Post cure oven

For optimum properties, all pultruded sections will require post curing and care must be taken to ensure adequate support along the entire pultruded length to prevent deformation occurring in the post cure oven. 

Anti-clockwise helically wound inner layer 

Studies with the hybrid pultrusion of glass and carbon at the University of Mississippi have shown that the flexural stiffness of a glass/epoxy composite could be significantly improved by the addition of carbon fiber, symmetrically distributed at the outer surfaces of the composite beams, but perhaps this is not surprising, since the glass occupies the neutral axis. 

a Japanese company, has developed a machine which will pultrude curved L and T stiffeners, but it is slow. 

---

Ageing ovens are similar in nature to post-cure ovens requiring very accurate temperature control systems and monitoring for volume throughput of circulating air to ensure compliance with the requirements of specification testing. 

Post-cure ovens may be used to help complete the cure cycle, especially to control gradual cooling of the molded part. 

Microcellular crumbs can be used in considerable quantity along with china clay and whiting to reduce the product cost. Higher proportions of stearic acid (5-10 phr) are normally used in microcellular compounds in order to bring down the decomposition temperature of DNPT type blowing agents (see Appendix AlO). Post-cure oven stabilization of the microcellular sheets, typically at 100°C for 4 h, reduces the delayed shrinkage after cure to a minimum. 

Mold temperatures vary between 150 and 200°C, depending on the molding methods and part size. Parts can be molded in 1.5-10 min depending on the configuration and thickness of the part, the mold temperature, and the desired state of cure at demolding. Since most ethylene-acrylic parts are post-cured, it is sometimes possible to demold partly cured articles and complete vulcanization in the post-curing oven. 

After the building process, the component is fully polymerized in a post-curing cabinet (post curing oven) and is freed from the supports. Process variants use nozzles to apply the material and polymerize with high energy lights or using a DTP projector. They often use supports from a thermoplastic wax, which can be washed out. 

For thick sections, the temperature of the post-cure oven is usually raised in several steps to prevent Assuring. Generally, 12-24 h reaction time at a temperature of 200-260 °C is used [28,35,58,110]. Typically, 200 °C is suffi-... 

Post-curing and chemical modification improves chemical and solvent resistance (20). Paraformaldehyde and acetylene diurea are added to a hot borax solution. Toluenesulfonamide (p and o), a few drops of phosphorous acid. Brilliant Yellow 6G [2429-76-7] Rhodamine E3B, and Rhodamine 6GDN [989-38-8] are added. After heating, the mass is cured in an oven at 150°C. The resulting cured resin is thermoset but can be ground to fine particle sizes. 

Post-Curing. Whenever production techniques or economics permit, it is recommended that compounds based on terpolymer grades be post-cured. Relatively short press cures can be continued with an oven cure in order to develop full physical properties and maximum resistance to compression set. Various combinations of time and temperature may be used, but a cycle of 4 h at 175°C is the most common. The post-cure increases modulus, gready improves compresson set performance, and stabilizes the initial stress/strain properties, as chemically the polymer goes from an amide formation to a more stable imide formation. Peroxide-cured dipolymer compounds need not be post-cured. 

Ovens for Cure, Post-Cure and Ageing Applications.191... 

The reaction was carried out at 100°C for about two hours until the theoretical isocyanate content, as determined by the di-n-butylamine titration method (27), was reached. The PU prepolymer with or without tertiary amine nitrogen groups was dissolved in dry MEK to obtain a prepolymer solution of 30-40% solids. It was then mixed with a mixture of 1,4-BD/TMP (4 1 by equiv. ratio) at an NCO/OH = 1.05/1.0 ratio in the presence of T-12 catalyst (0.05% based on total weight). The reaction mixture was cast in a metal mold treated with a release agent at ambient temperature. After standing 3-5 hours at room temperature, the mold was placed in an oven and post-cured at 100°C for 16 hours. The samples were then conditioned in a desiccator for one week before testing. 

The last major difference between urethane and nylon RIM systems lies in the extent of cure obtained in the mold. Many urethanes are polymerized just far enough in the mold to generate sufficient green-strength for demolding and handling the part. Parts are then oven post-cured to complete the reaction before atmospheric moisture reacts with the residual isocyanate In the part. Nylon RIM parts are fully cured in the mold. 

The blend was mixed for sixty seconds at room temperature (RT). It was poured Into a hot mold (100°C) and cured for 30 minutes at 100 C on a platen press under a pressure of approximately 2700 KPa. The elastomers were then post-cured In an oven at 100°C for 16 hours and conditioned at 25°C and SOX relative humidity for three days prior to testing. 

The elastomers investigated were prepared by curing a silicone resin (supplied by Rhodia Silicones) containing a blend of ingredients polysiloxane-diols, small amounts of hydrogen-methyl polysiloxane, tetraalkoxy silane and fumed silica filler. An organotin ingredient, stannous 2-ethylhexanoate, supplied as a 77% w/w solution in 2-ethyl hexanoic acid, was used as a cure initiator. Typically, 5 wt. of initiator is mixed into the polysiloxane resin. After the initial cure, the material is post-cured at 70°C for 16 h in an air oven. 

Pressure was applied for consolidation below the gel point. The temperature was then raised to 165°C at 3 per minute. The temperature was held at 165°C for 45 minutes, the panels were cooled to 60 C, removed from the autoclave and transferred to an oven. They were post cured for four hours at 177 C. 

Fluoroelastomer vulcanizate properties cure improved by oven post curing. This is true for diamine, bis-phenol, and peroxide cures. For example in Table 3 both bis- tenol and peroxide cured black stocks of a VFi/WE/HFP terpolyner show a 50% increase in MlOO and TB, a 50% drcrease in elongation at break, and a substanti d improvement in ccn ression set resistance. 

The composites made with hand lay-up technique. Short fibres with weight fraction 30% and 50% for eacth length mixed with the rain and then put in a vacuum jar and degassed until "boiled" and all bubbles in the resin are remove. After that poured the mixture to the mold, spacer were used in order to produce 2 mm thick of composite. The mold was press with 20 N/cm. Cured was carried out at room temperature for 16 hours and then post curing was done in an air oven at 80 0 for 5 hours. 

In order to demonstrate that HER compared to butanediol-based elastomer has better physical and mechanical properties at elevated temperatures, cast elastomers with 95% stoichiometry have been made from an MDI terminated polyester prepolymer (Baytec MS-242) extended with butanediol and HER-HP (from INDSPEC Chemical Corporation). Test specimens were cut from a sheet post cured at 110 °C for 16 hours, for the tensile, tear, DSC and DMA determinations. In the preparation of material for the dry heat aging evaluation, tensile, DSC and DMA samples were placed in an air oven with the temperature controlled within 2 °C of the set point and aged for 28 days at 100 °C, 21 days at 120 °C and 14 days at 135 °C. Then, all the samples were stored for at least seven days at room temperature and 50% relative humidity before testing. 

Lay-up is a cold moulding process and therefore cure is achieved by the use of a catalyst (e.g. a peroxide) and also an accelerator (typically cobalt napthanate). This may be assisted by the application of heat, generally by the use of an oven. When the laminate is sufficiently cured, it may be released from the mould and excess material at the edge trimmed back. Often the released part is post-cured at elevated temperature to reach the temperature performance or mechanical properties required for the application. 

Small production runs are processed by compression or transfer molding at 800 to 3,000 psi and 104 to 188°C mold shrinkage is 2 to 4 percent. Long production runs are more economical by injection molding at 5,000 to 20,000 psi, 188 to 252°C, and a 25 to 90 sec cycle. Extrusion requires post-cure in a 316 to 427°C hot-air oven, typically 60 ft/min steam post-cure can run 1200 ft/min. Calendering typically runs 5 to 10 ft/ min. 

---