A living polymerization process is one that can produce polymers of predetermind molecular weight and a narrow molecular weight distribution containing one or more monomer sequences, the length and composition of which are controlled by stoichiometry of the polymerization reaction and degree of conversion. One such process is reversible addition-fragmentation-termination (RAFT). While compounds made by RAFT function effectively as chain transfer agents, they share one major disadvantage with the entire class of sulfur-based compounds: a characteristic disagreeable odor.
As part of the continuing effort to reduce the environmental impact of various industrial chemical processes, there has been a strong emphasis in developing new methodology for the application and cure of organic coatings. While these ubiquitous materials are absolutely essential to modern life, they also constitute one of the primary industrial Sources of emissions of Volatile organic Solvents that contribute to air and water pollution.
Anionic polymerization processes variously termed living, controlled, or immortal are used to synthesize polymers having a narrow molecular weight distribution and low polydispersity (1.5). These processes are so named because polymerization generally occurs by addition of monomer units to a constant number of growing polymer chains until all monomer has been consumed; if more monomer is added, polymerization resumes.
The use of fillers in both thermoplastic and thermoset polymers has been common. The practice of filling polymers is motivated both by cost reduction and by the need to obtain altered or enhanced properties. Nanostructured dielectric materials have demonstrated advantages over micro-filled polymer dielectrics. However, this is a need to improve these nanocomposites such that they can be adapted for use in such situations as electrical insulation for low or medium voltage cables.
In photoinitiated cationic ring-opening polymerization, the polymerizable substrate is subjected to irradiation with light for a brief period during which the photopolymerization must proceed essentially to completion. Consequently, only monomers that undergo very high rates of polymerization may be employed. Certain epoxide monomers display high reactivity in photoinitiated cationic polymerization and are suitable for such uses while most other undergo sluggish reaction and are not usable.
There are two basic classes of adhesives in widespread current use. The first class is pressure sensitive adhesives, such as are employed in adhesive tapes. The second class is reactive adhesives, used primarily for structural purposes. A long-standing problem with these types of adhesives is that they are unable of obtaining both a long working life and a rapid cure time.
Polymers play an important role in electrical insulating and field grading technology because of their high electrical strength, ease of fabrication, low cost and simple maintenance. Conventionally, additives have been mixed into polymer matrices to improve their resistance to degradation, to modify mechanical and thermomechanical properties, and to improve electrical properties such as high-field stability. However, concentional additives have a negative effect on electrical properties.
This invention is directed to a new, inexpensive analytical instrument that can be used to study and evaluate such essential parameters as light intensity, photoinitiator concentration, and monomer reactivity in a wide variety of UV photopolymerization curing applications. The device provides real-time information as the sample proceeds through the photoreactive phase. Through the direct, continuous, and remote monitoring of the sample using optical pyrometery, the temperature of the monomer undergoing photopolymerization can be obtained as a function of time.
Cationic polymerization is employed in many commercially important applications, including, for example, decorative and abrasion resistant coatings, printing inks, adhesives, fiber reinforced composites, microelectronic encapsulations, tan coatings, pressure sensitive adhesives, high performance aerospace composites, fiber optic coatings, stereolithography, photoresist and holographic recording media. The term UV cure has also been applied to such processes because the polymerizations are typically induced by light having a wavelength in UV region below about 450 nm.
Ultrafiltration (UF) membranes have found widespread use in the food and biotechnology industries. UF has been applied in the processing of normal and transgenic milk, cheese and eggs, whey and potato protein recovery, the clarification of juices and wine, the recovery of proteins from animal blood, and the purification of water. UF is also used in the biotechnology industry for the recovery of biological products through such steps as cell broth clarification, cell harvesting, concentration or diafiltration of protein solutions prior to separation, and final concentration.