Impact modifiers described in some detail

The reason why certain polymers show brittle at room temperature , which is mainly determined by the structure of the polymer itself . Polymer
The brittleness and its molecular main chain flexibility , the molecular chain of the more flexible , its brittleness is smaller , whereas the greater brittleness . All Movies
A flexible polymer chain affected by factors such as the main chain structure , a substituted group, the polymerization degree , crosslinking degree of the polymer can affect the brittle
Sex . To improve the toughness of Impact modifier for PVC  the material , the following three main ways : in
Rubber component introduced into the polymer structure , as in the bulk polymerization of styrene butadiene component may be introduced in
Preparation of high-impact polystyrene (
HIPS, which in situ in the reaction kettle modification techniques suitable for mass production . In
Introducing the polymer backbone monomers low glass transition temperature , such as bisphenol
A polycarbonate raw
Production . Through
After some modification method would have the effect of toughening complexes were blended with polymer materials ,
Thereby enhancing the impact properties of polymeric materials . Such complexes known as impact modifiers , these additives is mainly used polyvinyl chloride
Ene, polystyrene and other plastics . The modified method has the freedom and flexibility characteristics.
1.1
Mechanism of impact modifier
The impact modifier in the polymer research, although there are a large number of scholars have carried out a series of fruitful work , but to
Today there are some issues unresolved , so it is no unified theory. Different scholars have proposed a different interpretation ,
Summarized in the following: rubber absorbs energy theory , shear yield theory, theory of cracks , crazing shear zone management
On other . Due to the use of rubber or elastomer -modified impact of plastics material will also reduce the rigidity of the self
Since there has been replaced by vegetable stearic acid  rigid particles of rubber and elastomer toughened polymers ideas, and the corresponding emergence of non-
Rigid polymer particle toughening machine theory .
Rubber absorbs energy theory
Is stretched when the cross section is substantially found not shrink , thereby setting
Want to cavitation occurs inside the material and the density becomes small ( approximately 8% reduction )
Year. They think its elongation stress whitening phenomenon
Is generated within the material of the hole caused by the scattering of light . Therefore, the argument put forward : when the material strain , in its internal generated a lot of very fine cracks , then there must be a
Of rubber particles across the crack , thus preventing rapid crack
Rapid expansion , while the rubber particles in its consumption of energy during deformation due
, Thereby improving the toughness of the material . As shown, located
Rubber particles in a growth of the crack face , such that material by
To break the impact absorbed energy equal to the Brittle Fracture
We can add on to be broken rubber particles acting combined. While
Explained tensile yield , must liquid stabilizer  assume the formation of a large number of micro- cracks in the rubber particles absorb energy schematic
And each micro-cracks were blocked by rubber particles , micro-cracks are adjacent the substrate a thin layer of polystyrene are separated . Thus, a large tensile strain can be micro- cracks open, the rubber particles are
Elongated and polystyrene layers bend to achieve. Accordingly, they assume that the rubber particles have a "bridge " effect as well as particles having a high flexibility and good adhesion to the substrate with the premise . This theory is that it is the lack of attention to the rubber , while ignoring the polymer matrix . Toughened polystyrene and polyvinyl chloride is concerned, both in the fracture behavior of a significant difference , which is not easy to explain the theory of micro-cracks