Polylactide and hybrid silicasol nanoparticle‐based composites

The effects of the chemical nature and size of the hybrid nanoparticle external layer on the structures and properties of polylactide composites are investigated. Polylactide is used as the matrix polymer, and molecular silicasol particles with γ‐hydroxypropylic, (methoxyacetyl)oxy, and acetoxy surface groups serve as fillers. A preliminary assessment of the thermodynamic compatibility of polylactide with the surface groups of molecular silicasols is performed. The hydrophilic shells of the silicasols prevent their aggregation in the bulk of the nanocomposite. It shows variations in the chemical structure of the surface layer of the nanoparticles as well as their sizes and concentration make it possible to conduct a controlled change of the characteristics of the composites, particularly to eliminate one of the drawbacks of PLA, the low speed of its crystallization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41894.     

One‐step green treatment of hemp fiber used in polypropylene composites

In this article, an eco‐friendly and cost effective surface treatment method is proposed for hemp fiber, enabling fabrication of hemp fiber/polypropylene (PP) composites, which show better mechanical properties than the PP composites containing untreated or alkali treated hemp fiber. Various techniques, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), moisture analysis, and differential scanning calorimetry (DSC), are employed for the characterization of hemp fiber and polymer composites interface. Based on these results, the conventional alkali treatment of hemp fiber results in the damage of elementary fiber by eliminating parts of lignin and hemicellulose, which could be the reason for the decline of mechanical properties for the resulted polymer composites. On the contrary, water treatment cleans the fiber surface by effectively removing the water‐soluble polysaccharides while ensures minimum degradation on elementary fiber structure, which contributes to the improved mechanical properties of final polymer composites: the Young's modulus, fracture stress and fracture strain were enhanced by 3.66, 7.86, and 14.6%, respectively, when compared with untreated fiber reinforced composites. POLYM. COMPOS., 37:385–390, 2016. © 2014 Society of Plastics Engineers     

A novel method for preparing composites of PDMS/PS core–shell emulsion and polystyrene

A novel and simple method for preparing composites of PDMS/PS core–shell emulsion and polystyrene was reported. This method was based on emulsion and suspension in situ polymerization. The relationship between the process of core–shell emulsion breaking and electrolyte concentration was studied by spectrophotometry. The results of transmission electron microscopy showed that polydimethylsiloxane soft particles were dispersed uniformly in the composites. Diameters of the composite beads ranged from 0.5 to 4.0 mm, which could be controlled by adjusting the amount of hydroxyapatite. At last, the properties of the latex film including water absorption ratio, contact angle, pendulum hardness and transparency were tested. The results showed that the content of emulsion obvious affected the properties. During the process of emulsion and suspension in situ polymerization, the contact angle of the latex films ascended to 106.06° and the transmission ratio at 500 nm decreased to 0.3 with the increasing of core–shell emulsion. Whereas, the absorption and pendulum hardness fell to 0.37% and 322 S, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A new method for preparing high impact polypropylene and polyethylene

Summary The impact strength of polypropylene was improved by adding propylene-vinylsilane copolymer (PVS) in the presence of tris(triphenylphosphine)rhodium chloride(TPR). The impact strength of polyethylene at low temperature was also improved by adding TPR and PVS which is brittle at low temperature. These phenomena were not observed when polymers were mixed without TPR.     

A novel method for preparing bipolar membranes

A method for preparing a bipolar membrane from separate anion and cation exchange films is described. In the procedure an inorganic electrolyte solution is introduced between the films before they are pressed together. The resulting membrane has a low electrical resistance and a high “water splitting” efficiency.     

Torrefied biomass‐polypropylene composites

Torrefied almond shells and wood chips were incorporated into polypropylene as fillers to produce torrefied biomass‐polymer composites. The composites were prepared by extrusion and injection molding. Response surface methodology was used to examine the effects of filler concentration, filler size, and lignin factor (relative lignin to cellulose concentration) on the material properties of the composites. The heat distortion temperatures, thermal properties, and tensile properties of the composites were characterized by thermomechanical analysis, differential scanning calorimetry, and tensile tests, respectively. The torrefied biomass composites had heat distortion temperatures of 8–24°C higher than that of neat polypropylene. This was due to the torrefied biomass restricting mobility of polypropylene chains, leading to higher temperatures for deformation. The incorporation of torrefied biomass generally resulted in an increase in glass transition temperature, but did not affect melting temperature. Also, the composites had lower tensile strength and elongation at break values than those of neat polypropylene, indicating weak adhesion between torrefied biomass and polypropylene. However, scanning electron microscopy results did indicate some adhesion between torrefied biomass and polypropylene. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41582.     

A novel approach in preparing polymer/nano-CaCO composites

An novel compounding process using nano-CaCO₃ aqueous suspension for preparing polymer/nano-CaCO₃ composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nanoparticle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO₃ in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO₃ improve slightly. It proved that this approach is suitable for the preparation of nanocomposites based on both polar and non-polar polymers.     

Fabrication and applications of cellulose nanoparticle‐based polymer composites

The impressive mechanical properties, reinforcing capability, abundance, low weight, low filler load requirements, and biodegradable nature of nanoparticles from bioresources such as cellulose, make it an ideal candidate for the development of green polymer nanocomposites. Significant amount of research in this area is primarily focused on the extraction, qualitative surface modification, and evaluation of mechanical performance after filling in polymer matrixes at different ratios. The extreme agglomeration tendency, hydrophilic nature, difficult dispersion in many organic solvents of cellulose nanoparticles are the challenging obstacles when fabrication of such nanocomposites is concerned. Traditional processing of polymer composites mainly through extrusion and melt compounding, is not easily possible in case of cellulose nanocomposites due to higher possibility of poor dispersion and degradation of nanofibers. Therefore, issues related to the fabrication of nanofiber‐based products and their application appears to be one of the most important areas in order to enhance their competitiveness with other nanoparticles. This review is aimed to summarize the recent accomplishments and issues involving the use of cellulose nanoparticles in the development of new polymeric materials. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Effect of single‐mineral filler and hybrid‐mineral filler additives on the properties of polypropylene composites

The present study was carried out to determine the filler characteristics and to investigate the effects of three types of mineral fillers (CaCO₃, silica, and mica) and filler loadings (10–40 wt%) on the properties of polypropylene (PP) composites. The characteristics of the particulate fillers, such as mean particle size, particle size distribution, aspect ratio, shape, and degree of crystallinity were identified. In terms of mechanical properties, for all of the filled PP composites, Young's modulus increased, whereas tensile strength and strain at break decreased as the filler loading increased. However, 10 wt% of mica in a PP composite showed a tensile strength comparable with that of unfilled PP. Greater tensile strength of mica/PP composites compared to that of the other composites was observed because of lower percentages of voids and a higher aspect ratio of the filler. Mica/PP also exhibited a lower coefficient of thermal expansion (CTE) compared to that of the other composites. This difference was due to a lower degree of crystallinity of the filler and the CTE value of the mica filler. Scanning electron microscopy was used to examine the structure of fracture surfaces, and there was a gradual change in tensile fracture behavior from ductile to brittle as the filler loading increased. The nucleating ability of the fillers was studied with differential scanning calorimetry, and a drop in crystallinity of the composites was observed with the addition of mineral filler. Studies on the hybridization effect of different (silica and mica) filler ratios on the properties of PP hybrid composites showed that the addition of mica to silica‐PP composites enhanced their tensile strength and modulus. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

A novel method for preparing bimodal elastomeric networks

Summary Hydroxyl-terminated chains of poly(dimethylsiloxane) (PDMS) were end linked with a trifunctional silane containing 3-aminopropyl groups. CuCl₂ or CoCl₂ added to the networks forms complexes with the amino groups on the cross links, thus introducing additional chains that are very short. The resulting PDMS networks are in this sense bimodal, and were found to have increased values of the ultimate strength.     

A novel approach in preparing polymer/nano-CaCO3 composites

An novel compounding process using nano-CaCO₃ aqueous suspension for preparing polymer/nano-CaCO₃ composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO₃ in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO₃ improve slightly. It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers. __________ Translated from Acta Polymerica Sinica, 2007, (1): 53–58 [译自: 高分子学报]     

Synthesis and characterization of hydrogel‐silver nanoparticle‐curcumin composites for wound dressing and antibacterial application

Hydrogel silver nanocomposites are found to be excellent materials for antibacterial applications. To enhance their applicability novel hydrogel‐silver nanoparticle‐curcumin composites have been developed. For developing, these composites, the hydrogel matrices are synthesized first by polymerizing acrylamide in the presence of poly(vinyl sulfonic acid sodium salt) and a trifunctional crosslinker (2,4,6‐triallyloxy 1,3,5‐triazine, TA) using redox initiating system (ammonium persulphate/TMEDA). Silver nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating the silver ions and subsequent reduction with sodium borohydride. Curcumin loading into hydrogel‐silver nanoparticles composite is achieved by diffusion mechanism. A series of hydrogel‐silver nanoparticle‐curcumin composites are developed and are characterized by using Fourier transform infrared (FTIR) and UV–visible (UV–vis) spectroscopy, X‐ray diffraction, thermal analyses, as well as scanning and transmission electron microscopic (SEM/TEM) methods. An interesting arrangement of silver nanoparticles i.e., a shining sun shape (ball) (～ 5 nm) with apparent smaller grown nanoparticles (～ 1 nm) is observed by TEM. The curcumin loading and release characteristics are performed for various hydrogel composite systems. A comparative antimicrobial study is performed for hydrogel‐silver nanocomposites and hydrogel‐silver nanoparticle‐curcumin composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

粘土还原氮化合成O'-Sialon基复合材料

采用高峰土碳热还原氮化合成O’-Sialon基复合材料。结果表明,在一定实验条件下,当烧结温度较低时(1400 ℃),碳热还原的最终产物为O’-Sialon、Si3N4;烧结温度较高时(1500℃),最终产物为O’-Sialon、SiC;温度处于两者之间时(1450℃),O’-Sialon、Si     

Steam‐exploded residual softwood‐filled polypropylene composites

Residual softwood sawdust was pretreated by a steam‐explosion technique. It was used as a natural filler in polypropylene (PP)‐based composites. Dynamic mechanical analysis and tensile properties of these materials were studied. The influence of filler loading, steam‐explosion severity, and coating the fiber with a functionalized compatibilizer, such as maleic anhydryde polypropylene (MAPP), on the mechanical behavior of the composite was evaluated. The results were analyzed in relation with scanning electron microscopy observations, and surface energy (dispersive and polar components) and apparent specific area measurements. Experimental data indicate a better compatibility between MAPP‐coated fiber and PP with respect to the untreated one. The coating treatment of the softwood fiber was found to promote interfacial adhesion between both components, and to enhance the tensile properties of the resulting composite. This reinforcing effect was well predicted from theoretical calculations based on a mean field approach (Halpin‐Kardos model). The steam‐explosion pretreatment severity increased the surface energy and apparent specific surface, and resulted in a loss of the fiber entirety. The sorption behavior of these composite materials was also performed. It was found that the composites absorb more water, as the filler content is higher. MAPP coating provided protection from water uptake in the interphase region. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1962–1977, 1999     

A reactive extrusion process with the aid of ultrasound for preparing cross‐linked polypropylene

Introducing the crosslinked structure in polypropylene (PP) was highly desired to meet the requirement of high melt strength, which was a key for the application of PP in thermoforming, blow molding and foaming where elongation flows dominated. In this work, the power ultrasound was introduced into the reactive extrusion at the exit die of an extruder for preparing crosslinked PP. The main target was to maintain the highly crosslinked structure during reactive extrusion process in case of low peroxide concentration. The results of the dynamic rheological properties, melt flow index, and extensional viscosity measurement showed that the content of PP gel and the melt strength of PP increased obviously with the employment of a 300 W ultrasound while the contents of functional monomers and peroxide were constant. Fourier transform‐infrared spectroscopy analysis, differential scanning calorimeter characterization, and gel permeation chromatograph measurement proved that the increases of content of PP gel and melt strength of PP were caused by that the ultrasonic waves could induce the chain scission and recombination reaction when the PP melts flowed through the exit die assembled with a ultrasonic probe. POLYM. ENG. SCI., 57:821–829, 2017. © 2016 Society of Plastics Engineers     

Seaweed as novel biofiller in polypropylene composites

Based on former exploratory research, we used seaweed (SW) fiber as a novel biofiller for the production of polypropylene (PP) biocomposites. Maleic anhydride‐grafted polypropylene (MAPP) and a CNT masterbatch (CESA) were applied as compatibilizers. Mechanical properties, crystallization behavior, dynamic mechanical performance as well as interfacial morphology were characterized. SW fiber was successfully incorporated in the PP matrix in terms of mechanical reinforcement. Accelerated crystallization process of PP matrix was observed. DMA results also indicated the favorable adhesion between SW fiber and PP matrix, which could be confirmed by SEM characterization. The effect and efficiency of MAPP and CESA as compatibilizers were evaluated. Moreover, potential flame retardancy of SW fibers for PP matrix was observed, and satisfying results warrant further investigations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Mechanical behavior of agro‐residue‐reinforced polypropylene composites

In this research, fully environment‐friendly, sustainable and biodegradable composites were fabricated, using wheat straw and rice husk as reinforcements for thermoplastics, as an alternative to wood fibers. Mechanical properties including tensile, flexural, and impact strength properties were examined as a function of the amount of fiber and coupling agent used. In the sample preparation, three levels of fiber loading (30, 40, and 50 wt %) and two levels of coupling agent content (0 and 2 wt %) were used. As the percentage of fiber loading increased, flexural and tensile properties increased significantly. Notched Izod results showed a decrease in strength as the percentage of fiber increases. With addition of 50% fiber, the impact strengths decreased to 16.3, 14.4, and 16.4 J/m respectively, for wheat straw‐, rice husk‐, and poplar‐filled composites. In general, presence of coupling agent had a great effect on the mechanical strength properties. Wheat straw‐ and rice husk‐filled composites showed an increase in the tensile and flexural properties with the incorporation of the coupling agent. From these results, we can conclude that wheat straw and rice husk fibers can be potentially suitable raw materials for manufacturing biocomposite products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of polypropylene fiber/banana fiber composites by novel commingling method

Short natural fiber thermoplastic composites are usually fabricated by melt mixing or solution mixing followed by conventional methods like injection molding or compression molding. In melt mixing, the fibers are subjected to high shear and this damage the natural fiber. In solution mixing, the use of the organic solvent is essential and its use is hazardous. Development of a novel method commingling to prepare polypropylene (PP)/short natural fiber composite is the main objective of this study. The influence of fiber loading on the mechanical properties of the composites prepared by the above method has been evaluated. The applications and limitations of several equations to predict physical properties such as tensile strength and modulus of the composites have been described. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Recycled‐disposable‐chopstick‐fiber‐reinforced polypropylene green composites

The utilization of disposable chopsticks is very popular in Taiwan, China, and Japan and is one of the major sources of waste in these countries. In this study, recycled disposable chopstick fiber was chemically modified. Subsequently, this modified fiber and polypropylene‐graft‐maleic anhydride were added to polypropylene (PP) to form novel fiber‐reinforced green composites. A heat‐deflection temperature (HDT) test showed an increase of approximately 81% for PP with the addition of 60‐phr fibers, and the HDT of the composite could reach up to 144.8°C. In addition, the tensile strength, Young's modulus, and impact strength were 66, 160.3, and 97.1%, respectively, when the composite material was 40‐phr fibers. Furthermore, this type of reinforced PP would be more environmentally friendly than an artificial‐additive‐reinforced one. It could also effectively reduce and reuse the waste of disposable chopsticks and lower the costs of the materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012