Synthesis and Characterization of Novel Segmented Castable Polyurethanes Based on 2,4-TDI and 3,5-DMTDA

2010 ◽  
Vol 29-32 ◽  
pp. 675-681 ◽  
Author(s):  
Xiao Dong Chen ◽  
Tie Jun Ma ◽  
Hai Zhang ◽  
Rong Sheng Chen
Keyword(s):  
Microphase Separation ◽  
Dynamic Properties ◽  
Testing Machine ◽  
Toluene Diisocyanate ◽  
Test Results ◽  
Polyurethane Elastomers ◽  
Soft Phase ◽  
Irregular Shapes ◽  
Soft Segments

A series of three castable polyurethane elastomers were prepared from 2,4- toluene diisocyanate (TDI) and 3,5-dimethyl-thioltoluenediamine (DMTDA) chain extender, with polyethylene adipate (PEA), polyoxytetramethylene glycol (PTMG) and polycaprolactone (PCL) soft segments. The polyol molecular weight employed was 2000g/mol. The polyurethane elastomers were characterized by an electronmechanical universal testing machine, a LX-A Shore durometer and a Dynamic Mechanical analyzer (DMA). In addition, fractured surface of the polyurethane elastomers was investigated by a field emission scanning electron microscopy (FE-SEM). The test results showed PCL based elastomer exhibits the excellent tear and stress-strain properties that polyester based elastomers offer, while retaining superior resilience similar to polyether based elastomers. The static and dynamic properties of PCL based elastomer were more suitable for dynamic applications. SEM micrographs of all polyurethane samples indicated the existing of microphase separation structure. Particles of the dispersed phase formed by hard phase and crystalline part of the soft phase grow bigger with increasing crystallinity of the soft segments. The hard domains are irregular shapes and with size of a few micrometers.

Synthesis and characterization of polydimethyl siloxane-based polyurethane elastomers using toluene diisocyanate

2014 ◽  
Vol 47 (8) ◽  
pp. 669-680 ◽  
Author(s):  
Khalid Mahmood Zia ◽  
Waseem-ul-Arifeen ◽  
Muhammad Ashair Iqbal ◽  
Mohammad Zuber ◽  
Muhammad Ishaq ◽  
...  
Keyword(s):  
Toluene Diisocyanate ◽  
Synthesis And Characterization ◽  
Polydimethyl Siloxane ◽  
Polyurethane Elastomers

Influence of Diisocyanates on Dynamic Mechanical Properties of Castable Polyurethane Elastomers

2012 ◽  
Vol 217-219 ◽  
pp. 563-566
Author(s):  
Xiao Dong Chen ◽  
Yu Hua Yi
Keyword(s):  
Mechanical Properties ◽  
Dynamic Mechanical Analysis ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Toluene Diisocyanate ◽  
Diphenylmethane Diisocyanate ◽  
Analysis Method ◽  
Polyurethane Elastomers ◽  
Dynamic Mechanical ◽  
Soft Segments

A series of castable polyurethane elastomers, based on polytetramethylene glycol as soft segments and toluene diisocyanate, 4, 4’-diphenylmethane diisocyanate, P-phenylene diisocyanate as diisocyanates respectively, were synthesized. The dynamic mechanical analysis method was utilized to determine tan delta property (tanδ). Also the influence of diisocyanates on the dynamic mechanical properties of castable polyurethane elastomers was analyzed. It can be concluded that the P-phenylene diisocyanate system elastomers have the most excellent dynamic mechanical properties.

Optimization and characterization of flavonoids extracted from Cannabis sativa fibers

2021 ◽  
pp. 004051752110277
Author(s):  
Qilu Cui ◽  
Jiawei Li ◽  
Chongwen Yu
Keyword(s):  
Chemical Structure ◽  
Cannabis Sativa ◽  
Ethanol Concentration ◽  
Extraction Process ◽  
Test Results ◽  
Hemp Fiber ◽  
Hemp Fibers ◽  
Structure Surface ◽  
Degumming Process

In this paper, the extraction process of flavonoids from hemp fibers was studied. Response surface methodology (RSM) analysis of the extraction parameters indicated that optimized results would be ethanol concentration 76 vol.%, bath ratio 1:50, and reaction time 139 min; therefore, an optimal extraction rate of flavonoids of 0.2275% can be obtained. The chemical structure, surface morphology and element composition of flavonoid extracts were analyzed. The test results indicated that hemp extract contains flavonoids, which can be used to extract flavonoids from hemp fiber, so as to comprehensively develop hemp fiber and reduce the discharge of waste liquid in the traditional degumming process.

scholarly journals Design and Experimental Characterization of L-CADEL v2, an Assistive Device for Elbow Motion

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5149
Author(s):  
Marco Ceccarelli ◽  
Mykhailo Riabtsev ◽  
Axel Fort ◽  
Matteo Russo ◽  
Med Amine Laribi ◽  
...  
Keyword(s):  
Elderly People ◽  
Operating Performance ◽  
Assistive Device ◽  
Test Results ◽  
Experimental Characterization ◽  
Elbow Motion ◽  
Laboratory Prototype

An experimental characterization is presented for an improved version of a wearable assistive device for elbow motion. The design is revised with respect to requirements for elbow motion assistance, looking at applications both in rehabilitation therapies and exercising of elderly people. A laboratory prototype is built with lightweight, portable, easy-to-use features that are verified with test results, whose discussion is also provided as a characterization of operating performance.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

scholarly journals Engineering nucleosomes for generating diverse chromatin assemblies

2021 ◽  
Author(s):  
Zenita Adhireksan ◽  
Deepti Sharma ◽  
Phoi Leng Lee ◽  
Qiuye Bao ◽  
Sivaraman Padavattan ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Dna Nanostructures ◽  
Macromolecular Assemblies ◽  
Maximum Resolution ◽  
Different Types ◽  
Chromatin Structural ◽  
Dna Fragment

Abstract Structural characterization of chromatin is challenging due to conformational and compositional heterogeneity in vivo and dynamic properties that limit achievable resolution in vitro. Although the maximum resolution for solving structures of large macromolecular assemblies by electron microscopy has recently undergone profound increases, X-ray crystallographic approaches may still offer advantages for certain systems. One such system is compact chromatin, wherein the crystalline state recapitulates the crowded molecular environment within the nucleus. Here we show that nucleosomal constructs with cohesive-ended DNA can be designed that assemble into different types of circular configurations or continuous fibers extending throughout crystals. We demonstrate the utility of the method for characterizing nucleosome compaction and linker histone binding at near-atomic resolution but also advance its application for tackling further problems in chromatin structural biology and for generating novel types of DNA nanostructures. We provide a library of cohesive-ended DNA fragment expression constructs and a strategy for engineering DNA-based nanomaterials with a seemingly vast potential variety of architectures and histone chemistries.

scholarly journals Multi-Scale Study of The Small-Strain Damping Ratio of Fiber-Sand Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2476
Author(s):  
Haiwen Li ◽  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Dynamic Properties ◽  
Wide Spectrum ◽  
Damping Ratio ◽  
Polypropylene Fiber ◽  
Small Strain ◽  
Treatment Method ◽  
Fiber Content ◽  
Polypropylene Fibers ◽  
Test Results ◽  
Fiber Reinforced

The use of polypropylene fibers as a geosynthetic in infrastructures is a promising ground treatment method with applications in the enhancement of the bearing capacity of foundations, slope rehabilitation, strengthening of backfills, as well as the improvement of the seismic behavior of geo-systems. Despite the large number of studies published in the literature investigating the properties of fiber-reinforced soils, less attention has been given in the evaluation of the dynamic properties of these composites, especially in examining damping characteristics and the influence of fiber inclusion and content. In the present study, the effect of polypropylene fiber inclusion on the small-strain damping ratio of sands with different gradations and various particle shapes was investigated through resonant column (macroscopic) experiments. The macroscopic test results suggested that the damping ratio of the mixtures tended to increase with increasing fiber content. Accordingly, a new expression was proposed which considers the influence of fiber content in the estimation of the small-strain damping of polypropylene fiber-sand mixtures and it can be complementary of damping modeling from small-to-medium strains based on previously developed expressions in the regime of medium strains. Additional insights were attempted to be obtained on the energy dissipation and contribution of fibers of these composite materials by performing grain-scale tests which further supported the macroscopic experimental test results. It was also attempted to interpret, based on the grain-scale tests results, the influence of fiber inclusion in a wide spectrum of properties for fiber-reinforced sands providing some general inferences on the contribution of polypropylene fibers on the constitutive behavior of granular materials.

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