Polyether as the main raw material, and the reaction of isocyanate to form the urethane foam products, is the skeleton of reaction. In the case of the same functionality, the molecular weightincreased, the tensile strength, elongation and foam elasticity increase, decrease the reaction activity of similar polyether; in the equivalent value (molecular weight / functionality) under the same condition, functionality is relatively increased, reaction speed, improve the degree of CrosslinkingPolyurethane formation, the foam hardness increased, the elongation decreased. Average polyolcan be 2.5 or more, if the average energy is too low, the foam recovery in poor compression.

If the amount is equivalent to polyether, other raw materials (TDI, water, catalyst etc) reduced, easy to cause cracking or collapsing bubble foam products.

If the small amount of polyether foam products, hard, elasticity, feel bad.

1, foaming agent

In the general manufacturing density of more than 21 pieces of polyurethane foam, using only water(chemical foaming agent) as foaming agent, using dichloromethane in low density formula or super soft formula (MC) and low boiling point compounds (foaming agent) as auxiliary foaming agent.

The auxiliary foaming agent can make the foam density and hardness decreased, because itabsorbs some gasification reaction heat will make the curing slow, need to increase the amount of catalyst. Due to absorb heat, to avoid the risk of burning core.

The foaming capacity available foaming index (equivalent number of 100 copies of polyether water or water) to reflect the amount of blowing agent: m---

The foaming index IF=m (water) +m (F-11) /10+m (MC.) /9 (100 polyether)

Water as foaming agent and isocyanate reaction of urea bond and release of CO2 and a large amount of heat, is a chain growth reaction.

A lot of water, foam density decreased, hardness increased, while the bubble pillar smaller and weaker, lower bearing capacity, easy to collapse and crack bubble bubble. TDI consumptionincreases, the heat release, easy heartburn. If the water is more than 5 copies, you must addphysical foaming agent to absorb heat, avoid core burning phenomenon.

Less water, the amount of catalyst decreases, but the density increases "F'

2, toluene diisocyanate

General soft foam with TDI80/20, 2, 4 and 2, a mixture of 6 isomers. The available coolingpreparation of T100 pure 2, 4TDI.

The amount of TDI (8.68+m = water * 9.67) * TDI index. The TDI index 110-120.

The isocyanate index increases in a certain range, while the foam hardness increased, but reached a certain point hardness after no longer increases significantly, and the tear strength, tensile strength and elongation decrease, bubble formation, big hole, obturator rise, rebound ratedecreased, the surface long sticky, curing time is long, caused by burning core.

The index is low, the bubble will cause cracks, poor elasticity, poor strength, compressionpermanent deformation is large, the surface moist.

3, catalyst

General A33 amine: its role is to promote the reaction of isocyanate and water, adjust the bubbledensity and bubble opening rate, mainly to promote foaming reaction.

Amine: Foam splitting occurs, bubble holes or bubble eye

Less: bubble contraction, amine closed cell foam products, a thick bottom.

Tin: using stannous octoate T-9; T-19 gel catalyst had a high catalytic activity, mainly to promote gelreaction, namely late reaction.

Tin: gel quickly, the viscosity increases, poor elasticity, poor air permeability, resulting in the phenomenon of obturator. If appropriate to improve its dosage can obtain good hole foamrelaxation, to further increase the amount of the foam gradually become close, so that the shrinkage,obturator.

Little tin: gel, foaming process caused by splitting. The edge or the top cracking, and knock, flash phenomenon.

Tin can reduce amine or increase took place in a large number of gas increase the strength of the polymer wall bubble film, thereby reducing the hollow or cracking phenomenon.

Whether or polyurethane foam obturator structure, opening the ideal, mainly depends on theformation of foam gel reaction velocity and gas] in the process of expansion rate is balanced. Thisbalance can be realized by adjusting the type and amount of tertiary amine catalyst in the formulation and stability of foam and other additives.

4, foam stabilizer (silicone oil)

Foam stabilizer is a kind of surface active agent, can make a good dispersion in polyurea foam system, plays the "physical crosslinking points", and can obviously improve the early viscosity offoam mixture, avoid cracking bubble. With the emulsification on the one hand, the foam materialamong the components of the mutual solubility enhancement, adding silicone surfactants on the other hand, can reduce the surface tension of R liquid, gas dispersion required to increase the free energy reduction, dispersed in raw materials in the air are more likely to nucleate in the mixing process. Help small bubbles, adjust the foam pore size, pore structure control, improve foamingstability; prevent bubble collapse, rupture, the bubble wall is elastic, bubbles and uniformity control.The initial foaming stability of foam and prevent bubbles and bubble in the middle of the bubblefired, connected in late foaming. General POP foaming agent, the more the amount of the larger amount of silicone oil.

Amount: so that the foam wall elasticity increases, not broken, fine bubble. The cause of the obturator.

Less: bubble, bubble collapse since, after the larger aperture, easy and global.

5. The influence of temperature

The polyurethane foaming reaction increased with increase in the temperature of the material, thesensitive formula will cause danger of fire and burning core. The general control of polyol andisocyanate component at constant temperature. When the foaming foam density decreased melt temperature increased. The same formula, the material temperature