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.     

Dynamic vulcanization of recycled milk pouches (LDPE–LLDPE) and EPDM blends using dicumyl peroxide

The viability of thermomechanical recycling of post‐consumer milk pouches (blend of low‐density polyethylene (LDPE) and linear low‐density polyethylene (LLDPE)) and its scope for suitable engineering applications were investigated. The effects of blending with ethylene‐propylene‐diene monomer (EPDM) rubber and subsequent curing using dicumyl peroxide (DCP) on the macromolecular structure and properties of recycled polyethylene (PE) blends were studied. The crosslinking efficiency of recycled PE/EPDM blends and possible thermooxidative degradation of recycled polymer upon peroxide curing was assessed using torque and gel content measurements along with infrared spectroscopic analysis. Both the torque and gel content of the blends varied with DCP crosslinking reactions and also were affected by oxidative degradation. In view of the electrical application area of this recycled blend material, the dielectric breakdown strength and volume resistivity were measured. The mechanical performance and thermal stability of recycled PE/EPDM blends improved with progressive crosslinking by DCP but deteriorated somewhat at higher DCP dose. Scanning electron microscopy showed good interface bonding between recycled polymer and dispersed EPDM phase in the cured blends compared to the non‐cured blends. Copyright © 2007 Society of Chemical Industry     

助交联剂TAIC对聚丙烯发泡性能影响的研究

在过氧化二异丙苯（DCP）引发下,研究三烯丙基异氰脲酸酯（TAIC）对聚丙烯（PP）的交联程度、熔体强度及其发泡性能的影响。在TAIC加入前后,分别测定PP的抗流淌能力和熔体流动速率及PP发泡材料的凝胶率和力学性能。结果表明,DCP／TAIC交联体系使PP的抗流淌时间平均延长了6-7min;当DCP为1．4份时,PP发泡材料的最大凝胶率提高14％,拉伸强度和撕裂强度分别提高了24．5％和55．8％。偏光显微镜观察结果显示,在DCP/TAIC交联体系作用下,PP发泡材料表面光滑,泡孔细密且均匀一致。     

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     

化学交联聚丙烯的研究

本文通过测定交联聚丙烯的凝胶含量及流变性，研究了以Ｎ，Ｎ＇－间苯基双马来酰亚胺作为交联助剂的过氧化二异丙苯引发聚丙烯的交联反应，结果表明ＰＰ必须交联助剂的存在下才能发生交联反应，其交程序与引发剂，交联助剂的含量以及工艺条件有关。     

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.     

Enhanced toughening of poly(propylene) with reclaimed‐tire rubber

The dynamic vulcanization of reclaimed‐tire rubber (RTR) and homopolypropylene (PP) was performed by melt‐mixing using either a sulfur crosslinking agent, maleic anhydride (MA), dicumyl peroxide (DCP), or the combination of MA and DCP, in two consecutive machines, first a two‐roll mill and then a counterrotating twin‐screw extruder. In the case of applying a sulfur crosslinking agent, it was demonstrated that the RTR/PP blend at the ratio of 30/70 had the highest impact strength. This could be attributed to the limitation of carbon black in the blend. When the combination of MA and DCP was applied, the result was higher impact strength of the blend at the same ratio. This could be attributed to not only the cohesion between the polymer chains in each phase, PP phase and rubber phase, but also the interfacial adhesion between PP and RTR chains in these two phases. For comparison, the GRT/PP blends with and without sulfur crosslinking agent were prepared as well. All these blends showed low impact strength, which was nearly the same as that of PP. The effects of different crosslinking agents on dispersion and distribution of rubber domain size, viscosity, and percentage crystallinity were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 510–515, 2004     

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.     

Effect of the various coupling agents on the mechanical and physical properties of thermoplastic‐bagasse fiber composites

Various types of bonding agents have been tried with blends of bagasse fibers and some thermoplastics such as low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC). These bonding agents are, namely, pentaerythritol tetracrylate (PETA), 1,6 hexandiol diacrylate (HDA), and dicumyl peroxide (DCP). In addition, a traditional coupling agents 3‐aminopropyltrimethoxy silane (AMPS) and di‐aminopropyltrimetoxy silane (DAMPS) were included for comparison. Electron beam (EB) irradiation is applied only for LDPE and HDPE at 40 and 10 kGy, respectively, before mixing with bagasse fibers. The data obtained reveal that incorporation of bonding agents remarkably increases the mechanical properties for all samples under investigation; the maximum improvement is observed in LDPE followed by HDPE, PP, PS, and PVC composites. Also, the physical properties enhanced but not at the same degree as mechanical properties. Among the tested bonding agents, it was found that PETA, DCP followed by DAMPS have highest efficiency in LDPE, whereas in case of HDPE, EB radiation was higher than PETA followed by DCP. PETA was superior in case of PS composites. Furthermore, PETA and HDA experienced higher efficiency than DAMPS and AMPS in case of PP and PVC composites. Comparison between the properties of thermoplastic composites and medium density fiberboard (MDF) reveals that most of the properties of thermoplastics composites are better than MDF. However, modulus of rupture of MDF was found to be slightly higher than thermoplastics except for PVC composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Tensile properties and morphology of the dynamically cured EPDM and PP/HDPE ternary blends

The tensile properties and morphology of the polyolefin ternary blends of ethylenepropylene–diene terpolymer (EPDM), polypropylene and high density polyethylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured in the presence of PP and HDPE under shear with dicumyl peroxide (DCP). For comparison, blends were also prepared from EPDM which was dynamically cured alone and blended with PP and HDPE later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastics composition was studied. The tensile strength and modulus increased with increasing DCP concentration in the blends of EPDM-rich compositions but decreased with increasing DCP concentration in blends of PP-rich compositions. In the morphological analysis by scanning electron microscopy (SEM), the small amount of EPDM acted as a compatibilizer to HDPE and PP. It was also revealed that the dynamic curing process could reduce the domain size of the crosslinked EPDM phase. When the EPDM forms the matrix, the phase separation effect becomes dominant between the EPDM matrix and PP or HDPE domain due to the crosslinking in the matrix.     

DCP用量对动态硫化POE/PP热塑性弹性体性能的影响

研究了过氧化二异丙苯(DCP)用量对动态硫化乙烯一辛烯共聚物聚丙烯(POE/PP)体系的物理性能以及PP结晶形态和POE相态结构的影响。结果表明:随DCP用量的增加,POE/PP体系的交联密度增大,而断裂伸长率、永久变形和拉伸强度下降。过量DCP的加人会导致PP降解,使体系的熔体流动速率随DCP用量的增加呈上升趋势。DSC分析表明,随着DCP用量的增加,POE/PP体系结晶度下降。微观分析得出,DCP对POE/PP体系相态结构影响显著,当DCP用量为1份时交联POE以较小的颗粒均匀分布于PP连续相中。     

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     

Reactive extrusion of polyolefin ternary blends

Reactive extrusion of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM)/high-density polyethylene (PE) (80/10/10 by weight) blends were carried out using a corotating twin-screw extruder. The effects of peroxide and coagent concentrations and extruder rpm were studied in terms of rheological, morphological, thermal, and mechanical properties of the blends. Melt viscosity of the peroxide-treated blend increased and decreased over the untreated one depending on the amount of a coagent. Morphologically, interfaces blur with only a peroxide treatment, and significant domain reduction was obtained when peroxide and a coagent were used together. Both T_m (crystalline melting temperature) and T_g (glass transition temperature) of PP increased in the blend, whereas those of PE slightly decreased. © 1996 John Wiley & Sons, Inc.     

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     

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     

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.     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of polypropylene/acrylonitrile–styrene copolymer alloys by one‐step reactive blending

The compatibilization of polypropylene/acrylonitrile–styrene (PP/AS) blends through the addition of peroxide (DCP) was investigated in this study. The grafting reaction between PP and AS with the addition of peroxide occurred during the reactive‐blending process. The in situ‐formed grafting copolymers of PP‐g‐AS and AS‐g‐PP were then characterized by FTIR. The optimum concentration of the initiator, DCP, was 0.2 wt %, and the reaction temperature should be above 195°C. It was found that, when AS was the major component of the blends, the grafting of AS onto PP was the main process; conversely, when PP was the major component, PP was grafted onto AS. These results can be explained by the main‐chain scission of PP during the reactive‐blending process. With increase of the AS component, the total degree of grafting increased at first and then decreased after the composition of the blends reached 50/50. The maximum degree of grafting was found to be 6 wt % for the 50/50 PP/AS/DCP blend. PP was more degradable than was AS in the presence of peroxide at high temperatures. The MFR values of the PP/AS/DCP blends were slightly greater than were those of the simple PP/AS blends, which means that blending is an effective way to protect PP from degradation. SEM micrographs of the cross section of PP/AS/DCP showed a fine dispersion and a smaller domain size of the dispersed‐phase particles, implying that the in situ‐formed grafting copolymers act as a compatibilizer to reduce the interfacial tension between the PP and AS phases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1284–1290, 2001     

LLDPE/POE共混物的交联行为研究

采用过氧化物交联研究了线性低密度聚乙烯(LLDPE)/乙烯-α-辛烯共聚物(POE)共混物。研究了工艺、配方对LLDPE/POE共混物凝胶含量的影响,以及凝胶含量与材料力学性能的关系。结果表明,LLDPE/POE共混物的凝胶含量随引发剂的用量、交联温度和交联时间的增加而增加,达到一定程度后不再增加。在170℃,30min的条件下DCP能充分分解引发交联反应,DCP用量为1.5%时,共混物的凝胶含量可以达到80%以上,再增加时凝胶含量不再增加。DCP的加入顺序对共混物的凝胶含量影响不大。共混物的凝胶含量对其动态力学行为有影响。共混物的凝胶含量对拉伸性能影响不大。     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001