scholarly journals Improving the Thermal Aging Resistance of γ-Vulcanized Polybutadiene Rubber (BR)/Nature Rubber (NR) Blends with Sulfur Added

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zongyuan Mao ◽  
Wenzhao Wang ◽  
Gang Mao
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Thermal Resistance ◽  
Thermal Aging ◽  
Irradiation Dose ◽  
Γ Radiation ◽  
Degradation Temperature ◽  
Polybutadiene Rubber ◽  
Aging Resistance

In this paper, sulfur was added into polybutadiene rubber/nature rubber (BR/NR) blends for improving the resistance of thermal aging. BR/NR blends with sulfur were vulcanized by 60Co γ radiation with different irradiation doses. Afterwards, the specimens underwent thermal aging by using air oven, the non-aged specimens without such process. It was found that the crosslink degree of BR/NR blends increased with the increase in the irradiation dose, according to the results of gel and molecular weight between crosslinks (Mc). Furthermore, the crosslink degree of BR/NR blends increased after thermal aging. This made the mechanical properties and initial degradation temperature (IDT) of aged BR/NR blends improve. Sulfur could improve thermal resistance of γ-irradiated BR/NR blends. Finally, the possible mechanism of improved crosslink degree in aged BR/NR blends was illuminated in the paper.

scholarly journals Effect of environmental conditions on the durability of polycarbonate for the protection of cultural heritage sites

2019 ◽  
Vol 17 (4) ◽  
pp. 228080001988162
Author(s):  
Laura Ascione ◽  
Maria Chiara Mistretta ◽  
MariaPia Pedeferri ◽  
Francesco Paolo La Mantia
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Cultural Heritage ◽  
Physical And Mechanical Properties ◽  
Oxidation Reactions ◽  
Yellowness Index ◽  
Photo Oxidation ◽  
Heritage Sites ◽  
Degradation Temperature ◽  
Moisture Conditions

Polycarbonate is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. However, polycarbonate degrades under environmental weathering with a significant decrease of physical and mechanical properties and loss of transparency. In this work, the contemporary presence of ultraviolet irradiation and different temperature and moisture conditions have been taken into account to study the environmental degradation of this polymer with regard to its mechanical and optical properties. The photo-oxidation reactions cause a decrease in the molecular weight and the formation of many oxygenated species. The hydrolytic scission, instead, gives rise to a remarkable reduction in the molecular weight. These two different degradation mechanisms do not seem interconnected because at the lowest degradation temperature and high humidity levels, the reduction of the molecular weight is more pronounced than that observed at the highest temperature but at a lower humidity level. Transparency decreases with the degradative processes, but even after severe degradation the loss of transparency is only about 10%. The yellowness index increases during the first stages of degradation, which has been attributed to the fast formation of carbonyl groups due to photo-oxidation.

scholarly journals Effect of Sizing Agents on Surface Properties of T800 Grade CF and Thermal Aging Time on Mechanical Properties of T800 Grade CF/Epoxy Composites

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Tian Yang ◽  
Yan Zhao ◽  
Hansong Liu ◽  
Shu Xiong
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Aging Time ◽  
Surface Properties ◽  
Thermal Aging ◽  
Ageing Time ◽  
Flexural Modulus ◽  
Thermal Ageing ◽  
Epoxy Composites ◽  
Interlaminar Shear

This paper investigates the effect of sizing agent molecular weight on carbon fiber (CF) surface properties and the effect of thermal aging time on mechanical properties of CF/epoxy composites. The surface properties of three CCF800 CF samples with varying sizing agent molecular weight were characterized by surface morphology, surface roughness, chemical functional groups, and element composition. The results showed that the sample with low molecular weight exhibited low roughness and high proportion of activated carbon atoms. The flexural strength, flexural modulus, and interlaminar shear strength of CCF800/5228 composites were measured at 25°C and 150°C by thermal ageing time 0, 100 h, 250 h, 500 h, and 1000 h. The results showed that the thermal aging time up to 1000 h had little effect on the flexural modulus, and the interlaminar shear performance at 150°C showed a trend of increasing at the beginning and then decreasing.

scholarly journals Thermal and mechanical properties of ultrahigh molecular weight polyethylene/high-density polyethylene/polyethylene glycol blends

2013 ◽  
Vol 33 (7) ◽  
pp. 599-614 ◽  
Author(s):  
Mazatusziha Ahmad ◽  
Mat Uzir Wahit ◽  
Mohammed Rafiq Abdul Kadir ◽  
Khairul Zaman Mohd Dahlan ◽  
Mohammad Jawaid
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Polyethylene Glycol ◽  
Impact Strength ◽  
High Density Polyethylene ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
High Density ◽  
Mechanical And Thermal Properties ◽  
Degradation Temperature ◽  
Ultrahigh Molecular Weight

Abstract Blends of ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) provide adequate mechanical properties for biomedical application. In this study, the mechanical and thermal properties of UHMWPE/HDPE blends with the addition of polyethylene glycol (PEG) prepared via single-screw extruder nanomixer were investigated. The UHMWPE/HDPE blends exhibit a gradual increase in strength, modulus, and impact strength over pure polymers, suggesting synergism in the polymer blends. The elastic and flexural modulus was increased at the expense of tensile, flexural, and impact strength for the blends containing PEG. The degradation temperature of UHMWPE was improved with the incorporation of HDPE due to good thermal stability of HDPE. HDPE improved the dispersibility of PEG in matrix, consequently reduced the surface area available for the kinetic effects, and reduced the degradation temperature. The morphology analysis confirmed the miscibility between UHMWPE and HDPE and the changes in polymer structure with the presence of PEG modify the thermal behavior of the blends. The mechanical properties of the blends that are underlying values for the design of implant material show the potential used as biomedical devices.

scholarly journals Melt- vs. Non-Melt Blending of Complexly Processable Ultra-High Molecular Weight Polyethylene/Cellulose Nanofiber Bionanocomposite

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 404
Author(s):  
Nur Sharmila Sharip ◽  
Hidayah Ariffin ◽  
Tengku Arisyah Tengku Yasim-Anuar ◽  
Yoshito Andou ◽  
Yuki Shirosaki ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Tensile Strength ◽  
Yield Strength ◽  
Young’S Modulus ◽  
High Molecular Weight ◽  
Melt Processing ◽  
Cellulose Nanofiber ◽  
Melt Blending ◽  
Ultra High Molecular Weight

The major hurdle in melt-processing of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite lies on the high melt viscosity of the UHMWPE, which may contribute to poor dispersion and distribution of the nanofiller. In this study, UHMWPE/cellulose nanofiber (UHMWPE/CNF) bionanocomposites were prepared by two different blending methods: (i) melt blending at 150 °C in a triple screw kneading extruder, and (ii) non-melt blending by ethanol mixing at room temperature. Results showed that melt-processing of UHMWPE without CNF (MB-UHMWPE/0) exhibited an increment in yield strength and Young’s modulus by 15% and 25%, respectively, compared to the Neat-UHMWPE. Tensile strength was however reduced by almost half. Ethanol mixed sample without CNF (EM-UHMWPE/0) on the other hand showed slight decrement in all mechanical properties tested. At 0.5% CNF inclusion, the mechanical properties of melt-blended bionanocomposites (MB-UHMWPE/0.5) were improved as compared to Neat-UHMWPE. It was also found that the yield strength, elongation at break, Young’s modulus, toughness and crystallinity of MB-UHMWPE/0.5 were higher by 28%, 61%, 47%, 45% and 11%, respectively, as compared to the ethanol mixing sample (EM-UHMWPE/0.5). Despite the reduction in tensile strength of MB-UHMWPE/0.5, the value i.e., 28.4 ± 1.0 MPa surpassed the minimum requirement of standard specification for fabricated UHMWPE in surgical implant application. Overall, melt-blending processing is more suitable for the preparation of UHMWPE/CNF bionanocomposites as exhibited by their characteristics presented herein. A better mechanical interlocking between UHMWPE and CNF at high temperature mixing with kneading was evident through FE-SEM observation, explains the higher mechanical properties of MB-UHMWPE/0.5 as compared to EM-UHMWPE/0.5.

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.

Sign in / Sign up

Export Citation Format

Share Document