Modern Views on the Chemistry of Vulcanization Changes. III. Reaction of Sulfur with Squalene and with Rubber

1947 ◽  
Vol 20 (2) ◽  
pp. 360-365
Author(s):  
George F. Bloomfield
Keyword(s):  
Molecular Weight ◽  
Molecular Distillation ◽  
Elevated Temperatures ◽  
Close Resemblance ◽  
Sulfur Vulcanization ◽  
Comprehensive Survey ◽  
Molecular Complexity ◽  
Long Chain

Abstract The hexaisoprene, squalene (C30H50), is a promising hydrocarbon for inclusion in a comprehensive survey of sulfur-olefin reactivity and the mechanism of rubber vulcanization, since its molecular complexity is such as to render it more closely comparable with long-chain polyisoprenes than is the diisoprene dihydromyrcene, while its molecular weight is still sufficiently low to enable molecular distillation of the sulfurated reaction product to be accomplished without recourse to unduly elevated temperatures. It has been shown elsewhere that the behavior of squalene toward halogens resembles more closely that of rubber than does the behavior of dihydromyrcene. It is now found that the reaction of squalene with sulfur at the ordinary vulcanization temperature pursues a course very similar to that of dihydromyrcene while at the same time showing a close resemblance to rubber-sulfur vulcanization.

Relation of Structure to Properties in Polyurethanes. Effect of Branching

1961 ◽  
Vol 34 (2) ◽  
pp. 639-647
Author(s):  
E. F. Cluff ◽  
E. K. Gladding ◽  
J. B. Rogan
Keyword(s):  
Molecular Weight ◽  
Hydrogen Bonding ◽  
Elevated Temperatures ◽  
Marked Effect ◽  
Dynamic Properties ◽  
Side Chains ◽  
Present Evidence ◽  
Polar Groups ◽  
Long Chain ◽  
Covalent Crosslinks

Abstract Attaching short N-arylurethane branches to a high molecular weight, linear polyether urethane introduces interchain forces—very likely arising from hydrogen bonding—which increase as the side chains become more polar. These forces are sufficiently strong to increase the bulk viscosity of the raw polymers and, with the more highly polar groups, are strong enough to impart an appreciable elastic memory. At slightly elevated temperatures (80° C) these forces are reduced considerably, which is to be expected if they arise through hydrogen bonding. However they are either not strong enough or are too limited in number to compete with the covalent crosslinks in the elastomer vulcanizates. Thus no significant alteration is observed in the vulcanizate properties which are customarily measured. The marked effect of these short aryl side chains to reduce crystallization tendencies can most likely be attributed to the bulkiness. of the pendant aryl moiety, which prevents—or slows down—the ordering of the polytetramethyleneether chains into a crystal lattice. Long chain branches influence dynamic properties considerably. Present evidence indicates that optimum dynamic properties—as measured by Yerzley resilience—are obtained when “loose ends” are absent.

Coactivation of Delayed-Action Vulcanization. Part I. Polymeric, Nonmigratory Cure Coactivators for Accelerated Sulfur Vulcanization

1989 ◽  
Vol 62 (5) ◽  
pp. 957-972
Author(s):  
A. Y. Coran ◽  
F. Ignatz-Hoover ◽  
L. H. Davis
Keyword(s):  
Molecular Weight ◽  
Minimum Loss ◽  
Synthetic Rubber ◽  
Curing Characteristics ◽  
Sulfur Vulcanization ◽  
Delayed Action ◽  
Very High ◽  
Rubber Article

Abstract Rubbery vinylpyridine-butadiene copolymers, containing 20–65% by weight of vinylpyridine monomer units, are effective coactivators of vulcanization for TBBS-accelerated sulfur-vulcanized SBR. In addition to emulsion SBR, the new co-activator has been evaluated in copositions of solution SBR, BR, NR, and various blends. The co-activator is active in all of the compositions which contain butadiene-derived synthetic rubber. This includes blends such as SBR/BR, solution-SBR/BR, SBR/NR, BR/NR, SBR/BR/NR, etc. There is little or no activity in which NR is the only polymer. The most efficacious copolymers contain between 30 and 60% 2-vinylpyridine. The incorporation of such a copolymer into an unvulcanized butadiene-derived rubber mix can give a substantial increase in the rate of crosslink formation with only a minimum loss of scorch resistance. Since the polymeric coactivators are very high in molecular weight, it can be at least tentatively concluded that they will not migrate from one component stock to another in a built-up multi-stock rubber article, either before or during vulcanization. Since the curing characteristics of a vinylpyridine-copolymer-containing TBBS-accelerated stock can be similar to those of TBBS-accelerated NR, it might be concluded that the new additives will solve some of the problems in balancing the cures of adjacent NR and SBR stocks in a multicomponent cured rubber article.

scholarly journals Improving Rheological and Mechanical Properties of Various Virgin and Recycled Polypropylenes by Blending with Long-Chain Branched Polypropylene

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1137
Author(s):  
Sascha Stanic ◽  
Thomas Koch ◽  
Klaus Schmid ◽  
Simone Knaus ◽  
Vasiliki-Maria Archodoulaki
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Tensile Test ◽  
Reactive Extrusion ◽  
Original Material ◽  
Melt Flow Rate ◽  
Single Screw Extruder ◽  
Pp Blends ◽  
The Impact ◽  
Long Chain

Blends of two long-chain branched polypropylenes (LCB-PP) and five linear polypropylenes (L-PP) were prepared in a single screw extruder at 240 °C. The two LCB-PPs were self-created via reactive extrusion at 180 °C by using dimyristyl peroxydicarbonate (PODIC C126) and dilauroyl peroxide (LP) as peroxides. For blending two virgin and three recycled PPs like coffee caps, yoghurt cups and buckets with different melt flow rate (MFR) values were used. The influence of using blends was assessed by investigating the rheological (dynamic and extensional rheology) and mechanical properties (tensile test and impact tensile test). The dynamic rheology indicated that the molecular weight as well as the molecular weight distribution could be increased or broadened. Also the melt strength behavior could be improved by using the two peroxide modified LCB-PP blends on the basis of PODIC C126 or PEROXAN LP (dilauroyl peroxide). In addition, the mechanical properties were consistently enhanced or at least kept constant compared to the original material. In particular, the impact tensile strength but also the elongation at break could be increased considerably. This study showed that the blending of LCB-PP can increase the investigated properties and represents a promising option, especially when using recycled PP, which demonstrates a real “up-cycling” process.

scholarly journals Phthalocyanine formation using metals in primary alcohols at room temperature

2000 ◽  
Vol 04 (01) ◽  
pp. 103-111 ◽  
Author(s):  
CLIFFORD C. LEZNOFF ◽  
ANNA M. D'ASCANIO ◽  
S. ZEKI YILDIZ
Keyword(s):  
Molecular Weight ◽  
Copper Powder ◽  
Reverse Micelle ◽  
Room Temperature ◽  
Micelle Formation ◽  
Lithium Metal ◽  
Electronic Effects ◽  
Primary Alcohols ◽  
Lower Yield ◽  
Long Chain

Lithium metal added to a solution of 4-neopentoxyphthalonitrile in 1-octanol or other long-chain primary alcohols at room temperature resulted in phthalocyanine formation at a reasonable rate in good yield, while preformed lithium 1-octanolate under the same conditions gave 2,9,16,23-tetraneopentoxyphthalocyanine, but in lower yield at a slower rate. The use of lower-molecular-weight alcohols slowly gave a phthalocyanine in lower yields. Reverse micelle formation when using long-chain alcohols is proposed as a possibility for enhanced phthalocyanine formation at room temperature. 2,9,16,23-Tetrasubstituted phthalocyanines and metallated phthalocyanines were prepared at room temperature from 4-neopentoxyphthalonitrile, 4-bis(4-methoxyphenyl)methoxyphthalonitrile, 4-[1-(4-ethoxy-3-methoxyphenyl)-1-phenyl]methoxyphthalonitrile and phthalonitrile using lithium 1-octanolate in 1-octanol or by the addition, to a solution of the phthalonitrile in ethanol, of calcium turnings or, to a solution of the phthalonitrile in methanol, of magnesium, zinc, iron or copper powder. The tetrasubstituted phthalocyanines produced exhibited a non-statistical distribution of regioisomers, indicating that electronic effects become important in room-temperature cyclotetramerization of phthalonitriles to phthalocyanines.

Long-Chain Branching and Mechanism Controlling Molecular Weight in Hevea Rubber

1999 ◽  
Vol 72 (4) ◽  
pp. 712-720 ◽  
Author(s):  
Jitladda Tangpakdee Sakdapipanich ◽  
Tippawan Kowitteerawut ◽  
Krisda Suchiva ◽  
Yasuyuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Branch Points ◽  
Long Chain Branching ◽  
Linear Character ◽  
Close Relationship ◽  
Deproteinized Natural Rubber ◽  
Long Chain

Abstract The linear character of transesterified deproteinized natural rubber (DPNR-TE) was confirmed by the analysis of terminal groups with NMR and viscometric analyses. The branch content of DPNR rubber from fresh latex was found to range from 0.3 to 1.3 and 0.7 to 3.2, based on tri- and tetra-functionalities, respectively. The plot between the number of branch-points and molecular weight (MW) can be divided into three fractions: (A) the rubber fractions in MW ranging from 2.4×105 to 1.9×106; (B) between 1.9×105 and 2.4×105; and (C) those of MW less than 1.9×105. The fraction (A) showed the number of branch-points per a branched molecule (m) higher than that of fractions (B) and (C). This plot is superimposable with the bimodal molecular-weight distribution (MWD) of Hevea rubber, showing a good coinciding of peak-tops at the high and low MW fractions. It seems likely that there is a close relationship between the number of branch-point and bimodal MWD of natural rubber.

scholarly journals Colouring Matters of the Aphidoidea. XLIV. A Survey of Long-Chain Acid Derivatives From Aphid Lipids Compared With Those of Related Insects. Glycerides of Octa-2,4,6-Trienoic Acid

1978 ◽  
Vol 31 (9) ◽  
pp. 2085 ◽  
Author(s):  
I Addae-Mensah ◽  
DW Cameron
Keyword(s):  
Trienoic Acid ◽  
Comprehensive Survey ◽  
First Time ◽  
Long Chain

A comprehensive survey of lipids representing all families of the Aphidoidea and several related families supports the chemotaxonomic separation of aphids and coccids from the remainder of the Hemiptera. Aphid glycerides are based chiefly on myristate, palmitate and sorbate as noted earlier; octa-2,4,6-trienoate residues are reported for the first time.

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