Studies on Structure and Properties of HDPE Functionalized Through Ultraviolet Irradiation and Its Blends with CaCO3

Abstract

The structure and properties of high-density polyethylene (HDPE) functionalized through ultraviolet irradiation in air and its blends with CaCO₃ were studied by Fourier transfer infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurement, Molau test, and mechanical properties test. The experimental results reveals that oxygen-containing groups such as C = O and C - O were introduced onto the molecular chains of HDPE through ultraviolet irradiation in air, and the groups' concentration increases with irradiation time. After irradiation, the water contact angle of HDPE becomes smaller, showing that the hydrophilicity of irradiated HDPE increases. Compared with those of HDPE/CaCO₃ blend, the dispersion of CaCO₃ particles in irradiated HDPE/CaCO₃ blend, the interface interaction between CaCO₃ particles and irradiated HDPE matrix, and the mechanical properties of irradiated HDPE/CaCO₃ blend are improved due to the introduction of polar groups.     

Mechanical properties and interfacial interaction of CaCO3 filled HDPE compatibilized with HDPE functionalized by ultraviolet irradiation

The mechanical properties of CaCO₃ filled high density polyethylene (HDPE) compatibilized with ultraviolet (UV) irradiated HDPE (uHDPE) were studied and the interfacial interactions between CaCO₃ and the polymers were evaluated by SEM, the Molau test, and ESCA. UV irradiation in air introduces the following functional groups on HDPE: >COOH, >C?O, ? OOH and ? OH. The concentration of these groups increases with irradiation time. The addition of a small amount (<10% by wt) of uHDPE to the HDPE/CaCO₃ improves the tensile and impact strength. For example, the addition of 3% HDPE irradiated for 500 hours (u500HDPE) increases the tensile and impact strength of HDPE/CaCO₃ from 16.7 MPa and 210 J/m to 25.2 MPa and 430 J/m, respectively. Chemical reactions between uHDPE and CaCO₃ promote interactions between HDPE and CaCO₃. The morphology of the compatibilized compound is nearly homogenous, and no CaCO₃ sediment was observed in a hot xylene solution of HDPE/u500HDPE/CaCO₃ when the content of u500HDPE exceeded 30% (wt).     

Effect of storage on ultraviolet irradiated HDPE

Abstract

Oxygen containing groups such as C=O and C–O were introduced onto high density polyethylene (HDPE) chains by ultraviolet (irradiated at 70°C and different light intensities in air). The contents of oxygen containing groups were unchanged after storage, indicating that these groups were stable in HDPE chains. The water contact angles of the irradiated HDPE at different light intensities after storage were equivalent to those of the irradiated HDPE before storage. Small quantity of the irradiated HDPE at different light intensities before and after storage as a compatibiliser were added into the HDPE/CaCO₃ composite respectively, and the HDPE/CaCO₃/irradiated HDPE before and after storage composite were prepared respectively. The tensile strength and the impact strength of HDPE/CaCO₃/irradiated HDPE after storage composite were similar to those of the HDPE/CaCO₃/irradiated HDPE before storage composite. The irradiated HDPE after storage was an efficacious compatibiliser.     

Preparation and properties of HDPE/CaCO3/OMMT ternary nanocomposite

A series of binary composites based on HDPE (high density polyethylene) and nanoinorganic particles such as nano‐CaCO₃ and OMMT (organic montmorillonite) were prepared. Their properties including tensile, impact strength, and some thermal properties were tested. The results showed that binary composite has partial improvement in mechanical properties compared with pure HDPE. A ternary composite nano‐CaCO₃/OMMT/HDPE was prepared and characterized. It was found that the mechanical and thermodynamic properties of this ternary composite have been enhanced greatly compared with both pure HDPE and binary composites. The tensile strength, Young's modulus, flexural strength, elastic modulus, and impact strength of nano‐CaCO₃/OMMT/HDPE were increased 124.6%, 302.7%, 73.86%, 58.97%, and 27.25%, respectively. The DMA test results showed that the mechanical properties of ternary composite were increased because of the limitation on the movement of HDPE due to inorganic particles. The synergistic effect introduced by nanoparticles may play an important role in all these processes. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Studies on high density polyethylene (HDPE) functionalized by ultraviolet irradiation and its application

The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m^?2 and 45 W m^?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m^?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m^?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m^?1 to 30.2 MPa and 158 J m^?1, respectively. Copyright © 2003 Society of Chemical Industry     

Studies on quick functionalization of polyethylene through ultraviolet irradiation and its composites

The oxygen-containing groups such as C–O, C=O, and C(=O)O were quickly introduced onto high-density polyethylene (HDPE) chains through ultraviolet irradiation in ozone atmosphere, and the functionalized HDPE was prepared. The content of the C–O, C=O, and C(=O)O groups increased with increasing the irradiation time. There was no gel in the functionalized HDPE. Compared with that of HDPE, the crystal form, cell parameters, and face space of the functionalized HDPE did not change, and its melting temperature and thermal stability decreased, while the crystallinity, hydrophilicity, and melt index increased. The functionalized HDPE/Sericite–Tridymite–Cristobalite (STC) (60/40) composite was prepared by melting blend. Compared with that of the HDPE/STC composite, the interfacial interaction and the dispersion of the STC particles in the functionalized HDPE/STC composite were improved markedly. With increasing the irradiation time, the tensile strength and notched impact strength of the functionalized HDPE/STC composite increased, while its melt index decreased.     

Binary and ternary particulated composites: UHMWPE/CACO3/HDPE

A study of the influence of employing ultrahigh molecular weight polyethylene (UHMWPE) on the toughness of CaCO₃/high‐density polyethylene (HDPE) composites was carried out. Binary and ternary HDPE‐based composites with calcium carbonate in the range of 0–40% and UHMWPE in the range of 0–50% were produced by twin‐screw extrusion followed by compression molding. From tensile and impact tests, it was found that increasing calcium carbonate content increased tensile modulus, but decreased tensile strength, strain at break, and impact resistance. The addition of UHMWPE helped to increase the strain at break and impact resistance of composites moderately without decreasing modulus or strength. The degree of toughening was found to increase with increasing UHMWPE content, but to decrease as the filler volume fraction was increased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1503–1513, 2000     

Improvement of the mechanical properties of an HDPE/PS blend by compatibilization and incorporation of CaCO3

Generally, recycled polymer blends exhibit solid dispersion‐like morphology with poor mechanical properties. The aim of this work was to enhance the mechanical properties of a HDPE/PS (75/25) blend, in particular the stiffness and the impact strength. In order to improve the stiffness, CaCO₃ filler was incorporated. It was shown that PS and CaCO₃ were separately dispersed with poor adhesion to the HDPE matrix. The incorporation of CaCO₃ significantly enhanced the stiffness but lowers the impact resistance. Elastomer copolymers were incorporated in order to compensate for the embrittlement caused by the CaCO₃ filler. Depending on their chemical structure, either grafted with a reactive function or ungrafted, the elastomers acted differently at the interfaces of the HDPE/PS/CaCO₃ system. SEBS acts exclusively at the HDPE‐PS interface whereas SEBSgMA acts at both the HDPE‐PS and the HDPE‐CaCO₃ interface. The SEBSgMA elastomer lowered the stiffening effect caused by CaCO₃ and provided an insufficient increase in impact properties. One the other hand, SEBS, which concentrates its action at the HDPE‐PS interface, retained much of the stiffening effect of CaCO₃ and provided a greater improvement in impact properties than SEBSgMA. In the recycled HDPE/PS (75/25) blend, the incorporation of 20 vol% CaCO₃ and 4 vol% SEBS led to an increase in both impact strength (from 39 to 70 kJ/m²) and in stiffness (from 1335 to 1560 MPa). So, encouraging results were obtained, enabling us to predict a promising future for this approach to the recycling of commingled plastics.     

Atomic Force Microscopy, thermal, viscoelastic and mechanical properties of HDPE/CaCO3 nanocomposites

High Density Polyethylene (HDPE) and calcium carbonate (CaCO₃) nanocomposites were prepared from masterbatch by melt blending in twin screw extruder (TSE). The physical properties of HDPE/CaCO₃ nanocomposites samples (0, 10 and 20?wt% CaCO₃ masterbatch) were investigated. The morphology, thermal, rheological/viscoelastic and mechanical properties of the nanocomposites were characterized by Atomic Force microscopy (AFM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analyzer (DMA) as well as tensile test. The AFM images showed homogeneous dispersion and distribution of nano-CaCO₃ in the HDPE matrix. The DSC analysis showed a decrease in crystallinity of HDPE/CaCO₃ nanocomposites with the increase of CaCO₃ loading. This was due to the presence of nanofiller which could restrict the movement of the polymer chain segments and reduced the free volume/spaces available to be occupied by the macromolecules, thus, hindered the crystal growth. However, there was an increase in crystallization temperature about 1?C2?°C with the addition of CaCO₃. It was suggested that the CaCO₃ nanoparticles acted as nucleating agent. In melt rheology study, the complex viscosities of HDPE/CaCO₃ nanocomposites were higher than the HDPE matrix and increased with the increasing of CaCO₃ masterbatch loading. The DMA results showed that the storage modulus increased with the increasing of nano-CaCO₃ contents. The improvement was more than 40?%, as compared to that of neat HDPE. Additionally, the tensile test results showed that with the addition of CaCO₃ masterbatch, modulus elasticity of nanocomposites sample increased while yield stress decreased.     

Toughness of HDPE/CaCO3 microcomposites prepared from masterbatch by melt blend method

In this study, a series of high‐density polyethylene and micro/nanocalcium carbonate polymer composites (HDPE/CaCO₃ nanocomposites) were prepared via melt blend technique using a twin screw extruder. Nanocomposite samples were prepared via injection molding for further testing. The effect of % loading of CaCO₃ on mechanical and fracture toughness of these composites has been investigated in details. The effect of precrack length variation on the fracture toughness of the composite samples was evaluated, and the morphology of the fractured samples was also observed using scanning electron microscopy (SEM). It was found that increasing the % of CaCO₃ and precrack length decreased the fracture toughness. Fracture surface examination by SEM indicated that the diminished fracture properties in the composites were caused by the aglomerization of CaCO₃ particles which acted as stress concentrators. A finite element analysis using ANSYS was also carried out to understand the effect of agglomeration size, interaction between the particles and crack tip length on the fracture properties of these composites. Finally, a schematic presentation of the envisioned fracture processes was proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A study on HDPE/sulfonated EPDM‐treated CaCO3 blends

In this article, sulfonated ethylene‐propylene‐diene monomer terpolymer (H–SEPDM) was used to treat CaCO₃ particles. CaCO₃ particles are encapsulated by H–SEPDM through the reaction of sulfonic acid group (? SO₃H) in H–SEPDM with CaCO₃ to improve the interface adhesion of CaCO₃ with HDPE. In case the treated CaCO₃ is blended with HDPE, a brittle–ductile transition occurs. The impact strength of the blend rises sharply at 25–30 wt % CaCO₃, and amounts to more than 700 J/m, four times as high as that of HDPE at 30 wt % CaCO₃, without much loss of its yield strength and modulus. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2140–2144, 2001     

Polyethylene toughened by CaCO3 particle: Brittle-ductile transition of CaCO3-toughened HDPE

The dependencies of the notched Izod impact toughness of HDPE / CaCO₃ blends on CaCO₃ particle concentration and particle size are analyzed. It was found that the notched Izod impact strength (S) of HDPE / CaCO₃ blends depends discontinuously on CaCO₃ particle concentration. A brittle-ductile transition occurs when the CaCO₃ volume fraction (V_f) increases to a critical value (Vη_f). Furthermore, a brittle-ductile transition master curve can be constructed by taking the matrix ligament thickness (L) into account as a parameter instead of V_f. The results show that the critical matrix ligament thickness (L_c) is a single parameter for the transition and L_c = 5.2μm for HDPE / CaCO₃ blends. The impact strength, however, varies considerably with CaCO₃ particle size, which shows that CaCO₃ particle size is another dominating parametor for the toughness of HDPE / CaCO₃ blends. © 1993 John Wiley & Sons, Inc.     

Toughening and Reinforcement of HDPE/CaCO3 Blends by Interfacial Modification. I. Mechanical Properties and Morphology

To improve the mechanical properties and interfacial structure of HDPE/CaCO₃ composites, a kind of modifier, consisting mainly of carboxylated polyethylene (CPE), and a kind of CaCO₃ grafted with acrylamide (CaCO₃-A) are used. The carboxyl group content of CPE is from 1% to 10%. The amide group content on the surface of modified CaCO₃ is from 0.2% to 1.8%. The results indicate that the CPE improves compatibility partially, and the application of CaCO₃-A results in more ductile material with good impact and tensile strength. The higher the amide group content and carboxyl group content, the higher the tensile and impact strength. The improvement of interfacial adhesion by CPE and CaCO₃-A is clearly revealed by SEM and solvent extracting experiment.     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.     

Toughening and reinforcement of HDPE/CaCO3 blends by interfacial modification—interfacial interaction

To improve the mechanical properties and structure of HDPE/CaCO₃ composites, a type of modifier, consisting mainly of carboxylated polyethylene (CPE), and a type of CaCO₃ grafted with acrylamide (CaCO₃(SINGLE BOND)A) were used. The carboxyl group content of CPE was from 1 to 10%. The amide group content on the surface of the modified CaCO₃ was from 0.2 to 1.8%. The interfacial structure and interaction of ternary blends of HDPE, CPE, and CaCO₃(SINGLE BOND)A were studied. The results indicate that the higher the amide group content and the carboxyl group content, the higher the tensile and impact strength. This behavior has been attributed to a series of chemical and physico-chemical interactions taking place between the two components during the blending process which were confirmed by FTIR and extraction experiments. The improvement of interfacial adhesion by the CPE and CaCO₃(SINGLE BOND)A was also clearly revealed in the SEM of the fracture surface. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1275–1281, 1997     

Mechanical properties of teak wood flour‐reinforced HDPE composites

Mechanical properties such as tensile and impact strength behavior of teak wood flour (TWF)‐filled high‐density polyethylene (HDPE) composites were evaluated at 0–0.32 volume fraction (Φ_f) of TWF. Tensile modulus and strength initially increased up to Φ_f = 0.09, whereas a decrease is observed with further increase in the Φ_f. Elongation‐at‐break and Izod impact strength decreased significantly with increase in the Φ_f. The crystallinity of HDPE also decreased with increase in the TWF concentration. The initial increase in the tensile modulus and strength was attributed to the mechanical restraint, whereas decrease in the tensile properties at Φ_f > 0.09 was due to the predominant effect of decrease in the crystallinity of HDPE. The mechanical restraint decreased the elongation and Izod impact strength. In the presence of coupling agent, maleic anhydride‐grafted HDPE (HDPE‐g‐MAH), the tensile modulus and strength enhanced significantly because of enhanced interphase adhesion. However, the elongation and Izod impact strength decreased because of enhanced mechanical restraint on account of increased phase interactions. Scanning electron microscopy showed a degree of better dispersion of TWF particles because of enhanced phase adhesion in the presence of HDPE‐g‐MAH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

紫外辐照官能化HDPE的研究

本文通过红引光谱,与水的接触角以及力学性能测试等研究了空气中紫外辐照ＨＤＰＥ官能化及其增容作用。表明,紫外辐照能有效地在ＨＤＰＥ分子链上引入Ｃ≡Ｏ基团,随辐照时间增加,ｕＨＤＰＥ的Ｃ≡Ｏ基团含量南昌市,与水的接触角一上降,在一定条件下制得的ｕＨＤＰＥ对ＨＤＰＥ／ＰＣ共混体系有增容作用,其共涨物的拉伸强度、断裂伸长率和缺口冲击强度比未增容的都有提高。     

Rheology and Dispersion Behavior of Highly Filled Propylene-Ethylene Copolymer/Calcium Carbonate Composites

The rheology and dispersion behavior of commercial propylene-ethylene copolymer, highly filled propylene-ethylene copolymer/CaCO₃ composites and highly filled propylene-ethylene copolymer/HDPE/CaCO₃ composites prepared by melt-compounding were investigated. The pure propylene-ethylene copolymer exhibits pseudoplastic flow behavior obviously. The CaCO₃ particles in the composites have achieved a homogeneous dispersion and the increasing shear rate has almost no influence on the dispersion behavior of CaCO₃ particles. The high loading of CaCO₃ particles influences the rheology behavior of propylene-ethylene copolymer slightly. For the highly filled propylene-ethylene copolymer/CaCO₃ composites, the extensional viscosity only decreases slightly throughout the entire range of extension rates.     

Effects of High-Energy Electron Beam Irradiation on the Properties of Flame-Retardant HDPE/EVA/Mg(OH)2 Composites

The mechanical properties of flame-retardant high-density polyethylene/ethylene vinyl-acetate copolymer/magnesium hydroxide (HDPE/EVA/Mg(OH)₂) composites for cable materials are usually poor due to the high loading of the filler. In this study, high-energy electron beam irradiation was applied to HDPE/EVA/Mg(OH)₂ composites in the presence of triallylisocyanurate, an irradiation sensitizer. The effects of high-energy electron beam irradiation on the properties of irradiated HDPE/EVA/Mg(OH)₂ composites were investigated through the measurements of gel content, limiting oxygen index, tensile testing, thermogravimetric analysis, and scanning electron microscope. The results showed that the thermal, mechanical and flame-retardant properties of the HDPE/EVA/Mg(OH)₂ composites were improved by using high-energy electron beam irradiation.     

Influence of nanoclay on properties of HDPE/wood composites

Composites based on high density polyethylene (HDPE), pine flour, and organic clay were made by melt compounding and then injection molding. The influence of clay on crystallization behavior, mechanical properties, water absorption, and thermal stability of HDPE/pine composites was investigated. The HDPE/pine composites containing exfoliated clay were made by a two‐step melt compounding procedure with the aid of a maleated polyethylene (MAPE). The use of 2% clay decreased the crystallization temperature (T_c), crystallization rate, and the crystallinity level of the HDPE/pine composites, but did not change the crystalline thickness. When 2% MAPE was added, the crystallization rate increased, but the crystallinity level was further lowered. The flexural and tensile strength of HDPE/pine composites increased about 20 and 24%, respectively, with addition of 1% clay, but then decreased slightly as the clay content increased to 3%. The tensile modulus and tensile elongation were also increased with the addition of 1% clay. The impact strength was lowered about 7% by 1% clay, but did not decrease further as more clay was added. The MAPE improved the state of dispersion in the composites. Moisture content and thickness swelling of the HDPE/pine composites was reduced by the clay, but the clay did not improve the composite thermal stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007