scholarly journals Melt Blending Modification of Commercial Polystyrene with Its Half Critical Molecular Weight, High Ion Content Ionomer, Poly(styrene–ran–cinnamic Acid) Zn Salt, toward Heat Resistance Improvement

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 584
Author(s):  
Zixin Yu ◽  
Jie Wang ◽  
Peihua Li ◽  
Dachuan Ding ◽  
Xuan Zheng ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Heat Resistance ◽  
Cinnamic Acid ◽  
Average Molecular Weight ◽  
Softening Temperature ◽  
Melt Blending ◽  
Ion Content ◽  
Critical Weight ◽  
Critical Molecular Weight ◽  
Cross Links

A half-critical weight-average molecular weight ( M ¯ w ) (approximately 21,000 g mol−1), high-ion-content Zn-salt poly(styrene–ran–cinnamic-acid) (SCA–Zn) ionomer was successfully synthesized by styrene–cinnamic-acid (10.8 mol %) copolymerization followed by excess-ZnO melt neutralization. At 220 °C, the SCA–Zn’s viscosity was only approximately 1.5 magnitude orders higher than that of commercial polystyrene (PS) at 102 s−1, and the PS/SCA–Zn (5–40 wt %) melt blends showed apparently fine, two-phased morphologies with blurred interfaces, of which the 95/5 and 90/10 demonstrated Han plots suggesting their near miscibility. These indicate that any PS–(SCA–Zn) processability mismatch was minimized by the SCA–Zn’s half-critical M ¯ w despite its dense ionic cross-links. Meanwhile, the SCA–Zn’s Vicat softening temperature (VST) was maximized by its cross-linking toward 153.1 °C, from that (97.7 °C) of PS, based on its half-critical M ¯ w at which the ultimate glass-transition temperature was approximated. Below approximately 110 °C, the PS/SCA–Zn (0–20 wt %) were seemingly miscible when their VST increased linearly yet slightly with the SCA–Zn fraction due to the dissolution of the SCA–Zn’s cross-links. Nevertheless, the 60/40 blend’s VST significantly diverged positively from the linearity until 111.1 °C, revealing its phase-separated morphology that effectively enhanced the heat resistance by the highly cross-linked SCA–Zn. This work proposes a methodology of improving PS heat resistance by melt blending with its half-critical M ¯ w , high-ion-content ionomer.

scholarly journals Effect of Epoxy Chain Extender on the Properties of Polylactic Acid

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Molecular Weight ◽  
Heat Resistance ◽  
Polylactic Acid ◽  
Epoxy Group ◽  
Average Molecular Weight ◽  
Testing Machine ◽  
Softening Temperature ◽  
Chain Extension ◽  
Melt Strength ◽  
Melt Index

Modification of polylactic acid (PLA) by chain extension is a method used to improve its melt strength and heat resistance. In this study, the chemical structure, viscosity average molecular weight, thermal properties, melt viscosity, mechanical properties and Vicat softening temperature of PLA before and after the modification were measured by Fourier-transform infrared spectroscopy (FTIR), a viscometer (Mv), differential scanning calorimetry (DSC), a melt index instrument (MI), a rotary rheometer, a universal material testing machine, and a Vicat softening temperature tester, respectively, to characterize the effect of chemically modifying PLA with KL-E4370. The experimental results showed that the epoxy group contained in KL-E4370 reacted with the carboxyl group of PLA. In addition, the modified PLA showed increased molecular weight, enhanced melt strength, decreased melt fluidity, a significantly decreased melt index, significantly increased complex viscosity and modulus, enhanced impact and tensile strengths, and an increased Vicat softening temperature. When the content of KL-E4370 was 0.1%, the viscosity average molar mass increased from 2.88×103 g/mol (that of neat PLA) to 4.02×103 g/mol, the crystallinity increased from 17.0% (that of neat PLA) to 32.5%, the melt index decreased from 6.0 g/10 min (that of neat PLA) to 2.2 g/10 min, the Vicat softening temperature increased from 67.9 °C (that of neat PLA) to 160.1 °C, and the heat resistance of PLA was improved significantly

Hydroxyl-functionalized resin: preparation, characterization, parameter optimization and property prediction

2018 ◽  
Vol 47 (3) ◽  
pp. 236-245 ◽  
Author(s):  
Appala Naidu Uttaravalli ◽  
Srikanta Dinda
Keyword(s):  
Molecular Weight ◽  
Batch Reactor ◽  
Average Molecular Weight ◽  
Hazardous Materials ◽  
Softening Temperature ◽  
Alkali Concentration ◽  
Operating Parameters ◽  
Compatibility Study ◽  
Content Type ◽  
Hydroxyl Value

Purpose The purpose of the present study is first to develop a hydroxyl-functionalized ketonic resin for coating applications and to establish a standard characterization protocol; second, to quantify the effects of various operating parameters on resin properties and to develop mathematical models to predict the product properties; and third, to carry out the compatibility study between the in-house developed resins and commercially available resins. Design/methodology/approach Self-polymerization reactions were conducted in a batch reactor. Effects of reaction time, temperature, catalyst concentration and reactor pressure on product properties have been studied. Hydroxyl value, iodine value, solubility, rheology, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and the X-ray diffraction (XRD) analysis were carried out to characterize the product properties. Mark–Houwink correlation was used to predict molecular weight of the resins. Findings The study shows that hydroxyl value and softening temperature (ST) of the product increased with the increase of reaction temperature, duration of reaction and alkali concentration. However, the solubility value of the resins decreased with the increase of temperature, time and alkali concentration. Regression models were developed to predict the optimum conditions for obtaining a desired quality of resin. The number-average molecular weight of the developed resins was in the range of 450-1150. The products are thermally stable up to around 200°C, and adequately soluble in many commercial solvents. Research limitations/implications The ketonic resin can be used as a substitute of phenolic resins which are prepared from more hazardous materials monomers such as phenolic and aldehyde compounds. Practical implications The resin can be used as a substitute of more hazardous materials such as phenolic and aldehyde compounds. Originality/value This paper details the synthesis of ketonic resin from cyclohexanone and its compatibility. It also investigates the optimization of operating parameters to obtain a desire product.

Influence of Operation Procedures on Vicat Softening Temperature of Thermoplastic Materials

2011 ◽  
Vol 291-294 ◽  
pp. 1820-1824
Author(s):  
Hou Bu Li ◽  
Qi Li ◽  
Mi Lin Yan
Keyword(s):  
Molecular Weight ◽  
Heat Resistance ◽  
High Molecular Weight ◽  
Initial Temperature ◽  
Softening Temperature ◽  
Initial Test ◽  
Waiting Period ◽  
Waiting Periods ◽  
Weight Carrying ◽  
Ultra High Molecular Weight

Vicat softening temperature (VST) is one of the most important parameters to evaluate heat resistance of thermoplastic materials. However, the initial test temperature is difficult to control, which may reduce the testing efficiency and the precision of VST. Moreover, according to the procedure of GB/T 1633-2000, the specimen should be placed horizontally under the indenting tip of unloaded rod for 5min. After that, add a sufficient weight to the weight-carrying plate, and then set the penetration indicator to zero to start the experiment. However, the waiting period between adding the extra mass and starting the test may be different during the real operation. Such longer or shorter waiting periods can also influence the tested VST. In this paper, ultra-high molecular weight polyethylene (UHMWPE) was used to discuss the influence of initial temperature and waiting period on its final VST. The results show that, in order to satisfy the practices of standard GB/T 1633-2000, the initial temperature and the waiting period should not exceed 40°C and 25min, respectively.

Effect of the molecular weight on the lower critical solution temperature of poly(N,N-diethylacrylamide) in aqueous solutions

2001 ◽  
Vol 79 (12) ◽  
pp. 1870-1874 ◽  
Author(s):  
D G Lessard ◽  
M Ousalem ◽  
X X Zhu
Keyword(s):  
Molecular Weight ◽  
Lower Critical Solution Temperature ◽  
Molar Mass ◽  
Average Molecular Weight ◽  
Solution Temperature ◽  
Low Molecular Weight ◽  
Fractional Precipitation ◽  
Critical Solution Temperature ◽  
Molecular Weight Dependence ◽  
Critical Molecular Weight

The molecular weight dependence of the lower critical solution temperature of poly(N,N-diethylacrylamide) was studied with 11 samples of the polymer with a number-average molecular weight (Mn) ranging from 9.6 × 103 to 1.3 × 106 g mol–1 and relatively narrow polydispersity indices from 1.19 and 2.60. These samples were obtained by fractional precipitation of the polymer. LCST values of polymers were measured by turbidimetry and microcalorimetry. An inverse dependence of LCST on the molar mass was found and the LCST of the samples remained more or less a constant above a critical molecular weight of ca. 2 × 105 g mol–1. The enthalpy and the entropy changes as well as the LCST of the polymer depend strongly on the molar mass of the polymer, especially in low molecular weight range.Key words: poly(N,N-diethylacrylamide), LCST, thermosensitive, phase diagram, effect of molecular weight.

The Cross-Linking of Rubber by Pile Radiation

1955 ◽  
Vol 28 (1) ◽  
pp. 1-11
Author(s):  
Arthur Charlesby
Keyword(s):  
Molecular Weight ◽  
Radiation Dose ◽  
Average Molecular Weight ◽  
High Energy ◽  
Cross Linking ◽  
Gel Formation ◽  
Gel Fraction ◽  
Cross Links ◽  
The Cross ◽  
The Relationship

Abstract The degree of cross-linking produced in a rubber by high-energy radiation is proportional to the radiation dose. Unit radiation, as defined in the text, links 1.1 per cent of the isoprene units. The distribution of molecular weight prior to cross-linking agrees with a Poisson distribution. Gel formation begins for γ=0.5. From the radiation dose required to initiate gel formation, the initial average molecular weight can be deduced. The increase of gel fraction with radiation dose follows the relationship deduced theoretically in the first part of the article. Measurement of gel fraction gives an alternative method of calculating the initial average molecular weight. Where some cross-linking is present in the rubber prior to cross-linking, this may be evaluated. In accordance with the theory presented in the article, the viscosity of the sol fraction rises initially, then decreases as the radiation dose increases. This provides a third method of measuring molecular weight, or of relating viscosity to molecular weight, which can be deduced from measurement of gel fraction. The swelling of very lightly cross-linked gel has been compared with the Flory-Huggins relationship, which is found to hold down to very lightly cross-linked gels for which the cross-linking index is only 0.2. To obtain this agreement, it is necessary to consider the swelling of the dry gel, rather than the whole specimen, and to ignore the cross-links required to form the gel itself.

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

Sign in / Sign up

Export Citation Format

Share Document