Dynamic and transient shear start‐up flow experiments along with TEM, WAXS, and SEM analyses are performed on PP/PET blends and nanocomposites. The TEM results along with a theoretical analysis based on a thermodynamic model reveal that the clay particles are mainly localized in the PET phase. The localization of nanoclay in PET as the matrix phase leads to a refinement of morphology. The localization of clay is also studied by analyzing changes in complex viscosity and storage modulus in oscillation mode as well as the changes in power law index obtained from steady‐state and transient shear start‐up flow experiments. The changes in the rheological behavior of the blends are attributed to formation of clay network‐like structures.
In situ PET microfibrils are created by drawing melt‐blended PP and PET. The drawn blend is used to prepare polymer/polymer MFCs, and isolated PET microfibrils are used for the manufacturing of MF‐SPCs. Samples are prepared with different fibril orientations to determine the effect of orientation on the mechanical properties of the two types of composites. The resulting composites show improvements in stiffness of 77% for uniaxial MFCs, and 125% for uniaxial MF‐SPCs, with the highest recorded modulus of 8.57 GPa for a uniaxial MF‐SPC sample. SEM observations confirm that the fibrillar structure and excellent alignment is maintained. The changes in the reinforcement effect with orientation are very similar to those predicted by the rule of mixtures for the crossply.
Poly(propylene)‐clay nanocomposites and poly(propylene) containing conventional inorganic fillers such as calcium carbonate (CaCO3) and glass fiber were used in a comparative study focusing on dimensional stability, structure, mechanical and thermal properties. Micro‐ and nanocomposites were prepared by melt blending in a twin‐screw extruder. The relative influence of each filler was observed from dimensional stability measurements and structural analysis by WAXD, TEM, and thermal and mechanical properties. At equal filler loadings, PP/clay nanocomposites exhibit an improvement in dimensional stability and were the only composites capable of reduced shrinkage in both in‐flow and cross‐flow directions. The flexural modulus of PP increased nearly 20% by compounding with 4% organoclay, as compared to a similar performance obtained by compounding with 10 wt.‐% of CaCO3 or approximately 6 wt.‐% of glass fiber. The HDT and thermal stability of PP were enhanced by using nanoclay as filler.
The effect of CO2‐induced crystallization on the mechanical properties, in particular the yield and the ultimate stresses, of polyolefins is studied. PP and SEBS copolymer blends are used as examples and foamed after sorption of CO2 at temperatures below Tm. CO2 sorption thickens the crystalline lamellae and consequently increases Tm from 160 to 178 °C for both pure PP and PP/SEBS blend systems. Foams with an average cell size smaller than 250 nm retain the ultimate stress at the level of the polymer before foaming, even without the effect of CO2‐induced crystallization. Including CO2‐induced crystallization, the yield and the ultimate stresses of the foam can be improved by 30 and 50% over solid PP and by 22 and 40%, for solid PP/SEBS blends, respectively.
Dynamic and start‐up shear flow experiments along with SEM analysis are described for a PP/PET blend compatibilized by two reactive compatibilizers with different interfacial activity and rheological characteristics. The linear viscoelastic behavior of the blends is discussed using Palierne and fractional Zener models (FZMs). The nonzero value of Ge, the elastic modulus of spring element of FZM, is explained by the network‐like structure of the blends attributed to the interconnectivity between dispersed‐phase domains. Ge increases with increasing interfacial activity. Micelle formation due to extra amounts of compatibilizer in a system with higher interfacial activity leads to an increase of the elastic modulus, but to Ge = 0 in system with lower interfacial activity.
As‐received poly(ethylene terephthalate) (asr‐PET) may be reorganized by precipitation from trifluoroacetic acid upon gradual addition to a large excess of rapidly stirred acetone (p‐PET). Unlike asr‐PET, p‐PET repeatedly crystallizes rapidly from the melt, and can be used in small quantities (a few %) as an effective self‐nucleating agent to control and improve the bulk semi‐crystalline morphology and properties of asr‐PET. Nuc‐PET film has significantly increased hardness and Young's modulus and is much less permeable to CO2, while its un‐drawn fibers exhibit higher tenacities and moduli. Because nuc‐PET contains no incompatible additives, it may be readily recycled.
Plastic foam with nano‐/micro‐scale cellular structures was prepared from a poly(propylene) (PP)/propylene‐ethylene copolymer (PER) blend by controlling bubble nucleation sites and bubble growth in disperse PER domains. Batch foaming experiments using a CO2 pressure quench method were conducted at room temperature. The bubble size and location were highly controlled in disperse PER domains by exploiting the differences in CO2 solubility and viscoelasticity between the PER domains and the PP matrix. The average cell diameter of PP/PER blend foams can be controlled within 0.5–2 µm by the PP/PER ratio, depressurization rate, and foaming temperature.
In this paper, a novel intumescent system including MP as well as PER/TPU which acts as composite charring agent, is adopted to flame‐retarded PP. The encapsulation of charring agent PER by TPU effectively avoids the reaction of PER with MP during the compounding with PP at high temperature and also prevents the leaching out of polar PER from nonpolar PP matrix, thus remarkably enhancing the stability and water‐resistance of the intumescent system. PER and TPU have different but complementary charring mechanisms. So flame‐retarded PP with MP/composite charring agent shows a much better charring performance and flame‐retardancy than MP/PER flame‐retarded PP. The experimental results show that the former can reach UL‐94 V‐0 rating at 1.6 mm thickness at 25 wt.‐% flame retardant loading.
The fabrication and characterization of a hybrid polymer p‐n junction‐type thin film via electropolymerization of NPs and a precursor polymer is described. Blends of TiO2 NPs, CdSe NCs, Cbz‐COOH, and PVK were utilized to enable electrochemical deposition on ITO glass substrates. Spectroscopic, microscopic, and wetting measurements confirmed thin film fabrication. CV yielded a CPN nanocomposite with electropolymerized (i.e., crosslinked) carbazole units embedding CdSe NCs. Absorption and emission measurements confirmed a charge transfer mechanism between the crosslinked carbazole and the NCs resulting in a p‐n junction‐type thin film on ITO; with the observed quenching of CdSe NC emission. Several possible applications of such thin films are also discussed.
Boehmite alumina nanoparticles are added to PP‐g‐MAH‐compatibilized blends of PA 12 and PP to study the effects of nanoparticle loading in the resulting composites. WAXD and SEM data suggest that the nanoparticles enhanced the coalescence of PP. DSC, DMA, and TGA reveal that the final properties such as crystallization temperature, flexural storage modulus, thermal degradation temperature, etc., improve with increasing nanoparticle loading for blend/based composites. FTIR results show that the nanoparticles interfere with the interfacial activity at 5 wt% nanoparticle loading. All results are compared between the neat polymers and the compatibilized blend and show that despite a slight increase in dispersed‐phase domain size, all other properties improve with the addition of AlO(OH).
A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.
Photoembossing is a cost‐effective technique for the production of complex surface relief structures in a photopolymer film, achieved via contact‐mask exposure to UV‐light. Here, photoembossing is explored using interference holography with a CW laser and a nanosecond pulsed laser. It is shown that identical surface relief structures are produced if the photopolymer film is kept in a fixed position. In the case of a moving substrate, relief structures are only obtained with the pulsed laser and the heights of the relief structures and their shape are the same as in the static experiments. This illustrates that photoembossing in combination with pulsed laser interference holography is potentially useful in the production of large area structured films using roll‐to‐roll processes.
The present paper is aimed to evaluate the efficiency of two masterbatches, i.e., EBAGMA/LDPE (MB1) and EBAGMA/PET (MB2) with 50/50 w/w composition, prepared by melt mixing and used as new compatibilizers for blends of LDPE/PET. The morphology, the mechanical and the thermal properties of LDPE/PET/MB1 and LDPE/PET/MB2 ternary blends have been investigated. Morphological investigation by SEM of LDPE/PET/MB1 ternary blends showed a finer dispersion of PET in LDPE matrix with a better interfacial adhesion compared to those of both LDPE/PET/MB2 and binary LDPE/PET blends. The results also indicated a substantial improvement in both elongation at break and impact strength, while the Young's modulus decreased. Moreover, the thermal properties showed a decrease of the crystallization phenomena of PET in LDPE/PET/MB1 blend, thus confirming the good dispersion of PET particles into the continuous phase of LDPE matrix, leading to the conclusion that MB1 could be an efficient compatibilizer for LDPE/PET system.
Hybrid nanocomposite coatings were prepared by the UV‐curing technique with a methacrylic oligomer and multifunctional methacrylic polyhedral oligomeric silsesquioxane blocks (POSS®). The results obtained from the polyhedral compounds were compared with those of a disordered framework obtained by the condensation of a silica precursor (MEMO). The inorganic domains generated during synthesis created constraints in movement of polymer segments, which reflected in an increase in Tg of the hybrid nanocomposite coatings. The films were transparent. The random structure obtained by the condensation of the MEMO showed a stronger effect on Tg than that observed by introducing POSS®. The effect of inorganic domains reflected on thermal stability, surface hardness and mechanical properties of the hybrid nano‐composite coatings.
Aminated poly(propylene) was prepared by reacting aliphatic primary diamines with maleic‐anhydride‐functionalized poly(propylene) by in situ melt reaction. Around 60–70% of the initial acid groups had reacted to form amide and imide groups as confirmed by the almost complete disappearance of the maleic anhydride peak in FT‐IR spectra. The molecular weight of the diamines had an influence on changes in molecular structure of the PP‐g‐NH2 as a result of secondary reactions such as chain extension and cross‐linking. PP‐g‐NH2 and polycarbonate were pressed into two‐layer films and their adhesion strength was measured. The results showed that PP‐g‐NH2 was a very effective adhesion promoter.
Epoxy/BaTiO3 hybrid materials are prepared as good candidates for organic capacitors. The hybrid system is cured by using camphorquinone and a iodonium salt through a free‐radical promoted cationic polymerization using a long‐wavelength tungsten halogen lamp. The cured films are fully characterized. Morphological characterization shows a well‐dispersed inorganic phase within the organic matrix. Electrical characterization demonstrates a linear increase of the dielectric constant with increasing filler content, while low dielectric loss values are obtained.
scCO2 was used to assist in the preparation of PP/CNT composites. Two types of CNTs were used: MWNTs with and without HDPE coating (cMWNTs). The morphology of the nanocomposites and their mechanical and thermal properties were investigated and compared with samples made by traditional melt compounding. The use of cMWNT leads to better dispersion and properties in melt‐compounded nanocomposites. For systems prepared using scCO2‐assisted mixing, however, better properties were obtained using pristine MWNTs, avoiding the additional costs of nanotube modification. It was also shown that observed improvements in the mechanical properties for these materials were due to a combination of matrix modification and nanotube reinforcement, rather than a reinforcement effect caused solely by MWNTs.
New talc/PBAT hybrid materials were prepared through reactive extrusion. First, PBAT was free‐radically grafted with MA to improve the interfacial adhesion between PBAT and talc. Then, the resulting MA‐g‐PBAT was reactively melt‐blended with talc through esterification reactions of MA moieties with the silanol functions from talc. Sn(Oct)2 and DMAP were used as catalysts. Interestingly, the tensile properties for these compatibilized composites were improved due to a better interfacial adhesion between both partners. XPS showed the formation of covalent ester bonds between the silanol functions from talc particles, and the MA moieties grafted onto the polyester backbones.
The first reported use of two‐dimensional mesh thermoplastic fibers in an epoxy matrix for mendable composites is presented, yielding 100% restoration of GIC, failure energy, and peak loads over repeated damage‐healing cycles. SEM imaging and EDS mapping showed different surface structures between CFRPp and CFRPf and confirmed strength recoveries were attained by delivery of EMAA to the fracture plane which enabled the fractured surfaces to rebind after heating to 150 °C for 30 min.
Toughness enhancement of S‐(S/B)‐S triblock copolymers via a molecular‐weight‐controlled pathway is demonstrated. The post‐yield crack toughness behavior of the triblock copolymers uniquely reveal a brittle‐to‐semiductile‐to‐ductile transition with increasing while keeping the basic molecular architecture fixed. TEM and SAXS investigations indicated three distinct morphologies as a function of χeffN as a consequence of the increase in : (i) a homogeneous structure without phase‐separation, (ii) a weakly segregated structure, and (iii) a lamellar structure. The increase in crack toughness is also reaffirmed from kinetic and strain field analysis studies concerning dynamics of crack growth in block copolymers with high PS content.
