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任务一：概述：聚对苯二甲酸乙二醇酯化学式为-[OCH2-CH2OCOC6H4CO]-英文名: polyethylene terephthalate，简称PET，为高聚合物，由对苯二甲酸乙二醇酯发生脱水缩合反应而来。
对苯二甲酸乙二醇酯是由对苯二甲酸和乙二醇发生酯化反应所得。
PET 是乳白色或浅黄色、高度结晶的聚合物，表面平滑有光泽。
在较宽的温度范围内具有优良的物理机械性能，长期使用温度可达120℃，电绝缘性优良，甚至在高温高频下，其电性能仍较好，但耐电晕性较差，抗蠕变性，耐疲劳性，耐摩擦性、尺寸稳定性都很好。
作为包装材料PET优点：①有良好的力学性能，冲击强度是其他薄膜的3~5倍，耐折性好。
②耐油、耐脂肪、耐稀酸、稀碱，耐大多数溶剂。
③具有优良的耐高、低温性能，可在120℃温度范围内长期使用，短期使用可耐150℃高温，可耐-70℃低温，且高、低温时对其机械性能影响很小。
④气体和水蒸气渗透率低，既有优良的阻气、水、油及异味性能。
⑤透明度高，可阻挡紫外线，光泽性好。
⑥无毒、无味，卫生安全性好，可直接用于食品包装目前使用最广的聚酯容器是聚对苯二甲酸乙二醇酯(PET)吹塑瓶。
PET瓶于二十世纪七十年代由杜邦公司研究成功，由于其性能优越，问世后受到塑料界的高度重视，特别是随着PET吹塑成型工艺和设备不断趋于完善以及PET瓶级树脂生产技术的不断提高、生产规模的不断扩大，成本大幅度下降，大大推动了PET瓶的开发应用。
PET热灌装瓶首先在果汁饮料及茶饮料等饮料主流产品包装上得到了广泛的应用，现阶段，在辣椒等农产加工制品包装中愈来愈受到欢迎，大有取代玻璃瓶的势头。
PET不透明，而瓶坯之所以透明，靠的就是冷却。
冷却不好将降低瓶坯的冷却速率，会导致缩水、瓶坯变形和影响循环时间，为避免此情况，要做好：水质处理，定期清理水道，检查水流量及水压，型芯及型腔的拆洗等。
合成方法及工艺的确定目前，世界各国PET生产采用的技术路线主要有3种。
一、生产现状产品简介：聚对苯二甲酸乙二醇酯化学式为-OCH2-CH2OCOC6H4CO- 英文名：polyethylene terephthalate，简称PET，为高聚合物，由对苯二甲酸乙二醇酯发生脱水缩合反应而来。
对苯二甲酸乙二醇酯是由对苯二甲酸和乙二醇发生酯化反应所得。
PET 是乳白色或浅黄色、高度结晶的聚合物，表面平滑有光泽。
在较宽的温度范围内具有优良的物理机械性能，长期使用温度可达120℃，电绝缘性优良，甚至在高温高频下，其电性能仍较好，但耐电晕性较差，抗蠕变性，耐疲劳性，耐摩擦性、尺寸稳定性都很好。
二、生产方法比较1.目前，世界各国PET生产采用的技术路线主要有3种。
（１）、DMT法采用对苯二甲酸二甲酯（DMT）与乙二醇（EG）进行酯交换反应，然后缩聚成为PET。
（2 ）、PTA法采用高纯度的对苯二甲酸（PTA）或中纯度对苯二甲酸（MTA）与乙二醇（EG）直接酯化，连续缩聚成聚酯。
（３）、EO法用PTA与环氧乙烷（EO）直接商化，连续缩聚成PET。
2.生产方法比较：因此我们采用PT A法生产PET。
二、生产工艺条件影响因素分析1．原料的影响1.1、PTA的粒度通常认为PTA 的粒度大小及形状对PET产品质量影响不大,只是大粒子“清晰点”(即PTA全部溶于液相,体系由非均相混淆转为均相透明)来的晚些。
但在文献[ 2 ]中有如下介绍, PTA 的粒度通常以粒径表示, 一般以100～130μm 为宜。
它主要影响PTA/ EG的浆料性质和酯化反应速度。
在实际生产中发现,粒径小, 浆料动力黏度大,输送阻力大,能耗高,酯化反应速度快,反应温度略低,在整个生产过程中易产生挥发性异物,使预缩聚和后缩聚系统的真空管道中出现白色粉末,预缩聚物过滤器清理周期短;粒径过大,则出现与上述相反的结果[3 ]。
PTA平均粒径对浆料稳定性(浆料结块程度)的影响见图21. 2 PTA纯度PTA 是生产PET 的主要原料,其杂质特别是42CBA(42羧基苯甲醛)含量增加,对酯化反应和缩聚反应都是有害的。
pet《新版1(标准版)》等级考试英语试卷test2全文共6篇示例，供读者参考篇1My Big English Test AdventureHi there! My name is Emma and I'm 10 years old. I just had the craziest day taking a really important English test called the PET 'New Version 1 (Standard)' Level Exam Test 2. It was super long and kind of hard, but I actually had a lot of fun with it! Let me tell you all about my big test adventure.It started bright and early this morning. My mom woke me up at 6am which is SO early for a Saturday! I was pretty grumpy at first, but then I remembered why I had to get up - for my huge English test! I got dressed super fast and ate a big breakfast of scrambled eggs, toast, and orange juice to fill up my brain.Then mom and I headed off to my school where the test was happening. There were kids from all over town there, looking just as nervous as me. We had to go to the gym and that's where all the desks were set up for the test. It felt just like taking one of my normal school tests, except there were a whole lot more kids there!The first part of the test was listening. The teachers played audio recordings and we had to answer multiple choice questions about what we heard. That wasn't too bad since I'm a pretty good listener. Although there was one weird story about a guy who lost his pet frog that completely stumped me!After listening, we moved right into the reading section. This is where things got really tough! The passages were all brand new topics I'd never read about before. There were texts about baking cupcakes, the history of skateboards, and even an article about ants. My brain was so fried trying to understand and answer the questions about all those new subjects.We did get a break for snacks and running around outside after the reading part, which was awesome. I desperately needed some fresh air and a snack to re-energize. I had a little bag of trail mix and an apple juice box. Yum!The next part was writing. We had to write a short story based on a picture they showed us. I actually thought this would be hard, but I ended up having a blast with it! The picture was of a kid and his dog, so I wrote all about the adventures they got into one summer day at the park. I used so many descriptive words to paint the picture in my mind. I was so proud of my little story!The very last section was speaking, which was probably the most nerve-wracking of all. They split us up into pairs and we had to take turns asking each other questions and responding. My partner asked me things like "What is your favorite subject in school?" and "What did you do last weekend?" I tried so hard to give detailed, grammatically correct responses. Phew!After what felt like an entire day (but was really only a few hours), the test was finally over. I've never been so relieved and exhausted at the same time! As I walked out with my mom, I just felt proud for giving that big challenge my all. Maybe I didn't ace every single part, but I know I tried my very best.A couple weeks later, I'll get my official results in the mail. I'm crossing my fingers that I did well enough to get that PET certificate! Even if I didn't though, the whole experience made me feel way more confident about my English skills. I'm just proud I could stick with it and work through all those different reading, writing, listening, and speaking sections.If you've got a big English test like that coming up, my advice is to get plenty of rest, fuel up with brain foods, and don't psych yourself out too much. You'll do great if you just stay focused and believe in yourself! Tests are hard but also kind of fun if you look at them like a challenge to rise to.Whew, I'm getting tired just thinking back on that crazy day again! I'm going to go take a nap before I have to start getting ready for my soccer game later. A kid's work is never done! Thanks for listening to my big English test adventure.篇2My Pet Level 1 English TestHi everyone! My name is Jenny and I'm going to tell you all about my recent experience taking the Pet Level 1 (Standard Version) English Test 2. I was a little nervous beforehand, but it ended up being really fun!The test had four sections - reading, writing, listening and speaking. We started with the reading section first thing in the morning. There were lots of different reading passages about all kinds of topics like animals, hobbies, school life and more. Some of the passages were conversations between people too.After each passage, there were multiple choice questions to test how well we understood what we had read. The questions asked things like who said what, what the main idea was, or asked us to fill in missing details. I tried my best to read everything really carefully so I could find the right answers.My favorite reading passage was the one about a girl and her pet hamster. It was so cute hearing about all the funny things her hamster would do, like stuffing its cheeks full of food! I have a hamster too, so I could really relate to that story.Once we finished the reading section, it was time for writing. We had to write a short story based on some pictures that were provided. The pictures showed a family going on a picnic in the park. In my story, I wrote about how they packed a yummy lunch, played fun games like frisbee, and had to run home when it started raining really hard! Writing stories is one of my favorite activities.After we turned in our writing samples, we took a break for snacks and recess before moving on to the listening part of the test. For this section, we listened to different recordings and had to answer comprehension questions just like we did for reading.One recording was about a boy giving instructions for taking care of a class pet over the weekend. Another one was a phone conversation between a mom and dad trying to figure out their family's schedule for the upcoming week. Listening carefully was so important to catch all the details!The final part of the test was the speaking section. We had to describe a series of pictures that told a story, like going on a tripor celebrating a birthday. The test administrators wanted to see how well we could put sentences together to explain what was happening in each picture.I love using my imagination, so this speaking part was really fun for me. For the pictures about a birthday party, I talked about how the family went to the mall to go shopping for presents, helped decorate with balloons and banners, and then sang "Happy Birthday" around a big cake. Speaking English clearly is something I'm working on, so tests like this help a lot.Even though there were a lot of different sections, I actually really enjoyed taking this Pet Level 1 English Test 2. It gave me a chance to practice all the reading, writing, listening and speaking skills I've been learning in my English classes at school. I'm already looking forward to taking the next level test!I'm sure I didn't get every single question right, but I tried my absolute best on each part of the test. No matter what my score ends up being, I'm proud of myself for giving it my all and not getting discouraged. Tests like this are great practice to keep improving my English abilities.Now I'm just counting down the days until I get my results back! I'll be sure to celebrate with my family if I pass on to the next Pet level. And if not, it's totally fine - I'll just study harderand try again next time. The most important thing is never giving up when learning a new language.Well, thanks for letting me tell you all about my Pet Level 1 test day! Being bilingual in English and my native language is so useful. I'm really glad my parents encouraged me to learn English from a young age. It opens up so many opportunities for the future.I hope this essay gave you a good idea of what to expect if you'll be taking the Pet English tests too. Study hard, don't stress too much, and most of all - have fun putting your English skills to the test! Learning a language should be an exciting adventure. OK, I'll sign off for now...bye!篇3Title: My Exciting Pet Exam Adventure!Hi there, friends! Today, I'm going to tell you all about my experience with the "Pet New Version 1 (Standard Edition)" level exam. It was a thrilling journey, and I can't wait to share it with you!First things first, what exactly is this "Pet" exam? Well, it's a test that measures your English language skills, and it's designedfor young learners like us. The "New Version 1 (Standard Edition)" level is the first step in this adventure, and it's all about showing how much we've learned so far.Now, let me tell you about my preparation for the exam. I studied really hard, practicing my reading, writing, listening, and speaking skills every day. My teacher gave me lots of practice tests, and my parents helped me with flashcards and fun games. It was a lot of work, but I knew it would all be worth it in the end.Finally, the big day arrived! I woke up early, had a healthy breakfast, and made sure I had all my supplies ready – pencils, erasers, and a big smile on my face! When I arrived at the exam center, I saw lots of other kids my age, and we were all feeling a little bit nervous but also excited.The exam itself was divided into different sections. First up was the reading part, where we had to read short passages and answer questions about them. I took my time, read carefully, and tried my best to understand every word. Next came the writing section, where we had to write a short story or essay. I let my imagination run wild and tried to use all the vocabulary and grammar I had learned.After a short break, it was time for the listening section. We had to listen to conversations or announcements and answerquestions based on what we heard. I focused all my attention and tried to catch every detail. Finally, the speaking part was my favorite! We had to have a short conversation with the examiner, introducing ourselves and answering some questions. I spoke clearly and confidently, remembering all the practice I had done.When the exam was over, I felt a huge sense of relief and accomplishment. I had given it my all, and no matter the result, I was proud of myself for trying my best.A few weeks later, the results arrived, and guess what? I passed the "Pet New Version 1 (Standard Edition)" level exam! I was over the moon with joy and couldn't wait to share the good news with my family and friends.Looking back, I realized that this exam was more than just a test – it was a learning experience that taught me the value of hard work, perseverance, and believing in myself. I'm already looking forward to the next level and can't wait to see what new adventures and challenges await me in the world of English language learning.So, if you ever have the chance to take the "Pet" exam, don't be afraid! Study hard, believe in yourself, and most importantly, have fun along the way. Who knows, you might just surprise yourself with how much you can achieve!篇4My Pet English Test AdventureHi friends! My name is Lily and I'm 10 years old. I just took the Pet English test level 1 and I want to tell you all about my exciting adventure with it!A few months ago, my English teacher Mrs. Roberts told our class that we would all be taking the Pet test. She said it's a really important English exam that shows how good our English skills are. I was a little nervous at first because tests can be scary. But Mrs. Roberts said not to worry and that if we studied hard, we'd do great.For weeks, we practiced all the things that would be on the test like reading, writing, speaking and listening. We did lots of practice tests too. My favorite part was the speaking practice because I love talking and telling stories! The reading was a bit harder for me though since some of the passages were pretty long with tricky vocabulary words.Finally, the big day came for the real Pet test! I had a good breakfast of eggs, fruit, and juice to keep my energy up. My mom wished me luck and dropped me off at school where the test washappening. There were kids from other schools there too, all taking the same Pet level 1 test.The test started with listening first. We had to listen to recordings and answer questions about what we heard. Like understanding directions or identifying the main idea. It was kind of fun picking out all the details I could understand.Next up was reading! We read different texts like stories, advertisements, and articles. Then we had to answer comprehension questions about them. Some passages were easier than others, but overall I tried my best. The key was going slowly and rereading parts I got stuck on.After a break for a snack, we did the writing section. We had to write a story based on some pictures, which was my favorite part! I loved using my imagination to make up a fun narrative. We also had to write emails, messages and other practical writing exercises.The last part was speaking, which made me a little nervous. I had to describe a scene, answer questions, and roleplay situations like ordering food or asking for directions. But I took a deep breath and reminded myself of all the practice I did. It ended up being not too bad!By the end, I was exhausted but so proud of myself for making it through such a big test. A few weeks later, I got my results in the mail and... I passed! I got a score that shows my English level is very good for my age. My parents were overjoyed and took me out for my favorite dinner of pizza to celebrate.Taking the Pet test level 1 was hard work but also really rewarding. It showed me how much English I've already learned and gave me confidence to keep studying hard. I'm so excited to continue improving my English skills and maybe take an even higher level Pet test in the future!If you're a kid learning English, I highly recommend trying out the Pet tests when you're ready. It's a great way to get experience with real English exams in a supportive setting. Just be sure to practice, stay calm on test day, and most importantly - believe in yourself! You've got this!篇5PET Exam Test 2Reading (25 points)Part 1 (5 points)Read the text and questions below. For each question, mark the correct letter A, B or C.My Favorite PetI have a pet dog called Buddy. He is a golden retriever and is three years old. Buddy has long golden fur and a friendly smile. He loves to play fetch and go for walks in the park. Every morning, I take Buddy out for a nice long walk before going to school. We stop at the playground and I throw his favorite tennis ball for him to catch.Buddy is a very good dog. He never makes a mess in the house and always comes when I call his name. At nighttime, Buddy sleeps in a cozy little bed next to my room. Sometimes I read him bedtime stories and he falls asleep listening to my voice. Buddy is my best friend and I love him very much!What kind of pet does the writer have?A. A dogB. A catC. A birdWhat color is Buddy's fur?A. BlackB. GoldenC. BrownWhat does Buddy like to play?A. FetchB. Hide and seekC. Tug of warWhere does Buddy sleep at night?A. On the couchB. In the writer's bedC. In his own little bedHow does the writer feel about Buddy?A. She loves him a littleB. She doesn't like himC. She loves him very muchPart 2 (10 points)Read the text and answer the questions below in full sentences.My Summer VacationLast summer, my family went on an amazing vacation. We drove five hundred miles to a beautiful beach town called Seashore City. When we arrived, I was so excited to see the bright blue ocean and the soft sandy beaches. Our hotel room had a balcony with an incredible view of the water.We spent our days swimming, building sandcastles, and collecting pretty seashells. In the evenings, we would walk along the beach boardwalk and get ice cream cones. My favorite flavor was chocolate chip! One night, we even saw a outdoor movie playing on a huge screen right on the beach. It was so much fun sitting under the stars watching a film.On the last day, we went on a boat tour to look for dolphins. The tour guide told us lots of interesting facts about the ocean and marine life. We were lucky enough to spot three gray dolphins swimming and jumping right next to our boat! I will never forget that amazing sight.Our vacation ended too soon and before I knew it, we had to pack our bags and make the long drive back home. I had such an incredible time at Seashore City and made so many wonderful memories. I can't wait to go back again next summer!Where did the writer go on vacation?How did the family travel to get there?What did the writer enjoy doing at the beach?What special event did the family attend one night?What animal did the writer get to see up close on the boat tour?Part 3 (10 points)Read the definitions and write the correct word from the word bank.Word Bank: afford, recycle, community, volunteer, donate, environment, pollution, endangeredTo give money, goods or time freely to help a person or cause. ________Animals or plants that may soon disappear forever. ________A group of people living together in one place or area.________Damage caused to air, water or land by harmful substances. ________To change waste into reusable materials. ________The natural world of land, air, water, plants and animals.________To give some of your time to help others for free. ________To be able to pay for something using your money. ________Writing (25 points)You have read a book about a young wizard who goes on an exciting magical adventure. Write a book review sharing your opinion of the story. Include details about the main character, the plot, and whether you would recommend the book to other students your age. Your review should be 200-250 words.Speaking (25 points)Part 1: Answer questions about yourself.Examples:• What is your favorite subject in school?• What games or sports do you like to play?• What do you like to do after school?Part 2: Describe the picture.• What do you see in the picture?• What is happening?• How do you think the people/animals feel?Part 3: Role-play situation.• A new student is joining your class. Introduce yourself and show the new student around the school. Explain where things are located like the library, playground, cafeteria etc.Part 4: Make a case persuading your parents to get you a pet.• Explain what kind of pet you want.• Give reasons why you want this pet and why pets are good for kids.• Promise how you will take care of it and be responsible.篇6My Pet Level 1 English Test ExperienceHi everyone! My name is Emma and I'm 10 years old. I just took the pet《新版1(标准版)》等级考试英语试卷test2 and I wanted to tell you all about it. It was a really big test for me because English is still pretty hard. But I studied a lot and gave it my best shot!The first part of the test was the listening section. I had to listen to some conversations and answer questions about what I heard. There were people talking about things like their favorite foods, weekend plans, after school activities and more. Listening is one of the hardest parts for me because the people talk so fast! But I tried my best to listen carefully to every word.After the listening section, we moved on to the reading part. We had to read a few different stories and passages then answer comprehension questions about them. One story was about a girl and her pet hamster which was really cute. Another one was about two friends going on a camping trip with their families. The passages weren't too too long which was good because my eyes start to get tired if I have to read a lot without taking breaks.The writing section came next. We had to write a short story based on some picture prompts. The pictures showed a boy and his dog playing outside. So I wrote a story about a kid who loved spending time with his puppy and all the fun adventures they would go on together. I tried to use a lot of descriptive words to make my story interesting and detailed.Then it was time for the speaking section which made me pretty nervous! We had to answer some questions and also describe a series of pictures to demonstrate our English speakingabilities. The pictures were about a family going on vacation which was a fun topic. I just tried to slow down, pronounce each word clearly, and not be afraid to take pauses if I needed to think for a second.Finally, the last part was the integrated skills section where we had to demonstrate reading, writing, listening and speaking all combined. We read a short passage about after school clubs, listened to a conversation about the same topic, then had to give a spoken summary of the key points. It was pretty challenging to put all those skills together at once!Overall, I worked really hard to prepare for this test over the past few months. My teachers gave me lots of practice materials and my parents helped me study at home too. There were some parts that were pretty difficult for me, but I felt good about the effort I put in. No matter how I scored, I'm proud of myself for giving it my best. Tests can be stressful but it's important to stay positive and have fun while learning English.Now I get to take a break and enjoy my summer vacation! Over the next few months I'll keep practicing my English skills through reading, watching shows, and playing language games. I love learning new words and phrases to better communicate with people from all around the world. English opens up so manydoors and opportunities. I'm already looking forward to taking the next level of the test when I'm older!Well, that's my experience with the pet《新版1(标准版)》等级考试英语试卷test2. It challenged me for sure, but I had fun along the way. Thanks for reading my story! Let me know if you have any other questions.。
