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).     

Studies on fast functionalization of HDPE by ultraviolet irradiation and functionalized HDPE/CaCO3 composites

High density polyethylene (HDPE) was functionalized quickly by ultraviolet irradiated in ozone atmosphere. The oxygen-containing groups in the functionalized HDPE were C=O and C–O, and their content increased with increasing the irradiation time. The molecular weight of the functionalized HDPE decreased and its distribution became wider with increasing the irradiation time. The gel was not found in the functionalized HDPE. Compared with those of HDPE, the melting temperature and crystallinity of the functionalized HDPE decreased. With increasing the irradiation time, the hydrophilicity of the functionalized HDPE was enhanced, while its temperature of thermal decomposition decreased. The functionalized HDPE/CaCO₃ composites were prepared. Compared with those of HDPE/CaCO₃ composites, the compatibility and dispersion of the functionalized HDPE/CaCO₃ composites were enhanced observably. The tensile strength and notch impact strength of the functionalized HDPE/CaCO₃ composites increased with increasing the irradiation time.     

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     

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     

Polyethylene toughened by rigid inorganic particles

High density polyethylene (HDPE) is toughened by particles of rigid inorganic filler CaCO₃, which is treated with phosphate. The stress-strain curve of the HDPE/modified-CaCO₃ (80/20) composite covers a greater area than that of HDPE, and the impact strength of HDPE is greatly improved by modified CaCO₃ from 230 J/m to 580 J/m as CaCO₃ content is increased to 50 wt%. Morphological observation indicates a finer dispersion of the modified-CaCO₃ particles and a large plastic deformation of HDPE. The cavitation and stress field interaction around the particles are considered to explain the toughening mechanism.     

Structure development and property changes in high‐density polyethylene/calcium carbonate blends during pan‐milling

A new self‐designed mechanochemical reactor, inlaid pan‐mill, was used in studying high density polyethylene (HDPE) and calcium carbonate (CaCO₃) blends. The effects of CaCO₃ on the crushing and structure of HDPE matrix and the properties of HDPE/CaCO₃ blends were investigated. Scanning electron microscopy, Fourier transformed IR spectroscopy, dynamical mechanical testing analysis, capillary rheometer, and Instron material testing system were used to characterize the structure of HDPE and evaluate the properties of HDPE/CaCO₃ blends. The introduction of calcium carbonate during milling improved milling efficiency, and time needed for each cycle was greatly reduced. Oxygen‐containing groups on HDPE chains, which were produced during milling, increased interfacial interactions and improved the dispersion and distribution of calcium carbonate particles in HDPE/CaCO₃ blends. Rheological, thermal, and mechanical properties were also improved. The elongation at break of milled blends with high concentrations of calcium carbonate was significantly higher than that of unmilled blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1459–1464, 1999     

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.     

Nonisothermal crystallization of high density polyethylene and nanoscale calcium carbonate composites

Nonisothermal crystallization of high density polyethylene (HDPE)/maleic anhydride‐modified HDPE(manPE)/nanoscale calcium carbonate (CaCO₃) nanocomposite was investigated by means of wide angle X‐ray diffraction (WAXD), polarized optical microscopy (POM), and differential scanning calorimetry (DSC). WAXD indicated that the crystallinity was reduced with the addition of CaCO₃. The spherulite size of HDPE increased in the presence of manPE, but decreased when CaCO₃ was added from observation of POM. A modified Avrami analysis, Ozawa analysis, and Liu analysis were applied to the nonisothermal crystallization process. Crystallizability followed the order: HDPE/manPE/CaCO₃ > HDPE/CaCO₃ > HDPE/manPE > HDPE when undercooling was taken into account. Dependence of the effective activation energy on the relative crystallinity was estimated by the Friedman equation, and the results were used to calculate the parameters (K_g and U*) of Lauritzen‐Hoffman's equation by Vyazovkin's method. These results indicate that the addition of maleic anhydride groups and CaCO₃ tend to promote the nucleation of spherulites on their surfaces and lead to epitaxial growth of the crystallites. But at the same time, manPE and CaCO₃ particles may hinder the transport of the molecule chains resulting in a decrease of the crystallization growth rate. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

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.     

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.     

Effect of high‐energy vibro‐milling of filler on the mechanical properties of filled high‐density polyethylene

The effect of high‐energy mechanical milling of CaCO₃ (calcium carbonate) and STC (a mixture of sericite, tridymite and cristobalite) on mechanical properties, rheological and dynamical mechanical behavior of high‐density polyethylene (HDPE)/CaCO₃ and HDPE/STC was studied through SEM (scanning electron microscope), DMTA (dynastic mechanical test analysis), mechanical and melt rheological properties tests. The experimental results show that addition of fillers treated by coupling agent and vibromilling to HDPE makes the impact strength of HDPE greatly increased. The impact strength of HDPE/treated CaCO₃ (60/40) and HDPE/treated STC (60/40) is ca. 4 and 3 times respectively as high as that of HDPE. The SEM micrographs of impact fractured surfaces of treated fillers filled HDPE show extensive plastic deformation of HDPE matrix, indicating that the plastic deformation of matrix induced by the treated fillers is the main contribution for absorbing a great amount of impact energy. This is the reason why the impact strength of HDPE greatly increases with addition of coupling agent and vibromilling treated fillers. The intensity of γ relaxation peak of HDPE in HDPE/treated CaCO₃ on tanδ vs. temperature curve increases and the peak shifts to higher temperature due to its stronger interface interaction as compared with that of HDPE/untreated CaCO₃.     

Investigation on β‐polypropylene/PP‐g‐MAH/ surface‐treated calcium carbonate composites

β‐Polypropylene composites containing calcium carbonate treated by titanate coupling agent (T‐CaCO₃) and maleic anhydride grafted PP (PP‐g‐MAH) were prepared by melt compounding. The crystallization, morphology and mechanical properties of the composites were investigated by means of differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy, scanning electron microscopy and mechanical tests. It is found that both T‐CaCO₃ and NT‐C are able to induce the formation of β‐phase, and NT‐C greatly increases the β content and decreases the spherulitic size of PP. PP‐g‐MAH facilitates the formation of β‐form PP and improves the compatibility between T‐CaCO₃ and PP. Izod notched impact strength of β‐PP/T‐CaCO₃ composite is higher than that of PP/T‐CaCO₃ composite, indicating the synergistic toughening effect of T‐CaCO₃ and β‐PP. Incorporation of PP‐g‐MAH into β‐PP/T‐CaCO₃ composite further increases the content of β‐crystal PP and improves the impact strength and tensile strength when T‐CaCO₃ concentration is below 5 wt%. The nonisothermal crystallization kinetics of β‐PP composites is well described by Jeziorny's and Mo's methods. It is found that NT‐C and T‐CaCO₃ accelerate the crystallization rate of PP but the influence of PP‐g‐MAH on crystallization rate of β‐PP composite is marginal. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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.     

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     

Ultraviolet light aging properties of PVC/CaCO3 composites

The ultraviolet radiation aging behaviors of PVC/CaCO₃ and PVC/CaCO₃/macromolecular modifier composites were studied through whiteness measurement, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, and mechanical properties test. It was found that nano‐CaCO₃ particles used as ultraviolet light screening agents could significantly enhance the antiaging properties of PVC materials. Due to the macromolecular modifier coated on nano‐CaCO₃ particles, the compatibility of nano‐CaCO₃ and PVC matrix was improved, resulting in uniform dispersion of nano‐CaCO₃ in PVC matrix. Therefore, the PVC/CaCO₃/MP composite exhibited better antiaging properties than PVC/CaCO₃ composite. After 12 h of ultraviolet irradiation, the tensile strength retention, elongation at break retention, and impact strength retention of PVC/CaCO₃/MP composite were 79.5%, 74.5%, and 75.3%, which were much higher than that of neat PVC and PVC/CaCO₃ composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of ultraviolet‐irradiated high density polyethylene at different environmental temperatures

C? O, C?O, and C(?O)O oxygen‐containing groups were introduced onto the molecular chain of high‐density polyethylene (HDPE) through ultraviolet irradiation in air. The introduction rate of the oxygen‐containing groups onto HDPE increased with increasing environmental temperature. After ultraviolet irradiation, the molecular weight of HDPE decreased, and its distribution became wider; the melting temperature, contact angle with water, and impact strength decreased; the degree of crystallinity and yield strength increased; and their variation amplitude increased with environmental temperature. The environmental temperature had an effect on the gel content of irradiated HDPE. HDPE‐irradiated for 48 h at 35° and 50°C were not crosslinked. However, gelation took place in HDPE irradiated for 24 h at 70°C. HDPE irradiated at a high environmental temperature was more effective than that irradiated at a low environmental temperature in compatibilizing HDPE with PVA. Compared with the 83/17 HDPE/PVA blend, the yield and notched impact strength of the 73/17 HDPE/PVA blend compatibilized with 10% HDPE irradiated for 24 h at an environmental temperature of 70°C increased from 30.8 MPa and 110 J/m to 34.9 MPa and 142 J/m, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2966–2969, 2003     

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.     

Influence of the incorporation of fine calcium carbonate particles on the impact strength of polypropylene/polystyrene‐block‐poly(ethylene butene)‐block‐polystyrene blends

The Izod impact strength of two kinds of ternary composites was investigated. One consisted of polypropylene (PP), the triblock copolymer polystyrene‐block‐poly(ethylene butene)‐block‐polystyrene (SEBS), and calcium carbonate (CaCO₃) particles, and the other consisted of PP, carboxylated SEBS (C‐SEBS), and CaCO₃ particles. The mean size of the CaCO₃ particles was about 160 nm. According to scanning electron microscopy observations, the composite with SEBS showed a morphology in which SEBS domains and CaCO₃ particles were independently dispersed in the PP matrix. On the other hand, the composite with C‐SEBS showed a morphology in which CaCO₃ particles were encapsulated by C‐SEBS; that is, a core–shell structure was formed. The Izod impact strength of the composite with SEBS was higher than that of the composite with C‐SEBS and the PP/SEBS and PP/C‐SEBS binary blends. According to observations of the fractured surface, the stress‐whitened area was larger in the composite with SEBS than in the composite with C‐SEBS and the PP/SEBS and PP/C‐SEBS binary blends. The toughening mechanism of the composite, using nanometer‐sized CaCO₃ particles in combination with SEBS, was examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009