Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

Poly(lactic acid)/poly(butylene succinate)/calcium sulfate whiskers biodegradable blends prepared by vane extruder: Analysis of mechanical properties,morphology, and crystallization behavior

Ternary blends of PLA/PBS/CSW with different weight fractions were prepared using a vane extruder. The mechanical properties, morphology, crystallization behavior and thermal stability of the blends were investigated. For the PLA/CSW blend, the tensile strength decreased, the flexural strength and modulus increased compared with pure PLA. For PBS, the addition of CSW had little influence on the mechanical properties. For the ternary blends PLA/PBS/CSW, the tensile strength, flexural strength and modulus decreased compared with pure PLA, while the elongation at break and the impact strength increased significantly. The brittle-ductile transition of the blends took place when the PBS weight fraction reaching 30 wt%. As a soft component in the blends, PBS was beneficial to improve the tensile ductility and the toughness of PLA. SEM measurements reveal that PLA/PBS/CSW blends were immiscible. When the weight fraction of PBS was 50 wt%, significant phase separation was observed, and CSW had preferential location in the PBS phase of the blend. DSC measurement and POM observation reveal that CSW had a heterogeneous nucleation effect on PLA and PBS matrix. The addition of PBS improved the crystallization of PLA and the thermal resistance of the PLA/PBS/CSW blends significantly.     

Polylactide/exfoliated graphite nanocomposites with enhanced thermal stability,mechanical modulus,and electrical conductivity

We have prepared a series of polylactide/exfoliated graphite (PLA/EG) nanocomposites by melt‐compounding and investigated their morphology, structures, thermal stability, mechanical, and electrical properties. For PLA/EG nanocomposites, EG was prepared by the acid treatment and following rapid thermal expansion of micron‐sized crystalline natural graphite (NG), and it was characterized to be composed of disordered graphite nanoplatelets. It was revealed that graphite nanoplatelets of PLA/EG nanocomposites were dispersed homogeneously in the PLA matrix without forming the crystalline aggregates, unlike PLA/NG composites. Thermal degradation temperatures of PLA/EG nanocomposites increased substantially with the increment of EG content up to ～3 wt %, whereas those of PLA/NG composites remained constant regardless of the NG content. For instance, thermal degradation temperature of PLA/EG nanocomposite with only 0.5 wt % EG was improved by ～10 K over PLA homopolymer. Young's moduli of PLA/EG nanocomposites increased noticeably with the increment of EG content up to ～3 wt %, compared with PLA/NG composites. The percolation threshold for electrical conduction of PLA/EG nanocomposites was found to be at 3–5 wt % EG, which is far lower graphite content than that (10–15 wt % NG) of PLA/NG composites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 850–858, 2010     

微生物合成的β-羟基丁酸酯与β-羟基已酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx).采用拉伸力学试验研究了共混物的力学性能.通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究.实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高.但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快.综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性.     

微生物合成的β-羟基丁酸酯与β-羟基己酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx)。采用拉伸力学试验研究了共混物的力学性能。通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究。实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高。但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快。综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性。     

Silkworm silk/poly(lactic acid) biocomposites: Dynamic mechanical, thermal and biodegradable properties

Silkworm silk/Poly(lactic acid) (silk/PLA) biocomposites with potential for environmental engineering applications were prepared by using melting compound methods. By means of Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Coefficient of thermal expansion test, Enzymatic degradation test and Scanning electron microscopy (SEM), the effect of silk fiber on the structural, thermal and dynamic mechanical properties and enzymatic degradation behavior of the PLA matrix was investigated. As silk fiber was incorporated into PLA matrix, the stiffness of the PLA matrix at higher temperature (70-160 °C) was remarkably enhanced and the dimension stability also was improved, but its thermal stability became poorer. Moreover, the presence of silk fibers also significantly enhanced the enzymatic degradation ability of the PLA matrix. The higher the silk fiber content, the more the weight loss.     

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.     

Properties of immiscible and ethylene-butyl acrylate-glycidyl methacrylate terpolymer compatibilized poly (lactic acid) and polypropylene blends

Poly(lactic acid) (PLA) and polypropylene (PP) blends of various proportions were prepared by melt-compounding. The miscibility, phase morphology, thermal behavior, and mechanical and rheological properties of the blends were investigated. The blends were immiscible systems with two typical morphologies, spherical droplet and co-continuous, and could be obtained at various compositions. Complex viscosity, storage modulus and loss modulus depend on the PP content. Thermal degradation of all blends led to two weight losses, for PLA and PP. The incorporation of PP improved the thermal stability of the blend. The effect of compatibilizer (ethylene-butyl acrylate-glycidyl methacrylate terpolymer, EBA-GMA) on the morphology and mechanical properties of 70/30 w/w PLA/PP blends was investigated. The tensile strength of these blends reached a maximum for 2.5 wt% EBA-GMA, and impact strength increased with increasing EBA-GMA content, suggesting that EBA-GMA is an effective compatibilizer for PLA/PP blends.     

脂肪族聚碳酸酯(PPC)与聚乳酸(PLA)共混型生物降解材料的热学性能、力学性能和生物降解性研究

通过溶液浇铸法制备了脂肪族聚碳酸酯与聚乳酸的共混物(PPC/PLA).采用示差热分析(DSC)和热重分析(TG)研究了材料的热性能.采用拉伸力学试验研究了共混物的力学性能.通过土壤悬浊拟环境培养降解实验法和扫描电子显微镜分析(SEM)对共混材料的生物降解性能进行了研究.实验结果表明,随着PPC含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高.但是,在一定的降解时间内,某些比例共混物的降解速率比100%PPC还要快.综合分析表明,PPC/PLA是力学性能和降解性能可以互补的共混体系.     

Structure and properties of blend membranes prepared from cellulose and alginate in NaOH/urea aqueous solution

Regenerated cellulose (RC)/alginic acid (AL) blend membranes were satisfactorily prepared from 6 wt % NaOH/4 wt % urea aqueous solution by coagulating with 5 wt % CaCl₂ aqueous solution, and then treated with 3 wt % HCl. Morphology, crystallinity, mechanical properties, and thermal stability of the membranes were investigated by scanning electron microscopy (SEM), IR and UV spectroscopes, X‐ray diffraction, tensile tests, and thermogravimetric analysis (TGA). The RC/AL blends were miscible in all weight ratios of cellulose to alginate. The membranes have homogeneous mesh structures, and the mesh sizes of the blend membranes (200–2000 nm) significantly increased with increasing alginate content. The crystalline state of the AL membrane prepared from 6 wt % NaOH/4 wt % urea aqueous solution was broken completely, and the crystallinity of the blend membranes decreased with an increase of AL. Comparing with AL membranes, the tensile strength and breaking elongation of the blend membranes were obviously improved in dry and wet states. Therefore, the RC/AL blends offer a promising way of alginate as separate and functional materials used in the wet state. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 451–458, 2001     

PLA,PPC和PHBV共混物的热性能、力学性能和生物降解性能研究

将聚乳酸(PLA)、聚碳酸酯(PPC)及β-羟基丁酸酯与β-羟基戊酸酯共聚物(PHBV)以溶液浇注法制备了各种不同比例的共混膜(60/20/20,40/20/40,40/40/20,20/60/20,20/40/40,20/20/60)。采用示差扫描量热分析(DSC)和热重分析(TG)研究了共混物的热性能,采用万能材料试验机研究了共混物的力学性能,通过土壤悬浊拟环境降解实验和扫描电子显微镜(SEM)研究了共混材料的环境生物降解性能。结果显示,该三元共混体系是部分相容的体系,PLA增加了材料的强度,PPC增加了材料的断裂伸长,PHBV则提高了材料的环境生物降解速率,三者优势互补,是一种有应用前景的生物降解共混体系。     

The Influence of Peroxide on Bubble Stability and Rheological Properties of Biobased Poly(lactic acid)/Natural Rubber Blown Films

This study investigated the effects of natural rubber(NR)and an organic peroxide on the rheological properties,mechanical properties,morphology,and bubble stability during film blowing of poly(lactic acid)(PLA).The NR and peroxide contents were varied from 0 wt%to 25 wt%and 0 wt%to 0.5 wt%,respectively.The results confirmed that the presence of well-dispersed NR could significantly improve the toughness,elongation at break,and processability of PLA films,where the optimal amount of NR was 15 wt%.For the reactive blending with peroxide,a suitable peroxide content for good film toughness and clarity was 0.03 wt%,while the higher content of 0.1 wt%could provide slightly higher processability.These contents are considered much lower than that in the PLA system(without NR),which required up to 0.5 wt%peroxide.The rheological studies indicated that the melt strength,the storage modulus(G’)and complex viscosity(η*)at low frequency could be correlated with good film blowing processability of the PLA/NR films at low gel contents.These parameters failed to correlate in the films having high gel contents as the deformation rate experienced by each test was different leading to the different levels of response to the type and amount of gels.     

Physico-Mechanical Properties of Biodegradable Rubber Toughened Polymers

Summary: In this study, blends of poly(lactic acid) (PLA) with poly(butylene adipate-co-terephthalate) (PBAT) were studied for their mechanical and thermal properties as a function of the PBAT content. Tensile testing, impact testing, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA) and scanning electron microscopy (SEM) were used to characterize the blends. It was observed that PLA/PBAT blends maintained quite high modulus and tensile strength compared to pure PLA. Small amounts of PBAT improved the elongation at break and the impact resistance showing a debonding effect typical of rubber toughened systems.     

Poly(hydroxyether of bisphenol A)/poly(vinyl acetate) blends: In situ polymerization preparation,morphology, and properties

The blends of poly(hydroxyether of bisphenol A) (phenoxy) and poly(vinyl acetate) (PVAc) were prepared through in situ polymerization, i.e., the melt polymerization of diglycidy ether of bisphenol A (DGEBA) and bisphenol A in the presence of PVAc. The polymerization reaction started from the initial homogeneous ternary mixture of PVAc/DGEBA/bisphenol A; the phase separation induced by reaction occurred as the polymerization proceeded. The phenoxy/PVAc blends with PVAc content up to 20 wt % were obtained and were further characterized by the solubility, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electronic microscopy (SEM). The results indicate that no intercomponent reaction occurred during the in situ polymerization. All the blends display separate glass transition temperatures (Tg's); the very fine phase-separated morphology was obtained by this polymerization blending method. Mechanical tests show that the prepared blends exhibited substantial improvement of mechanical properties, especially in impact strength, which could be ascribed to the formation of the fine phase-separation morphology during in situ polymerization. The thermogravity analysis (TGA) of the blends showed that the thermal stability of the PVAc-rich phases in the blends was enhanced in comparison to the pure PVAc due to the synergistic contribution of the two phases in energy transportation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2329–2338, 1999     

Compatibility and thermal properties of poly(3‐hydroxybutyrate)/poly(glycidyl methacrylate) blends

Poly(3‐hydroxybutyrate) (PHB)/poly(glycidyl methacrylate) (PGMA) blends were prepared by a solution‐precipitation procedure. The compatibility and thermal decomposition behavior of the PHB/PGMA blends was studied with differential scanning calorimetry, thermogravimetric analysis, and differential thermal analysis (DTA). The blends were immiscible in the as‐blended state, but for the blends with PGMA contents of 50 wt % or more, the compatibility was dramatically changed after 1 min of annealing at 200 °C. In addition, PHB/PGMA blends showed higher thermal stability, as measured by maximum decomposition temperatures and residual weight during thermal degradation. This was probably due to crosslinking reactions of the epoxide groups in the PGMA component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in the DTA thermograms. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 351–358, 2002     

Studies on poly(ε‐caprolactone)/thiodiphenol blends: The specific interaction and the thermal and dynamic mechanical properties

The effects of several low molecular weight compounds with hydroxyl groups on the physical properties of poly(ε‐caprolactone) (PCL) were investigated by Fourier transform infrared (FTIR) spectroscopy and high‐resolution solid‐state ¹³C NMR. PCL and 4,4′‐thiodiphenol (TDP) interact through strong intermolecular hydrogen bonds and form hydrogen‐bonded networks in the blends at an appropriate TDP content. The thermal and dynamic mechanical properties of PCL/TDP blends were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis, respectively. The melting point of PCL decreased, whereas both the glass‐transition temperature and the loss tangent tan δ of the blend increased with an increase in TDP content. The addition of 40 wt % TDP changed PCL from a semicrystalline polymer in the pure state to a fully amorphous elastomer. The molecules of TDP lost their crystallizability in the blends with TDP contents not greater than 40 wt %. In addition to TDP, three other PCL blend systems with low molecular weight additives containing two hydroxyl groups, 1,4‐dihydroxybenzene, 1,4‐di‐(2‐hydroxyethoxy) benzene, and 1,6‐hexanediol, were also investigated with FTIR and DSC, and the effects of the chemical structure of the additives on the morphology and thermal properties are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1848–1859, 2000     

聚乳酸/羧基化聚丙烯共混物的形态与热性能研究

以扫描电子显微镜、热重分析仪、差示扫描量热仪、热台偏光显微镜分别研究了聚乳酸/羧基化聚丙烯共混体系的相形态、热性能和结晶形态.结果显示,共混物熔体冷却时,聚乳酸和羧基化聚丙烯均形成球晶,但羧基化聚丙烯球晶较大而十字消光较暗,聚乳酸球晶尺寸较小而十字消光较亮,且聚乳酸球晶产生规则的、不连续的同心环线——裂纹,裂纹厚度约为1~2μm,且裂纹内部有微纤存在.当聚乳酸含量≤50%时,由于聚丙烯上羧基的存在而使共混体系具有较好的相容性.共混物的热分解过程分为三个阶段,热分解温度的变化是聚丙烯上的羧基、聚乳酸和聚丙烯骨架分解三种机制共同作用的结果,少量聚乳酸能够明显提高共混物中聚丙烯上羧基的热稳定性.共混物中的羧基化聚丙烯组分可以发挥稀释剂的作用,大幅度降低了聚乳酸的冷结晶温度.聚乳酸含量≥50%时,共混熔体降温时DSC谱图中聚乳酸和羧基化聚丙烯分别结晶,而聚乳酸含量<50%时,只观察到羧基化聚丙烯的结晶行为.     

Rheological and thermal behavior of PLA modified by chemical crosslinking in the presence of ethoxylated bisphenol A dimethacrylates

Crosslinking structures can be partly introduced into PLA by melt mixing in a twin screw extruder with dicumyl peroxide (DCP) and ethoxylated bisphenol A dimethacrylates (Bis‐EMAs) as a crosslinking coagent. The study of DCP and Bis‐EMA contents on the melt rheology, thermal properties, dynamic mechanical properties and morphology of the reactive extruded pellets is presented. The results show that PLA with a DCP content higher than 3 phr exhibits increases in both the melt modulus and complex viscosity as compared with PLA. The introduction of DCP into PLA improved the thermal stability of the PLA. PLAs with various Bis‐EMA contents showed the optimum storage modulus and complex viscosity to occur at 5 phr Bis‐EMAs. Moreover, the glass transition, cold crystallization and melting temperature of PLAs decreased with increasing Bis‐EMA content. The crystallinity of the partly crosslinked PLAs was lower than that of PLA. Similar to the rheological results, the thermo‐mechanical properties showed that the storage modulus and loss modulus of the partly crosslinked PLAs increased with increasing Bis‐EMA contents up to 5 phr. In addition, these partly crosslinked PLAs showed rough surface or sea island‐like structure. Copyright © 2016 John Wiley & Sons, Ltd.     

Nanoindentation,nanoscratch, and nanotensile testing of poly(vinylidene fluoride)‐polyhedral oligomeric silsesquioxane nanocomposites

Nanocomposites composed of a poly(vinylidene fluoride) (PVDF) matrix and 0, 3, 5, and 8 wt % fluoropropyl polyhedral oligomeric silsesquioxane (FP‐POSS) were prepared by using the solvent evaporation method. The morphology and the crystalline phase of the nanocomposites were investigated by digital microscopy, scanning probe microscopy, X‐ray diffractometer, and Fourier transform infrared spectroscopy. FP‐POSS acted as nucleating agent in PVDF matrix. A small content of FP‐POSS resulted in an incomplete nucleation of PVDF and generated bigger spherical particles, whereas higher contents led to a complete nucleation and formed more separate and less‐crosslinked particles. Nanoindentation, nanoscratch, and nanotensile tests were carried out to study the influence of different contents of FP‐POSS on the key static and dynamic mechanical properties of different systems. The nanocomposite with 3 wt % FP‐POSS was found to possess enhanced elastic properties and hardness. However, with the increase of the FP‐POSS content, the elastic modulus and hardness were found to decrease, and the improvement on stiffness was negative at contents of 5 and 8 wt %. Compared with neat PVDF, the scratch resistance of the PVDF/FP‐POSS nanocomposites was decreased due to a rougher surface derived from the bigger spherulites. Nanotensile testing results showed both the stiffness and toughness of PVDF‐FP_3% were enhanced and further additions of FP‐POSS brought dramatic enhancements in toughness while associated with a decline in stiffness. Dynamical mechanical properties indicated the viscosity of the nanocomposites increased with the increasing FP‐POSS contents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Physical blends of PLA with high vinyl acetate containing EVA and their rheological,thermo-mechanical and morphological responses

Rheological, morphological and thermo-mechanical responses of poly(lactic acid) (PLA)/ethylene-co-vinyl-acetate copolymer (EVA) blends at EVA volume fractions varying in the range of 0–0.35 were evaluated. The micro-structural analysis demonstrated dispersive mixing at low content and co-continuous morphology at 30 wt % of EVA in PLA. Dynamic rheology demonstrated enhanced storage modulus and complex viscosity (η*) with increase in frequency of the blends indicated strong phase interaction. Cole-Cole and Han plots indicated partial miscibility and incompatibility between the polymer matrix and the dispersed phase. Dynamic mechanical analysis (DMA) revealed slight increase in damping parameters which indicated interaction or reinforcement in the blends. Additionally, the thermogravimetric analysis (TGA) of the blends showed two step degradation and enhanced thermal stability.