Flow-cure properties

ASTM D3795, Test Methodfor Thermal Flow/ Cure Properties of Thermosetting Plastics by Torque Rheometer, Vol. 8.02, ASTM, Philadelphia, Pa., 1993. 

Ref 7 reviews the characteristics and manuf of PVC plastisol proplnts. Information is given on compn, uncured proplnt flow, curing time, variation of physical properties with temp of... 

Special Polymers control flow and curing properties of self compacting high-performance concrete... 

Thermal Flow and Cure Properties Using a Torque Rheometer... 

ASTM D3795-93, Thermal flow and cure properties of thermosetting plastics by torque rheometer. 

Uses Epoxy hardener, curing agent for powd. coatings containing 2% accelerator and 2.5% flow modifier Properties Gardner 1 max. solid vise. 290-470 cps (150 C)... 

Chem. Descrip. Low m.w. hydroxy-functional silicone-based additive Uses Mar resist, aid, slip agent, flow aid for powd. coatings based on epoxy, polyester, acrylic, and PU resins Features Does not reduce gloss or heat stability, even at over cure Properties Grans. sp.gr. 1.23 g/cm m.p. 85 C 96.6% act. 

The composition and curing properties of epoxy resins are of great commercial importance, and many workers have published separations. Heitz [38] used a poly(vinylacetate) gel with a coiled poly(tetrafluoro ethylene) column (1000 x 0.2 cm), with dimethylformamide as eluent at a very low flow rate. This gave plate counts of up to 160000. He showed the separation of oligomers up to n = 10, but other smaller components, which have different end groups, are visible. The telomerization of tetrahydrofuran is also described. 

ASTM D3795 - Thermal Flow and Cure Properties by Brabender Torque Rheometer - This test give a simulation of what will happen during injeetion or transfer molding. 

Other techniques include oxidative, steam atmosphere (33), and molten salt (34) pyrolyses. In a partial-air atmosphere, mbber pyrolysis is an exothermic reaction. The reaction rate and ratio of pyrolytic filler to ok products are controlled by the oxygen flow rate. Pyrolysis in a steam atmosphere gives a cleaner char with a greater surface area than char pyroly2ed in an inert atmosphere however, the physical properties of the cured compounded mbber are inferior. Because of the greater surface area, this pyrolytic filler could be used as activated carbon, but production costs are prohibitive. Molten salt baths produce pyroly2ed char and ok products from tine chips. The product characteristics and quantities depend on the salt used. Recovery of char from the molten salt is difficult. 

Silicon—Ca.rbon Thermoset. The Sycar resins of Hercules are sihcon—carbon thermosets cured through the hydrosilation of sihcon hydride and sihcon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (<15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type apphcations. 

Methods of preparation of the laminates depend on the partieular grade of polyimide resin used but in one process the polyimide precursor is dissolved in acetone and this solution is used to impregnate the glass or carbon fibre and thus produce a pre-preg . The pre-preg is dried and then pre-cured at about 200°C for about 3 hours. This operation reduces the volatile content and also modifies the flow properties to make them more suitable for the subsequent... 

Other ingredients may be added to prevent sticking to moulds (lubricants), to promote the curing reaction (accelerators), to improve the flow properties (plasticisers) and to colour the product (pigments). 

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