Processing flexural properties

Liquid Crystal Polymers Thermoplastic aromatic copolyesters with highly ordered structure. Has good tensile and flexural properties at high temperatures, chemical, radiation and fire resistance, and weatherabil-ity. Processed by sintering and injection molding. Used to substitute ceramics and metals in electrical components, electronics, chemical apparatus, and aerospace and auto parts. Also called LCP. 

In some individual cases of molding thermoplastics, but more frequently with elastomer processing, the finished article cannot be ejected automatically. The part must then be removed manually, because with elastomers, complex articles (as well as those with undercuts) are often produced from comparably simple molds, due to the material s stretchability and flexural properties. The removal of such parts is often so comphcated, that-if at all-only the most highly specialized handling devices ean be employed for automatic demolding. Therefore, manual removal still continues to be carried out in the elastomer processing industry even today. 

McHugh, A.J. etal. (1996) Processing-stracture-properties interaction in polymer-cement composites, in Proceedings MAETA Workshop on High Flexural Polymer-cement Composites, Sakata, pp.59-67. 

Following the trend of using PVC as matrix, research on the use of EFB as composite in PVC matrix was also reported. Bakar et at [37] used the EFB as filler in unplasticized poly(vinyl chloride) (PVC-U). They studied the effects of extracted EFB on the processability, impact and flexural properties of EFB/PVC-U composites. PVC-U resin, EFB and other additives were first dry-blended using a heavy-duty laboratory mixer and then milled into sheets on a two-roll mill before being hot-pressed and cut into impact and flexural test specimens. There were two kinds of EFB used in this experiment, which were extracted and xmextracted. The FTIR showed that the unextracted EFB contained oil residue, while the extracted one contained less oil residue. The results showed that both extracted and unextracted EFB decreased the fusion time and melt viscosity. However, the fusion time increased with the increase of extracted EFB content. Meanwhile, there was no significant difference in both the impact and flexural properties of extracted and xmextracted EFB. 

As the performance of the composite is profoxmdly dominated by the micromechanical deformation process, its knowledge and control are critical for the improvement of composite properties. The effect of particle characteristics and interfacial adhesion on the micromechanical deformation processes in PP-wood composites was investigated by Renner et al. [7]. They proposed a failure map as well as the practical results and considered the influence of matrix characteristics on deformation and failure in PP-natural fiber composites in other research [24]. Hietala et al. [78] studied the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio during the processing and mechanical properties of WPCs. The use of pretreated wood chips enhanced the flexural properties of the wood chip-PP composites. Moreover, the use of undried wood chips compared to dried one can improve and reduce the flexural strength and flexural modulus, respectively. On the other hand, they concluded that the use of pretreated and undried wood chips lead to the highest aspect ratio after compounding. The effect of composition and the incorporation... 

In recent years, the diversity of properties of plastic lumber produced from different mixes of materials, by different processes, has resulted in calls for development of standards. In late 1997, the American Society for Testing and Materials (ASTM) issued five new test methods for plastic lumber intended to help establish a benchmark for minimum plastic lumber performance. The standards include tests for compressive properties, flexural properties, bulk density and specific gravity, compressive and flexural creep and creep rupture, and tests for performance of mechanical fasteners. ... 

Dimer acid-based polyesters being used as thermoplasts, thermoset, and elastomers are used in large quantities as adhesives and coatings. The polyesters, as we have reported herein, may have various commercial applications. Owing to the flexural properties, these low molecular weight linear polyesters of dimer acid may be used as plasticizers providing internal lubrication for various polymers, such as polyimides and inorganic coordination polymers, which may have very poor processibility. 

A usual method is the blending of natural and polypropylene (PP) fibers before formation of bands or nonwovens [3]. So preforms are obtained in form of ribbons or nonwovens ready for thermoforming. The grade of the matrix-forming PP has less effect on the tensile and flexural properties of the composites. Therefore, there are no special requirements for the blended, matrix-forming PP fibers. PP fibers of a fineness between 1.7-6.7 dtex with lengths of 40-60 mm, even PP obtained from recycling processes, may also be used. There are no differences in a composites mechanical performance when homo- or copolymers are used. 

Astrom, B.T., Larsson, P.H., Hepola, P.J. and Pipes, R.B. (1994) Flexural properties of pultruded carbon/PEEK composites as a function of processing history. Composites, 25(8), 814-821. 

The mechanical characterization indicated that the mortars with nano-titania showed increased compressive and flexural strengths and moduli of elasticity over time, when compared to the specimens without nano-titania The results also indicate enhanced carbonation and hydration of mortar mixtures with nano-titania. The hydrophylicity of nano-titania improves the humidity retention of mortars, thus facilitating the carbonation and hydration processes. This property can be exploited into the fabrication of mortars... 

In an attempt to maximize flexural properties, PP/VB composites were fabricated with the reinforcing preform layers selectively placed near the composite surfaces where the greatest tension / compression occurs during flexural loading. During the composite fabrication process, PP sheets of varied thickness were used in order to situate two preform layers just inside both composite surfaces. The tensile and flexural mechanical properties for a -<10 VB wt.% composite with such uneven fabric distribution are provided in Table II along with the properties for its... 

The mechanical properties of surfactant adsorption monolayers are characterized not only by the interfacial tension but also by the interfacial bending moment, which is proportional to the so-called spontaneous curvature of the interface. In addition, the variation of the interfacial bending moment with curvature is characterized by the curvature elastic moduli. These interfacial flexural properties are determined mostly by the interactions between the head groups and tails of the adsorbed surfactant molecules. In their own turn, the interfacial flexural properties influence phenomena and processes such as the formation of microemulsions, critical emulsions, holes in foam and emulsion Aims, fluctuation capillary waves, flocculation in emulsions, and so on see Sec. IV. 

Glass fiber reinforced composites based on epoxy-acrylate modified UPRs were studied [228]. The authors showed that UPRs, endcapped with acrylate groups and diluted with reactive multifunctional acrylic and allylic monomers in the presence of a photoinitiator, can be photocrosslinked with UV radiation as glass fiber laminates in a rapid process. It was found that the physical properties of the photo-crosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. A greater improvement of the tensile and flexural properties of the photocured products was observed for multifunctional acrylate or acrylether monomers added to the UPR (Table 31) than for allylic monomers. 

Takagi, H. and Asano, A. (2008) Effects of processing conditions on flexural properties of cellulose nanofiber reinforced green composites. Composites Part A, 39 (4), 685-689. 

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