Polymethyl methacrylate crosslinking

Working with polymethyl methacrylate, Sirdesai and Wilkie (36) have shown that certain phosphine-platinum complexes undergo oxidative insertion reactions and thus catalyze crosslinking leading to flame retardance. This catalyst is expensive and not particularly efficient, but serves as a lead. 

Literature continues to be rather extensive on this subject since the 1930s. A summarization is provided in this section. Products fabricated include sheets, films, rods and tubes, and embedment. Acrylic castings usually consist of polymethyl methacrylate (PMMA) or copolymers of this ester as the major component with small amounts of other monomers to modify the properties (Chapter 2). Adding acrylates or higher methacrylates lowers the heat deflection temperature and hardness and improves thermoformability and solvent cementing capability, with some loss in resistance to weathering. Dimethacrylates or other crosslinking monomers increase the resistance to solvents and moisture. 

POLYMETHYL METHACRYLATE POLY T-BUTYL METHACRYLATE POLYMETHYL ISOPROPENYL KETONE CROSSLINKED POLYMETHYL METHACRYLATE POLY OLEFIN SULFONES POLY HEXYL ISOCYANATE DIAZOQUINONE PHOTORESIST... 

ABS Acrylontrile-butadiene-styrene EVA Ethylene-vinyl acetate PAI Polyamide-imide PC Polycarbonate PE Polyethylene PEEK Polyether ether ketone PES Polyether sulfone PET Polyethylene terephthalate PI Polyimide PMMA Polymethyl methacrylate PPO Polyphenylene oxide PPS Polyphenyl sulfide XLPE Crosslinked polyethylene Source Author s own files ... 

In this class of amorphous polymers, there are many biomedical polymers such as phenolic resins (adopted for production of surgical instruments), unsaturated polyester resins (used in bone repair) (Kharas et al., 1997), polystyrene (e.g. Petri dishes for cell culture) and polymethyl methacrylate (PMMA, used in bone cements, intraocular lens, and dental fillings) (Stuart, 2002). These are highly crosslinked polymers (resins in particular) or linear thermoplastic polymers that do not show structural macromolecular regularity. 

The heats of volatilisation of polymers have been determined. Values obtained for polymethyl methacrylate (PMMA) agreed well with calculated values [34]. Chemically crosslinked and oriented LDPE have been investigated using differential photocalorimetry and DSC [35, 36]. 

This involves the use of the Charlesby-Pinner (CP) (22-24) treatment which describes the determination of the gel firaction of the polymer as a function of radiation dose. Figures 4(a) and 4(b) illustrate that pofymers with structures as those shown for Polymers 1 and 2 crosslink when exposed to Co radiation. Polymer 1 has been synthesized with approximately 7 % of the allylic substituent, while the thesis of polymer 2 allowed for 3-4% of the same allylic group. Glass transition temperatures for these pofymers are not quite that of conventional resists such as polymethyl methacrylate (> 100°C), and it is speculated that as allyl content is ino-eased, Tgs will decrease slight. ... 

There are other absorbable fillers, such as collagen (bovine- or porcine-derived) injections, calcium hydroxyapatite (biodegradeable microparticles), poly(L-lactic acid) (PLLA) and non-absorbable fillers such as Artefill (polymethyl methacrylate (PMMA) with collagen) and silicone injections. Table 7.1 lists the most popular dermal fillers available in the United States [18]. Compared to the above-mentioned fillers, HA has the safest biological profile, and it is fully absorbable and biodegradable [19]. Crosslinking of its macromolecular chains increases its resistance to degradation by matrix metalloproteinases and extends its life in the body [6]. 

---