Sıkıştırmalı kalıplama yöntemi ile PLA esaslı polimerik kompozit köpüklerinin üretimi ve özelliklerinin incelenmesi
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Tarih
2022
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info:eu-repo/semantics/openAccess
Özet
Büyük çoğunluğu fosil yakıtlardan üretilen polimerler, kullanım ömürlerini tamamladıktan sonra bozunmaya uğramadıkları çevre ortamlarında atık haline gelmekte, her yeni hammadde üretim sürecinde gerek çevreye verilen zarar, gerekse sınırlı fosil yakıt kaynaklarının tüketimi bakımından benzer süreçler tekrarlanmaktadır. Ortaya çıkan bu kısır döngü son yıllarda yenilenebilir kaynaklardan elde edilen çevreci, biyo esaslı ve biyobozunur polimerlere ağırlık verilmesine neden olmuştur. Biyopolimerler, biyouyumlulukları ve biyobozunurlukları sebebiyle başlangıçta sadece biyomedikal uygulamalarda kullanım alanı bulsalar da yapılan çalışmalarla daha iyi anlaşılmaya başlanan fiziksel ve mekanik davranışları sebebiyle otomotiv uygulamalarında da petrol esaslı polimerlere alternatif olarak değerlendirilmeye başlanmıştır. Polilaktik asit (PLA), son yıllarda pek çok uygulama alanında kullanılabilirliği incelenen yüksek çekme dayanımı ve sertliği, kolay işlenebilirliği ile geleneksel petrol esaslı polimerler ile kıyaslanabilir özelliklere sahip olan alifatik bir polyesterdir. PLA kendisine avantaj sağlayan özelliklerinin yanı sıra yüksek maliyet, düşük tokluk, düşük ısıl direnç ve düşük kristalizasyon hızı gibi sınırlayıcı bir takım özelliklere de sahiptir. Ancak yapılan çalışmalarda bu sınırlamaların farklı polimerlerin, dolgu ve katkı sistemlerinin kullanılabildiği kompozit karışımların hazırlanmasıyla giderilebildiği görülmüştür. Literatür çalışmaları incelendiğinde özellikle otomotiv sektörü için önemli olan hafiflik ve karbon dioksit (CO2) emisyonu sınırlamaları sonucunda çalışmalarına ağırlık verilen köpük malzeme üretimlerinin biyopolimerler için de araştırılan ve üzerinde çalışılan bir alan olduğu, bu konuda hem fiziksel hem kimyasal köpürtme ajanları ile gerçekleştirilen çalışmalara son yıllarda ağırlık verildiği görülmektedir. Bu tez çalışmasında, otomotiv sektöründe kullanılabilecek hafif, çevreci, yüksek performanslı PLA esaslı polimerik kompozit köpüklerinin çift vidalı ekstrüder ve sıkıştırmalı kalıplama yöntemleri kullanılarak geliştirilmesi hedeflenmiştir. Bu amaçla, PLA ile birlikte poliamid 6 (PA6) ve polipropilen (PP) polimerleri kullanılarak, ilk aşamada polimer oranlarının belirlenmesi amacıyla 20:80, 30:70, 40:60 ve 70:30 oranlarında polimerik kompozit yapılar hazırlanmıştır. Sıkıştırmalı kalıplama yöntemi kullanılarak hazırlanan bu kompozit yapıların fiziksel, termal, mekanik ve morfolojik özellikleri ve bu özelliklerdeki değişimler incelenip en uygun polimer oranlarına karar verilmiştir. PLA/PP ve PLA/PA6 karışımları için en uygun polimer oranının 30:70 olduğu belirlenmiş, bu aşamadan sonraki çalışmalara bu oranlar ile hazırlanan karışımların kullanılarak devam edilmesi kararlaştırılmıştır. Ancak kimyasal köpürtücü ajan ve uyumlaştırıcı ajanın etkilerinin daha iyi anlaşılabilmesi için 30:70 oranı ile birlikte 70:30 oranı ile de çalışılmasına karar verilmiştir. Bu çalışmanın ikinci aşamasında, kimyasal köpürtücü ajan oranının belirlenmesi amacıyla ağırlıkça %1, %1,5 ve %2 oranlarında kimyasal köpürtücü ajan kullanılarak çift vidalı ekstrüder ve sıkıştırmalı kalıplama yöntemleri ile polimerik köpük yapılar hazırlanmıştır ve elde edilen numunelerin fiziksel, termal, mekanik ve morfolojik özellikleri ve kimyasal köpürtücü ajan oranına bağlı olarak bu özelliklerdeki değişimler değerlendirilmiştir. En uygun kimyasal köpürtücü ajan oranı PLA/PP ve PLA/PA6 karışımları için %1,5 olarak bulunmuştur. Son aşamada ise, köpürtülmüş ikili polimer sistemlerinde uyumsuzluğu gidermek amacıyla polimer oranları ve kimyasal köpürtücü ajan oranları belirlenen yapılar için son olarak en uygun uyumlaştırıcı ajan oranının belirlenmesi için çalışmalar gerçekleştirilmiştir. Uyumlaştırıcı ajan kullanımının fiziksel, termal, mekanik ve morfolojik özellikler üzerindeki etkilerinin değerlendirilmesi amacıyla ağırlıkça %1, %3 ve %5 oranlarında uyumlaştırıcı ajan içeren PLA/PP ve PLA/PA6 karışımları hazırlanarak analizleri gerçekleştirilmiştir. Köpük yapıdaki PLA/PP karışımları için en uygun uyumlaştırıcı ajan oranı ağırlıkça %1 olarak belirlenirken, bu oran köpük yapıdaki PLA/PA6 karışımları için ağırlıkça %3 olarak belirlenmiştir.
The vast majority of polymers which are produced from fossil fuels, become waste in the environment where they do not degrade after the end of their service life, and similar processes are repeated in terms of both environmental damage and consumption of limited fossil fuel resources in each new raw material production process. This vicious cycle has caused that given rise to the investigations of environmental, bio based and biodegradable polymers from renewable sources in recent years. Although biopolymers initially were used only in biomedical applications due to their biocompatibility and biodegradability, they have started to be considered as an alternative to petroleum based polymers in long-term automotive and electronic applications due to their physical and mechanical behaviors, which has been better understood in recent years. Polylactic acid (PLA) is an aliphatic polyester which has been investigated in many applications in recent years with high tensile strength, high hardness, easy processability and has comparable properties with conventional petroleum-based polymers. In addition to its advantages, PLA has a number of limiting properties such as high cost, low toughness, low thermal resistance and low crystallization rate. However, it has been found in the studies that these limitations can be solved by preparing mixtures of different polymers, reinforcing fibers, micro and/or nano fillers and selected additives, and composite materials can be prepared for the desired purpose. When the literature studies are evaluated, it has been seen that the production of foam materials which are focused on as a result of the lightness and CO2 emission limitations, which are especially important for the automotive sector, is a field that has been researched and studied for biopolymers and the studies carried out with both physical and chemical foaming agents have more important in recent years. In this thesis, it is aimed to develop lightweight, environmentally friendly, high performance PLA polymeric composite foams which can be used in automotive sector by using twin screw extruder and compression moulding methods. For this purpose, polyamide 6 (PA6) and polypropylene (PP) polymers were used together with PLA and firstly PLA/PP and PLA/PA6 polymeric composite structures were prepared at 20:80, 30:70, 40:60 and 70:30 ratios in order to determine the optimum polymer ratios. Optimum polymer ratios were detected after the evaluation of the physical, thermal, mechanical and morphological properties and the changes in these properties of these composite structures prepared by compression moulding. The optimum polymer ratio was determined as 30:70 for PLA/PP and PLA/PA6 mixtures, and it was decided to continue the studies after this stage by using the mixtures prepared with these ratios. However, in order to better understand the effects of the chemical foaming agent and the compatibilizing agent, it was decided to work with the ratio of 70:30 as well as 30:70. In the second stage of this study, in order to determine the chemical foaming agent ratio, polymeric foam structures were prepared by twin screw extruder and compression molding methods using 1%, 1.5% and 2% by weight of chemical foaming agent and the physical, thermal, mechanical and morphological properties of the samples and changes in these properties were evaluated. The optimum chemical blowing agent ratio was found to be 1.5% for PLA/PP and PLA/PA6 blends. In the last stage, after the optimum polymer ratios and optimum chemical foaming agent ratios are determined for the structures, in order to eliminate the incompatibility in foamed binary polymer systems, studies have been conducted on the use of compatibilizing agents. For this purpose foamed PLA/PP and PLA/PA6 blends were prepared using 1, 3 and 5% compatibilizing agents and the effects of the use of compatibilizing agent on physical, thermal, mechanical and morphological properties were evaluated. While the optimum ratio of compatibilizing agent was determined as 1% by weight for PLA/PP mixtures in foam structure, this ratio was determined as 3% by weight for PLA/PA6 mixtures in foam structure.
The vast majority of polymers which are produced from fossil fuels, become waste in the environment where they do not degrade after the end of their service life, and similar processes are repeated in terms of both environmental damage and consumption of limited fossil fuel resources in each new raw material production process. This vicious cycle has caused that given rise to the investigations of environmental, bio based and biodegradable polymers from renewable sources in recent years. Although biopolymers initially were used only in biomedical applications due to their biocompatibility and biodegradability, they have started to be considered as an alternative to petroleum based polymers in long-term automotive and electronic applications due to their physical and mechanical behaviors, which has been better understood in recent years. Polylactic acid (PLA) is an aliphatic polyester which has been investigated in many applications in recent years with high tensile strength, high hardness, easy processability and has comparable properties with conventional petroleum-based polymers. In addition to its advantages, PLA has a number of limiting properties such as high cost, low toughness, low thermal resistance and low crystallization rate. However, it has been found in the studies that these limitations can be solved by preparing mixtures of different polymers, reinforcing fibers, micro and/or nano fillers and selected additives, and composite materials can be prepared for the desired purpose. When the literature studies are evaluated, it has been seen that the production of foam materials which are focused on as a result of the lightness and CO2 emission limitations, which are especially important for the automotive sector, is a field that has been researched and studied for biopolymers and the studies carried out with both physical and chemical foaming agents have more important in recent years. In this thesis, it is aimed to develop lightweight, environmentally friendly, high performance PLA polymeric composite foams which can be used in automotive sector by using twin screw extruder and compression moulding methods. For this purpose, polyamide 6 (PA6) and polypropylene (PP) polymers were used together with PLA and firstly PLA/PP and PLA/PA6 polymeric composite structures were prepared at 20:80, 30:70, 40:60 and 70:30 ratios in order to determine the optimum polymer ratios. Optimum polymer ratios were detected after the evaluation of the physical, thermal, mechanical and morphological properties and the changes in these properties of these composite structures prepared by compression moulding. The optimum polymer ratio was determined as 30:70 for PLA/PP and PLA/PA6 mixtures, and it was decided to continue the studies after this stage by using the mixtures prepared with these ratios. However, in order to better understand the effects of the chemical foaming agent and the compatibilizing agent, it was decided to work with the ratio of 70:30 as well as 30:70. In the second stage of this study, in order to determine the chemical foaming agent ratio, polymeric foam structures were prepared by twin screw extruder and compression molding methods using 1%, 1.5% and 2% by weight of chemical foaming agent and the physical, thermal, mechanical and morphological properties of the samples and changes in these properties were evaluated. The optimum chemical blowing agent ratio was found to be 1.5% for PLA/PP and PLA/PA6 blends. In the last stage, after the optimum polymer ratios and optimum chemical foaming agent ratios are determined for the structures, in order to eliminate the incompatibility in foamed binary polymer systems, studies have been conducted on the use of compatibilizing agents. For this purpose foamed PLA/PP and PLA/PA6 blends were prepared using 1, 3 and 5% compatibilizing agents and the effects of the use of compatibilizing agent on physical, thermal, mechanical and morphological properties were evaluated. While the optimum ratio of compatibilizing agent was determined as 1% by weight for PLA/PP mixtures in foam structure, this ratio was determined as 3% by weight for PLA/PA6 mixtures in foam structure.
Açıklama
Anahtar Kelimeler
Polilaktik asit, polipropilen, poliamid 6, PLA-g-MA, kimyasal köpürtme, polimerik köpük kompozitler, Polylactic acid, polypropylene, polyamide 6, chemical foaming, polymeric foam composites
