Stabilization methods polymeric polyolefins

The growth of polyolefin fibers continues. Advances in olefin polymerization provide a wide range of polymer properties to the fiber producer. Inroads into new markets are being made through improvements in stabilization, and new and improved methods of extmsion and production, including multicomponent extmsion and spunbonded and meltblown nonwovens. 

Determination of the residual antioxidant content in polymers by HPLC and MAE is one way to determine the amoimt needed for reasonable stabilization of a material, and also to compare different antioxidants and their individual efficiencies. During ageing and oxidation of PE, carboxyhc acids, dicarboxylic acids, alcohols, ketones, aldehydes, n-alkanes and 1-alkenes are formed [86-89]. The carboxyhc acids are formed as a result of various reactions of alkoxy or peroxy radicals [90]. The oxidation of polyolefins is generally monitored by various analytical techniques. GC-MS analysis in combination with a selective extraction method is used to determine degradation products in plastics. ETIR enables the increase in carbonyls on a polymer chain, from carboxylic acids, dicarboxyhc acids, aldehydes, and ketones, to be monitored. It is regarded as one of the most definite spectroscopic methods for the quantification and identification of oxidation in materials, and it is used to quantify the oxidation of polymers [91-95]. Mechanical testing is a way to determine properties such as strength, stiffness and strain at break of polymeric materials. 

Several ofher cross-linking methods can be applied. For example, acrylonitrile, methyl methacrylate (MMA), and its EO derivatives can be copolymerized and then cross-linked with diisocyanate. A thin gel membrane can be prepared by soaking a polyolefin nonwoven fabric in a solution of reactant(s), which is fhen cross-linked by means of ultraviolet radiation. The thickness of fhis fhin gel membrane is 50-100 pm, and the ionic conductivity is 2-4 X 10 3 S/cm. Compared to the gel polymer electrolyte made from dry PAN, fhis process is much simpler, and the energy consumption is 10% lower. However, there are also disadvantages. For example, imreacted monomer and residual catalyst are difficult to remove from the gel polymer electrolyte, leading to reduced ionic conductivity and stability of the polymer. To overcome these disadvantages, the acrylonitrile monomer is first polymerized in nonaqueous electrolyte, and then the unreacted monomer is removed by vacuum. Finally, a multifunctional monomer is added, and the battery is filled with the mixed solution. It is solidified by heating to get the gel polymer electrolyte. 

Many synthesis methods for nanopartides of these materials and thdr surface functionalization have been devdoped. Nanocomposites based on polyolefins were prepared by mdt compounding with nanoscaled ZnO and 1102. Amphiphilic copolymers and surfadants were used to stabilize pattides for film casting in polystyrene, " polycarbonate, and PMMA. By in situ partide preparation in MeOH and subsequent mixing with acetone and PMMA for solvent evaporation transparent ZnO/PMMA films could be realized even without further surface modification. Poly(acrylic add-co-sodium aaylate)/ZnO composite latex partides were obtained via inverse miniemulsion polymerization. ... 

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