Vacuum casting method

Pouring liquid metal into the mold requires a steady hand and constant attention. When the mold containing liquid metal is placed in a centrifuge, hot metal can fly out of the centrifuge. This is why it is preferable to use the vacuum casting method, for which a centrifuge is not needed. 

One essential difference between casting and molding processes is that pressure need not be used in casting (although large-volume, complex parts can be made by low pressure and/or vacuum casting methods). Another difference is that the starting material is usually in liquid form rather than the usual solid plastic used in other processes. There is also the difference that the liquid could be a monomer rather than the plastic used in most other processes and in turn the monomer is converted to a polymer/plastic (Chapter 1). 

Vacuum castings, the more basic processes, such as vacuum casting in silicone molds, also have their place and a range of gun-applied TS polyurethane resins introduced by Axson, France, avoids the need even for the casting machine. Martello Design has developed a polyurethane injection process, Thin-RIM, complementary to its existing vacuum casting method, which allows features and wall sections down to 0.5 mm to be produced. 

The method of choice for the preparation of Pu metal on the multigram to kilogram scale is metallothermic reduction of PUF4 or PUO2 by Ca metal (69), followed by electrorefining with TaC electrodes and vacuum casting. This method produces metal 99.9 at % pure. An... 

In this chapter we investigate and discuss the thermal, optical, electrical properties of the oligothiophene derivatives by means of differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and UV-Vis spectroscopy. The thin films of these compounds produced by solution cast and vacuum deposition methods are characterised by AFM measurements in contact and non-contact mode, and by X-ray diffraction. Finally, an ultra-thin OFET is built, and the transistor characteristics are determined. 

The oligothiophene films were prepared by solution cast methods and by vacuum deposition. Depending on the cast procedure, different layer thicknesses could be achieved. Preparation from solution either by drop casting or spincoating resulted in films ranging from 50 nm to 200 nm in thickness. Vacuum sublimation yielded very thin layers in the range of 10 nm to 15 nm, which nevertheless allowed to build-up and operate an OFET structure of molecular thickness as demonstrated in this chapter. 

The advantages of this sintering method, when compared to solvent casting methods used in previous studies, include (i) elimination of shrinkage, (ii) elimination of the need for potentially expensive scale-up steps such as vacuum drying, (iii) reduction of processing time (slabs have been produced in 2 h, compared to 4 days required for solvent casting), and (iv)... 

The films of PBS, PEO and the binary blend of PBS/PEO were prepared by solution casting method. Pure PBS and PEO films with thickness of 200 10 pm were laminated together under pressure of 5 Mpa to obtain the bilayered film, and then used for preparation of gradient film. The laminated PBS/PEO film was annealed at 140 °C for 24 hours in an oven in the vacuum condition. By this way, we could generate a continuous gradient structure in the thickness direction, which is difficult to achieve by a conventional stepped multi-layer process. 

The films of pure P(BA-co-BT), pure PEO, binary blends P(BA-co-BT)/TDP(92/8 wt%/wt%) and PEO/TDP (92/8 wt%/wt%), and the ternary blend of P(BA-co-BT)/PEO/TDP containing a constant composition(8wt%) of TDP with various P(BA-co-BT)/PEO ratios were prepared by conventional solution casting method. 5wt% Polymer solution in 1,4-dioxane was stirred for 6-8 h and cast on a Teflon dish. The solvent was allowed to evaporate slowly for 1 day at ambient temperature. The resulted films were then dried in a vacuum oven at 50 °C for 2 days to remove residual solvent and subsequently compression molded between Teflon sheets for 3 min at 160 °C under pressure of 5MPa by using laboratory press (Mini Test Press-10, Toyoseiki Co., Japan). 

The bis-cyclometaUated complex Pt(N -thpy>2 28 (thpyH = 2-thien-2-ylpyri-dine), reported by von Zelewsky in the mid-1980s [44], was one of the first clear-cut examples of a simple platinum(ll) complex that phosphoresces in fluid solution at room temperature (2 ,ax = 578 nm, x = 2.2 ns in a PrCN/MeCN mixture) [45]. Barigelletti et al. showed, by means of a study of the temperature dependence of emission, that the influence of cyclometallation is to displace the d-d state to about 3,700 cm above the emissive state, ensuring that thermally-activated non-radiative decay is blocked off [46]. Although not thermally stable and hence not suitable for vacuum deposition methods of OLED fabrication, this complex and the trimethylsilyl derivative 29 has been incorporated into devices by spin-casting with TPD as a host material, and an EL efficiency of 11.5% has been achieved with 29 [47,48]. 

Vacuum casting n. A method used for casting fluid thermosetting resins to avoid inclusions of air bubbles. The mold is placed in a vacuum chamber and filled with resin from an external hopper. Vacuum is applied to pull out bubbles, held until they have all risen to the surface, then released. Curing follows. 

See table 2.1 for methods of analysis. Prepared in a W crucible and only vacuum cast. ... 

Gilmore et al. reported the preparation of a blend of cellulose acetate esters and P(3HB-co-3HV) copolymer using a solvent-casting method. P(3HB-C0-3HV) copolymer and cellulose acetate esters were dissolved separately in chloroform and then dried under vacuum. Lotti and Scandola reported the preparation of a blend of cellulose acetate butyrate and P(3HB-co-3HV) copolymer whereby the components were mixed in an injection molding machine. The temperature was kept low in order to minimise the thermal degradation of P(3HB-co-3HV) copolymer. 

Mixture samples were prepared by solution casting method with toluene as a solvent. First, predetermined amounts of block copolymers and PS homopolymers were dissolved in toluene with the addition of 0.3 wt% antioxidant (Irganox 1010, Ciba-Geigy Group). The solvent was slowly evaporated at ambient condition for 3 weeks, and then in a vacuum oven at 56V for 3 days. Finally, all the samples were annealed in a vacuum oven at I30T for 3 days. 

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