Transparent and ductile poly(lactic acid)/poly(butyl acrylate) (PBA) blends: Structure and properties

Poly(butyl acrylate) was prepared by the free radical polymerization of butyl acrylate as an initiator in the presence of 2,2′-Azoisobu-tyronitrile (AIBN) and the average molecular weight, polydispersity and thermal stability were evaluated. PLA and PBA were melt blended using a Haake Rheometer, and the light transmission, thermal properties, dynamic rheological properties, mechanical properties, phase morphology of blends and toughening mechanism were investigated. Dynamic rheology, SEM and DSC results show that the PLA is partial miscible with PBA. The PBA component improved the crystallization ability of PLA and the crystallinity of PLA increased with content of PBA (<15 wt.%). With the increase of PBA, the tensile strength and modulus of the blend decreased slightly while the elongation at break and toughness were dramatically increased. With the addition of PBA, the failure mode changes from brittle fracture of neat PLA to ductile fracture of the blend. Rheological results revealed the complex viscosity and melt elasticity of the blends decreased with increasing content of PBA and phase segregation occurred at loading above 11 wt.% PBA. UV–vis light transmittance showed that PLA/PBA blends with a high transparency, and the transmittance decreased with the amount of PBA.     

Cocontinuous morphology of immiscible high density polyethylene/polyamide 6 blend induced by multiwalled carbon nanotubes network

The effect of functionalized multiwalled carbon nanotubes (FMWCNTs) on the phase morphology of immiscible high density polyethylene/polyamide 6 (HDPE/PA6, 50/50) blend has been investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study both the morphology variation of the nanocomposites and the selective distribution of FMWCNTs in the nanocomposites. It is clear that adding small amount of FMWCNTs (<2.0 wt.%) does not exert profound influence on the sea-island morphology of the nanocomposites. However, at moderate content of FMWCNTs (2.0 and 5.0 wt.%), a typical cocontinuous morphology is detected. Further increasing FMWCNTs content (10.0 wt.%) induces phase inversion. The crystallization behaviors of both HDPE and PA6 components were investigated by using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The results show the apparent nucleation effect of FMWCNTs for PA6 crystallization due to the selective distribution of FMWCNTs in PA6 phase. Rheological measurements exhibit the presence of FMWCNTs network structure in the nanocomposites. It is suggested that the formation of the cocontinuous morphology and the novel crystallization behaviors of PA6 at high content of FMWCNTs are ascribed to the formation of the FMWCNTs network structure.     

Crystallization kinetics of polypropylene/ethylene–octene copolymer blends

Blends of polypropylene and ethylene–octene copolymers (EOC) were investigated by transmission electron microscopy, optical microscopy and differential scanning calorimetry (DSC). The main focus was on phase morphology and crystallization for blends containing EOC with different octene content (28, 37 and 52 wt.%). Also, for a given octene content (37 wt.%), the effect of molecular weight (115, 180, 229k) of EOC on morphology was observed. The largest particles were found in the blend with EOC-28 and the smallest with EOC-52. This blend with the smallest particles exhibits the fastest crystallization kinetics by two independent methods, optical microscopy and DSC. This behavior was explained by a model. Crystallizing polypropylene lamellae have to travel a longer distance going around large particles, which slows down overall crystallization growth rate. In the case of smaller particles, the obstacles are smaller and the crystallization is faster.     

Rheological,morphological, thermal,and mechanical properties of blends of vectra A950 and poly(trimethylene terephthalate): A study on a high-viscosity-ratio system

Poly(trimethylene terephthalate) (PTT) and a liquid crystalline polymer, Vectra A950 (VA), were melt-blended and subjected to capillary rheometry. Effects of VA content, shear rate and temperature on viscosity and flow activation energy (E_a) were investigated. Partial fibrillation was found even though the viscosity ratio was greater than one, leading to the formation of in-situ composites. Thermal and thermogravimetric analysis of the blends suggested that they were immiscible and their thermal stabilities were enhanced. From tensile tests, the incorporation of VA improved tensile modulus, slightly decreased tensile strength, and drastically lowered elongation at break, compared to neat PTT. It was found that the blend with the best VA dispersion can be achieved at the minimum VA content (10 wt%) and lowest processing temperature (250 °C). Not only did this blend exhibit improved mechanical properties comparable to those of blends processed at temperatures closer to the crystalline-to-nematic transition of VA (～280 °C), it also shows enhanced processibility through the reduction of both melt viscosity and E_a.     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

The Influences of Elastomer toward Crystallization of Poly(lactic acid)

Poly (lactic acid)/elastomer blends were prepared via direct injection molding. In non-isothermal crystallization scan, the crystallinity of PLA increased with a decrease in the heating and cooling rate. The melt crystallization of PLA appeared in the low cooling rate (1, 5 and 7.5°C/min). The presence of elastomer tended also to increase the crystallinity of PLA. However, it started to decrease in 30% of elastomer. It was also showed by the decreasing of cold crystallization activation energy. Elastomer also gave plasticization effect in PLA properties. Thermal treatment through annealing completed after 1 h at 80 °C. In isothermal crystallization scan, the cold crystallization rate increased with increasing crystallization temperature in the blends. The Avrami analysis showed that at low temperatures, the cold crystallization had two regime processes whereas at high temperature only one stage was observed.     

Influence of maleic anhydride grafted polypropylene on the miscibility of polypropylene/polyamide-6 blends using ATR-FTIR mapping

In this work we describe an approach to study the influence of the compatibilizer, maleic anhydride grafted polypropylene (PP-g-MAH), on the miscibility of polypropylene/polyamide-6 blends (PP/PA6) using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic mapping. In measurement, the image area for each blend was 100 μm × 100 μm. Different amounts of PP-g-MAH were introduced into the polymer blends, and the miscibility was characterized by the spatial distribution of PA6 in the image based on the corrected absorbance at 1640 cm^?1. It was found that small quantities of the compatibilizer could significantly improve the miscibility of the two immiscible polymers. Furthermore, our results proved that blend with 6 parts of PP-g-MAH by weight exhibited an optimal miscibility behavior. This paper demonstrates that ATR-FTIR mapping is a direct method to visualize the miscibility of polymer blends.     

Application of Potassium Carbonate as Space Holder for Metal Injection Molding Process of Open Pore Copper Foam

Copper foam has recently being applied to replace aluminium as heat sink. In this study, copper foam was manufactured via metal injection molding technique. Copper feedstock were prepared comprising 0 wt.%, 30 wt.% and 40 wt.% of potassium carbonate into copper powder to produce open pore cell structure, which also mixed together with a binder system consisting palm stearin (PS), polyethylene (PE) and stearic acid (SA). The feedstock was then injection molded into tensile shape test piece prior to solvent extracted in heptane prior to sintering using tube furnace at 850^oC for 4 hours in nitrogen atmosphere. The sintered samples were immersed in warm water to dissolve the carbonates. Copper foam has successfully manufactured at 850^oC for 4 hours in nitrogen atmosphere followed by the dissolution process. The porosity value increased as the addition of potassium carbonate increased from 0 to 40 wt.% which given the highest value of 52.985% porosity and thermal conductivity of 520.46 W/m.K.     

Influence of the morphology of barium sulfate nanofibers and nanospheres on the physical properties of polyurethane nanocomposites

Barium sulfate spherical agglomerates and fibers in the nanometric size range were used to prepare polyurethane (PU) nanocomposites (with 1 wt.% concentration) via melt extrusion. A detailed analysis on the effect of the morphology of the barium sulfate phase upon the mechanical, rheological and optical properties was carried out. Results show that the inclusion of the dispersed phase (with various morphologies and sizes) in the polymer matrix does not decrease the polymer mechanical properties, as is observed when particles in the micrometric size range are included. Rheological studies show that the nanocomposite containing spherical particles presents a slightly higher shear viscosity than that of the polymer matrix, in contrast to the nano-fibers viscosity which presents lower values. This is reflected in the effect of the particle morphology on the processability of the material; in contrast, the morphology has no effect on the radio-opacity of the samples. The structure and dispersion of the particles were analyzed using scanning and transmission electron microscopy. The sample with 1 wt.% nanofibers presents better processability than the system with spherical agglomerates maintaining the X-ray opacity properties.     

Are novel aryl phosphates competitors for bisphenol A bis(diphenyl phosphate) in halogen-free flame-retarded polycarbonate/acrylonitrile–butadiene–styrene blends?

The reactivity of the flame retardant and its decomposition temperature control the condensed-phase action in bisphenol A polycarbonate/acrylonitrile–butadiene–styrene/polytetrafluoroethylene (PC/ABS_PTFE) blends. Thus, to increase charring in the condensed phase of PC/ABS_PTFE + aryl phosphate, two halogen-free flame retardants were synthesized: 3,3,5-trimethylcyclohexylbisphenol bis(diphenyl phosphate) (TMC-BDP) and bisphenol A bis(diethyl phosphate) (BEP). Their performance is compared to bisphenol A bis(diphenyl phosphate) (BDP) in PC/ABS_PTFE blend. The comprehensive study was carried out using thermogravimetry (TG); TG coupled with Fourier transform infrared spectrometer (TG-FTIR); the Underwriters Laboratory burning chamber (UL 94); limiting oxygen index (LOI); cone calorimeter at different irradiations; tensile, bending and heat distortion temperature tests; as well as rheological studies and differential scanning calorimeter (DSC). With respect to pyrolysis, TMC-BDP works as well as BDP in the PC/ABS_PTFE blend by enhancing the cross-linking of PC, whereas BEP shows worse performance because it prefers cross-linking with itself rather than with PC. As to its fire behavior, PC/ABS_PTFE + TMC-BDP presents results very similar to PC/ABS_PTFE + BDP; the blend PC/ABS_PTFE + BEP shows lower flame inhibition and higher total heat evolved (THE). The UL 94 for the materials with TMC-BDP and BDP improved from HB to V0 for specimens of 3.2 mm thickness compared to PC/ABS_PTFE and PC/ABS_PTFE + BEP; the LOI increased from around 24% up to around 28%, respectively. BEP works as the strongest plasticizer in PC/ABS_PTFE, whereas the blends with TMC-BDP and BDP present the same rheological properties. PC/ABS_PTFE + TMC-BDP exhibits the best mechanical properties among all flame-retarded blends.     

The effect of gamma irradiation and particle size of CaCO3 on the properties of HDPE/EPDM blends

Mechanical blends formed of 50 wt% of high-density polyethylene (HDPE) and 50 wt% of ethylene–propylene–diene-monomer (EPDM) elastomer have been loaded with 50 wt% of three different particle size of CaCO₃, namely CaCO₃ 300, CaCO₃ 700, and CaCO₃ 2000 whereby the latter has the smallest particle size of ～311, 82 μm. Mechanical, physico-chemical and thermal properties were followed up as a function of irradiation dose for loaded and unloaded blends. The results obtained indicated that the values of tensile strength, tensile modulus at 50% elongation, gel fraction and decomposition temperature increase with increasing irradiation dose. On the other hand elongation at break, permanent set and swelling number were found to decrease with increasing irradiation dose. Moreover, the effect of particle size of CaCO₃ was observed in a limited but apparent upgrading of mechanical, physico-chemical, and thermal properties. The order of semi-reinforcing capacity of three different types of CaCO₃ is as follow: CaCO₃ 2000 > CaCO₃ 700 > CaCO₃ 300 > unloaded blend. Whereby CaCO₃ 2000 has the smallest particle size.     

Polysulfone — sulfonated poly(ether ether) ketone blend membranes: systematic synthesis and characterisation

The effect of sulfonated poly(ether ether ketone) (SPEEK) in membrane formation and separation properties has been investigated in polysulfone(PSU)/SPEEK/N-methyl-2-pyrrolidinone (NMP) systems. Charged ultrafiltration/nanofiltration membranes were obtained reliably in the range of 0.5–5 wt.% SPEEK in the polymer blend. All PSU/SPEEK blend membranes had substantially higher water flux, salt rejection, porosity and greatly reduced particle adhesion compared to the PSU base membrane. Further, all of these properties varied systematically with variation of SPEEK content. Reproducibility and stability of the membrane properties was excellent. Pore sizes determined from dextran retention data and AFM measurements showed reasonable agreement. Membranes with 5 wt.% SPEEK demonstrated excellent overall properties. Such membranes had very high permeability, 22.6±1.6×10⁻¹¹ m³ s⁻¹ N⁻¹, 0.999 fractional rejection of 4000 Da dextran, 0.65 rejection of 0.001 M NaCl, and only 0.75 mN m⁻¹ adhesion of a 4 μm silica particle. Such membranes are very promising for scale-up of production and testing on real process streams.     

Synergistic mechanical effects of calcite micro- and nanoparticles and β-nucleation in polypropylene copolymers

For improving the understanding of mechanical effects in micro- and nanocomposites based on polypropylene (PP) copolymers and precipitated or ground calcium carbonate (PCC or GCC), especially in the presence of significant portions of the β-modification, a set of compounds based on different PP grades and fillers with optional β-nucleation prepared by melt compounding was studied. A synergistic improvement of mechanical properties by a combination of calcite particles and β-nucleation was found for two of the investigated high-impact base polymers up to 20 wt.% of nanofiller. While in the past research positive toughness effects were always limited to PP homopolymers with a moderate original impact strength and to particles of less than 100 nm average diameter, the toughness of high impact ethylene–propylene impact copolymers could be increased by more than 150% even at sub-zero temperatures where the failure behaviour is determined by the disperse elastomer phase.     

Conductive poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonate [NBR-PAni.DBSA] blends prepared in solution

Blends of poly(butadiene-co-acrylonitrile) elastomer [NBR] and polyaniline dodecylbenzenesulfonate [PAni.DBSA], with electrical conductivities up to 10⁻² S cm⁻¹, have been prepared by solution mixing and casting. Miscibility was maximised for NBR with high acrylonitrile (ACN) content, as predicted on the basis of simple solubility parameter calculations. Blends prepared using NBR with 48 wt% ACN had the lowest electrical conductivity percolation thresholds, and were much more conductive than previous thermally mixed blends. Optical and electron micrographs of blends prepared from NBR 48 wt% ACN also showed the lowest levels of phase separation. The FT-IR spectra of NBR-PAni.DBSA blends resembled a superposition of the spectra of the pure materials, but with significant peak shifts due to changing intermolecular interactions between the polymers. Under DSC analysis, thermal events for blends prepared with NBR 48 wt% ACN also showed the largest temperature shifts relative to those for the pure polymers, supporting the other evidence for interaction between the two polymers.     

Morphology and properties of hollow-fiber membrane made by PAN mixing with small amount of PVDF

In this paper, the morphological structure and properties such as, miscibility, tensile strength, flux and retention ratio of hollow-fiber membranes manufactured by PAN mixing with small amounts of PVDF have been studied. The hollow fiber was made from a spinning solution composed of polymer (PAN : PVDF=10 : 0, 9 : 1, 7 : 3), additive (PVP, PEG-600) and solvent (DMAC) when immersed in water. The spinnability of blend polymer and the influences of blending on spinning technology have been observed; the morphology of membranes were examined by SEM. The blend membranes possess much higher flux than PAN membrane and fairly good retention ratio especially for the membrane made by PAN : PVDF=9 : 1.     

Effects of electron-beam irradation on some structural properties of granulated polymer blends

The aim of this article was to show the effects of the electron radiation dose and presence of a compatibiliser on the peak melting temperature (T_pm) of the crystalline phase, crystallinity (X_c), and melt flow rate (MFR) of granulated blends of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) as well as of blends of LDPE, HDPE, and PP. The purpose of applying the high-energy electron radiation with doses up to 300 kGy and of adding a compatibiliser was to enhance mechanical properties of the studied blends and, at the same time, to investigate the possibility of using this technique in the processes of recycling polymeric materials. As the compatibilisers, the styrene–ethylene/butylene–styrene elastomer grafted with maleic anhydride (SEBS-g-MA) and trimethylol propane trimethacrylate (TMPTA) were utilised; they were added at the amounts of 5, 10, and 15 wt% and 1, 2, and 3 wt%, respectively. The enhancement of mechanical properties was accompanied by the following effects, discussed in this article: (i) a decrease in the peak melting temperature upon the electron radiation for the crystalline phase of LDPE, HDPE, and PP that constituted the studied granulated blends and (ii) changes in MFR upon both the electron radiation and the addition of compatibilisers.     

Photoinduced optical anisotropy in azobenzene containing block copolymer–homopolymer blends. Influence of microstructure and molecular weight

Microstructure in two diblock methacrylic azo polymers and in some of their blends with PMMA of different molecular weights as well as their photoinduced anisotropy have been investigated. The block copolymers have similar structure but different azo content and degree of polymerization. A synthetic strategy based on a controlled radical polymerization (ATRP) of polymeric blocks and their coupling by click chemistry has been applied to obtain an azo block copolymer of high molecular weight. Microphase segregation has been observed in the block copolymers and in most of the blends. In blends of the block copolymer with lower degree of polymerization (Block 1) azo microdomains change from lamellar to spherical morphology when the azo content decreases from 24 to 3 wt.%. In the block copolymer with higher degree of polymerization (Block 2) and its blends, down to 3 wt.% azo content, spherical azo microdomains have been found. A decrease of the order parameter (η) and the photoinduced birefringence normalized to the azo content (|Δn|_norm) has been found in blends of Block 1 when the azo content decreases. However, |Δn|_norm and η values similar to those in the azo homopolymer have been observed in Block 2 and its blends. These blends can be used to lower the azo content while keeping a photoinduced response similar to that in the azo homopolymer.     

The wet phase separation: the effect of cast solution thickness on the appearance of macrovoids in the membrane forming ternary cellulose acetate/acetone/water system

We report on novel observations on the appearance of macrovoids in the ternary cellulose acetate (CA)/acetone (ACE)/water membrane forming system. The membranes are prepared by the wet phase separation whereby the cast solution is composed of ACE and polymer, and the coagulation bath is pure water only. It is found that the macrovoid formation in a 12.5 wt.% cast solution strongly depends on the cast solution thickness: macrovoids appear at the thickness of 500 μm but not at 150 and 300 μm.     

Linear viscoelasticity of poly(acrylonitrile-co-itaconic acid)/1-butyl-3-methylimidazolium chloride extended from dilute to concentrated solutions

The solution rheology of poly(acrylonitrile-co-itaconic acid) (poly(AN-co-IA)) in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) spanning dilute, semidilute unentangled and entangled regimes were investigated. The exponents in the specific viscosity η_sp ～ overlap parameter c[η] power law were 1, 2 and 4.7 for dilute, semidilute unentangled and entangled regimes, respectively, which were found to be consistent with the scaling prediction for neutral linear polymers in θ-solvent. For dilute solutions (lower than 0.9 wt.%), the linear viscoelastic responses were observed to be in good agreement with the Zimm model (Flory exponent ν = 0.5). While for semidilute unentangled solutions (between 0.9 and 8 wt.%), results obtained had been found to be consistent with Rouse model. Considering Flory exponent ν = 0.5 and the concentration dependences of the specific viscosity and relaxation time, it had been evaluated that poly(AN-co-IA) in [BMIM]Cl behaves as a neutral polymer in θ-solvent. It had also been suggested that according to the unusual deviation of Cox-Merz rule, poly(AN-co-IA)/[BMIM]Cl solutions are typical neutral polymeric liquids for the concentrated solutions but have shown a more complicated behavior at high deformation rates.     

高强超韧高密度聚乙烯/聚丙烯共混物性能与微相分离结构的研究

在常规注射过程中 ,难以获得超高性能的共混体系注射制件 ,已有的研究表明 ,采用高剪切注射 ,可以抬高共混体系的最低临界相容温度曲线 (LCST)的位置 ,增加相容性 .当熔体进入模具后 ,冷却的同时相容性下降 ,开始相分离 ,相分离程度发展到某一程度即可获得高性能的制件 .对于高密度聚乙烯 (HDPE)、聚丙烯 (PP)两组分均为结晶型聚合物的共混体系 ,由于其相形态与结晶形态相互制约、竞争 ,微相分离程度难以控制 ,因此对其液 液相形态与结晶过程的控制是获得共混物最终形态与性能的关键 .采用振动保压注射成型技术不仅对HDPE、PP各自力学性能有明显的自增强作用 ,而且对HDPE/PP共混体系的力学性能也有十分明显的改善 .DSC、WAXD、SEM结果表明共混体系拉伸强度的提高主要取决于试样中串晶数量和大分子链的定向程度 ,而冲击强度则主要取决于两组分微观的相分离程度 .研究结果表明 ,HDPE/PP含量为 92 / 8的试样拉伸强度为 97 1MPa,80 / 2 0试样的缺口冲击强度为 4 5 5kJ/m2 ,较静态试样分别提高 4 3倍和 9 5倍 .采用振动填充注射技术针对某一组分可以获得高强度、高韧性的共混制件 .