Presence Of Dicumyl Peroxide Research Articles

Preparation and Characterization of Functionalized Polypropylene with Acrylamide and Itaconic Acid

Functionalized polypropylene with acryl amide (AAm) and itaconic acid (IA) were prepared in the molten state in the presence of dicumyl peroxide. The effects of the concentration of both mono- mers on the degree of functionalization and properties of the products were investigated by FT-IR, contact angle measurement and DSC analysis. It was found that the degree of functionalization depends on the initial concentration of both monomers that used in the reaction. The influence of the AAm and IA content on the melting and crystallization temperature of PP was investigated by DSC. The contact angle of water on film surfaces of the functionalized PP (PP-g-AAm and PP-g-IA) decreased with increasing modified polymer content. From FT-IR spectra of functionalized PP a calculation was made of carbonyl index on the films surfaces. It was found that the higher intensity of the carbonyl index, the lower contact angle value and the lower crystallinity confirmed the ex- istence of functionalized AAm and/or IA in PP. It was concluded from the different characteriza- tion methods that the polarity and percentage of functionalized PP were increased up to 3 phr for both monomers, and then it was decreased by increasing the amount of monomers and had a threshold value, due to nucleating agents of monomers in PP.

Promoting crystallization of polylactide by the formation of crosslinking bundles

In this study, the influence of crosslinking structures on the crystallization of polylactide (PLA) samples was investigated. Chemical-induced crosslinking method was adopted and crosslinking structures were successfully achieved in the presence of dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC). Originally it was commonly suggested that crosslinking would block the motion of chains, thus hindering the crystallization process. However, our results indicate that low or moderate crosslinking bundles (not complete polymer network) can promote the crystallization of PLA samples to some extent. With further increasing crosslinking degree (from 12.1% to 41.2%), although the onset crystallization temperature can be increased as well, the perfection of crystal lamellas is inferior. Based on the experimental results, a schematic model is proposed.

Highly toughened poly(vinylidene fluoride)/nitrile butadiene rubber blends prepared via peroxide-induced dynamic vulcanization

Nitrile butadiene rubber (NBR) toughened poly(vinylidene fluoride) (PVDF) blends were prepared via dynamic vulcanization in the presence of dicumyl peroxide (DCP). A super toughened PVDF/NBR blend was achieved with 28 wt% NBR, showing Izod impact strength of 77.5 kJ/m2, which was 6–7 times higher than the pure PVDF. The effects of the NBR incorporation on morphology and properties of the blends were investigated. Good interfacial interaction was found between the PVDF continuous phase and crosslinked spherical NBR particles with diameter of 1–3 μm. The complex viscosity and storage modulus of the blends increased significantly with increasing NBR content. The incorporation of the NBR component decreased the thermal stability of the PVDF/NBR blends, while the mass of residual char of the blends was much higher than that of pure PVDF and NBR.

Morphology, rheology, crystallization behavior, and mechanical properties of poly(lactic acid)/poly(butylene succinate)/dicumyl peroxide reactive blends

ABSTRACTThe reactive blends were prepared by the blending of poly(lactic acid) (PLA) with poly(butylene succinate) (PBS) in the presence of dicumyl peroxide (DCP) as a radical initiator in the melt state. The gel fractions, morphologies, crystallization behaviors, and rheological and mechanical properties of the reactive blends were investigated. Some crosslinked/branched structures were formed according to the rheological measurement and gel fraction results, and the crosslinked/branched structures played the role of nucleation site for the reactive blends. The PLA–PBS copolymers of the reactive blends acted as a compatibilizer for the PLA and PBS phases and, hence, improved the compatibility between the two components. Moreover, it was found that the reactive blends showed the most excellent mechanical properties as the DCP contents were 0.2 and 0.3 phr. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39580.

Investigation on multifunctional monomer modified polypropylene and its foamability

ABSTRACT1,6‐Hexanediol diacrylate (HDDA), pentaerythrithyl tetramethacrylate (PETMA), and triallyl‐isocyanurate (TAIC) were used as representative monomers to modify polypropylene (PP) in the presence of dicumyl peroxide (DCP) in a mixer. Fourier transformed infrared spectroscopy (FTIR) results confirmed that all the three polyfunctional monomers have been grafted on PP backbone. The shape of torque curves suggested the occurrence of grafting and/or crosslinking structure. The rheological behaviors of HDDA modified PP showed the highest G′ and lowest tan δ at low frequency, shear‐thinning shifted to lower frequency in η*–ω plot, as well as more deviation from semicircle characteristic of linear PP at high viscosity in Cole–Cole plot. And, the improvement of the mechanical properties followed the order as below: TAIC < PETMA < HDDA. Meanwhile, the foamability of the modified PP samples was also investigated. The cellular structure and morphology of the obtained foams were observed by scanning electron microscopy (SEM), and the results indicated that the foamability of the three modified PPs followed the same order, demonstrating HDDA modified PP foam possessed the highest cell density and expansion ratio, and the most well‐defined closed cell structure and uniformly cellular morphology. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1675–1681, 2013

Preparation and Mechanical Properties of the Environmentally Friendly Wood-Plastic Composites

Good bonding at the interface between HDPE (High density polyethylene) and wood flour was achieved by adding MA (Maleic anhydride) as surface-reactive additive and WD-50 (3-aminopropyltriethoxysilane) as coupling agent products. HDPE-g-MA was prepared by melt grafting polymerization in the presence of DCP (Dicumyl peroxide) using a Hakke Rheocord. The FTIR spectra conformed that MA was successfully grafted onto HDPE and the effects of DCP and MA contents on grafting reaction were also studied. The effects of silane coupling agent (WD-50), wood flour and HDPE-g-MA contents on the mechanical properties of the HDPE-based wood-plastic composites were investigated by electronic tensile tester and impact test enginery. The results indicated that WD-50 (with the content of 2 wt%) and HDPE-g-MA (with the content of 10 wt%) effectively improved mechanical properties of the composite materials.

Morphology and mechanical properties of ethylene‐vinyl acetate rubber/polyamide thermoplastic elastomers

AbstractHigh performance thermoplastic elastomers based on ethylene‐vinyl acetate rubber (EVM) and ternary polyamide copolymer (tPA) were prepared through a dynamic vulcanization process in the presence of dicumyl peroxide (DCP). The morphology, crystallization, and mechanical properties of the EVM/tPA blends were studied. A phase transition of EVM/tPA blend was observed at a weight ratio of 60/40. The presence of EVM increased the melting enthalpy at the high temperature of tPA, ascribing to the heterogeneous nucleating effect of EVM. The tensile strength of EVM/tPA (70/30) blends was increased up to 20.5 MPa as the DCP concentration increased to 3.5 phr, whereas the elongation at break of the blends kept decreasing as the DCP concentration increased. The addition of ethylene‐acrylic acid copolymer (EAA) or maleic anhydride‐grafted EVM (EVM‐g‐MAH) to the EVM/tPA blends both induced finer dispersion of the EVM particles in the tPA phase and improvement in the tensile strength and elongation at break of the blends, which were ascribed to the compatibilization of EAA or EVM‐g‐MAH. Finally, a high performance EVM/tPA (70/30) thermoplastic elastomer with Shore A hardness of 75, tensile strength of 24 MPa, elongation at break of 361%, and set at break of 20% was obtained by adding 5 wt % of EVM‐g‐MAH and 3.5 phr DCP. It has great potential in automotive and oil pipeline applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation of long-chain branching polypropylene and investigation on its foamability

In this work, zinc N,N-dimethyldithiocarbamate (ZDMC) was used to mediate the melt modification of polypropylene (PP) with 1,6-hexanediol diacrylate (HDDA) in an internal mixer in the presence of dicumyl peroxide (DCP). Fourier transformed infrared spectroscopy analysis revealed that HDDA was directly grafted onto PP backbone. The dependence of torque on processing time indicated that the presence of ZDMC restrained the degradation of PP, and the end-torque value increased with the addition of ZDMC. Dynamic rheological measurement indicated that the modified PP possessed higher G′ and lower tan δ at low frequency, displaying an increase in η* and disappearance of Newtonian plateau in η*–ω plot, as well as larger radius of semicircle in Cole–Cole plot. All the rheological characterizations, together with the decreased gel content with the increase of ZDMC, confirmed the formation of long-chain branching. Subsequently, the foamability of the modified samples was investigated by one-step compression–molding process. The cellular structure and morphology of the obtained foams were observed by scanning electron microscopy, and the results showed that the addition of ZDMC decreased the cell size, increased the cell density, and brought about well-defined closed cell structure. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Study of rheological and mechanical properties of ternary blends of iPP/LDPE/EPDM

Abstract Compatible blends of isotactic polypropylene (iPP)/low-density polyethylene (LDPE)/ethylene-propylene-diene monomer (EPDM) were prepared by reactive blending in the presence of dicumyl peroxide (DCP). The blends were characterized using different techniques: dynamical rheological analysis (DRA), differential scanning calorimetry (DSC), optical microscopy (OM) and scanning electron microscopy (SEM), dynamical mechanical thermal analysis (DMTA), viscosity and impact strength, to evaluate their properties. Results revealed that the presence of the peroxide in LDPE/EPDM blends gives rise to crosslinking reactions, as is the case in iPP/LDPE/EPDM blends. However, in the latter case, scission reactions of the iPP component also take place. As a consequence of the whole process, morphological changes arise mainly in the amorphous regions, without affecting the degree of crystallinity of the components. The mechanical properties of the blends are consequently improved, due to the crosslinked network thus formed in the blends.

Rheologic studies on chemical cross-linking kinetics for LDPE

Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide (DCP) was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry (DSC) technique with different heating rates. The kinetic parameters of crosslinking reaction were calculated by both rheological and DSC measurements. The results reveal that with the increase of DCP contents, the apparent activation energy, E a, ranges from about 140 kJ/mol to 170 kJ/mol and the order of crosslinking reaction, \(\bar n\), approaches unity. The influence of measurement frequency, ω, on crosslinking reaction was also investigated. It can be found that \(\bar n\) does not change with the increase of ω, and E a decreases slightly with the increase of ω.

Effect of monomer-treated inorganic fillers on mechanical, rheological, and thermal properties of LLDPE nanocomposites

This article discusses the role of nanoscale calcium carbonate (nCC) surface treatment in affecting the mechanical, rheological, and thermal properties of linear low-density polyethylene (LLDPE). The mechanical tests indicated that nCC could simultaneously reinforce and toughen LLDPE. In addition, the composite sample with methacrylic acid (MA)-treated nanoparticles shows further increased mechanical properties as compared to unmodified nanoparticles. In the presence of dicumyl peroxide (DCP), a small amount of MA could increase markedly the mechanical properties of LLDPE/nCC composites. The results of rheological property analysis indicated that the viscosity increased with increasing amount of the filler, especially at low shear rates, but showed a substantial reduction with increasing concentration of the reactive monomer. The thermal behavior of these materials is evaluated by differential scanning calorimetry and thermogravimetric analysis. The addition of a small amount of MA and DCP enhances the stabilization of the blends.

Grafting maleic anhydride onto EVA and effect on the physical and rheological properties of PETG/EVA‐g‐MAH blends

AbstractMaleic anhydride (MAH) was grafted onto ethylene vinyl acetate copolymer (EVA) in the internal mixer in the presence of dicumyl peroxide (DCP), and a prepared reactive compatibilizer, MAH‐g‐EVA, was blended with Poly (ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG). The gel content determination and element analysis (EA) was performed to confirm the grafting reaction. It was found that grafting reaction of MAH on to EVA could compete with crosslinking reaction of DCP during the modification process. In addition, the introduction of small amount of MAH showed a great effect on reducing gel content by decreasing crosslink reaction. As MAH content increased, grafted MAH concentration increased, whereas the grafting yield decreased. It was also confirmed that MAH‐g‐EVA acted as a reactive compatibilizer in the blend with PETG, and enhanced compatibility by reacting with the hydroxyl end groups, OH, of PETG. Addition of EVA in the blend leads a plastic deformation of PETG, and MAH had a great effect on enhancing interfacial adhesion resulting in significant increasing of % strain; however, improved compatibility could not be changed much in low strain tensile strength and Young's modulus. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Grafting of maleic anhydride on poly(L-lactic acid). Effects on physical and mechanical properties

Maleic Anhydride (MAH) was grafted onto poly(L-lactic acid) (PLLA) in the presence of dicumyl peroxide (DCP) as a radical initiator. The effect of the MAH and DCP concentrations on the grafting and the physical and mechanical properties of PLLA films were investigated. The glass transition temperature and crystallinity significantly decreased with addition of MAH. The thermal decomposition of the PLLA films was affected by the MAH content while the mechanical properties were almost unchanged. A slight increase in molecular weight was found, which could be attributed to either the MAH branching reaction or a possible crosslinking reaction between the PLLA chains increasing the chain entanglements.

In-situ monitoring by fibre-optic NIR spectroscopy and rheometry of maleic anhydride grafting to polypropylene in a laboratory scale reactive extruder

The graft copolymerisation of maleic anhydride (MAH) onto polypropylene (PP) has been studied in situ by interfacing a laboratory scale mini-extruder/processor with a near-infrared (NIR) spectrometer via a fibre optic link. Apparent viscosity was measured simultaneously with the NIR spectra. The graft reaction was carried out at several temperatures with and without the initiator, dicumyl peroxide (DCP). Analysis of the NIR spectra showed the reaction to be first order with respect to MAH, and that the graft reaction rate was not affected by the presence of DCP. However, DCP caused a large increase in chain scission reactions leading to a dramatic drop in apparent viscosity. In the absence of DCP, scission reactions occurred at a slower rate and the apparent viscosity remained steady, after an initial drop, for about 15 min during the early part of the reaction. We suggest that a possible explanation for this might be a “repair mechanism” involving the reaction of two PP macro-radicals with a single MAH moiety, thus maintaining the molecular weight. Once the concentration of MAH drops, this reaction becomes less significant and scission reactions dominate.

Free radical graft modification of polyethylene with methacrylic acid and styrene monomer

Polar groups can be introduced on polyethylene by using polar monomer like acryl amide, acrylic acid and methacrylic acid. In present work binary monomer mixture of methacrylic acid and styrene were grafted onto low density polyethylene in the presence of dicumyl peroxide (DCP) as an initiator. Grafted polyethylene was characterized by using differential scanning calorimetry (DSC), melt flow Indexer (MFI) and Fourier transform infrared spectroscope (FTIR). Low value of MFI as compared to virgin polyethylene, presence of carbonyl peaks in the spectrum of grafted polyethylene and higher endothermic peaks in thermogram of grafted polyethylene confirmed grafting of methacrylic acid and styrene onto polyethylene. MFI values at different loads were used for further rheological study of virgin & grafted polyethylene. Key words: Degree of grafting, Meth acrylic acid, Free radical, Vinyl monomer, DCP DOI: http://dx.doi.org/10.3329/cerb.v15i1.7419 Chemical Engineering Research Bulletin 15 (2011) 34-38

Micro-Structure and Fracture Behavior of High-Melt-Strength PPs Prepared by Reactive Extrusion

In this study, high-melt-strength polypropylenes (PPs) were prepared by reactive extrusion of PP and varied amount of divinylbenzene in the presence of dicumyl peroxide and an antioxidant, and the dynamic rheological behavior, crystalline morphology, and fracture behavior of the resultant materials were investigated. It was found that at relatively low frequency, with the cross-linking and branching structures increasing, the complex viscosity of the melt of the modified PP increased significantly and then leveled off. The modulus of the melt, particularly the storage modulus, increased. The storage moduli of the melts with higher content of cross-linking and branching structures were higher than the loss modulus in the whole range of testing frequency, indicative of a completely elastic behavior. The crystallinity and the size of spherulites of the modified PP decreased, while the number of spherulites increased. The specific essential work of fracture and the specific non-essential work of fracture of the modified PP were found to be reduced compared with pure PP, but the specific essential work of fracture showed an increasing trend with the cross-linking and branching structures increasing.

Reactive Blending of Thermoplastic Polyurethane and Polypropylene

Abstract In this research, reactive blending of thermoplastic polyurethane (TPU) and polypropylene (PP) was studied. Grafting of maleic anhydride (MAH) onto TPU/PP blends was performed by a twin-screw extruder in the presence of dicumyl peroxide (DCP). Mechanical properties and morphology of the blends were investigated by tensile testing and scanning electron microscopy (SEM), respectively. Thermal properties of the blends were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The obtained results were compared with those of the uncompatibilized blends and the blends compatibilized with a commercial maleic anhydride grafted polypropylene (PP-g-MA). The results from the uncompatibilized blends clearly indicate that the TPU and PP are immiscible resulting in undesirable properties of the blends. These properties were improved significantly when TPU and PP were reactive-blended in the presence of MAH and DCP. When comparing with the blends compatibilized with PP-g-MA, the blends prepared by the reactive blending technique possessed better mechanical properties.

FTIR study of the melt grafting of high density polyethylene with amino, sulfonate, and mercapto esters

High-density polyethylene (HDPE) was melt-functionalized with three different esters at 160oC in the presence of dicumyl peroxide (DCP), a free radical initiator, under nitrogen atmosphere at different % weight loadings of esters. DCP and the esters were taken for the melt functionalization reaction in 1:1 ratio. FTIR spectroscopy was used to determine the % grafting of esters onto the HDPE backbone quantitatively. Diethyl mercaptosuccinate (DEMS) produced the highest % grafting with lowest % cross-linking values, whereas anthranilic acid cinnamoyl ester (AACE) yielded the highest % cross-linking with the lowest % grafting values.

Biodegradation of flax fiber reinforced poly lactic acid

Woven and nonwoven flax fiber reinforced poly lactic acid (PLA) biocomposites were prepared with amphiphilic additives as accelerator for biodegradation. The prepared composites were buried in farmland soil for biodegradability studies. Loss in weight of the biodegraded composite samples was determined at different time intervals. The surface morphology of the biodegraded composites was studied with scanning electron microscope (SEM). Results indicated that in presence of mandelic acid, the composites showed accelerated biodegradation with 20-25% loss in weight after 50-60 days. On the other hand, in presence of dicumyl peroxide (as additive), biodegradation of the composites was relatively slow as confirmed by only 5-10% loss in weight even after 80-90 days. This was further confirmed by surface morphology of the biodegraded composites. We have attempted to show that depending on the end uses, we can add differ- ent amphiphilic additives for delayed or accelerated biodegradability. This work gives us the idea of biodegradation of materials from natural fiber reinforced PLA composites when discarded carelessly in the environment instead of proper waste disposal site.

Melt functionalization of linear low-density poly(ethylene) with succinimide andN-hydroxy succinimide by thermolysis method

Linear low-density polyethylene (LLDPE) was functionalized with succinimide under different experimental conditions like change in time, temperature, and (% weight of succinimide). The FTIR Spectrum inferred that melt grafting of succinimide onto LLDPE followed the 0.50 order of reaction with respect to (% weight of succinimide). DSC was used to analyze the (melting temperature) Tm and (crystallization temperature) Tc values of functionalized LLDPE. Free radical mechanism explained the formation of nitroxide radical during the melt functionalization of N-hydroxy succinimide (NHS) with LLDPE in the presence of dicumyl peroxide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010