Fabrication and mechanical analysis of mimosa tannin and commercial flax fibers biocomposites

Composites were prepared by impregnating commercial nonwoven and unidirectional flax fibers mats, with a mimosa tannin/hexamine resin without addition of NaOH as it was described in previous papers and with improved results. The influence of various parameters was observed: the curing cycle including temperature, time, pressure, the moisture content, and the number of fiber mats the composites were made of. A new two-step method was investigated: full drying of the pre-impregnated mats for storage first and then rehydratation just before pressing. The composites obtained gave good modulus of elasticity and tensile strength in traction as well as a good resistance to water swelling for composites prepared with 50% matrix resin/50% natural fibers. Best results appear to be obtained using a slow curing at low temperature (130?°C for 35?min) with moisture content of 20% on dry material.     

The packing stress of impregnated fiber mats

The parameters affecting the packing stress of fiber mats for melt impregnation, resin transfer molding and compression molding are systematically investigated. An analytical equation based on local bending of fibers, which was previously derived for non‐impregnated networks, is applied to composite mats of dispersed planar bundles impregnated with molten polypropylene. It is shown that many simultaneous mechanisms interact during packing of impregnated bundle mats, in particular when the mats are needled. These include in‐plane bending of the bundles, compaction of the fibers within a bundle, and buckling, slippage or breakage of the out‐of‐plane fibers. In order to identify and decouple these features, aspect ratio of the bundles, lubrication, needling intensity and packing history are varied. A microstructural experiment is also developed to evaluate the extent of bundle spreading. It is found that dispersed fibers or bundles roughly follow the equation based on local bending, but that needled bundle networks deviate from the power law behavior. Three regions were identified. The first is attributed to self‐loading of the mats and to buckling of the out‐of plane fibers. The second region is due to slippage and breakage of the out‐of‐plane fibers and depends on the loading history and on the needling intensity. The third region is due to packing of the in‐plane bundles, which do not really bend, or spread under load, but are locally compressible, owing to misalignment and waviness of the individual fibers forming the bundles. In compression molding, the influence of the in‐plane reorientation of the initially out‐of‐plane bundles on the packing stress is observed.     

玻纤在绝缘行业中的应用和展望

介绍了玻璃纤维及制品在浸渍纤维制品、层压制品、塑料制品、云母制品等绝缘材料行业中的应用,分析了十二·五绝缘行业规划中涉及玻璃纤维的新型发电设备、输变电设备、用电设备配套的绝缘材料产品的发展,展望了高性能超薄型玻纤布、玻纤毡、特性化玻纤等特殊要求的绝缘材料的发展前景。     

固化剂对水性汽车罩光清漆固化膜性能的影响

合成了水性丙烯酸树脂并用其配制了汽车罩光清漆,通过FT-IR、DSC,TG和SEM分析研究了不同固化剂、固化剂用量对漆膜性能的影响。结果表明,Luwipal066作为固化剂,固化剂/树脂质量比为40/100,固化温度及时间分别为140℃和30min时,固化漆膜性能最好,光泽度达到98/60°,冲击强度为50kg·cm,硬度为2H,附着力为0级,耐溶剂、耐紫外老化性能良好,指标达到汽车罩光漆膜的要求。漆膜固化后表征羟基和甲氧基的吸收峰强度显著变弱,表明氨基树脂和丙烯酸树脂发生了交联固化。随着硬/软单体配比和固化剂/树脂配比的增加,固化漆膜的Tg升高,具有良好的热稳定性。     

In-plane permeability determination for simulation of liquid composite molding of complex shapes

Process simulation forms an important part of the design loop for parts manufactured by liquid composite molding. Critical to this is the determination of accurate permeability data. While constitutive models and test methods for determination of in-plane permeability of mats and fabrics exist, these do not take account of the effects of changes in fiber architecture during preform manufacture. The deformation behavior of mats and fabrics is reviewed, leading to fiber architecture predictions based upon deformed geometry. Existing models are applied to estimate the distribution of in-plane permeabilities within the preform based upon the predicted fiber architecture. The predictions are compared with test results for pre-stretched and pre-sheared reinforcements, and the method is demonstrated for two prototype automotive parts.     

高质量丙烯酸汽车罩光清漆

介绍了改性羟基丙烯酸树脂的合成工艺，并研究了由其配制的丙烯酸汽车罩光清漆的性能，该涂料是合成工艺简单、耐酸性及物理机械性能较好的汽车用OEM涂料。     

Sheet‐Molded Polyolefin Natural Fiber Composites for Automotive Applications

The use of natural fibers as reinforcing filler in thermoplastics is a relatively new application and has great potential in replacing glass fiber products in automotive industry. However, most of the research in this area has been focused primarily on flax fiber. In the first part of the work presented here, hemp fiber non‐woven mats are used exclusively in combination with a poly(propylene) matrix to study the mechanical properties of natural fiber mat thermoplastics (NMT) in the absence of binder. Film stacking was used as the method of preparation. The results show that hemp‐based NMT have comparable or even higher strength properties as compared with conventional flax‐based thermoplastics. A value of 63 MPa for the flexural strength is achieved at a fiber content of 64 wt.‐%. The influence of the compression ratio on the mechanical properties and density of NMT is also reported. A definite increase in strength is observed with increasing compression together with a much more uniform density profile. In the second part of this study, a unique combination of random hemp fibers, non‐woven mats and poly(propylene) films was employed in film stacking to evaluate strength properties and economic implications. The same fiber content (64 wt.‐%) was maintained in the final NMT by replacing 78 wt.‐% of the mats by random fibers. Preliminary tests reveal better mechanical properties especially in terms of impact energy, which is 50 to 100% higher, as compared with different mats‐only/poly(propylene) combinations. Further, a net saving of 40% in fiber cost is anticipated by replacing 78% non‐woven mats with an equivalent amount of random fibers. Overall results of this study indicate that hemp‐based NMT are promising candidates in automotive applications where high specific stiffness is required.

Tensile Strength of different NMTs and GMT.     

Study on long fiber–reinforced thermoplastic composites prepared by in situ solid‐state polycondensation

Long glass fiber–reinforced thermoplastic composites were prepared by a new process, in situ solid‐state polycondensation (INSITU SSP). In this process reinforcing continuous fibers were impregnated by the oligomer of PET melt, and then the impregnated continuous fibers were cut to a desired length (designated prepreg); finally, the prepreg was in situ polymerized in the solid state to form the high molecular weight matrix. SEM, FTIR spectra, short‐beam shear stress test, flexural strength test, impact strength test, and the intrinsic viscosity measurement were used to investigate the wetting and interfacial adhesion, the mechanical properties of the composite, and the molecular weight of matrix resin in the composite. The results showed that the molecular weight of PET in the matrix resin and mechanical properties could be adjusted by controlling the SSP time and that the high level of interfacial adhesion between reinforcing fibers and matrix resin could be achieved by this novel INSITU SSP process, which are attributed to the good wetting of reinforcing fibers with low molecular weight oligomer melt as the impregnation fluid, the in situ formation of chemical grafting of oligomer chains onto the reinforcing fiber surface, and the in situ formation of the high molecular weight PET chains in the interphase regions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3959–3965, 2004     

Analysis of resin injection molding in molds with preplaced fiber mats. II: Numerical simulation and experiments of mold filling

This work presents the results of numerical simulation and experimental visualization of the mold filling process in resin injection molding with preplaced fiber mats. The mold filling experiments were conducted with various mat stacks consisting of continuous random glass fiber mats and bidirectional stitched glass fiber mats. The use of two different mat types in the mat stack created porosity and permeability variations. The effect of these permeability variations was studied by taking flow pressure measurements and observing the progress of the flow front of a non-reactive fluid filling a clear acrylic mold that contained the reinforcement mat stack. Numerical simulation corresponding to each experiment was also carried out. The numerical results were compared to the experimental measurements.     

Superhydrophobic Mats of Polymer-Derived Ceramic Fibers

Solid preceramic polyaluminasilazane was synthesized through the reaction between liquid cyclosilazane and aluminum tri-sec-butoxide at 160°C. Electrospinning of polyaluminasilazane/polyethyleneoxide (1/0.0001 mass ratio) in chloroform solutions generated smooth fibers while the electrospun fibers from the chloroform/ N,N -dimethylformamide solutions had submicrometer structures on the fiber surfaces. Smooth and rough SiCNO ceramic fibers were obtained by the pyrolysis of the green fibers with an 80% yield. Superhydrophobic mats of ceramic fibers were fabricated via a chemical vapor deposition of perfluorosilane onto the rough fibers. These superhydrophobic mats possess good chemical and thermal stability.     

Effect of Thermoplastic Starch and Photocrosslinking on the Properties and Morphology of Electrospun Poly(ethylene-co-vinyl alcohol) Mats

Nonwoven fibrous mats of poly(ethylene-co-vinyl alcohol) (EVOH) and thermoplastic starch (TPS) blends were successfully prepared through the electrospinning technique using a mixed solvent system of isopropyl alcohol and water. The influence of TPS on the morphology and structure of the fibrous mats was investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The addition of TPS to EVOH resulted in beaded electrospun fibers. The SEM images revealed decreasing average width of the blend fibers and increasing quantity of beads with an increased TPS content. EVOH/TPS fibers mats irradiated under ultraviolet light using sodium benzoate as a photosensitizer were also prepared. The size and number of beads were diminished in the photocrosslinked EVOH/TPS fiber mats. The as-spun and crosslinked EVOH/TPS fiber mats exhibit a superior fluid uptake ability (with 20 wt% of TPS) and superior barrier properties (with 20 and 40 wt% of TPS) in comparison to those observed in neat electrospun EVOH mats. These properties are of particular interest for use in dressing materials for the medical industry and for use in multilayer plastic fuel tanks for the automotive industry, respectively. POLYM. ENG. SCI., 60:474–480, 2020. © 2019 Society of Plastics Engineers     

汽车轮毂罩光用亚光透明粉末涂料的研究与应用

研究了高耐候亚光透明粉末涂料配方的消光体系、树脂的耐候性、消光剂的种类、流平剂的透明度、紫外线吸收剂对耐候性的影响,以及潜伏性促进剂的使用,制备了适用于汽车铝轮毂罩光用亚光透明粉末涂料,并研究了其在汽车铝轮毂涂装中的施工性和应用效果。还研究了汽车铝轮毂罩光用亚光透明粉末涂料与高光丙烯酸型透明粉末涂料的兼容状况和烘烤温度适应性,最终制备了可以和高光环氧基丙烯酸透明粉末涂料共用生产线的亚光透明粉末涂料,依据汽车铝轮毂罩光用粉末涂料各项指标要求,该涂料综合性能相当,且在健康环保、节能、成本和贮存稳定性方面更具优势。     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Adhesion and Hydrolytic Stability of the Interface Between High-Modulus Polyethylene Fibers and Acrylic Resins

The effects of oxyen plasma treatment on the surface chemistry of Spectra 1000® high modulus polyethylene fibers and on the mechanical properties of fiber-reinforced composites of the fibers in a Bis-GMA based acrylic resin have been studied. X-ray photoelectron spectroscopy and diffuse reflectance FTIR spectroscopy have been used to show that the majority of oxygen on the fiber surface exists mostly in the form of ether and/or epoxy linkages, with carbonyl-, carboxylic- and ester-containing compounds accounting for less than 10 percent of the total. While the untreated and plasma-treated fibers have similar chemical compositions, the surfaces of the plasma-treated fibers are more polar and the oxygen is chemically bonded instead of being merely physisorbed. The interfacial shear strength between the fibers and the acrylic resin is increased by a factor of 2.3 by the plasma treatment indicating the presence of a weak boundary layer on the surface of the untreated fibers. The hydrolytic stability of the composite interfaces was investigated for fibers sized with several Bis-GMA-based adhesives. Maximum stability was attained by sizing with Bis-GMA containing a peroxide catalyst or an amine accelerator. The flexural properties of composites utilizing plasma-treated and untreated fibers were compared in three-point bending. The ultimate bending loads for composites using treated fibers were much higher than those for composites with untreated fibers, but only a fraction of that for glass or Kevlar®-reinforced materials.     

玻璃纤维浸胶纱拉伸破坏模式的研究

介绍了浸胶纱拉伸性能试验的原理、仪器和计算方法。通过对玻璃纤维浸胶纱的拉伸性能试验,研究了玻璃纤维浸胶纱弹性模量及伸长率的试验方法。通过分析玻璃纤维浸胶纱的破坏模式,研究了玻璃纤维与树脂基体的复合性能及机理,有利于促进玻璃纤维更合理的应用。     

提高PVC塑溶胶粘合力研究

ＰＶＣ塑溶胶配制的密封胶具有单组分、无溶剂、贮存稳定及弹性好、耐化学介质优良等特点、缺点是粘合力差。本文介绍了环氧树脂、聚氨酯树脂、聚酰胺树脂、丙烯酸树脂、尿素树脂等对ＰＶＣ塑溶胶的增粘作用,论述探讨了增粘剂的结构特点和增粘机理,以及油面胶的配制。     

低温快干氨基丙烯酸聚氨酯涂料的研究

羟基丙烯酸树脂A450与氨基树脂、潜催化剂封闭性磺酸盐、稀释剂等复配成的丙烯酸氨基涂料,具有低温固化特性,该氨基涂料与一定比例的多异氰酸酯固化剂混合得到的氨基聚氨酯涂料,加入二甲苯、醋酸酯、醇类稀释剂不混浊,该涂料储存稳定性好,交联密度高,可常温自干,也可低温固化,涂膜综合性能优异。氨基丙烯酸聚氨酯采用XP2605异氰酸酯固化剂,可显著提高涂料的干燥速度、硬度、耐磨性、耐溶剂等综合性能,降低对水的敏感性。     

Coating of carbon fibers with adhesion-promoting thin poly(acrylic acid) and poly(hydroxyethylmethacrylate) layers using electrospray ionization

Thin coatings of poly(acrylic acid) (PAA) and poly(hydroxyethylmethacrylate) (PHEMA) were deposited onto carbon fibers by means of the electrospray ionization (ESI) technique in ambient air. These high-molecular weight polymer layers were used as adhesion promoters in carbon fiber–epoxy resin composites. Within the ESI process, the carbon fibers were completely enwrapped with polymer in the upper 10 plies of a carbon fiber roving. As identified with scanning electron microscopy also shadowed fibers in a bundle as well as backsides of fiber rovings were pinhole-free coated with polymers (‘electrophoretic effect’). Under the conditions used, the layers have a granular structure. Residual solvent was absent in the deposit. PAA and PHEMA films did not show any changes in composition and structure in comparison with the original polymers as analyzed by X-ray photo-electron spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Single-fiber pullout tests of coated fibers embedded in epoxy resin showed significantly increased interfacial shear strength. It is assumed that chemical bonds between carbon fiber poly(acrylic acid) and epoxy resin contribute significantly to the improved interactions.     

Solid Ceramic Fibers via Impregnation of Activated Carbon Fibers

A process has been developed which allows the preparation of some solid ceramic fibers. In this process, activated carbon fibers which are porous throughout their entire diameter are impregnated with metal-containing solutions such as silicon tetrachloride. Calcination and sintering result in the formation of solid SiO₂ fibers. Use of woven mats or nonwoven felts of activated carbon fibers results in the formation of woven mats or nonwoven felts of silica fibers.     

Electrospinning polycaprolactone dissolved in glacial acetic acid: Fiber production,nonwoven characterization,and In Vitro evaluation

The electrospinning of polycaprolactone (PCL) dissolved in glacial acetic acid and the characterization of the resultant nonwoven fiber mats is reported in this work. For comparison purposes, PCL fiber mats were also obtained by electrospinning the polymer dissolved in chloroform. Given the processing parameters chosen, results show that 14 and 17 wt % PCL solutions are not viscous enough and yield beaded fibers, 20 and 23 wt % solutions give rise to high quality fibers and 26 wt % solutions yield mostly irregular and fused fibers. The nonwoven mats are highly porous, retain the high tensile strain of PCL, and the fibers are semicrystalline. Cells adhere and proliferate equally well on all mats, irrespective of the solvent used in their production. In conclusion, mats obtained by electrospinning PCL dissolved in acetic acid are also a good option to consider when producing scaffolds for tissue engineering. Moreover, acetic acid is miscible with polar solvents, which may allow easier blending of PCL with hydrophilic polymers and therefore achieve the production of electrospun nanofibers with improved properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41068.