This study determines the influences of siloxane flow agents’ migration on the outermost surface composition of clearcoats, before and after ethanol cleaning. This evaluation is undertaken to improve adhesion of pressure-sensitive adhesives (PSAs) on automotive paint systems. Most of the siloxane flow agents segregate from the bulk to the clearcoat outermost surface during curing. These additives can cover until 50% of the surface area but X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS) analyses indicate that they can be removed by ethanol cleaning. Composition of the cleaned clearcoats surfaces are similar as the composition of clearcoat formulated without siloxane additives: the polyester-(melamine)-polyurethane network is more detected than before cleaning. However, outermost surface analyses show that several aging weeks increase the siloxane additives segregation. This post-cleaning migration modifies the clearcoat surface composition and cancels the chemical modifications due to the ethanol cleaning. XPS analyses show that silicon concentrations after cleaning and aging are inversely proportional to the initial silicon concentrations measured after curing. It highlights that aging has to be controlled to improve adhesion of PSAs on clearcoats. A second ethanol cleaning on aged clearcoats is not effective to remove these new siloxane additives. Their formulation should be different from the flow agents and it could modify their solubility in ethanol. This result could also indicate that these new siloxane additives are not located on the last molecular layer of surface and they would not be soluble in ethanol. 相似文献
Summary: The effect of impurities on the coordination polymerization has generally been classified and discussed in different ways and has been investigated in detail in the syndiospecific homo‐ and copolymerization of styrene. With regard to impurities of styrene, phenylacetylene as an unpolar impurity containing separate multiple bonds, 1‐phenyl‐1,2‐ethanediol and ω‐hydroxyacetophenone as examples of polar impurities, and ethylbenzene as an other unpolar impurity have been investigated regarding the effect on the polymerization rate and the influence on the molecular properties of the syndiotactic polystyrenes. In the syndiospecific copolymerization with p‐methylstyrene, indene shows a different behavior regarding the decrease of the polymerization conversion depending on the comonomer concentrations present in the monomer mixture. Additionally, the effect of impurities of the catalyst system on the syndiospecific styrene polymerization has been demonstrated, particularly of octahydrofluorene as a component of the transition metal compound and of trimethylaluminium as a component of the cocatalyst methylaluminoxane. All results have been discussed with respect to the mechanisms of the effects on polymerization behavior and on polymer properties.
Dependence of the relative polymerization conversion on the amount of indene added to the monomer mixture in styrene (ST)/p‐methylstyrene (PMS) copolymerization (catalyst n‐ratio: 0.5; molar ratio MAO:Ti = 110:1; polymerization temperature: 60 °C; polymerization time: 45 min). 相似文献