Modification of PP by blending with PS and reactive polymers

In this paper a polypropylene (PP) resin with controlled rheology was selected as polymer matrix and modified by melt mixing with polystyrene (PS) which has certain processing compatibility with PP. The effect of the addition of polyperoxide (PPX), peroxide modified PS particles (PS‐PPX), and maleic anhydride (MAH) to the PP/PS blend during melt mixing on the rheological behavior and morphology of the PP/PS blends has been carefully studied.     

A calorimetric study of normal high density and ultra-high molecular weight polyethylene blends

The melting and the crystallization of blends of ultra-high molecular weight polyethylene (UHMWPE) and polyethylene high density with normal molecular weight (NMWPE) are investigated by means of differential scanning calorimetry (DSC). Mixing the components at a temperature below the flow temperature of UHMWPE (215 °C) results in segregated melting and crystallization. The segregated melting and crystallization temperatures of both components do not depend on composition of the blend. The extreme enthalpy dependence on blend composition is explained in terms of mutual influence exhibited by the components with respect to each other. It is due to the inner stresses in nonflowing UHMWPE characterized with a lot of entangled tie molecules. Mixing the components above the flow temperature of UHMWPE results in only one peak of melting and crystallization respectively. Complete mixing and probably co-crystallization between the components takes place on mixing NMWPE with flowing UHMWPE.     

Morphology development and control in immiscible polymer blends

Most immiscible polymer blends are produced by melt compounding in extruders. The melting and mixing process can generate morphologies ranging from disperse drops to fibers to lamella to cocontinuous structures. Controlling these morphologies is critical to performance of the final blend. This paper reviews recent research, from our group which reveals how these morphologies develop during compounding and how they can be stabilized with reactions at the interface between the two polymers.     

Rheological characterization of interfacial crosslinking in blends of reactive copolymers

The interfacial crosslinking reaction in molten blends of two functionalized ethylene copolymers was followed by rheological measurements. The blends were directly prepared in the rheometer. Due to the low melting temperature of the blend components, it was possible to carry out separately the mixing by steady shearing at low temperature, and the interfacial reaction followed by small amplitude dynamic measurements at higher temperatures. The influence of several parameters on the interfacial reaction was studied: the reaction temperature, the amount of shear during mixing, the blend composition and the compatibility and reactivity of the blend components.     

A multiple approach in determination of interfacial tension of biodegradable melt-mixed PBAT/EVOH blends: Correlation of morphology,rheology and mechanical properties

The interfacial tension of biodegradable melt-mixed blends of poly(butylene adipate-co-terephthalate), PBAT, and poly(ethylene-co-vinyl alcohol), (EVOH), was measured by breaking thread (BT), imbedded fiber retraction (IFR), and rheological methods. The PBAT-rich blends were prepared under different melt mixing conditions in order to investigate the effect of mixing conditions and possibility of reactive mixing between the blend components on the blend morphology, rheology, mechanical properties and interfacial tension values. The conditions were varied based on a Taguchi design of experiment using four factors namely EVOH content (0–30 wt%), mixing time (2–15 min), rotor speed (50–90 rpm), and mixing temperature (185–200 °C), each varying at three levels. The average size of EVOH droplets in PBAT matrix was determined for each blend by a field emission-scanning electron microscopy technique. The values of interfacial tension of PBAT/EVOH were found to be 2.57 ± 0.22 and 2.73 ± 0.30 mN m⁻¹ by the BT and IFR methods, respectively. The Palierne, Gramespacher, and Bousmina models were fitted to the rheological data to verify the interfacial tension of the blends. The continuous relaxation spectrum of the blends was determined in order to obtain the relaxation time of the EVOH droplets in the PBAT matrix. The Taguchi analysis revealed that the most effective factor is the EVOH content, and other factors do not play a significant role in the ultimate properties of the blends. Finally, based on the obtained mechanical properties, the possibility of reactive mixing under the applied mixing conditions was ruled out by means of repeated differential scanning calorimetry (DSC) and rheological measurements.     

Kinetics of nonisothermal crystallization and melting of normal high density and ultra-high molecular weight polyethylene blends

The kinetics of nonisothermal crystallization and melting of blends of ultra-high molecular weight polyethylene (UHMWPE) and polyethylene high density with normal molecular weight (NMWPE) are investigated by means of differential scanning calorimetry (DSC). Mixing the components at a temperature below the flow temperature of UHMWPE (215 °C) results in increased crystallization/melting rates of the individual components in the blends above the corresponding additive values. The morphological observations of the blends, carried out by means of polarization microscopy, show that a strong boundary of both types of structures (UHMWPE non-flowing aggregates and NMWPE spherulite structures) does not exist. The NMWPE spherulites' dimensions decrease on increasing the UHMWPE concentration in the blends, but their number increases. The facilitation of the crystallization/melting of the components in the blends is explained in terms of mutual influence exhibited by the components with respect to each other. It is due to the inner stresses in nonflowing UHMWPE characterized with a lot of entangled tie molecules and to the partial co-crystallization of NMWPE molecules with the flowing part of UHMWPE. At mixing temperatures above 215 °C the melting/crystallization integral kinetic curves have only one linear part in contrast to these of the same blend (11 ratio of components), prepared at 190 °C. The rates of melting/crystallization remain almost constant with the increase of the mixing temperatures.     

Mechanical,thermal and rheological properties and morphology of poly (lactic acid)/poly (propylene carbonate) blends prepared by vane extruder

In this study, the poly (lactic acid) (PLA) and poly (propylene carbonate) (PPC) blends with different compositions were prepared by a novel vane extruder based on elongation rheology. The mechanical properties, morphologies, crystallization behavior, thermal stability, and rheological properties of the blends were investigated. Mechanical test showed that PLA could be toughened by PPC to some extent, and the impact strength of the PLA was maximized when PPC content was about 30%. Differential scanning calorimetry analysis revealed that PPC had little effect on the melting process, the crystallization behavior of PLA component in the blend was improved, and the cold crystallizability of PLA decreased with the increase of PPC content when the PPC content was less than 50%. Thermogravimetry analysis showed that the thermal stability of the blends was improved by compounding with PLA. Scanning electron microscope showed that the dispersion of PLA droplets in PPC matrix was better than that of PPC droplets in PLA matrix. Rheological test showed that the melt viscosity of the pure PLA and the blend with 10% PPC was insensitive to shear rate, and the blends melt appeared shear thinning phenomenon with the increase of PPC content. It also showed that the blends microstructure changed with the addition of PPC and the blends with PPC content in a certain range had similar stress relaxation mechanism. Copyright © 2016 John Wiley & Sons, Ltd.     

Rheology behavior of nematic side-chain polymers in blends with thermoplasts

Peculiarities of the rheological behavior of blends composed of thermoplasts and side-chain nematic polymers have been studied. The strong role of interface interactions associated with the polymer chemical structure on the effect of rheology is shown. The influence of the nematic ordering is shown to be effective in the mechanical characteristics of blend extrudates whereas the rheology effect does not depend on the liquid crystal ordering.     

PC/EAA共混体系在加工过程中的反应

采用差示扫描量热法(DSC)和核磁共振氢谱法(1H-NMR)研究了不同聚碳酸酯(PC)/乙烯-丙烯酸共聚物(EAA)共混体系在加工过程中的大分子反应,考察了有机金属催化剂二丁基锡DBTO)含量和反应时间对体系的影响.采用哈克(Haake)转矩流变仪的混合器作反应釜,索氏抽提器分离产物.结果表明,PC和EAA在加工中反应剧烈,在共混体系的界面原位形成接枝或交联的PC-EAA共聚物,随催化剂用量增大、反应时间延长易生成共交联的PC-EAA共聚物.但混合时间过长,体系的断链反应会加剧,生成产物不稳定.     

Fibre‐forming blends of polypropylene and polyethylene terephthalate

Bicomponent fibres represent of the new ways for the preparation of synthetic fibres with more variable properties. The polypropylene (PP)‐poly(ethylene terephthalate) (PET) fibre‐forming blend is very interesting because of the improvement of dyeability from bath and some mechanical properties of PP fibres. The new polymer additives containing ester groups which can be added as masterbatches during melting and extrusion processes have been developed in the last years. It has been found that rheological properties of the basic polymer (PP) and polymer additives have a significant role in the blend formation and in spinning. In this work, the influence of some non‐reactive low‐molecular compounds on the processing of fibre‐forming PP‐PET blends and on the properties of blend fibres are presented.     

Compatibility Study of Blends of Acrylic Rubber (ACM), Poly(ethyleneterephalate) (PET), and Liquid Crystalline Polymer (LCP)

The ternary blends of acrylate rubber (ACM), poly(ethyleneterephalate) (PET), and liquid crystalline polymer (LCP) were prepared by varying the amount of LCP, but fixing the ratio of ACM and PET using melt mixing procedure. The compatibility behavior of these blends was investigated with infrared spectroscopy (IR), differential scanning calorimetry (DSC), and dynamic mechanical analyzer (DMA). The IR results revealed the significant interaction between the blend components. Glass transition temperature (T_g) and melting temperature (T_m) of the blends were affected depending on the LCP weight percent in the ACM/PET, respectively. This further suggests the strong interfacial interactions between the blend components. In the presence of ACM, the nucleating effect of LCP was more pronounced for the PET. The thermogravimetric (TGA) study shows the improved thermal stability of the blends.     

Shear influences on polymer blends: experimental,theoretical approaches and technical implications

We examine the effects of shear on polymer blends consisting of partially miscible components, i.e. systems close to the phase boundary. The eminent phenomenon is the shift of the phase boundary, either extending the homogeneous area (flow‐induced mixing) or the opposite effect (flow‐induced demixing). The kinetics of the demixing process and concentration fluctuations are also influenced by flow fields, inducing anisotropy due to the flow direction. Experiments (scattering, rheology, in‐situ flow‐scattering, microscopy, DSC) are carried out with the academic model blend polystyrene/poly(vinyl methyl ether) and the industrial poly(styrene‐co‐maleic anhydride)/poly (methyl methacrylate) blend. The experimental results are rationalised in terms of a generalised Gibbs energy of mixing by including the energy which is stored in the sheared fluids.     

Morphology and molten-state rheology of polylactide and polyhydroxyalkanoate blends

Polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) blends were prepared at different compositions by melt mixing. First, the rheological properties of each individual component are briefly presented focusing on the most important aspects to be taken into account during blends preparation and investigation. The kinetics of PHBV viscosity decrease due to strong polymer degradation in the molten state was recorded. This helped making a choice of the blending parameters and of the way of performing the rheological frequency sweeps. DSC showed that components are immiscible in the whole range of compositions studied. Blends morphology was studied using high-resolution scanning electron microscope and optical microscopy in reflection mode. Nodular and co-continuous morphologies were observed depending on the composition, and minor phase size was roughly estimated. The rheology of PLA/PHBV blends was investigated in the dynamic mode and correlated with the morphology observed. The results showed an important role of the interfaces between PLA and PHBV and a peculiar behaviour of the viscosity of some mixtures at low frequencies. At medium and high frequencies mixture dynamic viscosity follows the mixing law.     

A study of morphological,thermal, rheological and barrier properties of Poly(3-hydroxybutyrate-Co-3-Hydroxyvalerate)/polylactide blends prepared by melt mixing

The paper aims to study blend properties of biodegradable polymers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) prepared by melt mixing. Blend compositions based on PHBV/PLA were investigated according to the following weight ratios, i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 wt%. The study showed through scanning electron microscopy (SEM) that blends of PHBV/PLA are not miscible. This is consistent with differential scanning calorimetry (DSC) data which indicate the presence of two distinct glass transition temperatures (T_g) and melting temperatures (T_m), attributed to the neat polymers, over all the range of blend compositions. Water and oxygen barrier properties of PHBV/PLA blends are significantly improved with increasing the PHBV content in the blend. Further, morphological analyzes indicated that increasing the PHBV content in the polymer blends results in increasing the PLA crystallinity due to the finely dispersed PHBV crystals acting as a filler and a nucleating agent for PLA. On the other hand, the addition of PLA to the blend results in a very impressive increase in the complex viscosity of PHBV. Moreover, the rheological data showed that, excluding the specific behavior of the neat polymers at low frequencies, i.e. less than 0.1 Hz, the complex viscosity of PHBV/PLA blends fits the mixing law well.     

TLCP/PEI共混体系的流变特性与结构关系的研究

研究了VectraA950/PEI共混体系多层次结构与共混体系动态流变特性的关系.在研究液晶高分子的动态流变特性时,引入Palierne模型对动态实验结果进行预测.结果表明,TLCP分散相在高频时偏离了球形,导致Palierne模型拟合的结果与TLCP/PEI共混体系的实验结果在高频时不吻合.这与VectraA950/PEI共混体系中多层次结构在动态流场中的流变响应有关:在频率偏高时,液晶高分子取向不能完全松弛,易于形成各向异性结构,在流场作用下,易产生大形变;由于液晶高分子液滴的回缩过程很慢,在频率偏高时,产生的大形变不易回复,所以保留了纤维结构.     

Development of novel elastomeric blends derived from chlorinated nitrile rubber and chlorinated ethylene propylene diene rubber

Chlorinated nitrile rubber (Cl-NBR) has been blended with chlorinated ethylene propylene diene rubber (Cl-EPDM) in different ratios by a conventional mill mixing method. The effect of the blend ratio on processing characteristics, mechanical properties (such as tensile and tear strength, elongation at break, hardness, abrasion resistance, heat build-up and resilience), structure, morphology, glass transition temperature (Tg), thermal stability, flame retardancy, oil resistance, AC conductivity, dielectric properties and transport behavior of petrol, diesel and kerosene were investigated. The shift in absorption bands of blends studied from FTIR spectra, single Tg from DSC analysis and decrease in amorphous nature from XRD showed the molecular miscibility in Cl-NBR/Cl-EPDM blends. SEM images showed the uniform mixing of both Cl-NBR and Cl-EPDM in a 50/50 blend ratio. The TGA curves indicated the better thermal stability of the polymer blend. The elongation at break, heat build-up, resilience and hardness of the polymer blend decreases with an increase in Cl-NBR content in the blend whereas the flame and oil resistance were increased with increase in Cl-NBR content. Among the polymer blends, the maximum torque, tensile strength, tear and abrasion resistance was obtained for the 50/50 blend ratio because of the effective interfacial interactions between the blend components. AC conductivity and dielectric properties of polymer blend increased with increase in the ratio of Cl-NBR in the blend. Different transport properties such as diffusion, permeation and sorption coefficient were measured with respect to nature of solvent and different blend ratios. Temperature dependence of diffusion was used to estimate the activation parameters and the mechanism of transport found to be anomalous.     

Molecular mixing of incompatible polymers through formation of and coalescence from their common crystalline cyclodextrin inclusion compounds

We describe the successful mixing of polymer pairs and triplets that are normally incompatible to form blends that possess molecular‐level homogeneity. This is achieved by the simultaneous formation of crystalline inclusion compounds (ICs) between host cyclodextrins (CDs) and two or more guest polymers, followed by coalescing the included guest polymers from their common CD–ICs to form blends. Several such CD–IC fabricated blends, including both polymer1/polymer2 binary and polymer1/ polymer2/polymer3 ternary blends, are described and examined by means of X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and solid‐state NMR to probe their levels of mixing. It is generally observed that homogeneous blends with a molecular‐level mixing of blend components is achieved, even when the blend components are normally immiscible by the usual solution and melt blending techniques. In addition, when block copolymers composed of inherently immiscible blocks are coalesced from their CD–ICs, significant suppression of their normal phase‐segregated morphologies generally occurs. Preliminary observations of the thermal and temporal stabilities of the CD–IC coalesced blends and block copolymers are reported, and CD–IC fabrication of polymer blends and reorganization of block copolymers are suggested as a potentially novel means to achieve a significant expansion of the range of useful polymer materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4207–4224, 2004     

Mechanical and Rheological Behavior of Unvulcanized and Dynamically Vulcanized i-PP/EPDM Blends

The mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. It is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.     

The outstanding ability of nanosilica to stabilize dispersions of Nylon 6 droplets in a polypropylene matrix

The effectiveness of hydrophobically modified nanosilica (NS) as interfacial modifying agent for immiscible polymer blends is evaluated. Blends of polypropylene (PP) with 20% of polyamide 6 (PA) and 5% hydrophobic NS were prepared by melt mixing. Compression molded sheets and extruded films were evaluated by scanning electron microscopy, transmission electron microscopy, tensile testing, and rheological measurements. Hydrophobic NS particles strongly reduce the polydispersity and droplet size of the dispersed phase, as a result of their preferential location at the interface. NS promotes outstanding stability of blend dispersion regardless of the processing or post‐processing technique employed. The viscoelastic terminal zone shows a plateau for PP/PA/NS, which corresponds to a suspension‐like behavior. Under large amplitude oscillatory shear, the increment in the non‐linearity parameter Q evidences the interactions between NS and blend components. Therefore, NS is an excellent morphological stabilizer that prevents coalescence, but cannot promote interfacial adhesion between immiscible PP and PA phases. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1567–1579     

Miscibility,Crystallization, and Rheological Behavior of Solution Casting Poly(3-hydroxybutyrate)/poly(ethylene succinate) Blends Probed by Differential Scanning Calorimetry,Rheology, and Optical Microscope Techniques

The miscibility and crystallization of solution casting biodegradable poly(3-hydroxybuty-rate)/poly(ethylene succinate) (PHB/PES) blends was investigated by differential scanning calorimetry, rheology, and optical microscopy. The blends showed two glass transition temperatures and a depression of melting temperature of PHB with compositions in phase diagram, which indicated that the blend was partially miscible. The morphology observation supported this result. It was found that the PHB and PES can crystallize simultaneously or upon stepwise depending on the crystallization temperatures and compositions. The spherulite growth rate of PHB increased with increasing of PES content. The influence of compositions on the spherulitic growth rate for the partially miscible polymer blends was discussed.