Neat Polyamide 6 Research Articles

Preparation and wear resistance of Ti–Zr–Ni quasicrystal and polyamide composite materials

Ti–Zr–Ni icosahedral quasicrystal powders (Ti-QC), prepared by mechanical alloying and then annealing in a vacuum furnace, were used as a novel filler material in polyamide 12 (PA12). The melt processability of the composite was studied using a Haake torque rheometer. This indicates that PA12/Ti-QC composites can be melt-processed into a wear-resistant material. Further, these composites, fabricated by compression molding, were tested in sliding wear against a polished bearing steel counterface. The results from wear testing show that the addition of Ti-QC filler to PA12 enhances wear resistance and reduces volume loss by half compared with neat PA12. Furthermore, it is found that the hardness of the composite increases with increasing content of Ti-QC filler. In addition, PA12/Ti-QC composites exhibit a slightly higher crystallization temperature and better thermal stability than PA12. These combined results demonstrate that Ti-QC filler may be a desirable alternative when attempting to increase the wear resistance of PA12.

Single polymer composites by partially melting recycled polyamide 6 fibers: Preparation and characterization

AbstractRecycled polyamide 6 (PA6) cloth was used as the only raw material to prepare single polymer composites (SPC) by partially melting the PA6 fibers. During the process, part of PA6 fibers was melted to fill the gap between the remained fibers at a temperature in the melting temperature range of fibers. The matrix was in situ formed by recrystallization of the molten part and bonded the remained unmolten fibers together with cooling. Effects of a critical parameter, processing temperature (222–228°C), on the partially melting behavior of PA6 fibers and the properties of the resulting SPC were investigated by differential scanning calorimetry (DSC), scanning electron microscope (SEM), and tensile tests. As a result, at the processing temperature of 226°C, 31% of PA6 fibers were exactly molt to form the matrix and the tensile strength of prepared SPC achieved a maximal value of 138 MPa that was 105% higher than the one of neat PA6. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of carbon fibre content on friction and wear properties of carbon fibre reinforced PA6 composites

The tribological performance of polyamide 6 (PA6) and carbon fibre reinforced PA6 (CF/PA6) under dry sliding condition was examined. Different contents of CFs were employed as reinforcement. All filled and unfilled PA6 composites were tested against CGr15 ball, and representative testing was performed. The effects of CF content on the friction and wear properties of the composites were investigated. The worn morphologies of neat PA6 and its composites were examined by SEM, and the wear mechanisms were discussed. Moreover, all filled PA6 have superior tribological characteristics to unfilled PA6. The optimum wear reduction was obtained when the CF content is 20 vol.-%.

Polyamide 6 composites reinforced with silicon nitride whiskers: Synthesis, interface interaction, and mechanical properties

AbstractIn this study, polyamide 6 (PA6)/silicon nitride whisker (SNW) composites were fabricated via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam. By this novel method, SNWs can be dispersed uniformly in PA6 matrix. The interface interaction between SNW and PA6 was investigated, and the reinforcing efficiency of SNW on PA6 was evaluated. It was revealed by Fourier transform infrared spectroscopy that a large amount of polar groups, such as SiOH, NH, and NH2, were present on the SNWs, by which hydrogen bonding and covalent bonding can be formed at interface. Mechanical test showed that at a loading of 5.0 wt % SNW, the tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength of PA6/SNW composite were 37.9, 80.5, 60.3, 73.9, and 64% higher than those of neat PA6, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Aromatic–aliphatic polyamide/montmorillonite clay nanocomposite materials: Synthesis, nanostructure and properties

New type of aromatic–aliphatic polyamide/montmorillonite nanocomposites were produced using solution intercalation technique in dimethylacetamide. The modification of clay was carried out with ammonium salt of long chain alkyl amine. The nanocomposites were probed for organoclay dispersion, mechanical, thermal and water absorption measurements. Formation of delaminated and intercalated nanostructures was confirmed by X-ray diffraction and TEM studies. Improvement in tensile strength and modulus was observed for nanocomposites with optimum organoclay content (8-wt.%). Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. Differential scanning calorimetric results revealed increase in glass transition temperatures ( T g ) with augmenting organoclay in the nanocomposites. Water uptake of the nanocomposites reduced than the neat polyamide rendering decreased permeability.

Investigating the structure–property relationship of aromatic–aliphatic polyamide/layered silicate hybrid films

Surface treated montmorillonite was used to prepare nanocomposites with aromatic–aliphatic polyamide by solution intercalation technique. The polyamide chains were produced through polycondensation of 4-aminophenyl sulfone with sebacoyl chloride in dimethyl acetamide. Compatibility between the polymer and organoclay was achieved through carbonyl chloride end-capped amide chains prepared by adding extra sebacoyl chloride near the end of polymerization reaction. The nanocomposites morphology and clay dispersion were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Delaminated and intercalated morphologies were observed for different loading of organoclay. Tensile strength and modulus improved for nanocomposites with optimum organoclay content (10-wt.%). Thermal stability and glass transition temperature of nanocomposites increased relative to pristine polyamide with augmenting organoclay content. Water uptake of these materials decreased as compared to the neat polyamide indicating reduced permeability.

Thermal history dependence of polymorphic transformation of polyamide 6/silicate nanocomposites

BACKGROUND: Although much research has been devoted to nanocomposites of polyamide 6 (PA6) with inorganic nanoparticles, most research has mainly focused on the effects of clay and annealing temperature on the crystallization behavior of the PA6 matrix, but the effect of annealing on the thermal behavior of PA6/clay nanocomposites remains an interesting subject which requires further investigation. This paper focuses on the effects of thermal history on the polymorphic transformation of PA6 and PA6/layered silicate nanocomposites (PA6LSN). RESULTS: It was found that PA6 and PA6LSN exhibit a similar polymorphic behavior when they were annealed at 190 °C. As the annealing temperature was elevated to 230 and 250 °C, significant differences in polymorphic transformation and thermal behavior between PA6 and PA6LSN could be observed. For example, the γ phase became the dominant crystalline phase for PA6LSN samples while the α crystal was still the predominant phase in neat PA6. Furthermore, a higher temperature endothermic peak observed at around 236 °C in all PA6LSN modulated differential scanning calorimetry scans was also found to be strongly dependent on the cooling rate and annealing temperature. CONCLUSION: The thermal history has a strong influence on the polymorphic transformation of PA6 and PA6LSN. For the first time, the effect of thermal history on the high-temperature endothermic peak of PA6LSN was investigated and it was observed that this peak is also strongly dependent on the thermal history. Copyright © 2009 Society of Chemical Industry

Investigation of nanostructure and properties of aromatic–aliphatic polyamide‐based nanocomposites with clay additives

AbstractAromatic–aliphatic polyamide/clay nanocomposites were produced using solution intercalation technique. Surface modification of the clay was performed with ammonium salt of aromatic diamine and the polyamide chains were produced by condensation of 4‐aminophenyl sulfone with sebacoyl chloride (SCC) in dimethyl acetamide. Carbonyl chloride endcapped polymer chains were prepared by adding extra SCC near the end of polymerization reaction. The nanocomposites were investigated for organoclay dispersion, water absorption, mechanical, and thermal properties. Formation of delaminated and intercalated nanostructures was confirmed by X‐ray diffraction and TEM studies. Tensile strength and modulus improved for nanocomposites with optimum organoclay content (8 wt %). Thermal stability and glass transition temperatures of nanocomposites increased relative to pristine polyamide with augmenting organoclay content. The amount of water uptake for these materials decreased as compared with the neat polyamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and Characterization of Aromatic–Aliphatic Polyamide Nanocomposite Films Incorporating a Thermally Stable Organoclay

Nanocomposites were synthesized from reactive thermally stable montmorillonite and aromatic–aliphatic polyamide obtained from 4-aminophenyl sulfone and sebacoyl chloride. Carbonyl chloride terminal chain ends were generated using 1% extra sebacoyl chloride that could interact chemically with the organoclay. The distribution of clay in the nanocomposites was investigated by XRD, SEM, and TEM. Mechanical and thermal properties of these materials were monitored using tensile testing, TGA, and DSC. The results revealed delaminated and intercalated nanostructures leading to improved tensile strength and modulus up to 6 wt% addition of organoclay. The elongation at break and toughness of the nanocomposites decreased with increasing clay contents. The nanocomposites were thermally stable in the range 400–450 °C. The glass transition temperature increased relative to the neat polyamide due to the interfacial interactions between the two phases. Water uptake of the hybrids decreased upon the addition of organoclay depicting reduced permeability.

Preparation and mechanical properties of exfoliated CoAl layered double hydroxide (LDH)/polyamide 6 nanocomposites by in situ polymerization

Novel exfoliated nanocomposites based on polyamide 6 (PA6)/CoAl layered double hydroxide (CoAl-LDH) have been successfully prepared via in situ polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that the inorganic nanoplatelets of CoAl-LDH were homogeneously dispersed in the PA6 matrix. Mechanical testing (by tensile tests and nanoindentation measurements) shows that, compared with neat PA6, the tensile modulus, the yield strength, and the hardness of the nanocomposites are substantially improved by about 100%, 75%, and 25%, respectively, with incorporating only 1 wt% CoAl-LDH. In addition, tensile fracture morphologies of neat PA6 and its nanocomposites are also compared and discussed.

Diffusion behavior of water in polyamide 6 organoclay nanocomposites

Research on polymer-layered silicate nanocomposites is currently an expanding field of study because they exhibit a wide range of improved properties over their unmodified starting polymers. Polyamide 6 (PA6)/organoclay nanocomposites have been prepared by exfoliating the organoclay montmorillonite via melt mixing. The exfoliation within the nanocomposites has been monitored using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Water absorption of PA6 nanocomposites and its mechanical performance when saturated with water at temperatures rang- ing from 40 to 60°C were investigated. It was found that the organoclay up to 8 wt% was completely exfoliated and well distributed within PA6 matrix as observed by TEM and XRD analysis. Addition of organoclay did not affect the crystallinity of PA6, and better mechanical perform- ances were obtained. It was found that the barrier properties of the neat PA6 exhibited both higher diffusion coefficient and higher maximum water uptake as compared to the filled polymer. For all investigated temperatures the diffusion coefficient was found to decrease as function of organoclay loading. However, the maximum uptake was found to increase without reaching that of neat PA6. A relationship between temperature and diffusion coefficient was also established.

Rheological behaviour of nano-composites based on polyamide 6 under shear and elongational flow at high strain rates

In this work, the rheological behaviour of high molecular mass polyamide 6 (PA6)/organo-montmorillonite nano-composites, obtained via melt blending, was investigated under shear and extensional flow. Capillary rheometry was used for the measurement of high shear rate steady state shear viscosity and die entrance pressure losses; further, by the application of a converging flow method (Cogswell model) to these experimental results, elongational viscosity data were indirectly calculated. The extensional behaviour was directly investigated by means of melt spinning experiments, and data of apparent elongational viscosity were determined. The results evidenced that the presence of the organo-clay in filled PA6 melts modifies the rheological behaviour of the material, with respect to the unfilled polymer, in dependence on the type of flow experienced by the fluid. In shear flow, the nano-composites showed a slightly lower viscosity than neat PA6, whereas in elongation, they appeared much more viscous, in dependence on the organo-clay content.

Theoretical and experimental determination of tensile properties of nanosized and micron‐sized CaCO3/PA66 composites

AbstractThe objective of this research was to investigate the probability of reinforcing Polyamide66 (PA66) with both micron‐sized and nanosized calcium carbonate (CaCO3) particles. For this purpose, micron‐sized and nanosized CaCO3 particles were used as fillers to prepare microcomposites (conventional composites) and nanocomposites via a polymer solution method. The microcomposites and nanocomposites were found to have higher modulus and lower strength than neat PA66. Also, nanocomposites had higher modulus and strength than microcomposites. Theoretical prediction of elastic modulus was carried out using Rule of mixtures, Guth, Nicolais–Narkis, Hashin–Shtrikman, and Halpin–Tsai equations. Calculated results show that these equations cannot predict the results accurately for the work carried out. However, these models can be used with confidence for the prediction of elastic modulus as experimental data are higher than the calculated values. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Influence of extrusion temperature on thermal properties of polyamide 6/MMT nanocomposites

The effect of processing temperature on the melt flow and thermal behaviour of polyamide 6 (PA6)/organophillic montmorillonite (MMT) nanocomposite was investigated. PA6/MMT nanocomposites were prepared by melt extrusion at five different processing temperatures. Neat PA6 was also extruded as a reference. The composites were characterised by melt flow measurement, differential scanning calorimetry, dynamic mechanical analysis and X-ray diffraction.

Polyamide 6/Layered Silicate Nanocomposites

Polyamide 6 (PA6) and its two exfoliated nanocomposites (PA6/Nf919 and PA6/BZ-COCO), with bentonite (2.5 wt.%) organophilically treated with difierent cations, were studied. Improved mechanical properties, changes in crystallinity and morphology as well as higher glass transition temperature values were observed for the nanocomposites in comparison to the neat PA6. For the nanocomposite PA6/BZ-COCO, of better surface modiflcation of platelets and better interaction between the polymeric matrix and the organobentonite, higher values of Young’s modulus and yielding point together with higher contribution of larger free volume holes to free volume distributions occurred.

Nonisothermal crystallization kinetics of ZnO nanorod filled polyamide 11 composites

Zinc oxide (ZnO) nanorods filled polyamide 11 (PA11) composites have been successfully prepared by melt-blending. Nonisothermal melt crystallization kinetics of PA11 and its nanocomposites is investigated using differential scanning calorimetry (DSC) under different cooling rates. With increasing the content of ZnO nanorods, the crystallization rate of PA11 decreases. The nonisothermal crystallization behavior was analyzed by Avrami, Ozawa and modified Avrami–Ozawa methods. It was found that the Ozawa method failed to describe the nonisothermal crystallization behavior of PA11 and ZnO composites. Avrami analysis reveals two liner regions for all cooling rates studied. In the primary crystallization process, the values of Avrami exponent n are about 3.4. And in the secondary crystallization, the n is about 1.8, which is characteristic of perfection of crystals. The combined kinetic method was able to describe the nonisothermal crystallization behavior of PA11 and its composites much effectively. In addition, the activation energies of nonisothermal crystallization are determined using Takhor model. The results show that the crystallization activation energy of PA11/ZnO composites is lower than that of neat PA11.

Preparation and characterisation of polyamide–polyimide organoclay nanocomposites

AbstractBACKGROUND: Ternary nanocomposites containing an organomodified layered silicate polyimide additive within a polyamide matrix have been investigated to gain greater insight into structure–property relationships and potential high‐temperature automotive applications.RESULTS: Polyamide nanocomposite blends, containing 3 wt% of organoclay, were prepared and compared with organoclay‐reinforced polyamide and neat polyamide. Nanoclay addition significantly increased heat distortion temperature, as well as both the tensile and flexural moduli and strength. The addition of polyimide demonstrated further increases in heat distortion temperature, glass transition temperature and the flexural and tensile moduli by about 17, 21 and 40%, respectively. The tensile and flexural strengths were either unaffected or decreased modestly, although the strain‐to‐failure decreased substantially. Morphological studies using transmission electron microscopy (TEM) and X‐ray diffraction showed that the nanoclay was dispersed within the ternary blends forming highly intercalated nanocomposites, regardless of the presence and level of polyimide. However, TEM revealed clay agglomeration at the polyamide–polyimide interface which degraded the mechanical properties.CONCLUSIONS: A range of improvements in mechanical properties have been achieved through the addition of a polyimide additive to a polyamide nanocomposite. The decrease in ductility, arising from the poor polyamide–polyimide interface and nanoclay clustering, clearly requires improving for this deficiency to be overcome. Copyright © 2008 Society of Chemical Industry

Orientation and the extent of exfoliation of clay on scratch damage in polyamide 6nanocomposites

The major objectives of this work are to understand the effects of organoclay, its extent ofexfoliation and orientation, and indenter geometry on the scratch characteristics ofpolyamide 6/organoclay nanocomposites. Two different organically treated clays are usedfor this purpose and their structural parameters in a polyamide 6 matrix quantified. It isshown that, while the material properties are important for scratching resistance, they arenot the only determinants of the scratch performance of materials. Further, despite provingbeneficial to scratch resistance, in terms of residual depth, the presence (and exfoliation) oforganoclay promotes the formation of brittle cracks during scratching. But with noorganoclay layers, plastic flow controls the scratch damage in neat polyamide 6 with largeresidual depths. Factors such as orientation of clay layers and variations of indentertip geometry also exert dominant effects on scratch penetration resistance anddamage. Additionally, significant plastic flow and rotation of organoclay layersfrom the original configuration are observed underneath the sliding indenter.

Rheology of a low-filled polyamide 6/montmorillonite nanocomposite

The rheological properties of a polyamide 6/clay nanocomposite with a low loading of clay (1 wt %) were studied. Linear viscoelastic measurements in oscillatory and steady shear with small strain amplitudes were carried out. The nanocomposite exhibited a higher elastic modulus, viscous modulus, and complex viscosity than neat polyamide 6 during dynamic and steady shear tests. Moreover, the addition of clay resulted in a reduction of the critical strain amplitude, an increase of the loss angle, and a reduction of the frequency at the intersection of the elastic and viscous moduli. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Preparation of Semi-aromatic polyamide(PA)/multi-wall carbon nanotube (MWCNT) composites and its dynamic mechanical properties

Well dispersed semi-aromatic polyamide(PA)/multi-wall carbon nanotube (MWCNT) composite was prepared through high-speed shearing method in the presence of surfactant sodium dodecylbenzene sulfonate (SDBS). Further analysis of morphology, crystallization, and dynamical mechanical properties shows the presence of SDBS helps to disperse the MWCNT and largely enhance the mechanical property. In comparison with neat PA component, the storage modulus (E′) of the blend system at 90 °C is 3.5 times larger than PA with MWCNT load ratio of 3 wt.%; and meanwhile the glass transition temperature (Tg) of PA component increases about 17 °C; Similar phenomena have not found in MWCNT/PA composite without surfactant. Simultaneously, as DSC and morphology measurements indicate, the filled MWCNT does not show tremendous effect on the crystalline phase and crystallinity of PA, which imply that the increasing mechanical property for composites is due to the strengthening effect of MWCNT itself, not being caused by the change of crystalline phase and crystallinity by the addition of MWCNT. The increasing Tg, indicative of the restricting movement of PA chains, is most probably ascribe to the strong interaction presented between MWCNT and PA chains.