Molecular dynamics and mechanical properties correlations of PA6/PPO blends compatibilized with SMA

The effects of the compatibilizer, styrene maleic anhydride (SMA‐8% MA) upon the change of morphology and molecular dynamics of polyamide‐6 (PA6) and poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends were investigated by means of solid‐state NMR techniques. With increasing amounts of SMA, the domains correspond to PA6 and PPO are reduced and the polymer segmental mobility increased. The correlation between NMR relaxation time, T, and the bulk mechanical properties provide a molecular level understanding of the modification of molecular dynamics by the compatibilizer (SMA). The correlation shows that the tensile strength is governed mainly by the morphology, but modulated by the PA6 crystallinity, while the tensile elongation and impact strength are closely affected by both the molecular mobility and morphology. The annealing process improved only the tensile strength, but deteriorated tensile elongation and impact strength due to the increase of PA6 crystallinity, which induced phase separation after annealing. This study raised an important point that the polymer mechanical properties are most sensitive to the molecular structure and dynamics take place within the range of 20 Å to few hundred Å. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1155–1163, 1999     

The mechanical properties of plasma‐treated carbon fiber reinforced PA6 composites with CNT

The aim of this work is the evaluation of the effects of plasma treatment and the addition of CNT on the mechanical properties of carbon fibre/PA6 composite. A powder impregnation process with integrated inline continuous plasma of carbon fibers was used to produce CF/PA6 composite. CF/PA6 composite was processed into test laminates by compression moulding, and interface dominated composite properties were studied. The tensile and impact strength of composites containing CNT and plasma‐treated carbon fibres improved obviously. The tensile strength of nanocomposite largely increases with the increasing of the CNT content and then decreases when the CNT content is over 2%. The hydroxyl groups of the fibers surface are in favor of the wettability of carbon fibers by the polar matrix resin, which is resulting in a further interaction of the fiber surface with the curing system of the matrix resin.     

The interlaminar shear strength and tribological properties of PA 6 composites filled with graphene oxide‐treated carbon fiber

The objective of this work is to improve the interlaminar shear strength and tribological properties of the PA 6 composites by graphene oxide‐treated carbon fiber (CF) and ultraviolet irradiation of PA 6. The morphologies of untreated and treated CFs were characterized by X‐ray photoelectron spectroscopy. Surface analysis showed that after treatment, the surface of CFs chemisorbed oxygen‐containing groups; active carbon atom, the surface roughness, and wetting ability were increased. The results show that the treated CF composites can possess excellent interfacial properties and tribological properties accordingly after treatment. Copyright © 2017 John Wiley & Sons, Ltd.     

Phenomenological approach to compare the crystallization kinetics of isotactic polypropylene and polyamide‐6 under pressure

Reliable experimental data for semicrystalline polymers crystallized under pressure are supplied on the basis of a model experiment in which drastic solidification conditions are applied. The influence of the pressure and cooling rate on some properties, such as the density and microhardness, and on the product morphology, as investigated with wide‐angle X‐ray scattering (WAXS), is stressed. Results for isotactic polypropylene (iPP) samples display a lower density and a lower microhardness with increasing pressure over a wide range of cooling rates (from 0.01 to 20 °C/s). Polyamide‐6 (PA6) samples exhibit the opposite behavior, with the density and microhardness increasing at higher pressures over the entire range of cooling rates investigated (from 1 to 200 °C/s). A deconvolution technique applied to iPP and PA6 WAXS patterns has allowed us to evaluate the final phase content and to assess the crystallization kinetics. A negative influence of pressure on the α‐crystalline phase crystallization kinetics can be observed for iPP, whereas a slightly positive influence of pressure on the crystallization kinetics of PA6 can be noted. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 153–175, 2002     

PPO及其改性物在低于玻璃化转变退火时的热行为研究

用DSC法研究了聚苯醚(PPO)、羧化度为16.0mol%的羧化PPO(C-PPO)和相应的C-PPO的正十二酯(Et-CPPO)在稍低于玻璃化转变温度等温退火的热焓松弛行为,讨论改性基团对热焓松弛速率的影响。发现三种样品在等温退火过程中产生的吸热峰随退火时间或温度的增加而增加。在相同退火条件下,峰宽随侧基链加长而增加,热焓松弛速率降低。     

Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends

The nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009     

Water‐soluble poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) copolymer: Synthesis and characterization

Water‐soluble and photoluminescent block copolymers [poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) (PEO‐b‐PPV)] were synthesized, in two steps, by the addition of α‐halo‐α′‐alkylsulfinyl‐p‐xylene from activated poly(ethylene oxide) (PEO) chains in tetrahydrofuran at 25 °C. This copolymerization, which was derived from the Vanderzande poly(p‐phenylene vinylene) (PPV) synthesis, led to partly converted PEO‐b‐PPV block copolymers mixed with unreacted PEO chains. The yield, length, and composition of these added sequences depended on the experimental conditions, namely, the order of reagent addition, the nature of the monomers, and the addition of an extra base. The addition of lithium tert‐butoxide increased the length of the PPV precursor sequence and reduced spontaneous conversion. The conversion into PPV could be achieved in a second step by a thermal treatment. A spectral analysis of the reactive medium and the composition of the resulting polymers revealed new evidence for an anionic mechanism of the copolymerization process under our experimental conditions. Moreover, the photoluminescence yields were strongly dependant on the conjugation length and on the solvent, with a maximum (70%) in tetrahydrofuran and a minimum (<1%) in water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4337–4350, 2005     

Synthesis and characterization of polytulipalin‐g‐polylactide copolymers

Graft copolymers of poly(tulipalin A) (PT) and poly(DL‐lactide) (PDLLA) (PT‐g‐PDLLA) having various graft lengths and ratios were synthesized by free‐radical copolymerization of α‐methylene‐γ‐butyrolactone (MBL) and PDLLA macromonomers (HEMA‐PDLLA) terminated by 2‐hydroxyethyl methacrylate (HEMA)‐terminated. HEMA‐PDLLA were synthesized by ring opening polymerization (ROP) of DL‐lactide in the presence of HEMA. Both HEMA‐PDLLA and the copolymers were characterized by NMR spectroscopy and gel permeation chromatography (GPC). The thermal properties of the graft copolymers were found to depend on the graft length and the ratio. The copolymers consisting of PDLLA side chains of M_n = 500 Da showed a single T_g between T_gs of the two component polymers, suggesting a miscible state of PT and PDLLA. In contrast, the copolymers consisting of PDLLA side chains of M_n = 1100, 2000, and 7000 Da showed two isolated T_g, suggesting two segregated domains. The AFM phase images of the copolymers supported the single and phase‐separated morphologies for the former and latter systems, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Morphology and fracture behavior of toughening‐modified poly(vinyl chloride)/organophilic montmorillonite composites

Toughening‐modified poly(vinyl chloride) (PVC)/organophilic montmorillonite (OMMT) composites with an impact‐modifier resin (Blendex 338) were prepared by melt intercalation, and their microstructures were investigated with wide‐angle X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The mechanical properties of the PVC composites were examined in terms of the content of Blendex and OMMT, and the fracture toughness was analyzed with a modified essential work of fracture model. Intercalated structures were found in the PVC/OMMT composites with or without Blendex. Either Blendex or OMMT could improve the elongation at break and notched impact strength of PVC at proper contents. With the addition of 30 phr or more of Blendex, supertough behavior was observed for PVC/Blendex blends, and their notched impact strength was increased more than 3319% compared with that of pristine PVC. Furthermore, the addition of OMMT greatly improved both the toughness and strength of PVC/Blendex blends, and the toughening effect of OMMT on PVC/Blendex blends was much larger than that on pristine PVC. Blendex and OMMT synergistically improved the mechanical properties of PVC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 286–295, 2004     

Glass‐formation kinetics of miscible blends of atactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

We present a detailed investigation of the kinetics associated with the glass transitions of miscible blends composed of atactic polystyrene (a‐PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). According to both dynamic mechanical analysis and differential scanning calorimetry, relaxation times displayed an enhanced temperature dependence (i.e., more fragile or more cooperative behavior) for the blends compared with additive behavior based on the responses of neat a‐PS and PPO. This is consistent with the notion that specific interactions between the blend components heighten the intermolecular cooperativity. The compositional dependence of fragility provided insight into physical aging results for the properties of volume and enthalpy. The combination of our research and a previously reported pressure–volume–temperature study by Zoller and Hoehn (J Polym Sci Polym Phys Ed 1982, 20, 1385) provided evidence that the observation of increased glassy densities for the blends compared with those of the pure polymers was kinetic in origin and was not a feature of the thermodynamics of miscibility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2118–2129, 2001     

The influence of polypyrrole coatings on the mechanical and friction and wear properties of bamboo fiber filled PA6 composites

The effects of polypyrrole coatings on the tensile and tribological properties of bamboo fiber reinforced polyamide 6 (PA6) composites were studied. Tribological tests were conducted using a block‐on‐ring arrangement. It was observed that the polypyrrole coatings played a main role in the tensile‐resistant and wear‐resistant properties of the PA6 composites. The tensile properties were ruled by the fiber‐matrix adhesion. And the excellent tribological performance of the fillers improved the tribological properties of PA6 composites. The optimum content of polypyrrole coating concentration is 7vol%.     

Flame-retarded mechanism of SEBS/PPO composites modified with mica and resorcinol bis(diphenyl phosphate)

The flame retardancy of styrene-b-ethylene/butylene-b-styrene triblock polymer (SEBS)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends was greatly improved by the combined use of mica and resorcinol bis(diphenyl phosphate) (RDP). The limiting oxygen index (LOI), vertical burning and cone calorimeter test were performed to evaluate the flame-retarded effect. The composite of SEBS/PPO/maleic anhydride grafted SEBS (SEBS-g-MAH) with a mass ratio of 11/11/3 passed a V-0 rating in the UL94 test by the addition of 10–15 wt% mica and 15–10 wt% RDP with total amount of 25 wt%. The synergism was confirmed by the mathematical evaluation of the synergistic effect index (SE) in LOI, the residue, the peak heat release rate (PHRR) and the total heat evolved (THE) per mass loss (THE/ML). The flame-retarded mechanism of the composite was also proposed on the results of cone calorimeter test, TGA-FTIR, SEM micrographs and SEM/EDS analysis of the residues. It was found that the degradation rate of SEBS/PPO/SEBS-g-MAH matrix was slowed down, a more consolidated char layer with higher residue was promoted by the combination of RDP and mica. The flame-retardancy of RDP with mica in SEBS/PPO/SEBS-g-MAH matrix was synergistic through gas and condensed phase action.     

Mechanical properties and structural characteristics of PP/PP‐g‐SBR nanocomposites prepared by dynamical photografting

Poly(propylene) (PP)/PP grafted styrene‐butadiene rubber (PP‐g‐SBR) nanocomposite was prepared by blending PP with PP‐g‐SBR using dynamical photografting. The crystal morphological structure, thermal behavior, and mechanical properties of PP/PP‐g‐SBR nanocomposites have been studied by photoacoustic Fourier transform infrared spectroscopy (PAS‐FT‐IR), wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and mechanical measurements. The data obtained from the mechanical measurements show that the PP‐g‐SBR as a modifier can considerably improve the mechanical properties of PP/PP‐g‐SBR nanocomposites, especially for the notched Izod impact strength (NIIS). The NIIS of the nanocomposite containing 2 wt% PP‐g‐SBR measured at 20°C is about 2.6 times that of the control sample. The results obtained from PAS‐FTIR, WAXD, SEM, and DSC measurements revealed the enhanced mechanism of impact strength of PP/PP‐g‐SBR nanocomposites as follows: (i) the β‐type crystal of PP formed and its content increased with increasing the photografting degree of PP‐g‐SBR; (ii) the size of PP‐g‐SBR phase in the PP/PP‐g‐SBR nanocomposites obviously reduced and thus the corresponding number of PP‐g‐SBR phase increased with increasing the photografting degree of PP‐g‐SBR. All the earlier changes on the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP at low temperature. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6‐dimethyl‐1,4‐phenylene oxide)

An investigation on the effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is presented. Sulfonated PPO (SPPO) was prepared using chlorosulfonic acid as a sulfonating agent. The structure of SPPO was confirmed by FT‐IR, and the ion exchange capacity (IEC) of SPPO was accurately determined by conductometric titration and ¹H‐NMR. The three‐dimensional solubility parameters of SPPO defined by Hansen were estimated by group contribution, and this approach was used to obtain the three coordinates of a solubility parameter in terms of: a dispersion part δ_d, a polar part δ_p and a hydrogen bonding part δ_h. The theoretical predications of solubility behavior were characterized using “soluble sphere” in three‐dimensional space. The estimated results were in accordance with the solubility experiments in different solvents. Copyright © 2006 John Wiley & Sons, Ltd.     

Synergistic effect of polyfunctional silane coupling agent and styrene acrylonitrile copolymer on the water‐resistant and mechanical performances of glass fiber–reinforced polyamide 6

Adverse effects of a high‐water absorption rate on properties of a glass fiber–reinforced polyamide 6 (GF‐PA6) composite significantly reduce performance and limit application in humid environments. In this paper, a polyfunctional silane (PFS) coupling agent with amino (–NH₂) and imino (–NH) groups and styrene acrylonitrile copolymer (SAN) were added to a composite, GF‐PA6, to prepare GF‐PA6/SAN/PFS composites via melt blending in a twin‐screw extruder. The effects of SAN and PFS content on the static and dynamic mechanical properties of the composites before and after water absorption were investigated in detail. The microstructure of the fracture surface was analyzed by a scanning electron microscope (SEM). The results show that the addition of SAN and PFS could effectively inhibit water absorption of the GF‐PA6 composites. The alkoxyl groups on PFS reacted chemically with the nitrile groups of SAN, which enriched SAN on the interface between the fiber and matrix during the extrusion and mixing process to improve the effect of water prevention. Therefore, the mechanical properties of the wet state were notably improved while preventing water from permeating the interface by only the addition of a small amount of SAN and PFS. Dynamic mechanical analysis (DMA) results showed that the addition of PFS improved the compatibility of PA6 with SAN and enhanced the interface adhesion between fiber and PA6. In terms of test result of the comprehensive performance, 10 phr SAN with 0.6 phr PFS was the best dosage.     

Thermal and dynamic mechanical properties of PES/PPS blends

Blends of poly(ether-sulfone) (PES) and poly(phenylene sulfide) (PPS) with various compositions were prepared using an internal mixer at 290°C and 50 rpm for 10 min. The thermal and dynamic mechanical properties of PES/PPS blends have been investigated by means of DSC and DMA. The blends showed two glass transition temperatures corresponding to PPS-rich and PES-rich phases. Both of them decreased obviously for the blends with PES matrix. On the other hand, T_g of PPS and PES phase decreased a little when PPS is the continuous phase. In the blends quenched from molten state the cold crystallization temperature of PPS was detected in the blends of PES/PPS with mass ratio 50/50 and 60/40. The melting point, crystallization temperature and the crystallinity of blended PPS were nearly unaffected when the mass ratio of PES was less than 60%, however, when the amount of PES is over 60% in the blends, the crystallization of PPS chains was hindered. The thermal and the dynamic mechanical properties of the PPS/PES blends were mainly controlled by the continued phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of PEO‐PPO‐PEO copolymer on the mechanical and thermal properties and morphological behavior of biodegradable poly (L‐lactic acid) (PLLA) and poly (butylene succinate‐co‐L‐lactate) (PBSL) blends

A blend of two biodegradable and semi‐crystalline polymers, poly (L‐lactic acid) (PLLA; 70 wt%) and poly (butylene succinate‐co‐L‐lactate) (PBSL; 30 wt%), was prepared in the presence of various polyethylene oxide‐polypropylene oxide‐polyethylene oxide (PEO‐PPO‐PEO) triblock copolymer contents (0.5, 1, 2 wt%). Mechanical, thermal properties, and Fourier transform infrared (FTIR) analysis of the blends were investigated. It was found that the addition of copolymer to PLLA/PBSL improved the fracture toughness of the blends as shown by mode I fracture energies. It was supported by morphological analysis where the brittle deformation behavior of PLLA changed to ductile deformation with the presence of elongated fibril structure in the blend with copolymer system. The glass transition temperature (T_g), melting temperature (T_m) of PLLA, and PBSL shift‐closed together indicated that some compatibility exists in the blends. In short, PEO‐PPO‐PEO could be used as compatibilizer to improve the toughness and compatibility of the PLLA/PBSL blends. Copyright © 2010 John Wiley & Sons, Ltd.     

Positron annihilation properties of copolyimides and copolyamides with microphase‐separated structures

The positron annihilation lifetime (PAL) of a series of copolyimides and copolyamides with microphase‐separated structures was measured to investigate the effects of different hard‐segment polymers on the PAL properties of soft‐segment domains of poly(dimethyl‐siloxane) (PDMS) and poly(ethylene oxide) (PEO). The lifetime (τ₃) and intensity (I₃) of the long‐lived component are given as a function of the PDMS or PEO content for a series of copolymers, of which the density roughly obeys the additive rule except for the PDMS‐segmented copolyamides. The PDMS‐segmented copolyimides and copolyamides show much smaller I₃ values than those estimated from the additive rule. The lifetime distribution of the long‐lived component for the PDMS‐segmented copolyamides is composed of two components. The longer‐lifetime component is attributed to pure PDMS domains, and the shorter‐lifetime component is attributed to the polyamide domains, intermediate phases, and PDMS domains containing small amounts of short amide blocks. Despite the high PDMS content, the latter component is rather large. Thus, the positronium formation in the PDMS domains of the copolyimides and copolyamides is effectively reduced. This can be explained by the combination of the difference in the electron affinity of the PDMS and polyimide or polyamide segments and the incomplete phase separation. The PEO‐segmented copolyimides show much smaller I₃ values than those predicted from the additive rule. This is likely attributable to the effects of the intermediate phases. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1123–1132, 2000     

Double yielding in PA6/TPV‐MAH blends: Effect of crosslinking degree of the dispersed phase

Thermoplastic vulcanizates (TPVs) based on PP and EPDM (the ratio is 5:5) with different crosslinking degrees were prepared using different contents of phenolic resins, and then blended with polyamide 6 (PA6). The results indicated that with an increase in crosslinking degree, the double yielding phenomenon in PA6/TPV blends became more distinct, the yield stress of the first yield point and the yield stress difference of the two yield points decreased; however, the yield strain of the first yield point did not change with the increasing crosslinking degree of the TPV, but the yield strain of the second yield point increased, resulting in a more broadened yield region. The SEM results showed that with an increase in the crosslinking degree of TPV, the diameter of TPV increased in the core layer, and the orientation degree of TPV in the skin and subskin layer deceased, accompanying with a decrease of the ratio of length to diameter (L/D) of the droplets. The morphology evolution of the PA6/TPV blend during the tensile test was also studied, and the results agreed well with the model we proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 912–922, 2009     

Molecular composites of poly(p‐phenylene terephthalamide) anion and poly(ethylene oxide): Thermal behavior and morphology

Molecular composites, in which a small concentration of ionically modified poly(p‐phenylene terephthalamide) (PPTA) is dispersed in a poly(ethylene oxide) matrix, have been prepared. With the content of PPTA anion increasing to about 5 wt %, the glass‐transition temperature rises and the melting temperature decreases. From the equilibrium‐melting‐temperature depression data that were obtained from Hoffman–Weeks plots, the Flory–Huggins interaction parameter was determined to be negative (−1.10). These indications of enhanced miscibility between the components are attributed to intermolecular ion–dipole interactions. The presence of rigid PPTA‐anion reinforcement alters the morphology; for example, the spherulite size is reduced, and the degree of crystallinity is lowered. Possible models of how the reinforcement is incorporated into the composite are presented. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1369–1376, 2000