Intrinsic viscosity‐molecular weight relationship for polystyrene

Goldberg, and Israel; Hohenstein, W. P.; Mark, H.

doi:10.1002/pol.1947.120020506

Cited by 124 publications

(34 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Absorptions at 3.36 and 3.42 ,u are usually a result of carbon-hydrogen bond stretching. The intense absorption at 6.1 ,u is attributed to the carbonyl group, which usually absorbs at 5.76 to 5.84 microns but is displaced to longer wav elength in nylon 66 and amides in general probably as a re6ult of interaction between the carbonyl and imine groups [42]. The intense absorption at 6.46 ,u may result from N-H bending and could cause a harmonic effect at 3.2 ,u. The doublet band at 6.8 and 7.05 ,u has been observed in diallyl adipate [45].…”

Section: (B) Pyrolysismentioning

confidence: 99%

Mechanism of the degradation of polyamides

Achhammer¹,

Reinhart²,

Kline³

1951

J. RES. NATL. BUR. STAN.

View full text Add to dashboard Cite

Films of polyamides were exposed to heat, ultraviolet radiant energy, and different atmospheric conditions. The degradation products were collected in some cases and analyzed by mass spectrometric techniques. The unexposed and exposed specimens were examined by the following techniques to obtain information concerning the changes in chemical and physical structure of the polymer: infrared absorption, ultraviolet absorption , viscosity of solutions, measurement of dielectric constant and dissipation factor, photomicrography, X-ray diffraction, electron microscopy, electron diffraction, and effect of organic liquids. In addition, pyrolysis studies were made and some physical properties were determined. The results of the investigation show clearly that no single method gives a complete picture but that the results from several of the methods give an insight into the mechanism of degradation of poly ami des.Polyamide molecules are relatively unaffected by exposure to moderate temperature (60 0 C). However, loss of water and other volatile materials may cause changes in physcial properties. The effects of exposure to ultraviolet radiant energy are more pronounced, and degradation of the polyamide molecule occurs with accompanying loss of water and other volatile materials that act as plasticizers.The results of this inves tigation show that the general course of the degradation of polyamides is as follows :1. The polymer mol ecules break at the C -N bond of the peptide group creating smaller polymer molecules with the same unit of chemical structure. The fragments broken out are evolved as carbon dioxide, carbon monoxide, water, and hydrocarbons.2. The degree of crystallinity or local order changes, including alterations in hydrocarbon packing, dipole rearrangement, and hydrogen bridging.3. The amount of strongly bound water and/or organic liquids changes. These materials are probably bound by hydrogen bridging to the oxygen of the peptide group. They act as plasticizers for the polyamides. r. IntroductionOne of the major problems facing the plastics industry is the degradation of some plastics when exposed to certain service conditions. This problem has been investigated extensively by accelerated tests involving one or more physical properties. While empirical investigations of this type give information of value, they yield little or no information on the basic changes in the material. As a result, the value of the information now aVi),ilable is not only limited, but in too many instances the information cannot be used to predict behavior in actual service [1).1 The physical changes observed during degradation may result from (1) changes in the chemical structure of the plastic material, and (2) loss or changes in the compounding ingredients. The logical method of attack is to determine the specific chemical reactions involved in the degradation of the plastic and how these reactions are affected by the intensity of the conditions encountered.The degradation of the plastic type of polyamides was investigated as p...

show abstract

Section: (B) Pyrolysismentioning

confidence: 99%

Mechanism of the degradation of polyamides

Achhammer¹,

Reinhart²,

Kline³

1951

J. RES. NATL. BUR. STAN.

View full text Add to dashboard Cite

show abstract

“…16 This calculated molecular weight gives an idea of the extent of the polymerisation and hence an idea of the chain extensions in the various solvents employed as polymerisation media. The details furnished in Table I in this connection clearly indicate THF to be the most ideal solvent for polymerisation since chain extension takes place in this solvent more than in others.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Low-Temperature Stable Polymers. I. Chain-Extended Poly(tetrahydrofuran–urethane)

Rajendran

Mahadevan

Srinivasan

1981

Polym J

View full text Add to dashboard Cite

ABSTRACT:Tetrahydrofuran was polymerised with boron trifuoride etherate (BF3 · Et20) and terminated with hydrobromic acid to give the bromide-terminated prepolymer, which, on further reaction with ketal derivative of glycerol and subsequent hydrolysis, gave tetrahydroxylterminated polytetrahydrofuran. The prepolymer was chain-extended with tolylenediisocyanate and hexamethylenediisocyanate in six different solvents to give cross-linked polyurethane. These polymers were characterised by infrared, viscosity and thermogravimetric analysis. The glasstransition temperature, the tensile strength at break, and elongation were also determined.KEY WORDS The diisocyanate polymer chain-extension technique has been utilised in many fields of polymer technology to produce materials such as foams, coatings, castable elastomers/ and cryogenic adhesives.2 The coreactants that have been used are hydroxyl-terminated polyesters, polyethers, and some naturally occurring products such as castor oil. For many reasons, such as mix-fluidity and improved low-temperature flexibility, polyethers are preferred in urethane technology. The three principal types of polyethers used in work up to the present are poly(ethylene glycol)s, poly(propylene glycol)s and poly(tetrahydrofuran glycol)s, and the glycols obtained from the copolymerization of cyclic ethers. 3 The tetrahydrofuran(THF)-based polyurethanes (PU) were found to have the best physical and low-temperature properties. 4 Cross-linking was normally introduced into the urethane-extended polymers through the use of intermediates possessing more than two functional groups or through secondary reactions of the isocyanate group with -NH-gr,oups derived from the primary reactions of the isocyanate group. The polyfunctionality could also be introduced in the glycol intermediates by polymerising the cyclic ethers with initiators having more than two functiona! groups. 5 • 6 The introduction of cross-linking into the polymers results in a polymer having a low glass-transition temperature, a decrease in elongation; the cross-linking has an insignificant effect on tensile strength. EXPERIMENTAL Materials and MethodsBoron trifluoride etherate (Fluka AG), tolylenediisocyanate (TDI) (2: 4 isomer Reidel), and hexamethylenediisocyanate (HMDI) (Fluka AG) were all distilled prior to use in the experiments. The tetrahydrofuran, triethylamine, and dioxane (AR samples) were purified as usual. 7 The polymerisation solvents, acetonitrile, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and dichloromethane in analar qualities were dried by being kept overnight with phosphorous pentoxide, filtered, and fractionated in the reported boiling ranges. The ketal derivative of glycerol was prepared from dry glycerol and acetone with ptoluenesulfonic acid as catalyst. 8 The infrared spectra of polymers were taken by a Perkin-Elmer 257 spectrometer (KBr pellets and Nujol mulls). The intrinsic-viscosity measurements 99

show abstract

“…2 varies between 0.5 and 0.8. Although a function of the solvent, in this study we use a value of a = 0.71 for polystyrene [31], a = 0.81 for poly(methyl methacrylate) [32], and a = 0.68 for poly(ethylene glycol) polymer solutions [33], regardless of the solvent that is used. Also note that the magnitude of parameter K plays no role in the determination of the activation energy of viscous flow of the solution, as it is a scaling factor to estimate the solution intrinsic viscosity.…”

Section: Model Developmentmentioning

confidence: 99%

Non-equilibrium Thermodynamic Model for the Estimation of the Soret Coefficient in Dilute Polymer Solutions

Eslamian

Saghir

2010

Int J Thermophys

View full text Add to dashboard Cite

In the present work a theoretical model based on linear non-equilibrium thermodynamics and the concept of Eyring's activation energy of viscous flow is developed to estimate the Soret coefficient in dilute polymer solutions. The model is capable of predicting a sign change in the Soret coefficient, when the polymer molecular weight changes. The key part of the model is the way that the net heat of transport of the polymer molecules is simulated. Employing the Mark-Houwink equation, which correlates the polymer solution intrinsic viscosity with its molecular weight, the net heat of transport of the polymer is correlated with the activation energy of viscous flow of the polymer's monomer in the liquid state, the Mark-Houwink solution parameter, and the polymer molecular weight. The model is evaluated against the experimental data, where qualitative and in some cases quantitative agreement is found.

show abstract

Intrinsic viscosity‐molecular weight relationship for polystyrene

Cited by 124 publications

References 13 publications

Mechanism of the degradation of polyamides

Mechanism of the degradation of polyamides

Synthesis of Low-Temperature Stable Polymers. I. Chain-Extended Poly(tetrahydrofuran–urethane)

Non-equilibrium Thermodynamic Model for the Estimation of the Soret Coefficient in Dilute Polymer Solutions

Contact Info

Product

Resources

About