Synergistic effect of supported nickel catalyst with intumescent flame-retardants on flame retardancy and thermal stability of polypropylene

Supported nickel catalyst (Ni-Cat) was used as a catalyst to improve the flame retarclancy of intumescent flame-retardants (IFR) systems based on ammonium polyphosphate and pentaerythritol (PETOL) in polypropylene (PP) matrix. Limited oxygen index (LOI), UL-94 rating, and thermogravimetric analysis were used to characterize the flame retardancy and thermal stability of the PP systems, and field emission scanning electron microscopy (FE-SEM) and Fourier transformed infrared spectroscopy (FTIR) were used to analyze the microstructure and composition of the chars formed during measuring LOI value and after combustion at 800 degrees C. The catalytic effect of NiCat was shown in an increase of LOI, a change in the char microstructure, and improvement of the thermal stability in the PP systems, which result from the synergistic effect of Ni-Cat and IFR. The results from FE-SEM and FTIR spectra of the char can explain how this synergistic effect happened.

Neodymium oxide-assisted melt free-radical grafting of maleic anhydride on isotactic-polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd2O3), -assisted melt free-radical grafting of maleic anhydride (MAH) on isotactic-polypropylene (i-PP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 into reactive system leads to an enhancement of the grafting degree of MAH, along with an elevated degradation of i-PP matrix. When Nd2O3 content is 4.5 mmol %, the increment of the grafting degree of MAH (maximally) is up to about 30% compared with that of the related system without adding Nd2O3, while the severest degradation of i-PP matrix simultaneously occurs. On the basis of the reaction mechanism of PP-g-MAH proposed before, the sequence of beta-scission and grafting reaction is discussed in detail. It is found that, for the reactive system studied, most tertiary macroradicals first undergo beta-scission, and then, grafting reaction with MAH takes place at the new radical chain ends. The imported Nd2O3 has no effect on the aforementioned reaction mechanism, whereas it enhances the initiating efficiency of the initiator, dicumyl peroxide (DCP).

Compatibilization of PP/EPDM blends by grafting acrylic acid to polypropylene and epoxidizing the diene in EPDM

In this article, ethylene-propylene-diene-rubber (EPDM) was epoxidized with an in situ formed performic acid to prepare epoxided EPDM (eEPDM). The eEPDM together with the introduction of PP-g-AA was used to compatibilize PP/EPDM blends in a Haake mixer. FTIR results showed that the EPDM had been epoxidized. The reaction between epoxy groups in the eEPDM and carboxylic acid groups in PP-g-AA had taken place, and PP-g-EPDM copolymers were formed in situ. Torque test results showed that the actual temperature and torque values for the compatibilized blends were higher than that of the uncompatibilized blends. Scanning electron microscopy (SEM) observation showed that the dispersed phase domain size of compatibilized blends and the uncompatibilized blends were 0.5 and 1.5 mu m, respectively. The eEPDM together with the introduction of PP-g-AA could compatibilize PP/EPDM blends effectively. Notched Izod impact tests showed that the formation of PP-g-EPDM copolymer improved the impact strength and yielded a tougher PP blend.

Fe(2-EHA)(3)/Al(i-Bu)(3)/hydrogen phosphite catalyst for preparing syndiotactic 1,2-polybutadiene

Polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene with art iron(III) catalyst system has been investigated. Activity of the catalyst was affected by the type of cocatalyst alkylaluminum and the phosphorus compound as an electron donor, molar ratio of catalyst components, and their aging sequence and aging time of the catalyst. The microstructure and configuration of the polymer was decided by the catalyst components, the higher [Al]/[Fe] molar ratio tending to yield syndiotactic 1,2-polybutadiene, while the higher [P]/[Fe] molar ratio favors the formation of amorphous 1,2-polybutadiene.

Monte Carlo simulation of the grafting of maleic anhydride onto polypropylene at higher temperature

The graft of maleic anhydride (MAH) onto isotactic polypropylene (iPP) initiated by dicumyl peroxide (DCP) at 190 degreesC was studied by means of the Monte Carlo method. The ceiling temperature theory, i.e., no possibility for the homopolymerization of MA-H to occur at higher temperatures, was used in this study. The simulation results show that most MAH monomers were grafted onto the radical chain ends arising from beta scission at a lower MAH concentration, whereas the amount of MAH monomers attached to the tertiary carbons was much larger than that grafted onto the radical chain ends at a higher MAH concentration for various DCP concentrations. This conclusion gives a good interpretation for the disagreement on the grafting sites along a PP chain. Moreover, it was found that the grafting degree increased considerably up to a peak value; thereafter, it decreased continuously with increasing MA-H concentration. The peak shifted in the lower MAH concentration direction and became lower and lower with increasing DCP concentration. When the DCP concentration was below 0.1 wt %, the peak was hardly observed. Those results are in good agreement with the experiments.

Effects of surfactant loadings on the dispersion of clays in maleated polypropylene

A series of organically modified clays (OMCs) with a surfactant loading range from 0.625 to 2.5 times the cation exchange capacity (CEC) were melt-mixed with maleated polypropylene (PPMA). Wide-angle X-ray diffraction and transmission electron microscopy results of these narrocomposites show that dispersion of clays becomes unfavorable in the PPMA matrix during melt intercalation as the surfactant loading increases in the process of modifying clays, though larger interlayer distances are obtained in their corresponding OMCs. It is even important that clays uniformly disperse at the nanoscale level in the PPMA matrix when the surfactant loadings are below the CEC, which implies that incomplete exchange of inorganic cations in the process of modifying clay benefits the dispersion of clays in the PPMA matrix.

Compatibilization of polyamide-6/syndiotactic polystyrene blends using styrene/glycidyl methacrylate copolymers

Blends of polyamide-6 (PA6) with syndiotactic polystyrene (sPS) were prepared using a series of styrene/glycidyl methacrylate (SG) copolymers as compatibilizers. These copolymers are miscible with sPS, and the epoxide units in SG are capable of reacting with PA6 end groups. These copolymers thus have the potential to form SG-g-PA6 graft copolymers at the PA6/sPS interface during melt processing. This study focuses on the effects of functionality and concentration of the compatibilizer on the morphological, mechanical and crystallization behaviors of the blends.. In general, SG copolymers are effective in reducing the sPS domain size and improving the interfacial adhesion. About 5 wt% glycidyl methacrylate (GMA) is the optimum content in SG copolymer that produces the best compatibilization. Both the strength and modulus of the blend have been improved on addition of the SG copolymers, accompanying a loss in toughness when higher concentration copolymer is added. Incorporation of SG compatibilizers to PA6/sPS blend has little influence on the crystallization behavior of PA6 component but resulted in a steady reduction in intensity of crystallinity peak of sPS and simultaneous crystallization of sPS with PA6 is observed.

Characterization of the microstructure of biaxially oriented polypropylene using preparative temperature-rising elution fractionation

Two commercial biaxially oriented polypropylene (BOPP) resins, resin A and resin B, having different processing properties, were fractionated by preparative temperature-rising elution fractionation (TREF). The TREF fractions were further characterized by gel permeation chromatography (GPC), gel permeation chromatography coupled with light scattering (GPC-LS), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). GPC-LS did not find visible long-chain branching in either resin A or B. The results from TREF and DSC indicate that the fractional melting parameter f(T) may be used to predict the profile of the TREF cumulative weight distribution curve. GPC results show that the molecular weights of the fractions tend to increase with elution temperature. WAXD and DSC data show that the crystallinity of fractions does not increase monotonically with increase of elution temperature. There appears to be a maximum in the plot of crystallinity versus elution temperature. The high-speed BOPP resin A has a lower isotacticity but a homogeneous isotacticity distribution and a higher molecular weight but a broader molecular weight distribution than resin B.

Synthesis and characterization of polypropylene/montmorillonite nanocomposites via an in-situ polymerization approach

Polypropylene/montmorillonite (PP/MMT) nanocomposites were prepared by in-situ polymerization using a MMT/MgCl2/TiCl4-EB Ziegler-Natta catalyst activated by trietbylaluminum (TEA). The enlarged layer spacing of MMT was confirmed by X-ray wide angle diffraction (WAXD), demonstrating that MMT were intercalated by the catalyst components. X-ray photoelectron spectrometry (XPS) analysis proved that TiCl4 was mainly supported on MgCl2 instead of on the surface of MMT The exfoliated structure of MMT layers in the PP matrix of PP/MMT composites was demonstrated by WAXD patterns and transmission electron microscopy (TEM) observation. The higher glass transition temperature and higher storage modulus of the PP/MMT composites in comparison with pure PP were revealed by dynamic mechanical analysis (DMA).

Multiple melting behavior of isotactic polypropylene and poly(propylene-co-ethylene) after stepwise isothermal crystallization

The multiple melting behavior of several commercial resins of isotactic polypropylene (iPP) and random copolymer, poly(propylene-co-ethylene) (PPE), after stepwise isothermal crystallization (SIC) were studied by differential scanning calorimeter and wide-angle X-ray diffraction (WAXD). For iPP samples, three typical melting endotherms appeared after SIC process when heating rate was lower than 10 degreesC/min. The WAXD experiments proved that only alpha-form crystal was formed during SIC process and no transition from alpha1- to alpha2-form occurred during heating process. Heating rate dependence for each endotherm was discussed and it was concluded that there were only,two major crystals with different thermal stability. For the PPE sample, more melting endotherms appeared after stepwise isothermal crystallization. The introduction of ethylene comonomer in isotactic propylene backbone further decreased the regularity of molecular chain, and the short isotactic propylene sequences could crystallize into gamma-form crystal having a low melting temperature whereas the long sequences crystallized into alpha-form crystal having high melting temperature.

Study of PVT behavior of biaxially oriented polypropylene resins in the melting state

The PVT data of five kinds of biaxially oriented polypropylene (BOPP) Resins was measured by the PVT-100 apparatus. Thermal expansion coefficients (alpha) and isothermal compressibility (beta) were evaluated from Tait equation in the melting state and then compared with those fitted with the value of experiment. The results showed that it was reasonable to calculate alpha and beta with Tait equation in the melting state. At the same time, it was found that thermal expansion coefficients, isothermal compressibility and the melting temperature (T-m) of one of BOPP melts (S28C) were lower than those of the others in the same test conditions, indicating that the volume deformation of S28C resin is' less so that it could be realized to avoid arising surface defects of the film (biaxially oriented polypropylene film) due to. contracting, thereby decrease damage to the film in the subsequence process. Accordingly superior processing properties of S28C resin are confirmed from PVT. speciality.

The influence of nucleating agent on crystallization behavior and properties of polypropylene and its copolymer with ethylene

The influences of nucleating agent EDBS on crystallization behavior and properties of polypropylene UP) and its copolymer with a small amount (4. 48 %, molar fraction) of ethylene (CPP) were studied. DSC results indicated that the crystallization temperature of iPP and CPP samples with 0.5 % (mass fraction) EDBS obviously increased and the degree of crystallinity of these samples became higher. In addition, adding small amount of EDBS enhanced the crystallization of the low isotacticity and low molecular weight segments of the CPP. PLM results showed that their spherulite size decreased markedly, and as a result, the transmittance and haze of the films were all improved.

A novel preparation method of maleic anhydride grafted syndiotactic polystyrene and its blend performance with nylon6

This work is intended to provide a method for the preparation of maleic anhydride grafted syndiotactic polystyrene (sPS-g-MA). In particular, a novel solid reaction method by a radical grafting approach is investigated. The grafting reaction is performed at a solid state, where the syndiotactic polystyrene (sPS) is swollen in solvent at relatively low temperature compared to the conventional melt modification method. The formation of sPS-g-MA is directly confirmed by Fourier transform infrared spectroscopy and by the morphology observation of sPS/polyamide-6 (Nylon6) blends, when sPS-g-MA is used as a reactive compatibilizer.

Oriented crystallization process of polypropylene fractions

Melting recrystallization processes of melt-sheared films of polypropylene (S28C) fractions have been investigated in situ by polarized optical microscope equipped with CCD camera and hot-stage. Actually, the morphological developments in the melting recrystallization are partially reappearance of oriented crystallization processes during melt-shearing the fractions, which is due to a memory effect of oriented structure of polymer. For low molecular weight fraction, only incomplete spherulites with some orientation along shear direction are observed in the melting recrystallization processes of the sheared films. For middle molecular weight fractions, extended chain fiber crystals(or bands) are formed first at higher temperatures, and the bands can act as self-nuclei (i. e., row nuclei), resulting in epitaxial growth of chain-folded lamellae(or fibril), i. e., the formation of cylindrites, with further decrease of the crystallization temperature. For high molecular weight fraction, however, it is not possible to shear the melt film because of its high melt viscosity. When the low molecular weight fraction in which no fiber crystals or cylindrites are observed, are mixed with small amount(about 1%-2%) of the high molecular weight fraction, quite large number of cylindrites are formed during the melting recrystallization process of its sheared film, which implies that the component of high molecular weight plays an important role in the formation of cylindrites during the shear process of polypropylene.

Compatibilization of side-chain, thermotropic, liquid-crystalline ionomers to blends of polyamide-1010 and polypropylene

A novel side-chain, liquid-crystalline ionomer (SLCI) with a poly(methyl hydrosiloxane) main chain and side chains containing sulfonic acid groups was used in blends of polyamide-1010 (PA1010) and polypropylene (PP) as a compatibilizer. The morphological structure, thermal behavior, and liquid-crystalline properties of the blends were investigated by Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. The morphological structure of the interface of the blends containing SLCI was improved with respect to the blend without SLCI. The compatibilization effect of greater than 8 wt % SLCI for the two phases, PA1010 and PP, was better than the effects of other SLCI contents in the blends.