Search

A new kinds of waterborne polyurethane acrylate (WPUA) dispersions were synthesized based on isophorone diisocyanate (IPDI), hydroxyl‐terminated polybutadiene (HTPB), 1, 4‐butanediol (1, 4‐BDO), polytetramethylene ether glycol (PTMG), dimethylolpropionic acid (DMPA), 2‐ethylhexyl acrylate (EHA), and methyl methacrylate (MMA) as main raw materials. The influence of the HTPB content on the particle size, storage stability of the WPUA dispersions and the damping property of cured films were studied by using dynamic light scattering (DLS), dynamic mechanical analysis (DMA), respectively. It can be found the WPUA dispersions have a good stability and the damping temperature range of loss tangent (tan δ) >0.3 reaches a maximum (−26.6–79.14°C) when the content of HTPB is 20%. The HTPB based WPUA could be applied to damping material. [ABSTRACT FROM AUTHOR]

ABSTRACT Acrylic impact modifier (ACR), one kind of methyl methacrylate-butyl acrylate copolymer with a core-shell structure, was prepared by seed emulsion polymerization. The weight ratio of core-shell ranges from 85.5/14.5 to 71.9/28.1. Then PLA/ACR blends were prepared with a constant ratio of 80/20. The effect of core-shell ratio of ACR on toughening PLA was investigated. Torque analysis revealed that the torque values of PLA/ACR blends increased with increasing shell content of ACR. The impact strength of PLA/ACR blends reached the highest value of 77.1 kJ m−2 when the core-shell ratio of ACR was 79.2/20.8. Transmission electron microscope (TEM) photographs revealed that ACR was dispersed uniformly in the PLA matrix. Scanning electron microscopy (SEM) suggested that the plastic deformation and cavitations were the major toughening mechanism for the PLA/ACR blends. The shell partition PMMA of ACR was partially miscible with PLA from dynamic mechanical analysis. [ABSTRACT FROM AUTHOR]

A series of submicrometer-sized polybutadiene(PB) rubber particles with different diameters ranging from 100 to450 nm were prepared via an emulsion polymerization. Subsequently,core–shell polybutadiene-graft-polystyrene(PB-g-PS) particles were synthesized using a redoxinitiator system (cumene hydroperoxide and ferrous sulfate) by anemulsion grafting polymerization. Then the submicrometer sized PB-g-PS impact modifiers were utilized to toughen polystyrene(PS) by blending PS and high-impact polystyrene. From measuring mechanicalproperties, it was found that the notched impact strength of toughenedPS was significantly influenced by core–shell PB-g-PS particle size. When the rubber particle size was above 300 nm,the notched impact strength was 208 J/m, nearly 2 times than thatof toughened PS with particle size 100 nm. Moreover, the stress whiteningzones were observed by transmission electron microscopy, and the resultshowed that multiple crazing is its dominative toughening mechanism. [ABSTRACT FROM AUTHOR]

Maleic anhydride (MAH) functionalized acrylate-styrene-acrylonitrile(ASA) copolymers (F-ASA) were prepared via an emulsion polymerizationprocess. The F-ASA particles were used to toughen Polyamide-6 (PA-6).Molau tests showed the compatibilization reactions between PA-6 andF-ASA. The notched impact strength of PA-6 was effectively improvedby the use of F-ASA. At a rubber content of 20% by weight in PA-6/F-ASAblends, it was found that the impact strength increased with the MAHcontent. When the MAH content was 8% in F-ASA, the impact strengthwas 1008 J/m. The influence of rubber content on the properties ofPA-6/F-ASA8 blends was investigated. The results showed that brittle-ductiletransition took place when the rubber content was 20%. Moreover, increasingthe MAH content of the blends reduced the brittle-ductile temperatureof the F-ASA/PA-6 blends from 50 °C to about 0 °C. Scanningelectron microscopy (SEM) results showed that cavitation of rubberparticles and shear yielding of the PA-6 matrix were the major tougheningmechanisms. [ABSTRACT FROM AUTHOR]

Background: In the series of improved versions of U-Net, while the segmentation accuracy continues to improve, the number of parameters does not change, which makes the hardware required for training expensive, thus affecting the speed of training convergence., Objective: The objective of this study is to propose a lightweight U-Net to balance the relationship between the parameters and the segmentation accuracy., Methods: A lightweight U-Net with full skip connections and deep supervision (LFU-Net) was proposed. The full skip connections include skip connections from shallow encoders, deep decoders, and sub-networks, while the deep supervision learns hierarchical representations from full-resolution feature representations in outputs of sub-networks. The key lightweight design is that the number of output channels is based on 8 rather than 64 or 32. Its pruning scheme was designed to further reduce parameters. The code is available at: https://github.com/dengdy22/U-Nets., Results: For the ISBI LiTS 2017 Challenge validation dataset, the LFU-Net with no pruning received a Dice value of 0.9699, which achieved equal or better performance with a mere about 1% of the parameters of existing networks. For the BraTS 2018 validation dataset, its Dice values were 0.8726, 0.9363, 0.8699 and 0.8116 on average, WT, TC and ET, respectively, and its Hausdorff95 distances values were 3.9514, 4.3960, 3.0607 and 4.3975, respectively, which was not inferior to the existing networks and showed that it can achieve balanced recognition of each region., Conclusion: LFU-Net can be used as a lightweight and effective method in the segmentation tasks of two and multiple classification medical imaging datasets., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)