China
Africa
Explore chapters and articles related to this topic
Silicones
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Robert Perry, Clay Quinn, Frank Traver, Kedar Murthy
Silicone fluids are also used extensively as release agents in a variety of molding operations. They are desirable because of their resistance to high temperature, smoking, and fuming; and the small amount of product needed offsets their higher price.
Manufacturing Processes
Published in Ever J. Barbero, Introduction to Composite Materials Design, 2017
Ever J. Barbero, Ever J. Barbero
The mold preparation is one of the most critical steps in the layup process. The mold may be made of wood, plaster, plastics, composites, or metals depending on the number of parts, cure temperature, pressure, etc. Permanent molds, used for long runs, are made of metals. Molds made of composites are mostly used for low volume production since they do not respond well to repeated use. The mold may be male or female type, depending on which surface needs to be smooth. A coating of release agent is applied to the mold to facilitate the removal of the finished part. The release agents in common use are wax, polyvinyl alcohol, silicones, and release papers. The choice of the release agent depends on the type of material to be molded and the degree of luster desired on the finished product.
Moulds
Published in M. Levitt, Precast Concrete, 2014
The main purpose of a release agent is to stop/inhibit the concrete from sticking to the mould and is a general requirement except, possibly, for wet-cast concrete in PVC-lined or individual moulds and for moist mix design cast stone in timber moulds. All that is theoretically required to debond the concrete/mould interface is a monomolecular-thick layer but this is not possible due to practical reasons of application as well as mould texture. However, it points to the necessity of being as frugal as possible in application as generosity does not result in improved release and commonly leads to retardation of hydration as well as staining. In order to deal with over-application, it is often of benefit to allow the excess release agent to collect in the corners of the mould and rag off the excess. Alternatively, apply the agent with an oil-wet rag.
On the sensitivity of bondline control specimens with respect to the detection of adhesion defects
Published in The Journal of Adhesion, 2023
Lennert Heilmann, Michael Hoffmann
In order to fabricate adhesive bonds with defects that are homogeneous with respect to their areal distribution and severity, the pretreated substrate panels were contaminated with silicone-containing release agent. This was carried out with a dip-coater of the type RDC 21-K from Bungard Elektronik GmbH & Co. KG. During the contamination procedure, the substrate to be contaminated is immersed vertically in a solution of the contaminant at a constant speed and, after a specified dwell time, is pulled out at a constant speed. During the extraction, the solvent on the substrate panel evaporates so that a homogeneous film of the contaminant is deposited. The reinforcement fibres of the panels were oriented in parallel to the direction of movement; the dipping process was carried out with an immersion speed of 150 mm/min, a dwell time of 15 s and a pull out speed of 30 mm/min.
Investigation into mechanical & tribological performance of kenaf fibre particle reinforced composite
Published in Cogent Engineering, 2018
Alvin Devadas, Umar Nirmal, J. Hossen
A two-part epoxy resin was used as polymer matrix. Auto-Fix 1710A and its hardener Auto-Fix 1345B epoxy resin was purchased from Bonding Technology Resources Sdn. Bhd., Malaysia had been used to develop the kenaf fibre particle reinforced epoxy (KPafRE) composites. The epoxy was in liquid form with density 1100kg/m3 and viscosity 15,000 mPa.s (properties at 25°C) and it is generally used in various applications such as automotive, yacht and other composite component fabrication. First, Auto-Fix 1710A epoxy resin was mixed with 5 %wt. of kenaf fibre particles by means of an electrical stirrer before hardener was added with ratio of 1:1 to the resin. A closed mould with a dimension of 200 mm × 100 mm × 20 mm was used in the preparation of the composite by means of hand layup method. The inner surfaces of the mould were sprayed with a thin layer of silicone as a release agent. When the mould was completely filled with the mixture, it was covered with a steel plate and a pressure of 5 kPa was applied as to force out the trapped air. Keeping the pressure intact, the composite block was cured for 24 h at room temperature (28 ± 2°C). The hardened composite was removed from the mould and post cured in an oven at 80°C for one hour for complete curing. Similar method was used to fabricate other composites with 10, 15 and 20%wt. of kenaf fibre particles. For comparison purpose, the results will be compared with Neat Epoxy (NE).
Thermal energy management in buildings and constructions with phase change material-epoxy composites: a review
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Tejashree Amberkar, Prakash Mahanwar
The phase transition temperature of neopentyl glycol (NPG) is suitable for low-temperature building applications. Volatilization of solid-solid PCM NPG can be prevented, and their TES capacity can be retained for longer duration by physical blending of NPG and Bisphenol A type of epoxy resin E-44 (Meng et al. 2020). The procedure for preparing PCM-epoxy composite can be explained as follows. NPG was dissolved in anhydrous ethanol. Dissolved solution was subjected to infrared (IR) radiation to volatilize solvent. The obtained product was ground with mortar. Epoxy and ground NPG were dried at 50°C for 2 hours. NPG and acetone were mixed and subjected to heating at 250°C. The mixture containing equal-weight percentages of NPG and epoxy was stirred. The curing agent was added in 20% amount, and the mixture was further agitated. Then the mixture was poured into a steel mold with a release agent. Mold was vacuumed for two hours and cured for 96 hours at room temperature (RT). The mold was heated at 65°C for 1 hour to remove acetone and cooled to RT. The sample was demolded. Anhydrous ethanol was flushed in the composite several times until the surface was clear. Then the sample was dried in the oven to volatilize ethanol. FTIR and SEM confirmed the physical encapsulation of NPG. SEM morphology of epoxy and NPG-epoxy composite is given in Figure 7. It stated the pore size distribution of composite, where NPG particles accumulate, in the range of 0.5 to 12.5 µm. Such small pores prevent leakage of less viscous phase-transformed NPG. The incorporated quantity of NPG was 50%, whereas the quantity calculated from enthalpy calculation in DSC analysis was 49.6%. The enthalpy values suggested negligible loss of NPG in the preparation procedure. The composite showed volatilization loss of 0.1% at 60°C and 6.5% at 100°C. Enthalpy loss due to thermal cycling was 1.8% which is negligible. The composite possesses TES capacity at 41°C, which is useful for preparing thermal buffering sheets for building envelopes. Building materials should have good TES property for a few decades. Such long duration of operation requires a matrix with excellent leak-proof characteristics and thermal cycling stability. Epoxy provides these characteristics relentlessly for a long duration.