Flame retardant PP material due to its light density, excellent weather resistance and low comprehensive price, more and more manufacturers of all of the favor, in many applications have successfully replaced the flame retardant PS, flame retardant ABS, etc.. Behind the rise of the flame retardant PP material, there is a problem may often encounter problems, that is, the precipitation of flame retardant materials, in the halogen free flame retardant materials, it is more obvious.
Flame retardant PP material due to its light density, excellent weather resistance and low comprehensive price, more and more manufacturers of all of the favor, in many applications have successfully replaced the flame retardant PS, flame retardant ABS, etc.. Behind the rise of the flame retardant PP material, there is a problem may often encounter problems, that is, the precipitation of flame retardant materials, in the halogen free flame retardant materials, it is more obvious.
Flame retardant precipitation not only often in injection molding process have to affect the normal production of model scale, powder caking and mold sticking, in finished parts often happen exhalation, produce white fog like material affect the appearance of the product and lead to decline in flame retardancy and.
Before solving the problem of flame retardant, we first discuss the two important factors that affect the precipitation:
The compatibility of flame retardant and PP base resin
Flame retardant in the PP resin in general in two states: in the form of similar filler filled in resin, and the other is a homogeneous dispersion of the melt in the resin. As the PP is a nonpolar material, the interfacial compatibility between the polar flame retardant and the PP will exist. The worse the compatibility of the interface is, the more easily it will produce precipitation.
Two. The effect of temperature on the precipitation of flame retardant
PP for semi crystalline material, has low glass transition temperature, when the ambient temperature above the glass transition temperature, with the increase of temperature, no amorphous chain segments thermal motion will be accelerated, making and PP resin compatibility poor small molecule flame retardant agent can be relatively easy to overcome the resistance of migration to the surface.
This is parts storage for a period of time after surface sometimes causes of precipitation and high temperature injection molding process is most obvious precipitation process, the precipitation often reflect the mode of scale, etc. in the mold, injection, the higher the temperature of precipitation is more severe. The relationship between the migration rate of the flame retardant and the temperature can be approximately expressed in Figure four. In the range of the decomposition temperature of the flame retardant, the precipitation rate of the flame retardant is significantly increased with the increase of the temperature. At a constant temperature, there is a certain relationship between the precipitation and the time.
After understanding the causes of precipitation, the improvement of the flame retardant precipitation problem can be more effective. There are two main ways:
Scheme:
1 the introduction of strong polar groups (such as amino groups, carboxyl groups, epoxy groups, etc.), to enhance the role of flame retardant and PP interface, can effectively reduce the problem of flame retardant precipitation.
2. Improve the flame retardant agent and resin transfer resistance, reduce the migration rate of flame retardant low molecular weight: reduce the temperature to weaken the chain segment movement or enhance the flame retardant molecular degree and lower molecular weight distribution width becomes effective measures for reducing the precipitation of flame retardant agent of polymerization.
It should be pointed out that: no precipitation of flame retardant PP is not completely without precipitation, which is only to greatly reduce the migration of flame retardant. The current non precipitation flame retardant PP is often based on the high technology cost, therefore, the low cost of anti precipitation is still the current flame retardant PP material needs to be improved.
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