Gel permeation chromatography in the study of the molecular weight distribution of the copolymer vinyl chloride–vinyl acetate

A sample of the commercial copolymer vinyl chloride–vinyl acetate was fractionated by the GPC method in the preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, GPC in the analytical scale, chemical analysis, and IR spectroscopy. They were compared with those obtained by precipitation fractionation. The M?_w and [η] values from the light scattering and viscometry of fractions of the commercial copolymer were employed for the calculation of the Mark-Houwink equation valid in THF at 25°C for a copolymer with vinyl acetate content of 10–13%. Universal calibration of the [η]·M type was confirmed experimentally for the above polymer. Effects which could change the correct interpretation of the GPC data were discussed in detail. Correct interpretation of the GPC data showed an agreement between the GPC, light scattering, and viscometric data within 6–7%.     

Estimation on thermal conductivities of filled polymers

A new thermal conduction model is proposed for filled polymer with particles, and predicted values by the new model are compared with experimental data. The model is fundamentally based on a generalization of parallel and series conduction models of composite, and further modified in taking into account that a random dispersion system is isotropic in thermal conduction. The following equation is derived from the new model; log λ = V · C₂ · log λ₂ + (1 ? V) · log(C₁ · λ₁). Therefore, when thermal conductivities of polymer and particles (λ₁, λ₂) are known, thermal conductivity of the filled polymer (λ) can be estimated by the equation, with any volume content of particles (V). The new model was proved by experimental data for filled polyethylene, polystyrene and polyamide with graphite, copper, or Al₂O₃.     

Thermal conductivity of a polymer composite filled with mixtures of particles

A new thermal conduction model is proposed for a polymer system filled with a mixture of several types of particles. Predicted values by the new model are compared with experimental data. The model is derived by extending a model that was previously proposed for a two-phase system. The following equation is derived from the new model: log λ = V · (X₂ · C₂ · log λ₂ + X₃ · C₃ · log λ₃ + (1 ? V) log (C₁ · λ₁. When the thermal conductivities of polymer and particles (λ₁, λ₂, λ₃, …) and a mixing ratio of particles (X₂, X₃, …) are known, thermal conductivity of the filled polymer (λ) with several types of particles can be estimated from the equation, with any volume content of particles (V). Furthermore, from each polymer–filler composite (two-phase system) data, the thermal conductivity of a composite filled with different filler particles can be estimated.     

Toughening effect of poly(methyl methacrylate) on an immiscible poly(vinylidene fluoride)/polylactide blend

In this work, a mutually miscible third polymer, poly(methyl methacrylate) (PMMA), was incorporated into an immiscible poly(vinylidene fluoride)/polylactide (PVDF/PLA) blend (weight ratio 70:30). It was found that incorporation of PMMA in an appropriate amount (30–60 wt%) induced a marked improvement in fracture toughness. A five times enlargement of the elongation at break can be achieved by introducing 30 wt% PMMA. In order to understand the underlying toughening mechanism, SEM, dynamic mechanical analysis (DMA), XRD and DSC were applied to study the variations in morphology, the interaction between the three components and the crystallization behavior. SEM micrographs showed that the PMMA preferred to locate at the interface of PVDF and PLA, which was attributed to the mutual miscibility of PVDF with PMMA and PLA. Furthermore, a variety of thermal characteristics such as T_g and T_m induced by the entanglement of PVDF, PMMA and PLA at the interface were illustrated in DMA and DSC curves. Obviously, the interface consisting of the entanglement of PVDF, PLA and PMMA acted as a linkage to improve interfacial adhesion, which was regarded as the main toughening mechanism. This work provides a potential strategy to realize the interfacial enhancement of an immiscible blend via the incorporation of a mutually miscible third polymer. © 2016 Society of Chemical Industry     

Polymer blends of PBT and PP compatibilized by ethylene-co-glycidyl methacrylate copolymers

The ethylene-co-glycidyl methacrylate (EG) copolymer is an efficient reactive compatibilizer for polymer blends of poly(butylene terephthalate) (PBT) and polypropylene (PP). During melt processing, the epoxy functional group of the EG copolymer can react with the PBT carboxylic acid and/or hydroxyl terminal groups at the interface to form various EG-g-PBT copolymers. These in situ formed grafted copolymers tend to concentrate along the interface to reduce the interfacial tension at the melt and result in finer phase domains. Higher glycidyl methacrylate (GMA) content in the EG copolymer or a higher quantity of the EG compatibilizer in the blend results in a better compatibilized blend in terms of finer phase domains, higher viscosity, and better mechanical properties. The presence of only 50 ppm catalyst (ethyltriphenyl phosphonium bromide) in the EG compatibilized blend further improves the blend compatibility substantially. © 1996 John Wiley & Sons, Inc.     

Fusion bonding of supercooled poly(ethylene terephthalate) between Tg and Tm

Because of its slowly crystallizing nature, poly(ethylene terephthalate) (PET) can be supercooled into an amorphous glass by rapid quenching. Upon reheating between T_g and T_m, the amorphous PET are subjected to two competing processes: rubber softening and crystallization. Fusion bonding of two such crystallizable amorphous polymer sheets in this processing temperature window is thus a complex process, different from fusion of purely amorphous polymer above T_g or semicrystalline polymer above T_m. In this study, the interfacial morphological development during fusion bonding of supercooled PET in the temperature window between T_g and T_m was studied. A unique double‐zone interfacial morphology was observed at the bond. Transcrystals were found to nucleate at the interface and grow inward toward the bulk and appeared to induce nucleation in the bulk to form a second interfacial region. The size and morphology of the two zones were found to be significantly affected by the fusion bonding conditions, particularly the fusion temperature. The fusion bonding strength determined by the peeling test was found to be significantly affected by the state of crystallization and the morphological development at the bonding interface. Based on the interfacial morphology observed and the bonding strength measured, a fusion bonding mechanism of crystallizable amorphous polymer was proposed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Internal and interfacial structure analysis of graft-type fluorinated polymer electrolyte membranes by small-angle X-ray scattering in the high-q range

The hierarchical structures of poly(styrenesulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs) with different scale ranges including lamellar spacing, interfacial thickness, and intra-structure of conducting layers were evaluated by small-angle X-ray scattering in terms of background scattering (I _B(q)). First, I _B(q) was roughly estimated by modifying Ruland's method and then optimized to avoid overestimation using a “contribution factor,” which is defined as the contribution of I _B(q) to the observed scattering intensities over the entire q range. Then, I _B(q) was optimized again by using the model for the deviation from Porod's law also proposed by Ruland to select proper q-range for interfacial thickness evaluation. The lamellar spacing, which is observed in the low-q range, was not altered by background correction. In contrast, in the high-q range, the interfacial thickness and the internal structures can be estimated only after correction for the background scattering data. The interfacial thickness of the final membranes (ETFE-PEMs) is affected by both the graft-polymerization and sulfonation processes and because the change in membrane structures is observed during propagation steps at lower ion exchange capacity (IEC) range (IECs < 2.4 mmol/g), which should affect the mechanical strength of graft-type PEMs.     

Role of block copolymer on the coarsening of morphology in polymer blend: Effect of micelles

The reactive compatibilization of polystyrene/ethylene‐α‐octene copolymer (PS/POE) blend via Friedel–Crafts alkylation reaction was investigated by rheology and electron microscope. It was found that the graft copolymer formed from interfacial reaction reduced the domain size and decreased the coarsening rate of morphology. The reduction of the interfacial tension is very limited according to the mean field theory even assuming that all block copolymer stays on the interface. With the help of self‐consistent field theory and rheological constitutive models, the distribution of graft copolymer was successfully estimated. It was found that large amount of copolymer had detached from the interfaces and formed micelles in the matrix. Both the block copolymer micelles in matrix and the block copolymers at the interface contribute to the suppression of coarsening in polymer blend, but play their roles at different stages of droplet coalescence. In droplet morphology, the micelles mainly hinder the approaching of droplets. © 2014 American Institute of Chemical Engineers AIChE J, 61: 285–295, 2015     

High temperature GPC of polypropylene

The highest temperature at which molecular weight distributions can be characterized by current techniques is 145°C. Supermolecular aggregates may exist at this temperature in polypropylene solutions in trichlorobenzene and other solvents. Dissolution procedures at higher temperatures are ineffective in this case because of the limited thermal stability of polypropylene. Aggregate-free solutions can be prepared, however, by controlling storage times at 145°C in mixtures with added stabilizers. Low angle laser light scattering measurements can be used to determine when true solutions have been produced. This occurs when measured second virial coefficients agree with values predicted for the M _w measured in the light scattering experiment. GPC–LALLS measurements of M _w and M _z provide similar information about the effects of storage time on dissolution of aggregates and polymer degradation.     

Determination of the absolute molecular weight of a styrene–butyl acrylate emulsion copolymer by low-angle laser light scattering (LALLS) and GPC/LALLS

The application of low-angle laser light scattering (LALLS) and combined GPC/LALLS for the measurement of absolute molecular weight distribution of a styrene–butylacrylate (30/70) emulsion copolymer is discussed. From the static light scattering measurements in four different solvents, i.e., toluene, tetrahydrofuran (THF), methyl ethyl ketone (MEK), and dimethylformamide (DMF), the true weight average molecular weight (M _w) and heterogeneity parameters are determined. The apparent M _w obtained from the static measurement in THF was in good agreement with the M _w determined from the multiple solvent analysis, suggesting the validity of using THF as the mobile phase in the combined GPC/LALLS analysis.     

Study of the partial wetting morphology in polylactide/poly[(butylene adipate)‐co‐terephthalate]/polyamide ternary blends: case of composite droplets

The prediction of the morphology of ternary polymer blends requires a good knowledge of the values of the three interfacial tensions. We selected three polymers, either biobased or biodegradable, polyamide (PA), poly[(butylene adipate)‐co‐terephthalate] (PBAT) and polylactide (PLA), and we accurately measured their interfacial tensions using the retraction method, varying the molar mass or inverting the phases. The following values of interfacial tension were obtained: γ_PBAT/PLA = 3.3 ± 0.7 mN m^?1, γ_PA/PLA = 5.6 ± 0.3 mN m^?1 and γ_PBAT/PA = 3.0 ± 0.4 mN m^?1. These values were used to calculate the spreading coefficients giving rise to two negative coefficients and one coefficient close to zero. Ternary blends with various compositions, two different levels of viscosity for PBAT and different processing conditions were prepared. There was a very good agreement between the predictions of the spreading theory, when using the values of interfacial tension of the right order of magnitude, and the observed morphologies, whatever the polymer serving as a matrix. When PLA or PBAT was chosen as the matrix, the ternary blend morphology was composed of composite droplets, presenting a partial wetting morphology, dispersed in the polymer matrix. This morphology was observed whatever the composition, the viscosity of the PBAT phase and the processing conditions. A further calculation of the free energy confirmed this morphology. The formation process of this semi‐encapsulated morphology was observed during blending. © 2018 Society of Chemical Industry     

Linear viscoelastic behavior of compatibilized PMMA/PP blends

In this work, the morphology and linear viscoelastic behavior of PMMA/PP blends to which a graft copolymer PP‐g‐PMMA has been added was studied. The copolymer concentration varied from 1 to 10 wt % relative to the dispersed phase concentration. The rheological data were used to infer the interfacial tension between the blended components. It was observed that PP‐g‐PMMA was effective as a compatibilizer for PMMA/PP blends. For PP‐g‐PMMA concentration added below the critical concentration of interface saturation, two rheological behaviors were observed depending on the blend concentration: for 70/30 blend, the storage modulus, at low frequencies, increased as compared to the one of the unmodified blend; for 90/10 blend, it decreased. For 90/10 blend, the relaxation spectrum presented an interfacial relaxation time related to the presence of the compatibilizer (τ_β). For PP‐g‐PMMA concentrations added above the critical concentration of interface saturation, the storage modulus of all blends increased as compared with the one of the unmodified blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polymer blends of poly(trimethylene terephthalate) and polystyrene compatibilized by styrene‐glycidyl methacrylate copolymers

The compatibilizing effects of styrene‐glycidyl methacrylate (SG) copolymers with various glycidyl methyacrylate (GMA) contents on immiscible blends of poly(trimethylene terephthalate) (PTT) and polystyrene (PS) were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ¹³C‐solid‐state nuclear magnetic resonance (NMR) spectroscopy. The epoxy functional groups in the SG copolymer were able to react with the PTT end groups (? COOH or ? OH) to form SG‐g‐PTT copolymers during melt processing. These in situ–formed graft copolymers tended to reside along the interface to reduce the interfacial tension and to increase the interfacial adhesion. The compatibilized PTT/PS blend possessed a smaller phase domain, higher viscosity, and better tensile properties than did the corresponding uncompatibilized blend. For all compositions, about 5% GMA in SG copolymer was found to be the optimum content to produce the best compatibilization of the blend. This study demonstrated that SG copolymers can be used efficiently in compatibilizing polymer blends of PTT and PS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2247–2252, 2003     

Potential role of nanofillers as compatibilizers in immiscible PLA/LDPE Blends

This article describes the use of commercial silica (SiO₂) and calcium carbonate (CaCO₃) nanofillers as compatibilizers in immiscible polylactide/low‐density polyethylene (PLA/LDPE) blends. The general aim of the study was to investigate the possibilities of replacing standard commodity plastics such as LDPE based on non‐renewable mineral oil resources with the biodegradable renewable polymer PLA in compatibilized PLA/LDPE blends for use in the packaging industry. The calculations of the minimal interfacial energy and optimal wetting abilities indicated that SiO₂ filler was a better potential compatibilizer than CaCO₃ for a given PLA/LDPE blend. This was due to its preferential localization at the interface. The significantly improved morphology of the ternary PLA/LDPE/SiO₂ blend was found to present an increased strength, toughness, and crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41414.     

Effects of Thermal and UV-induced Grafting of Bismaleimide on Mechanical Performance of Reclaimed Rubber/Natural Rubber Blends

The scrap rubber powder (SRP) could be compression moulded to form elastomer via in situ interfacial reactions. In this study, SRP/NR (85/15) blends with good performance could be prepared by incorporating a little amount (lower than 5 phr of SRP and NR) of m-phenyl bismaleimide (BMI) in the compositions. The mechanical properties and the interface of SRP/NR (85/15, w/w) blends (base blend) were investigated. The results showed that the processing temperature, time, and BMI content have significant effects on the mechanical properties of the blends. The optimum BMI content and processing condition were determined as 5 wt.% and 180 ^○C/10 min. The mechanical properties, especially the elongation at break, of the elastomers could be improved further by ultraviolet (UV) exposure. With UV exposure, the tensile strength, elongation at break and tear strength of the modified base blend were determined as 10.4 MPa, 260% and 24 KN/m respectively. The FTIR results indicated that the BMI could be grafted onto the SRP surface under UV exposure. The composition with UV exposure had more uniform dispersion of the BMI and improved interfacial adhesion. The glass transition temperature (T_g) of the blends was increased by increasing the processing temperature, processing time or the introduction of UV exposure.     

Geometry and nature of the interfacial layer in polyimide coatings

A new approach to the quantitative evaluation of the thickness h_i and the volume fraction V_i of the interfacial layer in polyimide coatings has been developed using the model of a one-sided polymer coating as a three-phase system (a substrate, an interfacial layer and a polymer matrix) and the method of differential scanning calorimetry. The new approach is characterized by the fact that a “pure” polymer matrix is modeled with the help of free films obtained on mercury. The formulas for the calculation of the thickness and volume fraction of the interfacial layer have been proposed. The value h_i has been determined in polymer coatings of different thicknesses on aluminium foil. This parameter has been shown to be independent of the film thickness if the latter is not larger than the length of the interfacial layer. An assumption has been made about the “mechanical” origin of thick (> 1–5 μm) interfacial layers, and their relaxation character has been revealed.     

Enhanced dielectric response of ternary polymeric composite films via interfacial bonding between V2C MXene and wide-bandgap ZnS

Increasing the dielectric constant of polymer/sulfide ceramic composites by using wide-bandgap semiconducting sulfide ceramic fillers like ZnS is difficult because of their low interface polarization. To increase the dielectric constant, in this study, ternary polymer-based composite films were designed and fabricated using a hybrid filler consisting of shell-like ZnS particles and core-like V₂C MXene particles. First, V₂C MXene with a multi-layered structure was synthesized from the simplest raw materials followed by the in-situ hydrothermal growth of ZnS particles around the V₂C particles. Then, binary polymer/ZnS and ternary polymer/V₂C–ZnS composites were fabricated, and their dielectric, conductive, and electrical breakdown properties were investigated. Finally, the effect of interfacial bonding between the V₂C and ZnS phases was investigated by density functional theory calculations, and the contribution of V₂C/ZnS interfacial bonding to the higher dielectric constant of the ternary composites than that of the binary composites was explained. The ternary composites exhibited balanced electrical properties suitable for energy storage applications. The ternary composite with 10 wt% hybrid filler loading exhibited a high dielectric constant of ~52, a low dielectric loss of ~0.11 at 100 Hz, and a high electrical breakdown strength of ~202 MV m⁻¹. This study paves the way for the facile fabrication of high-performance composite dielectrics for application in advanced capacitors.     

Measurement of molecular weight of poly(vinyl chloride)

Molecular weights of six bulk-process and five suspension-process PVC samples have been measured as part of a study aimed at developing a technique for gel permeation-chromatographic analysis of this polymer in tetrahydrofuran at room temperature. Osmometric M?_n values measured in cyclohexanone appear to be valid; the results are insensitive to thermal history or ultrasonic irradiation of the solution. Corresponding measurements in tetrahydrofuran changed with measurement temperature and indicated the presence of stable supermolecular PVC aggregates in this solvent. Such aggregates can be dispersed by ultrasonic treatment of the solution for brief periods. Simultaneous degradation of PVC molecules appears to be prevented by addition of small concentrations of nonionic surfactant to the tetrahydrofuran solutions. Treated solutions are suitable for GPC analyses at ambient temperatures. The results of osmometry, light scattering, and GPC agreed well.     

超临界CO2辅助聚合物加工

近年来,以超临界CO₂替代聚合物加工过程中大量使用的有机溶剂实现超临界CO₂辅助聚合物加工过程已引起人们越来越多的关注。CO₂在聚合物中的溶解扩散可导致其结构和形态的变化,能够溶胀增塑聚合物并且将溶解于其中的小分子物质携带输运到聚合物基体中,进而影响聚合物的结晶及晶型转变行为,聚合物/CO₂体系界面张力以及聚合物/CO₂体系流变行为等基本物性的变化。利用聚合物基本物性的变化可实现CO₂辅助聚合物接枝反应,CO₂辅助聚合物渗透小分子物质以及CO₂辅助聚合物发泡等超临界CO₂辅助聚合物加工过程的应用。结合本研究室的实例,探讨了CO₂作用下等规聚丙烯和间规聚丙烯的结晶行为以及一种多晶型聚合物--等规聚丁烯-1的晶型转变行为;探讨了利用CO₂对等规聚丙烯、聚乳酸和聚酯三种典型的低熔体强度结晶聚合物具有的不同诱导结晶作用,调控聚合物的结晶行为,使其具备发泡所需的熔体强度,制备了具有不同结构特征的发泡聚合物材料。     

Phase morphology and interfacial characteristics of polycarbonate/acrylonitrile‐ethylene‐propylene‐diene‐styrene blends compatibilized by styrene‐maleic anhydride copolymers

Blends of polycarbonate (PC) and acrylonitrile ‐ ethylene‐propylene‐diene‐styrene (AES) were reactive compatibilized by styrene‐maleic anhydride copolymers (SMA). The changes in phase morphology and interfacial characteristics of the blends as a function of maleic anhydride content of SMA and the concentration of compatibilizer have been systematic studied. The occurrence of reaction between the terminal hydroxyl groups of PC and the maleic anhydride (MA) of compatibilizer was confirmed by fourier transform infrared (FTIR) spectroscopy. A glass transition temperature (T_g) with an intermediate value between T_g(AES) and T_g(PC) was found on differential scanning calorimeter (DSC) curves of PC/AES blends compatibilized with SMA contains high levels of MA. Furthermore, at lower compatibilizer content, increase of the compatibilizer level in blends result in decreasing gap between two T_gs corresponding to the constituent polymers. Small angle X‐ray scattering (SAXS) test results indicated that compatibilizer concentration for the minimum of blend interface layer's thickness was exactly the same as it was when compatibilized PC/AES blend exhibited optimal compatibility in DSC test. The observed morphological changes were consistent well with the DSC and SAXS test results. A new mechanism of interfacial structural development was proposed to explain unusual phenomena of SMA compatibilized PC/AES blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42103.