LLDPE/LDPE blends. I. Rheological,thermal, and mechanical properties

Structure and mechanical properties were studied for the binary blends of a linear low density polyethylene (LLDPE) (ethylene‐1‐hexene copolymer; density = 900 kg m⁻³) with narrow short chain branching distribution and a low density polyethylene (LDPE) which is characterized by the long chain branches. It was found by the rheological measurements that the LLDPE and the LDPE are miscible in the molten state. The steady‐state rheological properties of the blends can be predicted using oscillatory shear moduli. Furthermore, the crystallization temperature of LDPE is higher than that of the LLDPE and is found to act as a nucleating agent for the crystallization of the LLDPE. Consequently, the melting temperature, degree of crystallinity, and hardness of the blend increase rapidly with increases in the LDPE content in the blend, even though the amount of the LDPE in the blend is small. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3153–3159, 1999     

Cathodic disbondment resistance with reactive ethylene terpolymer blends

Adhesion to metallic substrates can be improved through the addition of polar functional groups, which bond with surface groups on the metal substrate. Additionally, polar interactions have been shown to increase adhesive strength even in wet environments (such as in the case for cathodic protection). A polymer blend is proposed as a coating material to provide adequate protection against the diffusion of moisture and air to the metallic surface along with superior adhesion even in the presence of wet and corrosive environments to resist cathodic disbondment. A reactive ethylene terpolymer (RET) of ethylene/n-butyl acrylate/glycidyl methacrylate (E/nBA/GMA) was compounded with HDPE to develop a potential coating material. The HDPE component offers high chemical and moisture resistance to permeation, while the RET component provides the material with high polarity and reactivity, which enhances adhesion to the substrates to be coated. The introduction of the reactive ethylene terpolymer decreases the magnitude of cathodic disbondment area of polyethylene coatings. After applying a cathodic potential to the coating substrate, the adhesive strength was observed to remain the same for silane-pretreated steel dollies. Without silane pretreatment, post-CD adhesive loss resembles that of the open circuit “wet” condition. EDAX data in conjunction with oxygen and water vapor transmission rates suggest an initial stage of disbondment where interfacial oxide is dissolved resulting in the delamination of coating around the initial defect. This initial disbondment zone acts like a moving crack tip creating larger areas of disbondment where interfacial bonds are degraded by the ingress of moisture and ions along the interface.     

Melt rheological properties of reactive compatibilized HDPE/PET blends

Melt rheological properties of high density polyethylene and poly(ethylene terephthalate) (HDPE/PET) blends compatibilized by an ethylene–butyl acrylate–glycidyl methacrylate terpolymer (EBAGMA) were studied by means of a HAAKE torque rheometer and a capillary rheometer. The phase morphology of the blends was evaluated by a scanning electron microscope (SEM). The results showed that the melts of blends behave pseudoplasticity. The addition of EBAGMA strengthens the interfacial adhesion between HDPE and PET and improves the phase dispersion due to reactive compatibilization. It was observed that the balance torque, melt viscosity, and sensitivity of melt viscosity to shear rate of the melts increase with increasing content of EBAGMA, but the melt flow index and activation energy decrease. At the same time, the plasticizing time is shortened indicating that the processability of the compatibilized blends has been improved. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Co‐crystallization in ternary polyethylene blends: tie crystal formation and mechanical properties improvement

Understanding the co‐crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co‐crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler ? Natta linear low density polyethylene (ZN‐LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40 wt% and the LDPE/ZN‐LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X‐ray scattering, small angle X‐ray scattering and field emission SEM techniques revealed the formation of two distinct co‐crystals in the blends. Fine LDPE/ZN‐LLDPE co‐crystals, named tie crystals, dispersed within the amorphous gallery between the coarse HDPE/ZN‐LLDPE co‐crystals were characterized for the first time in this study. It is shown that the tie crystals strengthen the amorphous gallery and play a major role in the mechanical performance of the blend.© 2016 Society of Chemical Industry     

Rheological properties of UHMWPE/HDPE blend gels and morphology and mechanical properties of gel-spun fibers

To produce polyethylene (PE) fibers with relatively high tensile strength but low cost, ultra-high-molecular-weight polyethylene (UHMWPE)/high-density polyethylene (HDPE) (UH) blend gels were prepared from paraffin oil and further fabricated into UH blend fibers by gel spinning. This research focused on the rheological properties of UH blend gels with high solid contents (SCs) ranging from 25 to 100 g/L, as well as morphology and mechanical properties of resultant gel-spun UH blend fibers. The rheological measurements indicated that the apparent viscosity, shear storage, and loss moduli of the UH blend gels were not markedly increased compared with those of the UHMWPE gel with much less SC. No obvious solid–liquid phase separation occurred in UH blend gels at a temperature above the sol–gel transition temperature. UH blend fibers were prepared by drawing as-spun fibers (draw ratio [λ] = 3) at 110°C to λ = 15, 45, 60, and 80, respectively. The orientation degree of fibril structure in UH blend fibers increased with increasing λ but the length of fibrils (L_fibril) showed a complex change. The L_fibril of UH blend fibers became larger due to chain arrangement in company with the transformation of the kebab structure to the extended shish structure when the λ was less than 45 but decreased during further elongation (λ = 60 and 80) because of fibril breakage and recrystallization. The change in morphological behavior led to the corresponding change in mechanical properties of resultant gel-spun UH blend fibers. The tensile strength of gel-spun UH55-45 blend fiber (UHMWPE/HDPE = 5/5 and λ = 45) reached 15.6 cN/dtex, which could fulfill the requirement of mechanical properties in common application.     

APAM/淀粉共混薄膜力学性能及粘合强度的研究

以丙烯酰胺(AM)、丙烯酸(AA)和丙烯酰氧乙基三甲基氯化铵(DAC)为共聚合单体,通过水溶液聚合合成两性聚丙烯酰胺(APAM),然后探索了它与淀粉的共混比对纤维粘合强度的影响,研究了这种共混物的薄膜性能。研究结果表明,APAM与淀粉共混后能够明显改善对棉和涤纶纤维的粘合强度,随着APAM用量的增加,对棉和涤纶纤维粘合强度逐渐增大;通过与APAM的共混,能够降低淀粉膜的脆性,对淀粉膜具有增韧作用;并能缩短淀粉膜的水溶时间、增加吸湿率和水溶胀率,有利于纺织退浆。     

PA 6/EPDM-g-MAH/HDPE三元共混物的形态与力学性能

制备了聚酰胺(PA)6/马来酸酐(MAH)接枝三元乙丙橡胶(EPDM)(EPDM-g-MAH)/高密度聚乙烯(HDPE)三元共混物,采用扫描电子显微镜观察了三元共混物的相形态,研究了注塑过程的二次剪切流动对该三元共混物相形态的影响,以及三元共混物相形态对其力学性能的影响。结果表明:二次剪切流动有利于PA 6/EPDM-g-MAH/HDPE体系向热力学最稳定的壳核结构发生转变。与PA 6/EPDM-g-MAH二元共混物相比,该三元共混物的力学性能得到较大改善,w(EPDM-g-MAH)为15%时,其Izod缺口冲击强度达85.83 kJ/m2,是纯PA 6的9倍,是同等橡胶含量的PA 6/EPDM-g-MAH二元共混物的2倍。     

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007     

Thermal and mechanical properties for binary blends of metallocene polyethylene with conventional polyolefins

The thermal and mechanical properties for four binary blends, high-density polyethylene (HDPE)–metallocene polyethylene (MCPE), polypropylene (PP)–MCPE, poly(propylene-co-ethylene) (CoPP)–MCPE, and poly(propylene-co-ethylene-co-1-butene) (TerPP)–MCPE were investigated to compare the compatibility and molecular micromechanism of the blends. We report in this work all the blend systems that are thermodynamically immiscible but mechanically compatible which have been understood by their thermal and mechanical behaviors. A lower content of MCPE (up to 50%) in PP–MCPE, CoPP–MCPE, and TerPP–MCPE blends showed discernibly two β transitions, whereas β relaxation was shifted to a lower temperature with the MCPE content in the HDPE–MCPE system. These results conclude that the degree of compatibility in the HDPE–MCPE blend is the largest among the blend systems that we have studied, which also can be explained in terms of the similar chemical structure of polyolefins. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2441–2450, 1998     

Structure and properties of PP/POE/HDPE blends

This work was aimed to counteract the effect of ethylene‐α‐olefin copolymers (POE) by reinforcing the polypropylene (PP)/POE blends with high density polyethylene (HDPE) particles and, thus, achieved a balance between toughness and strength for the PP/POE/HDPE blends. The results showed that addition of HDPE resulted in an increasing wide stress plateau and more ductile fracture behavior. With the increase of HDPE content, the elongation at break of the blends increased rapidly without obvious decrease of yield strength and Young's modulus, and the notched izod impact strength of the blends can reach as high as 63 kJ/m² at 20 wt % HDPE loading. The storage modulus of PP blends increased and the glass transition temperature of each component of the blends shifted close to each other when HDPE was added. The crystallization of HDPE phase led to an increase of the total crystallinity of the blend. With increasing HDPE content, the dispersed POE particle size was obviously decreased, and the interparticle distance was effectively reduced and the blend rearranged into much more and obvious core‐shell structure. The fracture surface also changed from irregular striation to the regularly distant striations, displaying much obvious character of tough fracture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

HNBR/EPDM共混物结构与性能研究

分别采用过氧化物和硫给予体作交联剂,考察了不同共混比对氢化丁腈橡胶（ＨＮＢＲ）／ＥＰＤＭ共混物性能的影响,并能力ＤＳＣ和ＴＥＭ分析了共混物的相容性,对两胶的共硫化也作了初步探讨。结果表明,两种硫化体系硫化的共混胶扯断伸长率保持率均在６０％以上,都具有优异的耐热氧老化性能。随ＨＮＢＲ用量增大,共混物的定伸应力、拉伸强度和撕裂强度均提高,磨耗明显降低。ＨＮＢＲ和ＥＰＤＭ为不相容体系,但硫化仪曲线显示二     

Poly(ethylene terephthalate)/polypropylene reactive blends through isocyanate functional group

To evaluate the compatibilization effects of an isocyanate group on poly(ethylene terephthalate)/polypropylene (PET/PP) blends through a reactive blend, PP grafted with 2‐hydroxyethyl methacrylate‐isophorone diisocyanate (PP‐g‐HI) was prepared and blended with PET. In view of the blend morphology, the presence of PP‐g‐HI reduced the particle size of the dispersed phase by the reduced interfacial tension between the PP and PET phases, indicating the in situ copolymer (PP‐g‐PET) generated during the melt blending. The DSC thermograms for the cooling run indicated that the PET crystallization in the PP‐g‐HI rich phase was affected by the chemical reactions of PET and PP‐g‐HI. The improved mechanical properties for the PET/PP‐g‐HI blends were shown in the measurement of the tensile and flexural properties. In addition, the water absorption test indicated that the PET/PP‐g‐HI blend was more effective than the PET/PP blend in improving the water resistance of PET. The positive properties of PET/PP‐g‐HI blends stemmed from the improved compatibilization of the PET/PP blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1056–1062, 2001     

Polypropylene/ABS terpolymer blends. Mixing and mechanical properties

A typical commercial polypropylene and acrylonitrile–butadiene–styrene terpolymer were coextruded and injection molded in various ratios and as the pure components. The rheological properties of the pure components in a single screw extruder were analyzed. Tensile and impact properties were compared with those of the pure polymers. Stress relaxation was analyzed by a simple three-element model. The data were related to the processing conditions. The morphology of the blends was inferred from extractive and staining tests on the blends.     

Preparation of HDPE/SEBS‐g‐MAH and its effect on mechanical properties of HDPE/wood flour composites

In this article, high density polyethylene/styrene‐ethylene‐butylene‐styrene block copolymer blends (HDPE/SEBS) grafted by maleic anhydride (HDPE/SEBS‐g‐MAH), which is an effective compatibilizer for HDPE/wood flour composites was prepared by means of torque rheometer with different contents of maleic anhydride (MAH). The experimental results indicated that MAH indeed grafted on HDPE/SEBS by FTIR analysis and the torque increased with increasing the content of maleic anhydride and dicumyl peroxide (DCP). Styrene may increase the graft reaction rate of MAH and HDPE/SEBS. When HDPE/SEBS MAH was added to HDPE/wood flour composites, tensile strength and flexural strength of composites can reach 25.9 and 34.8 MPa in comparison of 16.5 and 23.8 MPa (without HDPE/SEBS‐g‐MAH), increasing by 157 and 146%, respectively. Due to incorporation of thermoplastic elastomer in HDPE/SEBS‐g‐MAH, the Notched Izod impact strength reached 5.08 kJ m^?2, increasing by 145% in comparison of system without compatibilizer. That HDPE/SEBS‐g‐MAH improved the compatibility was also conformed by dynamic mechanical measurement. Scanning electron micrographs provided evidence for strong adhesion between wood flour and HDPE matrix with addition of HDPE/SEBS‐g‐MAH. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Super polyolefin blends achieved via dynamic packing injection molding: the morphology and mechanical properties of HDPE/EVA blends

As a part of long-term project aimed at super polyolefin blends, in this work, we report the mechanical reinforcement and phase morphology of the blends of high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) achieved by dynamic packing injection molding. The shear stress (achieved by dynamic packing injection molding) and interfacial interaction (obtained by using EVA with different VA content) have a great effect on phase morphology and thus mechanical properties. The super HDPE/EVA blends having high modulus (1.9–2.2 GPa), high tensile strength (100–120 MPa) and high impact strength (six times as that of pure HDPE) have been prepared by controlling the phase separation, molecular orientation and crystal morphology of the blends. The phase inversion was also found to shift towards lower EVA content under shear stress. The enhancement of tensile strength and modulus originates from the formation of oriented layer, while the high impact strength is related to shear induced phase morphology. DSC studies indicated that the shish kebab crystal structure that also contributes to the enhancement of tensile strength is formed in the oriented layer. The dramatic improvement of impact strength may result from the formation of microfibers and elongated EVA particles along the flow direction. Wu's toughening theory was found non-applicable for the elongated and oriented rubber particles, and a brittle–ductile–brittle transition was observed with increasing EVA content.     

HDPE/LLDPE/POE薄膜性能的研究

采用线型低密度聚乙烯（LLDPE）和热塑性弹性体乙烯-辛烯共聚物（POE）对高密度聚乙烯（HDPE）薄膜进行改性,研究了LLDPE和POE对共混体系薄膜力学性能、加工性能的影响,探讨了LLDPE增强HDPE的机理。结果表明,加入一定量LLDPE,使HDPE／LLDPE薄膜的拉伸强度较纯HDPE薄膜有所增加,而单位冲击破损质量则有所下降。当w（LLDPE）为15％时,HDPE／LLDPE薄膜的拉伸强度提高21．6％,薄膜的单位冲击破损质量降低23．0％。在HDPE／LLDPE/POE三元体系中,当w（POE）,w（LLDPE）分别为10％,15％时,薄膜的拉伸强度、单位冲击破损质量、断裂伸长率比纯HDPE薄膜分别提高2．3％,113％。36．0％,综合性能良好。     

HDPE/ROSIN blends: I-Morphology, mechanical and rheological properties

SUMMARY Melting mixtures of high density polyethylene (HDPE) and glycerol ester of hydrogenated rosin (ester gum) were prepared under select conditions using up to 50% of rosin. All blends showed phase separation. The size of rosin domains varied with the content of low molecular weight constituent. The 50/50 blend showed the highest dispersion and the presence of micro and macro rosin domains. Up to 20% rosin a slight decrease of Young's modulus was noticed while above this rosin content a slight increase occurred. The stress and elongation dropped markedly above 10% of rosin. The hardness of blends showed the same behavior as the elastic modulus. The melt flow index increased exponentially with the rosin content while processability has improved. Received: 7 May 1997/Revised version: 20 March 1998/Accepted: 14 April 1998     

Thermal decomposition behavior of miscible cellulose/synthetic polymer blends

The thermal decomposition behavior of the miscible cellulosic blends cellulose(Cell)/poly(N-vinyl-2-pyrrolidone) (PVP), Cell/poly(ethylene glycol) (PEG), and Cell/poly(vinyl alcohol) (PVA) was investigated by thermogravimetry. The thermal stability of Cell in the Cell/PVP blends decreased but that of Cell in the Cell/PEG and Cell/PVA blends was hardly influenced. The thermal stability of synthetic polymers in the blends was little affected. The difference in thermal decomposition behavior was correlated to the difference in miscibility. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2133–2137, 1998     

Crystallization,melting behavior,and morphology of BPP/HDPE blend

The crystallization, melting behavior, and morphology of a low ethylene content block propylene–ethylene copolymer (BPP) and a high-density polyethylene (HDPE) blend were studied. It was found that the existence of ethylene–propylene rubber (EPR) in BPP has more influence on the crystallization of HDPE than on that of PP. This leads to the decreasing of the melting temperature of the HDPE component in the blends. It is suggested that the EPR component in BPP shifted to the HDPE component during the blending process. The crystallinity of the HDPE phase in the blends decreased with increasing BPP content. The morphology of these blends was studied by polarized light microscopy (PLM) and SEM. For a BPP-rich blend, it was observed that the HDPE phase formed particles dispersed in the PP matrix. The amorphous EPR chains may penetrate into HDPE particles to form a transition layer. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2469–2475, 1998     

Influence of nanoclay on properties of HDPE/wood composites

Composites based on high density polyethylene (HDPE), pine flour, and organic clay were made by melt compounding and then injection molding. The influence of clay on crystallization behavior, mechanical properties, water absorption, and thermal stability of HDPE/pine composites was investigated. The HDPE/pine composites containing exfoliated clay were made by a two‐step melt compounding procedure with the aid of a maleated polyethylene (MAPE). The use of 2% clay decreased the crystallization temperature (T_c), crystallization rate, and the crystallinity level of the HDPE/pine composites, but did not change the crystalline thickness. When 2% MAPE was added, the crystallization rate increased, but the crystallinity level was further lowered. The flexural and tensile strength of HDPE/pine composites increased about 20 and 24%, respectively, with addition of 1% clay, but then decreased slightly as the clay content increased to 3%. The tensile modulus and tensile elongation were also increased with the addition of 1% clay. The impact strength was lowered about 7% by 1% clay, but did not decrease further as more clay was added. The MAPE improved the state of dispersion in the composites. Moisture content and thickness swelling of the HDPE/pine composites was reduced by the clay, but the clay did not improve the composite thermal stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007