Synthesis and characterization of nylon 6/clay nanocomposites prepared by ultrasonication and in situ polymerization

Nylon 6 nanocomposites were prepared by the in situ polymerization of ε‐caprolactam with ultrasonically dispersed organically modified montmorillonite clay (Cloisite 30B®). Dispersions of the clay platelets with concentrations in the range 1–5 wt % in the monomer were characterized using rheological measurements. All mixtures exhibited shear‐thinning, signifying that the clay particles were dispersed as platelets and forming a “house of cards” structure. Samples with Cloisite concentrations above 2 wt % showed a drop in viscosity between the initial shearing and repeated shearing, indicative of shearing breaking down the initial “house of cards” structures formed on sonication. DMTA measurements of the samples showed an increase in the β‐relaxation temperature with increasing clay concentration. The bending modulus, at temperatures below T_g, showed an increase with increasing clay concentration up to 4 wt %. X‐ray diffraction measurements showed that all nylon 6/Cloisite 30B samples were exfoliated apart from the 5 wt %, which showed that some intercalated material was present. The nylon crystallized into the α‐crystalline phase, which is the most thermodynamically stable form. Preference for this form may be a consequence of the long time associated with the postcondensation step in the synthesis or the influence of the platelets on the nucleation step of the crystal growth. DSC measurements showed a retardation of the crystallization rate of nanocomposite samples when compared with that of pure nylon 6, due to the exfoliated clay platelets hindering chain movement. This behavior is different from that observed for the melt‐mixed nylon 6/clay nanocomposites, which show an enhancement in the crystallization rate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The influence of silane treatment on nylon 6/nano‐SiO2 in situ polymerization

Silane treatment has been applied to the preparation of nylon 6/nano‐SiO₂ composites through in situ polymerization. The influence of such treatment on the reactivity of silica, polymerization of nylon 6, and the mechanical properties of the achieved composites has been studied. Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA) of silicas isolated from the composites have shown that the conversion of surface silanol groups to amino and epoxy groups did not cause a significant change in the reactivity of silica and that the percentage of silica surface grafting was around 15% for all treated and untreated silicas. End group analysis has shown that the presence of silica (pretreated or not) in the composite system resulted in the decrease of the average molecular weight of the polymer matrix. However, dynamic mechanical analysis and mechanical tests revealed that treating silica with silane improved the strength and toughness of the composite materials, while untreated silica improved their strength at the expense of toughness. This can be attributed to the existence of the flexible interlayer introduced by silane treatment. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 827–834, 2002; DOI 10.1002/app.10349     

Studies on nylon 6/clay nanocomposites by melt‐intercalation process

The preparation of nylon 6/clay nanocomposites by a melt‐intercalation process is proposed. X‐ray diffraction and DSC results show that the crystal structure and crystallization behaviors of the nanocomposites are different from those of nylon 6. Mechanical and thermal testing shows that the properties of the nanocomposites are superior to nylon 6 in terms of the heat‐distortion temperature, strength, and modulus without sacrificing their impact strength. This is due to the nanoscale effects and the strong interaction between the nylon 6 matrix and the clay interface, as revealed by X‐ray diffraction, transmission electron microscopy, and Molau testing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1133–1138, 1999     

Synthesis of polypropylene‐graft‐maleic anhydride compatibilizer and evaluation of nylon 6/polypropylene blend properties

Polymer blends based on polyolefins are of a great interest owing to their broad spectrum of properties and practical applications. However, because of poor compatibilities of components, most of these systems generally exhibit high interfacial tension, a low degree of dispersion and poor mechanical properties. It is generally accepted that polypropylene (PP) and nylon 6 (N6) are not compatible and that their blending results in poor materials. The compatibility can be improved by the addition of a compatibilizer, and in this study PP was functionalized by maleic anhydride (MAH) in the presence of an optimized amount of dicumyl peroxide (DCP). The reaction was carried out in the molten state using an internal mixer. Then, once the compatibilizer polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) was prepared, it was added at various concentrations (2.5–10 wt%) to 30/70 glass fibre reinforced N6 (GFRN6) PP, and the mechanical properties were evaluated. It was found that the incorporation of the compatibilizer enhanced the tensile properties (tensile strength and modulus) as well as the Izod impact properties of the notched samples. This was attributed to better interfacial adhesion as evidenced by scanning electron microscopy (SEM). The optimum in these properties was achieved at a critical PP‐g‐MAH concentration. Copyright © 2005 Society of Chemical Industry     

Preparation and properties of nylon 6/carboxylic silica nanocomposites via in situ polymerization

Nylon 6/carboxylic acid‐functionalized silica nanoparticles (SiO₂‐COOH) nanocomposites were prepared by in situ polymerization of caprolactam in the presence of SiO₂‐COOH. The aim of this work was to study the effect of carboxylic silica on the properties of the nylon 6 through the interfacial interactions between the SiO₂‐COOH nanoparticles and the nylon 6 matrix. For comparison, pure nylon 6, nylon 6/SiO₂ (unmodified) and nylon 6/amino‐functionalized SiO₂ (SiO₂‐NH₂) were also prepared via the same method. Fourier transform infrared spectrometer (FTIR) spectroscopy was used to evaluate the structure of SiO₂‐COOH and nylon 6/SiO₂‐COOH. The results from thermal gravimetric analysis (TGA) indicated that decomposition temperatures of nylon 6/SiO₂‐COOH nanocomposites at the 5 wt % of the total weight loss were higher than the pure nylon 6. Differential scanning calorimeter (DSC) studies showed that the melting point (T_m) and degree of crystallinity (X_c) of nylon 6/SiO₂‐COOH were lower than the pure nylon 6. Mechanical properties results of the nanocomposites showed that nylon 6 with incorporation of SiO₂‐COOH had better mechanical properties than that of pure nylon 6, nylon 6/SiO₂, and nylon 6/SiO₂‐NH₂. The morphology of SiO₂, SiO₂‐NH₂, and SiO₂‐COOH nanoparticles in nylon 6 matrix was observed using SEM measurements. The results revealed that the dispersion of SiO₂‐COOH nanoparticles in nylon 6 matrix was better than SiO₂ and SiO₂‐NH₂ nanoparticles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

In situ polymerization and nano‐templating phenomenon in nylon fiber/PMMA composite laminates

Supercritical Carbon Dioxide (SC CO₂) is used as a reaction/processing medium in the fabrication of fiber‐reinforced composite materials. SC CO₂ allows resin (reactive monomer), to penetrate inside the fibers themselves, partitioning into the amorphous regions of the fiber. The crystal structure then templates polymerization of matrix within the fiber. This process produces a composite that exhibits ultralong‐range order from the nanoscale reinforcement of crystals to the macroscale fiber reinforcement of matrix. In addition, SC CO₂ lowers resin viscosity and aids in wetting out Nylon 6,6 fiber reinforcement in a process similar to reaction injection molding (RIM) or resin transfer molding (RTM). This article will discuss the fabrication technique in detail, including process parameters and the structure of resulting composites and morphology of modified fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1600–1607, 2003     

尼龙6固相聚合模型及计算机模拟研究

根据尼龙6固相聚合反应机理,建立了由可逆化学反应和小分子扩散共间控制的尼龙6固相聚合动力学模型,并确定了其动力学和热力学参数。通过计算机模拟实验表明,聚合反应温度越高,预聚体尺寸越小,预聚体初始相对分子质量越高,越有利于固相增粘反应,有利于固相聚合尼龙6相对分子质量的增加。     

Toughened nylon66/nylon6 ternary nanocomposites by elastomers

The elastomer toughening of PA66/PA6 nanocomposites prepared from the organic modified montmorillonite (OMMT) was examined as a means of balancing stiffness/strength versus toughness/ductility. Several different formulations varying in OMMT content were made by mixing of PA6 and OMMT as a master‐batch and then blending it with PA66 and different elastomers in a twin screw extruder. In this sequence, the OMMT layers were well exfoliated in the nylon alloy matrix. The introduction of silicate layers with PA6 induced the appearance of the γ crystal phase in the nanocomposites, which is unstable and seldom appears in PA66 at room temperature and it further affected the morphology and dispersion of rubber phase resulting in much smaller rubber particles. The incorporation of POE‐g‐MA particles toughened the nanocomposites markedly, but the tensile modulus and strength were both reduced. Conversely, the use of OMMT increased the modulus but decreased the fracture toughness. The nanocomposites exhibited balanced stiffness and toughness. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and properties of polyimide‐g‐nylon 6 and nylon 6‐b‐polyimide‐b‐nylon 6 copolymers

Polyimide‐g‐nylon 6 copolymers were prepared by the polymerization of phenyl 3,5‐diaminobenzoate with several diamines and dianhydrides with a one‐step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten ε‐caprolactam. Nylon 6‐b‐polyimide‐b‐nylon 6 copolymers were prepared by the use of phenyl 4‐aminobenzoate as an end‐capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of ε‐caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120°C to generate N‐acyllactam moieties, which activated the anionic polymerization. All the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide into both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 300–308, 2006     

Toughening and phase separation behavior of nylon 6–PEG block copolymers and in situ nylon 6–PEG blend via in situ anionic polymerization

We have prepared in situ molded products of morphologically different nylon 6/polyethylene glycol (PEG) copolymers and their blends via anionic polymerization of ε-caprolactam in the presence of several kinds of PEG derivatives using sodium caprolactamate as a catalyst and carbamoyl caprolactam derivative as an initiator. Three carbamoyl caprolactams, such as tolylene dicarbamoyl dicaprolactam (TDC), hexamethylene dicarbamoyl dicaprolactam (HDC), and cyclohexyl carbamoyl caprolactam (CCC), with different functionalities and activities were used. Phase separation behavior was investigated by dynamic mechanical thermal analysis (DMTA) and DSC during in situ polymerization and melt crystallization. The mechanical properties of these molded products were evaluated. PEG segments in the block copolymers showed amorphous characteristics, whereas a large fraction of unreacted PEG segments was crystallized in as-polymerized samples, except for the products obtained using the CCC activator. The presence of PEG derivatives retarded the crystallization of nylon 6 part during in situ polymerization as well as melt crystallization. However, PEG segments did not alter the crystalline structure of nylon 6, showing α-crystalline modification. The nylon 6–PEG–nylon 6 triblock copolymers showed the highest impact strength, whereas the nylon 6–PEG diblock copolymers and in situ nylon 6–PEG blends showed no improved toughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1285–1303, 1999     

Preparation and characterization of polyimide‐g‐nylon 6 copolymers from nonfunctionalized polyimides

In this research, the anionic polymerization of ?‐caprolactam was carried out in the presence of small amounts of several different polyimides to generate polyimide‐g‐nylon 6 copolymers. The polyimides, which were prepared from 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and commercially available diamines with a one‐step method, were first dissolved in molten ?‐caprolactam. Phenylmagnesium bromide was then added at 120°C. Under these conditions, caprolactam anions were formed that attacked the five‐membered imide rings to form N‐acyllactam moieties, which activated the anionic polymerization of caprolactam. In essence, nylon 6 chains grew from the polyimide backbones. Probably because of a high activation energy, the process was relatively slow, requiring 1 h at 120°C. The introduction of 5 wt % polyimide into the graft copolymers produced significant increases in the tensile modulus and tensile strength in comparison with those of low‐ and high‐molecular‐weight nylon 6. The elongation to break, however, was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 292–299, 2006     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

Synthesis and characterization of nylon 6/polyalkylaniline conducting composites

Conducting composite films of polyalkylanilines with nylon 6 as the insulating matrix were electrochemically synthesized and characterized. The electrochemical properties of the alkylanilines and their composites were investigated with a cyclic voltammetry technique. The magnetic properties of the polymers and composites were analyzed, and their conducting mechanisms were found to be of bipolaron nature. With Fourier transform infrared spectra, it was clarified that polymerization occurred via the ? NH₂ group in a head‐to‐tail mechanism. Through thermogravimetric analyses, the thermal properties of the polymers and their composites were elucidated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1693–1701, 2003     

尼龙6固相缩聚——实验数据与模型数据的比较

研究了不同起始相对分子质量、不同含水量的圆球状尼龙6切片在不同温度和反应时间下的连续固相缩聚行为.结果说明了起始相对分子质量和温度对尼龙6的固相增黏效果影响很大,和模型得出的结论一致;而不同含水量和反应时间同样也会影响尼龙6切片的固相增黏效果.此外,结果还发现在实际生产中,切片的起始氧化温度远远低于模型推断出的起始氧化温度.实验结果为今后的模型设计和改进提供了极有参考意义的数据,同时也为固相缩聚提出了新的研究方向.     

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of ? NH₂ and ? COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between ? NH₂ and ? COOH groups were used. The one with higher concentration of ? COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work. © 2001 Society of Chemical Industry     

Polyaniline–nylon 6 composite nanowires prepared by emulsion polymerization and electrospinning process

Polyaniline (PANI) nanoparticles doped with the dodecylbenzene sulfonic acid (DBSA) were prepared and these nanoparticles were electrospun with nylon 6 as matrix material into fiber web. Depending on the contents and concentrations of PANI and nylon 6, either nylon 6 nanofibers (～96 nm) or PANI‐nylon 6 composite nanofibers (～12 nm) were obtained. The electrical conductivity of PANI(DBSA)–nylon 6 electrospun fiber web was lower than that of PANI(DBSA)‐nylon 6 film because of the low crystallinity of the PANI(DBSA)–nylon 6 composite electrospun fiber web. However, it showed that the PANI–nylon 6 composite nanofibers would have applications as the nanowires for connecting the microelectromechanical system (MEMS). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1277–1286, 2006     

Synthesis and characterization of nylon‐6/mesoporous silica nanocomposites via in situ synchronous hydrolytic polymerization of tetraethylorthosilicate and ε‐caprolactam

Nylon 6 (N6)/mesoporous silica (MS) nanocomposites (NMSNs) were synthesized via in situ synchronous hydrolytic polymerization of tetraethylorthosilicate (TEOS) and ε‐caprolactam. The novelty of this technique lies in that the nanosilica generated in situ has unique mesoporous structure and ultrahigh‐specific surface area (SSA). Mechanical test showed that, compared to conventional precipitated silica (PS) nanofillers, the MS generated in situ shows better reinforcing efficiency on N6. At a loading of only 3.0 wt % MS, the tensile modulus, flexural modulus, and the heat distortion temperature of NMSNs exhibit increase of 54.8%, 77.9%, and 55.9°C, respectively. The effects of MS on the crystallization behaviors of N6 have been studied by differential scanning calorimetry (DSC), which shows that the incorporation of MS influences the crystallization behaviors of N6 obviously: (1) increases crystallization temperature (T_c) by serving as heterogonous nucleating agent; (2) favors the formation of γ‐phase by hindering the mobility of N6 chains. Dynamic mechanical analysis confirmed that, compared ti that of neat N6, the temperature of the main α‐relaxation (T_α) and the secondary β‐relaxation (T_β) of NMSNs is shifted 6.1°C and 5.3°C toward higher temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

尼龙 6聚合中几种浓缩液直接回用工艺的对比

对比了国外公司的不同尼龙 6浓缩液直接在己内酰胺聚合中回用的工艺特点 ,国内引进装置采用该工艺的情况及应注意的问题。提出保持聚合进料组成稳定和防止浓缩液析出是成功地采用浓缩液直接在尼龙 6聚合中回用工艺的关键     

Preparation of conducting nylon‐6 electrospun fiber webs by the in situ polymerization of polyaniline

For the preparation of conducting polyaniline (PANI)/nylon composites with high electrical conductivity as well as superior mechanical properties such as flexibility and lightness, PANI/nylon‐6 composite nanofiber webs were prepared via the electrospinning process with a nylon‐6/formic acid polymer solution, and then PANI on the surface of the nylon‐6 electrospun nanofiber webs was chemically polymerized. The electrical conductivity measurements showed that the conductivity of the PANI/nylon‐6 composite electrospun fiber webs was superior to that of PANI/nylon‐6 plain‐weave fabrics because of the high surface‐area/volume ratios. On the other hand, the volume conductivities of the PANI/nylon‐6 composite electrospun fiber webs increased from 0.5 to 1.5 S/cm as the diffusion time increased from 10 min to 4 h because of the even distribution of PANI in the electrospun fiber webs. However, the surface conductivities of the PANI/nylon‐6 composite electrospun fiber webs somewhat decreased from 0.22 to 0.14 S/cm as the diffusion time increased because of PANI contaminated with aniline monomers, aniline oligomers, and some alkyl chains, which served as electrical resistants. These results were confirmed with Fourier transform infrared, electron spectroscopy for chemical analysis, and morphology analysis. It was concluded that the diffusion time for the in situ polymerization of PANI in electrospun fiber webs was optimized at approximately 3 h. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 983–991, 2005