Kopoliester elastomer (TPC-ET) katkıların ABS'in fiziksel ve mekanik özellikleri üzerine etkisi
Effect of thermoplastic  copolyester elastomers (TPC–ET) on  physical and mechanical properties of ABS
Yazar: KAĞAN VERÇİN
Danışman: PROF. DR. ŞAFAK YILMAZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Malzeme ve İmalat Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: Kimya Mühendisliği = Chemical Engineering ; Makine Mühendisliği = Mechanical Engineering ; Mühendislik Bilimleri = Engineering Sciences

Özet:
Bu tezin amacı ABS hammaddesine katılan TPC-ET ilavesinin, ABS'in mekanik ve fiziksel özelliklerine etkisini incelemektir.

Amorf termoplastiklerden biri olan akrino bütadiyen stiren terpolimer (ABS) hammaddesi geleneksel plastik işleme yöntemleriyle (enjeksiyon, ekstrüzyon, şişirme vb.) ile şekil verilmesinin kolay olması, parlaklığının yüksek ve kolay renklendirilebilmesinden dolayı başta beyaz eşya ve otomotiv sektörü olmak üzere birçok sektörde uygulama alanı bulmaktadır [1].

Kopoliester elastomer olarak da adlandırılan termoplastik kopoliester elastomerler (TPC-ET), yumuşak, esnek bir matris içinde dağılmış sert poliester kristallerden oluşan sentetik bir kauçuktur ve -50°C ve 150 °C arasında esnekliklerini ve kimyasal kararlılıklarını korudukları için otomotiv ve beyaz eşya gibi birçok sektörde uygulama alanı bulmaktadır [2]. Bu tez çalışmasında, termoplastikler gibi işlenebilen ama elastomer özelliklerine sahip TPC-ET ile ABS hammaddesinin ağırlıkça %5, %10, %15 ve %20 karışım oranlarında, plastik-kauçuk karışımlarının fiziksel ve mekanik özelliklerinin katkı oranına bağlı olarak değişimi incelenmiştir.

Hazırlanan numunelerin UV dayanımlarının, yaş boya tutunma performanslarının, yüzey gerilimi ölçümlerinin, sertlik ve çizilme dayanımı karşılaştırmaları yapılmıştır. Ayrıca, oda koşullarında tutulan ve parlatıcı sıvı ortamda yaşlandırılan numunelere çentik darbe testleri ve çekme deneyleri yapılmıştır. Son olarak DSC analizi ve yoğunluk ölçümleri yapılmış SEM görüntüleri ile içyapıları incelenmiştir. Sonuçlar karşılaştırmalı olarak verilmiştir.

Sonuç olarak TPC-ET katkı malzemesi olarak ABS'in ekstra darbe dayanımı ihtiyacı duyduğu estetik uygulamalarda, mamulün çizilme, boya tutma ve sertlik değerlerinde azalmaya yol açmadan kullanılabilir. Ayrıca kimyasal etkileşim sonrası gevrekleşmelerin, TPC-ET katkı oranının artışıyla orantılı olarak azaldığı belirlenmiştir.

Abstract:
The aim of this thesis is to investigate the effects of TPC-ET as a modifier on mechanical and physical properties of ABS.

Acrylonitrile-butadiene-styrene terpolymer (ABS) is one of the amorphous thermoplastic is favourable for many sectors of application areas including automotive and white goods sectors mainly due to easy to machine and fabricate by using conventional plastic processing methods (injection, extrusion, blow moulding, etc.) and the high gloss and colourability. The large diversity of end uses makes ABS terpolymer one of the most successful of the engineering thermoplastics available. İts position in terms of both properties and price between the more highly priced, high performance engineering plastics and the lower priced commodity plastics makes ABS the material of choice for many applications and the largest volume engineering thermoplactic sold. ABS consists of discrete, crosslinked polybutadiene which are grafted with poly(styrene-co-acrylonitrile)(SAN) and embedded in a SAN matrix. The SAN copolymer, chemically bound to the polybutadiene, is refered to as grafted SAN, while the non-bound material is called free or rigid SAN. [1].

Thermoplastic Copolyester elastomers also known as copolyester elastomers are block copolymers—that is, the two different types of chemical repeating units that make up the chainlike molecules occur in long sequences, or blocks. The hard sequences usually consist of polybutylene terephthalate (PBT), a stiff polyester resin. The soft sequences consist of any one of a number of polyesters or polyethers, such as polytetramethylene ether glycol. Upon cooling from a melt, the PBT sequences spontaneously cluster together in hard crystalline domains that connect the softer elastomeric sequences. The hard and soft regions are thus held together by mechanical interlocking and by strong intermolecular attractions, but they are not chemically interlinked into a permanent network as is the case with traditional vulcanized rubbers. For this reason, copolyester elastomers can be heated above the melting point of the crystalline domains (approximately 200 °C ) and then reprocessed—a property ideal for recycling. They retain their useful rubbery properties between –50 and 150 °C [2].

Polymer blends are capable of providing materials with extended useful properties beyond the range that can be obtained from single polymer equivalents. Polymer blend represents very important field in processing of new materials, which has better properties in comparison with the net polymers.

In this thesis, changes in the physical and mechanical properties of plastics-rubber blends which are ABS and TPC-ET that can be processed like a thermoplastics but have elastomeric properties in varying weight in the sizes of 0%, 5%, 10%, 15%, 20% by weight.

Comparisons of UV resistance, wet paid adhesion, surface tension, hardness and scratch resistance of prepared samples were done.

According to the UV test results, Hytrel® causes an increasing in 'b' value of colour through the (+) direction (yellowness). Also, it is observed that colour differences between the variants become less after 200 hrs UV test.

Wet paint adhesion perfomance of samples were investigated. Cross cut test results and surface tension measurement show that TPC-ET does not affect neat ABS's performace

According to Hardness and scratch resistance test, increase of scratch resistance that proportionally to increase of TPC-ET was observed although negligible hardness reduction.

In addition, tensile tests and notched impact test were done for chemically aged samples and samples held under the room conditions. According to impact test results, increase of impact resistance that proportionally to increase of TPC-ET was observed. In order to see chemical resistance of ABS/Hytrel belnds,the similar Charpy impact tests were repeated for the test bars that conditioned for 24 hours in a solution of 5% rinse aid. It is observed that Hytrel addition seems to improve the impact resistance. Crystalline structure of Hytrel caused impact resistancy retention while 100% ABS's values are decreasing by 6.4%.

Tensile modulus is decreasing by TPC-ET mixing ratio increases even after 5% rinse aid conditioning. Likewise yield strain values increase by TPC-ET ratio increases. It is observed that there is linear variaton with TPC-ET addition on the tensile propertise of composite specimens and tensile test results support impact resistance results. shows proper miscibility of two phases which gives the improved result of impact strength

In addition, DSC analysis and density measurement were done. The aim of the present study is to show the effect of blend ratios on the mechanical properties and study the probability to creating compatible system for the polymer blend. The best methods for detecting miscibility by Differential Scanning Calorimeter (DSC). If the DSC test detects one glass transition temperature for the polymer blend, then this leads to averment of state of miscibility. The results from this work show that the mechanical properties for blend system are better than those of pure polymers, also the (DSC) test gives good indications of improving state of miscibility for most blend ratios; there is only one glass transition temperature between the two values of pure polymers.

Lastly, internal structure of samples were examined by SEM. Results are given in comparison. SEM micrographs show that shows proper miscibility of two phases which gives the improved result of impact strength. there is good dispersion, there is no any agglomeration or flow lines between TPC-ET and ABS at highest magnification

Consequently, TPC-ET can be used as a modifier for ABS when there is a need for extra impact resistance for aesthetic parts without causing a reduction in scratch resistance, hardness and wet paint adhesion. In addition, decrease of embrittelement proportionally to increase of TPC-ET was observed after chemical interaction.