ABSTRACT:In this review, a summary is provided of the manufacturing process for syndiotactic polystyrene together with an overview of applications of syndiotactic polystyrenes, including selected examples of typical applications. The manufacturing process of syndiotactic polystyrene, consists of several basic sections: catalyst premix preparation, monomer treatment, polymerization reaction using a powder bed reactor together with an evaporative cooling system, devolatilization and extrusion, and finally finishing, including cooling and crystallization of the strands. This process is suitable for providing a wide range of syndiotactic polystyrenes comprising homopolymers, with a broad range of melt flow rates as well as copolymers of various comonomer contents, leading to products with various melting temperatures. Essential relationships and correlations of the separate process stages are demonstrated, in addition to useful analytical methods to control the process. These polymers' unique combination of heat resistance, chemical resistance, and electrical properties has led to their successful application in automotive, electrical and electronics, consumer and industrial uses.
An approach to improve the efficiency of the thermal insulation behavior of expandable polystyrene (EPS) particle foams by diminishing the thermal conductivity is the reduction of the radiation term of the thermal conductivity by an adjusted enlargement of the cell size of the particle foam. This correlation was investigated in detail by the determination of the dependences of cell size and thermal conductivity on the densities of the particle foam over a wider range using samples of expandable polystyrene particle foams showing conventional fine cell size as well as enlarged cell sizes. Based on the dependence of cell size on foam density of fine cell EPS foams, an equation is given also covering foams of larger cells. At the same mean diameter of the foam cells, the thermal conductivity of the EPS foam is increasing with a decrease in foam density in the whole range of diameters investigated from about 50—350 µm. At the same foam density, the thermal conductivity is in general independent of the mean cell diameter of the EPS foam at high foam densities, whereas at lower foam densities, the thermal conductivity is decreasing with increasing mean cell diameter of the foam, in a range of foam densities from about 10—35 g/L. Subsequently, a practical model to describe the dependence of thermal conductivity of expandable polystyrene particle foam on cell size and foam density is proposed and discussed.
Tetrabenzo[a,c,g,i]fluorene (Tbf-H, 4) was deprotonated with n-butyllithium, leading to ionic Tbf-LiLn complexes 5 and 6, consisting of well-separated cations (Li(THF)4 (5), Li(DME)3 (6)) and Tbf
anions. Subsequent reactions with chlorotitanium alkoxides Cl
x
Ti(O
i
Pr)4
-
x
(x = 1, 3) and chlorotitanium
phenoxides {ClTi(OR)3(THF)}2 (R = C6H5 (12), 4-MeC6H4 (13), 4-
t
BuC6H4 (14)) give a series of η5-tetrabenzo[a,c,g,i]fluorenyltitanium complexes (TbfTiCl2(O
i
Pr) (11) and TbfTi(OR)3 [R =
i
Pr (10), C6H5
(15), 4-MeC6H4 (16), 4-
t
BuC6H4 (17)]), which were characterized by NMR, MS, and IR measurements
and X-ray crystallography. Additionally, the compounds' properties regarding the syndiospecific
polymerization of styrene when activated with MAO were explored. The activities increase in the following
order [kg sPS/(mol Ti × mol styrene × h]: 11 (1420) < 17 (3400) < 16 (3740) < 10 (6040) < 15
(6720).
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