Water Desorption Kinetics of Polymer Composites with Cellulose Fibers as Filler

The water desorption kinetics of polymer composite systems with hydrophilic cellulose fibers from recycled paper (PSP) filler embedded in various polymer matrices (hydrophobic thermoset epoxy resin [EP] and thermoplastic polypropylene [PP], and hydrophilic thermoplastic poly[vinyl alcohol] [PVA]) was studied. Polymer composites test pieces containing 0, 3, 6, 9, and 30 wt. % of fibers were prepared. Adhesion between fibers and polymer matrices was improved by utilization of maleic anhydride grafted polypropylene (MAPP) coupling agent in the case of thermoplastic matrices (both PP and PVA). Water desorption tests were conducted after immersing test pieces in a distilled water bath at room temperature for 24 h. Study of the water desorption kinetics proved the expected enhanced absorption of the resulting composites after incorporation of cellulose fibers. A difference between two similar types of PVA by measurement of the desorption kinetics was found.     

Degradation Studies of Polycaprolactone in Banana Fibers Reinforced Thermoplastics Composites

In this paper we report the fabrication, properties and degradation studies of banana fibers–reinforced thermoplastic polymers. In order to impart hydrophobicity to the fibers and also to concomitantly increase interfacial bond strength, which is a critical factor for obtaining better mechanical properties of composites, banana fibers were treated with sodium hydroxide (5% and 10% for 4 h), sebacoyl chloride (SC) (0.5 g, 4 h), or toluene diisocyanate (TDl) (1.5 mL, 4 h). Mechanical properties of banana fibers treated with TDl were not affected to any significant extent, but there was an increase in tensile strength of fibers treated with sodium hydroxide (NaOH). Deterioration in mechanical properties was observed upon SC treatment. In thermograssimetre analogue (TGA) studies fibers showed initial mass loss (6.5%–9.5%) in the 50–150°C temperature region. Major weight loss occurred above 200°C. Scanning electron microscope (SEM) studies revealed an increase in surface roughness after alkali treatment. High density polyethylene (HDPE) modified by blending with poly (ε‐caprolactone) (80:20 w/w) was used as a thermoplastic matrix. Composites were fabricated by using 1 cm long banana fibers; the weight fraction of fibers was varied from 0.05–0.13. An increase in weight fraction of fibers resulted in an increase in tensile strength and modulus and decrease in elongation at break. Thin sheets and dumbbells were used for enzymatic and chemical hydrolysis degradation tests. The degradation of the material was monitored by weight change and loss of mechanical properties. The enzymatic degradation in (PCL) presence of Pseudomonas cepacia lipase (PCL) gave appreciable weight loss in PCL and blended materials.     

Adhesion and Young’s Modulus Estimation for Chemically Treated Argan Nut Shell Particles Reinforced Poly-Lactic Acid Polymer

Abstract

The use of natural fillers as reinforcements for polymer plastics takes place in a variety of industrial applications. Henceforth, the use of theoretical models to predict the properties of such bio-composites is essential. In this work, we estimated the Young’s modulus of poly-lactic acid (PLA) bio-composites reinforced with argan nut shell (ANS) chemically treated particles (successive alkali treatment, bleaching and silane treatments) using five theoretical models and compared the predicted results with our prior experimental results. These models allowed us to study the assumed spherical form of the ANS particles and the adhesion/distribution of these particles in a PLA matrix. The results indicated that the ANS chemically treated particles could be considered as spherical particles having good adhesion with the PLA matrix. In addition, three other mathematical models were used to predict Young’s modulus of the ANS chemically treated particles. The results showed that the highest value of Young modulus among the three treatments was obtained for the ANS alkali-bleached particles. In addition, the silane treatment enhanced the adhesion between the ANS particles and the PLA matrix, but decreased the Young’s modulus value compared to the other two treatments.     

Fabrication and Flexural Properties of Bagasse Fiber Reinforced Biodegradable Composites

Biodegradable composites made from bagasse fiber and biodegradable resin were fabricated and the flexural properties of the composites investigated in terms of the effects of fiber length, fiber volume fraction, and different alkali treatments of the bagasse fibers. The flexural properties of the composites increased with the increase in fiber length but decreased below the critical fiber length. The flexural properties increased with the increase in fiber volume fraction. The scanning electron microscope (SEM) micrographs showed that compression of the cellulose structure of bagasse fiber after preparation could have caused enhancement in the flexural properties. Furthermore, when comparing the effects of different alkali treatments of the bagasse fibers, maximum improvement in the flexural properties was observed for the 1% NaOH solution treated fiber composites. After alkali treatment, fibrillation occurred and the surface of the treated fibers became finer; this could contribute to improvement in the fiber‐matrix adhesion and result in enhancing the flexural properties.     

Study on the Tribological Properties of Carbon Fabric Reinforced Phenolic Composites Filled with Nano-Al2O3

Carbon fabric reinforced phenolic (CFRP) composites filled with nano-Al₂O₃ were prepared by a dip-coating and heat molding process and the tribological properties of the resulting composites under different sliding conditions were investigated systematically on a block-on-ring test rig. The worn surfaces were observed in a scanning electron microscope (SEM) to understand the mechanism. Nano-Al₂O₃ particles, as the filler, were effective in reducing the friction coefficient and wear rate of the CFRP composites. The steady state friction coefficient of the CFRP composites filled with 4 wt.% nano-Al₂O₃ particles was about 65.5% of that of unfilled CFRP composites, and the wear rate, in this case, was about 74.7% of that of unfilled CFRP composites. Tribological tests under different sliding conditions revealed that the filled CFRP composites seemed to be more suitable than unfilled CFRP composites for tribological applications under higher sliding speed and load. Moreover, the wear resistances of the unfilled and filled CFRP composites were found to be related to the stability of the transfer film on the counterface.     

Mechanical Properties Comparison of Various Ratios of L-Lactide Grafted Sisal Fibers and Untreated Sisal Fibers Reinforced Poly (lactic acid) Composites

Composites composed of the mixed fibers of L-lactide (LA) grafted sisal fiber (SF-g-LA) and untreated sisal fiber (USF) in a poly (lactic acid) (PLA) matrix were prepared with SF-g-LA/USF fibers ratios of 0, 1:9, 3:7, 5:5, 7:3, 9:1, and 1. The mechanical properties and the interfacial performance of the mixed SF reinforced PLA composites were investigated. The results of the study showed that the introduction of SF-g-LA improved the tensile strength, tensile modulus, flexural strength and flexural modulus of the mixed SF reinforced PLA composites compared with pure PLA or PLA composites with only USF, resulting from the improved interfacial adhesion between SF-g-LA and the PLA matrix. In addition, the introduction of some amount of USF enhanced the reinforcing efficiency of the mixed SF in the composites compared to the PLA composites with only SF-g-LA, owing to the good mechanical properties of USF itself. Furthermore, as for the tensile strength and tensile modulus of the mixed SF reinforced PLA composites, the optimal ratio of SF-g-LA and USF was 7:3, whereas for the flexural modulus of the mixed SF reinforced PLA composites, the optimal mixed ratio of SF-g-LA and USF was 3:7.     

高保偏聚合物光子晶体光纤的化学制备技术研究

研究了大尺寸高保偏聚合物光子晶体光纤（polymer Photonic Crystal Fibers,pPCFs）预制棒的化学原位制备技术.采用预聚物浇铸后加热聚合方法,成功制备了具有高保偏性能的光纤预制棒, 给出了聚合反应的最佳条件.对此预制棒进行二次拉伸及光学和化学性质的测试表明,该方法得到的预制棒力学结构稳定、光学透明度高,且拉伸所得光纤微结构保持完好、微孔坍塌率低、非固有损耗小.若在聚合反应体系中加入适量的激光染料或其它稀土有机螯合物等物质,可得到具有荧光性的高保偏聚合物光子晶体光纤预制棒,为保偏型聚合物光子晶体光纤激光器的研制提供新材料.     

Properties of Polyamide-6 Composites Reinforced with Hydroxyapatite Nanospheres

Hydroxyapatite nanospheres (nHA) were first synthesized from (NH₄)₂HPO₄ and CaCl₂ precursors in the presence of poly(vinyl alcohol) templates. The structure and morphology of as-synthesized products were examined by materials characterization techniques. X-ray diffraction patterns and Fourier transform infrared spectra showed that the nHA (50–70 nm) exhibit the crystalline structure and vibration bands of HA. The Ca/P molar ratio of nHA approached the stoichiometric value of 1.67. The nHA were then melt blended with polyamide-6 (PA6), followed by injection molding. Tensile and flexural measurements showed that the tensile and bending strengths of injection molded PA6–10 wt% nHA composite were close to those of human cortical bone. A simulated body fluid immersion test revealed that apatite crystals can be readily deposited on the PA6–10 wt% nHA composite surface after immersion for 30 days.     

Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.     

Effect of Wood Flour on the Curing Behavior,Mechanical Properties,and Water Absorption of Natural Rubber/Wood Flour Composites

The preparation of natural rubber/wood flour (NR/WF) composites and the influence of WF content, modification, and particle size on the vulcanizing behavior, mechanical properties, and water absorption of NR/WF composites are described. Results show that the addition of WF into NR delayed the scorching time and vulcanizing time of NR. The appropriate WF contents can improve the mechanical properties of NR. However, the overloading of WF destroys the mechanical properties of NR. The addition of WF increased the water absorption of NR. The silicone couple agents that were used to modify the WF had little effect on the water absorption of NR/WF composites. Decreasing the WF particle size enhanced the water absorption of NR/WF composites because the water-absorbing surface area increased with decreasing WF particle size. The water absorption of sisal-fiber-filled NR-based composites was larger than that of the WF-filled NR-based composites. A useful equation, w=ktⁿ , was inferred from the water absorption results to calculate the water absorption (w) of the NR/WF composites as a function of time (t), where k was a constant concerning the compounds’ character that was primarily determined by the WF's character and n was the power of time that was related to the NR's inherent character, such as cross-linking density, and primarily determined the water absorption rate.     

Properties of Waterborne Polyurethanes Based on Polycarbonate Diol Reinforced with Organophilic Clay

Abstract

Nanocomposite of waterborne polyurethane (PU) based on poly(hexamethylene carbonate) diol reinforced by organophilic clay was prepared. Exfoliation of silicate layer in PU was confirmed by x-ray diffraction pattern and transmission electron microscopy. Reinforcing effect of clay was examined by observing dynamic mechanical properties, tensile properties, and shore A hardness. The modulus increased as the content of clay in PU matrix was increased, and this increase was more evident when the PU matrix becomes soft at the temperature range above the glass transiton temperature of soft segment. Water swell was decreased and thermal resistance was increased as the content of clay was increased. Reduction of transparency by added clay was marginal.     

Study on the Tribological Properties of Carbon Fabric/Polyimide Composites Filled with SiC Nanoparticles

Carbon fabric reinforced thermoplastic polyimide composites have significant applications in the field of tribology. However, there are relatively few studies that have been focused on the investigation of these materials. In the present study, carbon fabric/polyimide (CF/PI) composites, reinforced further with SiC nanoparticles, were prepared by dip-coating and hot press molding methods. Rockwell hardness and flexural testing of the composites were conducted. The friction and wear behavior of the resulting carbon fabric composites were evaluated in a ring-on-block contact mode under dry sliding condition. The results showed that the SiC nanoparticles significantly improved the hardness and flexural strength when compared to the CF/PI composites without the SiC additions. The CF/PI composites reinforced with 5 vol% SiC nanoparticles demonstrated the most beneficial mechanical and tribological properties compared to the composites with greater and lesser SiC nanoparticles. Scanning electron microscopy (SEM) and optical microscopy (OM) were employed in order to study the mechanism of tribological behavior. A continuous and thin transfer film formed during the friction test of the composites led to a significant improvement of the tribological properties.