Melt blending of linear low-density polyethylene and polystyrene in a Haake internal mixer. II. Morphology-processing relationships

A measure of the effective shear rate range for dispersive mixing in the Haake mixer has been developed, which is more representative of shearing conditions than that currently used. In addition, the effects of processing conditions, composition, and compatibilizer on linear low-density polyethylene and polystyrene (LLDPE/PS) blend morphology were studied. Fiber/stratified morphologies form with blends when the minor phase has low viscosity and is present at its higher concentration. The influence of the viscosity ratio on phase size was found to be a minor effect for mixtures having a low fraction of the dispersed phase (20% PS). The effect of shear intensity, however, was found to be more important at a low composition of the dispersed phase or in compatibilized blends. During Haake blending, an optimal time for adding compatibilizer to stabilize phase morphology was found to be when the final morphology of an incompatible blend had developed. Further studies have concluded that the addition of styrene–ethylene/butylene–styrene (SEBS) stabilized the blend morphology of LLDPE/PS more efficiently than styrene–ethylene/propylene (SEP) on different blending conditions and compositions. At high temperatures, the addition of SEP to a LLDPE/PS blend did not modify the dispersed phase size. On the other hand, SEBS stabilized the dispersion so that the final domain size is independent of composition. © 1995 John Wiley & Sons, Inc.     

The influence of viscosity and composition of ABS on the ABS/SBS blend morphology and properties

Acrylonitrile–butadiene–styrene (ABS) shows excellent impact resistance and good stiffness. The incorporation of thermoplastic elastomer into ABS may consist in an interesting approach to further improve the toughness of ABS, in addition to tuning its compatibility with reinforcements. Blends of ABS and styrene–butadiene–styrene (SBS) were obtained by extrusion from different types of ABS with different SBS contents. The results showed that morphology and mechanical behavior of ABS/SBS blends depend strongly on the composition and characteristics of ABS matrix. An increase in elongation at break and slight decrease in modulus could be observed by increasing SBS content. ABS/SBS blend possessing good dispersion of rubber particles with sizes ranging from 0.1 to 0.8 μm of rubber particles exhibited the better performance of the impact resistance, whereas blends showing a predominance of relatively large particles resulted on poorer mechanical properties. These results suggest that viscosity and composition of ABS matrix play a significant role on the dispersion and coalescence of the dispersed phase during mixing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47075.     

High density polyethylene/acrylonitrile butadiene rubber blends: Morphology,mechanical properties,and compatibilization

Polymer blends based on high-density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two-phase structure in which NBR phase was dispersed as domains up to 50% of its concentration in the continuous HDPE matrix. However, 70 : 30 NBR/HDPE showed a cocontinuous morphology. The tensile strength, elongation at break, and hardness of the system were measured as a function of blend compostion. As the polymer pair is incompatible, technological compatibilization was sought by the addition of maleic-modified polyethylene (MAPE) and phenolic-modified polyethylene (PhPE). The interfacial activity of MAPE and PhPE was studied as a function of compatibilizer concentration by following the morphology of the blend using scanning electron micrographs. Domain size of the dispersed phase showed a sharp decrease by the addition of small amounts of compatibilizers followed by a leveling off at higher concentrations. Also, more uniformity in the distribution of the dispersed phase was observed in compatibilized systems. The tensile strength of the compatibilized systems showed improvement. The mechanical property improvement, and finer and uniform morphology, of compatibilized systems were correlated with the improved interfacial condition of the compatibilized blends. The experimental results were compared with the current theories of Noolandi and Hong. © 1995 John Wiley & Sons, Inc.     

Transition of phase continuity induced by crosslinking and interfacial reaction during reactive processing of compatibilized PVC/SBR blends

Blends of 50 wt% of poly(vinyl chloride) (PVC) and 40 wt% of styrene butadiene rubber (SBR) with 10 wt% of acrylonitrile butadiene rubber (NBR) as the compatibilizer were prepared in a Haake mixer. An inversion of phase continuity was observed when the sulfur concentration was changed from 0.0 to 2.0 parts per hundred parts of resins (phr) in the blends containing an NBR with an acrylonitrile content of 29.5 wt% (NBR-29). The SBR phase, which is continuous in the unvulcanized blend, changes progressively into the dispersed phase as sulfur concentration increases. This is explained by the viscosity increase of the rubber caused by crosslinking. There is no phase inversion as a result of increasing sulfur concentration when the compatibilizer NBR-29 was replaced by an NBR with an acrylonitrile content of 40 wt% (NBR-40). The SBR phase is discrete in the unvulcanized blend with NBR-40 as the compatibilizer.

A change in phase continuity occurs during processing of the vulcanized PVC/NBR-29/SBR (50/10/40) blends. A torque peak in the torque curve during processing is correlated to the transition of the PVC phase continuity. There is a gradual increase in the torque curve after the torque peak. The rubber particle size decreases as a result of such a post-peak increase in the torque. The torque peak and the post-peak increase in the torque are absent in the case of the binary blends (PVC/NBR and PVC/SBR). The post-peak increase in the torque is attributed to the interfacial reaction between SBR and NBR that resides in the PVC phase.

A novel method developed recently was applied to study the interface development during processing. An interface with a higher rubber concentration develops during processing of the compatibilized blends.     

Influence of coalescence and interfacial tension on the morphology of PP/HDPE compatibilized blends

In this paper, the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene-propylene-diene copolymer (EPDM), ethylene-vinylacetate copolymer (EVA) and styrene-ethylene/butylene-styrene triblock copolymer (SEBS). The morphology of the blends was studied by scanning electron microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA or SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at compatibilizer saturation.     

Poly(ethylene‐graft‐ethylene oxide) (PE‐PEO) and poly(ethylene‐co‐acrylic acid) (PEAA) as compatibilizers in blends of LDPE and polyamide‐6

In a blend of two immiscible polymers a controlled morphology can be obtained by adding a block or graft copolymer as compatibilizer. In the present work blends of low‐density polyethylene (PE) and polyamide‐6 (PA‐6) were prepared by melt mixing the polymers in a co‐rotating, intermeshing twin‐screw extruder. Poly(ethylene‐graft‐polyethylene oxide) (PE‐PEO), synthesized from poly(ethylene‐co‐acrylic acid) (PEAA) (backbone) and poly(ethylene oxide) monomethyl ether (MPEO) (grafts), was added as compatibilizer. As a comparison, the unmodified backbone polymer, PEAA, was used. The morphology of the blends was studied by scanning electron microscopy (SEM). Melting and crystallization behavior of the blends was investigated by differential scanning calorimetry (DSC) and mechanical properties by tensile testing. The compatibilizing mechanisms were different for the two copolymers, and generated two different blend morphologies. Addition of PE‐PEO gave a material with small, well‐dispersed PA‐spheres having good adhesion to the PE matrix, whereas PEAA generated a morphology characterized by small PA‐spheres agglomerated to larger structures. Both compatibilized PE/PA blends had much improved mechanical properties compared with the uncompatibilized blend, with elongation at break (ε_b) increasing up to 200%. Addition of compatibilizer to the PE/PA blends stabilized the morphology towards coalescence and significantly reduced the size of the dispersed phase domains, from an average diameter of 20 μm in the unmodified PE/PA blend to approximately 1 μm in the compatibilized blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2416–2424, 2000     

Weld‐line characteristics of polycarbonate/acrylonitrile–butadiene–styrene blends. I. Effect of the processing temperature

The effects of the processing temperature on the morphology and mechanical properties at the weld line of 60/40 (w/w) polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) copolymer blends were investigated. The influences of the incorporation of poly(methyl methacrylate) (PMMA) as a compatibilizer and an increase in the viscosity of the dispersed ABS domain phase were also studied. The ABS domain was well dispersed in the region below the V notch, and a coarse morphology in the core region was observed. When tensile stress was applied perpendicularly to the weld line, the fracture propagated along the weak region behind the weld part; there, the domain phase coalescence was significant because of the poor compatibility between PC and styrene–acrylonitrile (SAN). Phase coalescence became severe, and so the mechanical strength of the welded specimen decreased with an increasing injection‐molding temperature. The domain morphology became stable and the mechanical strength increased as the viscosity of the domain phase increased or some SAN was replaced with PMMA. That the morphology was well distributed behind the weld line and the mechanical properties of PC/ABS/PMMA blends were improved was attributed to the compatibilizing effect of PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 689–699, 2005     

Correlation between the morphology and dynamic mechanical properties of ethylene vinyl acetate/linear low‐density polyethylene blends: Effects of the blend ratio and compatibilization

The effects of the blend composition and compatibilization on the morphology of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were studied. The blends showed dispersed/matrix and cocontinuous phase morphologies that depended on the composition. The blends had a cocontinuous morphology at an EVA concentration of 40–60%. The addition of the compatibilizer first decreased the domain size of the dispersed phase, which then leveled off. Two types of compatibilizers were added to the polymer/polymer interface: linear low‐density polyethylene‐g‐maleic anhydride and LLDPE‐g phenolic resin. Noolandi's theory was in agreement with the experimental data. The conformation of the compatibilizer at the blend interface could be predicted by the calculation of the area occupied by the compatibilizer molecule at the interface. The effects of the blend ratio and compatibilization on the dynamic mechanical properties of the blends were analyzed from ?60°C to +35°C. The experiments were performed over a series of frequencies. The area under the curve of the loss modulus versus the temperature was higher than the values obtained by group contribution analysis. The loss tangent curve showed a peak corresponding to the glass transition of EVA, indicating the incompatibility of the blend system. The damping characteristics of the blends increased with increasing EVA content because of the decrease in the crystalline volume of the system. Attempts were made to correlate the observed viscoelastic properties of the blends with the morphology. Various composite models were used to model the dynamic mechanical data. Compatibilization increased the storage modulus of the system because of the fine dispersion of EVA domains in the LLDPE matrix, which provided increased interfacial interaction. Better compatibilization was effected at a 0.5–1% loading of the compatibilizer. This was in full agreement with the dynamic mechanical spectroscopy data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4526–4538, 2006     

Influence of Phase Dispersant on the Cocross-Linking of Polyvinyl Chloride with Low Density Polyethylene

The cocross-linking of polyvinyl chloride (PVC) and low density polyethylene (LDPE) was studied by THF extraction, FTIR, and Dynamic rheological analysis. It is found that dicumyl peroxide (DCP) could neither induce the cross-linking of PVC itself nor cause PVC chains to cocross-link with LDPE. Butadiene rubber (BR), as a solid phase dispersant (SPD) can not give a hand to the cocross-linking. However, NBR, both as a compatibilizer and SPD, can induce PVC to be crosslinked or cocross-linked with LDPE initiated by DCP. The composite cross-linking agent that consists of DCP, triallyl isocyanurate (TAIC), and magnesium oxide (MgO) is easy to induce PVC to cross-link itself or cocross-link with LDPE.     

Phase dispersion–crosslinking synergism in binary blends of poly(vinyl chloride) with low‐density polyethylene: Entrapping phenomenon in PVC/LDPE/DCP blend

The co‐crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/low density polyethylene/dicumyl peroxide (PVC/LDPE/DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co‐crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid‐phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/LDPE blends. Meanwhile, the improvement of the tensile properties is dependent mainly on the properties of the LDPE networks. Finally, the mechanism of phase dispersion–crosslinking synergism is presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1296–1303, 2003     

Correlation of viscosity ratio,morphology, and mechanical properties of polyamide 12/natural rubber blends via reactive compatibilization

Natural rubber (NR)-modified polyamide 12 (Nylon12/NR) was produced by melt blending Nylon12 and NR in the presence of polystyrene/maleated natural rubber (PS/MNR) copolymer as a reactive compatibilizer. The influence of compatibilizer loading on viscosity ratio, morphology, and mechanical properties of the blends was investigated. As a consequence of the reactive blend between Nylon12 and maleated NR in PS/MNR, the formation of amide and succinimide linkages was set at rubber-Nylon12 interfaces. Thus the dispersion of rubber particles was improved, and the particle coalescence was prevented so that the fine morphology with good interfacial adhesion was stabilized. This also resulted to enhance the blend viscosity and to lower viscosity ratio. The data revealed strong correlation between low viscosity ratio and fine spherical morphology of the compatibilized blends. An optimum PS/MNR compatibilizer content was at 7 phr to produce good dispersion of small rubber domains (size ≤0.3 μm) in Nylon12 matrix. Thermal properties by DSC revealed that crystallization temperature of Nylon12 was lowered by the presence of NR and crystallinity of Nylon12 was slightly affected by the PS/MNR content. An enhancement of mechanical properties, especially the impact energy was observed without suffering the tensile and flexural properties. Compared to the neat Nylon12, the compatibilized blends showed an increase in impact energy by a factor of 5. This large enhancement is successfully interpreted in term of the toughening effect by rubber phase of suitable dispersed size and the interparticle distance.     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

Properties and preparation of compatibilized nylon 6 nanocomposites/ABS blends using functionalized metallocene polyolefin elastomer. I. Impact properties

The impact behaviors of nanoclay‐filled nylon 6 (nano‐nylon 6) blended with poly(acrylonitrile–butadiene–styrene) terpolymers (ABS) prepared through a twin screw mixing process were investigated here using metallocene polyethylene grafted maleic anhydride (POE‐g‐MA) as a compatibilizer to enhance the interface interaction. No clear effect of compatibilizer on the dispersion of clay and crystalline structure of nano‐nylon 6 has been observed. In view of morphology and rheological behaviors, the effect of compatibilizer on the mechanical properties could be elucidated. It is found that impact strength increases with the addition of compatibilizer at various ABS compositions. Similar effects are also observed with decreasing test temperature at the nano‐nylon 6/ABS blend composition of 80/20. As for thermal properties, the heat distortion temperature shows a marginal decrease in the nano‐nylon 6/ABS blends. Rheological behavior indicates that increased viscosity is found for the investigated compatibilized systems. Through morphology observations, the etched ABS particle sizes tend to decrease with the addition of compatibilizer for the blends, but are larger with higher contents of ABS concentrations. Those observations account for impact behaviors of the investigated blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1364–1371, 2006     

Effect of a styrene–butadiene copolymer on the phase structure and impact strength of polyethylene/high‐impact polystyrene blends

The effect of a styrene–butadiene block copolymer on the phase structure and impact strength of high‐density and low‐density polyethylene/high‐impact polystyrene blends with various compositions was studied. For both the blends, the type of the phase structure was not affected by addition of a styrene–butadiene compatibilizer. The localization and structure of the compatibilizer in the blends were dependent on their composition. Addition of the compatibilizer improved impact strength of the blends in the whole concentration range. The improvement was the largest for blends with a low amount of the minor phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 570–580, 2001     

Effect of compatibilizer on the crystallization,rheological, and tensile properties of LDPE/EVOH blends

The effect of the compatibilizer on the crystallization, rheological, and tensile properties of low-density polyethylene (LDPE)/ethylene vinyl alcohol (EVOH) (70/30) blends was investigated. Maleic anhydride-grafted linear low-density polyethylene (LLD-g-MAH) was used as the compatibilizer in various concentrations (from 1 to 12 phr). The interesting effect of compatibilization on the crystallization kinetics of the blends was noted, and the correlation between the morphology and the rheological and tensile properties was also discussed. Morphological analysis showed that the blends exhibited a regular and finer dispersion of the EVOH phase when LLD-g-MAH was added. Nonisothermal crystallization exotherms of the compatibilized LDPE/EVOH blends showed the retarded crystallization of the dispersed EVOH phase, which probably resulted from the constraint effect of the grafted EVOH (EVOH-g-LLD) as well as the size reduction of the EVOH domains. The blends exhibited increased melt viscosity and storage modulus and also enhanced tensile properties with the addition of LLD-g-MAH, which seemed to be attributable to both dispersed particle-size reduction and improved interfacial adhesion. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1245–1256, 1998     

Experimental study of the relationship of processing to the morphology in blends of SBR and cis-polybutadiene with carbon black

The morphology of carbon-black-loaded styrene–butadiene rubber (SBR)/cis-1,4-polybutadiene (BR) blends is characterized as a function of mixing energy input. The blends consist of an 80:20 weight ratio of SBR and BR with the incorporation of 20 phr carbon black via three different schemes. These schemes are: (1) free mixing of the three components, (2) mixing of BR–black masterbatch with SBR, and (3) mixing of SBR–black masterbatch with BR. Differential scanning calorimetry (DSC) and electron microscopy (EM) results indicate that the domain morphology is strongly affected by the manner in which the carbon black is introduced into these blends. Some of the features of the blends are as follows: (1) BR, which is the minor rubber component, is always the dispersed phase, and its domain size decreases with increasing energy input during mixing. (2) In the black–rubber masterbatch mixing, the black always stays in the original rubber phase throughout the mixing process. No significant migration of carbon black from one rubber phase to the other is observed. (3) In the free mixing process, the carbon black agglomerates initially line up along the SBR–BR interfaces, and later disperse throughout the SBR matrix with increased mixing. However, the DSC results suggest that the amount of carbon-black-free BR is decreasing with increased mixing. This would occur if there is created a carbon-black-loaded SBR–BR diffuse interphase. A model is developed to interpret these findings.     

Morphological stability of postconsumer PET/HDPE blends

Summary The morphological stability and the mechanical properties of postconsumer polyethylene terephthalate (PET) and high density polyethylene (HDPE), at different composition with and without compatibilizer were investigated. The blends were prepared in an internal mixer and in a twin screw-extruder at different stretching ratio. For uncompatibilized blends, (previously prepared by extrusion), the particle size of the dispersed phase increases after being reprocessed in an internal mixer. However, in the case of compatibilized blend the particle size remains constant. Consequently, the compatibilizer reduces interfacial mobility, coalescence effects and stabilizes the morphology. The mechanical properties are also modified by the presence of the compatibilizer, mainly the elongation at break. Received: 14 January 2000/Accepted: 16 August 2000     

嵌段共聚物增容剂对LDPE／PS分散相粒径的影响

研究了增容剂苯乙烯－丁二烯二嵌段共聚物，苯乙烯－乙烯／丙烯二嵌段共聚物和苯乙烯－乙烯／丁烯－苯乙烯三嵌段共聚物对ＬＤＰＥ／ＰＳ共混物分散相粒径尺寸的影响，结果表明，在增容剂用量约３％时，分散相的粒径尺寸接近最小值，进一步增加增容剂的用量，粒径尺寸没明显的变化；增容剂中苯乙烯嵌段和橡胶嵌段之间的溶度参数差越大，分子间排斥作用越大，分散相的粒径越小。     

Structure and properties of rubber-modified polypropylene impact blends

The state of dispersion of poly(ethylene-co-propylene) (PEP) rubber and high-density polyethylene (HDPE) in polypropylene (PP) blends was investigated using scanning electron microscopy to examine solvent-etched microtomed surfaces cut at low temperatures. The validity of the method was established by comparing the areal fraction of dispersed particles in micrographs with the volume fraction of PEP and HDPE in PP-rich blends. When small amounts of PEP and HDPE were added to PP, they combined to form composite PEP–HDPE particles with characteristic internal structures in a PP matrix. Changes in impact strength and flexural modulus with changes in mixing conditions and blend composition were determined and interpreted in terms of the size, composition, and internal structure of the dispersed particles. Particle growth in the melt limited the impact strength level achieved in molded articles. A simple model proposed for screening rubbers for toughening of brittle plastics successfully predicts that PEP rubber should be an excellent impact modifier for PP.