Amount Of Dicumyl Peroxide Research Articles

The role of dicumyl peroxide in the preparation of chloroprene rubber/starch/sodium acrylate water-swellable composites

Water-swellable composites were prepared by blending sodium acrylate (NaAA), additives, and chloroprene rubber (CR)/starch masterbatch which was pre-formed by latex compounding method. The effects of the content of dicumyl peroxide (DCP) on the properties of the composites were investigated. We found that an increase in DCP amount led to a large increase in water swelling ratio and meanwhile a decrease in the mass loss ratio. Further, the composites were swollen uniformly in water and thus kept their original shapes well. The hardness and stresses at 100% and 300% increased with the increase in DCP amount. The addition of DCP facilitated the homopolymerization of NaAA while decreased the esterification reaction between NaAA and CR, which was verified by vulcanization curves, DSC and FT-IR. The morphology of the composites before and after water immersion was observed by optical transmission microscopy and indicated that the starch was homogenously dispersed in the composites.

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

AbstractThe poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the Tg and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10−3 S cm−1 at room temperature and 1.42 × 10−2 S cm−1 at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3O2 cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3 O2 cell is 115.3 mAh g−1. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

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

AbstractMechanical 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.

Fracture behaviors of metallocene catalyzed polyethylene elastomer via peroxide crosslinking

AbstractPeroxide cured metallocene catalyzed polyethylene (mPE) has been prepared to form an elastomer. mPEs with two different levels of comonomer contents have been cured with various amounts of dicumyl peroxide. “Threshold” fracture energy is roughly proportional to the reciprocal square root of Young's modulus. The values of tear strength are generally two orders of magnitude larger than the results from cutting measurements. The cutting strength of mPE vulcanizates gives an intermediate value compared with crystalline plastics and conventional elastomers and is comparable with other evaluations of cutting strength for different crosslinking types of mPE and different types of materials, which further signifies the importance of crystalline yielding even in the nanofracture zone of deformation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In situ fibrous structure oriented polymer blends composed of poly(lactic acid) and polycaprolactone containing peroxide

A fibrous dispersed phase stuffed with polycaprolactone (PCL) was constructed in a poly(lactic acid) (PLA) matrix during an injection-molding process. The injection-molding process showed efficiency in forming dispersions with fibrous shapes, and they could impart the ductile property of PCL to the brittle PLA matrix, with appropriate interfacial adhesion arising from the cocrosslinking structure at the PLA/PCL interface by dicumyl peroxide (DCP). However, the addition of excess DCP caused a split of the dispersions resulting from the compatibility increment and the excess crosslinking reaction at the interface and inside each phase. The addition of a small amount of DCP could adhere the interface without splitting of the dispersions. The observed internal structure in the injection moldings showed a morphology transition that changed gradually from a fine fibrous morphology to a coarse morphology at a deeper position in the injection moldings. The tensile properties of sliced local layers, which were fabricated with a sliding microtome, proved that the fibrous morphology was effective in the improvement of ductility of the blends. An X-ray analysis showed that the shear flow increased the crystalline orientation and formed a different crystalline structure only in the PCL dispersed phase, but its crystalline structure was not the main factor for ductility improvement. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The Effect of Feed Composition of Styrene and Acrylic Acid on the Properties of Modified Low Density Polyethylene

AbstractSummary: Low density polyethylene (LDPE) was functionalized with different molar ratios of styrene (St) to acrylic acid (AA) in the presence of dicumyl peroxide (DCP) in the molten state. The resultant LDPE was characterized by gel content and torque analysis. The results showed that the gel content of polymers grafted with small molar ratios (St/AA = 0.5) was always higher than those grafted with the equimolar St/AA ratio. The effect of DCP amount and AA concentration on the grafting degree of AA was investigated. The suitable DCP amount and AA concentration was obtained. Functionalized LDPE [LDPE‐g‐(AA‐St)] was characterized by Fourier transform infrared spectroscopy (FTIR), melt flow rate (MFR), water contact angle and capillary rheometry. The results showed that both MFR and grafting degree of AA of LDPE‐g‐(AA‐St) was the highest when an equimolar AA/St ratio was used, but when mixtures of St and AA (St/AA = 1/10) were loaded, the water contact angle of the film prepared from the LDPE‐g‐(AA‐St) was the smallest, which indicated that the hydrophicity of the film surface not only depended on the grafting degree, but also the molar ratios of the hydrophobic/hydrophilic groups.

Study of the Impact Resistance of Physically and Dynamically Vulcanized Mixtures of PP/EPDM

AbstractPhysically and dynamically vulcanized (TPV) mixtures of polypropylene (PP) and ethylene propylene diene terpolymer (EPDM) are prepared by extrusion in order to improve the impact resistance of PP. To enhance the chemical compatibility and provide better interaction between the PP and EPDM in the physical mixtures, both polymers are modified with maleic anhydride (MAH) in solution using xylene as solvent and dicumyl peroxide (DCP) as initiator. The qualitative and quantitative determination of the degree of grafting is study by Fourier Transform Infrared Spectroscopy (FTIR) and varying the amount of DCP and/or amount of MAH in order to determine the optimum amounts to obtain the highest degree of grafting. The effect of the relation of PP/EPDM, the amount of reinforcement filler and mix rate are studied for modified polymer mixtures (PP‐g‐MAH/EPDM‐g‐MAH). For the TPV of PP/EPDM the effects of amount and triallylisocyanurate (TAC) as coupling agent in presence of different amounts of DCP are studied. The physical mixtures of modified polymers prepared with a PP/EPDM ratio of 80/20 and the TPVs blends prepared with a PP/EPDM ratio of 70/30 and containing 15% filler at 60 rpm show the highest impact resistance. The impact resistance, melt flow index and hardness of the different mixtures are measured to determine their possible applications to prepare front panels and bumpers for automobiles by injection molding.

The effect of curing on sorption and diffusion of a brake fluid in EPDM elastomer

AbstractThe effect of a poly(ether glycol) brake fluid on cured EPDM (ethylenepropylene- diene monomer) elastomer based on 5-ethylidene-2-norborene has been studied. Different amounts of dicumyl peroxide (DCP) curing agent were used and the effect of ageing in a brake fluid (at 100°C for 70 h) on technical properties of EPDM have been investigated. By increasing the amount of DCP, significant changes were not observed. Tensile strength and modulus increased but elongation at break and abrasion loss decreased due to oxidative degradation and crosslinking. Hardness was constant due to the replacement of plasticizer with brake oil.

Preparation and properties of metallocene ethylene copolymer crosslinked by vinyltrimethoxysilane

AbstractSilane‐grafting and water‐crosslinking of ethylene–octene copolymer (EOR) was carried out. The influences of grafting formulation, comonomer content in EOR and time of the crosslinking process on grafting efficiency, degree and rate of crosslinking were investigated. The mechanical properties of various crosslinked samples are reported together with correlations with their gel contents. The results show that the extent of grafting increased with an increase in the amounts of dicumyl peroxide (DCP) and vinyltrimethoxysilane (VTMS) used in the reaction. The degree of crosslinking depended mainly on the extent of grafting, while the rate of the crosslinking process depended on the amount of amorphous phase in the samples. In this study, the variation of gel contents in the samples (0–77 %) had no significant influence on tensile properties. A large number of uncrosslinked regions are believed to exist inhomogeneously within the crosslinked polymers even after the sample has reached maximum gel content. The content of gel did not increase further when the crosslinking time was increased beyond that of reaching maximum gel, but the polymer network became denser, resulting in changes in polymer behaviour. Copyright © 2005 Society of Chemical Industry

Preparation and Characterization of trans‐1,4‐Polybutadiene Nanocomposites Containing in situ Generated Silica

trans‐1,4‐Polybutadiene (tPBD) networks crosslinked free radically with dicumyl peroxide (DCP) were reinforced by in situ silica formed in a two‐step sol–gel technique. Changing the degree of crosslinking by changing the amount of DCP, or changing the amounts of the sol–gel components [tetraethoxysilane (TEOS) and dibutyltin diacetate (DBTDA)], changed the silica generated with regard to the amount precipitated, particle size, and degree of dispersion. Stress–strain measurements in continuous extension indicated good reinforcement, even at relatively low amounts of silica. Differential scanning calorimetry (DSC) indicated decreases in heat of crystallization with increases in the amounts of silica, but thermogravimetric analysis showed initial decomposition temperatures (IDT) remained relatively constant. Suggestions are made regarding interpretation of these properties in terms of the composite morphologies.

Modyfikacja polietylenu malej gestosci allilomocznikiem

Modification of low-density polyethylene (PE-LD) with allylurea (AM) by reactive extrusion in the presence of dicumyl peroxide (DCP) as radical initiator of the expected grafting reaction has been described. Modification has been done in order to increase PE-LD susceptibility to degradation in the environment. FT-IR investigations showed the probability of the intermolecular AM condensation during processing at the conditions applied (Figs. 2, 3). The changes found should not impede the process of AM grafting. The slip of extruder screw, caused by AM, has been limited by addition of silica (K) to the composition. Composition properties have been studied in wide range of concentrations of silica (up to 8 wt. %), allylurea (up to 8 wt. %) and peroxide (up to 0.6 wt. %). The material showing good breaking strength was obtained when silica content in the composition (equal to AM content) was 3 wt. %. Gel number of various compositions was also determined. The samples obtained at small amounts of DCP, up to 0.2 wt. %, showed required low crosslinking degree (Table 1). FT-IR analysis suggests the partial grafting of allylurea onto PE chains (Table 2).

Study of heat shrinkability of crosslinked low‐density polyethylene/poly(ethylene vinyl acetate) blends

AbstractIn this study, the heat‐shrinkage property in polymer was induced by first compounding low‐density polyethylene/poly(ethylene vinyl acetate) (LDPE/EVA) blends with various amounts of peroxide in a twin‐screw extruder at about 130°C. The resulting granules were molded to shape and chemically crosslinked by compression molding. A process of heating–stretching–cooling was then performed on the samples while on a tensile machine. Shrinkability and effective parameters were also investigated using thermal mechanical analysis. The results showed that the gel fraction was higher for the sample of higher EVA content with the same amount of dicumyl peroxide (DCP). A decrease in the melting point and heat of fusion (ΔHf), as determined from DSC, was observed with an increase in the DCP content. Studies on the heat shrinkability of the samples showed that samples stretched above the melting point had a higher shrinkage temperature than those stretched around the crystal transition temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. These could be attributed to the formation of new spherulites as well as changes in the amount and the size of crystals. Furthermore, in samples elongated at 120°C (above the melting point), the rate of stretching had no effect on the shrinkage temperature. The results showed that the extent of strain had no effect on the temperature of shrinkage, but rather on the ultimate shrinkage value. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1389–1395, 2004

Graft copolymerization of oleic acid onto low‐density polyethylene in the molten state

AbstractA graft copolymer of oleic acid (OA) onto low‐density polyethylene (LDPE) was prepared using dicumyl peroxide (DCP) as an initiator in the molten state. The grafting was carried out in a Haake rheometer. The effects of the reaction time and the amount of DCP and the monomer on the percentage of grafting were studied. The rheological behavior and the melt‐flow rate of the graft copolymer (LDPE‐g‐OA) were also investigated. FTIR spectroscopy and a mass spectrum were used to characterize the structure of LDPE‐g‐OA. The experimental results showed that when the OA amount was 10 wt % and the DCP amount was 0.4 wt % based on the LDPE the percentage of grafting of LDPE‐g‐OA, prepared by maintaining the temperature at 170°C and the roller speed at 80 rpm, was about 6 wt %. It was found that both LDPE and LDPE‐g‐OA were pseudoplastic fluids. OA was grafted onto LDPE in the form of a monomer and a dimer. The grafted LDPE is expected to act as a compatibilizer between starch and polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3299–3304, 2003

Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene‐styrene interpolymers

AbstractFoamed materials (EVA/ESI) have been prepared from blends of ethylene‐vinyl acetate copolymer (EVA) and ethylene‐styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from −2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the α glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom‐designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break.

Structure and mechanical properties of SRP/HDPE/POE (EPR or EPDM) composites

The effects of dicumyl peroxide (DCP) and ethylene-octylene copolymer (POE), ethylene-propylene copolymer (EPR) or ethylene-propylene-diene terpolymer (EPDM) on the structure and properties of scrap rubber powder (SRP)/high-density polyethylene (HDPE) composites were studied. Torque and gel content results show that DCP promotes crosslinking of the SRP/HDPE/POE (EPR or EPDM) composites. The SRP/HDPE/POE (EPR or EPDM) composites containing a small amount of DCP have better mechanical properties than their corresponding composites without DCP. Highest tensile strength and elongation at break are found in the dynamically vulcanized SRP/HDPE/POE composite. Scanning electron microscopy (SEM) results show that good bonding between SRP and matrix is formed in the SRP/HDPE/POE (EPR or EPDM) composites with DCP.

Study on Crosslinking of Polyethylene–Octene Elastomer with Dicumyl Peroxide

A crosslinkable metallocene polyethylene–octene elastomer (POE) containing different amounts of dicumyl peroxide (DCP) was prepared in a mixer at 110°C to remove the methanol and to ensure a uniform distribution of DCP. A crosslinking reaction of the crosslinkable mixture was carried out for 20 min in a hot press at 140°C. The properties of crosslinked products have been examined in the present study. From the results of 13C NMR, it was found that H-Link was produced on the molecular structure of POE resulting from the crosslinking reaction with DCP. The molecular weight (MW) between crosslinks of the gel was determined from Flory-Rhener theory and the result showed that MW decreased as DCP concentration was increased. According to the result of DSC and x-ray diffraction characterizations, it was found that the crystalline structure of POE was altered after crosslinking and the degree of crystallization decreased with increasing DCP content. Tensile and tear tests showed that the magnitudes of tensile strength and elongation at break, fracture energy, threshold fracture energy, and effective unstrained diameter of the tear tip all decreased when the DCP loading was increased.

High‐density polyethylene modified by polydimethylsiloxane

High-density polyethylene (HDPE) was modified by the grafting of polydimethylsiloxane (PDMS) through a free-radical process, in a melt-mixer chamber, using dicumyl peroxide (DCP) as an initiator. The influence of PDMS (0.2–0.8 mol %) and peroxide (0.03–0.08 mol %) concentrations on the grafting, final torque, and melt flow rate (MFR) of copolymers were investigated using factorial planning. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), MFR, and rheometry were used to characterize the copolymers obtained. Surface plots showed that higher degrees of grafted PDMS and higher final torques were obtained with increase in the PDMS amount at low DCP levels and with increase in the DCP amount at low PDMS levels. The peaks of fusion and crystallization of the copolymers showed no significant changes with respect to HDPE. Data of MFR and GPC suggested that crosslinking reactions and/or chain extension occurred concomitant with the grafting reactions. Copolymers with high grafting degrees showed high MFR and low dynamic shear viscosities in comparison with low grafting degree copolymers, which is probably due to the migration of the PDMS-containing copolymers on the surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3460–3467, 2001

Comparative TMA and NMR investigation of a structure of carbon-black-free cured butadiene rubber

Butadiene rubbers (BRs) differing in isomeric content and cured with different amounts of dicumyl peroxide (DCP) have, according to TMA investigations, regions with two glass transition temperatures (low and high) and different thermal expansion properties. BR network has chemical and cluster type (physical localised) branching junctions. For rubbers of the same isomeric content, shares of such regions depend on concentration of DCP. This fact suggests cis–trans isomerization at curing, which increases the content of a high-temperature region with predominantly chemical branching junctions, because cluster type branching junctions start to relax at T g″. It is supposed that an essential change in T g, if DCP concentration in the rubber compound is varied, is determined by the different molecular mobility of the chains included in associated structures of cluster junctions of a network of cured rubber. Such mobility also increases if 1,2 (vinyl) isomer is present in the BR chain. The latter is probably distributed uniformly between the chains of both regions. In a low-temperature region it could act as an antiplasticizer, whereas in a high-temperature region as a plasticizer. The molecular weight distribution of the chains between the junctions of a low-temperature region is virtually bimodal for low DCP concentration in rubber compounds. This could result from some zones with different crosslinking degree within the network. It is believed that this region has branching junctions, which are of a low crosslink density of chemical types and a high crosslinking density of cluster type junctions. A wide spectrum of isomeric content in neat and cured BR when a medium content of DCP was used meant that a low-temperature region had unimodal and symmetric MWD between the junctions. In a high-temperature region the exact opposite phenomenon may be observed — separation of chain segment length giving a bimodal MWD. A possible reason for this is non-uniform distribution of 1,2 (vinyl) isomer within the chains of a high-temperature region. The shift in MWD between the junctions from bimodal to unimodal as DCP content is raised, which was identified using TMA, confirms our 2H NMR findings. The two splits in the 2H NMR spectra observed at lower DCP contents could result from regions with different crosslink density, as we have argued in a recently published paper. All these conclusions confirm the applicability of the adopted TMA for testing a complex structure of rubbers.

High‐density polyethylene modified by polydimethylsiloxane

AbstractHigh‐density polyethylene (HDPE) was modified by the grafting of polydimethylsiloxane (PDMS) through a free‐radical process, in a melt‐mixer chamber, using dicumyl peroxide (DCP) as an initiator. The influence of PDMS (0.2–0.8 mol %) and peroxide (0.03–0.08 mol %) concentrations on the grafting, final torque, and melt flow rate (MFR) of copolymers were investigated using factorial planning. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), MFR, and rheometry were used to characterize the copolymers obtained. Surface plots showed that higher degrees of grafted PDMS and higher final torques were obtained with increase in the PDMS amount at low DCP levels and with increase in the DCP amount at low PDMS levels. The peaks of fusion and crystallization of the copolymers showed no significant changes with respect to HDPE. Data of MFR and GPC suggested that crosslinking reactions and/or chain extension occurred concomitant with the grafting reactions. Copolymers with high grafting degrees showed high MFR and low dynamic shear viscosities in comparison with low grafting degree copolymers, which is probably due to the migration of the PDMS‐containing copolymers on the surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3460–3467, 2001

Foaming of aliphatic polyester using chemical blowing agent

AbstractPoly(butylene adipate‐co‐succinate) (PBAS), a saturated aliphatic polyester cured by dicumyl peroxide (DCP), was prepared and the viscoelastic property was investigated. The viscosity of crosslinked PBAS increased, and it exhibited rubbery behavior as the content of curing agent was increased. The results suggested that the viscosity and elasticity of PBAS could be regulated by adding a small amount of DCP; hence, the processibility could be improved. Prior to foaming, a proper formulation of blowing agent (blowing agent/urea activator = 100:8 phr) was examined to prepare expanded PBAS foam. Low‐density PBAS expanded foams were prepared using a chemical blowing agent and DCP. The effect of the foaming temperature, additive content, and curing agent content on the blowing ratio and morphology of expanded PBAS foams was investigated. A closed‐cell structure PBAS foam of high blowing ratio (density about 0.05 g/cm3) could be obtained by adding 3 phr DCP. To manufacture expanded PBAS foam under 0.1 g/cm3 using a chemical blowing agent, the storage modulus of the matrix polymer should exceed the loss modulus by enough to stabilize growing bubbles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2443–2454, 2001