单螺杆挤出机连续脱硫制备再生胶的结构与性能

利用本课题组研制的单螺杆挤出机,对废旧轮胎胶(GTR)粉进行连续脱硫制备再生胶(DGTR),并对DGTR进行再硫化制成DGTR硫化试样.结果显示,随螺杆转速增加,DGTR凝胶含量和DGTR硫化试样交联密度逐渐降低,DGTR硫化试样的拉伸强度和拉断伸长率有所提高;螺杆转速设定为40 r·min^-1时,在205℃脱硫温度下取得了最好的脱硫效果,DGTR硫化试样的拉伸强度和拉断伸长率分别约为11 MPa和386%.从红外光谱和光电子能谱的分析结果推测,在单螺杆挤出机的剪切和热等的共同作用下,GTR粉中部分S-S键和C-S键发生了断裂.     

Effects of shear stress and subcritical water on devulcanization of styrene–butadiene rubber based ground tire rubber in a twin‐screw extruder

The devulcanization reaction of styrene–butadiene rubber (SBR) based ground tire rubber (GTR) in GTR/ethylene–propylene–diene monomer rubber (EPDM) blend was investigated through a compound‐induced reaction by increasing screw rotation speed and being in the presence of subcritical water. The effects of temperature, pressure, screw rotation speed, or promoting agents on the gel content, Mooney viscosity, and Fourier transform infrared spectra of the sol of the devulcanized blends (devulcanized ground tire rubber (DGTR)/EPDM) were measured, and the mechanical properties and microstructures of the revulcanized blend ((DGTR/EPDM)/SBR) were characterized. The results show that subcritical water as a swelling agent and reaction medium promotes the devulcanization reaction, increases the selectivity of the crosslink breakage, keeps the extrusion material from oxidative degradation, reduces the gel particle size of the devulcanized blends, and significantly improves the mechanical properties of the revulcanized SBR/(DGTR/EPDM) blends. In subcritical water, the suitable promoting agents (alkylphenol polysulfide 450, hydrogen peroxide H₂O₂, or 450/H₂O₂) accelerate the devulcanization reaction, keep the double bond content, and lead to further decrease of the gel content and Mooney viscosity of the devulcanized blends and further increase of the mechanical properties of the revulcanized SBR/(DGTR/EPDM) blends. Especially the compound promoting agent (450/H₂O₂) improves the selectivity of the crosslink breakage in devulcanization of SBR‐based GTR. When 450/H₂O₂ is added as a compound promoting agent at the best reaction condition in subcritical water (200°C, 1.6 MPa and 1000 rpm), the tensile strength and elongation at break of the revulcanized SBR/(DGTR/EPDM) blends reach to 85.4% and 201% of vulcanized SBR (24.0 MPa, 356%), respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1845–1854, 2013     

亚临界流体挤出法复合诱导SBR基轮胎胶脱硫化及 再硫化材料力学性能

在SBR基轮胎胶(GTR)与三元乙丙橡胶（EPDM）混合物的熔融挤出过程中,采用改变亚临界流体品种和提高螺杆转速的方法,研究了亚临界流体（水,乙醇,丙醇）、螺杆转速、烷基酚多硫化物促进剂（450）以及温度对脱硫共混物（DGTR/EPDM）凝胶含量、门尼粘度、溶胶红外光谱及脱硫共混物共混丁苯橡胶（SBR）再硫化材料（SBR/(DGTR/EPDM)）力学性能的影响,对再硫化材料的试样断面形貌也进行了SEM观察。实验结果表明：亚临界流体（水,乙醇,丙醇）作为一种溶胀剂和反应性介质能够很好地促进脱硫反应,提高交联键断裂的选择性,降低脱硫产物的凝胶含量和凝胶颗粒尺寸并明显提高脱硫共混物共混丁苯橡胶再硫化材料的力学性能,其中亚临界乙醇的作用最显著。当450作为一种脱硫促进剂,在最优亚临界乙醇挤出反应条件（200℃,1.6 MPa,600 rpm）下,脱硫共混物共混丁苯橡胶分别达到丁苯生胶混炼硫化材料拉伸强度（24.0MPa）和断裂伸长率（356%）的99.6%和209%。     

Recycling of tire‐curing bladder by ultrasonic devulcanization

The recycling of butyl rubber‐based tire‐curing bladder was carried out by means of a grooved barrel ultrasonic extruder. Die pressure and ultrasonic power consumption were measured as a function of flow rate and ultrasonic amplitude. Gel fraction and crosslink density of the ultrasonically devulcanized rubber were substantially reduced. In turn, this led to some reduction in gel fraction and crosslink density in the revulcanized rubber. These findings were correlated with dynamic properties and the cure behavior of the devulcanized rubber. The mechanical properties of the revulcanized rubber, dependent on processing conditions during devulcanization, were compared with that of the virgin vulcanizate. Good mechanical properties of revulcanized rubber was achieved with 86 and 71% retention of the tensile strength and the elongation at break respectively, and with modulus increased by 44%. The devulcanized rubber was found to contain tiny gel particles of a wide size distribution with a predominant size of <4 μm. POLYM. ENG. SCI., 46:8–18, 2006. © 2005 Society of Plastics Engineers     

Thermomechanical reclaiming of ground tire rubber via extrusion at low temperature: Efficiency and limits

Thermomechanical reclaiming of ground tire rubber (GTR) was performed at different temperatures (60, 120, and 180°C) using a co‐rotating twin‐screw extruder. Obtained samples were used in styrene‐butadiene rubber (SBR) blends. As reference samples, SBR compounds containing untreated GTR were used. Curing characteristics, static and dynamic mechanical properties, and morphology of the obtained blends were determined. The results show that the increase of barrel temperature during the thermomechanical reclaiming of GTR has a positive effect on the decrease of screw torque (lower machine load) and decrease of Mooney viscosity (better processing characteristics). However, mechanical properties and crosslink density of rubber revulcanizate decreased with increasing barrel temperature during the reclaiming process. SBR blends with 50 phr of reclaimed rubber showed increasing phase compatibility between SBR matrix and the reclaimed rubber, which was confirmed by mechanical properties and morphology measurements. J. VINYL ADDIT. TECHNOL., 22:213–221, 2016. © 2014 Society of Plastics Engineers     

轮胎胶应力诱导脱硫化及PE-HD动态交联热塑性弹性体制备

采用在废旧轮胎胶粉(GTR)与高密度聚乙烯(PE-HD)的熔融挤出过程中提高双螺杆挤出机螺杆转速的高剪切应力诱导方法,研究了双螺杆挤出机的螺杆转速、挤出反应温度及脱硫促进剂仲丁醇、烷基酚多硫化物(420或450)和正丁胺对轮胎胶脱硫共混物的凝胶含量、熔体流动速率、溶胶红外吸收光谱及轮胎胶脱硫共混物/三元乙丙橡胶(EPDM)动态交联热塑性弹性体力学性能的影响。结果表明:高转速同向双螺杆挤出机的高剪切作用可诱发废旧轮胎胶共混物中交联网络的断链和解交联反应,引起脱硫共混物凝胶含量的下降、未熔融凝胶颗粒尺寸的减小及熔体流动速率的增加;4种促进剂均具有明显促进脱硫反应的作用,其中450或正丁胺的促进脱硫效果较好,并引起脱硫共混物凝胶含量下降、熔体流动速率上升及动态交联热塑性弹性体力学性能的明显改善;当以正丁胺为脱硫促进剂时,最佳脱硫反应条件(240℃和1000r/min)下,脱硫共混物/EPDM动态交联热塑性弹性体的拉伸强度和断裂伸长率分别达到12.5MPa和440.6%。     

Recycling of roofing membrane rubber by ultrasonic devulcanization

The recycling of vulcanizates based on EPDM roofing membrane rubber using a new ultrasonic devulcanization reactor with a grooved barrel was carried out. This reactor provided continuous devulcanization at an output as high as 2.52 g/s. Die pressure and ultrasonic power consumption were measured as a function of processing conditions. The mechanical properties of virgin vulcanized and revulcanized roofing membranes were measured. Tensile strength of the revulcanized rubber was found to be similar to that of the virgin vulcanizate. Gel fraction, crosslink density, and dynamic properties of the virgin vulcanizate, the ultrasonically devulcanized rubber, and the revulcanized rubber were determined. Also, dynamic properties and the cure behavior of the virgin compound and of the devulcanized roofing membrane were investigated. All these properties were found to be dependent on processing conditions during devulcanization. The thermal stability of the virgin compound, virgin vulcanizate, and devulcanized and revulcanized rubbers were studied by means of TGA. It was found that the thermal stability of all the vulcanizates in air and nitrogen environments remained practically intact, while that of devulcanized rubber in air environment was a function of processing conditions.     

Preparation of rubber composites from ground tire rubber reinforced with waste‐tire fiber through mechanical milling

Composites made from ground tire rubber (GTR) and waste fiber produced in tire reclamation were prepared by mechanical milling. The effects of the fiber content, pan milling, and fiber orientation on the mechanical properties of the composites were investigated. The results showed that the stress‐induced mechanochemical devulcanization of waste rubber and the reinforcement of devulcanized waste rubber with waste‐tire fibers could be achieved through comilling. For a comilled system, the tensile strength and elongation at break of revulcanized GTR/fiber composites reached maximum values of 9.6 MPa and 215.9%, respectively, with 5 wt % fiber. Compared with those of a composite prepared in a conventional mixing manner, the mechanical properties were greatly improved by comilling. Oxygen‐containing groups on the surface of GTR particles, which were produced during pan milling, increased interfacial interactions between GTR and waste fibers. The fiber‐filled composites showed anisotropy in the stress–strain properties because of preferential orientation of the short fibers along the roll‐milling direction (longitudinal), and the adhesion between the fiber and rubber matrix was improved by the comilling of the fiber with waste rubber. The proposed process provides an economical and ecologically sound method for tire‐rubber recycling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4087–4094, 2007     

废旧轮胎胶粉应力诱导脱硫反应影响因素的研究

在废旧轮胎胶粉/EPDM的熔融挤出过程中,以仲丁醇为脱硫反应促进剂,研究螺杆转速和挤出反应温度对脱硫共混物凝胶质量分数(w)、凝胶分子链结构以及SBR/脱硫共混物再硫化材料物理性能的影响。结果表明:在废旧轮胎胶粉/EPDM的熔融挤出过程中,随着螺杆转速和挤出反应温度的升高,废旧轮胎胶粉颗粒所受的机械剪切应力作用增强,引起废旧轮胎胶粉中交联网络的断裂、降解或解交联反应,导致脱硫共混物w显著减小以及SBR/脱硫共混物再硫化材料中凝胶粒子尺寸明显减小;添加仲丁醇有利于脱硫反应的进行,并具有抑制交联副反应和保护脱硫产物中双键的作用,使脱硫共混物的w进一步减小;在螺杆转速为1 000 r.min-1、挤出反应温度为240℃的条件下,SBR/脱硫共混物(添加仲丁醇)再硫化材料的拉伸强度和拉断伸长率分别为19.3 MPa和567%。     

Friction and wear behavior of styrene butadiene rubber‐based composites reinforced with microwave‐devulcanized ground tire rubber

In this work, the tribological properties of a new material obtained by revulcanization with styrene butadiene rubber (SBR) and devulcanized ground tire rubber (GTR) were investigated. GTR was devulcanized using the microwave method at a constant power while varying the microwave exposure time. Devulcanized rubber (DV‐R) and untreated GTR were revulcanized by mixing with SBR at different rates (10, 30, 50 phr). To determine friction and wear characteristics of the samples, pin (ball) on disc and abrasion tests were conducted. Scanning electron microscopy (SEM) was employed to observe the worn surfaces of the composites to correlate the experimental test results to the wear mechanisms. All of these tests and experiments were performed on original vulcanized rubber samples for comparison. The composites exhibited different friction and wear behavior due to morphology, dispersion behavior and devulcanization functionalization of ground tire rubber. In general, DV‐R/SBR composites exhibited improvement in both mechanical and tribological properties. However, the enhanced compatibility of DV‐R resulting from the specific chemical coupling of DV‐R with SBR was crucial for the mechanical, friction and wear properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42419.     

Balancing mechanical properties and processability for devulcanized ground tire rubber using industrially sized single‐screw extruder

Devulcanized ground tire rubber (DGTR) samples were produced using an independently developed industrially sized single‐screw extruder. The DGTR was further revulcanized to produce revulcanized DGTR (RDGTR) samples. The structure and properties of the produced samples were investigated via tests and characterization of sol fraction, crosslink density, Fourier transform infrared spectroscopy spectra, X‐ray photoelectron spectroscopy spectra, Mooney viscosity, curing characteristics, dynamic rheology, tensile properties, and surface morphology. The results demonstrate that the extruder can effectively break up crosslinked structure of ground tire rubber to achieve high devulcanization level (characterized by sol fraction and crosslink density), which is mainly associated with its moderate shear strength. The balance between mechanical properties and processability for the DGTR samples was analyzed. Lower ratios of main‐chain to crosslink scission and good processability (mainly characterized by modest Mooney viscosity) for the DGTR samples, and high tensile strengths and elongations at break for the RDGTR samples are obtained via appropriately combining the barrel temperature and screw speed. High quality DGTR sample with tensile strength and elongations at break of up to 11 MPa and 370%, respectively, is prepared under the conditions used in this work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43761.     

Effects of Extruder Parameters and Compositions on Mechanical Properties and Morphology of Maleic Anhydride Grafted Polypropylene/Waste Tire Blends

A co-rotating twin screw extruder was used for blending thermoplastic elastomeric blends of ground rubber tire (GRT) and maleic anhydride grafted polypropylene (PP-g-MA). The dynamic reaction occurring between the blends necessitates a study of the processing parameters of the extruder. The effects of the extruder screw configurations, screw speed, compatabilizer and blend ratios on the mechanical properties, and morphology was studied. Out of the four different screw configurations A, B, C, and D, screw D with reverse flow elements was found to be highly efficient with respect to mechanical properties, particularly at 100 rpm screw speed. SEM studies revealed that GRT and PP-g-MA are thermodynamically miscible under optimized screw configuration and processing condition of 100 rpm screw speed. SEM studies also show that the addition of compatibilizer increases the miscibility and, consequently, the mechanical properties. Finally, a composition involving GRT/PP-g-MA/SEBS-g-MA as 65/35/10 by weight was found to be optimum.     

铝塑复合管硅烷交联聚乙烯专用料的研究

研究了高密度聚乙烯（HDPE）／线性低密度聚乙烯（LLDPE）硅烷接枝交联体系。分析了过氧化二异丙苯（DCP），乙烯基三乙氧基硅烷（VTES），加工设备及工艺条件（温度，螺杆转速）对体系熔体流动速率（MFR）和凝胶含量的影响。并用Buss混炼设备制备出高流动性的铝塑复合管硅烷接枝交联PE专用料。     

Effect of dicumyl peroxide and phenolic resin as a mixed curing system on the mechanical properties and morphology of TPVs based on HDPE/ground tire rubber

Thermoplastic vulcanizates (TPVs) are a special group of thermoplastic elastomer with the characteristic that consists of rubber elasticity and the processability of thermoplastic polymers. TPVs based on high density polyethylene (HDPE)/ground tire rubber (GTR) with phenolic resin (HY‐2045) and dicumyl peroxide (DCP) as vulcanizing agents are prepared through dynamic vulcanization in this article. The blends consisting of 40/60 HDPE/GTR are melt‐mixed in an internal mixer and then pressed with a compression molding machine. The aim of this experiment is to study the influence of a compound curing agent system on the mechanical properties of the HDPE/GTR composites. The results indicate that the mechanical properties of the HDPE/GTR blends are improved significantly by adding 4 phr HY‐2045 and 0.3 phr DCP than those of TPVs without any vulcanizing agents after dynamic vulcanization. The X‐ray photoelectron spectroscopy study and the FTIR‐ATR analysis confirmed that the crosslinking phenomenon occurred in the preparation of TPVs; and the gel fraction analysis indicates that the GTR components and the HDPE components of the HDPE/GTR blends are all moderately crosslinked. In addition, the morphology of the HDPE/GTR blends has been investigated by scanning electron microscopy. POLYM. COMPOS., 36:1907–1916, 2015. © 2014 Society of Plastics Engineers     

Thermoplastic elastomers based on high‐density polyethylene,ethylene–propylene–diene terpolymer,and ground tire rubber dynamically vulcanized with dicumyl peroxide

Thermoplastic vulcanizates (TPVs) based on high‐density polyethylene (HDPE), ethylene–propylene–diene terpolymer (EPDM), and ground tire rubber (GTR) were dynamically vulcanized with dicumyl peroxide (DCP). The polymer blend was composed of 40% HDPE, 30% EPDM, and 30% GTR, and the concentration of DCP was varied from 0.3 to 3.6 parts per hundred rubber (phr). The properties of the TPVs were determined by evaluation of the gel fraction content and the mechanical properties. In addition, IR spectroscopy and differential scanning calorimetry analysis were performed as a function of the DCP content. Decreases in the Young's modulus of the blends and the crystallinity of HDPE were observed when the content of DCP was greater than 1.8 phr. The results regarding the gel content indicate that the presence of DCP promoted the crosslinking of the thermoplastic matrix, and optimal properties were obtained with 1.5% DCP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39901.     

Properties of natural rubber vulcanizates containing mechanochemically devulcanized ground tire rubber

The devulcanization of ground tire rubber (GTR) was carried out with a self-designed pan-mill type mechanochemical reactor. Gel fraction and crosslink density measurements confirmed the occurrence of stress induced mechanochemical devulcanization of GTR. The partially devulcanized GTR (dGTR) was blended with virgin natural rubber (NR) at different ratios. The curing characteristics and mechanical properties of these composites were investigated and compared with those composites of raw ground tire rubber (rGTR) and NR. The results showed that the tensile properties of the dGTR/NR vulcanizates were much better than those of the rGTR/NR vulcanizates, which are comparable to or even better than the virgin vulcanizate, indicating the significant benefit of mechanochemical devulcanization. At the GTR content of 10%, the tensile strength of the dGTR/NR blends increased to 23.2 MPa from 13.7 MPa of the rGTR/NR blends, enhanced by 69% through partial devulcanization of GTR, and the elongation at break increased by 47%.     

影响废旧轮胎胶粉热-机械剪切脱硫再生效果的因素

利用自行研制的长径比为60/1的强剪切型双螺杆挤出机对废旧轮胎胶粉进行热-机械剪切脱硫,用傅里叶变换红外光谱对脱硫胶粉进行了表征,考察了胶粉粒径和喂料螺杆转速与主机转速之比对脱硫胶粉凝胶含量、交联密度及再生胶力学性能的影响,以及脱硫过程中胶粉相对分子质量及其分布的变化。结果表明,随着胶粉粒径的增大,胶粉所受到的剪切力增强,脱硫效果也越好。随着转速比的增加,胶粉的脱硫程度提高;脱硫过程的第1个阶段是交联网络的破坏,第2个阶段除交联网络的破坏外分子主链也发生降解,再生胶的力学性能先增大后减小;当转速比为1.4时再生胶的扯断伸长率和弹性最好,拉伸强度也相对较高。     

The effect of adding devulcanized rubber on the thermomechanical properties of recycled polypropylene

This work aims to investigate the effect of adding vulcanized or partially devulcanized rubbers on recycled polypropylene (PPr), considering thermomechanical and morphological properties. The study proposes to better understand how structural changes underwent by rubber (after the devulcanization) contributed to improving the mechanical properties of the PPr. The PPr/rubber blends were prepared by a co-rotating twin-screw extruder and then were injected. The blends composed of the most devulcanized rubbers by microwaves with refined microstructure showed higher values of elongation at break and toughness. Data showed that the devulcanization process applied to the rubber interfered positively in its adhesion to the PPr. Data from dynamic mechanical analysis and atomic force microscopy indicated that the most devulcanized rubbers presented an interface more connected to PPr. These chemical interactions possibly impacted the mechanical properties of the PPr. Moreover, dilatation processes favored the fracture mechanisms of the PPr when rubber was added to it.     

Effects of composition and temperature on extrudate characteristics,morphology, and tensile properties of acrylic rubber–blended PVC

Poly(vinyl chloride) was blended with acrylic rubber over a range of compositions (5–40 wt % of the rubber), using a twin‐screw extruder. Morphological properties of the blends were investigated as a function of rubber content and blending temperature, using a scanning electron microscopy. The mechanical properties of the blends were determined by a tensile test. Smooth extrudates were obtained at the blending temperature of 155°C. At a higher blending temperature (195°C), greater die swell ratio and/or melt‐fractured extrudates were observed, depending on the rubber content. Miscible blends were obtained at low rubber contents (5–10 wt %). A dispersed particle morphology was observed from the extrudates containing the rubber content of 20–40 wt %, at 195°C. The ultimate tensile stress (UTS) and modulus of the blends decreased with the rubber content. The maximum tensile toughness was obtained for the blend with a rubber content of 20%, at a blending temperature of 155°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2523–2534, 2001     

Development of polymer blend morphology during compounding in a twin-screw extruder. Part III: Experimental procedure and preliminary results

Currently, selection of screw configurations as well as the operating conditions for compounding polymer blends with desired morphology in a co-rotating twinscrew extruder is an art based on experience. In this paper a quenching section of a twin-screw extruder is described. The section may replace any segment of the extruder barrel. It allows, on the one hand, a regular operation of the machine, and on the other, a rapid quenching and removal of blend specimens for morphology analysis from any place along the extruder barrel and at any time of the blending. The experimental observation of development during compounding of polymer blends enables verification and improvement of the theoretical model, aimed at predicting and controlling the size and polydispersity of the minor phase. Development of the predictive model for blend morphology will provide a valuable guide to the polymer processing industry. The preliminary data were collected using polystyrene/high density polyethylene (PS/HDPE) blends at low concentration of the dispersed phase, 5 wt% of either PS or HDPE. It was observed that the viscosity ratio, blend composition, screw configuration, temperature, throughput, and screw speed significantly influence the blend morphology.