New reactive additives for interface modification in multicomponent polyolefin systems

New reactive additives were synthesised and used as interface modifiers in different multicomponent polyolefine systems. The synthesis was carried out in computer‐controlled reactor by means of Diels‐Alder reaction and condensation. These additives are capable of combining the benefits of dispersing and coupling agents. A part of the synthesised reactive surfactants have also synergistic effect in flame retardant systems. Their surface‐active character facilitates the reactive compounding. The undesirable transport processes of stabilisers and components of flame‐retardants in polyolefine systems could be effectively controlled by interface modification.     

Influence of molecular weight and free NCO content on the rheological properties of lithium lubricating greases modified with NCO-terminated prepolymers

In this work, the use of reactive diisocyanate-terminated polymeric materials as rheology modifiers of lubricating greases has been studied. Particularly, the influences that free NCO content, molecular weight and functionality of the reactive prepolymers exert on the rheological response and microstructure of lubricating greases were analyzed. With this aim, NCO-terminated prepolymers were prepared from several di and trifunctional polyols and polymeric MDI. Afterwards, the reaction between terminal isocyanate groups and the hydroxy group located in the hydrocarbon chain of the 12-hydroxystearate lithium soap, used as thickener, was promoted during processing of lubricating greases. Polymeric materials used as additives and final lubricating greases were characterized by FTIR, DSC and GPC techniques. The effectiveness of these reactive additives was tested by performing small-amplitude oscillatory shear (SAOS), as well as standardized mechanical stability tests, on final greases. The rheological response was related to the microstructure of these greases, characterized by means of atomic force microscopy (AFM). From the experimental results obtained, it may be concluded that the effectiveness of these polymeric additives to modify the rheology of greases is due to the progress of the reaction between terminal isocyanate groups and the hydroxy group of lithium soap. However, a large dependence on both free NCO content and prepolymer molecular weight was found. Experimental results confirm that a balance between prepolymer molecular weight and NCO content is necessary to reach an optimal rheological modification of lithium greases. Moreover, this balance is a function of grease ageing, due to the progress of the reaction promoted.     

PET/R‐PP/PC blends by two‐stage reactive extrusion: effect of polypropylene reactively functionalized with an oxazoline group on morphology and mechanical properties

A series of PET/R‐PP/PC blends was studied in a chemical modification involving reactive extrusion with a ricinyl‐2‐oxazoline maleinate. The interfacial reaction between blend components were studied by the differential scanning calorimetry (DSC) and the scanning electron microscopy (SEM). The static tensile and flexural properties, and impact resistance response of the blends were tested. The phase morphology of the blends was of interpenetrating network (IPN) type according to SEM results. The blends offer excellent mechanical properties and improved impact strength as an effect of chemical reactions on reactive extrusion, even if PET waste and low PC contents (below 20%) have been used.     

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.     

Mechanical properties of rigid polyurethane composites reinforced with surface treated ultrahigh molecular weight polyethylene fibers

The mechanical properties of ultrahigh molecular weight polyethylene (UHMWPE) fibers reinforced rigid polyurethane (PU) composites were studied, and the effects of the fiber surface treatment and the mass fraction were discussed. Chromic acid was used to treat the UHMWPE fibers, and polyurethane composites were prepared with 0.1 to 0.6 wt% as‐received and treated UHMWPE fibers. Attenuated total reflection Fourier transform infrared demonstrated that oxygen‐containing functional groups were efficiently grafted to the fiber surface. The mechanical performance tests of the UHMWPE fibers/PU composites were conducted, and the results revealed that the treated UHMWPE fibers/PU composites had better tensile, compression, and bending properties than as‐received UHMWPE fibers/PU composites. Thermal gravimetric analyzer showed that the thermal stability of the treated fiber composites were improved. The interface bonding of PU composites were investigated by scanning electron microscopy and dynamic mechanical analysis, and the results indicated that the surface modification of UHMWPE fiber could improve the interaction between fiber and PU, which played a positive role in mechanical properties of composites.     

Gelation dynamics and gel structure of fibrinogen

Gelation dynamics and gel structure of fibrinogen induced by serine protease, thrombin, was investigated by light scattering, real space observation using confocal laser scanning microscopy (CLSM), and turbidity. Effects of additives, such as (linear) saccharides, glucose to dextran, and cyclodextrin, were studied focusing on the interaction with fibrin(ogen) and thrombin. Light scattering measurement was ascertained to be able to characterize the gelation process and growth kinetics. Stepwise (two-step) gelation process, formation of fibrin monomers and protofibrils followed by the lateral aggregation to form fibrin fibers and gel network, was clearly ascertained. Gelation point could be characterized quantitatively. At the gelation point, dynamic light scattering exhibited a self-similar nature of the fibrin gel network, and the fractal dimension was evaluated in good accordance with the reconstructed 3D image of gel network by CLSM. The interaction between the additives and fibrin(ogen) and thrombin were studied by the inhibition test using synthesized substrate. Temporal variation of microstructure of fibrin gel network (lateral fiber growth) was investigated by turbidity in detail. Addition of saccharides affects significantly the network formation as revealed by turbidity. The interaction of dextran with fibrin fibers was examined by fluorescence microscopy, too, and the characteristic spatial distribution was observed.     

Adsorption properties for metal ions of waste poly(p‐phenylene terephthalamide) fiber after chemical modification

Waste poly(p‐phenylene terephthalamide) fibers (PPTA) were chemically modified through nitration and nitro‐reduction reactions to obtain nitro‐ and amino‐containing fibers and used as adsorbents for metal ions. The structures of the modified fibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X‐ray diffraction (XRD), and thermogravimetric (TG) analysis. Metal ions, such as Ni²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, were used to determine the adsorption capacities of the PPTA fibers before and after modification in aqueous solutions. The results showed that the modification improved the adsorption capability of fibers and extraction ratio of metal ions significantly. The adsorption mechanism of modified PPTA fibers for metal ions was proposed. The adsorption processes of Ni²⁺, Pb²⁺, and Cu²⁺ followed well a pseudosecond‐order model onto PPTA‐NH₂. The Langmuir and Freundlich models were employed to fit the isothermal adsorption. The results revealed that the linear Langmuir isotherm model is better‐fit model to predict the experimental data. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of properties of modified silicones at solid-liquid interface: fabric-silicone interactions

Silicones are special reagents that impart desired surface properties such as softness, bounciness and antiwrinkle properties to fabrics and related materials. Although these finishing processes have been practiced routinely, very little is known about the mechanisms involved in modification so that they could be improved. The current study was undertaken to develop basic understanding of the mechanisms responsible for surface modification of fibers using silicones. PDMS based amino silicone emulsions, quaternized to various degrees using dimethyl sulphate, were used in the present study. The electrokinetic properties of the modified silicones were studied as a function of pH. It was expected that the silicone emulsions would show a steady positive zeta potential throughout the pH range due to the quaternization by dimethyl sulphate. Surprisingly, a sudden drop in the zeta potential was observed around pH 8 with the samples turning hazy in the pH range of 8-10. Turbidimetric studies also showed a sudden increase in the turbidity in the pH range 8-10 where commercial processes also encounter problems. It was concluded that the emulsions were destabilized at pH 8-10 thus rendering them ineffective for surface treatment. In order to identify reason for the improvement in fabric properties, fiber structure was monitored using atomic force microscopy. It was observed that the treated fibers were far smoother, relaxed and uniform as compared to the untreated fibers. Thus the morphology of the fabric is modified in a specific way by treatment with specialty silicones.     

Improved interfacial properties of carbon fiber/UHMWPE composites through surface coating on carbon fiber surface

Carbon fibers were coated in an attempt to improve the interfacial properties between carbon fibers and ultra‐high molecular weight polyethylene resin matrix. Atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy were performed to characterize the changes of carbon fiber surface. Atomic force microscopy results show that the coating of carbon fiber significantly increased the carbon fiber surface roughness. X‐ray photoelectron spectroscopy indicates that silicon containing functional groups obviously increased after modification. Interlaminar shear strength was used to characterize the interfacial properties of the composites.     

Modification of membrane materials used in dried blood spot technology by zinc oxide nanoparticles

The modification of hydrophilic fiberglass and cellulose membrane materials with zinc oxide has been investigated. The surfaces of zinc oxide nanoparticles was hydrophilized by modification with 3-amino-propyltriethoxysilane. It was shown using methods of Fourier transform IR-spectroscopy and scanning electron microscopy that coating with hydrophilized zinc oxide nanoparticles did not change the structure of glass fibers and membrane material, while the treatment of cellulose-based membrane materials caused irreversible changes in the structure of fibers and the material as a whole.     

Novel palladium catalysts immobilized on functionalized chlorinated polyvinylchloride nanofiber mats

Well-defined chlorinated polyvinylchloride (CPVC) nanofiber mats were fabricated by electrospinning, and then chemically modified with 1,3-propanediamine (CPVC–NH) and glutaraldehyde (CPVC–NOH) to immobilize palladium active species. The chemical modification could significantly improve the tensile strengths of the CPVC nanofiber mats. Adsorption of Pd(II) ions showed that the treatment of fiber mats with glutaraldehyde decreases it schelating ability. Transmission electron microscopy and X-ray diffraction analysis indicated that palladium species were dispersed more homogeneously on the CPVC–NH fibers than on the CPVC–NOH fibers. Results of Mizoroki–Heck reaction showed that the catalytic activity of Pd catalyst supported on CPVC–NOH fibers was superior to that of the Pd catalyst supported on CPVC–NH fibers. Thus, chemical modification of supporting materials with suitable chelating groups is an efficient way to control the catalytic performance of supported Pd catalysts.     

Wettability of carbon fibers modified by acrylic acid and interface properties of carbon fiber/epoxy

The oxidation-reduction and pre-irradiation induced methods were employed to study the effect of acrylic acid modification on the wetting and adsorption ability of carbon fiber (CF) in epoxy solution and the interfacial properties of CF/epoxy. Systematic experimental work was conducted to determine the surface topography, surface energy, surface chemical composition, absorbability and tensile strength of carbon fibers and interfacial adhesion of CF/epoxy before and after modification. The roughness, surface energy, amount of containing-oxygen functional groups and wetting ability were all found to increase significantly after modifications. The tensile strength of carbon fibers was improved marginally by γ-ray pre-irradiation while was decreased little by oxidation-reduction modification. Consequently, the surface modifications of carbon fibers via both oxidation-reduction and pre-irradiation led to an improvement (more than 15%) of the interlaminar shear strength of CF/epoxy composites. The mechanisms of interfacial improvement of modified CF/epoxy composites are proposed.     

Low Temperature Catalytic Hydrolysis of Carbon Disulfide on Activated Carbon Fibers Modified by Non-thermal Plasma

In order to improve the carbon disulfide (CS₂) catalytic hydrolysis efficiency of activated carbon fibers (ACFs), ACFs surface was modified by non-thermal plasma (NTP). In particular, the effects of modification conditions on the catalyst properties were studied, including the reactor structure, modification atmosphere, modification time, output voltage and discharge gap. The catalytic activity study showed that ACFs with NTP modification enhanced CS₂ catalytic hydrolysis. The optimal reactor structure, modification atmosphere, modification time, output voltage and discharge gap was a coaxial cylinder, an N₂ atmosphere, 5 min, 7 kV and 7.5 mm, respectively. The effect of the NTP modification on the micro-structural properties of the ACFs was characterized using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS) methods. The results showed that NTP modification improved the dispersion of functional groups and increased the number of oxygen-containing and nitrogen-containing functional groups, thus the catalytic activity could be enhanced. The present results indicated that NTP modification was an effective way to manipulate ACFs surface properties for the CS₂ catalytic hydrolysis reaction.     

Poly(lactic acid)/Poly(3-hydroxybutyrate) Biocomposites with Differently Treated Cellulose Fibers

The growing concern about environmental pollution has generated an increased demand for biobased and biodegradable materials intended particularly for the packaging sector. Thus, this study focuses on the effect of two different cellulosic reinforcements and plasticized poly(3-hydroxybutyrate) (PHB) on the properties of poly(lactic acid) (PLA). The cellulose fibers containing lignin (CFw) were isolated from wood waste by mechanical treatment, while the ones without lignin (CF) were obtained from pure cellulose by acid hydrolysis. The biocomposites were prepared by means of a melt compounding-masterbatch technique for the better dispersion of additives. The effect of the presence or absence of lignin and of the size of the cellulosic fibers on the properties of PLA and PLA/PHB was emphasized by using in situ X-ray diffraction, polarized optical microscopy, atomic force microscopy, and mechanical and thermal analyses. An improvement of the mechanical properties of PLA and PLA/PHB was achieved in the presence of CF fibers due to their smaller size, while CFw fibers promoted an increased thermal stability of PLA/PHB, owing to the presence of lignin. The overall thermal and mechanical results show the great potential of using cheap cellulose fibers from wood waste to obtain PLA/PHB-based materials for packaging applications as an alternative to using fossil based materials. In addition, in situ X-ray diffraction analysis over a large temperature range has proven to be a useful technique to better understand changes in the crystal structure of complex biomaterials.     

Effect of plasma treatment on cellulose fiber

Cotton cellulose fibers were modified in inert plasma. Surface morphology of the modified fibers was studied by SEM and changes in the surface composition by XPS and FTIR. Standard goniometry was used for determination of contact angle as a function of modified fiber aging. Absorptivity of modified fibers was determined by gravimetry and fiber width in physiological solution, simulating body liquids, by confocal microscopy. Antibacterial effect of pristine and plasma treated samples was examined by following growth of Escherichia coli. Plasma treatment led to surface ablation, changes in surface morphology and fiber width. Surface of the plasma modified fibers was oxidized and their water absorptivity was reduced. The plasma modification did not affect E. coli growth substantially.     

Novel polymeric platform produced by photodegradation-induced rearrangement for a multifunctional negative photoresist

Herein, a series of polymers containing the photosensitive 2-dinitro-benzenemethanol carbonate (DNBC) was developed by click polymerization. Due to the unique photochemical cleavage recombination behavior of DNBC, these polymers were used as negative photoresists to create micropatterns. Furthermore, the photochemical behaviors of DNBC were studied by nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC). According the results, we speculated that the photochemical reaction of DNBC involved an initial chemical bond-breaking process and a subsequent recombination process. Importantly, by extending the aldehyde to a branched-chain structure, reactive patterns were developed by film preparation. Clickable amine functional molecules could be grafted upon the substrates by surface modification. Surface modification of reactive patterns with fluorescent amines gave a multifunctional pattern with tunable properties confirmed by scanning electron microscopy (SEM) and confocal fluorescence microscopy.     

Study on the cationic modification and dyeing of ramie fiber

A modification procedure for ramie fiber using 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC) as a cationic agent and NaOH as a catalyst was developed in this paper. The morphological and structural transformations of the fiber induced by modification were determined by XRD (XRD), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). XRD results show that the crystal structure of the modified fiber was still preserved although its crystallinity was decreased, which was confirmed from the TGA results. The mechanisms for the modification and dyeing of ramie fiber were analyzed, and the optimum modification conditions were determined to be the CHPTAC concentration of 30 g L⁻¹, the NaOH concentration of 15 g L⁻¹, the reaction temperature of 50 °C, and the reaction time of 60 min. The raw and the modified fibers were dyed with C.I. reactive red 2. The K/S values for the cationic modified fiber increased to be three times as high as the unmodified fiber. The dye uptakes increased greatly with an increase in the nitrogen contents up to 0.4% on the modified fibers.     

邻苯二酚-四乙烯五胺改性超高分子量聚乙烯纤维

应用Cat-TEPA改性超高分子量聚乙烯(UHMWPE)纤维,在难黏附的纤维表面形成均匀涂层.采用透射电子显微镜(TEM)、红外光谱(FTIR)、X射线光电子能谱(XPS)、X射线衍射(XRD)、示差扫描量热(DSC)、热重分析(TGA)和静态接触角测试等手段对其结构和性能进行了表征,并通过单丝拔出实验研究改性前后纤维与环氧树脂之间的界面剪切强度(IFSS),探索了反应物配比、反应时间对表面性能的影响,并确定最佳改性条件.结果表明Cat-TEPA共沉积改性未影响纤维的结晶和热稳定性,改性后纤维表面浸润性得到改善,且适当增加反应时间和TEPA含量能够提高纤维和树脂之间的IFSS,当Cat-TEPA摩尔比为1:4,反应时间为24 h时效果最佳,与未改性纤维相比,界面剪切强度提升约44%.     

Grafting of wheat straw fibers with poly (ε‐caprolactone) via ring‐opening polymerization for poly(lactic acid) reinforcement

The use of natural materials has grown in the last years in the plastics industry. Natural lignocellulose fibers derived from agricultural waste present potential to be used as a replacement for glass fibers for polymer reinforcement, leading to lower CO₂ footprint products. This work focuses on the modification of the cellulose fibers in order to improve the compatibility with poly(lactic acid) (PLA). The scoured wheat straw fibers were grafted with polycaprolactone (PCL) through ring opening polymerization. Thermal stability of the wheat straw fibers improved after chemical modifications enabling higher processing temperatures. Flexural and tensile moduli were improved by 23% and 15%, respectively, compared with neat PLA, using 20 wt% modified fibers. An improvement of 20% in the impact strength was obtained using PCL grafted fibers because of entanglements and molecular interactions between PCL grafted on the wheat straw fibers and PLA molecules. Copyright © 2015 John Wiley & Sons, Ltd.     

The interfacial adhesion of wood fiber–reinforced UHMWPE composite filled with acid‐treated clay

Wood fiber–reinforced ultrahigh molecular weight polyethylene (wood fiber/UHMWPE) composites have been filled with acid‐treated clay to enhance the adhesion. According to the modification, the interlaminar shear strength of composites has been greatly improved. X‐ray photoelectron spectroscopy and scanning electron microscopy are used to examine the microscopic properties of resultant composites. The enhanced interlaminar shear strength is attributed to the clay interlock, which improves the wetting between wood fibers and resins.