Crystallization kinetics of thermoplastic elastomeric blends based on ground tyre rubber

This work analyzes the crystallization process of thermoplastic elastomeric blends (TPE) based on ground tyre rubber (GTR). More specifically it analyzes the effect of GTR and fresh rubber materials, like ethylene propylene diene monomer (EPDM) and ethylene propylene rubber (EPR), on the crystallization of binary and ternary polypropylene (PP)‐based blends. The crystallization kinetics is studied under isothermal and nonisothermal conditions using differential scanning calorimetry (DSC). The kinetic parameters derived from the Avrami model are used to study the effect of temperature and rubber materials on the nucleation mechanism, the morphology of the crystalline structures, and the crystallization rate. Results reveal that GTR has a strong nucleating effect on PP and that its presence leads to higher crystallization rates. The EPDM presence has a slight effect on the PP crystallization process whereas EPR has no significant effect. From the DSC curves it is possible to detect an inverse relationship between temperature and the crystallization rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42589.     

Fabrication of polypropylene blends with excellent low‐temperature toughness and balanced toughness‐rigidity by a combination of EPR and SEEPS

To overcome serious rigidity depression of rubber‐toughened plastics and fabricate a rigidity‐toughness balanced thermoplastic, a combination of styrene‐[ethylene‐(ethylene‐propylene)]‐styrene block copolymer (SEEPS) and ethylene‐propylene rubber (EPR) was used to toughen polypropylene. The dynamic mechanical properties, crystallization and melting behavior, and mechanical properties of polypropylene (PP)/EPR/SEEPS blends were studied in detail. The results show that the combination of SEEPS and EPR can achieve the tremendous improvement of low‐temperature toughness without significant strength and rigidity loss. Dynamic mechanical properties and phase morphology results demonstrate that there is a good interfacial strength and increased loss of compound rubber phase comprised of EPR component and EP domain of SEEPS. Compared with PP/EPR binary blends, although neither glass transition temperature (T_g) of the rubber phase nor T_g of PP matrix in PP/EPR/SEEPS blends decreases, the brittle‐tough transition temperature (T_bd) of PP/EPR/SEEPS blends decreases, indicating that the increased interfacial interaction between PP matrix and compound rubber phase is also an effective approach to decrease T_bd of the blends so as to improve low‐temperature toughness. The balance between rigidity and toughness of PP/EPR/SEEPS blends is ascribed to the synergistic effect of EPR and SEEPS on toughening PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45714.     

Thermoplastic dynamic vulcanisates containing LDPE,rubber, and thermochemically reclaimed ground tyre rubber

Abstract

Thermochemically devulcanised ground tyre rubber (GTR^DL) was added to fresh rubber compositions, which were then melt blended with low density polyethylene (LDPE). Styrene/butadiene rubber (SBR), natural (NR), and ethylene/propylene/diene (EPDM) rubbers were selected as the fresh rubbers. During blending, dynamic curing was achieved using sulphuric, phenolic, and peroxide curing agents. Some of the GTR was decomposed in the presence of 6 phr Regen^TM Agent-S reclaiming compound before being incorporated into the blends. The resulting thermoplastic dynamic vulcanisates had constant compositions, namely LDPE/rubber/GTR=50:25:25. Sulphuric and phenolic curing agents proved to be most suitable for dynamic curing. The thermoplastic dynamic vulcanisates with the best mechanical performance contained SBR and EPDM rubbers. The observed improvements in mechanical performance were attributed to chain entanglement and co-crosslinking in the interphase between the GTR^DL particles and the surrounding matrix (i.e. with the fresh rubber and/or LDPE). The phase morphology, which was assessed using scanning electron microscopy on the etched surfaces of cryogenically fractured thermoplastic dynamic vulcanisate compositions, is discussed.     

Effects of interface reactions in compatibilised ground tyre rubber polypropylene elastomeric alloys

Abstract

Compounds of ground tyre rubber (GTR) and polypropylene (PP) were prepared in an internal mixer and characterised by means of mechanical, thermal and morphological testing. Only physical melt mixing could not provide a suitable interface compatibilisation and leads to compounds with poor mechanical properties. However, the application of a reactive melt mixing process, using organic peroxides as radical donators, was found to be suitable to initiate a compatibilisation reaction via interphase grafting. These compatibilised GTR/PP elastomeric alloy (EA) systems exhibit interesting mechanical properties which are close to that of conventional two phase thermoplastic elastomers (TPE) based on dynamically vulcanised ethylene propylene diene monomer (EPDM)/PP blends. Results of the morphology investigations substantiate the occurrence of a compatibilisation reaction between rubber particles and PP matrix during reactive mixing which is most probably responsible for the enhanced material properties of the GTR/PP EA.     

Particles versus fibrillar morphology in polyolefin ternary blends

PP/EPR binary and PP/(EPR/PE) ternary blends were prepared based on the viscosity ratio, using a corotating twin-screw extruder. Both fibrillar structures and particle-in-matrix morphologies were created depending on the viscosity ratio of rubber domain to the matrix PP (η_EPR/η_PP, or η_EPR-PE/η_PP). With fibril formation, mechanical properties of the blends, especially the flexural modulus and notched impact strength, were significantly increased and the increase was more pronounced with the ternary blends. The fibrillar morphology and filled-out particles for particle-in-matrix morphology. © 1996 John Wiley & Sons, Inc.     

高温熔融对PP/EPR/PE-UHMW分子链扩散作用以及流变和结晶性能的影响

采用一种简便易行的方法使高度缠结的超高相对分子质量聚乙烯（PE-UHMW）与乙丙橡胶（EPR）的分子链得到有效的扩散,并最终将EPR/PE-UHMW预混物与聚丙烯（PP）共混形成PP/EPR/PE-UHMW三元共混物。并研究了该三元共混物的流变性能和结晶性能。结果表明,在预混物体系中,经历高温熔融处理后,流变曲线出现不同于一般EPR材料的难松弛结构的低频平台区,说明PE-UHMW与EPR分子链相互扩散形成长分子链缠结结构;其缠结结构在PP/EPR/PE-UHMW共混物中减慢了PP基体流变曲线低频平台区出现的趋势,限制了EPR向PP基体的扩散; EPR与PE-UHMW分子链之间的相互扩散,对高度缠结的PE-UHMW具有增塑作用,导致PE-UHMW结晶温度下降和结晶度上升;二元预混物添加进入PP基体中,促使PP多重熔融现象的发生。     

Maleic anhydride grafted thermoplastic elastomer as an interfacial modifier for polypropylene/polyamide 6 blends

A maleic anhydride grafted thermoplastic elastomer (TPE_g) was prepared. The effect of the TPE_g on the morphology and performance of polypropylene (PP)/polyamide 6 (PA‐6) blends was studied. The final properties of the blends were tuned through variations in the TPE_g/PA‐6 ratios and TPE_g and PA‐6 percentages in the blends. Scanning electron micrographs showed that the TPE_g greatly improved the homogeneity of the blends, and this led to better mechanical performance. The nonisothermal crystallization behaviors of PP and PA‐6 in the blends, revealed by differential scanning calorimetry, were different from those of pure PP and PA‐6. The crystallization temperature and rate of PP were promoted by the PA‐6 component because of its nucleating effect, whereas stepwise crystallization was detected for PA‐6 in the PP/PA‐6 blends when the TPE_g was added. On the basis of these observations, a schematic model was proposed for these blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1806–1815, 2004     

Synergetic toughness and morphology of poly(propylene)/nylon 11/maleated ethylene‐propylene diene copolymer blends

Polypropylene (PP)/nylon 11/maleated ethylene‐propylene‐diene rubber (EPDM‐g‐MAH) ternary polymer blends were prepared via melt blending in a corotating twin‐screw extruder. The effect of nylon 11 and EPDM‐g‐MAH on the phase morphology and mechanical properties was investigated. Scanning electron microscopy observation revealed that there was apparent phase separation for PP/EPDM‐g‐MAH binary blends at the level of 10 wt % maleated elastomer. For the PP/nylon 11/EPDM‐g‐MAH ternary blends, the dispersed phase morphology of the maleated elastomer was hardly affected by the addition of nylon 11, whereas the reduced dispersed phase domains of nylon 11 were observed with the increasing maleated elastomer loading. Furthermore, a core‐shell structure, in which nylon 11 as a rigid core was surrounded by a soft EPDM‐g‐MAH shell, was formed in the case of 10 wt % nylon 11 and higher EPDM‐g‐MAH concentration. In general, the results of mechanical property measurement showed that the ternary blends exhibited inferior tensile strength in comparison with the PP matrix, but superior toughness. Especially low‐temperature impact strength was obtained. The toughening mechanism was discussed with reference to the phase morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on morphology of ternary polymer blends. I. Effects of melt viscosity and interfacial interaction

The morphology of some ternary blends was investigated. In all of the blends polypropylene, as the major phase, was blended with two different minor phases, ethylene–propylene–diene terpolymer (EPDM) or ethylene–propylene–rubber (EPR) as the first minor phase and high‐density polyethylene (HDPE) or polystyrene (PS) as the second minor phase. All the blends were investigated in a constant composition of 70/15/15 wt %. Theoretical models predict that the dispersed phase of a multiphase polymer blend will either form an encapsulation‐type phase morphology or phases will remain separately dispersed, depending on which morphology has the lower free energy or positive spreading coefficient. Interfacial interaction between phases was found to play a significant role in determining the type of morphology of these blend systems. A core–shell‐type morphology for HDPE encapsulated by rubber was obtained for PP/rubber/PE ternary blends, whereas PP/rubber/PS blends showed a separately dispersed type of morphology. These results were found to be in good agreement with the theoretical predictions. Steady‐state torque for each component was used to study the effect of melt viscosity ratio on the morphology of the blends. It was found that the torque ratios affect only the size of the dispersed phases and have no appreciable influence on the type of morphology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1129–1137, 2001     

Use of Monomethyl Itaconate Grafted Poly(propylene) (PP) and Ethylene Propylene Rubber (EPR) as Compatibilizers for PP/EPR Blends

The use of grafted poly(propylene) (PP) and a random copolymer of ethylene and propylene (EPR) with an itaconic acid derivative, monomethyl itaconate (MMI), as compatibilizer for PP/EPR blends was analyzed. The grafting reaction was performed at 190 °C in a Brabender Plasticorder. 2,5‐Dimethyl‐2,5‐bis(tert‐butylperoxy) hexane was the radical initiator for the functionalization of PP; dicumyl peroxide was used as the radical initiator for the modification of EPR. The obtained degree of grafting was 1.5% by weight for PP and 1.2% by weight for EPR. The compatibilizing effect of modified polymers on the processability, morphology, and mechanical and thermal properties of the blends was of interest. Compatibilization substantially improved the toughness and deformation with little effect on the tensile modulus and strength. Moreover, this effect was particularly evident when both polymeric phases were grafted. Regarding compatibilization, the viscosity of the blends increased due to the high interfacial adhesion. Morphological studies showed that the particle size of the rubbery phase was reduced and the dispersion in the matrix improved by compatibilization. The grafted polymers behaved as nucleating agents, accelerating the PP crystallization.

Change in complex viscosity with angular frequency at 180 °C for unmodified and MMI‐functionalized PP/EPR (70/30) blends.     

Study of the modification of the properties of (PP/EPR) blends with a view to preserving natural resources when elaborating new formulation and recycling polymers

The aim of the present work is to study how CaCO₃, very abundant on earth, can be blended with polypropylene/ethylene propylene rubber (PP/EPR) either to preserve natural resources when elaborating virgin formulations or to simulate mixtures of waste made of CaCO₃ filled PP with PP/EPR which could result from end-of-life-vehicles (ELV). The article focuses on the studies of PP/EPR blends, used in the manufacture of automobile fenders, in the presence of nano-CaCO₃ and compatibilizers. Blends of various compositions (with and without compatibilizer and nanoparticles) were prepared using a corotating twin-screw extruder. The results were compared with the ones presented by a commercial (PP/EPR) blend. The experiments included mechanical tests, differential scanning calorimetry, scanning electron microscopy, and dynamic mechanical analysis experiments. The presence of the compatibilizers in the (PP/EPR) blends decreases the size of elastomer particles, improves the adherence to the interface and improves the mechanical properties. The nano-CaCO₃ would also seem to act as a nucleating agent in the PP/EPR matrix; it increases the cristallinity and the Young modulus of the blends. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Reinforcement of polyolefins‐based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (PP) and ethylene propylene copolymer (EPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated‐Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO₂ systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high‐shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization‐process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties. POLYM. ENG. SCI., 55:2328–2338, 2015. © 2015 Society of Plastics Engineers     

Compatibilizers for recycling of the plastic mixture wastes. II. The effect of a compatibilizer for binary blends on the properties of ternary blends

In this article, we discuss the effect of a compatibilizer for binary blends on the properties of ternary blends composed of high‐density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS) and poly(vinyl chloride) (PVC) virgin polymers with a simulated waste plastics fraction. Chlorinated polyethylene (CPE), ethylene–propylene rubber (EPR), and their 1/1 (w/w) mixture were tested as compatibilizers for the HDPE/PP/PVC ternary blend. CPE, styrene‐ethylene‐propylene block copolymer (SEP), or their 1/1 (w/w) mixture were tested as compatibilizers for the HDPE/PS/PVC ternary blend. The composition of the ternary blends were fixed at 8/1/1 by weight ratio. The amount of the compatibilizer was 3 phr. Rheological, mechanical, and thermal properties were measured. For the 8/1/1 HDPE/PP/PVC ternary blends, the tensile strength was slightly decreased, but the impact strength was significantly increased by adding EPR, CPE, or their mixture. EPR exhibited the most significant impact modification effect for the ternary blends. In a similar way, for 8/1/1 HDPE/PS/PVC ternary blends, on adding SEP, CPE, or their mixture, the tensile strength was slightly decreased, but the impact strength was noticeably increased. It was found that the SEP worked much better as an impact modifier for the ternary blends than CPE or the SEP/CPE mixture did. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1048–1053, 2000     

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.     

Partial replacement of EPDM by GTR in thermoplastic elastomers based on PP/EPDM: Effects on morphology and mechanical properties

The formulation of recycled thermoplastic elastomeric materials (TPE) based on ground tyre rubber (GTR), generated from end of life tyres, can be an alternative strategy to deal with a type of waste responsible for increasingly environmental problems over the past decades. The incompatibility of GTR with thermoplastics places several issues on the formulation of these materials, which this study tries to overcome. An encapsulation strategy of the GTR by an elastomeric phase is proposed in this work to overcome the lack of adhesion between the materials. Ternary blends, composed of a highly flowable polypropylene homopolymer, an ethylene propylene diene monomer (EPDM) and GTR were formulated and their morphology and mechanical properties analyzed. The morphology of the blends showed interaction between the materials, revealing that the encapsulation of GTR by a rubber phase can be an adequate strategy to formulate recycled‐based TPE materials, if the dimension of the GTR particles is controlled and taken into consideration. The mechanical properties revealed the replacement effect of EPDM by GTR, and its dependence on the amount of that replacement. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40160.     

乙丙嵌段共聚物相对分子质量及链结构对PP/EPR共混体系结构与性能的影响

设计合成了一系列不同相对分子质量和乙烯平均序列长度的乙丙嵌段共聚物（EP）,并将其作为聚丙烯（PP）/二元乙丙橡胶（EPR）共混体系的增容剂,考察了EP用量、相对分子质量及乙烯平均序列长度对共混体系性能及分散相形态演变的影响。结果表明,EP增容PP/EPR体系时存在最佳添加量,少量EP的加入可有效提高PP/EPR共混体系的抗冲击性能,并对分散相尺寸及形态起到良好的调控作用;同时,EP的相对分子质量越大对共混体系的冲击性能提高越明显,EP的组成与EPR越接近,对共混体系的增容效果越明显。     

Phase structure and mechanical properties of PP/EPR/CaCO3 nanocomposites: Effect of particle's size and treatment

Calcium carbonate (CaCO₃) reinforced polypropylene/ethylene propylene rubber (PP/EPR) copolymer composites for automotive use were developed by means of extrusion and injection molding process. Three kinds of CaCO₃ (stearic acid treated and untreated) nanoparticles and microparticles were used as fillers. The influence of stearic acid, particle size, and filler content on the state distribution and morphology were investigated by SEM and rheological measurements. Two different morphologies were observed: EPR and CaCO₃ dispersed in the PP matrix and a core shell structure, depending on the interactions between EPR and CaCO₃. Toughening mechanisms and mechanical properties of the different systems were investigated. Significant improvement in tensile modulus is observed in all composites, depending on filler content. Elongation and notched impact strength were drastically decreased, especially for composites with nano CaCO₃. Better impact properties were obtained with low content of treated particles, showing the importance of filler treatment. POLYM. ENG. SCI., 55:2859–2868, 2015. © 2015 Society of Plastics Engineers     

Effect of filler partitioning on the mechanical properties of TPO/nanosilica composites

Nanosilica (SiO₂) is used as a reinforcing filler in PP/elastomer thermoplastic polyolefin (TPO) blends containing ethylene‐octene polyolefin elastomer (POE), ethylene‐propylene rubber (EPR), and maleated EPR. The localization and dispersion of the filler are controlled by adding maleated derivatives to the matrix or the dispersed phase. A separated morphology, consisting of SiO₂ residing in the PP matrix, is necessary to achieve improvements in modulus. Filled TPOs containing POE have the best performance and exhibit improved moduli while retaining high values of elongation. J. VINYL ADDIT. TECHNOL., 13:147–150, 2007. © 2007 Society of Plastics Engineers     

Effect of monomethyl itaconate‐grafted HDPE and EPR on the compatibility and properties of HDPE–EPR blends

To improve the compatibility and properties of blends based on high‐density polyethylene (HDPE) and the ethylene–propylene copolymer (EPR), the functionalization of both through grafting with an itaconic acid derivative, monomethyl itaconate (MMI), was investigated. The grafting reaction was performed at 180°C in a Brabender Plasticorder using an initial monomer concentration of 3 phr in the case of HDPE and 5 phr in the case of EPR. 2,5‐Dimethyl‐2,5‐bis(tert‐butylperoxy)hexane was used as a radical initiator for the functionalization of HDPE and dicumyl peroxide was used as a radical initiator for the modification of EPR. The degree of grafting was 1.56% by weight for HDPE and 0.8% by weight for EPR. The effect of grafting on the processability, morphology, and thermal and mechanical properties of the blends are of particular interest. The results show that the grafting reaction increases the toughness and elongation at break of all tested blends and they retained their strength and stiffness. Moreover, the grafted polymers behaved as nucleating agents, accelerating the HDPE crystallization. These results are particularly relevant when both polymeric phases are modified. Morphological studies are in concordance with the mechanical characterization, showing a reduction of the rubber particle size and a better interfacial adhesion when both polymers are functionalized with MMI. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2239–2248, 2003     

Tensile elongation of high‐fluid polypropylene/ethylene–propylene rubber blends: Dependence on molecular weight of the components and propylene content of the rubber

We studied tensile behavior of low‐molecular‐weight (MW) polypropylene (PP)/ethylene–propylene rubber (EPR; 70/30) blends from the viewpoint of the MWs of PP and EPR and the compatibility between PP and EPR. The value of the melt flow rate of PP varied from 30 to 700 g/10 min at 230°C. We studied the compatibility between PP and EPR by varying the propylene content in EPR (27 and 68 wt %). At the initial elongation stage, crazes were observed in all blends. When blends included EPR with 27 wt % propylene, the elongation at break of the low‐MW PP improved little. The blends with EPR and 68 wt % propylene content were elongated further beyond their yielding points. The elongation to rupture was increased with increasing MW of EPR. Molecular orientation of the low‐MW PP was manifested by IR dichroism measurements and X‐ray diffraction patterns. The blends of low‐MW PP and EPR could be elongated by the partial dissolution of EPR of high‐MW in the PP amorphous phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 46–56, 2002