[Show abstract][Hide abstract] ABSTRACT: In 1953 Stanley Miller tested a hypothesis put forward by A.I. Oparin and, later, J.B.S. Haldane concerning the origin of life. The classic experiment is frequently cited in the popular literature and programing as evidence supporting the formation of primitive cellular organisms from polypeptides, which self-organized over millions of years. Yet many of the reaction products from Miller’s experiment are more problematic for the model than advocates readily admit. Among these is formic acid, reportedly present at about double the combined concentrations of identified amino acids including glycine, alanine, aspartic acid and glutamic acid. Formic acid can produce a significant negative impact on the formation and stability of components such as a hypothetical polypeptide. Consequently, advocates of the Oparin-Haldane-Miller theory are faced with an acute problem. The present paper explores the reaction chemistry of aqueous formic acid and an imaginary polypeptide assumed to be present in the primordial ocean.
Creation Research Society Quarterly Journal. 01/2013; 49(#3):211.
[Show abstract][Hide abstract] ABSTRACT: Phenothiazine (PTZ) continues to be an effective scorch inhibitor used by a number of slabstock foam manufacturers. It has a long, successful history as an additive, often used in combination with other antioxidants. However, this industrial workhorse comes with a possible side effect. Polyurethane foams containing trace quantities of PTZ or its post-reaction products have been observed to occasionally "pink" during warehouse storage. The present paper will examine relevant reaction chemistry; the underlying reasons for PTZ-induced discoloration; and offer some promising new solutions that eliminate "pinking" while providing scorch reduction benefits.
[Show abstract][Hide abstract] ABSTRACT: Polyurethane slabstock foam production involves a vigorous exothermic reaction. The prolonged post-reaction elevated temperature leads to chemical changes that appear as darkening in the core of the production foam block and is defined as "scorch". To suppress unwanted scorch, manufacturers add antioxidant blends known as scorch inhibitors. Generally, scorch inhibitors reduce the damaging effects of extended heat exposure by quenching thermally generated free radicals. Scorch inhibitors are effective at minimizing process issues but are known to contribute to foam discoloration resulting from warehouse fumes and exposure to light. The present paper explores chemical and morphological changes in the PUR foam scorched region. The beneficial effects of VANOX ® 982 Antioxidant, a new scorch inhibitor which reduces scorch and foam discoloration, will also be reviewed.
[Show abstract][Hide abstract] ABSTRACT: Polyurethane (PUR) slabstock foam production involves a vigorous exothermic reaction that leads to the well known phenomenon of scorch. To control the potential loss of product and minimize unwanted scorch, manufacturers often use antioxidant blends consisting of hindered phenol and secondary aromatic amine derivatives. Common commercial blends may also contain additional additives such as phenothiazine at low concentration levels. These widely used scorch inhibitor blends, while reducing scorch discoloration, are known to contribute to PUR foam discoloration resulting from end-use stresses. The present paper explores a new patented scorch inhibitor blend (PLX 982) that reduces scorch significantly when compared with state-of-the-art products and adds minimally to foam discoloration when exposed to selected stresses such as light or NO x fumes. To set a context for this discussion, we will explore the mechanism of thermo-oxidative degradation of PUR hard and soft segments and assess the impact of various blends.
[Show abstract][Hide abstract] ABSTRACT: Polyolefins and composites are susceptible to oxidation, which affects physical properties. This is of great practical importance depending upon the application of the final part. Where is the plastic to be used? What is its environment? How long will the part last in that context? What can a manufacturer do to extend the service lifetime of its part? The present study offers a new long term heat stabilizer for both filled and unfilled polypropylene compounds.