The Effect of ultra‐high speed twin screw extrusion on ABS/organoclay nanocomposite blend properties

Acrylonitrile butadiene styrene (ABS) nanocomposites containing Cloisite 11 organoclay at 2 wt% were prepared using a 60 L/D ultra‐ high speed twin screw extruder (TSE), with speeds ranging from 400 to 4000 rpm. The purpose of this study was to investigate the effect of high shear melt processing on the intercalation and exfoliation of organoclay in the polymer, as well as the mechanical and rheological properties of the material. X‐ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) results showed better intercalation of the nanofiller with increasing screw speed up to a point, and indicated an exfoliated structure of the nanocomposites extruded at 4000 rpm. Mechanical and rheological testing results indicated that by adding organoclay to ABS, the properties improved with increasing screw speed up to an optimum value of 2000 rpm. However, at the higher screw speeds of 3000 and 4000 rpm, the intense shear history led to a decrease in properties, most likely due to chain scission and molecular weight reduction. Similar trends were observed in rheological properties of the nanocomposite as well. At 2000 rpm, the results indicate that the lowering of the molecular weight due to shear effects is balanced by good intercalation/exfoliation of the organoclay. POLYM. ENG. SCI., 57:60–68, 2017. © 2016 Society of Plastics Engineers     

Effect of processing parameters on the mechanical properties of in situ compatibilized polybutylene terephthalate/acrylonitrile–butadiene–styrene blends

To evaluate mechanical properties of blends prepared by intermeshing corotating twin‐screw extrusion (ICTSE), it is usually necessary to injection mold specimens after the extrusion mixing process. At this study an alternative method is used to obtain testing specimens from ribbons extruded polybutylene terephthalate/acrylonitrile–butadiene–styrene blends, (PBT/ABS), compatibilized with methyl methacrylate–glycidyl methacrylate‐ethyl acrylate (MGE) by ICTSE, and then to correlate their mechanical properties with the processing parameters. Regarding to the extrusion process parameters, it has been noted that higher feed rates, lower screw speeds and narrower kneading blocks have reduced the ductile‐brittle transition temperature (DBTT) of the compatibilized PBT/ABS blends, thereby suggesting that the molecule integrity of blend polymeric components has been preserved and that a good dispersion of the ABS domains in the PBT matrix has been achieved. Injection molded PBT/ABS blends were obtained to compare to the extruded ribbons. The mechanical tests for both specimens have shown the same trends. The injection molded samples have presented poorer impact strength, tensile strain at break and tensile strength, when compared to the respective extruded samples. That behavior has been attributed to the high level of molecular orientation resulting from the injection molding process and mainly to PBT degradation during process. The PBT degradation could have increased its degree of crystallinity, which has been confirmed by DSC measurements. As result, the blend became more brittle, decreasing its Izod impact strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhancing the electrical conductivity of carbon black/graphite nanoplatelets: Poly(ethylene‐butyl acrylate) composites by melt extrusion

The influence of processing parameters such as screw geometry, temperature profile, and screw speed on the electrical properties of hybrid composites consisting of graphite nanoplatelets and carbon black in ethyl butyl acrylate was studied. Two different screws were used to compound the hybrid composites at two different temperatures and two different screw speeds. A beneficial effect was noted with regard to the electrical properties when adding nanoplatelets to the filler system. The cause could be a synergistic effect due to the difference in particle shape of the two fillers. Lower percolation thresholds were obtained with the conventional screw due to less breakage of the graphite nanoplatelets compared to the barrier screw. No significant changes of the electrical properties were observed when changing the temperature profiles or the screw speeds. Furthermore, the melt viscosity of the compounds was not appreciably affected at the rather low filler contents used here. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42897.     

High-speed gel-spinning of ultra-high molecular weight polyethylene

Summary This communication is concerned with the gel-spinning of ultrahigh molecular weight polyethylene (UHMWPE) at speeds up to 1500 m/min. It was found that 5 wt% solutions of UHMWPE in paraffin oil could be extruded through a conical die at a rate of 100 m/min. without the appearance of filament irregularities due to elastic solution fracture. These elastic turbulences occur at extrusion speeds of about 5 m/min. Without the addition of 1 wt% of Aluminium-stearate the spinline could be stretched at most to 60 m/min at 170°C but at 210°C it did not break at a speed of 1500 m/min.These high-speed gel-spinning experiments at temperatures around 200°C yielded polyethylene fibers with a tensile strength of 3.5 GPa. It was observed that drying of the as-spun fiber containing n-hexane at constant length led to excessive crazing.     

ABS/PS共混改性研究

采用在材料熔融挤出共混过程中提高双螺杆挤出机螺杆转速的方法,研究了较高螺杆转速条件下双螺杆挤出机的机械剪切应力和弹性体的种类、用量等因素对丙烯腈-丁二烯-苯乙烯共聚物(ABS)/聚苯乙烯(PS)共混材料力学性能和加工流动性能的影响。结果表明,双螺杆挤出机的高剪切应力可促进分散相颗粒的分散和界面结合力的增强,引起共混材料力学性能和熔体流动速率的改善。丁腈橡胶(NBR)粉末对ABS/PS共混材料具有增容增韧作用,挤出共混温度为220℃,螺杆转速在720 r/min,NBR粉末质量分数为10%时,ABS/PS共混材料的缺口冲击强度为16.4 kJ/m2,比改性前约提高1.6倍,达到ABS树脂冲击韧性的指标,并保持了良好的加工流动性。     

Relationship between processing method and microstructural and mechanical properties of poly(ethylene terephthalate)/short glass fiber composites

Composites of recycled poly(ethylene terephthalate) (PET) reinforced with short glass fiber (GF) (0, 20, 30, and 40 wt %) were compounded in a single‐screw extruder (SSE) and in a intermeshing corotating twin‐screw extruder (TSE). An SSE fitted with a barrier double‐flight screw melting section in between two single‐flight sections and a TSE with a typical screw configuration for this purpose were used. The composites were subsequently injection molded at two different mold temperatures (10 and 120°C), with all other operative molding parameters kept constant. The effects of processing conditions on composite microstructure, PET degree of crystallinity, and composite mechanical properties were evaluated. Appropriate dispersive and distributive mixing of the glass fiber throughout the PET matrix as well as fine composite mechanical and thermal‐mechanical properties were achieved regardless of whether the composites were prepared in the SSE or TSE. The performance of the SSE was attributed to the efficiency of the barrier screw melting section in composite mixing. The mold temperature influenced the mechanical properties of the composites, by controlling of the degree of crystallinity of the PET in the composites. For a good balance of mechanical and thermal‐mechanical properties, high mold temperatures are desirable, typically, 120°C for a mold cooling time of 45 s. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effect of ultrasonic extrusion on properties of colloids and bio-based nanocomposites containing epoxidized soybean oil and nanoclay

Colloid prepared with epoxidized soybean oil (ESO) and a nanoclay, organically modified montmorillonite (OMMT), has been processed using an ultrasonic twin-screw extruder under various ultrasonic amplitudes and screw rotation speeds. Ultrasonic treatment has significantly increased OMMT dispersion in ESO, according to wide angle X-ray diffraction and rheological data. Yield stress, storage and loss modulus, and complex viscosity and relaxation time of the colloid have been increased with increase of ultrasonic amplitude. Under certain high ultrasonic amplitudes, the increase of one to two orders of magnitude in the above-mentioned properties of colloids has been observed. Creep and recoverable compliance have been decreased with the increase of ultrasonic amplitude. The tremendous changes in rheological properties of the colloid are a result of significantly improved OMMT dispersion with the aid of ultrasonic treatment. With no or low ultrasonic treatment, a higher screw rotation speed has improved OMMT dispersion since it brings more mixing effect. However, at high ultrasonic amplitudes, a higher rotation disrupts jet flow and has led to less dispersion improvement compared with the same colloid extruded at a lower rotation speed. Colloids extruded at 400 rpm were cured using triethylenetetramine to prepare bio-based nanocomposites. The nanocomposite prepared using colloid treated at 13 μm shows improved tensile strength and modulus compared with the nanocomposite prepared using untreated colloid.     

Mechanical properties and creep resistance in polystyrene/polyethylene blends

Recycled plastics, predominantly high‐density polyethylene (PE), are being processed in the shape of dimension lumber and marketed as “plastic lumber.” One drawback to these products is their low creep resistance or high creep speed. The objective of this study was to examine the feasibility of reducing the creep speed of PE‐based products by blending the PE with a lower‐creep plastic, in this case polystyrene (PS). Various blends of PE and PS were prepared in either a laboratory extruder or a bowl mixer and then compression‐molded. The mechanical properties, creep behavior, morphology, and thermal properties of extruded and compression‐molded samples were determined. The modulus of elasticity of the extruded blends could be estimated by a weighted average of PS and PE, even in the absence of a compatibilizer. Processing strongly affected the morphology and mechanical properties of the blends. For 50% PS : 50% PE blends, the stress–strain curves of the extruded samples showed PE‐like behavior, whereas those from compression‐molded samples were brittle, PS‐like curves. Flexural strength was 50% higher in the extruded samples than in those from compression molding. The creep experiments were performed in three‐point bending. Creep speed was lower in 50% PS : 50% PE and 75% PS : 25% PE blends than in pure PS. Creep speed of 75% PS : 25% PE was lowest of all the extruded blends. PE formed the continuous phase even when the PS content was as high as 50 wt %. For a 75% PS : 25% PE blend, cocontinuous phases were observed in the machine direction. A ribbonlike PS‐dispersed phase was observed in the 25% PS : 75% PE and 50% PS : 50% PE samples. Blending low‐creep‐speed PS with high‐creep‐speed PE appeared to successfully improve the performance of the final composite. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1100–1108, 2000     

Influence of processing parameters on the degradation of poly(L‐lactide) during extrusion

The influence of processing conditions during melt extrusion on the degradation of poly(L ‐lactide) (PLLA) has been investigated. PLLA polymer was processed by melt extrusion in a double screw extruder at 210 and 240°C. For each extrusion temperature, two screw rotation speeds, 20 and 120 rpm, were used. To investigate the influence of moisture on the thermal degradation during processing, the PLLA granules were dried at 100°C for 5 h and then either extruded directly or conditioned at 65% RH, 20°C for 24 h prior to extrusion. The results show that a decrease in molecular weight measured as number‐average (M_n) molecular weight occurs for all combinations of process parameters used. At processing temperature of 210°C, the change in molecular weight for the dry granules was shown to be dependent on the residence time (i.e., screw rotation speed) in the melt. By changing the screw rotation speed from 120 to 20 rpm at 210°C, M_n decreased from 33,600 to 30,200 g/mol. When the processing temperature was increased to 240°C, the dry granules showed an M_n of 25,600 and 13,600 g/mol when extruded at 120 and 20 rpm, respectively. M_n for the conditioned specimens extruded at 210°C was 18,400 g/mol when processed at 120 rpm and 12,300 g/mol at 20 rpm. When processed at 240°C, 20 rpm, M_n is independent of whether the granules were dry or moist prior to extrusion. It is probably due to the fact that the degradation at 240°C is so extensive that the presence of moisture in the polymer does not contribute further to the degradation process. The stress and strain at break decreased due to degradation and were dependent on the molecular weight of the samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2128–2135, 2001     

Effects of processing conditions on the fiber length distribution and mechanical properties of glass fiber reinforced nylon‐6

The effects of processing conditions on fiber length degradation were investigated in order to produce composites with higher performance. Nylon‐6 was compounded with glass fibers in a twin‐screw extruder for various combinations of screw speed and feed rate. Collected samples were injection molded and Izod impact and tensile tests were performed in order to observe the effect of fiber length on the mechanical properties. Also, by using the extruded and injection molded smaples, fiber length distribution curves were obtained for all the experimental runs. Results show that when the shear rate is increased through the alteration of the screw speed and/or the feed rate, the average fiber length decreases. Impact strength, tensile modulus and tensile strength increase, whereas elongation at break decreases with the average fiber length.     

The effect of melt viscosity on thermal efficiency for single screw extrusion of HDPE

In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process.     

Online monitoring of the thermal degradation of POM during melt extrusion

Because of its high stiffness, chemical resistance, and low viscosity, Poly (oxymethylene) (POM) is of high relevance for technical applications. The thermal degradation of POM during processing affects its final properties and decreases the long‐term stability. The degradation is indicated by the emission of formaldehyde (FA) gas. The aim of this study is to monitor the thermal degradation of POM online, during the melt extrusion in a co‐rotating twin screw extruder (TSE). The effect of the processing conditions on the thermal stabilisation of the POM is observed by FA emission and online viscosity measurements. The effect of processing conditions on the compounding of POM with two different FA scavengers is also studied. Fourier transform infrared (FTIR) spectroscopy is used for the online measurement of FA gas and acetyl acetone colour measurement for the offline characterisation. The online viscosity is measured by passing the melt through a slit die at constant volume flow rate. An enhanced thermal degradation is found with decreasing throughput and increasing screw speed. A good correlation between the online viscosity and offline FA measurement is observed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

黏度对水发泡聚苯乙烯发泡性能的影响

采用水作为物理发泡剂,对聚苯乙烯(PS)进行挤出发泡。研究了低温PS水发泡的流变性能,并研究了黏度对PS发泡制品性能的影响。结果表明:水会影响PS在发泡加工过程中的黏度;在低温情况下,水发泡后的PS仍然具有流动性;其黏度随剪切速率的增大而减小,在相同的剪切速率下,温度越高黏度越低。当模头温度为140℃、螺杆转速为15r/min时,可制备出表面光滑、泡孔细密均匀、质轻的PS水发泡制品。     

Void content of a viscoelastic composite melt: Reduction during mixing

Mica and polystyrene in four ratios were sheared for three different times, each at three speeds, and at two temperatures in the viscoelastic region, in a screw mixer. From precise density measurements on the resulting composites, void volume fractions were calculated and found to be proportional to mica concentration and independent of total screw rotations. Experimental void/mica ratios were represented by a kinetic model; they decreased from a single value common to all conditions to a steady-state value proportional to the square root of the screw speed. Void formation and elimination occur simultaneously. The goodness of the fit to the data is insensitive to the details of the kinetic model. The characteristic rate constant depends only on temperature, increasing at the same rate as the reciprocal of the low-frequency dynamic viscosity. Cavitation in regions of diverging flow of the mixer may inhibit void elimination.     

高黏微观混合表征新方法及其在双螺杆挤出机中的应用

在双螺杆反应挤出过程中微观混合程度是重要的操作参数。一些特别设计的经典小分子竞争反应体系常用于表征微观混合,但其用于大分子反应的高黏物系时由于大小分子扩散不同容易引起偏差。今建立了一种由苯乙烯-(3-异丙烯基-α,α′-二甲基苄基-异氰酸酯)共聚物(PSt-co-TMI)与9-(甲胺基-甲基)蒽(MAMA)为快反应、PSt-co-TMI与己内酰胺(ε-CL)为慢反应的大分子竞争反应体系,并应用于TSE-20可开启式自啮合双螺杆挤出机中微观混合状况的表征。考察了不同螺杆位置处产物的分离指数和转化率;研究了螺杆转速、喂料速率等对微观混合质量的影响。结果表明:该大分子竞争体系可很好地用于双螺杆挤出机中高黏物系微观混合表征;微观混合在物料熔融后相当短的流程内即完成,微观混合质量在挤出过程稳定后保持不变;对于推进式元件,在相同的喂料速率下随着螺杆转速的增加微观混合质量下降;填充度是影响推进元件中微观混合质量的重要因素,在特定的实验条件随喂料量增大微观混合质量反而改善的原因在于填充度的提高有利于微观混合。     

Effects of ultrasonic oscillation on processing behaviors of PS,EPDM, and PS/EPDM blend

In this study, the extrusion processing behaviors of polystyrene (PS), ethylene–propylene–diene terpolymer (EPDM), and their blend (PS/EPDM, 80/20) were studied by using a special ultrasonic oscillation extrusion system developed in our laboratory. The die pressure and volume flow rate were measured at different ultrasonic intensities and screw rotation speeds. The dependences on ultrasonic intensity of die pressure, volume flow rate, and apparent viscosity of polymers, as well as die swell at the same screw rotation speed were investigated. The effects of screw rotation speed on the processing behaviors of polymers and their blend at the same ultrasonic intensity were also studied. The experimental results showed that in the presence of ultrasonic irradiation, the processibilities of polymers and their blend were improved. Their possible mechanism is discussed in this article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1856–1863, 2006     

Enhanced (thermo)mechanical properties in biobased poly(l-lactide)/poly(amide-12) blends using high shear extrusion processing without compatibilizers

Compatible and partly-biobased poly(l -lactide) (PLA)/polyamide-12 (PA12) blends (30 wt% PA12) are here processed by twin-screw extrusion at high shear without added compatibilizers and the effect of several processing parameters (screw speed, feed rate) on final properties (tensile strength, ductility, impact toughness, thermal resistance) is addressed. High tensile strengths could be maintained for these blends with a maximal ductility (225%) and impact toughness (48 kJ/m²) achieved for an optimal screw speed of 800 rpm. However, extreme screw speeds higher than 800 rpm dramatically reduce ductility and impact toughness. Concerning thermal resistance, a constant increase of the heat deflection temperature is observed with the screw speed and thermal resistance up to 123°C could be obtained. In this respect, processing conditions of PLA/PA12 blends have profound positive effects on all (thermo)mechanical properties. Blend morphologies were revealed by scanning electron microscopy and refined PA12 fibrils are detected at optimal processing conditions. Properties deterioration were correlated to a PA12 fibrillar-to-ellipsoidal shape transition at extreme screw speeds arising from PLA degradation and attesting for the importance of the PA12 fibrillation process on final properties. Consequently, PLA/PA12 blends represent interesting biobased candidates for high-performance applications and their optimization could be easily performed by playing with extrusion conditions without compatibilizers.     

Morphological evolution of polypropylene/polystyrene blends in a twin‐screw extruder

The effects of the blend composition and rotation speed on the morphological evolution of polypropylene (PP)/polystyrene (PS) blends were investigated in a twin‐screw extruder. When PS was the major component, the rate of melt and the rate of dispersion played final roles in the morphological development of the polymer melts. However, when PP was the major component, the rate of dispersion and the rate of coalescence played key roles. A high tendency to coalesce occurred at a high rotation speed and/or a high content of the dispersed phase. When the PP/PS blend composition was close to 1, a cocontinuous morphology was observed to transmute into a coarse one with increasing rotation speed. Attempts were made to correlate the morphology and mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nanocomposites based on aromatic polyesters and organically modified clay

Milled polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT) were mixed with organically modified clay and extruded to prepare nanocomposites by melt intercalation. The modifier of the nanofiller belongs to the group of trialkylbenzylammonium cations. Manufacturing of the materials was carried out with a co‐rotating twin‐screw‐extruder at 230°C and 240°C for PTT and PBT, respectively. A concentration of 3% of the inorganic filler component in the composites was aimed at. The influence of mechanical stress during extrusion on the stability of the neat polymers was tested at different speeds of rotation between 100 rpm and 800 rpm. The composites were characterized with regard to the experimental filler content and the properties of the matrix polymers like melt and crystallization temperatures, degrees of crystallinity, intrinsic viscosities, and melt viscosities. Additionally, mechanical properties were analyzed by tensile tests and discussed in terms of processing and the filler presence. The dominance of PBT as polymer matrix was highlighted. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of Temperature and Loading Rate on the Mechanical Properties of a High Temperature Epoxy Adhesive

The variation of the mechanical properties of adhesives with temperature and strain rate is one of the most important factors to consider when designing a bonded joint due to the polymeric nature of adhesives. It is well known that adhesive strength generally shows temperature dependence. Moreover, in many structural applications, the applied loads can be dynamic and the design of the joint requires the knowledge of the high loading rate mechanical behaviour of the adhesive. In this study, the combined effect of the temperature and test speed on the tensile properties of a high temperature epoxy adhesive was investigated. Tensile tests were performed at three different test speeds and various temperatures (room temperature (RT) and high temperatures (100, 125 and 150°C)). The glass transition temperature (T _g) of the epoxy adhesive investigated is approximately 155°C. The ultimate tensile stress decreased linearly with temperature (T) while increased logarithmically with the loading rate, which is in the accord with the Airing's molecular activation model.