Latex compounds, swelling

Ten of 12 workers experienced acute irritant contact dermatitis of the hands after 2 days of direct contact. In the most severe case, a woman with no previous skin problems, who wore latex gloves intermittently, had painful swelling of the fingers of both hands with redness and vesicles on the palms. The affected skin later became thickened and showed a brownish discoloration. Another worker noticed small vesicles on the forehead, probably due to scratching with contaminated fingers. All cutaneous reactions cleared within 3 weeks of termination of exposure. Gas chromatograph analysis of the NMP used at the factory did not reveal any contaminating compounds. 

The swelling of the seed latex in the presence of water-insoluble, low molecular weight compounds in the monomer phase may be quantitatively expressed by (3, 7-18),... 

Still further modifications of natural rubber are the superior processing or SP rubbers. Here a portion of the latex is vulcanized before coagulation. In a sense, the vulcanized globules serve as small particle reinforcement of the rubber. Such rubbers help keep close dimensional tolerances or smooth finish requirements. Extrusion and/or calender output is improved, and die swell is lessened in lightly loaded compounds. In the interest of economical overseas shipments from the Far East, masterbatches of these rubbers, called Processing Aids (PA), are used. For example, PASO is a rubber that has 80 parts of vulcanized rubber and 20 parts of raw rubber. A softer material called PA57 has 57 parts of vulcanized rubber, 14 parts of raw rubber, and 29 parts of oil. 

---