Polyurethane one-component foam formulation optimization for low free isocianate monomer content

2016 ◽  
Vol 53 (2) ◽  
pp. 167-179 ◽  
Author(s):  
Ana C Marques ◽  
Helena Dias ◽  
Sandro Matos ◽  
Bruno Sargaço ◽  
Ricardo Simoes ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Flame Retardant ◽  
High Molecular Weight ◽  
Polyurethane Foams ◽  
Toluene Diisocyanate ◽  
Chain Extension ◽  
Methylene Diphenyl Diisocyanate ◽  
Monomer Content ◽  
Aerosol Cans ◽  
One Year

Recent changes in legislation have forced one-component foam producers to drop the amount of free monomeric isocyanate in their polyurethane systems. Also, it is required that commercial polyurethane aerosol cans exhibit at least one year of shelf life and polyurethane foams must be classified as B2 on the fire testing following DIN 4102. This paper reports on a systematic optimization study of polyurethane formulations dedicated to address these current industry requirements. A one-component foam system exhibiting simultaneously all of these parameters was achieved by reacting conventional diols, a relatively low-molecular weight monol (2-ethylhexanol), a flame retardant high-molecular weight monol (tris(bromoneopentyl)alcohol), a methylene diphenyl diisocyanate-based prepolymer (GreenAdduct 13), and a small amount of 2,4′-toluene diisocyanate. The use of monols allows producing prepolymers with low free methylene diphenyl diisocyanate by preventing chain extension and, therefore, avoiding extreme viscosity build-up. Toluene diisocyanate also promotes a lower viscosity inside the aerosol can, which enables the use of high enough quantities of high-molecular weight flame retardant monol to achieve a B2 fire test classification.

A novel high-molecular-weight flame retardant for cotton fabrics

Cellulose ◽  
2020 ◽  
Vol 27 (6) ◽  
pp. 3501-3515 ◽  
Author(s):  
Shidong Liu ◽  
Caiyan Wan ◽  
Yu Chen ◽  
Rui Chen ◽  
Fengxiu Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Flame Retardant ◽  
High Molecular Weight ◽  
Cotton Fabrics

Synthesis, Bromination and Cure of Isobutylene/Isoprene/P-Methylstyrene and Isobutylene/Isoprene/Styrene Terpolymers

2002 ◽  
Vol 75 (1) ◽  
pp. 155-169 ◽  
Author(s):  
Gabor Kaszas ◽  
Binh Tran
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Reactivity Ratios ◽  
Aromatic Rings ◽  
Maximum Torque ◽  
Styrene Monomer ◽  
Hot Air ◽  
Lower Reactivity ◽  
Monomer Content ◽  
Good Agreement

Abstract High molecular weight isobutylene/isoprene/p-methylstyrene and isobutylene/isoprene/styrene terpolymers containing up to 10.6 mol% p-methylstyrene and 3.6 mol% styrene were synthesized using “H2O”/AlCl3 as an initiator/coinitiator system in methylchloride at -95 °C. p-Methylstyrene was found to be uniformly distributed in the chains due to its similar reactivity to isobutylene. In contrast, styrene had a lower reactivity than isobutylene or even isoprene, resulting in low conversion of the styrene monomer. The reactivity ratios obtained were in good agreement with the published values. Up to about 3 mol% styrenic monomer content, the Tg of the terpolymers showed no significant increase. The isoprene units of the terpolymers were brominated by the conventional bromination technique. During bromination, some of the aromatic rings also underwent bromination. The extent of this reaction was found to be much lower in the case of p-methylstyrene than in the case of styrene. The brominated terpolymers were cured using ZnO. The brominated terpolymers displayed much faster cure, higher maximum torque and modulus at the same brominated isoprene concentration than brominated copolymers of isobutylene and isoprene, indicating that the aromatic rings participate in the cure. The brominated terpolymers showed an increased resistance to hot air aging, compared to brominated polymers containing no styrenic termonomer.

Molecular Tailor of Castable Polyurethane Elastomer with Low Free TDI Monomer Content Prepolymer

2010 ◽  
Vol 159 ◽  
pp. 584-588
Author(s):  
Yu Hua Yi ◽  
Zhen Tong
Keyword(s):  
Molecular Weight ◽  
Dynamic Properties ◽  
Toluene Diisocyanate ◽  
Low Molecular Weight ◽  
Polyurethane Elastomer ◽  
Structure And Properties ◽  
Narrow Molecular Weight Distribution ◽  
Compression Set ◽  
Low Viscosity ◽  
Monomer Content

Castable polyurethane elastomer based on polytetramethylene glycol (PTMEG) and 2,4-toluene diisocyanate (TDI) was prepared with low free TDI monomer content prepolymer (LF-prepolymer), the structure and properties of the prepolymers and corresponding elastomers were characterized. The result showed that, LF-prepolymer exhibit low viscosity, low molecular weight and narrow molecular weight distribution. The polyurethane prepolymer based on LF-prepolymer show higher bashore rebound, lower compression set and better dynamic properties.

Apparently Nonfunctioning Metastases of Parathyroid Carcinoma

1987 ◽  
Vol 73 (2) ◽  
pp. 191-193 ◽  
Author(s):  
Paolo Manente ◽  
Maurizio Cecchettin ◽  
Domenico Infantolino ◽  
Giancarlo Foscolo ◽  
Nicola Conte
Keyword(s):  
Molecular Weight ◽  
Lymph Nodes ◽  
High Molecular Weight ◽  
Parathyroid Carcinoma ◽  
Immunohistochemical Study ◽  
Gel Filtration ◽  
Parathyroid Tumor ◽  
Parathyroid Cancer ◽  
Normal Limits ◽  
One Year

A 41-year-old woman was operated on for severe hyperparathyroid syndrome. At surgery a parathyroid tumor with the histopathologic pattern of carcinoma was found. After surgery serum calcium settled within normal limits (10.5 mg/dl, N.V. 8.5–10.8), whereas parathormone and calcitonin reached progressively high levels, respectively 400 ng/dl (N.V. up to 250) and 500 pg/ml (N.V. up to 100 ng/ml). Serum ultrafiltration analysis for parathormone and calcitonin showed many peaks of immunoreactivity with high molecular weight of both hormones. One year after surgery, metastases developed in the lymph nodes of the neck and the mediastinal, pleural and pancreatic regions. After death for tumor wasting, immunohistochemical study of the tumoral tissue with the peroxidase-antiperoxidase technique showed a relatively high density of calcitonin-containing cells. The findings in this case suggest that: a) several cells in this parathyroid cancer could secrete both parathormone and calcitonin; b) the hormonal secretion was impaired as suggested by the high molecular weight of both hormones found at gel-filtration analysis; c) the macromolecular profile of parathormone could explain the apparent function of the parathyroid cancer.

scholarly journals When Attempting Chain Extension, Even Without Solvent, It Is Not Possible to Avoid Chojnowski Metathesis Giving D3

Molecules ◽  
2021 ◽  
Vol 26 (1) ◽  
pp. 231
Author(s):  
Mengchen Liao ◽  
Yang Chen ◽  
Michael A. Brook
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Efficient Method ◽  
Heterogeneous Reaction ◽  
Chain Extension ◽  
Molecular Weights ◽  
Second Growth ◽  
The One ◽  
Hydrolysis Of ◽  
Homogeneous Reactions

A simple, mild and efficient method to prepare HSi- or HOSi-telechelic, high-molecular-weight polydimethylsiloxane polymers (to 41,600 g·mol−1) using the one-shot hydrolysis of MHMH is reported; titration of the water allowed for higher molecular weights (to 153,900 g·mol−1). The “living” character of the chain extension processes was demonstrated by adding a small portion of MHMH and B(C6F5)3 (BCF) to a first formed polymer, which led to a ~2-fold, second growth in molecular weight. The heterogeneous reaction reached completion in less than 30 min, much less in some cases, regardless of whether it was performed neat or 50 wt% in dry toluene; homogeneous reactions in toluene were much slower. The process does not involve traditional redistribution, as judged by the low quantities (<3%) of D4 produced. However, it is not possible to avoid Chojnowski metathesis from MHDDMH giving D3, which occurs competitively with chain extension.

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