Effect of liquid isoprene rubber on dynamic mechanical properties of emulsionpolymerized styrene/butadiene rubber vulcanizates

The effect of liquid isoprene rubber (LIR) on the dynamic mechanical properties of emulsion‐polymerized styrene/butadiene rubber (ESBR) vulcanizates was investigated by temperature sweep using dynamic mechanical analysis. The introduction of LIR led to ESBR vulcanizates having higher loss factor (tan δ) in the temperature range ? 30 to 0 °C, and lower tan δ in the range 60 to 80 °C. A small amount of LIR‐403 (LIR with carboxyl groups) led to a significant change in tan δ: the addition of LIR‐403 (3 phr) led to a 7.5% increase in tan δ from ? 30 to 0 °C, and a 24.9% decrease in tan δ from 60 to 80 °C. It was found that the introduction of LIR increased the bound rubber content in the ESBR compound. Equilibrium swelling experiments showed that the crosslink density of the vulcanizates increased after the introduction of LIR‐403 or LIR‐50 (general purpose LIR). The change in tan δ from 60 to 80 °C was related to polymer–filler interactions. The characteristic constant of filler–ESBR matrix interaction (m) was calculated. At a given filler volume fraction, the increase in m in the presence of LIR could be well related to the decrease in tan δ from 60 to 80 °C. The influence of LIR on filler network in the ESBR compound was also investigated by strain and temperature sweeps using a rubber processing analyzer. Copyright © 2011 Society of Chemical Industry     

Effects of surface functionalized partially reduced graphene oxide and different compatibilizers on the properties and structure of PP/EPR nanocomposites

In this study polypropylene/ethylene-propylene rubber (PP/EPR) and different amounts of partially reduced graphene oxide (prGO) and its derivatives were investigated. The nanocomposites were also compatibilized with EPR containing diethyl maleate (DEM), glycidyl methacrylate (GMA) and maleic anhydride (MAH) functionality as a means of controlling their ultimate mechanical behaviour and their structural morphology. Mechanical tests show that the addition of pristine prGO to PP/EPR blend promotes tensile strength and Young’s modulus, while reducing elongation at break and impact strength. A significant improvement of these properties was achieved by the presence of functionalized prGO and EPR-g-DEM. TGA analysis showed that the nanocomposites exhibit a higher thermal stability than that of the matrix alone. XRD analysis revealed that the polymer chains have been successfully intercalated into prGO layers. SEM has been used to verify the dispersion of the prGO particles in the matrix and to reveal the developed morphology of PP/EPR, in the presence of compatibilizers and functionalized prGO.     

Structure development in thermoset recyclate‐filled polypropylene composites

Polypropylene containing comminuted fiber reinforced thermoset recyclate has been shown to exhibit enhanced mechanical properties relative to particulate‐filled materials. Optimum mechanical performance in these recyclate‐filled materials is achieved in compositions made from rubber‐modified polypropylene containing maleic anhydride‐modified PP in conjuction with silane coupling agent. Although matrix crosslinking was found to enhance properties in both filled and unfilled systems, composite properties are dominated by the development of strong interfacial bonding between polypropylene and recyclate reinforcement. A mechanism for the formation of interfacial bonding is proposed involving reaction between maleic anhydride functionalized PP, formation of trisilanol groups and their subsequent condensation with hydroxyl groups on the recyclate surfaces, together with molecular entanglement and co‐crystallization of the grafted and ungrafted polypropylene molecules. Furthermore, in the absence of treatment there is evidence that the elastomer particles encapsulate the filler particles. However, this effect is strongly hindered when functionalized‐PP is added, either in isolation or in combination with the silane co‐treatment. The crystalline nucleation of PP by thermoset recyclate and treatment is also considered. The treatment system investigated was found to promote interfacial bonding to both the polyester (DMC) and woven glassreinforced phenolic recyclates investigated, suggesting it may be suitable for treating mixed composite scrap.     

Completely biodegradable composites reinforced by the cellulose nanofibers of pineapple leaves modified by eco-friendly methods

In this study, cellulose nanofibers (CNF) derived from waste pineapple leaves (PALF) were incorporated into poly (lactic acid) (PLA) with the aim of developing completely biodegradable and sustainable composites. CNF was first prepared by the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) method, and then, different surface modifications of the eco-friendly method were carried out for better dispersion in the PLA matrix. Then, a series of eco-friendly modified CNF/PLA composites were prepared by melt-blending. According to the contact angle experiment, the values of eco-friendly modified CNFs increased from 12.02° to 61.49 and 57.45°, respectively. DSC thermograms show that eco-friendly modified CNFs have a significant nucleating effect for the crystallization of PLA compared to the original CNF. Mechanical testing reveals that the tensile and impact strengths of eco-friendly modified CNF containing composites are improved by 5.4~22.7% and 17.5~56.1%, respectively, through the addition of only 1~3 wt% of modified CNF, and are all higher than that of the original CNF containing composite. Moreover, eco-friendly modified CNF containing composites can allow good light transmittance due to better dispersity of the modified CNF. Consequently, the addition of modified CNFs to the PLA matrix results in increased mechanical and thermal properties of the composites, as well as transparency. Moreover, the addition of CNFs extracted from pineapple leaves by eco-friendly methods can not only reduce the amount of agriculture waste but also avoid the usage of an organic solvent and meet the requirements of environmental protection.     

One‐step latex compounding method for producing composites of natural rubber/epoxidized natural rubber/aminosilane‐functionalized montmorillonite: enhancement of tensile strength and oil resistance

Montmorillonite (Mt) was intercalated with cetyltrimethylammonium bromide and functionalized with three types of aminosilane (3‐aminopropyltrimethoxysilane, n‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane and 3‐[2‐(2‐aminoethylamino)ethylamino]propyltrimethoxysilane). The modified Mt was compounded with natural rubber (NR)/epoxidized natural rubber (ENR) via one‐step latex compounding. The effect of the modified Mt content on the oil resistance and mechanical properties of the NR/ENR/modified Mt composites was investigated. The X‐ray diffraction patterns of the composites showed partial intercalation/exfoliation of the modified Mt in the rubber matrix. Cryogenic fracture and X‐ray fluorescence results revealed highly dispersed modified Mt in the composites in the presence of 10 phr ENR. All three aminosilane groups slightly improved the oil resistance, with the long‐alkyl‐length group producing the greatest improvement. The addition of a small amount of modified Mt improved both oil resistance and tensile strength by increasing in the average diffusion path length in the NR matrix and enhancing the interaction between the modified Mt and the epoxide groups in ENR. The addition of 1.0 phr of modified Mt increased the tensile strength by 18% and decreased the elongation at break by 12% compared with a neat NR/ENR blend. © 2017 Society of Chemical Industry     

Epoxidized natural rubber/epoxy blends: Phase morphology and thermomechanical properties

Epoxidized natural rubbers (ENRs) were prepared. ENRs with different concentrations of up to 20 wt % were used as modifiers for epoxy resin. The epoxy monomer was cured with nadic methyl anhydride as a hardener in the presence of N,N‐dimethyl benzyl amine as an accelerator. The addition of ENR to an anhydride hardener/epoxy monomer mixture gave rise to the formation of a phase‐separated structure consisting of rubber domains dispersed in the epoxy‐rich phase. The particle size increased with increasing ENR content. The phase separation was investigated by scanning electron microscopy and dynamic mechanical analysis. The viscoelastic behavior of the liquid‐rubber‐modified epoxy resin was also evaluated with dynamic mechanical analysis. The storage moduli, loss moduli, and tan δ values were determined for the blends of the epoxy resin with ENR. The effect of the addition of rubber on the glass‐transition temperature of the epoxy matrix was followed. The thermal stability of the ENR‐modified epoxy resin was studied with thermogravimetric analysis. Parameters such as the onset of degradation, maximum degradation temperature, and final degradation were not affected by the addition of ENR. The mechanical properties of the liquid‐natural‐rubber‐modified epoxy resin were measured in terms of the fracture toughness and impact strength. The maximum impact strength and fracture toughness were observed with 10 wt % ENR modified epoxy blends. Various toughening mechanisms responsible for the enhancement in toughness of the diglycidyl ether of the bisphenol A/ENR blends were investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39906.     

液体聚异戊二烯对天然橡胶/聚丁二烯橡胶硫化胶微观结构和性能的影响

研究了液体聚异戊二烯(LIR)作为增塑剂对天然橡胶(NR)/聚丁二烯橡胶(BR)硫化胶微观结构、弯曲疲劳性能、压缩疲劳性能和动态力学性能的影响,并与加入工业用增塑剂芳烃油的硫化胶进行了对比。结果表明,加入LIR较芳烃油有利于炭黑在NR/BR体系中的分散;随着LIR用量的增加,NR/BR硫化胶的耐屈挠疲劳性能基本不变;与芳烃油增塑的NR/BR体系相比,LIR增塑NR/BR体系的耐屈挠疲劳性能较优,压缩疲劳生热和压缩永久变形较低;加入LIR降低了硫化胶滚动阻力的同时减弱了其抗湿滑性。     

Improving the properties of polylactic acid by blending with low molecular weight polylactic acid‐g‐natural rubber

The low molecular weight (M_w) polylactic acid‐g‐natural rubber (PLA‐g‐NR) was synthesized by grafting the maleated natural rubber (MNR) with low molecular weight PLA at a weight ratio of 1:1 in toluene at 80°C. Two types of MNR (MNR10 and MNR20) having anhydride moieties of 10 and 20 wt%, respectively, were prepared. The reaction was followed by IR analysis. Next, the obtained PLA‐g‐NR was blended with pristine PLA using a twin‐screw extruder at PLA to PLA‐g‐NR weight ratios of 90:10, 80:20, 70:30, and 60:40 followed by compression to obtain specimens for testing. In case of 10 wt% PLA‐g‐NR having MNR10, it was found that blending of PLA with PLA‐g‐NR resulted in a 200% improvement in impact strength and twofold percent elongation at break (flexibility). Further SEM analysis confirmed that PLA‐g‐NR was compatible with PLA matrix. In contrast, NR was present as disperse particles which exhibited poor adhesion to PLA. From these findings, it was also found that PLA‐g‐NR was capable of improving the properties of PLA more than NR due to the fact that it exhibited higher compatibility. POLYM. ENG. SCI., 54:2770–2776, 2014. © 2013 Society of Plastics Engineers     

Performance enhancement of polylactide by nanoblending with POSS and graphene oxide

We report the effect of filler modification on the properties of polylactide (PLA)‐based nanocomposites, where graphene oxide (GO) nanosheets and polyhedral oligomeric silsesquioxane (POSS) nanocages are employed as nanofillers. The organically treated nanofillers are termed as GO‐functionalized and POSS‐functionalized. The synthesis of the nanocomposites was carried out via in situ ring‐opening polymerization of lactic acid (LA). The following four naocomposite systems were prepared, characterized, and compared to achieve a better understanding of structure‐property relationship (1) PLA/GO‐functionalized, (2) PLA/POSS‐functionalized, (3) PLA/physical mixture of GO‐functionalized and POSS‐functionalized, and (4) PLA/GO‐graft‐POSS (with eight hydroxyl groups). As revealed by the thermal and mechanical (nanoindendation) characterization, that the nanocomposites having a combination of GO and POSS as nanofiller, either as physical mixture of GO‐functionalized and POSS‐functionalized or as GO‐graft‐POSS, is far more superior as compared with the nanocomposites having individually dispersed nanofillers in the PLA matrix. Observed enhancement is attributing to the synergistic effect of the nanofillers as well as better dispersion of the modified‐fillers in the matrix. POLYM. COMPOS., 35:118–126, 2014. © 2013 Society of Plastics Engineers     

液体聚异戊二烯的结构表征

通过傅立叶变换红外光谱、核磁共振、不饱和度测定、凝胶渗透色谱、热重分析和动态流变分析等手段对液体聚异戊二烯（LIR-50）的结构及其基本性质进行了研究.结果表明,LIR-50的链节化学组成与天然橡胶完全相同,但二者的空间结构有明显区别.LIR-50的顺-1,4、反-1,4和3,4结构含量分别为70.8%、24.4%、4.8%,而天然橡胶的顺-1,4结构高达98%.LIR-50的数均分子量为42000,多分散指数为1.24,其动态粘度对温度敏感,对剪切速率不敏感.     

Cellulose fiber‐reinforced polylactic acid

Polymer composites from polylactic acid (PLA) and two types of cellulose fibers obtained either by acid hydrolysis of microcrystalline cellulose (HMCC) or by mechanical disintegration of regenerated wood fibers (MF) were prepared and characterized. To enhance the compatibility of the cellulose fibers with PLA matrix, a surface treatment based on 3‐aminopropyltriethoxysilane (APS) was performed. The Fourier Transform Infrared (FTIR) spectroscopy was used to determine the chemical groups involved in the surface modification reaction. The silanization treatment resulted in different modifications on both types of cellulose fibers because of their different structural and morphological characteristics. The composites were prepared by incorporating 2.5% of the treated or untreated HMCC and MF into a PLA matrix using a melt‐compounding technique. An improved adhesion between the two phases of the composite materials was observed by scanning electron microscopy thanks to treatment. The dynamic mechanical thermal analyses showed that both untreated and silane treated fibers led to an improvement of the storage modulus of PLA in the glassy state. A higher enhancement of the storage modulus in the case of PLA/HMCC composites than the composites containing MF was obtained as a result of the high aspect ratio of these fibers which allows better matrix‐to‐filler stress transfer. Furthermore, the storage modulus of PLA composites was enhanced by silanization even at higher temperatures especially after thermal treatment. The cellulose fibers addition in PLA matrix modified significantly the relaxation phenomenon as observed in tan δ curves, emphasizing strongly modified molecular mobility of PLA macromolecules and crystallization changes. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.     

Basalt fiber reinforced and elastomer toughened polylactide composites: Mechanical properties,rheology, crystallization,and morphology

A series of the reinforced and toughened polylactide (PLA) composites with different content of basalt fibers (BF) were prepared by twin screw extruder. The toughness of BF/PLA composite s was improved further by the addition of polyoxyethylene grafted with maleic anhydride (POE-g-MAH), ethylene–propylene–diene rubber grafted with maleic anhydride (EPDM-g-MAH), and ethylene-acrylate-glycidyl methacrylate copolymer (EAGMA), relatively. The mechanical properties, rheology, crystallization, and morphology of BF/PLA composites were studied. The results showed that basalt fiber had significant reinforcing and toughening effect in comparsion with glass fiber. EAGMA was more effective in toughening BF/PLA composites than POE-g-MAH and EPDM-g-MAH. When the content of EAGMA achieved to 20 wt %, the impact strength of BF/PLA/EAGMA composite increased to 33.7 KJ/m², meanwhile the value was improved by 71.1% compared with pure PLA. According to dynamic rheometer testing, the use of the three kinds of elastomers increased the melt dynamic viscosity. Differential scanning calorimetry analysis showed that POE-g-MAH and EPDM-g-MAH can decrease the cold crystallization temperature (T_cc) to approximately 20°C and dramatically improve crystallinity (χ_c) of BF/PLA composites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology and rheology relationships of epoxy/core‐shell particle blends

The morphological and rheological behaviors of toughened epoxy resins modified with core‐shell rubber particles (CSR) were studied. These rubber particles were based on a poly (butadiene‐co‐styrene) core and a crosslinked poly (methyl methacrylate) shell. The effect of functionalized groups was performed on two types of CSR particles: first, those containing carboxyl‐functionalized groups (CSf), and second, particles containing no carboxyl‐functionalized groups (CSnf) in the PMMA‐shell. For these blends, the correlations between the morphology, particle dispersion state and their rheological behaviors before curing were investigated. Preliminary work using TEM micrographs indicated that the blends modified with CSf and CSnf exhibited the same particle size but differed with respect to the dispersion state. Rheological behavior of these blends was assessed in steady shear flow and dynamic viscoelastic experiments. Yield viscosity near‐zero shear rate occurred in the DGEBA/CSf blend presenting non‐Newtonian behavior at the particle volume fraction of 20% vol. The rheological behavior was clearly related to the state of particle dispersion and analyzed taking into account interactions between the particles‐particles and the particles‐matrix. The Williams‐Landel‐Ferry (WLF) shift procedure was used to construct modulus master curves G′ and G″ from the elastic solid state to molten polymers. A secondary plateau existed at low frequencies and was related to the presence of interactions leading to a physical network‐type structure. The deviation between theoretical G′ (Paleirne's model) and experimental G′ values was evaluated and exhibited high elasticity at the terminal zone, which correlated well with available literature.     

Wetting behavior of functionalized silicone and EPDM rubber

The contact angles and surface energies have been determined for silicone rubber functionalized with amide group and EPDM rubber modified with sulfonic acid and maleic anhydride. The functionalization of the polymers decreases the equilibrium contact angles of water and formamide with an increase in the surface energy. The changes in the surface properties are due to the changes in the concentration of the polar groups as measured by IR spectroscopy. The lap shear measurement on joints of silicone and EPDM rubber indicates an increased strength on modification. © 1996 John Wiley & Sons, Inc.     

Development of plasticized PLA/NH2‐CNTs nanocomposite: potential of NH2‐CNTs to improve electroactive shape memory properties

A polymer nanocomposite system comprising epoxidized soya oil plasticized‐polylactic acid (PLA) and amine functionalized carbon nanotubes (NH₂ functionalized‐CNTs) has been prepared with the aim of producing electrically conductive PLA products suitable for shape memory (SM) applications. An influence of the addition of NH₂ functionalized‐CNTs on thermal, mechanical properties, and morphology development of plasticized PLA/NH₂ functionalized‐CNTs nanocomposite was investigated by differential scanning calorimetry, tensile tests, scanning electron microscope, and atomic force microscopy, respectively. In addition, electroactive SM behavior in resulting nanocomposite was evaluated by a bending test, and the recovery process was recorded with video camera. The results showed that SM behavior in nanocomposite was influenced by NH₂ functionalized‐CNTs weight percent in matrix. Nanocomposite with 5 wt% NH₂ functionalized‐CNTs showed optimum values of shape recovery due to its relatively high electrical conductivity, and an adequate degree of crosslinking between NH₂ functionalized‐CNTs and plasticized PLA matrix. However, more than 5 wt% loading of NH₂ functionalized‐CNTs dropped down an elongation at break, while tensile at break increased with the increasing of CNTs weight percent in matrix. Interesting point in this study is that all improvements in the properties of resulting PLA/NH₂ functionalized‐CNTs nanocomposite sheet were observed at very low filler content, while other literature reports where large quantities of CNTs were used. POLYM. COMPOS., 35:2129–2136, 2014. © 2014 Society of Plastics Engineers     

Melt processing of biodegradable poly(lactic acid)/functionalized chitosan nanocomposite films: mechanical modeling with improved oxygen barrier and thermal properties

The present work demonstrates about the formulation of functionalized chitosan (CH-g-OLLA) through the transformation of hydrophilic nature of chitosan into hydrophobic by grafting with oligo(L-lactic acid) (OLLA). The developed CH-g-OLLA is easily soluble in poly(lactic acid) (PLA) matrix, which provides an opportunity towards producing industrially viable nanocomposite films for stringent food packaging and beverages applications. The grafting of OLLA chains is confirmed at NH₂ group of chitosan through the presence of two new peaks at 4.2 and 5.1 ppm in ¹H–NMR spectra. Various parameters like yield (%), grafting efficiency (%) and percent grafting (%) are calculated as ~51.6, ~40 and ~150%, respectively. Functionalized chitosan has been utilized as nano-filler in PLA matrix to fabricate PLA/CH-g-OLLA nanocomposite films which have compounded successfully by co-rotating twin screw compounder cum cast film extrusion technique (distinctly advantageous over conventional solution casting) at bench scale as well as semi-pilot scale and further demonstrated for its application in the area of food packaging with tailored oxygen barrier properties. Uniform dispersion of spherical aggregates of functionalized chitosan is observed in PLA/CH-g-OLLA nanocomposite films using TEM analysis. A significant reduction up to ~11 °C in glass transition temperature of PLA is observed by adding 5 wt% of nano-filler as a result of plasticization effect, which is an essential property in designing of flexible packages. Mechanical modeling of extruded PLA/CH-g-OLLA films has been performed to compare the experimental values with theoretical results using various mathematical models in which modified foam model, Nielsen model and modified Mitsuishi model demonstrate the best match for Young’s modulus (±0.08), tensile strength (±0.06) and percentage elongation (±0.03), respectively. This may be a significant contribution towards commercialization of such formulation where elegant melt extrusion process of PLA with functionalized chitosan is capable of reducing oxygen permeability up to ~10 folds due to a drastic reduction (~96%) in oxygen solubility.     

Effect of modified rubber powder on the morphology and thermal and mechanical properties of blown poly(lactic acid)–hydroxyl epoxidized natural rubber films for flexible film packaging

In this study, we prepared and used modified natural rubber powder to increase the toughness of poly(lactic acid) (PLA) films. We blended PLA and hydroxyl epoxidized natural rubber (HENR) via a melt-mixing process with twin-screw extruder and a blowing machine. We investigated the influence of the HENR content in the blend films on the microstructure, thermal, mechanical, and optical properties. The morphology of the blend showed a coarse surface and elongated fibrils of HENR in the PLA matrix. After blowing, the dispersion of small particles of HENR in the substrate was seen. The size of the remaining HENR particles was smaller than that of the starting powder. The compatibility of HENR and the remaining rubber particles may have synergistically contributed to improvements in the elongation at break, impact strength, and ultraviolet–visible transition protection of the PLA films. The elongation at break drastically increased from 3 to 228% after PLA was blended with 20 wt % HENR. On the other hand, all of the blends exhibited lower glass-transition temperatures and cold crystallization temperatures than the pure PLA films. We concluded that the blend was partially compatible and may have increased the flexibility of the PLA films. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47503.     

Thermal stability of modified end‐capped poly(lactic acid)

The influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l ‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l ‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41105.     

液体异戊橡胶作为顺丁橡胶反应型增塑剂的研究

研究了自制聚异戊二烯橡胶(LIR)、LIR-50对顺丁橡胶(BR)结构与性能的影响,并与传统增塑剂石蜡油作对比。结果表明：LIR和传统增塑剂石蜡油均能有效改善BR的加工性能,后者的增塑效果稍好;与石蜡油相比,LIR几乎完全参与硫化,是一种反应型增塑剂;LIR填充胶料的硫化胶具有较低的抽提率及稳定的物理机械性能;自制LIR和LIR-50使用效果相当。     

滑石粉、氧化锌柱撑有机皂石复合填料对聚乳酸结晶及性能的影响

以改性滑石粉与氧化锌柱撑有机皂石为添加助剂,通过溶液插层法制备了聚乳酸基纳米复合材料。研究了该复合材料的微观结构、热性能及力学性能。结果表明,滑石粉层间距被增大,硅烷偶联剂（KH570）被有效包覆在滑石粉片层表面;添加0.3份氧化锌柱撑有机皂石时,聚乳酸复合材料的拉伸强度达到40.3MPa,比纯聚乳酸增加了约140.9%;改性滑石粉与氧化锌柱撑有机皂在聚乳酸基中起到了良好的异相成核作用,氧化锌柱撑有机皂石含量为0.3份时复合材料的结晶度与纯聚乳酸提高了87.0%,热分解温度提高了7.07oC。