Dynamically vulcanized blends of polypropylene and ethylene‐octene copolymer: Comparison of different peroxides on mechanical,thermal, and morphological characteristics

Thermoplastic vulcanizates (TPVs) are prepared by the dynamic vulcanization process, where crosslinking of an elastomer takes place during its melt mixing with a thermoplastic polymer under high shear. TPVs based on polypropylene (PP) with different grades of ethylene‐octene copolymers (EOC) were prepared with a coagent assisted peroxide crosslinking system. The effect of dynamic vulcanization and influence of various types and concentrations of peroxide were mainly studied on the basis of the mechanical, thermal, and morphological characteristics. Three structurally different peroxides, namely dicumyl peroxide (DCP), tert‐butyl cumyl peroxide (TBCP), and di‐tert‐butyl peroxy isopropyl benzene (DTBPIB) were investigated. The mechanical properties of the TPVs are primarily determined by the extent of crosslinking in the EOC and the degree of degradation in the PP phase. Among all peroxides used DCP gives best overall properties with low‐molecular‐weight EOC, whereas TBCP shows best property level with high‐molecular‐weight EOC‐based TPVs. These can be explained on the basis of the molecular characteristics of EOC and the nature of the peroxide used. Differential scanning calorimetery (DSC) and morphological analysis reveal that PP and EOC are a thermodynamically immiscible system. The melting endotherm was studied to determine the influence of various peroxides on crystallinity of the PP phase. Tensile fracture patterns were also analyzed to study the failure mechanism of the samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamically vulcanized PP/EPDM blends by multifunctional peroxides: Characterization with various analytical techniques

The characterization of peroxide‐cured PP/EPDM TPVs using various spectroscopic techniques is difficult. These techniques are most suited for analysis of solutions, while the PP‐phase does not dissolve in common organic solvents at room temperature. To obtain more insight into the chemistry and reactivity involved between the multifunctional peroxides and EPDM rubber, several characterization techniques were employed. In the present investigation, FTIR, GC‐(FID + MS), HP‐SEC, and element analysis were used to characterize the multifunctional peroxides TBIB and DTBT, before and after the dynamic curing of the EPDM phase. The decomposition products obtained from these multifunctional peroxides are most likely grafted onto the EPDM‐rubber, thereby reducing their volatility and avoiding the common unpleasant smell. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1393–1403, 2005     

NR/PP thermoplastic vulcanizates: Selection of optimal peroxide type and concentration in relation to mixing conditions

Thermoplastic vulcanizates (TPVs) from natural rubber (NR) and polypropylene (PP) were studied, prepared by dynamic vulcanization during melt mixing, using various peroxides to crosslink the rubber phase. The objective was to find a proper balance between degree of crosslinking of the rubber and degradation of the PP‐phase, and the tendency of the peroxide to form smelly by‐products, in particular acetophenone. Four types of peroxides were investigated: 2,5‐dimethyl‐2,5‐di(tert‐butyl‐peroxy) hexyne‐3 (DTBPHY), 2,5‐dimethyl‐2,5‐di(tert‐butyl‐peroxy) hexane (DTBPH), di(tert‐butylperoxyisopropyl) benzene (DTBPIB), and dicumyl peroxide (DCP), at two mixing temperatures: 160 and 180°C for a 60/40 NR/PP TPV. The maximum and final mixing torques are clearly related to the intrinsic decomposition temperature of the particular peroxide used, where DCP and DTBPIB turn out to be effective at 160°C, whereas the other two require a higher temperature of 180°C. The best mechanical properties, tensile strength, elongation at break and compression set are obtained at lower mixing temperature with DCP and DTBPIB, presumably due to less degradation of the NR and PP. Unfortunately, these two peroxides form more smelly by‐products than DTBPHY and DTBPH. Dependent on the requirements of the pertinent application, a balanced selection needs to be made between the various factors involved to obtain an optimal product performance of these NR/PP TPVs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dynamically vulcanized blends of polypropylene and ethylene octene copolymer: Influence of various coagents on mechanical and morphological characteristics

Dynamically cured blends of polypropylene (PP) and ethylene octene copolymer (EOC) with coagent‐assisted peroxide curative system were prepared by melt‐mixing method. It was well established that PP exhibits β‐chain scission in the presence of peroxide. Principally, incorporation of a coagent increases the crosslinking efficiency in the EOC phase and decreases the extent of degradation in the PP phase. The present study mainly focused on the influence of three structurally different coagents, namely, triallyl cyanurate (TAC), trimethylol propane triacrylate (TMPTA), and N,N′‐m‐phenylene dimaleimide (MPDM), on the mechanical properties of the PP/EOC thermoplastic vulcanizates (TPVs). The reactivity and efficiency of different coagents were characterized by cure study on EOC gum vulcanizate. TAC showed the highest torque values followed by MPDM and TMPTA. Significant improvements in the physical properties of the TPVs were inferred with the addition of coagents. Among the three coagents used, MPDM showed the best balance of mechanical properties in these TPVs. The results indicated that torque values obtained during mixing and the final mechanical properties can be correlated. Different aspects were explained for the selection of a coagent that forms a product with desired properties. The phase morphologies of the TPVs prepared were studied by scanning electron microscopy. Tensile fracture patterns were also analyzed to study the failure mechanism of the samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Dynamically vulcanized polypropylene/styrene–butadiene rubber blends: The effect of a peroxide/bismaleimide curing system and composition

Polypropylene (PP)/styrene–butadiene rubber blends were studied with special attention given to the effects of the blend ratio and dynamic vulcanization. Dicumyl peroxide (DCP) was used as the curing agent in combination with N,N′‐m‐phenylene bismaleimide (BMI) as the coagent for the curing process. Outstanding mechanical performance, especially with regard to the elongation at break, and better resistance to compression set were achieved with the dynamic vulcanization; this indicated that the DCP/BMI system also acted as a compatibilizing agent. This phenomenon was also confirmed by Fourier transform infrared spectroscopy of the insoluble material, the crystallinity degree of the PP phase (as investigated by X‐ray diffractometry), and scanning electron microscopy. The dynamic mechanical properties of the nonvulcanized and vulcanized blends were also investigated. The aging resistance of the blends was also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical,vulcametric, and thermal properties of the different 5‐ethylidene 2‐norbornene content of ethylene‐propylene‐diene‐monomer vulcanized with different types and compositions of peroxides

Ethylene‐propylene‐diene‐monomer (EPDM) rubber is an important commercial polymer. The vulcanization process significantly changes its thermal, mechanical, and vulcametric properties. This study was carried out to find optimum formulation of EPDM composite for a better application in automotive industry. Sixteen EPDM polymer samples having different 5‐ethylidene 2‐norbornene (ENB) and ethylene contents were vulcanized with different types and compositions of peroxide and coagents. The mechanical and vulcametric properties of these samples were measured and compared. The type of peroxide, coagent, and EPDM grade affected the mechanical, thermal, and vulcametric properties of the EPDM rubber to some extend. Use of aromatic peroxide and coagent increased the thermal stability slightly. Mechanical properties were changed very slightly with the change of peroxide type for the same content of peroxide and coagent. Scorch time and cure time decreased with initial increase of the peroxide content. EPDM compound vulcanized with BBPIB peroxide and TAC/S coagent has higher cure time than EPDM compound vulcanized with DMBPHa peroxide and TMPTMA coagent. Coran method was used for the modeling of experimental data. Velocity constant for the formation of peroxide radical and polymer radical were found for each case. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Synergistic effect of SBS and trimethylopropane trimethacrylate (TMPTMA) on dynamically vulcanized SEBS/PP blends

The SEBS/PP thermoplastic vulcanizates (TPVs) were prepared by melt blending. Di‐tert‐butyl peroxide (DTBP) was used as the curing agent in combination with trimethylopropane trimethacrylate (TMPTMA) and poly(styrene‐b‐butadiene‐bstyrene) (SBS) as the coagents for the curing process. The synergistic effect of TMPTMA and SBS on the structure and properties of TPVs was studied by means of FT‐IR, DSC, torque rheometer, and universal testing machine. Both SEBS and PP crosslinked and the network structure formed under the participation of TMPTMA and SBS. Compared with the sole addition of the coagent, simultaneous loading of both TMPTMA and SBS could provide the TPVs with better solvent‐resistance and excellent mechanical properties. The crosslinking mechanism of the TPVs was also proposed. The slight lower value of T_m for the TPVs indicated the improved miscibility between PP and SEBS due to the crosslinking reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44392.     

Effect of different types of peroxides on properties of vulcanized EPDM + PP blends

Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene‐propylene‐diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678–1691, 2010. © 2010 Society of Plastics Engineers.     

Systematic investigation on the effect of crosslinking agent type and dosage on the performance of TPU/MVQ based thermoplastic vulcanizates

Dynamic vulcanized thermoplastic polyurethane (TPU)/methyl vinyl silicone rubber (MVQ) thermoplastic vulcanizates (TPVs) were prepared in torque rheometer. The influence of the type and amount of peroxide crosslinking agent on the mechanical properties, thermal stability, micromorphology and melt flowability was systematically investigated. The results showed that the mechanical properties of the TPVs vulcanized by 2,5-dimethyl-2,5-di (tert-butyl peroxy) hexane (DBPH) first increased and then decreased with increasing the peroxide amount, while for dicumyl peroxide (DCP) vulcanizing system the mechanical properties slowly increased. Besides, the comprehensive mechanical properties vulcanized by DBPH were better than those of DCP group. The results of the thermogravimetric analysis showed that the TPVs vulcanized by DBPH had better heat stability, corresponding to the excellent thermo-oxidative aging performance and the 38% increase in tensile strength after aging. In addition, the MVQ rubber particles showed better dispersing performance for DBPH vulcanizing system. The melt flow rate of the TPVs showed a linear relationship with increasing DBPH dosage and became worse after the amount of crosslinking agent exceeded 1.5 phr. By comprehensive comparison, the TPVs have better performance when use peroxide DBPH as the crosslinking agent and the dosage is 1.5 phr.     

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.     

Influence of oil contents in dynamically cured natural rubber and polypropylene blends

Mechanical, dynamic, thermal, and morphological properties of dynamically cured 60/40 NR/PP TPVs with various loading levels of paraffinic oil were investigated. It was found that stiffness, hardness, tensile strength, storage shear modulus, complex viscosity, glass transition temperature (T_g) of the vulcanized rubber phase, degree of crystallinity and crystalline melting temperature (T_m) of the polypropylene (PP) phase decreased with increasing loading levels of oil. This is attributed to distribution of oil into the PP and vulcanized rubber domains causing oil‐swollen amorphous phase and vulcanized rubber domains. An increasing trend of elastic response in terms of tension set and damping factor was observed in the TPVs with loading levels of oil in a range of 0–20 phr. It is supposed that a major proportion of oil was first preferably migrated into the PP phase and caused an abrupt decreasing trend of degree of crystallinity and T_m of the PP phase. The dispersed vulcanized rubber domains remained small as particles with a low degree of swelling. Increasing loading levels of oil higher than 20 phr caused a decreasing trend of elongation at break and elastomeric properties. Saturation of oil in the PP phase was expected and the excess oil was transferred to the rubber phase which thereafter caused larger swollen vulcanized rubber domains. The remaining amount of oil was able to separate as submicron pools distributed in the PP matrix. This caused lowering of T_g, T_m, crystallinity of PP phase as well as strength, elastomeric, and dynamic properties of the TPVs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dynamically vulcanized blends of polypropylene and ethylene octene copolymer: Influence of various coagents on thermal and rheological characteristics

The present study focuses on the influence of the three structurally different coagents, namely triallyl cyanurate (TAC), trimethylol propane triacrylate (TMPTA) and N,N′‐m‐phenylene dimaleimide (MPDM) on the thermal and rheological properties of thermoplastic vulcanizates (TPVs) based on the polypropylene (PP) and ethylene octene copolymer (EOC). Depending on the structure and reactivity, different coagents show different behaviors. All the TPV compositions were made by melt mixing method in a Haake Rheomix at 180°C. Rheological properties have also been evaluated at the same temperature. Viscoelastic properties of the TPVs were analyzed by a dynamic oscillatory rheometer in the melt state in a Rubber Process Analyzer (RPA 2000). Morphologically, TPVs consist of dense crosslinked rubber domains dispersed in a continuous thermoplastic matrix. The crosslinked rubber particles have a tendency to form agglomerates and build local clusters which undergo disintegration by shearing. A variety of rheological characteristics such as Payne effect, shear rate sensitivity, modulus recovery and dynamics of relaxation were studied by performing strain sweep, frequency sweep and stress relaxation tests. Among the various coagents taken for investigation, MPDM‐based TPVs show improved dynamic functions (complex modulus and complex viscosity) and lower rate of stress relaxation over TAC, TMPTA and the control sample without any coagent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influences of blend proportions and curing systems on dynamic,mechanical, and morphological properties of dynamically cured epoxidized natural rubber/high‐density polyethylene blends

Thermoplastic elastomers (TPEs) based on dynamically cured epoxidized natural rubber/high‐density polyethylene (ENR/HDPE) blends were prepared. Influence of the process oil, blend proportion, and curing systems were investigated. It was found that the oil‐extended thermoplastic vulcanizates (TPVs) exhibited better elastomeric properties and improved ease of the injection process. Increasing the proportion of ENR caused increasing elastic response of elongation at break, tension set properties, and tan δ. It was also found that the TPV treated with phenolic resin exhibited superior mechanical properties and the smallest vulcanized rubber domains. The TPV treated with the conventional peroxide co‐agent curing system showed superior strength properties but had poor elastomeric properties. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Thermoplastic vulcanizates based on poly(methyl methacrylate)/epoxidized natural rubber blends: Mechanical,thermal, and morphological properties

Epoxidized natural rubbers (ENRs) with epoxide levels of 10, 20, 30, 40 and 50 mol % were prepared. The ENRs were later used to prepare thermoplastic vulcanizates (TPVs) by blending them with poly(methyl methacrylate) (PMMA) using various formulations. Dynamic vulcanization, using sulfur as a vulcanizing agent, was performed during the mixing process. The mixing torque increased as the ENR contents and epoxide molar percentage increased. This was because of an increasing chemical interaction between the polar groups of the blend components, particularly at the interface between the elastomeric and thermoplastic phases. The ultimate tensile strength of the TPVs with ENR‐20 was high because of strain‐induced crystallization. ENRs with epoxide levels >30 mol % exhibited an increase of tensile strength because of increasing levels of chemical interaction between the molecules and the different phases. The hardness of the TPVs also increased with increased epoxide levels but decreased with increased contents of ENRs. Two morphology phases with small domains of vulcanized ENR particles dispersed in the PMMA matrix were observed from scanning electron microscopy micrographs. The TPVs based on ENR‐20 and ENR‐50 showed smaller dispersed rubber domains than those of the other types of ENRs. Furthermore, the size of the vulcanized rubber domain decreased with increasing amounts of PMMA in the blends. The decomposition temperature of the TPVs also increased as both the levels of ENRs in the blends and the epoxide molar percentage increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1251–1261, 2005     

Effect of different curing systems on heat shrinkability and mechanical properties of ethylene vinyl acetate/epoxidized natural rubber blends

Ethylene vinyl acetate (EVA)/epoxidized natural rubber (ENR) blends containing 10 and 30 wt % ENR were prepared by using an internal mixer. Five different types of curing systems were employed: dicumyl peroxide (DCP), sulfur (S), phenolic resin (Ph), DCP + S, and DCP + Ph. DCP could crosslink with both EVA and ENR while S and Ph were curing agents for ENR. The DCP system provided the lowest tensile properties and tear strength because of low crosslinking in ENR phase. Addition of sulfur or phenolic resin increased the mechanical properties due to a better vulcanization of the rubber phase. The mechanical properties of the blends decreased with increasing ENR content. The rubber particle size in the blends containing 30% ENR played a more important role in the mechanical properties than the blends containing 10% ENR. ENR particle size did not affect heat shrinkability of EVA and a well vulcanized rubber phase was not required for high heat shrinkage. Furthermore, heat shrinkage of the blends slightly changed as the ENR content increased for all curing systems. With regard to the mechanical properties and heat shrinkability, the most appropriate curing system was DCP + Ph and in the case the 10 wt % ENR content produced a more favorable blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Exploring a novel cyclic monofunctional peroxide for curing of silicone rubber at elevated temperature

The curing characteristics of silicone rubber (polydimethylsiloxane [PDMS]) in the presence of structurally different peroxides, namely dicumyl peroxide (DCP) and 3,3,5,7,7‐pentamethyl‐1,2,4‐trioxepane (PMTO), have been studied in details. At moderate temperature, DCP is more prominent for curing the silicone rubber but at high temperatures it suffers from low scorch safety. An inhibitor 2,2,6,6‐tetramethylpiperidinyloxyl (TEMPO) was added with DCP to stabilize the radicals in order to increase the scorch safety time. On the other hand, PMTO showed a prolonged scorch safety and better crosslinking efficiency rather than (DCP + TEMPO) mix at higher temperatures. PMTO‐crosslinked PDMS shows better crosslinking efficiency as indicated by a higher gel content and low swelling index value. Also the mechanical properties, thermal stability, and dynamic mechanical behavior of PMTO‐crosslinked PDMS are much superior than (DCP + TEMPO)‐crosslinked PDMS. Apart from thermoplastic vulcanizates (TPVs) made from PMTO‐crosslinked PDMS show better physicomechanical behavior compared to the TPVs made from (DCP + TEMPO)‐crosslinked PDMS. Moreover, DCP undergoes decomposition reactions at a higher temperature and forms acetophenone, which leads to an unpleasant smell in the final products whereas no such phenomenon is observed for PMTO. Therefore, PMTO turns out to be the suitable peroxide for crosslinking of PDMS at higher temperature. POLYM. ENG. SCI., 57:1073–1082, 2017. © 2016 Society of Plastics Engineers     

Effects of peroxide and gamma radiation on properties of devulcanized rubber/polypropylene/ethylene propylene diene monomer formulation

Mechanical and thermal properties of devulcanized rubber (DR)/polypropylene (PP)/ethylene propylene diene monomer blends (EPDM) were studied at various concentrations of dicumyl peroxide (DCP) and gamma radiation doses. The blends showed improved mechanical properties for vulcanized sample. The coupling of DR/PP/EPDM with different proportions of DCP was investigated by X‐ray diffraction and scanning electron microscopy techniques. Evaluation of the developed blends, unirradiated and gamma irradiated, was carried out using elastic modulus, tensile strength, elongation at break, thermogravimetric analysis, kinetic analysis, and DSC measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40611.     

Effect of the compatibility on the morphology and properties of acrylonitrile–butadiene rubber/polypropylene thermoplastic vulcanizates

In this study, the morphologies of three types of acrylonitrile–butadiene rubber (NBR)/polypropylene (PP) thermoplastic vulcanizates (TPVs) (with an NBR/PP blend ratio of 70/30) were compared. The TPVs were (1) an ultrafine fully vulcanized acrylonitrile–butadiene rubber (UFNBR)/PP TPV made by the mechanical blending of UFNBR with PP, (2) a dynamically vulcanized NBR/PP TPV without the compatibilization of maleic anhydride grafted polypropylene (MP) and amine‐terminated butadiene–acrylonitrile copolymer (ATBN), and (3) a dynamically vulcanized NBR/PP TPVs with the compatibilization of MP and ATBN. The influence of the compatibility therein on the size of the dispersed vulcanized NBR particles and the crystallization behavior of the PP in the TPVs and the resultant properties are also discussed. As indicated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, polarizing microscopy, dynamic mechanical thermal analysis, and rheological and mechanical testing, the compatibility was significantly improved by the reactive compatibilization of MP and ATBN, which led to a uniform and fine morphology. The compatibilization increased the crystallization rate and reduced the size of the spherulites of PP. On the other hand, it was found that the dispersed vulcanized NBR particles lowered the degree of crystallinity. The better the compatibility of the blend was, the lower the degree of crystallinity and the storage modulus were, but the higher the loss factor and the processing viscosity were. All TPVs showed almost the same oil resistance, but the TPV prepared with reactive compatibilization had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012