Monitoring the Evolution of Morphology of Polymer Blends Upon Manufacturing of Microfibrillar Reinforced Composites

Abstract

Microfibrillar reinforced composites (MFC) based on HDPE/PET blends were prepared under conditions relevant for direct scale-up to an industrial process. The evolution of the morphology and of the linear viscoelastic response of the blend along the axis of a co-rotating twin screw extruder and at several locations along the extrusion line was monitored. Major changes in the average particle size and size distribution of the disperse phase occurred upon melting of the components, whilst a much slower evolution rate was evident downstream in the extruder. Simultaneously, G′ and G″ increased along the extruder. Pellets showing well oriented PET fibrils embedded in a HDPE matrix with poor adhesion between both were obtained. This MFC showed the typical improvement expected in mechanical performance when compared with the matrix.     

Recyclability of In Situ Microfibrillar Poly(ethylene terephthalate)/High‐Density Polyethylene Blends

Repetitive processing was employed to assess the recyclability of in situ microfibrillar poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) blends which were fabricated through a “rectangular slit die extrusion–hot stretching–quenching” process. For comparison, the conventional PET/HDPE blends were also obtained using the same processing operation but without hot stretching. The morphological observation indicated that slit die extrusion and hot stretching successfully made the dispersed PET phase deform in situ into well‐defined microfibrils. The average diameter of the microfibrils increased with the processing cycles. The rheological properties obtained from the parallel‐plate dynamic rheometer suggested that the microfibrillar blends have higher viscosity and viscoelastic moduli (storage and loss moduli) as well as better flow stability than the conventional PET/HDPE blend. More importantly, with the increase in the processing cycles, an increase in yield strength and unchanged tensile modulus were observed for in situ microfibrillar blends, while a decrease in these properties for conventional blend, indicating that the in situ microfibrillar PET/HDPE blends have promising recycling potential.

     

The Influence of NBR-g-GMA Compatibilizer on the Morphology and Mechanical Properties of Poly (ethylene terephthalate)/Polycarbonate/NBR Ternary Blends

The work aims to study the role of NBR-g-GMA compatibilizer on the morphology and mechanical characteristics of PET/PC/NBR ternary blends. The compatibilizer content and amount of constitutive polymers are changed to correlate morphology development with mechanical properties. Various ternary samples are prepared using a twin-screw extruder whereat weight percent of rubbery dispersed phase (NBR+NBR-g-GMA) is changed. Analyzing the morphology of produced samples and interpretation of mechanical properties corroborated the role of the mentioned factors on the type of morphology and also the size of both individual and composite domains in these sorts of ternary blends. Based on this attempt, the mechanical properties of 50/50 blends of NBR/NBR-g-GMA, showed maximum toughness value compared to pure PET specimen. Also, the results revealed that by increasing the rubber content, the rodlike structures were disappeared; besides, toughness was increased. On the contrary, by increasing PC content, rodlike structures have seen by morphological study; however, core-shell droplets formed in the blend structure caused enhancing the impact strength and reducing Young's modulus. Ultimately, the ternary blend of 63/7/30 of PET/PC/ (NBR+NBR-g-GMA) revealed the best mechanical properties due to proper interaction between the PET matrix and rubbery domains in the presence of reactive compatibilizer.     

Mechanical and Rheological Properties of Poly(ethylene terephthalate)/ Polypropylene Blends

Poly(ethylene terephthalate) and polypropylene (PET/PP) were compounded and pelletized with a single-screw extruder. Standard ASTM tensile test specimens were made by injection moulding. The blends are stronger and stiffer than the plain PP specimens. The addition of a compatibilizer, EPOLENE E-43, is found to improve the strength and stiffness of the blends at loadings of 50% and 70% PET. At 10% PET loading, E-43 has the opposite effect of slightly reducing the tensile properties. All the blends are more brittle relative to either plain PET or PP. The addition of E-43 results in negligible improvement in the elongation at break. E-43 is also found to be an effective lubricant in improving the processability of the blends. The blends with E-43 added have lower viscosities and less shear-thinning characteristics than those without E-43. © 1997 SCI.     

原位微纤增强复合材料的结构与性能

采用熔融挤出——热拉伸——牵引拉伸制备了HDPE/PA6原位成纤增强复合材料,通过SEM分析了分散相PA6含量对其在基体中的形态及分布的影响;讨论了两种加工方式条件下分散相PA6含量对复合材料拉伸性能和冲击韧性的影响以及加工方式对复合体系力学性能的影响。结果表明：在原位成纤增强复合材料中存在直径为2～5 μm的纤维,当HDPE/PA6质量比为85/15时,微纤直径约为3 μm,此时,与普通共混复合材料相比,原位成纤增强复合材料的拉伸强度提高了6.9%,拉伸模量提高了14.8%,冲击强度提高10.03%。     

Barrier Properties of Blends Based on Liquid Crystalline Polymers and Poly(ethylene terephthalate)

Abstract

Blends of poly(ethylene terephthalate) (PETP) and two different thermotropic liquid crystalline (LC) polymers of the Vectra-type were prepared by melt mixing. Oxygen and water vapor permeability, light transmission and welding properties were measured on compression-molded and film-blown specimens. SEM showed that the LC polymers were the disperse phase with a good phase adhesion to the PETP matrix in the majority of the compression-molded blends. The 50/50 blend based on the low melting point LC polymer showed possibly a continuous LC polymer phase. The film-blown specimens showed LC polymer spheres at low LC polymer content. Above a certain LC polymer content (10-30% LC polymer), fibrous and ellipsoidal LC polymer particles was the dominant morphological feature of the blends. Density measurements showed that the void content in the blends was low. The compression-molded blends based on the high melting point LC polymer showed permeabilities conforming to the Maxwell equation assuming low permeability (LC polymer) spheres in a high permeability (PETP) matrix. The compression-molded blends based on the low melting point Vectra showed lower permeabilities than predicted by the Maxwell equation, particularly at high LC polymer content. The film-blown blends showed extensive scattering in the permeability data. The blend with 30% low melting LC polymer exhibited a 96% lower oxygen permeability than PETP. This was due to a reduction in both oxygen diffusivity and solubility. Ellipsoidal and fibrous LC polymer particles increased the diffusional path and lowered the diffusivity. The transparency of the compression-molded samples was lost already at 1% LCP. The blends showed welding properties superior to those of PETP.     

Nanofibrillar Single Polymer Composites of Poly(ethylene terephthalate)

Using the experience gained from the development of polymer–polymer nanofibrillar composites (NFCs), an attempt was undertaken to manufacture PET single polymer nanofibrillar composites. For this purpose polypropylene (PP) was removed by selective extraction from a knitted textile manufactured with PP/PET (80:20 by wt) blend. The remaining PET nanofibrillar textile was then sandwiched between lower‐melting PET films and compression molded at 120 °C. The obtained PET single polymer NFCs comprised PET nanofibrils as reinforcement and showed an improvement in the tensile strength and modulus of 37–100 and 40–140%, respectively (depending on the annealing temperature after compression molding and the test direction) compared to those of the starting isotropic matrix film.

     

HDPE/r-PET原位微纤物微观形态与力学性能

以高密度聚乙烯(HDPE)和回收聚对苯二甲酸乙二醇酯(r-PET)为原料,通过反应挤出、冷拉伸、退火工艺制备了HDPE/r-PET原位微纤物。研究了扫描电镜(SEM)的制样方法即用液氮冷冻、脆断样品、聚四氟乙烯带包覆、在沸腾的二甲苯中刻蚀7～10min和不同r-PET用量、不同拉伸比制备出的系列HDPE/r-PET原位微纤物的力学性能。结果表明,通过SEM可清晰地看到形成的微纤,原位微纤物的拉伸强度和冲击强度都随拉伸比的增大而增大;r-PET质量分数为15%时,原位微纤物的拉伸强度和无缺口冲击强度达到最大值;HDPE/r-PET原位微纤物的适宜注塑温度为210℃。     

Study on Mechanical and Dielectric Properties of Jute Fiber Reinforced Low-Density Polyethylene (LDPE) Composites

Abstract

Jute fiber (Hessian cloth) reinforced low-density polyethylene (LDPE) composites were prepared by heat press molding techniques. The mechanical properties such as tensile strength (TS), bending strength (BS), and elongation at break of the composites were studied. The enhancement of TS (33%) and BS (50%) were obtained as a result of reinforcment jute fabrics in LDPE. In order to improve the mechanical properties and adhesion between jute and LDPE, hessian cloth were each treated with 2-hydroxyl ethyl methacrylate (HEMA). The HEMA-treated jute composite showed higher tensile and bending strength compared to untreated jute composite and LDPE. Dielectric properties like dielectric constant and loss tangent (tan δ) of jute, LDPE and composites were studied. Ferro to paraelectric phase transition occurred in both treated and untreated jute composites containing more than 20% jute. Water uptake behaviors of the composite were monitored and HEMA-treated composite showed lower water absorption behavior. The adhesion nature of jute and LDPE also characterized by scanning electronic microscopy (SEM), better adhesion was observed between HEMA-treated jute and LDPE over untreated ones.     

Morphology and Tensile Strength Prediction of in situ Microfibrillar Poly(ethylene terephthalate)/Polyethylene Blends Fabricated via Slit‐Die Extrusion‐Hot Stretching‐Quenching

Summary: In situ microfibrillar poly(ethylene terephthalate) (PET)/polyethylene blends (MRB) were successfully fabricated by slit‐die extrusion‐hot stretching‐quenching. The morphology of this new material is mainly influenced by the composition and the hot stretching. Appropriate PET concentrations and a comparatively high hot stretching ratio could facilitate the fibrillation of PET domains during processing. The expression employed for prediction of the tensile strength for the microfibrillar blend was proved to be desirable. The prediction was, generally, in agreement with the experimental results, although the values of some parameters were approximated.

SEM micrograph of the cryofractured surface of the in situ microfibrillar PET/PE blend after injection molding.     

PET/PTT共混聚酯的等温结晶行为

使用差示扫描量热仪(DSC)研究不同比例的PET/P1T共混聚酯在205℃的等温结晶行为,并使用Avrami方程对其等温结晶过程进行研究.结晶半周期t1/2,总结晶速率常数k和Avrami指数n的变化表明:在共混体系中,对于PET和PTT而言,另一组分的加入都会对结晶产生阻碍作用,PET与P1T相互影响成核与晶体生长机理.     

Non-isothermal Crystallization Behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) Blends

Summary Non-isothermal crystallization behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) blends was investigated by XRD and DSC. By XRD spectra analysis, it could be concluded that PET and PTT crystals coexisted. They did not form the cocrystals due to different chemical structures. The Avrami equations modified by Jeziorny and Ziabicki’s kinetic crystallizability analysis were employed to describe the non-isothermal crystallization process of PET/PTT blends. The results suggested that the entanglement of the two polymer chains decrease the crystallizability of PET and PTT in blend. The crystallization activation energies of the blend evaluated by the Friedman method also indicated that the presence of two components in the blends hinders the crystallization process of both components.     

Morphology and Properties of Deoiled Cake (DOC) Isolated Mixed Proteins and Low-Density Polyethylene Blends

Proteins were isolated from deoiled cakes (DOC) of soybean, castor and rapeseed. The isolated proteins were then blended with LDPE in different wt. ratios, using PEG₄₀₀ as a plasticizer. The morphology of the blends was evaluated by using a scanning electron microscope (SEM). Homogeneous blends were obtained and analyzed for various mechanical properties such as tensile strength, impact strength, hardness and % elongation and compared with properties of plastic sheets prepared from mixture of pure proteins. Results revealed that protein composition and amount of LDPE in proteins and LDPE blend, affects the mechanical properties of the plastic compositions considerably.     

Morphology,Thermal and Mechanical Properties of Poly(propylene) Fibre‐Matrix Composites

Preparation and properties of poly(propylene)‐poly(propylene) composites have been investigated. Poly(propylene) fibres of varying diameter have been incorporated in a random ethylene co‐poly(propylene). The composites prepared from the same semi‐crystalline polymer in the matrix and reinforcement have lead to inherently strong interfacial bonding between the two phases of the same polymer. The composites demonstrated enhanced stiffness, which increased with fibre diameter. The structure, thermal, static and mechanical properties of poly(propylene) long fibre reinforced random co‐poly(propylene) composites have been studied with reference to the fibre diameter. The matrix and fibre components retained their separate melting temperatures. After melting, the two phases remained separate and showed their individual crystallization temperatures on cooling, and melting temperatures on a second heating. The melting temperature of the poly(propylene) fibres increased after formation of the composites. The compression molding of the composites at a temperature below the melting temperature of the fibres caused annealing of the fibre crystals. By incorporation of long poly(propylene) fibre into random co‐poly(propylene), the glass transition, storage and static modulus have been found to be increasing and composite with the largest fibre diameter shows better properties. Transcrystallization of the matrix poly(propylene) was observed.

Optical microscopy of composites with fibre diameter 68 μm.     

Thermal and Mechanical Properties of Polyblends of Polycaprolactam with Cationic Dyeable Poly(ethylene terephthalate)

One Polycaprolactam (PCPL) polymer and three cationic dyeable poly(ethylene terephthalate) (CD-PET) polymers were blended mechanically in the proportions of 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90 in a melt twin-screw extruder to prepare twenty-seven PCPL/CD-PET polyblended polymers. The molar ratios of 5-sodium sulfonate dimethyl isophthalate (5-SSDMI) for three CD-PET polymers were 2, 6 and 10%, respectively. This study investigated the thermal and mechanical properties of PCPL/CD-PET polyblended materials using gel permeation chromatograph (GPC), nuclear magnetic resonance (NMR), gas chromatography (GC), potentiometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), extension stress-strain measurement, density gradient method and rheometer. Experimental results of the thermal properties indicated PCPL and CD-PET molecules easily formed individual domains. PCPL and CD-PET polymers were proved to be immiscible system even when CD-PET possessed higher 5-SSDMI content. Rheological behaviour of PCPL/CD-PET polyblends exhibited negative-deviation blends (NDB). The measurements of densities showed linear variation with the blend ratio of PCPL/CD-PET polyblends. The SEM pictures displayed the blend ratio of PCPL/CD-PET was 50/50, the morphological aggregation of a larger size from 3 to 5 m in diameter was observed. Experimental results of the mechanical properties indicated the 50/50 blend of PCPL/CD-PET showed a minimum tensile strength.     

PET／POE-g-MAH的性能研究

利用熔融法，采用马来酸酐接枝乙烯-辛烯共聚弹性体(POE-g-MAH)增韧聚对苯二甲酸乙二醇酯(PET)，研究了热处理对PFT／POE-g-MAH共混体系增韧效果的影响。结合共混材料的室温缺口冲击断面SEM照片，淬断刻蚀照片和宏观力学性能，分析了共混体系发生脆韧转变对应的微观形貌特征。结果表明POE-g-MAH与PET具有良好的相容性，热处理不但可以使PET／POE-g-MAH共混体系的拉伸强度增大，而且可以显著提高其冲击强度。     

Mechanical and Thermal Properties of Flexible Poly(propylene) Composites

Summary: The melting temperature difference between poly(propylene) (PP) fibre and random poly(propylene‐co‐ethylene) (PPE) was exploited to establish processing conditions for all‐PP composite. Under these conditions, the matrix must be liquid to ensure good wetting and impregnation of fibres, though temperatures must be low enough to avoid melting of fibres. The high chemical compatibility of the two components allowed creation of strong physico‐chemical interactions, favouring strong interfacial adhesion. Static and dynamic mechanical properties and morphology of all‐PP composites were investigated according to method of preparation and compared with the behaviour of hot compacted composites, prepared under different moulding conditions. The composites were compacted with varying pressure and time, and mechanical and thermal properties of the resulting sheets were measured. With increased moulding time, more fibres melted or their original properties deteriorated. Fast cooling or quenching caused imperfect morphology. Moulding pressure played an important role. Morphology of the optimum hot compacted composite was investigated using scanning electron microscopy before and after tensile testing. Tensile fracture surfaces showed a melted phase epitaxially crystallised onto the remaining orientated phase. Compacted composites showed fibre shapes under a thin layer of PPE with all of the gaps between fibres filled by melted PPE matrix.

SEM of compacted all‐PP composite without quenching.     

The Microcellular Injection Molding of Low-Density Polyethylene (LDPE) Composites

This paper reports the study of microcellular injection molding of low-density polyethylene- (LDPE) based composites. The effects of adding nanoclays and polymer additives in LDPE as well as rheological property of materials on the cell morphology, mechanical properties and surface properties of microcellular injection molded LDPE based composites are presented. For the microcellular injection molding process, when 3 wt% of nanoclays are added into LDPE-based polymers, the cell morphology can be significantly improved due to the nucleating effects resulting from the broad interface areas between polymer and nanoclays. Also, the addition of low melt flow LDPE into high melt flow LDPE could achieve smaller and denser bubbles in the polymer matrix than neat high melt flow LDPE.     

PS/SBR-g-PS共混物的力学性能和形态结构

采用种子乳液聚合技术在丁苯胶乳上接枝聚合苯乙烯 ,合成了一系列丁苯橡胶接枝聚苯乙烯共聚物 (SBR-g-PS)。将其与聚苯乙烯 (PS)树脂共混后 ,考察了 SBR-g-PS的组成 (SBR/ PS)对共混物的力学性能和形态结构的影响。结果发现 ,当 SBR/ PS为 6 7/ 33-5 0 / 5 0时 ,PS/ SBR-g-PS共混物表现出良好的综合力学性能 ,在 SBR-g-PS中随着接枝 PS的增多 ,像胶粒子在基体中的分散状况获得改善 ,在大橡胶颗粒中含有大量的 PS次级粒子。在外负载的作用下 ,共混物中的大橡胶颗粒引发了大量的银纹 ,吸收了断裂应变能 ,从而提高了材料的冲击韧性。     

Mechanical Relaxation in Solid-state Polymerized Poly(ethylene terephthalate)

Abstract

The dynamic mechanical tensile properties, storage modulus E′ and loss modulus E″, of the amorphous and semi-crystalline PET samples, ranging in molecular weight from 15,000 to 300,000 g/mol, were measured over temperature T range from 150°C to +250°C at four frequencies v=3.5, 11, 35 and 110 Hz. The samples with molecular weight larger than 15,000 were produced by solid-state polymerization in high vacuum. An increase in the height of loss β-peak, at T= ?60… -30°C, with an increase in molecular weight was found both in the amorphous and semi-crystalline PET. On the other band, the height of loss β-peak for the amorphous samples appeared to be smaller in comparison with that for the semi-crystalline samples. By contrast, the height of loss δ-peak, at T= + 90. +110°C, for the amorphous samples was larger than for the semicrystalline samples. An increase in the E value with an increase in the molecular weight of the amorphous polymer was accompanied by an increase in the E″ value. This behavior was explained by the effective interpenetrated network of the high-molecular-weight polymer and better short-range ordering in the low-molecular-weight polymer. The intensity of the β-process was found to weaken with an increase in the chain ends concentration in both the amorphous and semi-crystalline samples. This result indicates that there is no contribution of the chain ends to the process of β-relaxation in PET.