Structure evolution of bio-based PLA/ENR thermoplastic vulcanizates during dynamic vulcanization processing

The thermoplastic vulcanizates (TPVs) of Polylactide (PLA)/Epoxidized natural rubber (ENR) were prepared by dynamic vulcanization technology. The processing torque, crosslink density, morphology of PLA/ENR blends, and PLA's molecular weight during the processing were investigated by HAAKE rheometer, swelling measurement, scanning electron microscopy (SEM), and gel permeation chromatography (GPC). It was found that the vulcanization of ENR completed at the turning point after torque peak. After the turning point, the torque and crosslink density decreased with the processing time increasing. Moreover, the morphology of PLA/ENR blends showed bi-continuous structure during the dynamic vulcanization processing, and the phase size of PLA/ENR was increased with processing time and temperature. GPC results showed PLA degradation mainly happened after torque turning point. Thermal gravimetric analysis (TGA) results indicated that some parts of PLA would graft on ENR during processing, and the higher the processing temperature, the more the PLA was grafted.     

Bio-based polylactide/epoxidized natural rubber thermoplastic vulcanizates with a co-continuous phase structure

A bio-based thermoplastic vulcanizate (TPV) composed of polylactide (PLA) and epoxidized natural rubber (ENR) was fabricated through dicumyl peroxide-induced dynamic vulcanization. It was found that the crosslinked ENR phase had a specific continuous structure, hence forming a bi-continuous structure in the TPV. We designed cyclic stress-strain, stress-soften and stress-relaxation tests and SEM observation to reveal the relationship between the PLA continuous phase and crosslinked ENR continuous phase. It was found that the PLA phase generated crazes to adapt the elongation of the ENR continuous phase during stretching. At the same time, the enhanced interface between PLA and ENR kept the stress transferring between the two phases. The ENR with more epoxy groups showed better compatibility with PLA, which resulted in better mechanical properties.     

Tough crystalline blends of polylactide with block copolymers of ethylene glycol and propylene glycol

The effect of crystallinity of polylactide (PLA) on the structure and properties of tough PLA blends with PEG-b-PPG-b-PEG block copolymers was studied. PLA was melt blended with a set of the copolymers with varying ratio of the hydrophilic (PEG) and hydrophobic (PPG) blocks. Although the blend phase structure depended on the copolymer molar mass and PEG content, as well as on the copolymer concentration in the blend, crystallinity also played an important role, increasing the copolymer content in the amorphous phase and enhancing phase separation. The influence of crystallinity on the thermal and mechanical properties of the blends depended on the copolymer used and its content. The blends, with PLA crystallinity of 25 ÷ 34 wt%, exhibited relatively high glass transition temperature ranging from 45 to 52 °C, and melting beginning above 120 °C. Although with a few exceptions crystallinity worsened the drawability and toughness, these properties were improved with respect to neat crystalline PLA in the case of partially miscible blends, in which fine liquid inclusions of the modifier were dispersed in PLA rich matrix. About 20-fold increase of the elongation at break and about 4-fold increase of the tensile impact strength were reached at a small content (10 wt%) of the modifier. Moreover, crystallinity decreased oxygen and water vapor transmission rates through neat PLA and the blend, and the barrier property for oxygen of the latter was better than that of neat polymer.     

Preparation of body-temperature-triggered shape-memory polyurethane with biocompatibility using isosorbide and castor oil

Shape memory polyurethanes (SMPUs) have attracted much attention in the biomedical field because they can easily control the transition temperature (T_trans) to shape memory and are biocompatible. In this study, a shape memory polyurethane with both biocompatibility and a T_trans close to the body temperature was synthesized by using natural derivatives of isosorbide and castor oil in place of petroleum-based materials. Isosorbide and castor oil were used to form net points, and polycaprolactone diol (PCL diol) acted as the switching segment. The synthesized four polyurethane (PCL diol/isosorbide/castor oil, PICU-1, 2, 3, 4) with different isosorbide contents exhibited desired thermal and mechanical properties. In the thermo-cyclic shape memory testing experiment, the PICU series demonstrated good shape memory property, with more than 95% shape recovery ratio (R_r) and more than 90% shape fixity ratio (R_f), and PICU-3 recovered its shape within 20 s in a 37 °C water bath. In addition, the PICU series proved to be safe materials with excellent biocompatibility, as indicated by the observed C2C12 cells viability and proliferation. The stent made with the PICU-3 film showed near complete magnetization at 37 °C within 18 s and proved to be a suitable self-expanding stent.     

Tough and transparent blends of polylactide with block copolymers of ethylene glycol and propylene glycol

In order to modify its physical properties, particularly the drawability and toughness, polylactide (PLA) was melt blended with a set of PEG-b-PPG-b-PEG block copolymers with varying ratio of the hydrophilic (PEG) and hydrophobic (PPG) blocks. Miscibility of the copolymers with PLA depended on their molar mass and PEG content. Interestingly, the best drawability was achieved in the case of partially miscible blends, in which fine liquid inclusions of the modifier were dispersed in PLA rich matrix with glass transition temperature only moderately decreased, to about 50 °C. About 37 fold increase of the elongation at break and about 1.5 fold increase of the tensile impact strength with respect to neat PLA were reached at small content (10 wt.%) of the modifier. Despite the phase separation, the blends remained transparent. In addition, the barrier properties for oxygen were improved.     

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials.     

Detailed molecular characterization of castor oil ethoxylates by liquid chromatography multistage mass spectrometry

The molecular characterization of castor oil ethoxylates (CASEOs) was studied by reverse-phase liquid chromatography (RPLC) mass spectrometry (MS) and multistage mass spectrometry (MS(n)). The developed RPLC method allowed the separation of the various CASEO components, and especially, the baseline separation of multiple nominal isobars (same nominal mass) and isomers (same exact mass). MS and MS(n) were used for the determination and structure elucidation of various structures and for the discrimination of the isobars and isomers. Different ionization techniques and adduct ions were also tested for optimization of the MS detection and the MS(n) fragmentation. A unique fragmentation pathway of ricinoleic acid is proposed, which can be used as a marker of the polymerization process and the topology of ethoxylation in the CASEO. In addition, characteristic neutral losses of ricinoleic acid reveal its (terminal or internal) position in the molecule.     

Synthesis, characterization, degradation of biodegradable castor oil based polyesters

A new family of castor oil based biodegradable polyesters was synthesized by catalyst free melt condensation reaction between two different diacids and castor oil with d-mannitol. The polymers synthesized were characterized by NMR spectroscopy, FT-IR and the thermal properties were analysed by DSC. The results of DSC show that the polymer is rubbery in physiological conditions. The contact angle measurement and hydration test results indicate that the surface of the polymer is hydrophilic. The mechanical properties, evaluated in the tensile mode, shows that the polymer has characteristics of a soft material. In vitro degradation of polymer in PBS solution carried out at physiological conditions indicates that the degradation goes to completion within 21 days and it was also found that the rate of degradation can be tuned by varying the curing conditions.     

橡胶增韧塑料机理

综述了橡胶增韧塑料机理研究的发展与现状,着重探讨了橡增韧机理中有关脆韧转变的定量研究,同时也讨论了分散相的形态参数、界面相容性和韧性测试条件以及分散相与基体的性能等因素对橡胶增韧塑料性能及增韧的影响,最后提出了橡胶增韧塑料研究的发展趋势。     

Pyrolysis of vegetable oil soaps—Palm, olive, rapeseed and castor oils

Saponified, palm, olive, rapeseed and castor oils were pyrolysed (at 750 °C for 20 s) by pyrolysis gas chromatography with mass selective and flame ionisation detection (Py-GC/MSD and FID) to clarify their thermochemical behaviours. The liquefiable compounds recovered from palm, olive and rapeseed oils mainly contained linear alkenes (up to C₁₉) and alkanes (up to C₁₇), both similar to those found in gasoline (C₄-C₁₀) and diesel fuel (C₁₁-C₂₂) boiling range fractions of petroleum, whereas in the case of castor oil a significant amount of undesired oxygen-containing products (e.g., ketones and phenols) were formed. The obtained data on reaction mechanisms can also be utilised in applications where various biofuels are produced, for example, from the extractive-derived by-product (tall oil) of kraft pulping.     

Optimization of gas chromatographic-mass spectrometric analysis for fatty acids in hydrogenated castor oil obtained by catalytic transfer hydrogenation

Optimization of the analytical conditions for determination of the partially hydrogenated products of castor oil obtained by catalytic hydrogen transfer, using Pd/C, with limonene as hydrogen source, was carried out in this work. The study involved the use of three capillary columns: SPB-1, HP-5 and HP-20 M. The best resolution for the oleic acids isomers, C18:1, was obtained with HP-20 M column while, the best resolution, identification and quantification for the products containing OH and CO were obtained with a HP-5 column after the silylation of the methyl esters.     

Preparation of polypropylene/ethylene‐propylene‐diene terpolymer/nitrile rubber ternary thermoplastics vulcanizates with good mechanical properties and oil resistance by core‐shell dynamic vulcanization

As the most successful commercialized thermoplastic vulcanizates (TPVs), polypropylene (PP)/ethylene propylene rubber (EPDM) TPVs exhibit poor oil resistance. In this work, we prepared PP/EPDM/butadiene acrylonitrile rubber (NBR) ternary TPVs with good oil resistance using core‐shell dynamic vulcanization. According to the theoretical analysis of the spreading coefficient and the transmission electron microscopy results, the rubber phases exhibited a special core‐shell structure, in which the cross‐linkedNBR‐core was encapsulated by the EPDM‐shell. The core‐shell structure effectively improved the interfacial compatibility between PP and NBR phase as the EPDM‐shell could avoid the direct contact of them, thus improving the mechanical properties of the TPVs. For example, the PP/EPDM/NBR (40/30/30) ternary TPV showed enhanced tensile strength of 12.57 MPa, compared with 10.71 MPa of PP/EPDM (40/60) TPV and 11.11 MPa of PP/NBR (40/60) TPV, respectively. Moreover, the oil resistance of the TPVs was also improved. Compared with PP/EPDM TPV, the change rates in mass, volume, tensile strength and elongation at break of PP/EPDM/NBR TPV after oil immersion decreased by 42.18%, 48.69%, 52.68% and 28.77%, respectively.     

Recycling of waste poly(ethylene terephthalate) with castor oil using microwave heating

The chemical recycling of waste poly(ethylene terephthalate) (PET) using castor oil (CO) as a reagent is reported. CO presents a renewable alternative to petrochemical based reagents, e.g. glycols, and enables also substantial modification of final physico-chemical properties of a received product. Advantageously, microwave irradiation was used to accelerate the depolymerization of PET. A composition of obtained product was strongly influenced by the reaction temperature. When the decomposition of PET was performed at temperature higher than 240 °C, then a significant extent of side products based on PET oligomers and transesterified CO was observed due to dehydration and hydrolysis of CO. Contrary to that, PET decomposition took place at slow rate below 230 °C and the optimal reaction temperature lies in the relatively narrow interval from 230 °C to 240 °C. The product prepared in the optimal temperature range did not contain any high molecular weight PET oligomers. MALDI-TOF mass spectrometry enabled to identify the structures included in the obtained polyol product. The maximum number of six repeating monomeric unit of PET was found in the product, which confirmed practically the complete depolymerization of PET chain and good reactivity of the acylester hydroxyl groups of CO.     

Synthesis and properties of isocyanate curable millable polyurethane elastomers based on castor oil as a renewable resource polyol

Millable polyurethane elastomers based on difunctional castor oil and poly(propylene glycol), 2,4-toluene diisocyanate and 1,4-butane diol were prepared and cured using toluene diisocyanate dimer as crosslinking agent. All elastomers were characterized by conventional methods. Physical, thermal and mechanical properties of elastomers were studied. Investigation of these properties showed that the elastomers could be tailor made in order to fulfill industrial needs.     

Room temperature synthesis and mechanical properties of two kinds of elastomeric interpenetrating polymer networks based on castor oil

Two kinds of interpenetrating polymer networks (IPNs) composed of two-component polyurethane (PU) and vinyl or methacrylic polymer (PV), namely, (polyether-castor oil)PU/PV IPN(I) and (polybutadiene-castor oil)PU/PV IPN(II), were synthesized at room temperature using benzoyl peroxide and N,N-dimethylaniline as redox initiator and dibutyltin dilaurate as catalyst. The former IPN was prepared by polymerization of castor oil, NCO-terminated polyether and vinyl or methacrylic monomer together and the latter IPN was obtained by polymerization of castor oil, NCO-terminated polybutadiene, NCO-terminated castor oil and vinyl or methacrylic monomer together. Various synthesis conditions affecting mechanical properties of the two kinds of IPNs were studied. Acrylonitrile (AN) is a good monomer for synthesizing IPN(I), but is a poor monomer for preparing IPN(II). At optimum conditions for the synthesis, both the (polyether-castor oil)PU/PAN IPNs and the (polybutadiene-castor oil)PU/polystyrene (PSt) IPNs possess permanent set about 10%, tensile strength over 13 and 11 MPa and ultimate elongation over 240% and 270%, respectively, thus behaving as elastomers. TEM micrograph of a (polybutadiene-castor oil)PU/PSt IPN showed a microphase separation in the IPN.     

Synthesis of environmental benign biolubricant from wild castor seed by reactive extraction and optimization

Castor oil alkyl esters are a possible biolubricant since they contain 90% hydroxyl fatty acid, which improves the oil's lubricity. Due to the limitations of the conventional approach, castor oil propyl ester (COPE) from wild castor seed was synthesized by reactive extraction. The factors influencing yield of reaction was optimised by response surface methodology to obtain a high yield. The influence of amount of catalyst, propanol to oil proportion, temperature, and rotating speed on castor oil propyl ester yield was investigated using a central composite design.The optimised reaction condition is propanol to oil molar proportion of 275: 1 with 1.5 wt% of catalyst loading at 90 °C and rotating speed of 450 rpm with COPE yield of 78.6% in 3hrs. Physico-chemical properties of alkyl esters were determined. COPE can be employed as a bioadditive to ultra-low sulphur diesel fuels due to its high lubricity.     

Modification of Polylactic Acid by Reactive Blending with Functionalized Imidazolium-based Ionomers and Epoxy-containing Additives北大核心CSCD

Aiming to tackle the serious brittleness problem of polylactic acid（PLA）,PLA-based multiphase blends are prepared by melting reactive blending with hydroxyl functionalized ionomer as the toughening agent and compatibilizer containing epoxy groups. The structures and properties of the blends are characterized by scanning electron microscopy（SEM）,Fourier transform infrared spectrometer（FT-IR）,differential scanning calorimetry（DSC）and mechanical properties tests. The synergistic compatibilization and toughening effects of epoxy soybean oil （ESO）,polyethylene glycol diglycidyl ether （PEGDE）and ethylene-methyl acrylate-glycidyl methacrylate （AX8900） terpolymer are compared and analyzed. The results show that the compatibilization effect is closely related to the content and position of the epoxy group in the additives,which presenting different toughening effects. The addition of AX8900 can effectively improve the toughness of the blend system to obtain balanced mechanical properties. However,ESO tends to lead to crosslinking,which limits the toughening efficiency. PEGDE mainly shows a plasticizing effect,leading to the reduction of tensile strength. The results demonstrate modification of the PLA blends by reactive blending with different epoxy additives and hydroxy-containing polymers is an effective strategy for the development of high-performance biobased PLA materials. © 2022, Science Press (China). All rights reserved.     

Ternary blends based on poly (ethylene-naphthalate)/glass fibers/nitrile rubber: Preparation,properties and effect of dynamic vulcanization

This work studied the possibility of utilizing nitrile rubber (NBR) to modify the impact properties of poly (ethylene-naphthalate) (PEN). The PEN/NBR ratio used changed from 100/0 to 60/40. At the same time, glass fibers (GF), 40% weight of the PEN component, were used to reinforce the blends to compensate for the loss of mechanical properties of PEN by incorporation of NBR. The results showed that the impact strength of the PEN/GF/NBR blend (PEN/NBR = 60/40) was increased up to 27.6J/m, nearly 5 times higher than that of the neat PEN. Meanwhile, the tensile strength and flexural strength were still maintained at as high as 66.1 MPa and 98.2 MPa, respectively. Dynamic vulcanization further improved the mechanical properties of the PEN/GF/NBR blends, which provided routes to the design of new PEN/elastomer blends. Other properties of the PEN/GF/NBR blends were also investigated in terms of morphology of fractured surface, dynamic mechanical behavior, thermal stability and crystallization, by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.     

Dynamic vulcanization of reclaimed tire rubber and high density polyethylene blends

Dynamic vulcanization of reclaimed tire rubber (RTR) and HDPE blends was reported. The effect of blend ratio, methods of vulcanization, i.e. sulphur, peroxide, and mixed system and the addition of compatibilizer on mechanical, thermal, and rheological properties were investigated. The blend with highest impact strength was obtained from 50/50 RTR/HDPE vulcanized by sulphur. Increasing the RTR content to more than 50% resulted in a decrease in the impact strength of blend, most likely due to the increasing carbon black content. For tensile strength, the presence of rubber and carbon black, however, unavoidably caused a drop in this property. Comparing among three methods of vulcanization, sulphur system seems to be the most effective method. Results from solvent swelling ratio, glass transition temperatures and viscosity indicated that the sulphur vulcanization created the highest degree of cross-link and filler-matrix interaction in the RTR/HDPE blend. Morphology of the blends was also assessed by scanning electron microscopy (SEM).     

Microstructure and properties of polyurethanes derived from castor oil

The goal of this work was the synthesis of novel segmented polyurethanes with a high percentage of components derived from renewable sources. The soft segment was a polyol derived from castor oil and the hard segment structure was varied by means of different chain extenders, petrochemical-based 1,4-butanediol (BD) and corn sugar-based 1,3-propanediol (PD). The synthesis was carried out in bulk and without catalyst via a two-step polymerization varying hard segment ratio. Physico-chemical, mechanical and morphological characterization was performed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), atomic force microscopy (AFM), mechanical testing and termogravimetric analysis (TGA). Properties have been discussed from the viewpoint of hard/soft microdomain phase separation and also the hard segment nature and formed structure. An increase in hard segment content was accompanied by an increase in hard domain order, crystallinity, and stiffness. The hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to impart properties ranging from elastomeric to rigid behaviour with the increase of hard segment content. Polyurethanes synthesized from bio-based chain extender showed a slightly lower crystallinity in the hard segment structure than that synthesized from BD as the chain extender. This lower crystallinity avoids strength concentrations at the soft/crystalline hard segment interface, thus improving the mechanical properties at high hard segment content. The slightly higher thermal stability observed for BD based polyurethanes is related with their more packed structures and crystallinity observed in the hard segment structure.