Investigation Of Effects Of Alum And Potassium Sesquicarbonate On The Fire Characteristics Of Flexible Polyurethane Foam

CHAPTER TWO

EXPERIMENTAL

Materials and methods

a. The raw materials used for the production of the foam were obtained from Winco Foam LTD. Awka. b. The flame retardants Alum (K2SO4 . Al2(SO4)3 . 24H2O and potassium sesquicarbonate (K2CO3 . 2KHCO3 . 3/2H2O) used were procured from Head Bridge Market Onitsha, Anambra State.

Apparatus:

The apparatus used include

USA standard testing sieve (ASTM E - II specification)

Stopwatch

Triple beam balance

Cigarette lighter

Retort stand and clamp

Vernier calipers

2.2.1 Preparation of materials

The Alum and potassium sesquicarbonate were ground into fine powder using a manually operated corona lever machine, Landers and YCIA S.A model. It was sieved to pass through laboratory test sieve of 63um U.S.A Standard Testing Sieve, (ASTM) E.II specification and kept in air tight polyurethane bags.

Production of flexible polyurethane foam

The measured quantity of the samples were added to the polyol in a mixing bowl and stirred vigorously, followed by sequential addition of other raw materials including silicone, stannous octoate DMAE (2 - dimethylamino ethanol) water [55]. The mixture was stirred and TDI (toluene diisocyanate) was finally added and stirred continuously until when there was a sign of rising in the mixture which was immediately poured in the mould. The foam was allowed to solidify for about 9 minutes in the mould before being removed. The foam was allowed to stay for 20 - 24 hour for its total curing after it had been removed from the mould before testing.

Characterization of the foam samples 2.3.1 Determination of the ignition time:

Ignition time is the time taken by the sample to catch fire[17]. It was determined by measuring out the same area and thickness of different concentration of the foam sample.

The foam samples were clamped vertically and ignited at the base with a cigarette lighter and the readings were taken using a stop watch.

Determination of burn length:

Burn length determines the distance from the original sample edge to the farthest point showing evidence of damage due to combustion[58].

12.5cm of the foam samples were cut and set in 120 seconds which was taken as the average burn length. The samples were clamped to a tripod stand such that they were positioned vertically in an air free environment. The essence of protecting the experiment from air interference is to ensure that the burn length is not discrepantly increased. The samples were then ignited at the base and the burn length deduced with a stop watch taking cognizance of the required standard time for burn length.

Determination of flame propagation rate:

The method as described by Eboatu et al [17] was adopted. In this technique, each sample was clamped vertically and ignited at the base with a cigarette lighter in a draught free room. The distance traveled by the flame front at a stipulated time interval was measured by subtracting the final length from the initial length of the samples.

The rate of flame propagation at a vertical interval was calculated as shown below:

Flame propagation rate = Distance traveled by the flame (cm)

Time (Sec)

Determination of flame duration:

Flame duration is a measure of the sustainability of combustion. The foam samples were clamped vertically and ignited at the base in a draught free room and the flame duration time i.e. the duration between the onset of combustion and self - extinguishments was recorded.