Autoclave process development

Abstract This chapter discusses the state-of-the art of autoclave processing of polymer composites. First, the architecture and typical formulation of a process model applied to the autoclave process is presented. Then, the steps for autoclave process development using the proposed modelling approach are discussed. In particular, the thermal management during the process and the dimensional control of the final part are reviewed in more detail. 

Most commercial tellurium is recovered from electrolytic copper refinery slimes (8—16). The tellurium content of slimes can range from a trace up to 10% (see Seleniumand selenium compounds). Most of the original processes developed for the recovery of metals of value from slimes resulted in tellurium being the last and least important metal produced. In recent years, many refineries have changed their slimes treatment processes for faster recovery of precious metals (17,18). The new processes have in common the need to remove the copper in slimes by autoclave leaching to low levels (<1%). In addition, this autoclave pretreatment dissolves a large amount of the tellurium, and the separation of the tellurium and copper from the solution which then follows places tellurium recovery at the beginning of the slimes treatment process. 

Atlanta, Ga., 26th-30th April 1998, p. 1842-9. 012 PRODUCT AND PROCESS DEVELOPMENTS IN THE NITROGEN AUTOCLAVE PROCESS FOR POLYOLEFIN FOAM MANUFACTURE Eaves D E Witten N Zotefoams pic (SPE)... 

A review is presented of the nitrogen autoclave process for the manufacture of crosslinked polyolefin foams. Process and product developments over the last few years are summarised and future possibilities are described. Process developments include use of higher temperatures and pressures to produce foams having densities as low as 10 kg/cub.m. Product developments include foams based on HDPE/LDPE blends, propylene copolymers and metallocene-catalysed ethylene copolymers. The structure and properties of these foams are compared with those of foams produced by alternative processes. 5 refs. 

Autoclave processing is a process in which individual prepreg plies are laid up in a prescribed orientation to form a laminate (Fig. 5.9). The process involves consolidation of the laminate, which generally results in a three-dimensional flow field. Similar to the IP process the fiber bed is not stationary in the AP process hence, its movement has to be specifically considered when the appropriate conservation equation for this process are developed. If it is assumed that the resin has a relatively constant density (i.e., the excess resin is squeezed out before the gel point is reached) then the appropriate conservation of mass equation for this consolidating system is Equation 5.12. 

Several viscosity and kinetic models, and experimental procedures for developing these models, are available for a number of commercially available resin systems [1-5]. These models allow insight into autoclave process decisions based on changes in resin viscosity and kinetic behavior and can be used to determine hold temperatures and durations that allow sufficient resin flow and cross-linking to avoid over bleeding, exotherms, and void formation. 

Heat transfer models are a powerful tool for developing autoclave process cycles. They are especially useful in aiding tool designers in choosing tooling materials, thicknesses, and thermocouple locations. Models can also be used to determine if a tooling concept would be detrimental in a specific position in the autoclave and the types of tools that should be processed together to optimize the cure cycle. 

Data showing survival on some but not all of the Bis may be valuable in process development (particularly in the development of sterilization specifications and sterilizer parameters for porous and equipment loads), but would likely raise issues at regulatory inspection. The inference taken from having some survival could be that each item in the autoclave load is not being exposed to the same treatment. 

Hydrothermal liquefaction is a process for the conversion of biomass into an organic product oil. It has been widely studied in the early 1980 s (see the recent extensive literature survey in [1]), Starting in 1983 Shell Research performed process development based on experiments in autoclaves and a continuous bench scale unit. This resulted in a conceptual design for the HTU process including cost estimate [2,3]. The work was discontinued in 1988. 

The sterilization of components and equipment will be validated for each load configuration using the cGMP autoclave. Cycle Development Testing and Performance Qualification Testing will qualify each sterilization process. A separate Performance Qualification and Cycle Development Testing Report will be written for each load configuration. The process will be considered validated when the acceptance criteria is met for three (3) successful consecutive runs. 

The objectives of the process design and optimisation stages of product development have been discussed in chapter 8, Product Optimisation . For ophthalmic products, like parenterals, process development can be quite challenging because the formulation must be manufactured sterile. Quite often, it is discovered that some formulations cannot withstand a stressful sterile process such as autoclaving. Chemical degradation or changes to the formulation properties of multiphase systems, such as suspensions and gels, can occur. In all cases, the compendial sterility test requirements described in the various pharmacopoeias must be complied with. 

As we related in the introduction to Appendix A, this patent should be read by everyone involved in research and process development using supercritical fluids. In his examples, Zosel describes results on neat solubility, separations of liquids and solids, fractionations, etc. A wealth of information is given on the performance of various gases, e.g., ethylene, ammonia, ethane, carbon dioxide, in dissolving a variety of compounds. Several interesting experiments carried out in a plexiglass autoclave are descrited, and certain phase separations are noted. Some of the information can be found in other references, of course, but not in such succinct form. It is of pedagogical value to reproduce one of the examples here. 

The PLATSOL M treatment of a nickel rich concentrate and a pyrrhotite 3 cleaner concentrate was demonstrated. The PLATSOL autoclave process was combined with precious metal precipitation, copper concentrate enrichment, copper removal, iron/aluminum removal, mixed hydroxide precipitation of nickel and cobalt and finally magnesium removal. The copper concentrate enrichment process proved to be a novel addition to the NorthMet flowsheet. The copper in solution from the autoclave processing was recovered by metathesis on the copper concentrate in the enrichment process. The solvent extraction and electrowinning of copper process applied to precious metal free PLATSOL solutions is no longer required by using this metathesis process route. This development provides maximum operational flexibility for treatment of the NorthMet ore. 

Three common concerns when developing an autoclave process for a specific component in the aerospace industry are (1) to meet the cure cycle specification, that is, to ensure that all regions of the component are experiencing... 

Abstract Traditional autoclave curing technology has its own limitations which has motivated many researchers and industries to consider an out-of-autoclave (OoA) alternative. Since the last couple of decades number of autoclave substitutes have been developed and demonstrated by the technologists around the globe. This chapter provides information on most of the OoA technologies that are used on the industrial and lab scale. These technologies are compared with the conventional autoclave process and their merits and demerits are also illustrated. Expectations of the composite industry from such technologies have been presented at the end of this chapter. 

Although being a relatively old technology to process composites, the autoclave technique is still a matter of research. Besides the previously mentioned microwave development, research is being conducted to simulate the autoclave process and to derive models for time-based cost calculations [5,6]. In addition, efforts are being undertaken in the field of tooling and the effect of the tool on the part quality [7,8]. 

The driving force for developing ethylene polymerization in a loop reactor was problems encountered in the autoclave process with fouling and related problems with heat removal. In the loop process two important features support effective heat removal the high surface-to-volume ratio offered by the pipe and the turbulent flow... 

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