The Effect of Dicumyl Peroxide Vulcanization on the Properties & Morphology of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber Blends

ABSTRACT

This article discusses some properties such as tensile properties, chemical and oil resistance, gel content, crystallinity, and morphology of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends. Dicumyl peroxide (DCP) was applied as a crosslinking agent. In terms of tensile properties, peroxide vulcanized blend shows higher tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) as compared with the unvulcanized blend. The elongation at break of the peroxide vulcanized blend is higher for the blend with NR rich content compared with the EPDM rich content. The improvements in chemical and oil resistance as well as gel content of peroxide vulcanized blends have also proved the formation of crosslinks in the rubber phase. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the crosslinks have occurred during dynamic vulcanization. Dynamical vulcanization with DCP has decreased the percent crystallinity of blends that can be attributed to the formation of crosslinks in the rubber.     

Influence of Type of Vulcanization on Rheological and Thermal Properties of PP/NR Blends

Summary Rheological and thermal behavior of isotactic polypropylene (PP) and natural rubber (NR) blends were studied, with special reference to the type of vulcanization (dynamic and static). It was found that dynamic crosslinking of the NR phase increases the viscosity of the system, while it decreases crystallinity degree. Statically vulcanized blends show similar properties regardless curing time while dynamically vulcanized blends show enhanced properties if compared to the corresponding uncured blends.     

Effects of blend composition and dynamic vulcanization on the morphology and dynamic viscoelastic properties of PP/EPDM blends

The morphology and dynamic viscoelastic properties of isotactic polypropylene (PP) blended with oil-free/oil-extended ethylene–propylene–diene (EPDM) rubbers were studied. Unvulcanized and dynamically vulcanized blends with the compositions PP/EPDM = 50/50 and = 30/70 were investigated. The morphology was observed by phase contrasted atomic force microscopy. The dynamic viscoelastic properties were determined with a rheometer of plate–plate configuration. It was shown that the rheological behavior was strongly affected by both the composition and the morphology of the blends. Significant improvement in the flowability of the dynamically vulcanized blends was observed when oil-extended EPDM was used instead of the oil-free version. It was demonstrated that the rheological properties are mostly controlled by the elastomer phase at low frequencies, while in the high-frequency range the influence of PP becomes dominant. The peculiarities in the rheological behavior of the thermoplastic elastomers (uncured blends, TPE) and thermoplastic dynamic vulcanizates (TPV, dynamically cured blends) containing oil-extended EPDMs were traced to a limited compatibility between the PP and EPDM components in the melt. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The control of miscibility of PP/EPDM blends by adding lonomers and applying dynamic vulcanization

The control of miscibility for isotactic polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) has been attempted by adding poly(ethylene-comethacrylic acid) (EMA) ionomers and by applying dynamic vulcanization. The rheological properties, crystallization behavior, and morphology of the dynamically vulcanized EPDM/PP/ionomer ternary blends were investigated with a Rheometrics dynamic spectrometer (RDS), a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Two kinds of EMA ionomers neutralized with different metal ions (Na⁺ and ZN⁺⁺) were investigated. Blends were prepared on a laboratory internal mixer at 190°C. Blending and curing were performed simultaneously, i.e., EPDM was vulcanized with dicumyl peroxide (DCP) in the presence of PP/ionomer. The composition of PP and EPDM was fixed at 50/50 by wt% and the contents of EMA ionomer were vaired from 5 to 20 parts based on the total amount of PP and EPDM. It was found that the addition of ionomers and the application of the dynamic vulcanization were effective in enhancing the miscibility of PP and EPDM. The structure of the blends was controlled by the following three component phases, i.e., the phase of the dynamially valcanized EPDM, PP, and Zn-neutralized ionomer. The ternary blends showed more miscibility than the PP/EPDM binary blend. This is due to the thermoplastic interpenetrating polymer network (IPN) of the ternary blends. The structure and properties of the ternary blends differed, depending on the types and contents of ionomer, i.e., the ternary blend containing Na-neutralized ionomer did not show a thermoplastic IPN structure clearly, even though the blend was prepared by dynamic vulcanization. The ternary blend containing Zn-neutralized ionomer clearly showed the behavior of a thermoplastic IPN when the contents of ionomer and DCP were 15 parts and 1.0 part, respectively.     

马来酸酐和苯乙烯接枝改性对天然橡胶/聚丙烯共混物物理机械性能的影响

用动态硫化法制备了天然橡胶(NR)/聚丙烯(PP)热塑性弹性体(TPV)。研究了马来酸酐/苯乙烯/过氧化二异丙苯(MAH/St/DCP)多单体熔融接枝交联改性及纳米二氧化硅用量对NR/PP TPV物理机械性能的影响,讨论了NR/PP TPV的重复加工性能。结果表明,当MAH/St/DCP用量为3.750/1.875/0.375质量份、纳米二氧化硅用量为3质量份时,NR/PP TPV的物理机械性能最好,达到了国内外有关通用橡胶/PP TPV的水平,并且具有较好的重复加工性能。     

Comparison of Rheological and Mechanical Behavior of Dynamically and Statically Vulcanized PP/SBS Blends

Summary Rheological behavior of dynamically and statically vulcanized blends of isotatic Polypropylene (PP) and 20% wt Styrene-Butadiene-Styrene block copolymer (SBS) was studied with reference to the effect of extrusion conditions, curing agents (sulphur, peroxide) and curing times. All blends showed pseudoplastic behavior. When using sulphur, a slight increase on melt viscosity was observed, showing no differences with vulcanization method or with pre-vulcanization time. With peroxide, melt viscosity changed drastically. Dynamically vulcanized blends with sulphur showed a noticeable rise on elongation at break as well as on toughness while those statically vulcanized showed very low values on these properties.     

Multifunctional peroxide as alternative crosslink agents for dynamically vulcanized epoxidized natural rubber/polypropylene blends

Commonly used dicumyl peroxide (DCP) in combination with coagent, triallyl cyanurate (TAC), as a crosslinking agent is well acceptable for dynamically vulcanized rubber phase of thermoplastic vulcanizates (TPVs). However, it generally produces volatile decomposition products, which cause a typical unpleasant smell and a blooming phenomenon. In this work, influence of two types of multifunctional peroxides: 2,4‐diallyloxy‐6‐tert‐butylperoxy‐1,3,5‐triazine (DTBT) and 1‐(2‐tert‐butylperoxyisopropyl)‐3‐isopropenyl benzene (TBIB), on properties of TPVs based on epoxidized natural rubber (ENR)/polypropylene (PP) blends were investigated. The conventional peroxide/coagent combinations, i.e., DCP/TAC and tert‐butyl cumyl peroxide (TBCP)/α‐methyl styrene (α‐MeS) were also used to prepare the TPVs for a comparison purpose. The TPVs with multifunctional peroxide, DTBT, provided good mechanical properties and phase morphology of small dispersed vulcanized rubber domains in the PP matrix which were comparable with the DCP/TAC cured TPVs. However, the TPVs with TBIB/α‐MeS and TBCP/α‐MeS showed comparatively low values of the tensile properties as well as rather large phase morphology. The results were interpreted by three main factors: the kinetic aspects of the various peroxides, solubility parameters of respective peroxide/coagent combinations in the ENR and PP phases, and the tendency to form unpleasantly smelling byproducts. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Effects of Dynamic Vulcanization by Dicumyl Peroxide (DCP) and N,N-m-Phenylene Bismaleimide (HVA-2) on the Properties of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Blends

ABSTRACT

This paper discusses some properties of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends, such as tensile properties, heat resistance, gel content, and morphology. Dicumyl peroxide (DCP) and N,N-m-phenylene bismaleimide (HVA-2) and their combination were applied in PP/EPDM/NR blends as cross-link agents. In terms of tensile properties, the combination of DCP with HVA-2 shows the highest tensile strength and elongation at break in all PP/EPDM/NR blend ratios compared to similar blends, except with DCP or HVA-2 alone. The addition of HVA-2 produced blends with good heat resistance, while the combination of DCP with HVA-2 shows the highest gel content dealing with the cross-links formation. SEM micrographs from the surfaces extraction of the blends support that the cross-links have occurred during dynamic vulcanization process.     

Properties of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends: The Effect of N,N-m-Phenylenebismaleimide (HVA-2) Addition

This paper discusses process development, tensile properties, morphology, oil resistance, gel content, and thermal properties of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) vulcanized blends with the addition of N,N-m-phenylenebismaleimide (HVA-2) as a compatibilizer. Blends were prepared in several blend ratios in a Haake Polydrive with temperature and rotor speed of 180°C and 50 rpm, respectively. Results indicated that the combination of dicumyl peroxide (Dicup) with HVA-2 shows high torque development and stabilization torque as compared to the blend with Dicup vulcanization alone. In terms of tensile properties, the combination of Dicup with HVA-2 shows higher tensile strength, tensile modulus (M₁₀₀), elongation at break, oil resistance, and gel content in all blend ratios compared to similar vulcanized blends with Dicup without HVA-2 addition. Scanning electron microscope (SEM) micrographs of the blends support that the cross-linking and compatibilization occur during the process of the vulcanized blend containing HVA-2. In the case of crystallinity of the blends, the addition of HVA-2 in Dicup vulcanized blend revealed a tendency for the percentage of crystallinity (Xc) to decrease. The addition of HVA-2 in Dicup vulcanization also produced blends with good thermal stability dealing with the so-called coagent bridge formation.     

Synergistic effect of gamma radiation and peroxide on dynamic vulcanization of thermoplastic vulcanizes based on (devulcanized rubber)/polypropylene

Devulcanized rubber (DR) with highly crystalline polypropylene (PP) was used to prepare thermoplastic vulcanizates on the basis of DR/PP (75/25) blends. Influences of the curing systems, dicumyl peroxide (DCP) and gamma radiation, were investigated by X‐ray diffraction and scanning electron microscopy techniques. The mechanical and thermal behaviors of the composites in different proportions were studied. We found that the elastic modulus and tensile strength of the thermoplastic vulcanizates exhibited higher values than unvulcanized material. This finding may be attributed to an improvement in DR dispersion as well as interaction networks between the PP matrix and DR in the presence of DCP and the formation of more stable linkages. Peroxide caused a degradation of the PP molecules. A higher level of DCP was used in the peroxide‐vulcanized system and caused greater influence on properties. The mechanical and thermal properties of the unirradiated and irradiated composites were evaluated. J. VINYL ADDIT. TECHNOL., 20:168–176, 2014. © 2014 Society of Plastics Engineers     

Influences of the phenolic curative content and blend proportions on the properties of dynamically vulcanized natural rubber/acrylonitrile–butadiene–styrene blends

The vulcanization of natural rubber (NR)‐blended acrylonitrile–butadiene–styrene (ABS) was carried out with a phenolic curing agent by a melt‐mixing process. The NR compound was first prepared before blending with ABS. The effects of the phenolic curative contents (10, 15, and 20 phr) and blend proportions (NR/ABS ratio = 50 : 50, 60 : 40, and 70 : 30) on the mechanical, dynamic, thermal, and morphological properties of the vulcanized NR/ABS blends were investigated. The tensile strength and hardness of the blends increased with increasing ABS content, whereas the elongation at break decreased. The strength property resulting from the thermoplastic component and the vulcanized NR was an essential component for improving the elasticity of the blends. These blends showed a greater elastic response than the neat ABS. The thermal stability of the blends increased with increasing ABS component. Scanning electron micrographs of the blends showed a two‐phase morphology system. The vulcanized 60 : 40 NR/ABS blend with 15‐phr phenolic resin showed a uniform styrene‐co‐acrylonitrile phase dispersed in the vulcanized NR phase; it provided better dispersion between the NR and ABS phases, and this resulted in superior elastic properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42520.     

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.     

Influence of incorporation methods of ATH on microstructure,elastomeric properties,flammability, and thermal decomposition of dynamically vulcanized NR/PP blends

Flame‐retardant thermoplastic vulcanizates (TPVs) of natural rubber (NR)/polypropylene (PP) (60/40 wt %) blends filled with alumina trihydrate (ATH) were prepared with an internal mixer. To increase the properties of flame‐retardant NR/PP TPV, the new mixing method, stepwise masterbatch mixing (SMB) method was adopted. The effects of SMB method along with different ATH loadings on microstructure and properties of NR/PP TPVs were investigated. Conventional one‐step mixing (CV) method was also studied for comparison. Transmission electron microscopy analysis showed that different processes led to a variation in microstructural homogeneity, which imposed various effects on blend properties. The mechanical properties of TPVs changed with ATH loading, and the strength of the samples obtained from SMB method was higher than those of CV method. LOI and cone calorimetry tests revealed that the flame retardancy of NR/PP blends dramatically increased at higher ATH loading. Furthermore, the increment level of flame retardancy was accelerated in the blends produced particularly through SMB method, resulting from homogeneity of local ATH distribution in NR/PP blend. Greater combustion resistance of blends prepared from SMB route were confirmed by thermogravimetry and pyrolysis‐gas chromatography–mass spectrometry techniques. Finally, a burning mechanism between filler structure and flammability of NR/PP TPVs obtained from CV and SMB methods was discussed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46231.     

Evolution of rheological properties and morphology development during crosslinking of polyolefin elastomers and their TPV blends with polypropylene

This work investigates the evolution of the rheological properties of elastomeric dynamically vulcanized ethylene‐α‐olefin copolymers (ECs) and their blends with polypropylene (PP), during peroxide initiated crosslinking. Rheological techniques are used in conjunction with gel content measurements to determine the onset of gelation during static crosslinking. The complex viscosity and moduli follow power‐law dependence with respect to frequency at the gel point. The relaxation exponent and corresponding values of tan δ at the gel point are determined from the complex viscosity versus frequency curves and used as criteria for the determination of the instance of gelation. The evolution of morphology of thermoplastic vulcanizate (TPV) blends consisting of EC and PP during dynamic crosslinking is discussed in the context of the evolving rheological properties of the matrix and the dispersed phase that take place upon peroxide modification. TPVs having the crosslinked EC as the matrix present a very fine morphology, whereas the blends containing crosslinked EC particles, present a coarser morphology. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Exploring the thermomechanical properties of peroxide/co-agent assisted thermoplastic vulcanizates through temperature scanning stress relaxation measurements

Temperature scanning stress relaxation (TSSR) measurement of peroxide vulcanized polymer blends of polypropylene (PP) and ultrahigh molecular-EPDM (UHM-EPDM) rubber has been performed to study the thermomechanical behavior of thermoplastic vulcanizates (TPVs). Co-agents play crucial roles in the enhancement of properties of TPVs. Different types of co-agents (Triallyl cyanurate-TAC; N, N-m-phenylene-dimaleimide-HVA2; zinc dimethacrylate-ZDMA; and in-situ formed zinc dimethacrylate-ZMA) have been explored in this work. TSSR study shows that higher T₅₀ and T₉₀ values have been achieved in ZMA co-agent assisted-TPV. Higher TSSR-index (RI) value was also found for the same co-agent ZMA, indicating higher elastic behavior. TSSR result supports the mechanical and rheological properties, and it is found that the ZMA and ZDMA show higher mechanical strength. Cross-linked-density calculated by modified Flory–Rehner equation and the cross-link-density as obtained from TSSR method have been compared and the trend was found to be the same. Stress relaxation study shows the slow relaxation-phenomena of the ZMA-TPV with slowest relaxation-time (θ_r) than the other TPVs, which correlates with superior material strength. Thermogravimetric analysis proves that there is a difference in degradation temperature of the blends at approximately 5–10°C. Ultrahigh molecular weight-EPDM/PP based TPVs reveal superior thermomechanical and physico-mechanical properties with ZMA and ZDMA co-agent over TAC and HVA2. These ultrahigh molecular weight-EPDM based TPVs can be used in automotive seals/strips, hoses, bellows, and 2 K-molds for automotive applications.     

Cure characteristics and mechanical properties of hydrogenated natural rubber/natural rubber blends

The cure characteristics and mechanical properties of blends consisting of hydrogenated natural rubber (HNR) and natural rubber (NR) blends were investigated. The HNR/NR blends at 50/50 wt ratio were vulcanized using various cure systems: peroxide vulcanization, conventional vulcanization with peroxide, and efficient vulcanization with peroxide. The HNR/NR vulcanizates cured by the combination of peroxide and sulfur donor (tetramethylthiuram disulfide, TMTD) in the efficient vulcanization with peroxide exhibited the best mechanical properties. It was also found that the hydrogenation level of HNR did not affect the tensile strength of the vulcanizates. The tensile strength of the blends decreased with increasing HNR content because of the higher incompatibility to cause the noncoherency behavior between NR and HNR. However, the HNR/NR vulcanizate at 50/50 wt ratio showed the maximum ultimate elongation corresponding to a co‐continuous morphology as attested to by scanning electron micrographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of some curatives on the properties of ethylene propylene diene rubber/polyethylene blends

A series of ethylene propylene diene rubber/polyethylene (EPDM/PE) blends has been prepared containing different weight fractions of PE up to 0.66. The blends were vulcanized with a sulphur system N-cyclohexyl-2-benzthiazol sulphenamide/sulphur (CBS/S), and a non-sulphur-system dicumyl peroxide (DCUP). The concentration of the latter has been changed from 1.5 phr up to 6 phr calculated on the total weight of the blend composition. It has been found that the maximum torque obtained from rheographs for blends vulcanized with the CBS/S system decreases markedly with increasing PE concentration in comparison with those vulcanized with peroxide. The E modulus obtained from the stress–strain diagram at 110 °C showed the role played by the crosslinking of PE, the E modulus for blends vulcanized by peroxide being higher than for samples vulcanized with CBS/S. In contrast, the values of E modulus of both samples are practically the same at room temperature and attain more than 40 MPa depending on the composition. The tensile strength at room temperature strongly increases with increasing the weight fraction of PE. It has also been confirmed that the melting point of the crystalline phase of PE decreases with increasing crosslinking density of PE. The shear modulus obtained from dynamic mechanical measurements is in accordance with that obtained from static mechanical measurements. © 1999 Society of Chemical Industry     

Effects of Composition and Dynamic Vulcanization on the Rheological Properties of PP/NBR Blends

Summary Rheological behavior of isotactic polypropylene (PP) and nitrile rubber (NBR) blends, in the composition range of 10–30-wt % NBR content were studied, with special reference to the effect of blend ratio, dynamic vulcanization and compatibilization. All blends were prepared in a twin-screw extruder. Capillary Rheometry was employed. Pseudoplastic behavior of blends was favored by increasing rubber content. The incorporation of NBR into PP lowered activation energies. Compatibilization of unvulcanized blends did not produce significant changes on flow behavior. Dynamically vulcanized blends provide unique processing characteristics that enable to perform well in both injection molding and extrusion. Received: 8 October 2002/Revised version: 3 March 2003/Accepted: 4 March 2003 Correspondence to M. Hernández     

The Effect of Dynamic Vulcanization on the Properties of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber (PP/EPDM/NR) Ternary Blend

The effects of dynamic vulcanization on the process development and some properties, such as tensile properties, swelling index, gel content, crystallinity, and morphology, of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends were investigated. Dynamically vulcanized blends show higher stabilization torque than unvulcanized blends. In terms of tensile properties, the tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) of the vulcanized blends have been found to increase as compared with the unvulcanized blends, whereas the elongation at break is higher in the blend with richer EPDM content. These results can be attributed to the formation of cross-linking in the rubber phase. The formation of cross-links in the rubber phase has also been proved by swelling index and gel content. The percentage of crystallinity of the blends is decreased by dynamic vulcanization. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the cross-links occurred during dynamic vulcanization.     

Reactive extrusion of PP/natural rubber blends

Reactive extrusion of polypropylene (PP)/natural rubber (NR) (90/10) blends was conducted in the presence of a peroxide [1,3-bis(t-butylperoxy)benzene] and coagent (trimethylolpropanetriacrylate, TMPTA). Effects of peroxide and coagent content were studied in terms of melt index (MI), melt viscosity, morphology, thermal, and mechanical properties. At a constant content of the coagent, melt viscosity increased at a low and decreased at a high content of the peroxide. On the other hand, melt viscosity increased monotonically with the coagent concentration at constant peroxide content. The increase and decrease of viscosity were interpreted in terms of crosslinking and chain scission of PP, which governed the rubber domain size and mechanical properties of the reactive blends. © 1995 John Wiley & Sons, Inc.