Compression molded films thermal properties

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

A comparison of the dynamic mechanical properties of our HB at 35 Hz has been made to that of LDPE in Figures 14 A and B. The thermal and sample preparative history affects the mechanical properties of HB films to such an extent that in order to make a meaningful comparison one has to describe the exact history of the samples. Such a thermal history dependence has been examined for LDPE(54,57) and recently for HB.(12) Shown in Figures A and B are the mechanical spectra for HB-PQ, HB-Tol, and LDPE-PQ films. The compression molded films were prepared 1 to 2 days prior to the test. The solution cast film (from toluene), HB-Tol, was annealed at 80°C for 2-3 days and stored at room temperature for 1 week... 

It is noted that the specific phase morphology of the injected molded tensile specimens used in the present study may differ from the compression molded film morphology. In the case of extruded samples of polymer blends displaying macrophase separation. Van Oene (25) indicates that the dispersed phase may appear as either ribbons (stratification) or droplets independent of shear strain rate but dependent of the post-extrusion thermal history. A study of the effect of morphology and phase inversion on the mechanical properties of the incompatible PPO blends is presently in progress. 

Thermal stability was determined by assessing the color of compression molded films of the polymer. A film sample was held in a convection oven for 4 hours at 200°C. Color and clarity of the aged film varied firom no ehange to yellow for different polymers. Molecular weight of the polymer was assessed by an indi-reet measurement of melt viscosity. A film sample was produeed by applying pressure to 0.5 g of polymer powder at 225°C in a press for 30 seconds. The area of the film formed by this technique was measured as an indieation of the viscosity of the polymer. A lower viseosity, i.e., lower molecular weight, polymer spread into a larger area film sample. Table 5.41 shows a summary of the PVDF polymerization conditions and the polymer properties. The data in Table 5.41 indieate that no reaction took place in the absenee of both iron and surfactant. Polymerization yield was anemie in the presence of only surfactant or iron. 

As a tme thermoplastic, FEP copolymer can be melt-processed by extmsion and compression, injection, and blow molding. Films can be heat-bonded and sealed, vacuum-formed, and laminated to various substrates. Chemical inertness and corrosion resistance make FEP highly suitable for chemical services its dielectric and insulating properties favor it for electrical and electronic service and its low frictional properties, mechanical toughness, thermal stabiUty, and nonstick quaUty make it highly suitable for bearings and seals, high temperature components, and nonstick surfaces. 

Recently the synthesis and characterization of novel fluorinated poly(aryl ether)s containing perfluorophenylene moieties " " was also reported. These fluorinated polyethers were prepared by reaction of decafluorobiphenyl with bisphenols. These polymers exhibit low dielectric constants, low moisture absorption, and excellent thermal and mechanical properties. Tough, transparent films of the polymers were prepared by solution-casting or compression-molding. The fluorinated poly(aryl ether)s containing perfluorophenylene moieties are good candidates for use as coatings in microelectronics applications. 

The properties of dense films are often equated with the Intrinsic properties of the bulk polymer. However, this comparison must be made with caution because chain packing, and thus transport properties, may be dependent upon thermal history or solution history during film preparation and upon the attainment of equilibrium prior to characterization. Dense films can be prepared by melt extrusion, compression molding or solution casting,... 

The necessary pressure and temperature vary considerably depending on the thermal and rheological properties of the polymer. For a typical compression molding thermoset material, they may be between 120 and 200 C and 1000 and 3000 psi. A slight excess of material is nsnaUy placed in the mold to ensure its being completely filled. The rest of the polymer is squeezed out between the mating surfaces of the mold in a thin, easily removed film known as flash. 

Polyamide-imides enjoy, as the name suggests, a positive synergy of properties from both polyamides and poljdmides, such as flexibility, melt processability, elongation, dimensional stability, and toughness. Polyamide-imide polymers can be processed into a wide variety of forms, from injection- or compression-molded parts and ingots to coatings, films, fibers, and adhesives. Generally these articles reach their maximum properties with a subsequent thermal cure process. 

The dried blend resin can either be injection or compression molded into articles with specifically tailored thermal and mechanical properties that lie between the respective properties of the pure PBI and PEKK from which the blend was produced. These blends can be used to enhance films, composites, or alloys. Further, these blends can be reinforced or filled prior to molding to produce unique blended products such as T-series products marketed by PBI Performance Products Inc. 

Polyamide-imides (PAIs) are thermoplastic amorphous polymers prepared by the condensation of an aromatic diamine, such as methylene diamine, and an anhydride, such as trimellitic add chloride. PAIs have good mechanical, thermal, chemical resistance, high strength, melt processability, and high heat capacity. They can be processed into a variety of forms, such as injection or compression molded articles, coatings, films, fiber, and adhesives. The typical heat deflection temperature for neat molded PAI is 278°C,but reinforcements are often used to improve mechanical properties. PAIs are generally soluble in strong aprotic solvents such as NMP and DMAc, and thus misdble blends with PBI are feasible. 

---