j. nucl. tech. appl. sci, vol. 4, no. 2, pp. 83 : 90 (2016) vol 4 no 2.pdf · center for material...

The use of Ionizing Irradiation to Prepare Polyethylene Wax and Agrowaste Composite ( 83 )

ABSTRACT

KEYWORDS

The use of Ionizing Irradiation to Prepare Polyethylene Wax and Agrowaste Composite

Elhady, M.A.1; Christopher Mark Liauw2; Shabaan K. M.3 and Elnahas, H.H.1

Received: 26/06/2016

Accepted: 14/07/2016

E.mail:[email protected]

Low Density Polyethylene Wax; Agrowaste; Irradiation.

J. Nucl. Tech. Appl. Sci, Vol. 4, No. 2, PP. 83 : 90 (2016)

Journal of

NUCLEARTechnology in Applied ScienceISSN 2314-8209 e-ISSN 2314-8217

1. National center for radiation research and technology, Polymer Dept. ,Atomic Energy Authority, P.O.Box 29, Nasr City, Cairo, Egypt; 2. Center for Material Science Research, Faculty of science and Engineering Manshester Metropolitan University, Chester Street, MI 5

GD, UK. 3. School of Science &the Environment Chemistry and Environmental Division, Manchester, Oxford Road, MI 5GD, UK.

Low density polyethylene wax (LDPE wax) and agrowaste compos-ites were prepared through melt processing in a wide range of composi-tions at 110oC and 80 rpm for 5 min. Agrowaste content was added be-tween 35 and 65 % by weight. Mechanical strength, water absorption and morphological properties were studied. The results asserted that increas-ing of LDPE wax content in the prepared composites tended to increase the wet ability of agrowaste fiber increasing in sequences the interfacial adhesion. Where, the smaller molecular weight polymer of LDPE wax decreases viscosity at 110oC and improves process ability considerably, thus optimization of composition is essential to achieve maximum per-formance. Concentrations of 1.2 wt.% of titanium dioxide (TiO2) was recommended for the optimization of increasing the melting temperature (Tm) and surface hardening properties of the composites, respectively. Also, ionizing irradiation of the prepared composites has possessed an obvious increase of Tm and mechanical properties. The application of the prepared composites in plastic-wood production was suggested.

Elhady, M.A. et al.( 84 ) J. Nucl. Tech. Appl. Sci., Vol. 4, No. 2

INTRODUCTION

Polymer wood composite (PWC) prod-ucts manufactured from blends of ther-moplastics and agrowaste have been the subject of many studies. The ap-plications of the PWC products include

decking, window and door profiles, panel inserts, and flower pots. It is known that the mechanical and physical properties of PWC products are affected by a number of factors, such as the volume fraction and aspect ratio of fiber, fiber orientation, dispersion temperature (Matuana et al., 1998; Clemons et al., 2000; Colom et al., 2003; Sombatsompop et al., 2003 and Sombatsompop et al., 2005). The most important role on the mechanical properties of the composites is the fiber matrix adhesion. The incom-patibility between polar cellulose fibers and hydro-phobic polymers results in inferior mechanical prop-erties due to poor interfacial bonds. Current concepts of the methods applied to improve the fiber matrix interfacial adhesion include molecular chain entan-glements, good mechanical contact, the matching of surface tensions, and the formation of chemical and physical bonds through the use of chemical coupling agents (Bledzki et al., 1999; Mohanty et al., 2001 and Moon et al., 2005).

In this article, a recyclable polymer and agrowaste composites as Low density polyethylene wax produced from LDPE polymer and agrowaste fiber from bagasse were prepared by using coupling agent and ionizing irradiation in order to seek the op-timum interfacial strength, melting temperature and water resistance by considering the mechanical and morphological properties of the composites

Experimental

Preparation of low density polyethylene wax

Two main steps were used to obtain LDPE wax. Firstly,through the irradiation process: the LDPE

samples are irradiated by γ-rays at dose of 50kGy (the doserateis 2.08kGy/h) under water (in absence of air) (El-Nahas et al., 2014).Secondly, thermolysis process: the irradiated LDPE samples were heated to 350oC as a thermolysis process to obtain a low molecular weight of LDPE wax. The LDPE wax with melting point (Tm) 110 ◦C was obtained. The following diagram shows the preparation of LDPE wax from LDPE through radiation-thermolysis pro-cesses.

Schematic diagram shows the preparation of wax from LDPE through radiation-thermolysis pro-cesses

Agrowaste fiber

Agrowaste fiber particles were obtained from bagasse after multiple squeezing of sugar cane. The average size of agrowaste particles used in this work was in the range 150-1000μm. At the initial stage of this work, the contents of agrowaste particles added into the LDEP wax were varied from 35% to 65% by weight and then 50% was chosen as optimum ra-tio for our suggested application.


Coupling agents

Coupling agent as (TiO2) was supplied by Gran-dy Co., for chemical industries, Egypt.

Blending of LDPE wax and agrowaste fibers

The blending process commenced by oven-dry-ing agrowaste, at 80oC for 24h. After that, the LDPE wax (pellets or flaks) were brought to dry. Blend with agrowaste particles by a high speed mixer for 5min before being melt blended in a twin-screw extruder (Haake pollab- Rheomex CTW 100p, Germany).

The blending temperature profiles on the ex-truder were 110, 120 and 130oC from hopper to die zones or to hot pressing. The screw rotating speed was 80 rpm.

Composite characterization

Flexural strength

The flexural property was determined according to ASTM D790 (1990) (specimen dimensions of 6.4 X 120 mm2. Support span of 92 mm. and a cross-head speed of 2.8 mm min).

Surface hardness

Hardness was controlled by ASTM D2240 spec-ification, model 306 L type A, D durometer for soft and hard plastic.

Water absorption

The clean and dried samples of known weight were immersed in distilled water for 24 h. at 25oC. The samples were removed, blotted by absorbent paper and quickly weighted. The water absorption percent was calculated as follows:

Water absorption % = (W2 – W1)/W1X100

Where, W1 and W2 represent of dry and wet samples, respectively.

Melting temperature

Differential scanning calorimetry (DSC) A Shi-madzu Type DSC-50 DSC system in nitrogen atmo-sphere at 20 mL/min was used in this study in the temperature range from ambient to 250°C at a heat-ing rate of 10°C/min.

Morphological investigations

The surface morphology of different samples was studied by SEM. The SEM micrographs were taken with a JSM-5400 instrument by JEOL-Japan.

Gamma Irradiation

Radiation was carried out using acobalt-60 source of gamma radiation (in NCRRT) manufac-tured by the Atomic Energy Authority of India at dose rate of 2.5kGy/ h

RESULTS AND DISCUSSION

Factors affecting the properties of LDPE wax and agrowaste fiber composites:

Effect of LDPE wax:

It is difficult for the low density polyethylene (LDPE) molecules to fill the small cavities on the surface of agrowaste to form mechanical interlocks due to the high viscosity of the LDPE. Increasing the processing temperature may theoretically improve the ability of LDPE molecules to flow into those cav-ities; however, high temperatures (exceeding 190oC) may lead to early decomposition and carbonization of agro-fibers (Moon et al., 2005) thus lowering the mechanical properties of plastic-wood composite. As the result of that, the use of LDPE wax has re-alized a high flow at low temperature as shown in table 1.

Table 1 shows the properties containing different LDPE wax amounts. Generally, it was found that in-creasing the LDPE wax content resulted in increases in hardness, flexural and water resistance.


Effect of coupling agent:

The most important role on the mechanical prop-erties of the composites is the fiber matrix adhesion. The incompatibility between polar cellulose fibers of agrowaste and hydrophobic polymers results in in-ferior mechanical properties due to poor interfacial bonds. Current concepts of the methods applied to improve the fiber matrix interfacial adhesion include molecular chain entanglements, good mechanical contact, the matching of surface tensions and the for-mation of chemical coupling agents (Bledzki et al., 1999; Mohanry et al., 2001 and Moon et al., 2005).

Table (1) Typical formulation and related properties of LDPE wax / bagasse composites containing different LDPE wax contents.

LDPE waxContents %

Surface hardnessShore D Flexural strength MPa Water absorption %

35 58 13 540 59 14 445 60 15 350 63 17 160 66 18 0.465 68 19 0.2

Processing temperature = 110-120oC Time of processing = 5 minApplied pressure = 50 Kgm/cm2

Fig. (1): Effect of coipling agent (TiO2) on melting tem-perature of LDPE wax and bagaase composite (50/50).

Fig. (2): Effect of coupling agent on surface hardness of LDPE and bagasse (at 50/50).

Fig. (3): Effect of coupling agent on flexural strength of LDPE wax and bagasse composite (at 50/50).


In figures 1, 2 and 3 concentration of 0.7 wt% of TiO2 was recommended for the optimization of the mechanical properties of the composites. Up to the recommended dosages, TiO2 was more effective in turns of the improved for increasing thermal melt-ing, hardness and flexural strength. This improve-ment of the composites was reduced by the increased amounts of agrowaste particles.

Effect of ionizing irradiation

In the general majority of cases, pre-irradiations of solid polymers are a free radical process and oxy-gen has a pronounced inhibiting effect. If irradiation is carried out in presence of air, oxygen reacts with radicals in the surface layers of the polymer, slowing crosslinking and giving a brittle, easily damaged sur-face. The damaging effect of oxygen is increased by the ozone formed in the irradiation zone (Shiryaeva et al., 1980).

The main point of this part of study is to discuss that the essential point in crosslinking of some types of polymers is exclusion of air from the media around the polymer by any effective means and the effect of that condition in improving thermal and mechanical characteristics of LDPE wax can be achieved.

Morphological properties

Fig. (4): Effect of irradiation dose on melting tempera-ture.

(a) (b)

(c) (d)

Fig. (6): Effect of irradiation dose on flexural strength.

Fig. (7): Scanning electron micrographs of LDPE wax and bagasse composites.

Fig. (5): Effect of irradiation dose on surface hardness.

LDPE wax content was added by with 35 wt.% as in view (a) and 65 wt. % as in view (b) , where views (a) and (b) show that LDPE wax fills all the small cavities on the surface of agrowaste to form inter penetration achieving a proper mechanical strength and increased with increasing wax content as shown in view (b) where an over flow of LDPE wax has been obviously noticed on the surface of


Composites containing LDPE wax and agrowaste fibers from bagasse were prepared by varying the fi-ber contents, addition of coupling agents and using ionizing irradiation. The results showed that low vis-cous polymer from LDPE wax, TiO2 and ionizing ir-radiation could moderately improve the mechanical, melting temperature and water resistance properties of the prepared composites. It was found that in-creasing the LDPE wax content resulted in increases in hardness, flexural and water resistance.

TiO2 was also more effective in turns for increas-ing thermal melting, hardness and flexural strength. The study offers a new type of plastic wood based on LDPE wax and bagasse composite.

Acknowledgements

Thanks are due to Dr. Faten Ismail (NCRRT) for assistance and suggesting the point of this re-search. The authors gratefully acknowledge ministry of technical education and training, branch of wood industries for application support.

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agrowaste. Also, using coupling agents as titanium dioxide lead to increase the interfacial strength that gave in sequence an increase in both mechanical and thermal properties as shown in view (c). The same trend was achieved by applying ionizing irradiation in absence of air, where crosslinking of LDPE wax lead to increasing molecular weight that enhanced surface hardness and thermal properties as shown in view (d), where the surface view of the sample ap-pears as a highly compacted and smooth pattern .

Photographic view of wood panels of Polyethylene wax and Agrowaste Composite

In figure 8 the photographic view show panels of polyethylene wax and agro-waste composite us-ing hot pressing machine that can be used to pro-duce wood-wax like panels. The powder wax can be added and mixed manually or mechanically with Agrowasts e and then pressed at 110oC for few min-utes (2 – 3 min) to obtain a superior water resistant type of wood-wax panels. This panel acquires an im-provement in hardness and flexibility and high ther-mal properties through irradiation process at 50 kGy.

Fig. (8): Photographic view: wood panel of Polyethylene wax and Agrowaste Composite Conclusion.


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الكثافة منخفض ايثيلني البوىل مشع من خماليط حتضري فى املؤين اإلشعاع إستخدام واملخلفات الزراعية

حممد امحد اهلادى1 وكريستوفر مارك لياو2 و شعبان كامل2 وحسني حسني النحاس1

مت حتضري خماليط مكونة من مشع البوىل ايثيلني منخفض الكثافة واملخلفات الزراعية مثل بقايا قصب السكر عند درجة حرارة 110 م0 بسرعة 80 لفة فى الدقيقة ملدة 5 دقائق حيث كان احملتوى من املخلفات الزراعية يرتاوح من 35إىل 65 % من إمجاىل وزن املخلوط. مت دراسة الصفات امليكانيكية ومعدل إمتصاص املياة والتحليل امليكروسكوبى لدراسة السطح اخلارجى والداخلى للمخاليط احملضرة. حيث الكثافة عند درجة ايثيلني منخفض البوىل الكبري لشمع السيولة تأثري معدل الدراسة مدى اظهرت حرارة 110 م0 فى زيادة معدالت التشرب وختلل الشمع بالكامل داخل ألياف املخلفات الزراعية مما أدى

إىل زيادة معدالت ثباتية وتالصق جزيئات األلياف الزراعية بعضها مع بعض.

الشمع التجانس بني لزيادة معدالت رابطة التيتانيوم كمادة دراسة إستخدام أكسيد أيضا مت واأللياف الزراعية وزيادة معدالت الصهراحلرارى للمخلوط والصالبة امليكانيكية .

للمخاليط وامليكانيكية احلرارية الصفات حتسني فى املؤين الشعاع إستخدام دراس��ة مت أيضا احملضرة إلستخدامها فى تطبيقات األخشاب البالستيكية.

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