F. Simioni

Expandable graphite as an intumescent flame retardant in polyisocyanurate-polyurethane foams

Abstract Flame retarded polyisocyanurate–polyurethane (FR PIR–PUR) foams have been synthesized by the use of a new flame retardant, expandable graphite (EG foams), never used on industrial scale in polyurethane rigid foams, and a mixture of expandable graphite and triethylphosphate (EG–TEP foams). FR PIR–PUR foams, blown with n -pentane, have been prepared with a constant NCO index (250) in order to achieve greater thermal stability and better fire behaviour than polyurethane foams, without significantly decreasing physical–mechanical properties. It was then investigated, as the presence of the flame retardants influences both physical–mechanical properties and fire performance. In particular, fire behaviour of the foams has been studied through cone calorimeter analysis, by the oxygen index and by the DIN 4102-B2 test. The results show that an increase in expandable graphite amount in EG foams or in triethylphosphate content in EG–TEP foams does not worsen mechanical properties. Increasing the amount of triethylphosphate does not influence the thermal conductivity, but an increase in the quantity of expandable graphite causes a worsening of insulating properties, probably due to the bigger dimensions of the foam cells. The presence of expandable graphite alone or in mixture with triethylphosphate brings an overall improvement in fire behaviour. In particular, the oxygen index (OI) increases in a linear way and the highest OI values are obtained for EG–TEP foams. The results from the cone calorimeter are in agreement with those of OI; EG and EG–TEP filled foams show a considerable decrease of rate of heat release (RHR) with respect to unfilled foams. In particular, for EG–TEP foams, the higher the triethylphosphate content the higher the RHR decrease. The only hazard observed is an increase of CO/CO 2 weight ratio in the presence of very high content (25%) of expandable graphite; this effect is not shown when increasing the TEP amount.

Influence of different flame retardants on fire behaviour of modified PIR/PUR polymers

The influence of some halogen-free flame retardants (ammonium polyphosphate or ammonium polyphosphate+melamine cyanurate) on fire behaviour of modified polyisocyanurate/polyurethane (PIR/PUR) foams, with a constant isocyanate index equal to 200, have been studied by means of a cone calorimeter. Foams were prepared from isocyanates modified with adipic acid, in order to obtain amide-modified isocyanurate foams that exhibit better thermal stability performance than polyurethane and lower friability than unmodified polyisocyanurate foams. The results obtained demonstrate that an increasing amount of filler causes a slight worsening of physical and mechanical properties. On the other hand, the cone calorimeter results show that the presence of melamine, which causes a rapid decrease of rate of heat release (RHR) and rate of weight loss, considerably improves the fire behaviour of the foams.

Recycling of flexible polyurethane foams with a low aromatic amine content

Abstract The glycolysis process is the basis for a controlled degradation of crosslinked polyurethane for recycling. Flexible water-blown polyurethanes are polymers with repeating urethane and urea groups. When they undergo heating in presence of glycols and selective catalysts, the reaction of these groups leads to products that are liquid at room temperature. The transesterification reaction of the urethane groups, that leads to the formation of new carbamate is faster than that of the urea groups that leads to the formation of carbamates and amines. The carbamates in turn undergo aminolysis due to the amines formed in the glycolysis of the urea groups to give insoluble products. The possibility of transforming the free aromatic amines by means of a reaction with formaldehyde into products with methylol end groups has been studied. At the same time the formation of a solid phase, mainly of urea groups, has been avoided. The use of ethylene glycol (EG) allows the process to be carried out with high polymer/glycol ratio (up to 4:1) even if a biphase product is obtained. The top phase is mainly formed by the polyether polyol from the polymer, the bottom phase is formed by the solution of carbamates, ureas and amines in EG.

Recycling of Microcellular Polyurethane Elastomer Waste

Waste and scraps from polyurethane rigid foams, with a glycolysis process, can be transformed into products that are liquid at room temperature and terminated with hydrogen active groups, so that they can be directly recycled in the production process of new rigid foams. The process is a very con venient solution to an ecological problem. With proper variations the process can be applied to the recycling of polyurethane structural foams and of microcellular elastomers. The glycolysis chemistry is very complicated because of the presence in the polymer of numer ous groups taking part in the reactions, and because at the process tempera ture, secondary reactions of pyrolysis products cannot be excluded. Moreover, these reaction products can react with themselves and with the glycolysis products. It is therefore of paramount importance that the selective catalysts for the transesterification reactions be active at the lowest possible tempera tures. Chemical plants which are easily managed and require small invest ments have been built in situ by the industries that produce the waste and scraps that are available in the appropriate form and free from transport costs.

Formic acid as a co-blowing agent in rigid polyurethane foams

A valid substitute for CFC-11 (trichlorofluoromethane) for the production of rigid poly- urethane foams for thermal insulating materials, with blowing agents having low environmental impact, is not available yet. HCFC-141b and n-pentane, at present the most utilized physical blowing agents (PBAs), cannot definitely replace CFCs because of their environmental impact and flammability, re- spectively. The aim of the present work is to investigate the opportunity of employing HCOOH as a chemical blowing agent (CBA), other than water, which can in some applications replace physical blow- ing agents. Advantages and disadvantages have been highlighted after studying the isocyanate-formic acid reaction. Evidently, the introduction of new reactions into the polyurethane chemistry introduces a wide range of opportunities and challenges. # 1998 Elsevier Science Ltd. All rights reserved

Recycling of Polyurethane Waste

a high pressure chamber for compression. The resulting CFC is recovered, the foam waste compressed and the condensed water can be drained. Low pressure in the system prevents the CFC (R-11) from leaking. A condensor liquifies the absorbed gas. The residual air is purified by means of active charcoal filters which can be regenerated and then released into the atmosphere. The efficiency of the unit is determined by the formula: