A molecular weight model in vinyl chloride–divinyl monomer suspension copolymerization before the gel point

1995 ◽  
Vol 56 (10) ◽  
pp. 1221-1230
Author(s):  
Luo Yingwu ◽  
Pan Zuren ◽  
Weng Zhixue ◽  
Huang Zhiming
Keyword(s):  
Molecular Weight ◽  
Vinyl Chloride ◽  
Gel Point ◽  
Weight Model ◽  
Suspension Copolymerization

scholarly journals Preparation of Ultralow Molecular Weight Poly(vinyl chloride) with Submicrometer Particles via Precipitation Polymerization

2019 ◽  
Vol 37 (7) ◽  
pp. 646-653 ◽  
Author(s):  
Peng Cui ◽  
Chang-Tong Song ◽  
Xian-Hong Zhang ◽  
Dong Chen ◽  
Yu-Hong Ma ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Vinyl Chloride ◽  
Precipitation Polymerization ◽  
Poly Vinyl Chloride

Recuring Vulcanizates. I. A Novel Way to Study the Mechanism of Vulcanization

1992 ◽  
Vol 65 (1) ◽  
pp. 211-222 ◽  
Author(s):  
Robert W. Layer
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Zinc Salt ◽  
Current View ◽  
Accelerator Complex ◽  
Exchange Reactions ◽  
Model Compounds ◽  
Vulcanization Process ◽  
Weight Model ◽  
Sulfur Donor

Abstract Vulcanizates, to which a curative is added by swelling, can be recured to easily study a variety of aspects of the vulcanization process, such as maturation, reversion, and even how much accelerator remains active as its zinc salt at the end of the cure. In effect, vulcanizates can be viewed as high-molecular-weight model compounds. In this study, we find that recuring SBR/BR vulcanizates, to which sulfur or the sulfur donor, N,N′ -dithiodimorpholine, is added, develops the same state of cure as the same amount of sulfur (or sulfur donor) added for the initial cure. This suggests that exchange reactions occur between crosslinks and the zinc-sulfur-accelerator complex during the cure and that all of the accelerator remains as its zinc salt at the end of the cure. This last result is interesting, since it is not consistent with the current view that most of the accelerator becomes irreversibly bound to the rubber and lost during the vulcanization of polybutadiene rubbers.

The Chemistry of Phenol-Formaldehyde Resin Vulcanization of EPDM: Part I. Evidence for Methylene Crosslinks

1995 ◽  
Vol 68 (5) ◽  
pp. 717-727 ◽  
Author(s):  
Martin van Duin ◽  
Aniko Souphanthong
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Polymer System ◽  
Phenol Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Hydroxyl Groups ◽  
Reaction Products ◽  
Cure Reaction ◽  
Weight Model

Abstract The application of phenol-formaldehyde resins as crosslinking agents is increasing in importance due to the good high temperature properties of the corresponding vulcanizate and the use in thermoplastic vulcanizates. With respect to the chemistry of phenol-formaldehyde cure (reaction mechanism and structure of crosslink) there are still problems that have to be resolved. The reaction products of the phenol-formaldehyde resin curing of EPDM, contain 2-ethylidene norbornene (ENB) as the third monomer, have been studied. Since such an investigation is rather difficult to perform for the polymer system, a low molecular weight model for EPDM was used: 2-ethylidene norbornane (ENBH). Reaction of ENBH and a resole results in scission of the dimethylene ether bridges, i.e. in degradation of the resole into mono-, bis- and terisooctylphenol units. These are consequently converted into products, consisting of two ENBH molecules linked by mono-, bis- and terisooctylphenol units. The solid resole seems to be a technological solution for storing phenol in combination with formaldehyde. These results support the use of 2-hydroxymethylphenol (HMP) as a low molecular weight model for the resole. At low temperatures and/or short reaction times HMP oligomers (= resoles) and HMP oligomers linked to one ENBH molecule are formed, which are converted into ENBH/HMP (1:1) condensation products. The reaction products of ENBH with both the resole and HMP are shown to contain methylene linked structures, as demonstrated by the formation of monisooctylphenol crosslinks and the presence of residual unsaturation and hydroxyl groups, besides chroman linked structures. This is the first experimental evidence that during phenol-formaldehyde resin cure of rubber, formation of methylene bridges occurs.

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