The response of a HDPE, a L-LDPE and a PP homopolymer to processing conditions and processing stabilizer formulations in the 220'C to 280°C temperature range was investigated. The technique of multiple extrusion was used. Melt flow and melt flow ratio were measured after the first, third and fifth extrusion pass. In the case of the HDPE and the L-LDPE, degradation by cross-linking was the predominant reaction and the molecular weight distribution showed a significant broadening compared to the virgin samples. The PP homopolymer degraded by chain scission. By adding a multifunctional hindered phenol and a hydrolysis resistant phosphite, all polymers could be efficiently protected against degradation on processing. For the HDPE and the L-LDPE, increased amounts of phosphite provided increased processing stability at constant phenol concentration. A 4:l ratio of phosphite to phenol exhibited the best performance. The most efficient ratio for protecting melt flow of the PP homopolymer was found when a two to one ratio of phosphite to phenol was added.

An experimental program was conducted to study the thermochemical and flammability characteristics of an improved polyisocyanurate foam, uncoated and coated either with fluorinated copolymer or an intumescent material. Testing methods included thermal analysis; scanning electron microscopy; infrared photography; infrared spectroscopy; HLT‐15, ASTM D‐1692, Bureau of Mines Penetration, and XP‐2 smoke chamber flammability tests; limiting oxygen index (LOI); and a moderate‐scale fire simulation test. The uncoated and coated foams were found to have excellent flammability and insulation characteristics, although smoke development was substantial.

The effect of various types of glass specimen holders on the observed degradation time of polypropylene samples was investigated. Depending upon the type of holder used, different results could be obtained with the same antioxidants. In partially enclosed holders, degradation products from samples drastically reduced the long‐term stability of other samples contained in the same holders. No evidence was found to indicate that this influence extended to adjacent sample holders, nor was any evidence found to suggest a positive influence of one sample upon another. Furthermore, under routine testing conditions, no such adverse effects were found. However, in ovens not having sufficient circulation of air or without adequate exchange of fresh air, such adverse effects are believed possible.

An experimental program was conducted to study the thermochemical, flammability and toxicological characteristics of uncoated and coated polyisocyanurate foams. The coatings used were fluorinated copolymer and an intumescent material. Flammability testing methods included the XP‐2 chamber smoke test, ASTM D‐1692, infrared photography, Bureau of Mines penetration test, and a JP‐4 fuel combustion chamber. The results of these tests are presented in a companion paper. Combustion and pyrolysis gases were analyzed by gas chromatography and mass spectrometry. The LD‐50 and LD‐100 tests were performed on Sprague‐Dawley rats housed in an environmental chamber. The isocyanurate foam, flourinated‐copolymer‐coated foam, and the intumescent‐coated foam were found to have excellent flammability and insulation characteristics, although smoke development was substantial. The LD‐50 values for Sprague‐Dawley rats, based on a two‐week survival, were approximately 2.0 gm/ft3 for all three materials. Examination indicated an absence of any significant cause of death except carbon monoxide poisoning.