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     

废弃交联PE的力化学再生及其与PE-HD共混物性能的研究

采用固相力化学技术,实现了交联聚乙烯电缆料（XLPE）的力化学回收。结果表明：固相力化学方法是实现XLPE热塑性加工的有效手段,经力化学处理后,再生XLPE的拉伸强度为13.7 MPa,断裂伸长率为383 ％。XLPE经力化学处理后表观黏度下降,加工流动性显著改善。将力化学处理的XLPE与高密度聚乙烯(PE-HD)共混,加工性能进一步得到改善,XLPE/PE-HD共混材料的拉伸强度和断裂伸长率分别达到18.5 MPa和500 %。XLPE/PE-HD共混物的SEM断面形貌分析表明,力化学处理可有效改善共混体系中XLPE和PE-HD的相容性。     

Rheological,mechanical and morphological properties of thermoplastic vulcanizates based on high impact polystyrene and styrene‐butadiene rubber

Thermoplastic vulcanizates (TPVs) based on high impact polystyrene (HIPS)/styrene‐butadiene rubber (SBR) blends were prepared by dynamic vulcanization technique. The rheological, mechanical and morphological properties of the dynamically vulcanized blends were investigated systematically. As determined by capillary rheometer, the apparent viscosity of the blends decreases as the shear rate increases, indicating obvious pseudoplastic behavior. At low shear rate, the apparent viscosity of these blends is considerably higher than that of neat HIPS and decreases with the increase of HIPS concentration. The increase of HIPS content in the dynamically vulcanized blends contributes to the increase of tensile strength and hardness properties, while elongation at break and tensile set at break reach a maximum at 30 and 50 wt % of the HIPS content, respectively. The etched surfaces of the HIPS/SBR TPVs were investigated using field‐emission scanning electron microscopy, the morphological study reveals continuous HIPS phase and finely dispersed SBR elastomeric phase in the TPVs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

EPDM/POE动态硫化热塑性硫化胶的性能与结构

采用动态硫化法制备EPDM/聚烯烃弹性体(POE)热塑性硫化胶(TPV),研究共混温度和硫化体系配比对其性能的影响,并对其形态结构进行表征.结果表明:随着共混温度的升高和硫化体系用量的增大,共混体系的硫化速率逐渐加快;TPV的拉伸强度和拉断伸长率在共混温度为150℃左右时达到最大,拉断伸长率随着硫化体系用量的增大而减小,而拉伸强度则先减小后略有增大;随着共混温度的升高和硫化体系用量的增大,TPV撕裂强度呈现先增大后减小趋势;当硫黄用量为0.2份时,体系出现了明显的Payne效应,EPDM交联相以平均粒径为1μm左右的颗粒状态分散于POE连续相中.     

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%.     

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     

Enhancement of processability and foamability of ground tire rubber powder and LDPE blends through solid state shear milling

The foamed composites made from low-density polyethylene(LDPE) and ground tire rubber(GTR) powder using azodicarbonamide as chemical blowing agent have been investigated. Solid state shear milling was used to enhance the processability and foamability of LDPE/GTR blends by a pan-mill type mechanochemical reactor. First the blends of LDPE/GTR were prepared by co-milling, then the samples were melt-mixed in a Brabender Plasti-Corder, saturated with blowing agent, crosslinking agent and blowing co-agent, and finally the saturated specimens were expanded during the pressure-quench process. The results indicated that the mechanical properties of the LDPE/GRT foamed composites were improved, and the blends of co-milled GTR and LDPE powder showing better processability and foamability than those obtained in a conventional melt-mixing manner, as indicated by the rheological and morphological studies.     

二段硫化的均聚型/共聚型氯醚共混胶的性能

研究了二段硫化对均聚型(CO)／共聚型(ECO)氯醚共混胶的力学性能以及高温压缩永久变形的影响：结果表明，采用NA-22硫化体系硫化的CO／ECO共混胶，在合适的二段硫化条件下，可增加硫化胶的拉伸强度，但降低了其扯断伸长认；而采用TCY硫化的共混胶．二段硫化后，硫化胶的拉伸强度基本不变，扯断伸长率减小，二段硫化能明显减少CO／ECO共混胶的高温压缩永久变形，而且在一定范围内．二段硫化时间的延长有利于减少硫化胶的高温压缩永久变形。     

Morphology and mechanical properties of ethylene‐vinyl acetate rubber/polyamide thermoplastic elastomers

High performance thermoplastic elastomers based on ethylene‐vinyl acetate rubber (EVM) and ternary polyamide copolymer (tPA) were prepared through a dynamic vulcanization process in the presence of dicumyl peroxide (DCP). The morphology, crystallization, and mechanical properties of the EVM/tPA blends were studied. A phase transition of EVM/tPA blend was observed at a weight ratio of 60/40. The presence of EVM increased the melting enthalpy at the high temperature of tPA, ascribing to the heterogeneous nucleating effect of EVM. The tensile strength of EVM/tPA (70/30) blends was increased up to 20.5 MPa as the DCP concentration increased to 3.5 phr, whereas the elongation at break of the blends kept decreasing as the DCP concentration increased. The addition of ethylene‐acrylic acid copolymer (EAA) or maleic anhydride‐grafted EVM (EVM‐g‐MAH) to the EVM/tPA blends both induced finer dispersion of the EVM particles in the tPA phase and improvement in the tensile strength and elongation at break of the blends, which were ascribed to the compatibilization of EAA or EVM‐g‐MAH. Finally, a high performance EVM/tPA (70/30) thermoplastic elastomer with Shore A hardness of 75, tensile strength of 24 MPa, elongation at break of 361%, and set at break of 20% was obtained by adding 5 wt % of EVM‐g‐MAH and 3.5 phr DCP. It has great potential in automotive and oil pipeline applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphological and structural development of recycled crosslinked polyethylene during solid‐state mechanochemical milling

Waste crosslinked polyethylene (XLPE) was partially decrosslinked to obtain a thermoplastic recycled material through solid‐state mechanochemical milling with pan‐mill equipment at ambient temperature. The gel fraction and size exclusion chromatography measurements showed that the gel content of XLPE decreased remarkably with increasing cycles of mechanochemical milling, whereas the molecular weight of the sol fraction was not significantly reduced; this indicated the realization of partial decrosslinking during mechanochemical milling. Differential scanning calorimetry and X‐ray diffraction analysis showed that the melting temperature of decrosslinked polyethylene increased by 3.5°C because the bigger crystallites size resulting from the higher mobility of the chain segment. The improved thermoplastic characteristic of XLPE after mechanochemical milling were confirmed by scanning electron microscopy and rheological measurement. The mechanical properties of recycled XLPE also achieved significant improvement after mechanochemical milling. Solid‐state mechanochemical milling is a cost‐effective, reliable, and environmentally friendly method for recycling XLPE at ambient temperature without any additional materials or chemicals. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structures and properties of waste silicone cross‐linked polyethylene de‐cross‐linked selectively by solid‐state shear mechanochemical technology

Waste silicone cross‐linked polyethylene (Si‐XLPE) recycling effectively by using solid‐state shear mechanochemical (S³M) technology was investigated to make the better performance thermoplastic polyethylene. To make this thermoplastic material, the cross‐linked structures of waste Si‐XLPE that was consisted of the siloxane bonds must be de‐cross‐linked selectively instead of the destruction of the material main chains. The properties of recycled Si‐XLPE materials were investigated by gel fraction measurements, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter, torque rheological measurements, scanning electron microscope (SEM) and thermogravimetric analyzer (TG). From the results, it could be seen that the cross‐linking bonds of the Si‐XLPE were destroyed selectively by S³M technology and the mechanochemical milling also played a significant role in improving the materials process‐ability and mechanical properties. Gel fraction measurements, GPC and FTIR showed that S³M technology could interrupt the cross‐linked structures of Si‐XLPE rather than the backbone chains by initiating the de‐cross‐linking reaction obviously; Torque rheological results further confirmed that the recycled Si‐XLPE materials gained better plastic characteristics and process‐ability after mechanochemical milling. Compared with the untreated Si‐XLPE, the tensile strength and elongation at break of Si‐XLPE samples after 10 cycles milling increased by 118.4% and 330.4%, respectively. J. VINYL ADDIT. TECHNOL., 25:149–158, 2019. © 2018 Society of Plastics Engineers     

Effect of interfacial enhancing on morphology,mechanical, and rheological properties of polypropylene‐ground tire rubber powder blends

In this work, polypropylene (PP)‐ground tire rubber (GTR) blends are prepared by means of melt‐extrusion process using a co‐rotating twin screw extruder. The influences of types of compatibilizers and crosslinkers on the interfacial interaction state, mechanical and rheological properties of PP‐GTR blends are investigated systematically. Particularly, quantitative nano mechanic technique of atom force microscope was employed to examine the change in thickness of the interfacial transition layer between PP and GTR phase with variety of compatibilizer and crosslinker types. Results indicated that styrene‐b‐poly(ethylene‐ethylene/propylene)‐b‐polystyrene (SEEPS) and peroxide are optimal compatibilizer and crosslinker for interfacial interaction enhancement, respectively. The resultant PP‐GTR blend possesses tensile strength of 14.5 MPa, elongation at break of 307%, and permanent set of 16%. It was expected that reaction activities of the crosslinker with GTR and SEEPS would have a significant influence on the agglomeration of GTR particles and the interaction between PP and GTR phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45354.     

Effect of butyl rubber type on properties of polyamide and butyl rubber blends

Polyamide‐12 was blended with butyl rubber, bromobutyl rubber, and chlorobutyl rubber with and without a sulfur curing system. Mechanical properties for dynamically vulcanized blends generally exceed those made with no vulcanization. Chlorobutyl‐containing blends prepared by dynamic vulcanization have higher tensile strength and elongation at break values in comparison to those made from other butyl rubbers. For a variety of polyamide/rubber blends made by dynamic vulcanization, there is very little effect of rubber percentage unsaturation and Mooney viscosity on the mechanical properties of the blends. In chlorobutyl‐containing blends prepared by dynamic vulcanization, the swelling index values attributed to the rubber portion decrease as rubber content decreases, and it is likely that the polyamide phase completely surrounds the rubber particles at compositions exceeding approximately 25% polyamide. Swelling index results can be correlated with elongation at break values for similar blends. The results of differential scanning calorimetry suggest that the polyamide phase is not a neutral component in high shear mixing with butyl rubbers with or without curing agents. Rheological studies indicate strong non‐Newtonian behavior for all blends of polyamide‐12 with butyl rubbers. Scanning electron microscopy on polyamide‐12/butyl rubber blends indicates compatibility for butyl rubbers in the order of chlorobutyl > bromobutyl > butyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1423–1435, 2004     

共改性煤粉增强丁苯橡胶的硫化、力学和热稳定性能研究

将硅烷偶联剂KH⁃560和硫化促进剂CZ共改性煤粉（Coal）作为增强填料加入到丁苯橡胶（SBR）中制备改性SBR/ Coal复合材料,通过设置不同的共改性Coal的添加量,寻找KH⁃560、CZ共改性Coal增强丁苯橡胶的最佳实验配比。结果表明,KH⁃560的最佳添加量为Coal质量的5 %,此时SBR/ Coal⁃KH560复合材料的力学性能最佳; KH⁃560和CZ改性Coal可以明显减少Coal团聚现象,在丁苯橡胶中均匀分散。当Coal⁃KH560⁃CZ添加量为40 %时,与纯SBR相比,拉伸强度由1.66 MPa升高至2.9 MPa,断裂伸长率由295 %升高至390 %,撕裂强度由7.1 N/mm增加至11.6 N/mm,复合材料的力学性能和热稳定性能得到改善,加工性能也得到较大提升。     

Effects of Dynamic Vulcanization and Acrylic Acid on Properties of Recycled Poly(vinyl chloride)/Acrylonitrile Butadiene Rubber (PVCr/NBR) Blends

Effects of dynamic vulcanization and acrylic acid (AAc) on processability, mechanical properties, swelling behavior, morphology, and thermal stability of recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were investigated. Blends were prepared in a Haake Rheomix at a temperature of 150°C and a rotor speed of 50 rpm. Recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were also prepared as comparison. It was found that the dynamic vulcanization and the addition of acrylic acid improved the stabilization torque, mechanical energy, stress at peak, stress at 100% elongation (M₁₀₀), swelling resistance, and thermal stability but decreased the elongation at break of the blends. The introduction of a cross-link into the elastomer phase and better compatibility between PVCr and NBR are responsible for the enhancement of thermal stability and mechanical properties of dynamically vulcanized PVCr/NBR + AAc as evidence from the scanning electron microscopy (SEM) of the tensile fracture surfaces and infrared spectroscopy study of the dynamically vulcanized of PVCr/NBR + AAc shows.     

Mechanical properties of thermoplastic elastomers based on silicone rubber and an ethylene–octene copolymer by dynamic vulcanization

Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers that are generally produced by the simultaneous mixing and crosslinking of a rubber with a thermoplastic polymer at an elevated temperature. Novel peroxide‐cured TPVs based on blends of silicone rubber and the thermoplastic Engage (an ethylene–octene copolymer) have been developed. These TPVs exhibit very good overall mechanical and electrical properties. With an increasing concentration of dicumyl peroxide, the tensile strength, modulus, and hardness of the TPVs increase, whereas the elongation at break decreases. Significant correlations have been obtained from oscillating disc rheometer torque values with various physical properties, such as the modulus and tension set of the TPVs. The aging characteristics and recyclability of the silicone‐based TPVs are also excellent. Scanning electron microscopy photomicrographs of the TPVs have confirmed a dispersed phase morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermoplastic vulcanizates based on epoxidized natural rubber/polypropylene blends: Effect of compatibilizers and reactive blending

Epoxidized natural rubber (ENR) was prepared using the performic epoxidation method. TPVs based on ENR/PP blends were later prepared by melt‐mixing processes via dynamic vulcanization. The effects of blend ratios of ENR/PP, types of compatibilizers, and reactive blending were investigated. Phenolic modified polypropylene (Ph‐PP) and graft copolymer of maleic anhydride on polypropylene molecules (PP‐g‐MA) were prepared and used as blend compatibilizers and reactive blending components of ENR/Ph‐PP and ENR/PP‐g‐MA blends. It was found that the mixing torque, apparent shear stress and apparent shear viscosity increased with increasing levels of ENR. This is attributed to the higher viscosity of the pure ENR than that of the pure PP. Furthermore, there was a higher compatibilizing effect because of the chemical interaction between the polar groups in ENR and PP‐g‐MA or Ph‐PP. Mixing torque, shear flow properties (i.e., shear stress and shear viscosity) and mechanical properties (i.e., tensile strength, elongation at break, and hardness) of the TPVs prepared by reactive blending of ENR/Ph‐PP and ENR/PP‐g‐MA were lower than that of the samples without a compatibilizer. However, the TPVs prepared using Ph‐PP and PP‐g‐MA as compatibilizers exhibited higher values. We observed that the TPVs prepared from ENR/PP with Ph‐PP as a compatibilizer gave the highest rheological and mechanical properties, while the reactive blending of ENR/PP exhibited the lowest values. Trend of the properties corresponds to the morphology of the TPVs. That is, the TPV with Ph‐PP as a blend compatibilizer showed the smallest rubber particles dispersed in the PP matrix, while the reactive blending of ENR/PP‐g‐MA showed the largest particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4729–4740, 2006     

纳米SiO2对动态硫化EPDM/PP热塑性硫化胶性能的影响

采用不同硫化体系动态硫化制备三元乙丙橡胶/聚丙烯热塑性硫化胶(EPDM/PP TPVs),并在制备的过程添加不同量的纳米SiO2。结果表明酚醛树脂2402动态硫化得到的EPDM/PP TPVs性能最佳。随着纳米SiO2添加量的增加,EPDM橡胶粒子的粒径先减小后增大,当纳米SiO2的添加量为10份时,EPDM橡胶粒子的粒径达到最小。流变性能研究表明添加纳米SiO2使EPDM/PP TPVs的加工性能变差。动态机械分析仪(DMA)研究表明纳米SiO2提高了TPVs中PP相的玻璃化转变温度。当纳米SiO2的添加量为10份,TPVs的拉伸强度达到最高为23.7MPa,提高了19.1%,断裂伸长率达到最大为431%,提高了11.1%。纳米SiO2使EPDM/PP TPVs的热稳定性和耐热老化性能变好。     

Thermoplastic vulcanizates based on epoxidized natural rubber/polypropylene blends: Effect of epoxide levels in ENR molecules

Epoxidized natural rubbers (ENR) with various levels of epoxide groups were prepared. Thermoplastic vulcanizates based on 75/25 ENRs/PP blends with Ph‐PP compatibilizer were later prepared by dynamic vulcanization using sulfur curing system. Influence of various levels of epoxide groups on rheological, mechanical morphological properties, and swelling resistance of the TPVs was investigated. It was found that the mixing torque, apparent shear stress, apparent shear viscosity, tensile strength, and hardness properties increased with increasing levels of epoxide groups in the ENR molecules. This may be attributed to increasing level of chemical interaction between the methylol groups of the Ph‐PP molecules and polar functional groups of the ENR molecules. Also, the PP segments in the Ph‐PP molecules are capable of compatibilizing with the PP molecules used as a blend composition. In SEM micrographs, we observed finer dispersion of vulcanized rubber domains as increasing levels of epoxide contents. This corresponds to increasing trend of strength and hardness properties of the TPVs. An increasing trend of tension set and a decreasing trend of elongation at break were observed as increasing levels of epoxide groups in the ENR molecules. This is because of higher rigidity of the vulcanized ENR phase with higher epoxide groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3046–3052, 2006     

三螺杆动态混炼挤出机制备TPV的力学性能研究

在振动力场作用下的三螺杆动态混炼挤出机上,采用硫磺硫化体系对不同配比EPDM／PP共混物进行动态硫化实验。通过调节螺杆振动参数(频率和振幅)改变加工过程中振动力场的振动强度,探讨了振动力场对 EPDM／PP共混物力学性能的影响规律。结果表明:振动力场的引入可以使热塑性硫化体系(TPV)拉伸强度最大提高23％,100％定伸应力最大提高20％,断裂伸长率最大提高28．7％;而振动力场的施加使得TPV材料的永久变形增大,说明其弹性下降,另外对硬度影响不大。