Comparison to poly

The thermal stability of PNT from different polymerization methods is presented in Table 18.7. ft appears that the colored (dark brown) but transparent PNT -N film synthesized by VDP is the cleanest film among the polynaphthalenes from other polymerization processes that have been reported. These PNT-N films from VDP also have very low dielectric constants in comparison to poly(tetra-fluoro-p-xylylene) films. PNT-N and PNT-F films have higher dissociation temperatures (>570°C) and better thermal stability (>530°C), and no film cracking was observed until PNT-F was annealed at 600°C in nitrogen. Table 18.8 presents a summary of the different properties ofPNT-N and PNT-F prepared by the VDP process. 

Copolymers of ethylene and norbomene exhibit excellent transparency, high moisture barrier, high strength and stiffness, and low shrinkage. In comparison to poly(ethylene) (PE) and polypropylene) (PP), they show a very low gas permeability. They are used for blister packaging in pharmacy applications and for flexible films for food packaging. Multilayer films consisting of PP outer layers and a cyclic olefin copolymer are in use. 

Oxidative Matrix Polymerization The polymerization of NVK in a matrix of poly(ethylene glycol) (PEG) has been described. As an oxidant, Ce" + has been used. PEG proved to be a more suitable matrix in order to obtain a stable homogeneous ternary complex solution in comparison to poly(acrylic acid) and poly(V-vinyl-2-pyrrolidone). 

Carbon nanotube composites from poly(ethylene) and PPS have been prepared by melt mixing [83]. The two types of carbon nanotube composites were compared with respect to their properties. Measurements of the electrical properties suggest an increase in homogeneous dispersion of the carbon nanotubes in the PPS matrix in comparison to poly(ethylene). This finding has been attributed to the increase in connectivity of the nanotube network structure of the composite. 

Surface Protection. The surface properties of fluorosihcones have been studied over a number of years. The CF group has the lowest known intermolecular force of polymer substituents. A study (6) of liquid and solid forms of fluorosihcones has included a comparison to fluorocarbon polymers. The low surface tensions for poly(3,3,3-trifluoropropyl)methylsiloxane and poly(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane both resemble some of the lowest tensions for fluorocarbon polymers, eg, polytetrafluoroethylene. 

It has been found that, for a fixed mineral filler content, the viscosity of PMF-based composites increases when the coat is made of polyethylene [164, 209, 293], poly(vinyl chloride) [316] and polypropylene [326, 327], The picture was different, however, for composites based on the ethylene/vinyl acetate copolymer to which kaolin with grafted poly (vinyl acetate) was added [336]. Addition of PMF with a minimum quantity of grafted polymer results in a sharp drop of flowability (rise of viscosity), in comparison to addition of unmodified filler but with a further increase of the quantity of grafted polymer the flow gradually increases and, depending on the kaolin content and quantity of grafted polymer, may even become higher than in specimens with unmodified filler, for equal concentrations. 

Fig. 17. CP-MAS 13C-NMR spectra of threodiisotactic poly(l, 2-dimethyltetrame-thylene) below, c), and above the glass transition, b), in comparison to the spectrum in CDC13 solution at 303 K, a). The chemical shifts given at the signals refer to TMS = 0 ppm. (Ref. 32))...

---