning electron microscopy. POLYM. ENG. SCI., 47:1634–1642, 2007. © 2007 Society of Plastics Engineers     

Fracture and Orientation of Long-Glass-Fiber-Reinforced Polypropylene During Injection Molding

Injection processing parameters directly influence the final fiber length and may have a negative effect on the mechanical properties of a part. The aim of the work is to investigate and quantify the effects of the injection rate (2/10/50 cm³/s) on the fiber length, the distribution, and orientation during injection molding and the mechanical properties of long-glass-fiber-reinforced polypropylene (LGF/PP) by experimental and simulated methods. When the injection rate increases from 2 to 10 cm³/s, the fiber length sharply decreases from the original 11 mm to 3.43 mm at the nozzle and 1.30 mm at the filling end, and almost 88% of the fibers are less than 3 mm when the injection rate is 50 cm³/s. A distinct hierarchical orientation (skin-shear-core) for the fiber distribution in the thickness is obtained via a metallographic microscope, which shows that the shear layer (here the shear stress is larger and the fiber is more inclined to oriented along the flow direction) decreases with increasing injection rate. Moreover, the numerical results of the residual fiber length and orientation at different injection rates are in accord with the trend of the measured results. POLYM. ENG. SCI., 60:13–21, 2020. © 2019 Society of Plastics Engineers     

Linear low-density polyethylene/high-density polyethylene blends: Effect of high-density polyethylene content on die swell and flow instability

This work aimed to evaluate the effect of high-density polyethylene (HDPE) content and of shear rate on the die swell and flow instability of linear low-density polyethylene (LLDPE)/HDPE blends. The results showed that the die swell of the LLDPE/HDPE blends increased with the increase in the shear rate. At high shear rates, the increase in the HDPE content led to an increase in the die swell of LLDPE/HDPE blends. The surface morphology analysis of the extrudates by optical and scanning electron microscopy revealed the presence of sharkskin and stick–slip flow instabilities in LLDPE and LLDPE/HDPE blends at the shear rates investigated. These instabilities were attenuated with the addition of HDPE and almost disappeared in the LLDPE/HDPE blend containing 50 wt% of HDPE.     

Viscosity and die swell of acrylonitrile-butadiene-styrene filled with glass beads and glass fibers

Shear viscosity and die swell ratio of acrylonitrile-butadiene-styrene filled with glass beads and glass fibers were measured. The relative viscosity of the composites increased with filler content, but decreased with shear rate. At low shear rates, fiber filled systems had higher relative viscosities than bead filled systems. At high shear rates, the opposite was observed. The die swell ratio of the unfilled material increased linearly with the logarithm of the shear rate. Systems highly filled with glass beads or fibers showed a maximum in the die swell ratio at medium shear rates. The magnitude of the maximum in the die swell ratio increased with the filler content and the die length, up to a certain length, in a series of dies that had the same radius. The presence of a maximum in the die swell ratio of the filled melts is explained by an order-disorder phenomenon observed earlier by Wu.     

长玻璃纤维增强聚丙烯复合材料的力学性能研究

采用熔体浸渍技术制备了长玻璃纤维母料(LGF/PP-g-MAH/PP)增强聚丙烯(PP)复合材料(LGF/PP)。通过双螺杆挤出机制备了同等配比的短玻纤增强聚丙烯(SGF/PP)复合材料。研究了LGF含量、环氧树脂(EP)和固化剂(2E4MZ)对LGF/PP复合材料的力学性能影响。结果表明:当LGF质量分数为35%～40%时,LGF/PP的综合力学性能最好,且明显优于同样组成的SGF/PP复合材料。EP和含固化剂(2E4MZ)的EP对LGF/PP复合材料的力学性能提高有一定的作用。SEM照片分析表明:EP的加入能改善玻纤与聚丙烯基体的界面粘接。     

The influences of fiber feature and polymer melt index on mechanical properties of sugarcane fiber/polymer composites

The fiber characteristics (i.e., the fiber type, morphology, and dimension) and polymer melt flow index (MFI) significantly affected mechanical properties of sugarcane fiber/HDPE composites. The length and diameter of sugarcane fibers followed a lognormal distribution before and after compounding. The long fibers had a significant reduction in the dimension and aspect ratio during compounding. However, the short fibers had close values in these two properties before and after compounding. For the resultant sugarcane fiber/polymer composites, the HDPE resins with a low MFI value presented high tensile and impact strengths. Because of high sugar content, the pure rind fiber had a poor performance as filler in the HDPE resins with respect to the raw bagasse fiber and alkali‐extracted bagasse fiber. On the other hand, the aspect ratio was proportional to the mechanical performance of the fibers in the HDPE resins. As a result, the fibers with a large aspect ratio and low sucrose content improved the strength properties of the resultant composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5607–5619, 2006     

UV老化对ZnO填充PA6/LGF复合材料性能的影响

用熔融共混法制备出长玻璃纤维(LGF)含量为30%的LGF增强尼龙6(PA6)/ZnO(PA6/LGF/ZnO)复合材料,并采用氙灯紫外(UV)老化法研究了ZnO含量为0%~8%及UV老化时间为0~800 h对复合材料力学性能和结晶性能的影响。结果表明,经UV辐照后,PA6/LGF/ZnO复合材料的拉伸强度升高,韧性下降,其中当ZnO添加量为6%时,复合材料在800 h老化后的拉伸强度和缺口冲击强度保留率较未添加ZnO的复合材料分别提高了5.39%和4.98%。SEM分析表明在UV老化过程中,LGF与PA6基体之间的界面并未受到明显破坏,老化主要集中发生在PA6基体上。随着老化时间的延长,PA6/LGF复合材料中的PA6出现UV交联而使其结晶度从26.19%降低至20.70%;对于ZnO含量为6%的PA6/LGF/ZnO复合材料,老化800 h后其结晶度仅从22.92%下降至21.34%,PA6/LGF/ZnO复合材料整体上的结晶性能趋于稳定。     

Preparation and Mechanical Properties of Long Glass Fiber Reinforced PA6 Composites Prepared by a Novel Process

Summary: Long glass fiber reinforced PA6 (LGF/PA6) prepregs were prepared by impregnating PA6 oligomer melt into reinforcing glass fiber followed by subsequent solid‐state polymerization (SSP) to obtain LGF/PA6 composite pellets. A conventional injection‐molding machine suitable for short glass fiber reinforced composites was applied to the processing of the prepared composites, which reduced the fiber length in the final products. Mechanical properties, thermal property, and fiber length distribution of injection molding bars were investigated. Scanning electron microscopy (SEM) was used to observe the impact fracture surfaces and the surfaces of glass fiber after the SSP. It was found that the LGF/PA6 composites were of favorable mechanical properties, especially the impact strength, although the average length of glass fiber was rather short. By this novel process, the content of glass fiber in composite could be high up to 60 wt.‐% and the maximum level of heat distortion temperature (HDT) was close to the melting temperature of PA6. SEM images indicated the favorable interfacial properties between the glass fiber and matrix. The glass fiber surfaces were further observed by SEM after removing the matrix PA6 with a solvent, the results showed that PA6 macromolecules were grafted onto the surface. Furthermore, the grafting amount of PA6 was increased with SSP time.

SEM images of impact fracture surfaces of LGF/PA6 composites (left) and of glass fiber surfaces after removing PA6 with 5 h SSP (right).     

Elastic behavior of LDPE/HEPE blend melts in capillary extrusion

The studies of the elastic behavior in the capillary flow of LDPE/HDPE blend melts were carried out at a test temperature range from 180 to 200°C and at an apparent shear rate of about 25–120 s⁻¹. The end‐pressure drop (ΔP_end) increased nonlinearly with increasing wall shear stress (τ_w) and achieved a minimum value at a weight fraction (ϕ_HD) of HDPE of 50%. The die‐swell ratio (B) increased basically linearly with increasing τ_w or ΔP_end and achieved a maximum value at ϕ_HD of 50%. With the addition of the die length–diameter ratio, the values of B were decreased linearly. At a low shear rate, the temperature sensitivity of the melt die‐swell was more significant than at a high shear rate. With increasing ϕ_HD, B increased when ϕ_HD < 50%, then decreased. B reached a maximum value at ϕ_HD of 50% and a fixed apparent shear rate. This phenomenon may be explained by using the theory of viscoelastic competition between components of polymer blend melts. Furthermore, the first normal stress difference (N₁) of the sample melts was estimated by using an equation published in a previous work. The results showed that B increased linearly with increasing N₁. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 759–765, 2000     

Effect of impregnation time on performance of long glass fiber‐reinforced polypropylene composites

Long glass fiber (LGF)‐reinforced polypropylene (PP) composites were prepared using self‐designed impregnation device. Effects of impregnation time on mechanical properties, crystallization, dynamic mechanical properties, and morphology of PP/LGF composites were investigated. The experiment results demonstrate that the excellent tensile strength, Notched Izod impact strength was 152.9 MPa, 31.2 KJ/m², respectively, and the stiffness of PP/LGF composites was higher, when the impregnation time was 7.03 s. The excellent interfacial adhesion between PP and glass fiber indicates that PP/LGF composites possess the outstanding mechanical properties. The impregnation time scarcely influenced thermal properties of PP/LGF composites. J. VINYL ADDIT. TECHNOL., 24:174–178, 2018. © 2016 Society of Plastics Engineers     

聚合物熔体在任意长径比圆锥口模的挤出胀大唯象研究

深入讨论了聚合物熔体在不同长径比、不同角度圆锥口模的挤出胀大现象及机理。对口模长径比较小的挤出胀大,由于熔体入口拉伸弹性变形来不及松弛,产生较大的挤出胀大;对长径比较大的口模,熔体在平直流道内停留时间较长,入口弹性形变逐渐松弛,这时主要是流动剪切应变引起的弹性变形,产生较弱的挤出胀大,比长径比小的挤出胀大来得小,并且聚合物熔体的挤出胀大随着长径比的增大而趋向一恒定值。结果还表明:聚合物熔体在圆锥口模的挤出胀大受到挤出口模入口角影响。当L/D较小时,挤出胀大与口模入口角有关;当L/D较大时,口模入口角对挤出胀大影响较小。     

PPS/PA66/GF复合材料的制备及性能研究

在聚苯硫醚（PPS）树脂基体中引入聚酰胺66（PA66）,随着PA66含量增加,PPS/PA66共混物的拉伸强度和弯曲强度逐渐下降,结合PPS/PA66共混物的相形貌分析,提出了通过玻璃纤维（GF）的引入,制备具有互锁结构的PPS/PA66/GF三元体系复合材料,达到同时提高复合材料的强度、刚度及韧性的目的。分别考察了短玻璃纤维（SGF）和中长玻璃纤维（LGF）增强PPS/PA66的综合性能。结果表明,GF的引入显著提高了共混物的力学性能,同时,PPS/PA66/SGF和PPS/PA66/LGF复合材料的扫描电子显微镜和动态力学性能分析都表明共混物内部形成了一个高度互锁的结构。     

Effect of filler treatments on rheological behavior of calcium carbonate and talc‐filled polypropylene hybrid composites

Commercial stearic acid treated calcium carbonate (CaCO₃) was used to make a comparative study on rheological behavior of the CaCO₃ and talc‐filled polypropylene (PP) hybrid composites with nontreated filler. Apparent shear viscosity and extrudate swell were investigated with variation of filler ratio and temperature with 30% by weight total of filler was used in PP composite. The Shimadzu capillary rheometer was used to evaluate shear viscosity and shear rate of the composite. It was found that the shear viscosities decrease with increasing shear rate. The apparent shear viscosity of the composite containing the stearic acid treated is slightly lower than untreated filler. Shear thickening behavior at higher shear rate has also shown by 15/15 treated composites at higher temperature about 220°C and investigation by SEM has proved that filler being densely packed at that condition. Treated composites also exhibit lower swelling ratio value than untreated composite, and swelling ratio also decreases linearly with increasing temperature and the die length–diameter ratio. It is believed that dispersion of filler play an important role not only on shear viscosity but also on swelling ratio of PP composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5421–5426, 2006     

长玻纤增强热塑性复合材料阻燃改性及老化性能研究进展

综述了近几年来长玻璃纤维(LGF)增强热塑性复合材料的发展现状,重点以聚丙烯为例,介绍了纤维含量、分布及纤维与基体之间相容性等因素对LGF增强热塑性复合材料性能的影响;重点以尼龙6为例,对LGF增强热塑性复合材料的阻燃改性及老化性能的相关研究进行了阐述。最后对未来LGF增强热塑性复合材料改性及抗老化研究的重点和方向进行了展望。     

Studies on thermal,mechanical, morphological,and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers     

A parallel coextrusion technique for simultaneous measurements of radial die swell and velocity profiles of a polymer melt in a capillary rheometer

This article proposes a new experimental technique to simultaneously measure radial die swell and velocity profiles of polystyrene melt flowing in the capillary die of a constant shear rate rheometer. The proposed technique was based on parallel coextrusion of colored melt‐layers into uncolored melt‐stream from the barrel into and out of the capillary die. The size (thickness) ratio of the generated melt layers flowing in and out of the die was monitored to produce the extrudate swell ratio for any given radial position across the die diameter. The radial velocity profiles of the melt were measured by introducing relatively light and small particles into the melt layers, and the times taken for the particles to travel for a given distance were measured. The proposed experimental technique was found to be both very simple and useful for the simultaneous and accurate measurement of radial die swell and velocity profiles of highly viscous fluids in an extrusion process. The variations in radial die swell profiles were explained in terms of changes in melt velocity, shear rate, and residence time at radial positions across the die. The radial die swell and velocity profiles for PS melt determined experimentally in this work were accurate to 92.2% and 90.8%, respectively. The overall die swell ratio of the melt ranged from 1.25 to 1.38. The overall die swell ratio was found to increase with increasing piston speed (shear rate). The radial extrudate swell profiles could not be reasoned by the shear rate change, but were closely linked with the development of the velocity profiles of the melt in the die. The die swell ratio was high at the center (～1.9) and low (～0.9) near the die wall. The die swell ratio at the center of the die reduced slightly as the piston speed was increased. Polym. Eng. Sci. 44:1960–1969, 2004. © 2004 Society of Plastics Engineers.     

HDPE/OMMT纳米复合材料挤出胀大比的影响因素研究

利用流变分析仪研究了高密度聚乙烯(HDPE)/有机蒙脱土(OMMT)纳米复合材料在挤出过程中的挤出胀大行为及其影响因素,深入讨论了剪切应力、剪切速率、口模温度、口模长径比及OMMT用量对HDPE/OMMT纳米复合材料挤出胀大比B的影响.结果表明,B值随着剪切应力或剪切速率的增加而增大,并且与剪切应力近似呈线性关系;随着口模温度的升高或长径比的增加而减小,当口模长径比较小时,B值受剪切应力或剪切速率的影响尤为显著;同时B值随OMMT用量的增加而逐渐减小.     

Thermal stability and thermal degradation kinetics of short and long glass fiber reinforced PA10T composites

In this work, the long glass fiber reinforced poly(decamethylene terephthalanide) (PA10T/LGF) composites and short glass fiber reinforced PA10T (PA10T/SGF) composites were prepared by two different extrusion processing methods, respectively. The results of mechanical properties reveal the introduction of glass fiber can improve the performance of the material, and the LGF reinforced PA10T composites can achieve much higher performance than the SGF reinforced ones at the same level of fiber contents. The thermal stabilities of neat PA10T, PA10T/SGF, and PA10T/LGF are investigated by nonisothermal TG analysis. The thermal degradation kinetics is introduced by using Kissinger and Flynn‐Wall‐Ozawa methods and the thermal degradation mechanism functions of the samples are calculated by the Coats‐Redfem model. The results show that the thermal stabilities of PA10T/SGF and neat PA10T are better than that of PA10T/LGF. In addition, the incorporation of glass fiber into PA10T do not have much effect on the reaction mechanism type of thermal degradation compared with that neat PA10T. Furthermore, the thermal stability analysis of the composites is verified by the computed results of Gibbs free energy (ΔG^#). POLYM. ENG. SCI., 59:246–253, 2019. © 2018 Society of Plastics Engineers