scholarly journals Study of crystallization behaviour of electron beam irradiated polypropylene and high-density polyethylene

2021 ◽  
Vol 8 (3) ◽  
Author(s):  
Petr Svoboda ◽  
Krunal Trivedi ◽  
Karel Stoklasa ◽  
Dagmar Svobodova ◽  
Toshiaki Ougizawa
Keyword(s):  
Electron Beam ◽  
High Density Polyethylene ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Mechanical Analysis ◽  
High Density ◽  
Crystal Formation ◽  
Scanning Calorimetry ◽  
Irradiation Level ◽  
A Chain

The influence of electron-beam irradiation on polypropylene (PP) and high-density polyethylene (HDPE) was investigated with a focus on crystallization. A high-temperature (200°C) creep test revealed that the HDPE gradually increased cross-linking density in the range 30–120 kGy, while the PP underwent a chain scission which was quantitatively evaluated by gel permeation chromatography. The mechanical properties were measured in the range -150 to 200°C by a dynamic mechanical analysis. A small presence of C=C and C=O bonds was found in the irradiated PP by a Fourier transform infrared spectroscopy. Crystallization kinetics measured by differential scanning calorimetry and hot-stage optical microscopy results were influenced tremendously by irradiation for HDPE and to a lesser extent for PP. Irradiation caused a decrease in both the number of nucleation centres and the growth rate of individual spherulites. Crystallization was analysed in detail with the help of Hoffman–Lauritzen, Avrami and Arrhenius equations. Interestingly an increasing β -crystal formation with an increasing irradiation level was discovered for PP by X-ray diffraction. A generation of defects in the crystalline structure owing to irradiation was discussed.

A detailed characterization of sandalwood-filled high-density polyethylene composites

2020 ◽  
pp. 089270572093915
Author(s):  
Metehan Atagür ◽  
Nusret Kaya ◽  
Tuğçe Uysalman ◽  
Cenk Durmuşkahya ◽  
Mehmet Sarikanat ◽  
...  
Keyword(s):  
High Density Polyethylene ◽  
High Speed ◽  
Loss Modulus ◽  
Weight Fraction ◽  
Mechanical Analysis ◽  
High Density ◽  
Scanning Calorimetry ◽  
Detailed Characterization ◽  
Three Point Bending

In this study, the performance of sandalwood (SW), as an efficient potential filler material for high-density polyethylene (HDPE), was investigated in detail. Firstly, the characterization of SW was conducted by the determination of chemical composition with chemical and thermal analysis methods. The distribution of SW particles, which were used in composite fabrication, was obtained by using a dynamic light scattering analyzer. Then, the composites of SW, whose weight fractions varied from 5% to 20%, with HDPE were produced in a high-speed thermokinetic mixer. The detailed characterization of composites was made by using thermogravimetric analysis, scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, dynamic mechanical analysis (DMA), Fourier transform infrared, thermal conductivity measurements, and tensile and three-point bending tests. From DMA, storage modulus and loss modulus values of the HDPE matrix increased with increasing the weight fraction of SW. It is clearly seen that SW incorporation into HDPE at weight fractions of 5% and 20% exhibited the best improvement in terms of tensile and flexural strengths, respectively. It can be noted that the reinforcement effect of SW for HDPE is more prominent at high temperatures.

Effect of Low Molecular Weight Ethylene Homopolymer on Structure and Properties of Bimodal High Density Polyethylene

2012 ◽  
Vol 217-219 ◽  
pp. 603-608
Author(s):  
Xing Bo Shi ◽  
Ju Lin Wang ◽  
Xiao Ping Cai
Keyword(s):  
Molecular Weight ◽  
High Density Polyethylene ◽  
Gel Permeation Chromatography ◽  
High Density ◽  
Low Molecular Weight ◽  
Structure And Properties ◽  
Scanning Calorimetry ◽  
Processing Properties ◽  
Positive Effect ◽  
Properties Of Composites

The effect of low molecular weight (LMW) ethylene homoploymer on the structure and properties of bimodal high density polyethylene (HDPE) was studied by blending two commercial bimodal HDPE resins (tandem reactor) with two types of LWM ethylene homopolymer. The molecule weight and molecule weight distribution, crystsallinity, rheological and mechanical properties of composites were characterized by high temperature gel permeation chromatography (HT-GPC), differential scanning calorimetry (DSC), capillary rheometer respectively. For composites of bimodal HDPE and LMW ethylene homopolymer, the polydispersity index (PDI) and crystallinity can be effectively increased when reduce the molecular weight of first reactor in tandem reactor. The viscosity of composites decreases at high shear rate. Increasing of LMW component has a positive effect on processing properties and tensile strength, while makes composites brittle.

Long-term closed-loop recycling of high-density polyethylene/flax composites

2018 ◽  
Vol 34 (4) ◽  
pp. 171-199 ◽  
Author(s):  
Nathalie Benoit ◽  
Rubén González-Núñez ◽  
Denis Rodrigue
Keyword(s):  
Mechanical Properties ◽  
Coupling Agent ◽  
High Density Polyethylene ◽  
Closed Loop ◽  
Fibre Length ◽  
Chain Scission ◽  
High Density ◽  
Scanning Calorimetry ◽  
Initial Processing

This work investigates the loss of performance and the recyclability of natural fibre composites for a long-term closed-loop process. Composites based on flax fibres and high-density polyethylene are subjected up to 50 extrusion cycles under constant processing conditions with or without maleic anhydride grafted polyethylene as a coupling agent. The results show that the addition of fibre increases the rigidity but decreases the elongation properties. The initial processing cycle leads to an important decrease of the fibre length and modification of the molecular weight distributions, thus indicating that the addition of fibre enhances chain scission and that fibre breakup mainly happens during the initial processing. The effect of recycling is much less significant, except for the mechanical properties. Negligible variations are observed for density, differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography and impact results. On the contrary, the mechanical properties are strongly affected by recycling as most of them increase with recycling. The addition of a coupling agent improves the composite properties, but this effect disappears with recycling. These trends are associated to a balance between fibre breakup and macromolecular chain scission compared to more homogeneous materials (better fibre distribution) taking place in the materials during recycling. The results show that long-term recycling of composites is possible as their overall performances remain acceptable.

Preparation of Crosslinked High-density Polyethylene Foam Using Supercritical CO2 as Blowing Agent

2017 ◽  
Vol 36 (4) ◽  
pp. 167-182 ◽  
Author(s):  
Hongfu Zhou ◽  
Zhanjia Wang ◽  
Guozhi Xu ◽  
Xiangdong Wang ◽  
Bianying Wen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Density Polyethylene ◽  
Crosslinking Agent ◽  
Volume Ratio ◽  
Gel Permeation Chromatography ◽  
Complex Viscosity ◽  
High Density ◽  
Foaming Properties ◽  
Scanning Calorimetry ◽  
Blowing Agent

Different content of dicumyl peroxide (DCP) acting as a crosslinking agent was mixed with high-density polyethylene (HDPE) in a Haake internal mixer to improve the viscoelasticity and foamability of HDPE. The crosslinked HDPE samples were foamed in a high pressure stainless steel autoclave using CO2 as the physical blowing agent. The molecular weight, crystallization behavior and rheological properties of various HDPE samples were examined by gel permeation chromatography, differential scanning calorimetry, rotational rheometer, and torque rheometer, respectively. The foaming properties of various samples were characterized by scanning electron microscope and densimeter. It was found that with the increasing content of DCP, the molecular weight, crystallization temperature, complex viscosity, and storage modulus of HDPE increased and the crystallization degree of HDPE decreased. When 0.2 phr of DCP was introduced into HDPE, the expansion volume ratio of HDPE showed the highest value, which could be more than 7 times.

scholarly journals Photocatalytic Degradation of High Density Polyethylene using CaO Nanocatalyst

2020 ◽  
Vol 32 (9) ◽  
pp. 2293-2297
Author(s):  
V.S. KUMAWAT ◽  
J.P. BHATT ◽  
D. SHARMA ◽  
S.C. AMETA ◽  
R. AMETA
Keyword(s):  
Functional Groups ◽  
High Density Polyethylene ◽  
Chain Scission ◽  
High Density ◽  
Degree Of Crystallinity ◽  
Infrared Spectrometry ◽  
Scanning Calorimetry ◽  
Fusion Enthalpy ◽  
Before And After ◽  
Scanning Electron

The photodegradation of high density polyethylene (HDPE) using CaO nanoparticles as a catalyst was carried out using 500 W lamp. After exposure, morphology as well as thermal properties of the HDPE was investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). SEM results showed that the HDPE is more prone to crack into small fragments, which indicated a rise in crystallinity with different amounts of catalyst i.e. CaO nanoparticles. The DSC results confirmed the remarkable influence of photodegradation on degree of crystallinity (XC%), fusion enthalpy (ΔH J g-1) and melting temperature (Tm) of HDPE. Infrared spectrometry (FTIR) demonstrated all functional groups of HDPE, present before and after photodegradation. Overall results showed that HDPE was photodegraded into small fragments successfully by using CaO nanopartilces, where different functional groups such as carbonyl, esters and vinyl were obtained during chain scission.

Tuning the Mechanical Properties of High-Density Polyethylene by ECAE Process

2015 ◽  
Author(s):  
Catalin Fetecau ◽  
Felicia Stan ◽  
Laurentiu Sandu ◽  
Florin Susac
Keyword(s):  
Mechanical Properties ◽  
High Density Polyethylene ◽  
Equal Channel Angular Extrusion ◽  
Morphological Changes ◽  
Longitudinal Axis ◽  
High Density ◽  
Scanning Calorimetry ◽  
Plastic Deformations ◽  
The Third ◽  
Indentation Tests

This paper investigates the ability of the equal channel angular extrusion (ECAE) process to induce morphological changes and hence tune the mechanical properties of high-density polyethylene (HDPE). In this study, differential scanning calorimetry (DSC), compression and cylindrical macro-indentation tests have been used to investigate the evolution of the mechanical properties of HDPE processed by ECAE up to four passes via route BC, i.e. counter clockwise 90° billet rotation about its longitudinal axis. It was found that the ECAE process induces significant plastic deformations with changes in the crystalline structure. The ECAE process increased the HDPE crystallinity by 10 to 15%. The number of ECAE passes has a significant effect on the magnitude of the mechanical properties especially on the elastic modulus and yield stress. Young’s modulus and yield strength decreased with increasing the number of ECAE passes and reached a stationary state after the third pass.

Tensile and flammability characterizations of corn straw slagging/high-density polyethylene composites

2019 ◽  
Vol 33 (11) ◽  
pp. 1466-1477
Author(s):  
Qingfa Zhang ◽  
Wenyu Lu ◽  
Liang Zhou ◽  
Donghong Zhang ◽  
Hongzhen Cai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Tensile Strength ◽  
Flame Retardant ◽  
High Density Polyethylene ◽  
Oxygen Index ◽  
High Density ◽  
Corn Straw ◽  
Scanning Calorimetry ◽  
Scanning Electron

Biocomposites were prepared with corn straw slagging (CSS) and high-density polyethylene (HDPE) at four loading levels (10, 20, 30, and 40 wt%) by extrusion method. CSS/HDPE composites were tested by tension, oxygen index meter, differential scanning calorimetry, X-ray diffraction, and the scanning electron microscopy. The scanning electron microscopy showed that CSS was dispersed uniformly in the HDPE matrix and strong interfacial interaction was achieved, which had an important influence on the tensile strength of the composites. The tensile strength of the composites could be improved with proper increase of CSS and reached maximum value at 30 wt% content. Furthermore, the addition of CSS played an important role in improving the flame-retardant ability of CSS/HDPE composites, and the limited oxygen index was 31.26% at 40 wt% content, good flame-retardant effect achieved.

Sepiolite as a nanofiller to improve mechanical and thermal behavior of recycled high-density polyethylene

2020 ◽  
Vol 36 (3) ◽  
pp. 185-195 ◽  
Author(s):  
Negin Farshchi ◽  
Yalda K Ostad
Keyword(s):  
Thermal Behavior ◽  
High Density Polyethylene ◽  
Low Cost ◽  
Process Condition ◽  
Softening Temperature ◽  
High Density ◽  
Plastic Pollution ◽  
Scanning Calorimetry ◽  
Melt Flow Rate ◽  
Recycled Hdpe

Regarding the current demand for controlling plastic pollution, recycling of polymer sounds a promising solution. However, recycling causes mechanical and thermal shortcomings in polymers. Addition of nanoparticles to recycled materials may overcome these shortcomings. Nanocomposites can be achieved either by blending or through polymerization. Sepiolite as a nanoparticle enhances the thermal properties of polymers. In this study, the effect of sepiolite as a nanoparticle has been investigated on the thermal and mechanical behavior of recycled high-density polyethylene (HDPE). Hardness, density, Vicat softening temperature, melt flow rate (MFR), and differential scanning calorimetry has been investigated on recycled HDPE containing different amount of sepiolite. Results showed that both the amount of recycled HDPE and the sepiolite content affect the mechanical and thermal behavior of samples. Increasing the amount of recycled component resulted in increasing of MFR, a slight increase in density, and decrease in Vicat softening point, hardness, melting temperature, and degree of crystallization. As an opposite effect of these to factors on crystallinity of HDPE, sepiolite content has better effects to be considered separately for each recycle content. Sepiolite can be introduced as a low-cost reinforcement filler in recycling industry for tuning new compositions based on process condition, or vice versa.

Stress-Induced Crystal-to-Crystal Transformations in High-Density Polyethylene-Layered Silicate Nanocomposites: A Spectroscopic Study

2005 ◽  
Vol 59 (9) ◽  
pp. 1148-1154 ◽  
Author(s):  
Spiros Tzavalas ◽  
Vasilis G. Gregoriou
Keyword(s):  
High Density Polyethylene ◽  
Mechanical Strain ◽  
Layered Silicate ◽  
High Density ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Polyethylene Matrix ◽  
Dsc Measurements ◽  
Infrared Measurements ◽  
Ft Ir

High-density polyethylene (HDPE)–clay nanocomposites have been prepared using the melt intercalation technique. Organically modified montmorillonite at various loadings (0.5–7%) was used as a nanoadditive. Fourier transform infrared spectroscopy (FT-IR) was utilized for the first time to monitor the stress-induced crystal-to-crystal transformations of the polyethylene matrix with respect to the clay loading as well as to the degree of mechanical strain. In addition, polarized infrared measurements revealed information on both the orientation and the stress-induced distortion of the crystals. It was concluded that the crystal-to-crystal transformations are hindered by the presence of the clay, which also prevented the crystals from orienting even at low clay loadings (1%). Finally, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements confirmed the presence of the stress-induced crystalline structures in agreement with the infrared measurements.

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