Effect of interaction from the reaction of carboxyl/epoxy hyperbranched polyesters on properties of feedstocks for metal injection molding

The purpose of this study is to improve the properties of the feedstocks and shape retention of debinded parts by the reaction between 17-4PH stainless steel powders. Carboxyl-terminated hyperbranched polyester (CTHP) and epoxy-terminated hyperbranched polyester (ETHP) were used to treat the powders, and termed as CTHP-m and ETHP-m with carboxyl and epoxy group, respectively. Comparing with pristine, CTHP-m and ETHP-m, feedstock prepared from equal amount of CTHP-m and ETHP-m (CTHP-m/ETHP-m) possessed more excellent properties. The experimental results showed that the critical solids loading, flexural modulus, density and melt flow index of CTHP-m/ETHP-m feedstock were 63.8 vol.%, 2800 Mpa, 5.06 g/cm3 and 62 g/10min, respectively, which were obviously higher than that of others. Also, the shape retention of CTHP-m/ETHP-m debinded parts was the best of all the samples. The improved properties of CTHP-m/ETHP-m feedstock were attributed to the powder interaction between CTHP-m and ETHP-m formed by the chemical reaction between epoxy and carboxyl group.

Flexible crosslinking of polyurethane using grafted poly(dimethylsiloxane) with Epichlorohydrin and Bisphenol A end groups and its impact on the mechanical properties and low-temperature flexibility

Poly(dimethylsiloxane) (PDMS) was grafted onto polyurethane (PU), and Epichlorohydrin and Bisphenol A were attached to the free ends of PDMS groups and used to link the grafted PDMS to thereby introduce flexible crosslinks between the PU chains. The flexible crosslinks enhanced the crosslink density and solution viscosity of PU but did not change the melting and crystallization behaviors of the soft segments of PU. In particular, the flexible PDMS crosslinks increased the maximum tensile stress by up to 300% and the maximum tensile strain up to 180%. The shape recovery capability at 10°C and the shape retention capability at −25°C were maintained above 90% with the flexible crosslinking. Grafted PDMS moderately improved the low-temperature flexibility of PU due to its flexibility at low temperature. The flexible crosslinks of grafted PDMS successfully improved the tensile strength, shape recovery, and low-temperature flexibility of the PU.

Interventional Status Awareness Based Manipulating Strategy for Robotic Soft Endoscopy

Traditional soft endoscopy is operated with naked eyes and use of hands. Robotic soft endoscopy frees the hands of endoscopists, which reduces the labor-intensity and complexity of operation and improves the operational accuracy of endoscope, but it’s hardly to be reliably performed because the operator lacks of situational awareness of endoscopic interventional status when the hands are detached from the endoscope. This paper first presents a method to perceive the interventional status of endoscope based on image processing, the interventional status includes insertion length and velocity. A manipulating strategy was designed according to the perceived endoscope interventional status and construction parameters of dual robotic arms in order to achieve reliable interventional endoscopy. Human phantom experiments are carried out to verify the effectiveness and feasibility of the proposed interventional status awareness method and manipulating strategy. The results show that the robotic soft endoscopy can be well performed with the ability of interventional status awareness and coordinated manipulation of dual arms. The perceived insertion length indicates the position of the tip of endoscope in human body and the designed manipulating strategy is effective in endoscopic shape retention and torque transmission.

Development of rapid set mortar for additive manufacturing

The study presents the development results of blended cement mortars for additive manufacturing. The goal was to achieve a balanced rheological behaviour of the fresh mixture through optimal granulometry, suitable grain shape and the choice of micro-admixtures. The article closely describes the granulometric and rheological characterization of the proposed ternary and quaternary blended mortar mixtures with various SCM’s. The print quality and shape stability of the promising mortars and the researched 3DP mixes were evaluated during incremental layering for comparison. The performed experiments confirmed that the mixtures containing blast furnace slag, quartz powder and metakaolin are more plastic and allow faster layering in height. The slaked lime-enriched mixture has excellent plasticity and is able to resist deformation during overlaying, the printed layers are without surface defects. The small addition of polypropylene fibre (0.08 wt.%) improves the plasticity and shape retention ability.

Impact of abrasion on strength, elasticity and elastic recovery properties of stretch-denim fabric

PurposeIn recent times, the usage of elastane-containing denim garments has increased, as it provides fit and comfort both at the same time. The purpose of the study is to understand the effect of abrasion on the durability of comfort related to body movement and shape retention property of the stretch-denim fabric.Design/methodology/approachThe paper investigates the effect of abrasion on the initial tensile properties, recovery and resilience properties of the stretch-denim fabric. Further, to analyse the effect of the composition of the elastane yarn, three different types of elastane yarns having different types of sheath (covering) fibre, structure and different levels of elastane content have been used in the weft.FindingsThe comfort related to body movement and the shape retention properties of the stretch-denim fabric got affected due to abrasive damage. The elastane yarn composition and structure played an important role in determining the extent of the change in such properties during abrasion. The fabric with a higher level of elastane content suffered a greater loss in shape-retention properties due to abrasion. The extent of mass loss in stretch-denim fabric does not always correlate to the extent of loss in the comfort and shape-retention properties.Originality/valueMost of the earlier studies have investigated the effect of abrasion on the durability aspect of the stretch-denim fabric. In a practical scenario, the stretch-denim garments are rarely discarded due to tearing or change in appearance but mainly due to bagging, i.e. distortion in shape after usage. Thus, the study on the combined effect of the abrasion and cyclic loading on the comfort and shape-retention properties will help to predict the performance of the apparel during usage.

Determination of Material Requirements for 3D Gel Food Printing Using a Fused Deposition Modeling 3D Printer

The material requirements for printing gel food with a fused deposition modeling 3D printer were determined based on fidelity, shape retention, and extrudability, as described by the rheological parameters of storage modulus (G’), yield stress (τ0), and phase angle (δ). The material requirements were determined for printing gel food using three formulations containing gelatin, gelatin and pectin, and gum mixture as the gelling agents. As compared with formulations based on gelatin alone, pectin-containing gelatin-based formulations yielded higher δ and lower G’ and τ0 values, while gum mixture-based formulations formed a gel with higher G’ and δ values and a wider range of τ0. Overall, this study presents quantitative material requirements for printing gel products containing gelatin, gelatin–pectin, and gum mixtures.