Preparation and Properties of Polyethylene Terephthalate (PET)/Near Infrared Reflective Pigment (NIR) Composites

A near infrared reflective (NIR, nickel antimony titanium yellow rutile) pigment filler was incorporated into a polyethylene terephthalate (PET) matrix via a melt blending approach to increase the infrared reflection of PET and limit the thermal heat accumulation in light of environmental and energy conservation concerns. Two different types of surface modifiers, polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB), were used to modify the NIR surface, as NIR–PEG and NIR–CTAB fillers, to investigate the surface modification effect. Fourier transform infrared spectroscopy (FTIR), a Zetasizer, and electron spectroscopy for chemical analysis (ESCA) results suggested a successful adsorption of the organic modifiers onto the NIR surface. Thermogravimetric analysis indicated a higher adsorption degree for the CTAB modifier than the PEG modifier due to the electronic interaction between CTAB and NIR. The thermal crystallization temperature (T_c) for neat NIR-filled samples decreased with increasing NIR content within the PET matrix at first, up to 9°C, but then tended to increase again up to a measurable difference of 6°C with respect to pure PEG, indicating the promotion of the crystallization kinetics of the neat NIR within the PET matrix. On the other hand, a decrease in T_c for all NIR-CTAB or NIR-PEG loadings was found, with the depression close to 10°C for all NIR-CTAB samples regardless of the loading. CTAB modified NIR gave the highest improvement in tensile strength and strain at break in comparison with NIR and NIR-PEG filled samples. The near infrared reflection values of modified PET were higher than those of neat PET. The reflection values appeared to be the highest for some concentrations of the NIR-CTAB filled samples, but were of similar orders of magnitude with those for NIR or NIR-PEG filled samples.     

Effect of Inorganic Fillers on Morphology and Mechanical Properties of PA66/POE-g-MAH/Filler Composites

Composites of polyamide 66 (PA66)/maleic anhydride grafted poly(ethylene-co-octene) (POE-g-MAH)/nano-calcium carbonate (nano-CaCO₃) and PA66/POE-g-MAH/talc were prepared by a one-step blending method. Morphology, crystallization, and mechanical properties of the composite materials were characterized with respect to different amounts of both inorganic fillers, nano-CaCO₃ and talc. Results showed that the tensile yield strength and tensile modulus of the composites were increased remarkably with introduction of nano-CaCO₃ or talc, but the notched impact strength was significantly lowered for both kinds of composites. Mechanical properties exhibited little difference between the PA66/POE-g-MAH/nano-CaCO₃ and PA66/POE-g-MAH/talc composites both for the different shapes and sizes of nano-CaCO₃ and the flake-like talc. Results of scanning electron microscopy exhibited agglomeration of the fillers. Differential scanning colorimetry analysis suggested that introduction of the inorganic fillers cause the crystallinity of PA66 to decrease by heterogeneous nucleation. The study provides a basic investigation on polymer/elastomer/rigid filler composites.     

THERMAL BEHAVIOR OF PP/PA6 BLENDS UNDER DYNAMIC CONDITIONS. THE EFFECT OF DIFFERENT INTERFACIAL AGENTS BASED ON CHEMICALLY MODIFIED ATACTIC POLYPROPYLENE

The thermal behavior in dynamic conditions of polypropylene/polyamide 6 (PP/PA6) blends with a modified interphase is discussed in terms of the crystallinities of the polypropylene and polyamide components imposed by the processing step conditions and after removal of those constraints by holding the blends 5 min in the molten state in the calorimeter. As interfacial agents, two based on succinic anhydride or succinil-fluoresceine grafted atactic polypropylenes were used. The experimental program was run following the Box-Wilson experimental design methodology. Thermal scans were made using round samples (5 mm diameter and 100 μm thick) cut from compression-molded sheets with morphologies and macroscopic behavior studied previously. Changes of the amount of crystallinity of each polymer in the modified blends are contrasted with the tensile strength values of the heterogeneous materials as a whole; evidence of the different roles played by each interfacial agent acting at the interface among blend components is shown.     

Non‐Isothermal Crystallization Kinetics of PA6/Attapulgite Composites Prepared by Melt Compounding

The non‐isothermal crystallization behaviors of neat polyamide 6 (PA6) and PA6/attapulgite (ATB) composites were examined using differential scanning calorimetry. The results show that ATB acts as a nucleator for PA6 matrix, accelerating the crystallization, and simultaneously obstructs the crystallization especially for the composites with higher ATB content. The analysis results using the Jeziorny and Liu equations verify the dual actions of the nucleation and the obstruction of crystallization of the ATB in the PA6 matrix. Kissinger's method is employed to obtain the activation energy of the crystallization processes; the results further indicate that the addition of ATB may also cause the above actions. It is speculated that there is a very complicated crystallization mechanism in the PA6/ATB composites based on the analysis of Avrami exponents obtained by the Jeziorny model.     

Crystallization Behavior of Rare‐earth Doped Luminous Pigment/Polyamide 6 Composites

The crystallization behavior of well‐dispersed rare‐earth doped luminous pigment/polyamide 6 (PA6) composites prepared through in situ polymerization was investigated by DSC. The rare‐earth doped luminous pigments could accelerate the forming of γ form crystals and also had a great effect on the crystallinity and crystallization rate of PA6 composites. The Ozawa, Jeziorny, and Mo methods were used to analyze the non‐isothermal crystallization kinetics. It was found that the Ozawa method was unsuitable for non‐isothermal crystallization of PA6 composites. The results of Jeziorny analysis showed that the crystallization rates of PA6 composites increased when the luminous pigment content was larger than 5 wt.%. Mo's analysis also showed that the presence of the pigment shortened the crystallization time and accelerated the crystallization rate. Polarized optical microscopy showed that the spherulites became smaller with increasing of the luminous pigment amount due to the heterogeneous nucleation.     

Morphology and Crystallization in Polystyrene/polyamide 6 Blends: Influence of a Reactive Compatibilizer and Nano-TiO2

A polystyrene (PS)/polyamide 6 (PA6) (70/30, weight ratio) blend in the presence of terminal malic anhydride functionalized PS (FPS) and nano-TiO₂ were prepared using a meltmixing technique. The morphology of the blend was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallization behavior of the PA6 phase in the blend was studied using DSC techniques. The results showed that by adding 7.5 phr nano-TiO₂, the size of the dispersed PA6 domains was dramatically decreased; An additional 1.5 phr FPS to the PS/PA6/TiO₂ blend, for reactive blending, caused the size of the dispersed PA6 domain to become even smaller and more uniform, and a weak, broad crystallization exotherm of PA6 was observed. However, the degree of crystallinity of PA6 in PS/PA6/TiO₂/FPS blend was sharply increased.     

Effects of Carbon Nanotubes on the Morphology and Properties of Uncompatibilized and Maleic Anhydride-grafted Polypropylene-compatibilized Polyamide 6/Polypropylene Blends

The effects of carbon nanotubes (CNTs) on the morphology of uncompatibilized and maleic anhydride-grafted polypropylene (MAPP)-compatibilized polyamide 6 (PA6)/polypropylene (PP) (70/30 w/w) blends prepared using a torque rheometer were investigated. TEM observations showed that the CNTs were selectively located in the major PA6 phase and at the interface. Such localization of nanofillers in the literature usually leads to a refinement in a sea-island morphology. Unexpectedly, our results show that increasing amounts of CNTs in the samples prepared using a torque rheometer led to a transformation from typical sea-island morphology to co-continuous morphology for uncompatibilized PA6/PP blends and to partial fibrillization of the PP domains for MAPP-compatibilized PA6/PP blends. These unusual morphological changes are attributed to a retarded morphology evolution process caused by the CNTs. According to rheological measurements and theoretical analysis, this was achieved through the role of CNTs in enhancing the viscoelasticity of the PA6 phase and promoting interfacial slip. The electrical resistivites, crystallization, and melting behavior of all samples were also studied.     

Isothermal Crystallization Properties of Polyamide 6 / Hexagonal Boron Nitride Nanocomposites

Hexagonal boron nitride was adopted as a heterogeneous nucleation agent to fabricate polyamide 6 based nanocomposite films via a solution casting method. Isothermal crystallization behaviors of the as-prepared films were measured by using differential scanning calorimetry. Results showed that both the crystallization temperature and fillers loading greatly affected the crystallization process of the as-prepared samples. The crystallization nucleation and growth mechanism did not change during the initial stage of crystallization. The halftime of crystallization gradually increased with increasing crystallization temperature. Moreover, it decreased first and then increased with increasing the fillers loading at low crystallization temperature, while it decreased gradually at high crystallization temperature. Furthermore, the crystallization activation energy of the as-prepared samples gradually decreased with increasing fillers loading.     

Mechanical Properties,Rheology, and Crystallization of Epoxy-Resin-Compatibilized Polyamide 6/Polycarbonate Blends: Effect of Mixing Sequences

Blends of polyamide 6 (PA6)/polycarbonate (PC)/epoxy resin (EP) were melt blended with three different mixing sequences. Their mechanical properties, crystallization, and rheological behaviors, as well as the morphology, were investigated via mechanical testing, differential scanning calorimetry (DSC), dynamic rheometry, and scanning electron microscopy (SEM). It was noted that the mixing sequences affected the distribution of EP in the PA6 matrix, as well as the reactivity of EP with PA6 and PC. Mechanical testing showed that the blends prepared by the first (S₁, blending PA6, PC, and EP simultaneously) and second mixing sequences (S₂, blending PC with a premixture of PA6/EP) had higher notched Izod impact strengths due to the formation of PA6-EP-PC block copolymer (named as the AEC structure) during compounding, as evidenced by the results of dynamic rheology and SEM. Whereas for the third sequence (S₃, blending PA6 with a premixture of PC/EP), EP could barely react with PA6 and PC, leading to little formation of AEC structure, which resulted in a poor notched Izod impact strength of the blends. The incorporation of EP actually acted as a plasticizer to improve the elongation at break of the S₃ blends. In addition, the DSC results and SEM observations showed that there were distinct differences in the crystallization and morphology of the samples prepared by the different mixing sequences.     

Effect of pre-irradiation PPO-grafted maleic anhydride on structure and properties of PPO-g-MAH/PA66 blends

The pre-irradiation polyphenylene oxide (PPO)-graft-maleic anhydride (PPO-g-MAH) was carried out by reactive extrusion. The chemical structure of PPO-g-MAH was characterized by means of Fourier-transform infrared spectroscopy. The wettability of PPO-g-MAH was characterized by the contact angle method. The blends of PPO-g-MAH/polyamide 66 (PA66) were prepared. Compared with the PPO/PA66 blends, mechanical properties of PPO-g-MAH/PA66 blends were distinctly improved. Smaller dispersed particle sizes with narrower distribution were found in PPO-g-MAH/PA66 blends, via field-emitted scanning electron microscopy. Rheological properties of PPO-g-MAH/PA66 blends were studied with a rotational rheometer.     

Simultaneously Enhancing Mechanical Properties and Melt Flow Ability of Polyamide 6 by Blending with a Hyperbranched Polymer

A series of polyamide 6/hyperbranched polymers (PA6/HBP) blends with different HBP contents was prepared by melt processing using a twin-screw extruder. The HBP was synthesized on the basis of pentaerythritol and dimethyl terephthalate according to a one-step method. The melt flow behavior, crystallization behavior, morphology, and mechanical properties of the PA6/HBP blends were investigated. The results showed that the melt flow index of the blends was greatly improved by a small amount of HBP. The yield strength, tensile modulus, Izod impact strength, and flexural strength of samples were simultaneously enhanced from 54.6 MPa, 0.5 GPa, 3.8 kJ/m², 56.9 MPa for pure PA6 to 61.1 MPa, 0.7 GPa, 5.3 kJ/m², 67.1 MPa for PA6 blends with 2.0 wt% HBP, respectively. The PA6/HBP blends showed the higher content of α-form crystal and a higher degree of crystallinity than those of pure PA6.     

Ultrasound Assisted Development of Structure and Properties of Polyamide 6/Montmorillonite Nanocomposites

In this paper, polyamide 6/montmorillonite nanocomposites (PA6CNs) were prepared via conventional and an ultrasonic extrusion technology developed in our laboratory. The structure and morphology of montmorillonite dispersed in conventional and ultrasonicated PA6CNs were studied by x‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The experimental results gained by XRD, differential scanning calorimetry (DSC), and polarizing optical microscopy (POM) showed that the dispersed morphology of montmorillonite plays an important role in the crystalline form, nucleation rate, crystallization temperature, crystallinity, and spherulite size of PA6 crystals. The ductility of conventional PA6CNs decreases with the addition of montmorillonite because of the presence of large, stacked montmorillonite particles. Compared with the conventional PA6CNs, the elongation at break and impact strength of the ultrasonicated PA6CN increase greatly due to the improved dispersion of montmorillonite and decreased size of spherulites, while also showing the higher yield strength. Thermogravimetric analysis (TGA) revealed a decrease in thermal stability of conventional PA6CNs, with the introduction of ultrasound further accelerating thermal decomposition. A possible explanation for the observed decrease in polymer thermal stability on ultrasonic treatment is provided.     

Adhesion in polyamide/compatibilizer/polypropylene systems

The effect of compatibilization on the adhesion, fracture toughness, morphology, and mechanical properties of isotactic polypropylene (PP)/polyamide 6 (PA) blends was investigated. Maleic anhydride (MAH) functionalized poly-(ethylene-co-vinyl acetate) (EVA-g-MAH) and nonreactive EVA copolymer were used as compatibilizers in binary blends. An attempt of in situ compatibilization via addition of pure maleic anhydride to PA/EVA/PP melt was also made. The blends containing maleated EVA copolymer showed more regular and finer dispersion of phases, better adhesion at the interface, and improved mechanical properties.     

Effects of Blend Ratio on Rheology,Morphology, Mechanical and Oil-Resistant Properties in Chlorinated Polyethylene Rubber and Copolyamide Blends

The elastomeric chlorinated polyethylene (CPE) blended with a low melting point copolyamide (PA6/PA66/PA1010, PA) was prepared by a melt mixing technique. The mixing characteristics of the blends were analyzed from the rheographs. The influence of copolyamide (PA) content on the morphology, mechanical properties, crystallization and oil-resistance, and the addition of compatibilizers on the mechanical properties were also systematically investigated. Morphological examinations clearly revealed a two-phase system in which CPE/PA blends exhibit a cocontinuous morphology for 50/50 composition, and the continuous phase of PA turns into a disperse phase for 70/30, 80/20, and 90/10. There is a distinct interface between the two phases. The mechanical properties, crystallization, and oil-resistance have a strong dependence on the amount of PA. The blends with higher proportions of PA have superior mechanical properties; they are explained on the basis of the morphology of the blend and the cystallinity of PA. In addition, compatibilizers, including chlorinated polyethylene-graft-copolyamide (CPE-G-PA), chlorinated polyethylene-graft-maleic anhydride (CPE-G-MAH), ethylene-n-butyl acrylate-monoxide (EnBACO), and ethylene-n-butyl acrylate-monoxide-graft-maleic anhydride (EnBACO-g-MAH) were added into the blends. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on the basis of the total mass of the blend) of 20 wt% while the PA content is 30 wt%.     

Effect of Maleated Styrene/Ethylene-co-Butylene/Styrene on the Dispersed Particles Size and Mechanical Properties of Polyamide 6/Poly(styrene-co-acrylonitrile)/Poly(styrene-b-(ethylene-co-butylene)-b-styrene) Ternary Blends

In this study, the effect of several parameters, including composition, order of mixing, viscosity, and interfacial tension, on the phase structure and size of dispersed particles of polyamide 6 (PA6)/poly(styrene-co-acrylonitrile) SAN/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) ternary blends was investigated. Moreover, the effect of addition of different ratios of reactive SEBS (maleic anhydride grafted-SEBS) and non-reactive SEBS at a fixed order of mixing and composition of 70/15/15 (PA6/SAN/SEBS + SEBS-g-MAH) on the mechanical properties of ternary blends was examined. Scanning electron microscopy (SEM) micrographs showed that among the studied parameters, interfacial tension and viscosity of dispersed phases were the leading factors in the formation of morphology and size of dispersed droplets. Mechanical results revealed that in contrast to the expectation, formation of core/shell structure of PA6/SAN/SEBS ternary blends did not result in a significant increasing of impact strength. The highest impact strength was achieved when a 50/50 weight ratio of SEBS/SEBS-g-MAH was used.     

Effect of Phase Arrangement on Solid State Mechanical and Thermal Properties of Polyamide 6/Polylactide Based Co-polyester Blends

The main goal of this work is to correlate morphological parameters of the binary blend of polyamide 6 (PA6) and a polylactide (PLA) based biodegradable co-polyester blend (BioFlex) (scanning electron microscopy, solvent extraction method) with the solid-state mechanical properties (stress strain analysis) as well as thermal (differential scanning calorimetry) and selected physico-chemical characteristics (Fourier transform infrared spectroscopy and water uptake analysis). The blends of PA6/BioFlex were prepared in ratios of 100/0, 90/10, 75/25, 60/40, 50/50, 40/60, 25/75, 10/90 and 0/100 in wt.%. The occurrence of co-continuous morphology was observed within the range of 40 to 60 wt.% of BioFlex. Furthermore, the results show that the co-continuous morphology of PA6/BioFlex blends significantly affected both tensile (E modulus) and thermal properties (melting enthalpy) of the blends. In the case of the tensile properties, the effect of the morphological arrangement was strongly dependent on the deformation range. The presence of BioFlex in the blends reduced the crystallizability of PA6 noticeably. Co-continuous structure formation was observed to have a significant effect on the melting enthalpy of the blend. Composition morphology dependent responses were observed in the case of the FTIR and water uptake studies.     

Polyamide 6/modified Carbon Black Nanocomposites Prepared via In Situ Polymerization

Polyamide 6/modified carbon black (PA6/MCB) composites were prepared via in-situ ring opening polymerization of caprolactam in the presence of dispersed carboxyl group modified carbon black (MCB). The dispersion of MCB in the PA6 matrix, nonisothermal crystallization and melting behaviors, and volume resistivity of the composites were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and a resistivity meter, respectively. The results indicated that MCB dispersed well in the PA6 matrix. When the MCB content was 5 wt%, the MCB particles were of a nanoscale. The conductivity percolation threshold of the PA6/MCB composites was 8 wt% due to the good dispersion of MCB in the PA6 matrix. The addition of MCB elevated the cold crystallization temperature of PA6, reflecting the effectiveness of MCB as nucleating agents. However, the MCB decreased the crystallization enthalpy of PA6 during both heating and cooling processes.     

CRYSTALLIZATION IN PARTIALLY MOLTEN ORIENTED BLENDS OF POLYCONDENSATES AS REVEALED BY X-RAY STUDIES*

Oriented fibers or films of binary polymer blends from polycondensates were investigated by two-dimensional (2D) wide-angle X-ray scattering (WAXS) during the finishing process of microfibrillar reinforced composite (MFC) preparation, that is, heating to a temperature between the melting temperatures of the two components, isothermal annealing, and subsequent cooling. It is shown that the crystallization behavior in such MFC from polycondensates depends not only on the blend composition, but also on thermal treatment conditions. Poly(ethylene terephthalate)/polyamide 12 (PET/PA12), poly(butylene terephthalate)/poly(ether ester) (PBT/PEE), and PET/PA6 (polyamide 6) composites were prepared in various compositions from the components. Materials were investigated using rotating anode and synchrotron X-ray source facilities. The effect of the annealing time on the expected isotropization of the lower melting component was studied in the PET/PA6 blend. It was found that PA6 isotropization took place after 2 h; shorter (up to 30 min) and longer (up to 8 h) melt annealing results in oriented crystallization due to different reasons. In PET/PA12 composites, the effect of PA12 transcrystallization with reorientation was confirmed for various blend compositions. The relative strength of the effect decreases with progressing bulk crystallization. Earlier presumed coexistence of isotropic and highly oriented crystallites of the same kind with drawn PBT/PEE blend was confirmed by WAXS from a synchrotron source.

     

The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties

The PA66-based nanocomposites containing surface-modified nano-SiO₂ were prepared by melt compounding. The interface structure formed in composite system was investigated by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The influence of interface structure on material's mechanical and thermal properties was also studied. The results indicated that the PA66 chains were attached to the surface of modified-silica nanoparticles by chemical bonding and physical absorption mode, accompanying the formation of the composites network structure. With the addition of modified silica, the strength and stiffness of composites were all reinforced: the observed increase depended on the formation of the interface structure based on hydrogen bonding and covalent bonding. Furthermore, the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the presence of modified silica could affect the crystallization behavior of the PA66 matrix and lead to glass transition temperature of composites a shift to higher temperature.     

Studies on the Blends of Polyamide66 and Thermoplastic Polyimide

The influence of the content of thermoplastic polyimide (TPI) on the structure and properties of polyamide66 (PA66)/TPI blends was studied. The results indicated that the addition of TPI showed little influence on the mechanical properties of the PA66/TPI blends, and the melting and crystallization behavior of the TPI/PA66 blends was not changed obviously. However, the addition of a small quantity of TPI significantly improved the heat resistance, and lowered the friction coefficient and the wear rate of the blends in comparison with pure PA66.