Structure and morphology of an intumescent polypropylene blend

This article deals with the study of the efficiency of different compatibilizing agents in the intumescent polypropylene/polyamide‐6/ammonium polyphosphate (PP/PA‐6/APP) blend. The migration of additive was first investigated by X‐ray photoelectron spectroscopy. The study showed that ethylene–butyl acrylate–maleic anhydride is not efficient in preventing the exudation of APP to the surface. However, ethylene vinyl acetate (EVA) prevented such a phenomenon. Second, the modifications in the blends were analyzed as a function of their compositions. Optical microscopy analysis showed that adding EVA to PP/PA‐6/APP promoted a decrease in the size of PA‐6 droplets. X‐ray diffraction was used to characterize the effect of each component on the PP crystallinity. It was clearly shown that the crystallinity depends on the composition of the blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 402–411, 2004     

Intumescent flame retardation of melamine‐modified montmorillonite on polyamide 6: Enhancement of condense phase and flame retardance

Melamine‐modified montmorillonite (MA‐MMT) was prepared via cation exchange. The intercalation behavior was investigated by Fourier transform infrared spectrometer (FT‐IR), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffraction (XRD). The results showed that the d‐spacing value increased from 1.25 nm for Na‐montmorillonite (Na⁺MMT) to 1.53 nm for MA‐MMT. Different kinds of montmorillonite combined with melamine pyrophosphate (MPP) were used to prepare flame‐retardant polyamide 6 (FR‐PA6). Flame retardance of FR‐PA6 samples was investigated by limiting oxygen index (LOI), UL‐94 vertical burning method, and cone calorimeter test. Morphology and component of char residues for FR‐PA6 were investigated by scanning electron microscope (SEM) and XPS. It was found that MA‐MMT/MPP system contributed both excellent flame retardance and anti‐dripping ability for PA6. MA‐MMT particles can fill flaws of char residues and strengthen the char layer, leading to form more intumescent char layer. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Using PA6 as a charring agent in intumescent polypropylene formulations based on carboxylated polypropylene compatibilizer and nano‐montmorillonite synergistic agent

The intumescent fire retardant polypropylene (IFP/PP) filled with ammonium polyphosphate (APP), melamine (M), and PA6 (charring agent) is discussed. Intumescing degree (ID) and the char yield were determined. Only when the three main components of IFR coexist at appropriate proportions, it has optimal ID and higher char yield. The appropriate proportion is PA6 : APP : M = 10 : 10 : 5. A new compatibilizer, carboxylated polypropylene (EPP), was added to PP/PA‐6 blend. Flow tests indicated that the apparent viscosity increased with the addition of EPP, thermal characterization suggested that EPP has reacted with PA6, PA6‐g‐EPP cocrystallized with PA6, and EPP‐g‐PA6 cocrystallized with PP; SEM micrographs illustrated that the presence of EPP improved the compatibility of PP and PA6. All the investigations showed that EPP was an excellent compatibilizer, and it was a true coupling agent for PP/PA6 blends. Using PA6 as a charring agent resulted in the IFR/PP dripping, which deteriorated the flammability properties. The addition of nano‐montmorillonite (nano‐MMT) as a synergistic agent of IFR enabled to overcome the shortcoming. The tensile test testified that the addition of nano‐MMT enhanced the mechanical strength by 44.3%. SEM showed that nano‐MMT improved the compatibility of the composites. It was concluded that the intumescent system with nano‐MMT was an effective flame retardant in improving combustion properties of polypropylene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 739–746, 2006     

Polymer‐Clay Nanocomposites Based on Blends of Polyamide‐6 and Polyethylene

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.     

Toughening and compatibilization of polypropylene/polyamide‐6 blends with a maleated–grafted ethylene‐co‐vinyl acetate

In this article, maleated–grafted ethylene‐co‐vinyl acetate (EVA‐g‐MA) was used as the interfacial modifier for polypropylene/polyamide‐6 (PP/PA6) blends, and effects of its concentration on the mechanical properties and the morphology of blends were investigated. It was found that the addition of EVA‐g‐MA improved the compatibility between PP and PA6 and resulted in a finer dispersion of dispersed PA6 phase. In comparison with uncompatibilized PP/PA6 blend, a significant reduction in the size of dispersed PA6 domain was observed. Toluene‐etched micrographs confirmed the formation of interfacial copolymers. Mechanical measurement revealed that the addition of EVA‐g‐MA markedly improved the impact toughness of PP/PA6 blend. Fractograph micrographs revealed that matrix shear yielding began to occur when EVA‐g‐MA concentration was increased upto 18 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3300–3307, 2006     

Flame retardancy and mechanical properties of polyamide 6 with melamine polyphosphate and ionic liquid surfactant‐treated montmorillonite

The mechanical properties and inflammability of polyamide 6 (PA6) nanocomposites incorporated with Montmorillonite organoclay (MMT) modified with thermal stable ionic liquid surfactants were investigated. The compatibility between ionic liquid‐treated MMT and PA6 matrix was improved and the intercalation morphology was achieved, which resulted in the increaseof tensile modulus. However, the addition of organo‐MMTs alone did not improve the inflammability of the PA6 nanocomposite, because of strong melt‐dripping behavior of PA6 matrix. Addition of auxiliary melamine polyphosphate (MPP) intumescent flame retardant to the nanocomposite prevented the melt dripping and enhanced inflammability performance. The enhanced inflammability of PA6/organoclay/MPP nanocomposites was attributed to the synergistic effect between imidazolium or phosphonium organo‐MMTs and intumescent flame retardant MPP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40648.     

Flame‐retardant finishing in cotton fabrics using zinc oxide co‐catalyst

In this article, N‐Methylol dimethylphosphonopropionamide (FR) in combination with a melamine resin (CL), phosphoric acid (PA) catalyst and zinc oxide (ZnO) or nano‐ZnO co‐catalyst were used (FR‐CL‐PA‐ZnO or nano‐ZnO system) to impart flame‐retardant property on cotton fabrics. FR‐CL or FR‐CL‐PA‐treated cotton specimen showed roughened and wrinkled fabric surface morphology, which was caused by the attack of the FR with slightly acidity. In addition, FTIR analysis showed some new characteristic peaks, carbonyl, CH₂ rocking and CH₃ asymmetric and CH₂ symmetric stretching bands, in the chemical structure of treated cotton specimens. Apart from these, the flame ignited on the flame‐retardant‐treated fabrics (without subjected to any post‐wet treatment) extinguished right after the removal of ignition source. However, FR‐CL treated specimens were no longer flame‐resistant when the specimens subjected to neutralization and/or home laundering, while FR‐CL‐PA treated specimens showed opposite results. By using 0.2% and 0.4% of ZnO or nano‐ZnO as co‐catalyst, the flame spread rate of neutralized and/or laundered test specimens decreased, even the specimens were undergone 10 home laundering cycles. Moreover, flame‐retardant‐treated cotton specimens had low breaking load and tearing strength resulting from side effects of the crosslinking agent used, while addition of ZnO or nano‐ZnO co‐catalyst could compensates for the reduction. Furthermore, the free formaldehyde content was dropped when ZnO and nano‐ZnO co‐catalyst was added in the treatment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystal structures and their effects on the properties of polyamide 12/clay and polyamide 6–polyamide 66/clay nanocomposites

Both polyamide 12 (PA 12)/clay and polyamide 6–polyamide 66 copolymer (PA 6/6,6)/clay nanocomposites were prepared by melt intercalation. The incorporation of 4–5 wt % modified clay largely increased the strength, modulus, heat distortion temperature (HDT), and permeation resistance to methanol of the polyamides but decreased the notched impact strength. Incorporation of the clay decreased the melt viscosities of both the PA 12 and PA 6/6,6 nanocomposites. Incorporation of the clay increased the crystallinity of PA 6/6,6 but had little effect on that of PA 12, which explained why the clay obviously increased the glass‐transition temperature of PA 6/6,6 but hardly had any effect on that of PA 12. The dispersion and orientation of both the clay and the polyamide crystals were studied with transmission electron microscopy, scanning electronic microscopy, and X‐ray diffraction. The clay was exfoliated into single layers in the nanocomposites, and the exfoliated clay layers had a preferred orientation parallel to the melt flow direction. Lamellar crystals but not spherulites were initiated on the exfoliated clay surfaces, which were much more compact and orderly than spherulites, and had the same orientation with that of the clay layers. The increase in the mechanical properties, HDT, and permeation resistance was attributed to the orientated exfoliated clay layers and the lamellar crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4782–4794, 2006     

Effects of functional group on the mechanical properties of PA6/SiO2 composites

The polyamide‐6 materials were mixed with nano‐silica modified by γ‐glycidoxypropyltrimethoxysilane (GPS) via a melt blending process. The idea was to study the correlation between content of GPS and PA6/silica interfacial interactions as well as mechanical properties of PA6/silica composites. The epoxy groups in GPS could react with –COOH and –NH₂ in PA6 to produce the covalent bond and hydrogen bonding based on FTIR chart, TG analysis, and TEM analysis results. The DSC results show that nanosilica could encourage the formation of the hydrogen bonded structure of the α‐PA6 crystals. However, the over GPS could confine the motion of polyamide‐6 and decrease the generation of α‐PA6 crystals resulted the decrease of mechanical properties. So the amount of epoxy groups grafted on nano‐silica has a threshold effect on strength of PA6. POLYM. COMPOS., 35:435–440, 2014. © 2013 Society of Plastics Engineers     

Phase morphology evolution and compatibilization of immiscible polyamide 6/polystyrene blends using nano‐montmorillonite

Nanocomposites of organic nano‐montmorillonite (nano‐OMMT)‐filled immiscible polyamide 6 (PA6)/polystyrene (PS) blends were prepared by three different processing methods. Masterbatch M1 of OMMT/PA6 and masterbatch M2 of OMMT/PS were prepared as separate masterbatchs by melt mixing with PA6 or PS, and then either mixed together or each mixed individually with appropriate amounts of PS or PA6, respectively. The effects of nano‐OMMT content and processing method on the structure, phase morphology, and mechanical properties of the PA6/PS/OMMT nanocomposites were investigated by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and mechanical properties tests. The results showed that the nano‐OMMT by M1 and M2 masterbatches dispersed primarily as exfoliated platelets in the PA6 matrix in the final composites regardless of the method of preparation. A drastic decrease of dispersed PS phase size and a very homogeneous size distribution were observed with the addition of nano‐OMMT. The PA6/PS/OMMT nanocomposites prepared from the M2 displayed the smallest dispersed PS phase size and best distribution of OMMT. The improvement of the mechanical properties of the PA6/PS/OMMT nanocomposites was attributed to the enhanced compatibilization of the immiscible PA6/PS blends by using nano‐OMMT. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Potential in situ preparation of aliphatic polyamide‐based nanocomposites: The organoclay‐polyamide salt interaction

In situ intercalative polycondensation is applied for the preparation of polyamide (PA) n,6–clay nanocomposites, namely poly(ethylene adipamide) (PA 2,6), poly(hexamethylene adipamide) (PA 6,6), and poly(dodecamethylene adipamide) (PA 12,6). For this purpose, two different polymerization routes are considered; a low‐temperature melt polymerization technique and the conventional solution‐melt one. Under the specific experimental conditions, lack of clay exfoliation is detected through XRD measurements, which is proved irreversible even when twin‐screw extrusion is attempted as an additional step. The resulting PA n,6–clay structures are found dependent on the diamine moiety length; more specifically, an intrinsic interaction between the polyamide monomer and the organoclay surfactant is indicated. An ion exchange occurs between the two competitive species, that is, diamine and surfactant cations, leading to flocculated clay structures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of morphology and ammonium polyphosphate dispersion on the flame retardancy of polystyrene/nylon‐6 blends

The influences of the distribution of ammonium polyphosphate (APP) in polystyrene/nylon‐6 [PS/polyamide‐6 (PA6)] blends and the continuity of the (PA6 + APP) phase on flame retardancy were investigated. The flame retardant properties were evaluated by limiting oxygen index (LOI), vertical flammability test and cone calorimeter tests. The results showed that APP is exclusively dispersed in the PA6 phase, and (PA6 + APP) phase formed a continuous state when the content of PA6 in PS/PA6 blends was higher than 32% (w/w). For blends with a continuous (PA6 + APP) phase, the decrease of PA6 content caused an increase in LOI values from 26% to 33% and a reduction of peak heat release rate. The improvement of flame retardancy was attributed to the increase of APP concentration in the PA6 phase, which benefited the fast formation of a continuous intumescent charred layer. The transformation of (PA6 + APP) phase morphology from a continuous state to a discontinuous state at a PA6 content of below 32% (w/w) caused a decrease in LOI. Results of thermo‐gravimetric and cone calorimeter tests indicated that the discontinuous intumescent charred layer thus formed could be responsible for the deterioration of flame retardant properties, which was also confirmed by scanning electron microscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

Mechanical properties and morphology of PA6/EVA blends

The mechanical properties of blends of polyamide6 (PA6) and ethylene vinyl acetate (EVA) at a blending composition of 0–50 wt % EVA were studied. The notched Izod impact strength of PA6 increased with the incorporation of EVA, the increase being more than 100% compared to PA6 at 10% EVA. The tensile strength and the tensile modulus of the blends decreased steadily as the weight percent of EVA increased. Analysis of the tensile data using predictive theories indicated the extent of the interaction of the dispersed phase and the matrix up to 20 wt % EVA. SEM studies of the cryogenically fractured surfaces indicated increase in the dispersed phase domain size with EVA concentrations. On the other hand, impact fractured surfaces of PA6/EVA blends indicated debonding of EVA particles, leaving hemispherical bumps, indicating inadequate interfacial adhesion between PA6 and EVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1593–1606, 2002     

Characterization of crystalline structure and free volume of polyamide 6/nitrile rubber elastomer thermoplastic vulcanizates: Effect of the processing additives

Blends of polyamide 6 and nitrile rubber (PA6/NBR) dynamically vulcanized may generate innovative products for special purposes where both high temperature and chemical resistance are key factors. In this investigation, we show that the crystalline nature of the PA6 can be controlled in terms of its morphological aspects (degree of crystallinity, crystal size, and structure) as a consequence of the presence of NBR and processing additives. Our results indicate that this crystalline control is dependent on the plasticization caused by the processing additives. Furthermore, imide‐like linkage formation was favored in the presence of ethylene‐co‐vinyl acetate (EVA)‐g‐maleic anhydride, resulting in changes in the molecular mobility of the PA6 matrix, crystallization parameters, and viscoelastic properties when compared to the others EVA additives. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45576.     

Investigation of thermal degradation and flammability of polyamide‐6 and polyamide‐6 nanocomposites

In this paper, polyamide‐6 and polyamide‐6 nanocomposites were prepared by direct melt intercalation technique. The thermal degradation behavior of both polyamide‐6 and polyamide‐6 clay nanocomposites has been studied. The apparent activation energy of the nanocomposites is almost the same with that of pure polymer under nitrogen, but the apparent activation energy of the nanocomposites is greatly enhanced in air atmosphere. This increasing trend coincides with the thermal analysis and the cone calorimeter results, which may suggest that the polymer/clay nanocomposites have a higher thermal stability and lower flammability. The kinetic analysis also indicates that the pyrolytic degradation and the thermal oxidative degradation of PA6 and PA6/OMT nanocomposites are two kinds of different reaction models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2297–2303, 2007     

Synergistic effects of silica nanoparticles and reactive compatibilizer on the compatibilization of polystyrene/polyamide 6 blends

This study examines the selective dispersion of nano‐SiO₂ in polystyrene (PS) and polyamide 6 (PA6) blends. With the coupling assistance of 3‐methacryloylpropyl trimethoxysilane (MPS), nano‐SiO₂ surfaces are grafted with PS chains of different molecular weights (SiO₂–MPS–PS) or reactive random copolymer of styrene (St) and 3‐isopropenyl‐α,α′‐dimethylbenzene isocyanate (TMI) to produce SiO₂–MPS–P(St–co–TMI). The isocyanate groups of the reactive copolymer can react with the terminal group of the PA6 to form a graft copolymer, which helps in controlling the location of nano‐SiO₂ between the PS and PA6 phases. Field‐emission scanning electron microscopy imaging combined with the rheological method was used to investigate the location and dispersion of nano‐SiO₂, as well as the morphology of the PS/PA6 blends, at low nano‐SiO₂ loading. Compared with pristine SiO₂, the modified SiO₂ with different chain lengths adjusted the PA6 phase with refined size and narrow size distribution because of the strong interaction with both phases. The SiO₂–MPS–PS with appropriate length is the most effective. The use of nano‐SiO₂ along with the reactive compatibilizer provides synergistic effects for improving the compatibilization of PS/PA6 blends. POLYM. ENG. SCI., 57:1301–1310, 2017. © 2017 Society of Plastics Engineers     

Effects of swelling agents on the crystallization behavior and mechanical properties of polyamide 6/clay nanocomposites

Montomorillonite was organically modified with three different swelling agents: n‐dodecylamine, 12‐aminolauric acid, and 1,12‐diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X‐ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1686–1693, 2003     

Self‐assembly morphology evolution of the polyamide 6 (PA6) component in the PA6/polyethylene glycol system by in situ polymerization of ϵ‐caprolactam monomer

This paper describes the morphology evolution of polyamide 6 (PA6) components in the presence of polyethylene glycol (PEG) by self‐assembly via in situ anionic ring‐opening polymerization of ?‐caprolactam (CL) monomer and expands the study of morphology changes of PA6 in the PA6/PEG system. With a fixed mass ratio of [CL]/[PEG], it was found that by simply changing the reaction conditions the morphology of PA6 components could be changed from nano‐sized microspheres to regular 3D microsphere structured polyhedrons to 3D nano‐sized particle clusters to micro‐scale microspheres. The morphologies of the PA6 components were investigated by SEM and TEM analyses. The diameter range of the PA6 nano‐sized microspheres was controlled within 400 nm. The side length of an individual polyhedron could be effectively tuned from 10 µm to 100 µm. The diameter range of micrometer microspheres was about 5–8 µm. The results suggest that this strategy for self‐assembly can be applied to design materials with complex geometric structures. © 2018 Society of Chemical Industry     

Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Free‐volume hole properties of two kinds thermoplastic nanocomposites based on polymer blends probed by positron annihilation lifetime spectroscopy

Two type of nanocomposites—an immiscible blend, high density polyethylene/polyamide 6 (HDPE/PA‐6) with organomodified clay, and a compatibilized blend, high density polyethylene grafted with acrylic acid/PA‐6 (PEAA/PA‐6) with organomodified clay—were prepared via melt compounding. X‐ray diffraction and transmission electron microscopy results revealed that the clay was intercalated and partially exfoliated. Positron annihilation lifetime spectroscopy has been utilized to investigate the free‐volume hole properties of two type of nanocomposites. The results show a negative deviation of free‐volume size in PEAA/PA‐6 blend, and a positive deviation in HDPE/PA‐6 blend, and I₃ has a greater negative deviation in compatibilized blend than in immiscible blend due to interaction between dissimilar chains. For nanocomposites based on polymer blends, in immiscible HDPE/PA‐6/organomodified clay system, the variation of free‐volume size with clay content is not obvious and the free‐volume concentration and fraction decreased. While in the case of compatibilized PEAA/PA‐6/organomodified clay nanocomposites, complicated variation of free‐volume properties due to interactions between two phases and organomodified clay was observed. And the interaction parameter β shows the interactions between polymers and organomodified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2463–2469, 2006