Elaboration and relationships between structure and rheological properties of microtalc or nanotalc/polyamide composites

This study focuses on the elaboration of nanocomposites processed by melt mixing of a polyamide 12 matrix and a hydrogel filled with synthetic talc particles. The systems are obtained by simultaneous mixing using either an internal mixer or a lab twin‐screw extruder. The structure and rheological properties of synthetic talc/polyamide composites are compared with those of natural talc/polyamide microcomposites and modified montmorillonite/polyamide nanocomposites. A multiscale structure, composed of numerous nanometric particles but also few micrometric aggregates, is obtained for synthetic talc/polyamide composites. In terms of processability, the lab twin‐screw extruder is more adequate than the internal mixer for the elaboration of synthetic talc/polyamide composites with relatively high filler volume fractions. For composites elaborated with the extruder, the percolation threshold, estimated from linear viscoelastic measurements, is close to 1, 6, and 11%, respectively, with modified montmorillonite, synthetic talc, and natural talc particles, in agreement with structural results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42299.     

The Effect of Carbon Fiber Content on the Mechanical and Tribological Properties of Carbon Fiber-Reinforced PTFE Composites

Blending polytetrafluorothylene (PTFE) to carbon fiber at different compositions was produced in a corotating twin screw extruder where PTFE acts as the polymer matrix and carbon fiber as the dispersed phase. The effects of carbon fiber content on mechanical and tribological properties of the composites were investigated. The worn surface morphologies of neat PTFE and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. The presence of carbon fiber dispersed in the PTFE continuous phase exhibited superior tribological characteristics to unfilled PTFE. The optimum wear reduction was obtained when the content of carbon fiber is 30 vol%.     

Evaluation of mechanical properties of polypropylene/polycarbonate/SEBS ternary polymer blends using Taguchi experimental analysis

In this work, ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS‐g‐MAH) at fixed compositions are prepared using twin‐screw extruder at different levels of die temperature (235‐245‐255°C), screw speed (70‐100‐130 rpm), and blending sequence (M1‐M2‐M3). In M₁ procedure, all of the components are dry blended and extruded simultaneously using Brabender twin‐screw extruder, whereas in M₂ procedure, PC, SEBS, and SEBS‐g‐MAH minor phases are first preblended in twin‐screw extruder and after granulating are added to PP continuous phase in twin‐screw extruder. Consequently, in M₃ procedure, PP and SEBS‐g‐MAH are first preblended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taguchi experimental design. The responding variables are impact strength and tensile properties (Young's modulus and yield stress), which are influenced by the morphology of ternary blend, and the results are used to perform the analysis of mean effect as well. It is shown that the resulted morphology, tensile properties, and impact strength are influenced by extrusion variables. Additionally, the optimum processing conditions of ternary PP/PC/SEBS blends were achieved via Taguchi analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Friction and wear properties of PTFE composites filled with PA6

Blending Polytetrafluoroethylene (PTFE) to PA6 at different compositions was produced in a corotating twin‐screw extruder, where PTFE acts as the polymer matrix and PA6 as the dispersed phase. The effects of PA6 content on the tribological properties of the composites were investigated. The worn surface morphologies of neat PTFE and its composites were examined by scanning electron microscopy (SEM), and the wear mechanisms were discussed. The presence of PA6 particles dispersed in the PTFE continuous phase exhibited superior tribological characteristics to unfilled PTFE. The optimum wear reduction was obtained when the content of PA6 is 30 vol%. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

混炼设备结构对PP/GF复合材料中GF残存长度及其力学性能的影响

基于熔融共混法,分别采用双转子连续混炼挤出机和同向啮合双螺杆挤出机制备了20 %玻璃纤维增强聚丙烯（GFRPP）复合材料,并对制备出的GFRPP复合材料中玻璃纤维残存长度及其力学性能进行了相应表征,在此基础上探讨了具有不同混炼特性的混炼设备结构对GFRPP复合材料中玻璃纤维残存长度及其力学性能的影响。结果表明,GFRPP复合材料的力学性能随玻璃纤维残存长度的增加而明显提高;双转子连续混炼挤出机相对于同向啮合双螺杆挤出机更有利于保留长玻璃纤维,同时适当减弱双转子连续混炼挤出机的转子的分散混合能力,降低转子转速,有利于提高玻璃纤维的残存长度,制备出更高性能的GFRPP复合材料。     

共混方式对高密度聚乙烯/聚碳酸酯共混体系形态与性能的影响

研究了不同共混方式对高密度聚乙烯（ＨＤＰＥ）／聚碳酸酯（ＰＣ）共混体系形态与性能的影响。将不同组成的ＨＤＰＥ／ＰＣ分别在双螺杆、单螺杆挤出机中共混后注射成型,测试注射样条的力学性能并用扫描电子显微镜（ＳＥＭ）对样条断面进行形态观察。结果发现,共混方式对共混体系拉伸强度影响不大,但对冲击强度和断面形态影响较大。当ＰＣ含量低时,双螺杆的共混效果不如单螺杆;当ＰＣ含量较高时,双螺杆的共混效果优于单螺杆。     

Effects of filler geometry on internal structure and physical properties of polycarbonate composites prepared with various carbon fillers

BACKGROUND: The effects of filler geometry are important for understanding the internal structure and physical properties of polymer composites. To investigate the effects of filler geometry on electrical conductivity as well as morphological and rheological properties, three types of polycarbonate (PC) composites were prepared by melt compounding with a twin‐screw extruder. RESULTS: The electrical conductivity of PC/carbon black (CB) and PC/graphite (carbon) nanofibre (CNF) composites did not show a percolation threshold through the entire filler loading ranges. However, PC‐blend‐carbon nanotube (CNT) composites showed a percolation electrical threshold for a filler loading of 1.0 to 3.0 wt% and their maximum electrical conductivity approached 10^?3 S m^?1. PC‐blend‐CB and PC‐blend‐CNF composites showed Newtonian behaviour like pure PC matrix, but PC‐blend‐CNT composites showed yield stress as well as increased storage modulus and strong shear thinning behaviour at low angular frequency and shear rate due to strong interactions generated between CNT–CNT particles as well as PC molecules and CNT particles on the nanometre scale. CONCLUSIONS: The electrical conductivity of the PC composites with different carbon constituents was well explained by the continuous network structure formed between filler particles. The network structure was confirmed by the good dispersion of fillers as well as by the yield stress and solid‐like behaviour observed in steady and dynamic shear flows. Copyright © 2009 Society of Chemical Industry     

Noticeable viscosity reduction of polycarbonate melts caused jointly by nano‐silica filling and TLCP fibrillation

Nano‐SiO₂ was introduced into in‐situ composites of polycarbonate (PC) and a thermotropic liquid crystalline polymer (TLCP) using a twin‐screw extruder. The rheology of these composites was characterized with capillary rheometry, and the morphology of the dispersed TLCP observed with scanning electron microscopy. The rheological data revealed that the viscosity decrease of PC melts by only the addition up to 20 wt% TLCP remained smaller than 30%, while it became ～48% upon further addition of only about 1 wt% nano‐SiO₂ and larger than 60% upon ～9 wt% nano‐SiO₂ filling, in contrast to a 50% viscosity increase of PC melts with increase in nanosilica loading up to ～9 wt%. These silica‐filled composites exhibited markedly low viscosity, especially at relatively high shear rates. The morphology of TLCP extracted from unfilled and silica‐filled composites indicated that the largest viscosity reduction was correlated well with the fibrillation of TLCP droplets enhanced by nano‐SiO₂. The TLCP/SiO₂/PC composites exhibited rheological hybrid effect with fillers at nanometer scale. POLYM. ENG. SCI., 47:757–764, 2007. © 2007 Society of Plastics Engineers     

HDPE/PC分散相纤维化及其原位复合材料的研究

将高密度聚乙烯(HDPE)和聚碳酸酯(PC)在双螺杆挤出机中熔融共混挤出，通过改变对挤出物施加的牵引速度，研究了拉伸力场对HDPE／PC共混物的形态及其原位复合材料性能的影响。结果表明，随着牵引速度的提高，纤维状分散相所占比例增加，但纤维直径无明显变化；HDPE／PC原位复合材料与其普通共混材料相比，拉伸强度基本无变化，但冲击强度提高较大。     

自洁型非对称同向双螺杆挤出机混合分析

设计了自洁型非对称同向双螺杆,并采用实验研究及数值模拟方法分析其混合特性。采用活性纳米CaCO3（nano CaCO3）填充线形低密度聚乙烯(PE LLD)的体系进行实验研究,在挤出量一定的前提下分别在自洁型非对称同向双螺杆挤出机以及普通同向双螺杆挤出机上造粒,通过扫描电子显微镜观察产品中nano CaCO3分布情况。结果表明,非对称双螺杆挤出PE LLD/nano CaCO3复合材料中nano CaCO3分布较为均匀,粒径尺寸更小,具有明显的增韧效果,这与数值模拟结果一致。     

Flame retardancy and mechanical properties of pet‐based composites containing phosphorus and boron‐based additives

Flame retardancy of poly(ethylene terephthalate), PET, was improved using different flame retardant additives such as triphenylphosphate, triphenylphosphine oxide, zinc borate, and boron phosphate (BP). Composites were prepared using a twin screw extruder and subsequently injection molded for characterization purposes. The flame retardancy of the composites was determined by the limiting oxygen index (LOI) test. Smoke emission during fire was also evaluated in terms of percent light transmittance. Thermal stability and tensile properties of PET‐based composites were compared with PET through TGA and tensile test, respectively. The LOI of the flame retardant composites increased from 21% of neat PET, up to 36% with the addition of 5% BP and 5% triphenyl phosphate to the matrix. Regarding the smoke density analysis, BP was determined as an effective smoke suppressant for PET. Enhanced tensile properties were obtained for the flame retardant PET‐based composites with respect to PET. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42016.     

Monitoring the Evolution of Morphology of Polymer Blends Upon Manufacturing of Microfibrillar Reinforced Composites

Abstract

Microfibrillar reinforced composites (MFC) based on HDPE/PET blends were prepared under conditions relevant for direct scale-up to an industrial process. The evolution of the morphology and of the linear viscoelastic response of the blend along the axis of a co-rotating twin screw extruder and at several locations along the extrusion line was monitored. Major changes in the average particle size and size distribution of the disperse phase occurred upon melting of the components, whilst a much slower evolution rate was evident downstream in the extruder. Simultaneously, G′ and G″ increased along the extruder. Pellets showing well oriented PET fibrils embedded in a HDPE matrix with poor adhesion between both were obtained. This MFC showed the typical improvement expected in mechanical performance when compared with the matrix.     

Effects of viscosity ratio and compatibilizers on the morphology and mechanical properties of polycarbonate/acrylonitrile-butadiene-styrene blends

A comprehensive experimental study was carried out to investigate the effects of (1) viscosity ratio, (2) temperature on the viscosity ratio, (3) extruder screw location, and (4) compatibilizers on the morphology of bisphenol-A-polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS). Blends were prepared by utilizing a co-rotating twin screw extruder and in-situ morphology obtained via the screw pullout technique. A plot of the PC/ABS viscosity ratio, η_PC/η_ABS, versus the shear rate showed a gradual rise in the curve up to a critical shear rate and thereafter displayed asymptotic character. Contrary to premise, η_PC/η_ABS decreased with increasing temperature. This was elucidated by the melt viscosity of PC being thermally more sensitive than ABS over the temperature range investigated. As expected, the plot of the average domain size versus the viscosity ratio gave a concave up curve with a minimum when the viscosity ratio was close to unity. The morphology evolution along the screw of a twin screw extruder was examined. When sections of the kneading block were examined, the minor phase domains gradually showed reduction in size toward the extruder die, and the samllest domain was realized at the end of the block, namely, the flow impeding left-handed screw element. Polymethylmethacrylate (PMMA) exhibited the greatest ABS domain size reduction, and annealed samples showed that it suppressed coalescence.     

Effect of Interfacial Compatibility on the Mechanical and Tribological Properties of Blending PTFE with PA6

Blending Polytetrafluorothylene (PTFE) to PA6 with and without maleic anhydride grafted Polytetrafluorothylene (PTFE-g-MA) was produced in a corotating twin screw extruder. The effect of PTFE-g-MA on the tensile properties and tribological properties of PTFE/PA6 polymer blends is studied. Results show that the presence of PTFE-g-PA6 in the PTFE continuous phase improves the interfacial adhesion, as a result of the creation of an interphase that was formed by the interaction between the formed PTFE-g-PA6 copolymer in situ and both phases. Compared with the PTFE/PA6 without PTFE-g-MA, the PTFE/PA6 with PTFE-g-MA had the lowest friction coefficient and specific wear rate under given applied load and reciprocating sliding frequency.     

Characterization,morphology, and biodegradation of bioplastic fertilizer (BpF) composites made of poly(Butylene succinate) blended with oil palm biomass and fertilizer

Poly(butylene succinate) (PBS) is a versatile biodegradable polymer that can be processed into slow‐release bioplastic fertilizer (BpF) composites using twin screw extruder extrusion method, with controlled formulation and temperature. In this study, slow‐release BpF composites were created by blending NPK fertilizer with biodegradable plastic composites and oil palm biomass. Temperature processing was done at 125°C–145°C for 3–5 min using twin screw extruder. Its thermal degradation occurred initially at 263.44°C and reached maximum at 300.73°C. In biodegradation test, the weight losses of PBS/NPKC1 and PBS/NPKC2 were about 60% while the weight losses of PBS/EFB/NPKC1 and PBS/EFB/NPKC2 were 72.68% and 73.09%, respectively. It was observed under scanning electron microscope that PB1 and PB2 showed more homogeneous adhesion and better wetting of PBS. POLYM. COMPOS., 38:2577–2583, 2017. © 2015 Society of Plastics Engineers     

Mechanical and tribological properties of polyoxymethylene modified with nanoparticles and solid lubricants

Polyoxymethylene (POM) composites modified with nanoparticles, polytetrafluoroethylene (PTFE) and MoS₂ were prepared by a twin‐screw extruder. The effect of nanoparticles and solid lubricant PTFE/MoS₂ on mechanical and tribological properties of the composites were studied. Tribological tests were conducted on an Amsler friction and wear tester using a block‐on‐ring arrangement under dry sliding and oil lubricated conditions, respectively. The results showed that generally speaking POM nanocomposites had better stiffness and tribological properties than corresponding POM composites attributed to the high surface energy of nanoparticles, except that the tensile strength of three composites and dry‐sliding tribological properties of POM/3%Al₂O₃ nanocomposite decreased due to the agglomeration of nanoparticles. Tribological properties differed under dry sliding and oil lubricated conditions. The friction coefficient and wear volume of POM nanocomposites under oil lubricated condition decreased significantly. The increased deformation resistance supported the increased wear resistance of POM nanocomposites. POM/PTFE/MoS₂/3%Al₂O₃ nanocomposite had the best mechanical and tribological properties of all three composites, which was attributed to the synergistic effect of nanoparticles and PTFE/MoS₂. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Effects of compatibilizer,compounding method,extrusion parameters,and nanofiller loading in clay‐reinforced recycled HDPE/PET nanocomposites

Nanocomposites based on recycled high density polyethylene (rHDPE), recycled polyethylene terephthalate (rPET), and organoclay (C10A) were made using twin screw extruder followed by hot pressing. The independent effects of polymer/clay compatibility, preparation method, extrusion parameters, and clay loadings were investigated. Ethylene‐glycidyl methacrylate could effectively improve the compatibilization of immiscible rHDPE/rPET blend with clay, which confirmed by the good polymers‐clay adherence and domain size reduction obtained in scanning electron microscopy images. Although intercalated structures were observed in the composites made by one‐step compounding, in the composites prepared by two‐step extrusion method, enhanced dispersion of clay in polymer blend was found from X‐ray diffraction results. Higher extrusion temperature and intermediate speed of rotation (90 rpm) appeared to increase the mechanical properties due to improvement of nanofiller dispersion in matrix. Results showed that the stiffness increased whereas tensile and impact strength decreased with clay content. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42287.     

Experimental investigation of the influence of the compounding process and the composite composition on the mechanical properties of a short flax fiber–reinforced polypropylene composite

Polypropylene (PP) composites containing 20 wt% short flax fibers are prepared, and the process parameters such as throughput, rotational speed, and screw configuration are varied during melt compounding with a corotating intermeshing twin‐screw extruder. The investigations reveal that low rotational speeds, high throughputs, and moderate shear energy inputs by the screw configuration led to an optimum set of mechanical properties. To investigate the influence of different composite compositions on the mechanical properties, composites with fiber contents between 0 and 40 wt% and maleic anhydride‐grafted PP (PP‐g‐MA) contents between 0 and 7 wt% are prepared. Increasing fiber contents enhance the Young's modulus and decrease the elongation at break and the notched impact strength. The tensile strength is barely affected. The addition of PP‐g‐MA increases the tensile strength as well as the elongation at break, whereas the Young's modulus is not influenced. Thus, PP‐g‐MA enhances the adhesion between PP and flax fibers significantly. POLYM. COMPOS., 36:2282–2290, 2015. © 2014 Society of Plastics Engineers     

Polycarbonate/molybdenum disulfide/carbon black composites: Physicomechanical,thermal, wear,and morphological properties

To investigate the influence of molybdenum disulfide (MoS₂) as solid lubricant and filler on the polycarbonate (PC) and carbon black (CB) composites, PC containing one weight percentage of CB powder was compounded and extruded with 0.5, 1.0, 2.0, and 3.0 weight percentage of MoS₂ powder in a co‐rotating twin screw extruder. Thus, the fabricated PC/CB/MoS₂ composites were characterized for physicomechanical properties such as density, void content, surface hardness, tensile behaviors, and impact strength. The thermal characteristics of the composites have been studied by differential scanning calorimetry and dynamic mechanical analysis (DMA). The effect of MoS₂ content, loads and sliding distances on wear characteristics of the composites were evaluated using pin‐on‐disc equipment. It was found that wear, friction, and laser etching resistance of PC/CB/MoS₂ composites increased with increase in MoS₂ content along with improvement in tensile and impact strengths. DMA analysis indicates the storage modulus of PC/CB/MoS₂ composites increased with increase in MoS₂ content below the glass transition temperature (T_g) of PC. Worn surfaces and laser etched surfaces were examined with scanning electron microscopy and optical microcopy respectively to have better insight of the wear and laser etching mechanism. It was observed that the MoS₂ as solid lubricant played major role in improving resistance to wear, friction, and laser etching. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

A super‐toughened nylon 12 blends via anionic ring‐opening polymerization of lauryllactam in a twin screw extruder. Preparation,morphology, and mechanical properties

Nylon 12 blends (BP) with nitrile‐butadiene ultrafine full‐vulcanized powdered rubber (NBUFPR) were successfully synthesized in a corotating intermeshing twin screw extruder via anionic ring‐opening polymerization of lauryllactam at 250°C. The in situ formed blends were characterized by mechanical test, fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. A brittle‐tough transition occurs when NBUFPR content is 4 wt%. And the notched Izod impact strength achieves 989 J m^?1 when 5 wt% NBUFPR was added. Because of the good dispersion property of NBUFPR during the process ofreactive extrusion, the interparticle distance decrease remarkably. Besides, the in situ formed NBUFPR‐graft‐PA12 leads to better adhesion between the two phases. For comparison, another series of blends (BL) were also prepared by melt blending hydrolytic‐polymeric PA12 and NBUFPR in the same twin screw extruder. Brittle‐tough transition did not appear in BL blends within the same range of NBUFPR content. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers