Polypropylene blowing agents

Eoams were extruded from low density polyethylene (LDPE) and blends of LDPE with syndiotactic polypropylene (sPP), using isobutane as the blowing agent. The extruded materials were characterised by measurement of dimensional stability at room temperature, density, tensile properties, dynamic stiffness, and crystallinity determined by differential scanning calorimetry. The sPP, with a slow crystallisation rate, did not interfere with the expansion of the LDPE, and enhanced the temperature resistance by in-situ crystallisation. The blends were flexible, dimensionally... 

Orlando, FI., 7th-llth May, 2000, paper 703 EFFECT OF CHEMICAL BLOWING AGENT DOSAGE ON THE PROPERTIES OF EXTRUDED EXPANDED POLYPROPYLENE Dixon D Martin P J Harkin-Jones E Belfast,Queen s University (SPE)... 

Patent Number US 5567742 A 19961022 DIMENSIONALLY-STABLE POLYPROPYLENE FOAM EXPANDED WITH INORGANIC BLOWING AGENTS... 

Carbon dioxide gas was used as a physical blowing agent to produce medium density polypropylene foam sheets using a single screw extruder. The mechanical properties of the foam were similar in the machine direction and in the transverse direction. Abetter surface finish and a lower density was produced by using a commercial wrapping film as a cap layer. The process conditions and the die design data are presented and an attempt made to relate them to the product characteristics. 4 refs. 

Derivation A polyether such as polypropylene glycol is treated with a drisocyanate in the presence of some water and a catalyst (amines, tin soaps, organic tin compounds). As the polymer forms, the water reacts with the isocyanate groups to cause cross-linking and also produces carbon dioxide, which causes foaming. In other cases, trifluoromethane or similar volatile material may be used as a blowing agent. 

Use Blowing agent for polyolefins, impact polystyrene, polypropylene, ABS, etc. 

New potential possibilities in polypropylene crosslinking which have not been elaborated very much are those from the use of azobisdicarbonamide as a crosslinking and blowing agent. This was attempted at temperatures ranging fi-om 200 to 260 °C [129],... 

To date, the autoclaving process has been the one most frequently used to produce foam particles, in particular EPP (expanded polypropylene). In the autoclaving process, a suspension of compact polypropylene microgranulate and a liquid is placed under a pressurized atmosphere with inert gas and blowing agent while... 

Paraffin oils, the silicone oils, the medium to long chain alkyl phthalates and isoph-thalates, and the polypropylene oxides are selected for preparation of blowing agent mas-terbatch for making of polystyrene foams. The amoimt of plasticizer should be selected to maintain Vicat softening temperature between 30 and 50°C. 

For melamine phosphate-pentaerythritol-polypropylene, the char former/blowing agent ratio was shown to have a significant effect on flame retardancy [37]. 

Polypropylene, solid additives, (chemical blowing agent)... 

Examples of chemical blowing agents are azo compounds, N-nitroso-compounds, and sulphonyl hydrazides, which yield 10()-3()() cm of nitrogen per gram of compound at temperatures of 90-2 7 5°C. Azodicarbonamide is widely used, having a decomposition temperature of 230-235°C, which can be reduced to 155-200°C by means of metal compounds such as lead and zinc stabilizers. It can thus match the temperatures at which the melt viscosity of many polymers is suitable for foaming, and is used (typically) in calendered PVC and PVC plastisols and in structural foam forms of polyethylene, polypropylene, PVC, polystyrene, and ABS. 

Cefor Polypropylene, Shell Celanex PBT, Hoechst Celcon Polyacetal, Hoechst Celogen Blowing agents. Uniroyal Chemical... 

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