Cured Sheets

Mechanical properties - Samples were cured in a Wickert laboratory press (WLP 1600/5 4/3) at a pressure of 100 bar (10 MPa) for the duration of lstress-strain properties of the cured samples were measured on a Zwick Z020 tensile tester according to ISO-37 type 2. 

The cured sheets were conditioned at 23 °C and 50% relative humidity. MIT folding endurance was run on 1.5-cm wide strips at 0.5 kg load. Tensile was taken on the same width strip. Eight strips were run machine direction and eight cross direction. As mentioned by Raff et al. (4,5), standard deviation and coefficient of variation were increased greatly in the treated plasticized paper for example untreated Foldur Kraft gave ... 

Specimens of Class PS (gasket type materials, preformed seals) elastomers were obtained as vulcanized, post-cured sheets, approximately 0.18 cm in thickness, from their manufacturers with the exception of silicone rubbers I and J which were supplied as calendered rolls requiring a 4 h bake at 200 C before using (Table I). 

In another study, the ground reclaim rubber was blended with stirene-butadiene rubber and cured under pressure at 160°C. The cured sheets were silica-reinforced by soaking in tetraethyl ortho silicate, then in an aqueous solution of n-butyl amine catalyst, followed by heat treatment at 50°C. The tensile properties of the blends containing conventionally incorporated silica, with no coupling agent, were superior to those containing silica incorporated by the sol-gel reaction [21]. 

For dielectric studies circular discs with a diameter of 12 mm were cut out from the cured sheets of composites. These studies were carried out using a HP impedance analyser model 4285 A in the frequency range of 100 kHz to 8 MHz by varying the temperature from 30 °C to 120 °C. The samples were inserted between two copper plates of the same diameter to form a capacitor in a homemade dielectric cell. The dielectric permittivity of the sample was calculated using the relation ... 

Two characteristics that make syntactic foam an efficient buoyancy material are high compressive strength and low density. The low density of the syntactic foam allows buoyant lift to be designed into the insulation system. As an example, Cuming Microwave Corporation makes a series of syntactic foams (low loss dielectric as well as treated lossy materials), which are ultralight and high strength and can be adjusted to specifications. These materials are available in different forms uncured, pack-in-place, cured sheet, and molded to shape. The pack-in-place variety has the consistency of a snowball, which can be readily packed into complex shapes. 

Mathai et al. cut circular specimens from sulfur-cured sheets of NR/NBR (34% ACN content) and immersed them in bottles of toluene at constant temperature until periodic weighing showed that equilibrium swelling had been attained. The toluene uptake of the rubber vulcanizate was increased by increasing the NR weight percentage in the blend (cf. Figure 9.2). This is in accordance with the inherent solvent resistance performance of NBR. The sorption behaviour of the same blend was tested for various types of penetrants... 

The mechanical properties were measured in accordance with ISO 37. The tensile tests were carried out using a Zwick 1435 Universal Testing Maschine with the cross-head 500 mm/min. The samples had the standard dumbbell shape. The micro structure of the vulcanizates surface was observed by scanning electron microscopy (SEM) LEO 1530 Zeiss. The samples of cured sheets were fixed on the sample holder, then gold-coated and secondary electron images were recorded. 

A Class B, zero shrink, high reacitivty polyester resin designed to be compression moulded at 137 - 155 C, as in the manufacture and use of fast cure sheet moulding compounds. Finds automotive as well as structural/industrial applications. 

The dispersion of type N-330 carbon black and of type N-326 carbon black into natural rubber (SMR 5CV) was investigated. In each case, the freshly mixed composition was press cured, razor cut, and microscopically examined to visually estimate the degree of carbon black dispersion as expressed by a dispersion rating (DR). Cured sheets of each composition were also tested with respect to ultimate tensile strength and other performance-related properties. The test recipes are given in Table 1. We note here that the uncured compositions can also be examined for dispersion quality (discussed later). 

Stamping out of gaskets from cured sheet rubber 20-40% waste... 

Polyisoprene with regular ingredients was mixed and different mixes containing varied carbon black (0 to 100 phr at the interval of 20) were made. A thin uncured layer of the mix was prepared by pressing it between the mylar sheets in the hydraulic press. The inner surfaces of the mylar sheets were coated with PVA for easy removal of the layer. All these uncured thin layers of different mixes were stacked sequentially with increasing/decreasing amount of carbon black in each layer. The stack as a whole was kept in the mould and compression molded at 150° C for 15 min. in a hydraulic press to get a cured sheet with... 

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