Heat Shrinkability Research Articles

Effect of electron beam radiation on the mechanical, electrical, heat shrinkable and morphological properties of linear low-density polyethylene/polyolefin elastomer blends

The blending of polymers is an efficient means for developing new materials in a less hazardous and more economical way compared to the synthetic route. Polymers with different properties are blended to obtain a new material with combined properties. In this study, a thermoplastic elastomer blend is prepared by melt mixing a metallocene-based polyolefin elastomer (Engage 8003, abbreviated as EN) with linear low-density polyethylene (LLDPE, abbreviated as LL) using a twin-screw extruder in various compositions. To investigate the effect of the electron beam on the properties, LL, EN and their blends are irradiated in the 50–250 kGy dose range. The samples are subjected to gel fraction, mechanical, dynamic mechanical, hardness, heat shrinkability, volume resistivity and morphological studies. The % gel fraction, hardness and heat shrinkability of a sample increase with an increase in the irradiation dose. With increasing LL content, Young’s modulus and ultimate tensile strength of the blends are increased, maintaining the % elongation at break in an attractive region. LE64 (60 wt% LL and 40 wt% EN) and LE46 (40 wt% LL and 60 wt% EN) blends show optimized mechanical and dynamic mechanical properties. Irradiation further increases the tensile strength and Young’s modulus of LE64 up to 150 kGy and LE46 up to 200 kGy. The volume resistivity of the LE64 blend increases tenfold and quadruples for LE46 compared to non-irradiated blends when irradiated at 200 kGy. The morphological structures of the non-irradiated and crosslinked blends support the outcome of the obtained properties nicely.

Modified ethylene‐propylene‐diene elastomer (EPDM)‐contained silicone rubber/ethylene‐propylene‐diene elastomer (EPDM) blends: Effect of composition and electron beam crosslinking on mechanical, heat shrinkability, electrical, and morphological properties

ABSTRACTIn this investigation, a gamma radiation‐induced methacrylic acid (MAA)‐grafted ethylene‐propylene‐diene elastomer (EPDM) was used as a third component (g‐EPDM) in silicone rubber (SiR)/ethylene‐propylene‐diene elastomer (EPDM) blends. These blends were electron beam (EB) crosslinked. The effect of blend composition, the presence of g‐EPDM, and EB crosslinking on the mechanical, heat shrinkability, electrical, and morphological properties of SiR/EPDM blends have been studied. To investigate the effect of grafted EPDM (g‐EPDM), 10 wt % of g‐EPDM was added to immiscible SiR/EPDM blends. Both silicone and EPDM are blended in different proportions (70:30 and 30:70) with and without g‐EPDM followed by compression molding. To improve the properties and investigate the crosslinkability of binary and ternary blends further, the SiR/EPDM blends were irradiated by electron beam at different doses (50, 100, and 150 kGy). The gel content was found to increase with EPDM content, the presence of g‐EPDM, and radiation dose. The addition of g‐EPDM led to improvement of tensile properties (tensile strength, Young's modulus, percentage elongation, and toughness), electrical properties, and shrinkability of blends. EB crosslinking further enhanced the above properties. Surface morphology (SEM) revealed that the presence of g‐EPDM and the incorporation of EB crosslinking improved the above properties of blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47787.

Improved heat shrinkage and mechanical performances of polyethylene trilayer blown film prepared via novel multilayer coextrusion method

In this work, polyethylene (PE) trilayer blown film was prepared using a self‐made rotating coextrusion blown film die (RCBD) with the aim to manufacture trilayer film with excellent comprehensive heat shrinkage and mechanical performances. Polymer resins in this unique blown film die are subjected to a complicated flow field combining both shear circulation and pressure flow. As a result, the melt shows a helix movement in our novel die. The effect of additional parameter (mandrel rotation speed) on the heat shrinkability and mechanical properties of trilayer film was investigated and compared with that of various blow‐up ratios (BURs). The shrinkage rate and shrinkage force along transverse direction (TD) were significantly improved by the mandrel rotation, rather than BUR. Similar trends were observed in tensile strength along TD. However, no considerable changes in heat shrinkability and mechanical properties of PE films along machine direction (MD) were observed. In summary, samples prepared at mandrel rotation speed of 4 rpm were obtained excellent comprehensive performances. Moreover, the morphological investigations confirmed that the formation of high ordered lamellae could be induced by mandrel rotation, and the row structure of oriented lamellae tended to incline to TD under higher rotation speed of mandrel. Besides, the crystal dimension and percent crystallinity were increased because of the mandrel rotation.

Effect of different curing systems on heat shrinkability and mechanical properties of ethylene vinyl acetate/epoxidized natural rubber blends

AbstractEthylene vinyl acetate (EVA)/epoxidized natural rubber (ENR) blends containing 10 and 30 wt % ENR were prepared by using an internal mixer. Five different types of curing systems were employed: dicumyl peroxide (DCP), sulfur (S), phenolic resin (Ph), DCP + S, and DCP + Ph. DCP could crosslink with both EVA and ENR while S and Ph were curing agents for ENR. The DCP system provided the lowest tensile properties and tear strength because of low crosslinking in ENR phase. Addition of sulfur or phenolic resin increased the mechanical properties due to a better vulcanization of the rubber phase. The mechanical properties of the blends decreased with increasing ENR content. The rubber particle size in the blends containing 30% ENR played a more important role in the mechanical properties than the blends containing 10% ENR. ENR particle size did not affect heat shrinkability of EVA and a well vulcanized rubber phase was not required for high heat shrinkage. Furthermore, heat shrinkage of the blends slightly changed as the ENR content increased for all curing systems. With regard to the mechanical properties and heat shrinkability, the most appropriate curing system was DCP + Ph and in the case the 10 wt % ENR content produced a more favorable blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of rubber content on mechanical properties and heat shrinkage of ethylene vinyl acetate copolymer blended with epoxidized natural rubber

AbstractEthylene vinyl acetate (EVA, 18 mol % vinyl acetate) and epoxidized natural rubber (ENR, 50 mol % epoxidation) were blended in an internal mixer and compared to EVA. Dicumyl peroxide (DCP) was used as a curing agent. The blends consisted of 10–50 wt % of ENR and were compared with crosslinked EVA in terms of heat shrinkage, mechanical properties, and degree of crystallinity. It is found that the blends showed a decrease in mechanical properties with increasing ENR content because DCP was not a good vulcanizing agent of ENR. The addition of ENR did not affect heat shrinkability of EVA. The maximum heat shrinkage obtained was 80% for EVA and the blends. ENR did not affect thermal properties of EVA investigated by the differential scanning calorimetry. The X‐ray diffractometry showed discrepancy in degree of crystallinity before and after specimen stretching and after heat shrinking. It is believed that ENR particles decreased molecular orientation of EVA resulting in a decrease in degree of crystallinity but the remained orientation was sufficient for heat shrinking. The blend showed better extrudability than EVA after increasing take‐up speed. Therefore, the extruded tube prepared from the blend provided higher heat shrinkage than EVA tube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Mechanical properties and heat shrinkability of electron beam crosslinked polyethylene–octene copolymer

The mechanical properties and heat shrinkability of electron beam crosslinked polyethylene–octene copolymer were studied. It was found that gel content increases with increased radiation dose. The analysis of results by the Charlesby–Pinner equation revealed that crosslinking was dominant over chain scission upon irradiation. Formation of a crosslinked structure in the electron beam irradiated sample was confirmed by the presence of a plateau of dynamic storage modulus above the melting point of the polymer. Wide-angle X-ray diffraction revealed that there was little change in crystallinity for the irradiated samples, indicating that radiation crosslinking occurs in the amorphous region of the polymer. The tensile modulus increases, whereas the elongation at break decreases with increased radiation dose. The heat shrinkability of the material increased with an increased radiation dose because the radiation-induced crosslinks serve as memory points during the shrinking process.

Heat Shrinkable Behaviour of Supramolecular Hydrogen Bonded Maleated Ethylene Propylene Diene Rubber and Maleated High Density Polyethylene Blend

Maleated high density polyethylene and maleated ethylene propylene diene rubber (50 wt%/50 wt%) was blended in presense of 3-amino-1,2,4-triazole (ATA). The supramolecular hydrogen bonding was characterized by FTIR and dynamic mechanical analysis. The crystallinity of the blend system was studied by XRD and it was observed that supramolecular hydrogen bonding decreases the crystallinity of the blend. The supramolecular hydrogen bonded network improves heat shrinkability of the blend.

Green thermoplastic elastomer based on polycaprolactone/epoxidized natural rubber blend as a heat shrinkable material

Green thermoplastic elastomer based on polycaprolactone and epoxidized natural rubber blend was prepared by melt mixing process. Effect of crosslinking by dicumyl peroxide and rubber content on heat shrinkable behavior of the blends was studied. It was found that the crosslinking enhances the heat shrinkability of the blend, and in the case of uncrosslinked blends, the blend containing higher amount of rubber showed greater heat shrinkability.

Heat Shrinkable Behavior and Mechanical Response of a Low‐Density Polyethylene/Millable Polyurethane/Organoclay Ternary Nanocomposite

AbstractSummary: A low‐density polyethylene (LDPE)/millable polyurethane (PU)/organoclay ternary nanocomposite was successfully prepared. The nanocomposites were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites, as evidenced by XRD, are intercalated. The heat shrinkable behavior of the nanocomposites, as well as their pristine counterparts, was studied. It was observed that heat shrinkability decreases with increased filler content. The tensile strength and the tensile modulus of the nanocomposites are higher than their pristine counterparts.The heat shrinkability of the unfilled LDPE/millable PU blend is highest and it decreases with increased nanofiller content.imageThe heat shrinkability of the unfilled LDPE/millable PU blend is highest and it decreases with increased nanofiller content.

Study of heat shrinkability of crosslinked low‐density polyethylene/poly(ethylene vinyl acetate) blends

AbstractIn this study, the heat‐shrinkage property in polymer was induced by first compounding low‐density polyethylene/poly(ethylene vinyl acetate) (LDPE/EVA) blends with various amounts of peroxide in a twin‐screw extruder at about 130°C. The resulting granules were molded to shape and chemically crosslinked by compression molding. A process of heating–stretching–cooling was then performed on the samples while on a tensile machine. Shrinkability and effective parameters were also investigated using thermal mechanical analysis. The results showed that the gel fraction was higher for the sample of higher EVA content with the same amount of dicumyl peroxide (DCP). A decrease in the melting point and heat of fusion (ΔHf), as determined from DSC, was observed with an increase in the DCP content. Studies on the heat shrinkability of the samples showed that samples stretched above the melting point had a higher shrinkage temperature than those stretched around the crystal transition temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. These could be attributed to the formation of new spherulites as well as changes in the amount and the size of crystals. Furthermore, in samples elongated at 120°C (above the melting point), the rate of stretching had no effect on the shrinkage temperature. The results showed that the extent of strain had no effect on the temperature of shrinkage, but rather on the ultimate shrinkage value. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1389–1395, 2004

Studies in interchain crosslinking and heat shrinkability of polymer blends consisting of grafted low‐density polyethylene and ethylene‐acrylic rubber

AbstractBlends prepared by the melt mixing of thermoplastic and elastomer have gained considerable attention in recent years. Heat shrinkability, which is dependent on elastic memory, can be introduced into the system in the form of an elastomeric phase. The present study deals with the measurement of heat shrinkability of the blends of grafted polyethylene and an ethylene acrylic elastomer. Interchain crosslinking between grafted polyethylene and elastomer improves the shrinkability. High temperature performance of the samples depends on interchain crosslinking. From torque rheometry it was observed that the maximum amount of interchain crosslinking was obtained in the sample containing acrylamide grafted LDPE. The probable interaction between the rubber and the plastic phase is confirmed by IR spectroscopy.

Study of Poly (Ethylene Vinyl Acetate)- Carboxylated Nitrile Rubber (XNBR) Blends with Reference to their Shrinkability

Heat shrinkability, a collective property, of the polymer is being utilised in various applications - mainly in the field of encapsulation. The elastic memory is introduced into the system in the form of an elastomeric phase. Here, the blends of ethylene vinyl acetate (EVA) and carboxylated nitrile rubber (XNBR) were studied with reference to their shrinkability. It was found that with increasing cure time shrinkability was decreased. On the other hand, with increasing elastomer content, the shrinkage was increased up to a certain level and beyond this shrinkability was decreased. Temperature has a profound effect on the shrinkability. High temperature (H-T) stretched samples showed higher shrinkage than room temperature (R-T) stretched one. Generally, the crystallinity of high temperature (H-T) stretched sample was higher than that of room temperature (R-T) stretched sample, which was again higher than that of original unstretched sample, for a particular blend. At room temperature (R-T), stretching nucleation is favoured but at high temperature (R-T) stretching crystal growth is favoured. From SEM, it was seen that elastomer phase in H-T stretched sample was more elongated than that in R-T stretched one and in shrunk sample elastomer phase was more spherulitic than that of the original unstretched one.

Heat Shrinkable Polymer Blends Based on Grafted Low-Density Polyethylene and Carboxylated Nitrile Rubber

Heat shrinkability of a polymer, which depends on the elastic memory, was introduced into the system in the form of an elastomeric phase. The present study deals with the measurement of heat shrinkability of the blend of grafted low-density polyethylene and carboxylated nitrile rubber. The grafting materials used in this study were acrylamide, vinyl triacetoxy silane, and maleic anhydride. Coupling agents used were 4,4′-diamino diphenyl methane and 4,4′-diamino diphenyl sulphone. It was found from torque rheometry and swelling studies that the degree of interchain crosslinking was greatest when 4,4′-diamino diphenyl methane was used as a coupling agent in the maleic anhydride grafted low-density polyethylene, while it was lowest when 4,4′-diamino diphenyl sulphone was used as a coupling agent. Shrinkability of the high temperature stretched sample was more than that of room temperature stretched sample. It was found from XRD that the crystallinity of the stretched sample was more than that of original sample. It was observed from the high temperature DSC that the interchain crosslinking was responsible for the enhancement of the thermal stability of the sample. Interchain crosslinking between grafted polyethylene and elastomer improves the shrinkability. Probable interactions between the rubber and plastic phase were confirmed by IR spectroscopy.

Effect of the coupling agent's reactivity on the shrinkability of the blends consisting of grafted low‐density polyethylene and ethylene acrylic elastomer

AbstractBlends prepared by melt mixing of thermoplastic elastomer have gained considerable attention in recent years from a heat shrinkability point of view. Our present study deals with the measurement of heat shrinkability of the maleic anhydride grafted low‐density polyethylene and ethylene acrylic elastomer. Two samples have been prepared to study the effect of coupling agent's reactivity on the shrinkability of the blends. The coupling agents used are 4,4′‐diamino diphenyl sulphone, and 4,4′‐diamino diphenyl methane. Shrinkability was measured at room temperature, 120 °C, 150 °C, and 180 °C. Shrinkability is found to be greater in high temperature stretched sample rather than that of room temperature stretched sample. It is observed that reactivity as well as heat shrinkability is more when 4,4′‐diamino diphenyl methane is used as a coupling agent. The mechanism of interchain crosslinking reaction has been confirmed by IR spectroscopy. Differential scanning calorimetry was performed to study the thermal stability of the sample. Copyright © 2002 John Wiley & Sons, Ltd.

On the Heat Shrinkability and Interchain Crosslinking of Blends Consisting of Grafted Ethylene-Propylene Polymer and Polyurethane Elastomer

Blends prepared by melt mixing of thermoplastic materials/elastomers have gained considerable attention in recent years from the viewpoint of heat shrinkability. The present study deals with the measurement of heat shrinkability of the blends of grafted ethylene-propylene polymer and polyurethane elastomer. The used grafting materials are acrylic acid, vinyltriacetoxysilane, and glycidyl acrylate. Interchain crosslinking between grafted ethylene-propylene polymer and polyur-ethane elastomer improves the heat shrinkability. The high temperature performance of the sample is dependent on interchain crosslinking. From torque rheometry it was observed that the maximum amount of interchain crosslinking occured in the sample containing glycidyl acylate as grafting material. The probable interaction between rubber and plastic phase was confirmed by IR spectroscopy.

Development of heat shrinkable and flame‐retardant EVA/CSM blends

AbstractA plastic (EVA) was blended with elastomer (CSM) with and without curatives. The elastomer phase (amorphous) contributed markedly to the shrinkability and most important is, took up a major amount of additive flame‐retarding agent thus not affecting much the heat shrinkability of the plastic i.e. as a whole the blend. When the elastomer phase was crosslinked the flame‐retardancy, due to a reduction of combustible volatile product, was increased. Additive flame‐retardants hamper the heat‐shrinkability of the blend to some extent depending on various factors such as blend composition, temperature, curing etc. The depression of shrinkability in the presence of flame‐retarding agent was less for the cured sample and elastomer‐rich blend compared with the uncured and plastic‐rich blend, respectively. It was found that with an increase in the cure time and elastomer content the shrinkability as well as flame‐retardancy was increased. At high temperature the sacrifice of the shrinkability in the presence of flame‐retardants increased, for a particular blend. The shrinkability and flame‐retardancy of a cured sample was higher than that of an uncured sample. The highest flame‐retardancy was obtained in the presence of Sb2O3/Chlorohor. Copyright © 2002 John Wiley & Sons, Ltd.

On the Heat Shrinkability and Interchain Crosslinking of Blends Consisting of Grafted Ethylene-Propylene Polymer and Polyurethane Elastomer

On the Heat Shrinkability and Interchain Crosslinking of Blends Consisting of Grafted Ethylene-Propylene Polymer and Polyurethane Elastomer

Effect of the coupling agent's reactivity on the shrinkability of the blends consisting of grafted poly (ethylene vinyl acetate) and polyurethane elastomer

Blend prepared by the melt mixing of thermoplastic elastomer has gained considerable attention in recent years from heat shrinkability point of view. Present study deals with the measurement of the heat shrinkability of the maleic anhydride grafted poly (ethylene vinyl acetate) and polyurethane elastomer blend. Two samples have been prepared to study the effect of the coupling agent's reactivity on the shrinkability of the blend. The used coupling agents are 4,4′ diamino diphenyl sulphone (DDS) and 4,4′ diamino diphenyl methane (MDA). It is revealed that heat shrinkability increases as the reactivity of the coupling agent increases. The reactivity as well as the shrinkability is more when the used coupling agent is 4,4′ diamino diphenyl methane. The mechanism of interchain crosslinking reaction is confirmed by IR spectroscopy.

Study of Heat Shrinkability and Flame Retardancy of Poly(ethylene vinyl acetate)/Epichlorohydrin Blends

Greater cure time (crosslinking) and greater elastomer content increases the shrinkability as well as flame retardancy of the blends. Additive flame retardants hamper the heat shrinkability of the blend to some extent depending on various factors. The depression of shrinkability due to interference of flame retarding agent is less for cured sample and elastomer-rich blend compared to uncured and plastic-rich blend, respectively. At high temperature the shrinkability is higher, but the sacrifice of shrinkability in the presence of flame retardants increases with increase in temperature, for a particular blend. The highest flame retardancy is obtained in presence of Sb2O3/Chlorohor and TPP/Zn metaborate.

Heat Shrinkable Polymer Blends Based on Grafted Low Density Polyethylene and Polyurethane Elastomer—Part II

Heat shrinkability of a polymer, which depends on the elastic memory, can be introduced into the system in the form of an elastomeric phase. The present study deals with the measurement of heat shrinkability of a blend of grafted polyethylene and polyurethane elastomer. The grafting materials used are vinyl triacetoxy silane and maleic anhydride. The coupling agents used are ethane diol and 4,4′-diamino diphenyl sulphone. From Torque Rheometry it is found that the maximum amount of interchain crosslinking is obtained in the sample containing silane grafted LDPE. Shrinkability was measured at room temperature, 120°C, 150°C, and 180°C. Shrinkability is greater in the high temperature stretched sample than in the room temperature stretched sample. Shrinkability depends on various factors such as orientation of the stretched sample, unrecoverable viscous flow, which occurs during stretching, and degree of interchain crosslinking. Interchain crosslinking between grafted polyethylene and elastomer improves the shrinkability. Probable interactions between the rubber and plastic phase are confirmed by IR spectroscopy. Extraction of the elastomeric phase is restricted due to interchain crosslinking as confirmed by scanning electron microscopy.