Plastics surface preparation atmospheric

Lord Corporation introduced adhesives containing methacrylated phosphate monomers that gave much-improved thermal and atmospheric durability, and Dymax Corporation introduced their aerobic acrylics that were less sensitive to inhibition by atmospheric oxygen. Dow Automotive, 3M, and Loctite recently introduced two-part acrylic-based adhesives that can bond many low-surface-energy plastics, including many grades of polypropylene, polyethylene, and thermoplastic polyolefins without special surface preparation (see Section 4.2.2 for a description of this technology). 

A wide variety of capsules loaded with water-immiscible or water-iasoluble materials have been prepared by complex coacervation. Capsule size typically ranges from 20—1000 p.m, but capsules outside this range can be prepared. Core contents usually are 80—95 wt %. Complex coacervation processes are adversely affected by active agents that have finite water solubiUty, are surface-active, or are unstable at pH values of 4.0—5.0. The shell of dry complex coacervate capsules is sensitive to variations ia atmospheric moisture content and becomes plasticized at elevated humidities. 

Sulphur is remarkable for the number of solid forms in which it can be obtained. These include at least four well-known normal polymorphs stable under atmospheric pressure, numerous high-pressure forms of which one is the fibrous form made from plastic sulphur, so-called amorphous forms characterized by small solubility in CS2, and coloured forms produced by condensing the vapour on surfaces cooled to the temperature of liquid nitrogen. Some at least of the amorphous sulphur preparations (e.g. milk of sulphur) give X-ray diffraction lines indicative of some degree of crystallinity, and it is perhaps preferable to use the term u-sulphur rather than amorphous sulphur.The term normal polymorph used above refers to the forms now known to consist of Sg or Sg molecules. In recent years cyclic molecules S (n = 7,9, 10, 12, 18, 20) have been prepared by special methods (see below). 

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