Research and Implementation of Integrated Methods of Unsupported Printing and Five-Axis CNC Machining Technology

In traditional 3D printing, the best method for creating overhanging structures is to add supporting materials; however, this often leads to an increase in costs and a decrease in printing efficiency. Therefore, a five-axis CNC machining technology is introduced in this paper, proposing an unsupported 3D printing method. Models requiring support structures were supported by an existing supporting surface by adding two degrees of freedom (rotation and swinging). Moreover, effectiveness of the proposed method was verified by experiment

Cross-linked thermoplastics

Cross-linked thermoplastics represent an important class of materials for numerous applications such as heat-shrinkable tubing, rotational molded parts, and polyolefin foams. By cross-linking olefins, their mechanical performance can be significantly enhanced. This chapter covers the three main methods for the cross-linking of thermoplastics: radiation cross-linking, chemical cross-linking with organic peroxides, and cross-linking using silane-grafting agents. It also considers the major effects of the cross-linking procedure on the performance of the thermoplastic materials discussed

Crosslinked thermoplastics

Cross-linked thermoplastics represent an important class of materials for numerous applications such as heat-shrinkable tubing, rotational molded parts, and polyolefin foams. By cross-linking olefins, their mechanical performance can be significantly enhanced. This chapter covers the three main methods for the cross-linking of thermoplastics: radiation cross-linking, chemical cross-linking with organic peroxides, and cross-linking using silane-grafting agents. It also considers the major effects of the cross-linking procedure on the performance of the thermoplastic materials discussed

Low-Cost Inkjet-Printed Temperature Sensors on Paper Substrate for the Integration into Natural Fiber-Reinforced Lightweight Components

In a unique approach to develop a “green” solution for in-situ monitoring, low-cost inkjet-printed temperature sensors on paper substrate were fully integrated into natural fiber-reinforced lightweight components for which structural health monitoring is becoming increasingly important. The results showed that the sensors remained functional after the vacuum infusion process; furthermore, the integration of the sensors improved the mechanical integrity and stability of the lightweight parts, as demonstrated by tensile testing. To verify the qualification of the printed sensors for the target application, the samples were exposed to varying temperature and humidity conditions inside of a climate chamber. The sensors showed linear temperature dependence in the temperature range of interest (−20 to 60 °C) with a TCR ranging from 1.576 × 10−3 K−1 to 1.713 × 10−3 K−1. Furthermore, the results from the tests in humid environments indicated that the used paper-based sensors could be made almost insensitive to changes in ambient humidity by embedding them into fiber-reinforced lightweight materials. This study demonstrates the feasibility of fully integrating paper-based printed sensors into lightweight components, which paves the way towards integration of other highly relevant sensing devices, such as strain and humidity sensors, for structural health monitoring of smart, sustainable, and environmentally compatible lightweight composite materials

WATER DISPERSABILITY OF PAPERS– BALANCING MATERIAL STRENGTH AND DISPERSIBILITY

<p>Water- dispersability of papers is useful in various applications as it disintegrates into its fibers after usage, and also is a fully biodegradable material. In this work, we have first introduced a test for the disintegration performance of different paper grades. Based on that disintegration and comprehensive statistical analysis we have performed a quantitative analysis on the technological and physical mechanisms responsible for a good paper dispersibility in water. Regarding technological parameters for paper production, we identified lignin content, degree of refining and addition of starch as relevant factors reducing paper dispersibility. Addition of a debonding agent, a surfactant, was not found to be effective here. In order to clarify the physical mechanisms governing paper disintegration behavior we analyzed paper properties related to mechanical strength and water uptake. We found a strong correlation between wet- and dry tensile strength of paper, both of which were highly affecting the dispersibility. Water uptake in the network, or water uptake into the fibers (WRV), or fiber wetting (contact angle) were not, or only very moderately, related to paper dispersibility. The only water absorption related paper property correlated to the disintegration results was liquid penetration speed measured with ultrasonic testing. We are concluding that the same mechanisms that are creating dry strength – high density and strong fiber-fiber bonding – are also responsible for a bad disintegration behavior. Principal component analysis revealed that paper strength and water penetration speed are not governed by different latent variables but instead are all strongly associated with the first principal component. This suggests that the same mechanisms are responsible for reduction of water penetration speed and wet/dry strength. A future solution of the problem might thus be to decouple network strength and water penetration, e.g. by identifying suitable additives that impart bonding strength to the network without reducing the access of water to break the fiber-fiber bonds.</p&gt

Factors influencing the processing and technological properties of laminates based on phenolic resin impregnated papers

High quality decorative laminate panels typically consist of two major types of components: the surface layers comprising décor and overlay papers that are impregnated with melamine-based resins, and the core which is made of stacks of kraft papers impregnated with phenolic (PF) resin. The PF-impregnated layers impart superior hydrolytic stability, mechanical strength and fire-resistance to the composite. The manufacturing involves the complex interplay between resin, paper and impregnation/drying processes. Changes in the input variables cause significant alterations in the process characteristics and adaptations of the used materials and specific process conditions may, in turn, be required. This review summarizes the main variables influencing both processability and technological properties of phenolic resin impregnated papers and laminates produced therefrom. It is aimed at presenting the main influences from the involved components (resin and paper), how these may be controlled during the respective process steps (resin preparation and paper production), how they influence the impregnation and lamination conditions, how they affect specific aspects of paper and laminate performance, and how they interact with each other (synergies)

Characterization of Cellulose/Polyvinyl Alcohol/Expanded Graphite 3D Porous Foam and Adsorption of Methylene Blue

The cellulose/polyvinyl alcohol (PVA)/expanded graphite (EG) 3D porous foam, which has wide application prospects in cost-effective dye removal, was prepared by physical crosslinking and foaming technology. The prepared foam material has an obvious 3D network and porous structure, exhibiting excellent removal efficiency for methylene blue (MB) in an aqueous solution. The largest MB adsorption capacity of the foam is 110.81 mg/g. The adsorption process follows the pseudo-2nd order kinetics and the Freundlich isotherm model, indicating that the adsorption process is controlled by active surface sites and the physical adsorption process. Thermodynamic studies have shown that the adsorption process is a spontaneous and exothermic reaction. After five cycles of adsorption experiments, the composite material still exhibited a more than 70% dye removal rate. Results show that cellulose/PVA/EG 3D porous foam is an effective, promising, and recyclable adsorbent, which can be used to remove MB from aqueous solutions

Review on impregnation issues in laminates manufacture: opportunities and risks of phenol substitution by lignins or other natural phenols in resins

This article provides a general overview of the most promising candidates of bio based materials and deals with the most important issues when it comes to their incorporation into PF resins. Due to their abundance on Earth, much knowledge of lignin-based materials has already been gained and uses of lignin in PF resins have been studied for many decades. Other natural polyphenols that are less frequently considered for impregnation are covered as well, as they do also possess some potential for PF substitution