Flame retardation of polypropylene: Effect of organoantimony compounds on the melt flow behavior

The melt flow behaviour of polypropylene filled with organoantimony compounds, triphenylstibinedibromide and its derivatives with tribromo-, trichloro-, and pentachloro-phenols, as flame retardants has been studied in the temperature range of 180 to 220°C, and at shear rates of 29.5 to 588.8's^?1, using a capillary rheometer. A decrease in the melt viscosity at all shear rates and temperatures was noticed on addition of these flame retardants, The melt viscosity further decreased upon increasing the concentration (from 5 to 20 phr) of the flame retardants. The die swell was measured in order to determine the melt elasticity of the filled systems. The minimum melt viscosity of filled propylene was observed approximately where the maximum die swell (melt elasticity) occurred.     

Flame retardation of polypropylene: Effect of organoantimony compounds on the flammability and thermal behavior

Triphenylstibinedibromide and its derivatives with tribromo-, and pentachlorophenols have been used as flame-retardant additives for polypropylene. Maximum limiting oxygen index of 31.5 against 18.2 for unfilled polypropylene was obtained in a sample containing 10 phr of triphenylstibinedibromide. However, V-0 rating in UL-94 test was observed in 20 phr flame-retardant-filled polypropylene sample, while V-2 rating was obtained even at 5 phr flame-retardant level. Thermal behavior of flame-retardant-filled polypropylene was also studied in air atmosphere by thermogravimetric analysis, and an attempt has been made to correlate the flammability with the thermal behavior. The residue obtained in isothermal treatment at 450°C for 1/2 hour in air was analyzed for antimony and halogen which establishes the role of these flame retardants in vapor phase.     

Effect of surface coverage of silane treated CaCO3 on the tensile properties of polypropylene composites

Polypropylene (PP) composites were prepared with a constant volume fraction of a CaCO₃ filler, which was treated with eight trialkoxy functional silane coupling agents and the routinely used stearic acid, as comparison, The tensile properties of the composites were determined as a function of surface coverage and the chemical composition of the coupling agent. Significant differences were detected in the effect of the silane coupling agents on the tensile properties of the composites studied. They could be classified into groups of reactive, nonreactive and inactive compounds, in accordance with an earlier study. Moreover, tensile properties proved to be very sensitive to surface treatment. Reactive coupling leads to a maximum in tensile strength, while the use of nonreactive agents decreases strength rapidly with increasing surface coverage. The rate of strength decrease slows down above the concentration necessary for the formation of a monolayer coverage. Treatment influences deformability accordingly, it decreases on reactive coupling, while agents with a surfactant effect increase elongation. Amino functional silanes show a strong reactive coupling effect. A trialkoxy derivative of stearic acid, (3-stearyloxy-propyl-triethoxy-silane), synthesized the first time in our laboratory, has an outstanding surfactant effect; its use increases both the elongation and the tensile strength of the composites. Both characteristics exceed the corresponding properties of the reference composite containing the filler treated with stearic acid.     

Effect of silane KH‐550 to polypropylene/brucite composite

The effect of the KH‐550 type silane coupling agent on the properties of polypropylene (PP)/brucite (BC) composite was studied. X‐ray diffraction, scanning electron microscope, and polarization optical microscope indicated that morphology structure of PP changed with the addition of KH‐550, which activated the heterogeneous nucleation centers on BC surface, which made the distribution of the spherulite diameter become narrow and uniform, and improved the dispersibility of BC in the matrix. Therefore, KH‐550 enhanced the interfacial adhesion of matrix‐filler and improved the compatibility of the PP/BC composite, when KH‐550's content was 2.9% the tensile strength and impact strength increased approximately by 90% and by 30%, respectively than PP/BC. Flow tests and IR proved that some reactions took place between BC and KH‐550. All the investigations showed KH‐550 was a proper coupling agent in the PP/BC composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of silane coupling agents on the properties of pine fibers/polypropylene composites

In the present work, PP‐based composites, reinforced with surface modified pine fibers, have been prepared. The surface of the fibers has been treated with several silane derivatives bearing specific functionalities. ? NH₂, ? SH, long aliphatic chain, and methacrylic group were chosen as functionalities of the silane derivatives for evaluating the compatibility with the polymer matrix. Mechanical analysis, contact angle and XPS spectra, SEM microscopy, and water uptake measurements were used as characterization techniques for evaluating the nature of composites. XPS as well as contact angle measurements demonstrated that pine fibers and silane derivatives were effectively coupled. The mechanical analysis showed an increase in Young's and flexural moduli, by 12% and 130% respectively, and nonsignificant changes in the ultimate tensile strength were noted after surface modification. Water uptake measurements revealed a low water absorption by the materials, always lower than 2 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3706–3717, 2007     

Flame retardation and thermal degradation of intumescent flame‐retarded polypropylene composites containing spirophosphoryldicyandiamide and ammonium polyphosphate

A novel halogen‐free intumescent flame retardant, spirophosphoryldicyandiamide (SPDC), was synthesized and combined with ammonium polyphosphate (APP) to produce a compound intumescent flame retardant (IFR). This material was used in polypropylene (PP) to obtain IFR‐PP systems whose flammability and thermal behavior were studied by the limiting oxygen index (LOI) test, UL‐94, thermogravimetric analysis, and cone calorimetry. In addition, the mechanical properties of the systems were investigated. The results indicated that the compound intumescent flame retardant showed both excellent flame retardancy and antidripping ability for PP when the two main components of the IFR coexisted in appropriate proportions. The optimum flame retardant formulation was SPDC:APP = 3:1, which gave an LOI value of 38.5 and a UL‐94 V‐0 rating. Moreover, the heat release rate, production of CO, smoke production rate, and mass loss rate of the IFR‐PP with the optimum formulation decreased significantly relative to those of pure PP, according to the cone calorimeter analysis. The char residues from the cone calorimetry experiments were observed by scanning electron microscopy, which showed that a homogeneous and compact intumescent char layer was formed. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Flame retardation and thermal degradation of flame‐retarded polypropylene composites containing melamine phosphate and pentaerythritol phosphate

The flame retardation of polypropylene (PP) composites containing melamine phosphate (MP) and pentaerythritol phosphate (PEPA) was characterized by limiting oxygen index (LOI) and UL 94. The morphology of the char obtained from the combustion of the composites was studied by scanning electron microscopy (SEM). The thermal degradation of the composites was investigated using thermogravimetric (TG) analysis and real‐time Fourier transform infrared (RTFTIR) spectroscopy. It has been found that the PP composites containing only MP do not show good flame retardancy even at 40% additive level. Compared with the PP/MP binary composites, all the LOI values of the PP/MP/PEPA ternary composites at the same additive loading increase, and UL 94 ratings of the ternary composites at suitable MP/PEPA ratios are raised to V‐0 from no rating (PP/MP). The TG and RTFTIR studies indicate that the interaction occurs among MP, PEPA and PP. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of polymeric silane coupling agents on adhesion of polypropylene and polystyrene to glass

The coupling performance of some polymeric silane compounds was compared with that of the monomeric silanes for adhesion of polypropylene (PP) and polystyrene (PS) to glass. A silylated poly-1,2-butadiene was found to be effective for PP and, on the other hand, some copolymers derived from styrenyl triethoxysilane or γ-methacryloxypropyl trimethoxysilane for PS. Benzoyl peroxide also showed a pronounced effect on the adhesion of PP, rather than that of PS. The adhesion strength was approximately correlated with the contact angles of the resin melts on the coated glass, intensively suggesting the dependence of compatibility between resinous matrix and coupling agent on the adhesion. Their critical surface tensions, thermal behavior, and infrared spectra were also measured to discuss the relationship between the surface constitution and the adhesion effect.     

The retardation of reinforcing steel corrosion by alkyl-alkoxyl silane

The effectiveness of an alkyl-alkoxy silane treatment of concrete on reducing the rate of corrosion of reinforcing steel in the presence of chloride ions was investigated. First, the penetrating characteristics of the alkyl-alkoxy silane into dried concrete were determined. Then, the corrosion currents of 90 corrosion specimens, some of which were dried and silane-impregnated, were measured using an impressed current, accelerated corrosion technique. The penetration of alkyl-alkoxy silane into dried concrete followed an approximate linear square root time relationship. Comparisons of corrosion currents showed that alkyl-alkoxy silane showed that allowing time after treatment for the They also showed that allowing time after treatment for the ethanol carrier to evaporate and exposing the treated surface to water for a short period of time were beneficial.     

Flame surface modification of polypropylene film

Contact-angle measurements, the ASTM standard wetting test for polyolefin films, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize flame-treated polypropylene (PP) films. Two combustion models, STANJAN and PREMIX, were then used to determine the chemical and physical properties of the flames used to treat the PP films. Both the flame equivalence ratio and the position of the PP film in the flame are important variables in determining the extent of oxidation and improvement in wettability obtained by flame treating. The optimal equivalence ratio for the flame treatment of PP is 0.93, while the optimal luminous flame-to-film distance is 0-2 mm. Modeling of the combustion processes occurring in the flame provides evidence that the extent of treatment correlates closely with the concentrations of H, O, and OH radicals present in the flame. The extent of surface modification of the flame-treated PP does not appear to correlate with either the flame temperature or the concentraion of oxygen molecules. The mechanism of surface oxidation by flame treatment probably involves polymer-radical formation by O and OH, followed by rapid reaction of the polymer radicals with O, OH, and O₂.     

Properties of polypropylene structural foam crosslinked by vinyltrimethoxy silane

Polypropylene containing the blowing agent azodicarbonate was first grafted with vinyl trimethoxy silane, then crosslinked using the hot water treatment. Two heating stages initiated the blowing agent and formed polypropylene structural foam. The effects of such reaction variables as initiator, cross-linking agent, cross-linking accelerator, and blowing agent on the gel fraction, density, and expansion ratio of polypropylene foam were studied. Furthermore, cell dimension, compression strength, and volume resistivity were also measured and analyzed.     

Effect of oleyl amine on SBR compounds filled with silane modified silica

The effect of oleyl amine on processing and physical properties of SBR compounds filled with silane–silica particles has been evaluated. Two different types of silane molecules have been used as coupling agents to minimize the silica–silica interactions and reduce the formation of secondary structures of silica, in addition with an increment in the filler–rubber interactions. Significant differences between those compounds have been found according with the silane structure. However, in both cases, the dynamic, rheological, and mechanical properties of the filled rubber compounds were improved after the incorporation of oleyl amine molecules. This fact could be related with the capacity of the amine molecules to interact with the free silanol groups of silane‐modified silica forming an amine‐modified silica complex, which reduces the hydrophilic nature of the silica surface. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1806–1814, 2007     

Surface‐activated nanosilica treated with silane coupling agents/polypropylene composites: Mechanical,morphological, and thermal studies

This work reports the mechanical, morphological, and thermal properties of the polypropylene (PP) nanocomposites containing nanosilica (nano‐SiO₂) which were treated by different functional group silane coupling agents. Four types of silane coupling agents namely aminopropyltriethoxy silane (APTES), glycidyloxypropyltrimethoxy silane (GPTMS), trimethoxysilylpropyl methacrylate (TMPM), and dichlorodimethyl silane (DCMS) were used to modify the surface‐activated nanosilica. To enhance the effectiveness of the coupling, nanosilica was chemically activated and analyzed through FTIR and X‐ray photo electron spectroscopy (XPS). The highest tensile strength was recorded by the activated nanocomposites treated with APTES followed by nanocomposite treated with GPTMS, TMPM, and DCMS, respectively. The addition of silane coupling agents into nano‐SiO₂/PP system further improved the tensile modulus of the PP nanocomposites. From the transmission electron microscopy (TEM) analysis, activated nanosilica treated with APTES showed better nanosilica dispersion in the PP matrix and lesser agglomeration occurred when compared with the other silane coupling agents which were used in this study. Surface activation process does not effectively increase the degree of crystallinity and thermal stability on the PP nanocomposites. However, with the assistance of the surface treatment, it was found that the thermal behavior of the PP nanocomposites had been enhanced. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Effect of titanium compounds on thermooxidative properties of stabilized polypropylene

The effect of titanium compounds on thermooxidation stability of stabilized polypropylene was studied. It was found that the presence of titanium compounds shortens the induction period of PP oxidation. This phenomenon is brought about by the thermal reactions of titanium compounds with antioxidants which take place during polymer processing. The first step is the reaction of Ti? Cl with OH groups of phenolic antioxidant, which gives rise to a colored titanate and HCl. Hydrogen chloride functions as a Friedel-Crafts catalyst for degradation and dealkylation of phenolic antioxidants. The products of degradation have a very low stabilization efficiency. Hydrogen chloride acceptors suppress antioxidant degradation and increase the polymer stability even in the presence of small amounts of titanium compounds.     

Crosslinkable polypropylene composites made by the introduction of silane moieties

Silane‐crosslinkable polypropylene (PP) composites containing calcium carbonate (CaCO₃) as a filler have been investigated. The melt grafting of vinyl trimethoxysilane to PP with dicumyl peroxide (DCP) as a radical initiator is demonstrated. The thermal and mechanical properties of the crosslinkable products are also discussed. The results show that two reactions, that is, silane grafting and PP degradation, take place in parallel. The extents of silane grafting and PP degradation strongly depend on the reaction temperature, grafting formulation, and amount of the filler in the systems. Increasing the DCP concentration (up to 0.05 wt %) leads to an increase in the grafting degree. However, when the concentration of radicals is over a certain degree, the dominant reaction is PP chain scission. This results in a drastic decrease in the polymer viscosity. In systems containing both silane and CaCO₃, the viscosity of the polymer is higher than that of a grafted sample without CaCO₃ addition; in other words, the effect of the filler on the polymer viscosity compensates for the effect caused by PP degradation. Differential scanning calorimetry results show that the crystallization starts earlier for grafted samples. The percentage of the crystallinity of grafted PP is higher than that of the pure polymer. The incorporated silane does not have a strong effect on the mobility of the PP chains, as revealed by dynamic mechanical analysis. In comparison with ungrafted composites, the silane‐crosslinkable products show higher tensile stress and modulus. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1476–1483, 2005     

Effect of the silane modification of an organoclay on the properties of polypropylene/clay composites

A commercial clay, Cloisite®20A (C20A) was modified with three different silane compounds, propyltrimethoxy silane, octyltrimethoxy silane, and octadecyltrimethoxy silane, to control the hydrophobicity of C20A. The amount of the silane compounds grafted to C20A was quantified from the weight loss by using TGA, and the hydrophobicity was evaluated by the amount of water absorption. The variation of the interlayer distance was traced by XRD and TEM observation. SEM/EDS was employed to visualize the morphology of the fractured surface and the degree of dispersion of the clay layers in the PP/clay composites. Measurements of the tensile properties of the PP/clay composites indicated that the composite made from PP and the C20A modified with octadecyltrimethoxy silane exhibited the most excellent tensile properties. This was ascribed to the fact that the C20A modified with octadecyltrimethoxy silane possessed the most favorable interfacial interaction with PP and thus the degree of dispersion of the clay layers was the best in the PP matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

硅烷接枝聚丙烯对GMTPP的增容作用及增容机理

为了获得高刚性和高韧性的玻璃纤维毡增强聚丙烯(GMT-PP),首先制备了硅烷接枝聚丙烯(PP-g-Si),研究了PP-g-Si对GMT-PP的增容作用及增容机理.结果表明质量分数低于20%的PP-g-Si,可以提高GMT-PP的拉伸和弯曲性能,而冲击强度几乎没有变化;PP-g-Si对GMT-PP的增容机理为PP-g-Si的甲硅烷基氧与结合在玻璃纤维上的氨基硅烷的氨基相互吸附形成了氢键.     

Effect of chemical structure of silane coupling agent on interface adhesion properties of syndiotactic polypropylene/cellulose composite

To improve interaction between syndiotactic polypropylene (SPP) and fibrous cellulose (FC), effects of chemical structure of silane coupling agent on the reactivity for the surface hydroxyl group on the FC were studied by X‐ray photoelectron spectroscopy (XPS) measurement. Among the three kinds of the silane coupling agent, the 3‐aminopropyltrimethoxysilane (APTMS) showed the highest reactivity with the surface hydroxyl group on the FC, and the linear silane compound with methoxyl group was found to be suitable for the reaction. Although the morphology of the SPP/FC composite is hardly affected by the difference in the kinds of the silane coupling agent, the tensile properties were considerably different. In particular, in the case of using higher silane coupling agent solution (over 3 wt %), the chemical structure of silane coupling agent certainly affected the tensile properties of the SPP/silanized FC composite. It was found that the tensile properties were distinctly affected by the reactivity between the surface hydroxyl group on FC and the silane coupling agent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of interfacial compatibility in wood flour/polypropylene composites by grafting isocyanate silane coupling agent on polypropylene

In this paper, the polypropylene was functionalized by isocyanate silane coupling agent grafted polypropylene (IS-g-PP), various characterization methods were conducted to evaluate the interfacial compatibility of WF/PP. The results indicated that IS-g-PP remarkably enhanced the interfacial adhesion between WF and PP with improved mechanical property, tensile strength was improved by 96.1%, and flexural strength was also increased apparently. According to the DSC results, the crystallization temperature of PP was decreased due to its enhanced interfacial adhesion. Most importantly, the use of IS-g-PP reinforced the storage modulus, loss modulus, and complex viscosity of WF/PP. These results demonstrated that IS-g-PP enhanced the interfacial interaction, and the mobility of PP chain was restrained, and was further confirmed by SEM analysis.     

Mechanism of a one-step method for preparing silane grafting and cross-linking polypropylene

A high-melt-strength polypropylene (HMSPP) with partially cross-linking, modified from a normal isotactic polypropylene (IPP), is prepared by a one-step silane grafting and cross-linking method in a twin-screw reactive extruder. The melt grafting and cross-linking of IPP is achieved by using vinyl unsaturated silane with long chain as a grafting monomer, benzoyl peroxide (BPO) as an initiator, styrene as a coagent, and a little water as a catalyst for cross-linking. By analyzing the difference of the Fourier transformed infrared spectra between raw and modified PP, comparing the variety of the melt flow rate (MFR) and gel percentage between cured and uncured PP samples, and investigating the effect of catalyst on the MFR and gel percentage of modified PP, the partially cross-linked polypropylene in the way of one-step reactive extrusion has been verified. We put forward the reactive mechanism of one-step method based on our experimental results. In this mechanism, the hydrolysis and condensation of silane occur first through the catalysis of water and a compound with two or more double-bond is formed, which then the compound reacts with PP macroradicals to form the partially cross-linked PP. POLYM. ENG. SCI., 47:1004–1008, 2007. © 2007 Society of Plastics Engineers