Studies on novel composites of polyoxymethylene/ polyamide 6

A series of new composite of polyoxymethylene/polyamide 6 (POM/PA 6) were synthesized by using ε‐caprolactam as a reactive solvent with POM soluble in it. Incorporating a small content of POM (1–4 wt %) into PA 6 led to a great improvement of impact resistance POM/PA 6. The effects of POM content on the mechanical, morphological, and thermal properties of the composites were investigated. Incorporating minor POM (1 wt %), disposed in finely dispersed level (about 1 μm), into PA 6 matrix can greatly reduce the crystallization rate and crystallinity of PA 6. Scanning electron microscopy measurements indicated that much microfibers with aspect ratio about 10 appeared with the addition of 3 wt % POM because of the change of phase separation mechanisms. As a result, with a small content of PA 66 (1–4 wt %) incorporated, the impact strength and elongation of POM/PA 6 were improved markedly, with retention of good tensile strength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 335–339, 2006     

Compatibilizing effect of styrene–maleic anhydride copolymer on the properties of polyamide‐6/liquid crystalline copolyester composites

Liquid crystalline polymer–polyamide‐6 (LCP/PA6) composites containing 20 wt % LCP content were compatibilized by a random styrene–maleic anhydride copolymer (RSMA). The blending was performed via extrusion followed by injection molding. The LCP employed was a commercial copolyester, Vectra A950. The dynamic mechanical (DMA), rheological, thermal, and mechanical properties as well as the morphology of the composites were studied. The DMA and rheological results showed that RSMA is an effective compatibilizer for LCP/PA6 blends. The mechanical measurements showed that the stiffness, tensile strength, and toughness of the in situ composites are generally improved with increasing RSMA content. However, these mechanical properties deteriorated considerably when RSMA content was above 10 wt %. The drop‐weight dart impact test was also applied to analyze the toughening behavior of these composites. The results show that the maximum impact force (F_max) and crack‐initiation energy (E_init) tend to increase with increasing RSMA content. From these results, it appeared that RSMA prolongs the crack‐initiation time and increases the energies for crack initiation and impact fracture, thereby leading to toughening of LCP/PA6 in situ composites. Finally, the correlation between the mechanical properties and morphology of the blends is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1964–1974, 2000     

Properties of cyanate ester-cured epoxy/polyphenylene oxide blends as a matrix material for Kevlar fiber composites

Epoxy/polyphenylene oxide (PPO) blends were cured with multifunctional cyanate ester resin. The effects of the PPO content on the cure behavior in the cyanate ester-cured epoxy were investigated with Fourier transform infrared spectroscopy (FTIR). The cure reaction in the epoxy/PPO blends was faster than that of the neat epoxy system. FTIR analysis revealed that the cyanate functional group reactions were accelerated by adding PPO and that several co-reactions had occurred, such as cyanate-hydroxyl addition and epoxy-cyanate addition. This was caused by the reaction of cyanate ester with the PPO phenolic end-group and water yielding imidocarbonate and carbamate intermediate which can react with cyanate ester to form cyanurate. Then the cyanurate can react further with the epoxy resin. Thermal mechanical analysis showed that the thermal stability of the epoxy/PPO blends is improved by adding PPO. The morphology of the fiber-rich areas in the composite is different from that of the epoxy/PPO blend without Kevlar fiber. In the pure polymer blends with high PPO content (30 and 50 phr), phase separation and phase inversion were observed. In the composites, the majority of the epoxy resin migrates to the polar fiber surface, resulting in epoxy-coated fibers. So the interfacial shear strength (IFSS) between Kevlar fiber and the epoxy/PPO blends is almost the same as that between Kevlar fiber and neat epoxy. The presence of PPO does not affect the interfacial property in the epoxy/PPO/fiber composite. So the interlaminar shear strength (ILSS) increase with the PPO content is due to an increase in the composite's ductility or toughness.     

Preparation of conductive polyphenylene sulfide/polyamide 6/multiwalled carbon nanotube composites using the slow migration rate of multiwalled carbon nanotubes from polyphenylene sulfide to polyamide 6

Conductive polyphenylene sulfide (PPS)/polyamide 6 (PA6)/multiwalled carbon nanotube (MWCNT) composites having 10–30 wt % PA6 and 1 wt % MWCNTs are prepared by melt mixing at 300°C for 8 min using a high concentration PPS/MWCNT masterbatch approach, and the migration kinetics of MWCNTs from thermodynamically unfavored PPS to favored PA6 was investigated. The morphology of the composites was investigated by field emission scanning electron microscopy and transmission electron microscopy, showing the localization of most MWCNTs in the PPS phase and at the interface, being different from the case of direct melt mixing where non‐conductive materials were obtained with most MWCNTs found in the PA6 phase and at the interface. The electrical resistivity and morphology of the materials as a function of time were investigated, showing that the conductive materials can be prepared within a mixing time of 4–16 min because of the slow migration rate of MWCNTs from PPS toward PA6, and MWCNTs can eventually migrate into the PA6 phase after a long mixing time of 30 min. The slow migration rate of MWCNTs was attributed to the high viscosity ratio of the two phases. This article shows a good example where the migration of MWCNTs was slow enough to control and can be used to prepare conductive polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42353.     

PPO-g-MAH与CNTs-x对PPO/PA6共混物的协同增强作用研究

研究了聚苯醚/尼龙6/聚苯醚接枝马来酸酐/功能化碳纳米管(PPO/PA6/PPO-g-MAH/CNTs-x)复合材料的形貌结构、力学性能、动态力学行为、流变性能。引入增容剂PPO-g-MAH可改善PPO与PA6之间的界面性能,明显提高了PPO/PA6共混物的力学性能。通过拉伸、冲击实验,动态力学和流变学实验分析发现,在PPO/PA6/PPO-g-MAH共混物中添加氨基化碳纳米管(CNTs-NH₂),其形貌和力学性能均优于碳纳米管(CNTs)和羧基化碳纳米管(CNTs-COOH)。这是由于CNTs-NH₂与PA6/PPO-g-MAH的相互作用较强,并随着CNTs-NH₂添加量的增加,复合材料的拉伸性能、储能模量和复数黏度提高,但冲击强度降低。     

Influence of nanoclay and coupling agent on the physical and mechanical properties of polypropylene/bagasse nanocomposite

In this work, the effects of nanoclay (1–4 wt %) and coupling agent (2 and 4 wt %) loading on the physical and mechanical properties of nanocomposites are investigated. Composites based on polypropylene (PP), bagasse flour, and nanoclay (montmorillonite type) was made by melt compounding and then compression molding. When 1–3 wt % nanoclay was added, the tensile properties increased significantly, but then decreased slightly as the nanoclay content increased to 4%. The impact strength was 6% lower by the addition of 1 wt % nanoclay, it was decreased further when the nanoclay content increased from 1 to 4%. Finally, the water absorption of PP/bagasse composites was lowered with the increase in nanoclay content. Additionally, the coupling agent, 4 wt % MAPP, improved the mechanical and physical properties of the composites more than the 2 wt % MAPP. From these results, we can conclude that addition of nanoclay enables to achieve better physical and mechanical properties in conventional composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Relationship between structure and properties in high‐performance PA6/SEBS‐g‐MA/(PPO/PS) blends: The role of PPO and PS

This work aimed at studying the role of poly(phenylene oxide) (PPO) and polystyrene (PS) in toughening polyamide‐6 (PA6)/styrene‐ethylene‐butadiene‐styrene block copolymer grafted with maleic anhydride (SEBS‐g‐MA) blends. The effects of weight ratio and content of PPO/PS on the morphology and mechanical behaviors of PA6/SEBS‐g‐MA/(PPO/PS) blends were studied by scanning electron microscope and mechanical tests. Driving by the interfacial tension and the spreading coefficient, the “core–shell” particles formed by PPO/PS (core) and SEBS‐g‐MA (shell) played the key role in toughening the PA6 blends. As PS improved the distribution of the “core–shell” particles due to its low viscosity, and PPO guaranteed the entanglement density of the PPO/PS phase, the 3/1 weight ratio of PPO/PS supplied the blends optimal mechanical properties. Within certain range, the increased content of PPO/PS could supply more efficient toughening particles and bring better mechanical properties. Thus, by adjusting the weight ratio and content of PPO and PS, the PA6/SEBS‐g‐MA/(PPO/PS) blends with excellent impact strength, high tensile strength, and good heat deflection temperature were obtained. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45281.     

硅烷偶联剂对ZnO/PA6复合材料力学性能的影响

以硅烷偶联剂KH550和KH560为改性剂对ZnO粉体进行表面改性,KH550带有氨基团,KH560带有环氧基团,通过HAAKE双螺杆混合机制备ZnO/PA6复合材料。红外光谱证实改性后两种偶联剂均与ZnO表面发生了化学键和;结果表明经偶联剂改性的氧化锌比未改性的氧化锌能更好的提高PA6的拉伸强度,而且在ZnO的添加量为2%～3%时对PA6力学性能的改善达到一个最佳效果。     

Study on in situ reinforcing and toughening of a semiflexible thermotropic copolyesteramide in PBT/PA66 blends

Ternary in situ composites based on poly(butylene terephthalate) (PBT), polyamide 66 (PA66), and semixflexible liquid crystalline polymer (LCP) were systematically investigated. The LCP used was an ABA30/PET liquid crystalline copolyesteramide based on 30 mol % of p‐aminobenzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The specimens for thermal and rheological measurements were prepared by batch mixing, while samples for mechanical tests were prepared by injection molding. The results showed that the melting temperatures of the PBT and PA66 phases tend to decrease with increasing LCP addition. They also shifted toward each other due to the compatibilization of the LCP. The torque measurements showed that the ternary blends exhibited an apparent maximum near 2.5–5 wt % LCP. Thereafter, the viscosity of the blends decreased dramatically at higher LCP concentrations. Furthermore, the torque curves versus the PA66 composition showed that the binary PBT/PA66 blends can be classified as negative deviation blends (NDBs). The PBT/PA66/LCP blends containing up to 15 wt % LCP were termed as positive deviation blends (PDBs), while the blends with the LCP ≥25 wt % exhibited an NDB behavior. Finally, the tensile tests showed that the stiffness and tensile strength of ternary in situ composites were generally improved with increasing LCP content. The impact strength of ternary composites initially increased by the LCP addition, then deteriorated when the LCP content was higher than 10 wt %. The correlation between the mechanical properties and morphology of the blends is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1975–1988, 2000     

PPO／PA6／EPDM／滑石粉共混体系的加工－性能－形态之间关系研究

采用熔融共混法制备了聚苯醚(PPO)/聚酰胺6(PA6)/三元乙丙橡胶(EPDM)三元和PPO/PA6/EPDM/滑石粉四元体系的共混合金,而且在制备四元共混合金时采取先用马来酸酐接枝的三元乙丙橡胶(EPDM-g-MAH)与滑石粉制成母粒,然后再将母粒与PPO、PA6共混的方法,研究了三元和四元共混体系的力学性能、流变性能和相态结构。结果表明:将制备的母粒与PPO和PA6进行共混,当母粒含量在一定范围内时可以实现弹性体和无机刚性粒子对体系的协同增韧作用,且母粒含量在15％时达到最佳,其增韧效果优于相同用量的纯EPDM-g-MAH弹性体增韧体系,同时母粒的加入可以改善共混体系的流动性,对拉伸强度的影响也比较小。     

Selective laser sintering of polyamide 12/potassium titanium whisker composites

The excellent performance of potassium titanium whiskers (PTWs) reinforced plastics has been recognized; however, because of their large length‐to‐diameter ratio, they have not been applied in selective laser sintering (SLS). This article reports a new method for preparing polyamide 12 (PA12)/PTWs composite (PPC) powders for applications in SLS that uses a dissolution–precipitation process. The characteristics of the powders were evaluated. The results indicated that when the PTWs content of the composites was low (<10 wt %), the shape of the powder became more regular, and the particle diameter distribution became narrower. The crystallinity of PPC was 13 wt % higher than that of PA12. The sintering characteristics and mechanical properties of PA12 powder, glass‐filled PA12 (GF–PA), and PPCs were compared. The results showed that the sintering characteristics of PPCs (10 or 20 wt % PTWs) were as good as those of PA12. The mechanical properties were greatly improved by PTWs. The maximum tensile strength, bending strength, and bending modulus of the composites containing 20 wt % PTW were 68.3 MPa, 110.9 MPa, and 2.83 GPa, respectively, and were much higher than those of PA12 and GF–PA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influences of high-impact polystyrene loading on the foaming behavior and flame-retardant properties of polyphenylene oxide composites blown with CO2

Polymeric foam with high expansion ratio, well-defined cell structure, and excellent flame retardant properties is essential for broadening its applications. Polyphenylene oxide (PPO) is a kind of cost-effective engineering plastic with excellent flame retardancy, anti-dripping behavior, and good mechanical strength, but suffers from its poor processability. In this study, microcellular PPO composite foams were fabricated by applying a solid-state foaming technology using compressed CO₂ as the blowing agent. High-impact polystyrene (HIPS) phase was introduced with the aim to improve the fluidity and foaming ability of PPO composites. It was interesting to find that the 18–48% HIPS loading significantly increased the expansion ratio, that is, 1.8–3.3 versus, 10.8–14.3, and broadened the optimum foaming temperature of PPO composite foams, attributing to the miscible character between PPO and HIPS and excellent foaming ability of HIPS. Furthermore, the as-prepared PPO/HIPS composite foams exhibited high limited oxygen index (LOI) of 22.0–29.9%, low horizontal flammability rate (HFR) of 60.5–141.2 mm/min, and anti-dripping behavior, and the void fraction was verified to be a critical parameter to determine the flame retardant performance of the composite foam. Besides its lightweight and excellent flame retardant properties, PPO composite foams also presented uncompromised tensile properties and well-defined thermal insulation properties.     

Preparation and Mechanical Properties of Polyamide-6 Composites Reinforced with Fir Flour/SiO2 Hybrid Material

Fir flour/SiO₂ hybrid material (FSHM) was fabricated by Sol-gel infiltration process. The morphology and structure were investigated by Fourier transformed infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The composites of polyamide-6 (PA6) reinforced with FSHM were prepared by melt-mixing in twin-screw extruder. Part of FSHM was treated with γ-aminopropyltriethyoxysilane or epoxy resin as compatibilizer. Tensile strength of the composites with 25 wt.% of FSHM increased by almost 23.3% compared to that of pure PA6, whereas 59.8% increase in flexural strength was observed. Both compatibilizers improved interfacial adhesion between FSHM and PA6, resulting in increased impact strength of the composites.     

Tensile properties and damage behaviors of glass‐bead‐filled modified polyphenylene oxide under large strain

Based on Continuum Damage Mechanics (CDM), a damage model for glass‐bead‐filled modified polyphenylene oxide (GB/PPO) has been proposed to describe its damage behavior at various levels of tensile strain by considering the reduction of effective loading area. Hence, an equation for prediction of effective elastic modulus of the damaged GB/PPO composites in terms of the three principal true strains was derived. The tensile properties and damage behaviors of the GB/PPO composites with different volume percentages of glass beads were investigated using standard tensile tests and load‐unload tests, respectively. The addition of glass beads increases Young's modulus of PPO but has a weakening effect on its tensile strength. A maximum value of tensile work to break and tensile strain at break was found when 5 vol% of glass beads with a mean diameter of 11 μm was blended with PPO. These results were justified through microscopic examination of the fracture surfaces of the tensile specimens by using a scanning electron microscope (SEM). In‐situ observations of the strain damage processes were made through the SEM equipped with a tensile stage to determine the strain at fully debonding of glass beads. The volumetric strain of GB/PPO composites increases because of microcavitation during strain damage. In general, the prediction for the effective elastic modulus of the damaged GB/PPO composites at different true strains is slightly higher than the experimental results. The damage evolution rates after fully debonding of glass beads from the matrix are close to those predicted by the proposed damage model.     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Compatibilization and toughening of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 alloy with poly(ethylene 1‐octene): Mechanical properties,morphology, and rheology

Blends of a poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO)/polyamide 6 (PA 6) alloy toughened with a novel polyolefin elastomer poly(ethylene‐1‐octene) (POE) were prepared via melt extrusion. In order to improve the compatibilization between POE and the PPO/PA 6 alloy, POE was grafted with maleic anhydride (MA), which could react with the amine group of PA 6. The Izod impact strength of the blends exhibited an optimum when the extent of MA grafting of POE was changed, which is an order of magnitude higher than that of the untoughened blends. The morphology revealed that the size of the POE particles decreased with an increasing MA grafting ratio of POE. Studies on the tensile properties and rheology of the blends were also carried out. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3110–3116, 2003     

Ultrahigh compressive strength and heat resistance of polystyrene/polyphenylene oxide foams of supercritical carbon dioxide foaming

Polystyrene (PS) foam materials are lightweight, but suffer from poor compressive strength and heat resistance, among other problems, which limit their application. Herein, a method for preparing PS foam with high compressive strength and high heat resistance using supercritical CO₂ is proposed. PS/polyphenylene oxide (PPO) blends were prepared using a corotating intermeshing twin-screw extruder. The results showed that PPO exhibited excellent molecular-level compatibility with PS, which substantially improved mechanical properties and heat resistance of PS. Foam samples of PS/PPO blends with the same expansion ratio were prepared via batch foaming experiments, and the compressive strength of different foams was determined at different temperatures. At room temperature, the compressive strength of the PS/PPO-30% foam increased by 173% compared with pure PS foam. As the testing temperature increased from 30 to 120°C, the compressive strength of pure PS foams decreased rapidly. Nevertheless, PS/PPO foams maintained high compressive strength at high temperatures.     

Kinetic studies of the reactive compatibilization of polyamide 6, polycarbonate and poly(propylene oxide)

The kinetics of the reactive blending process occurring during the stirred melting of polyamide 6/polycarbonate (PA6/PC), polyamide 6/polycarbonate/poly(propylene oxide) (PA6/PC/PPO) in a Haake internal mixer at 240°C were investigated. In the PA6/PC blends the formation of copolymers can be observed and they act as compatibilizing agents, raising the miscibility of these blends. In the PA6/PC/PPO blends, the composition is very important in creating the PA6-PC copolymers. The rise of the PPO percentage increases the mobility of the PA6 molecules and the probability of formation of PA6-PC copolymers in PA6/PC/PPO blends with 10% w/w of PC. The PPO percentage (3-10 phr) influences the kinetics of reaction of PA6/PC/PPO ternary blends with a constant PA6/PC mass ratio (85/15).     

In situ Polymerization of Polyamide 6/Boron Nitride Composites to Enhance Thermal Conductivity and Mechanical Properties via Boron Nitride Covalently Grafted Polyamide 6

Polyamide 6/boron nitride (PA6/BN) composites were synthesized via anionic ring-opening polymerization using ε-caprolactam as the monomer and functional boron nitride (f-BN) as the thermal conductive filler. Besides the homopolymerized PA6, some PA6 molecule chains would grow from the f-BN sheets through the “grafting from” strategy. Compared with unfunctional hexagonal BN (h-BN), the introduction of f-BN not only improved the dispersion of f-BN in the matrix but also enhanced the interface bonding between f-BN and PA6. The homogeneous dispersion of f-BN in the PA6/f-BN composite favored the formation of the continuous thermal conductive paths or network at a low f-BN loading, and the good interface bonding reduced the phonon scattering in the interface, which improved the thermal conductivity (TC) of the PA6/f-BN composite by 66.0% compared with that of the pure PA6, when only 5 wt% f-BN was added. In contrast, with the same content of unfunctional h-BN loading, the TC of the corresponding composite merely improved by 29.7%. Moreover, Young's modulus and yield strength of PA6/f-BN composites had increased obviously with the introduction of f-BN, whereas those of PA6/h-BN composites showed small fluctuation with the same contents of BN. POLYM. ENG. SCI., 60:710–716, 2020. © 2020 Society of Plastics Engineers     

Modification of melt,light, and heat stability of polyamide 6 by hindered piperidine amine and tertiary amine

Hindered piperidine amine (HPA) and tertiary amine (TA) were introduced into hydrolytic polymerization of caprolactam, and polyamide 6 (PA 6) modified by additives [HPA/TA = 1 : 1 (w/w)] was obtained. The effects of additives on the melt, light, and heat stability of PA 6 were studied. The results showed that with an increase in additive content, the viscosity of PA 6 increased and the elastic response decreased. Thus, the drawing property of PA 6 fibers during melt spinning was improved. With the addition of 0.1%–0.2% additives, the degree of variation in amino end group content and relative viscosity decreased during the process going from resin to fiber, indicating the modified PA 6 had improved melt stability. During light and heat aging, the ratio of retained fracture strength of PA 6 filament increased after modification by 0.1%–0.4% additives. Scanning electron microscopy showed that the surface morphology of the modified fiber remained almost the same, whereas that of the unmodified fiber was seriously destroyed when exposed to xenon light for 8 days or heated to 180°C in air for 1.5 h. The degree of variation of relative viscosity of the PA 6 fiber also decreased after modification by 0.1%–0.2% additives under oxidative degradation. All these results indicate PA 6 had better melt, light, and heat stability when modified by additives. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 538–544, 2007