回收PET瓶片回炉三次后，特性粘度从0.65掉到0.50，拉出来的片材一折就裂。改性厂老板盯着粘度计发呆——粘度上不去，料就只能当低级回料卖，一吨少赚两千元。他知道该加扩链剂，但之前试过一款，加过量后交联起晶点，整锅料报废。
回收料每回一次炉，分子量就矮一截，扩链剂负责把它接回去。
本文由长期经营塑料原料及助剂的宁波市科隆新材料有限公司整理，牌号与批次信息以实际供货渠道为准。
扩链剂速查总表：两类活性基团一页看完
扩链剂的本质是“带反应性尾巴的小分子”，一头抓住分子链上断出来的羧基，一头抓住羟基，把两段链重新缝在一起。按活性基团不同，主流分环氧类和噁唑啉类两条路线。下面这张表把代表品种、参数和用途列清楚。
| 体系 | 代表品种 | 关键参数 | 典型制品 | 添加比例 |
|---|
| 环氧类（ADR） | 巴斯夫Joncryl系列、国产对标ADR | 多环氧官能团，熔融接枝增粘 | 回收PET瓶片、PBT、PC | 0.1%-0.5% |
| 噁唑啉类 | 含双噁唑啉结构品种 | 与羧基反应扩链 | PA、回收聚酯体系 | 0.2%-0.8% |
| 异氰酸酯/其它 | 双官能反应型 | 湿敏、需控温 | TPU、部分回收体系 | 0.1%-0.5% |
注：以上环氧当量和粘度提升为参考，实际效果受回料品质影响，以官方TDS和实测为准。
图1 扩链剂——把断裂的回收料分子链重新接长
断链不是报废，接上还能再用一茬
这位主角，是回收料的接骨医生。宁波市科隆新材料有限公司长期经营各类塑料助剂及改性原料，覆盖国内外多个品牌货源，在环氧ADR扩链剂、回收PET增粘体系上有稳定供货渠道。而扩链剂这个品类，本质上是回收塑料的“分子量还原剂”——塑料每经历一次挤出、注塑，分子链就被热和剪切剪断一些，端羧基、端羟基越断越多，分子量一路往下掉，黏度跟着稀，制品就越做越脆、越做越软。
扩链剂就像给回收料请了个接骨医生，断了的分子链一节节再接回去。
环氧类ADR的动作很漂亮：一个分子上挂着多个环氧基团，进入熔体后，环氧环同时和断链上的羧基、羟基发生开环反应，相当于一手牵一段链。一个ADR分子能同时“招呼”好几个链端，于是短链们被织回成长链，特性粘度IV回升，熔体强度和力学性能跟着回来。这就是行业说的“扩链增粘”。
ADR的妙处在于一个分子同时牵好几段断链——0.1%-0.5%的料，干的却是把碎链条重新织成布的活。
但这里有个分寸感：扩链不是加得越多越好。ADR过量，反应点太密，分子链之间会过度交联，从“接长”变成“结块”，熔体里出现凝胶颗粒，薄膜上就是一个个晶点，注塑件表面就是麻点。所以行业里反复强调：先测回收料的初始IV和酸值，再倒推ADR用量。
哦，你拿回炉三次的PET直接拉片？脆得一折就裂还想当新料卖，这是给客户埋雷。
逐品种速查：ADR看环氧当量，牌号看用途
扩链剂牌号看着杂，其实抓住“环氧当量”和“基材匹配”两个关键，就能筛掉八成干扰项。
粘度计上多读出的那零点零几，就是回料从'垃圾价'翻到'拉丝价'的分水岭。
环氧类ADR（以巴斯夫Joncryl ADR系列为代表的多环氧官能团扩链剂）：回收PET瓶片增粘的主力。分子设计上把多个环氧官能团接在一个丙烯酸酯主链上，熔融后反应均匀、增粘效率高，适合PET瓶片→片材→纤维这条回收链。选它的信号：回收PET、PBT、PC需要提熔体强度和IV。注意：加工温度窗口要合适，过高会让ADR提前交联。
供货提示：环氧ADR类扩链剂科隆新材可稳定供货，每批附环氧当量数据，公斤级试样支持先做粘度提升对比。
噁唑啉类扩链剂：对端羧基反应尤其灵敏，在PA回收料、聚酯回收体系里用得较多，增粘的同时对羧基封端，对后续耐水解也有帮助。选它的信号：回收PA、要求同时扩链和封端。注意：分散和反应温度窗口比ADR窄，要小试确认。
流变改性剂（高熔体强度助剂）：严格说是扩链的延伸应用，目的不只是增粘，更是调节熔体强度和应变硬化，让回收料能上发泡、吹塑、片材热成型这些“对熔体有要求”的工序。选它的信号：回收料要做发泡片、吸塑杯。
回收料越回越稀，ADR把黏度拉回来，废片才真正变废为宝。
替代对照：进口ADR能不能换？先看这张表
做回收PET的采购都关心：巴斯夫Joncryl这类进口ADR贵，国产对标品能不能顶上去？坦率说，通用回收增粘场景，国产ADR在增粘效率上已经能打，但在反应均匀性、凝胶含量控制、长期批次稳定性上仍需逐批验证。下面这张表把替代方向和切换前提列清楚。
| 原用进口方向 | 典型应用 | 可对标方案 | 切换前提 |
|---|
| 巴斯夫Joncryl ADR（高粘级） | 回收PET瓶片增粘 | 国产环氧ADR对标品 | 小试对比IV回升幅度、凝胶/晶点含量 |
| 巴斯夫Joncryl ADR（通用级） | 片材/热成型增粘 | 国产ADR | 对比熔体强度、应变硬化、热成型窗口 |
| 高粘级回收PET纺丝 | 纤维级增粘 | 国产高环氧当量ADR | 对比纺丝稳定性、断丝率、白度 |
| PA回收体系噁唑啉扩链 | PA6/66回收增粘 | 国产噁唑啉类 | 对比端羧基下降、IV回升 |
表中方向仅供替代参考，切换前仍需逐批实测。替代老流程：小试平行对比IV、凝胶含量、力学保留，客户书面确认后小批量，再放量。
扩链剂替代要看特性粘度提升幅度，科隆新材寄送公斤级环氧ADR试样时附环氧当量数据，客户可以直接做IV对比和力学性能测试，确认粘度回升效果再切换。
扩链剂不是加越多越好，过量会交联起晶点，别把料做成一锅浆糊。
行业场景速查：谁在靠扩链救回料
同样是加ADR，做回收PET片材和做工程塑料改性，对增粘幅度的要求差着量级。下面这张表按行业拆解。
| 行业 | 典型制品 | 客户最先问的参数 | 推荐方案 | 认证要求 |
|---|
| 回收包装 | PET瓶片→片材、吸塑杯 | IV回升幅度、晶点含量 | 环氧ADR 0.2%-0.4% | 食品接触GB 4806.7 |
| 化纤 | 回收PET短纤、再生纺丝 | 纺丝稳定、断丝率 | 高粘ADR 0.15%-0.3% | OEKO-TEX、可追溯 |
| 汽车 | 回收PP/PA改性内饰 | 熔体强度、气味 | ADR+相容剂体系 | IATF 16949、低VOC |
| 片材吸塑 | 外卖盒、托盘回收片 | 热成型窗口、壁厚均匀 | 流变改性型ADR | GB 4806系列 |
| 电子电器 | 回收PC/PBT合金增韧增粘 | 缺口冲击、外观 | ADR+增韧复配 | UL黄卡、RoHS |
举个场景：做回收PET吸塑杯，客户要求片材热成型时不被拉破、壁厚均匀。单纯提IV不够，还得看熔体强度和应变硬化，这时候选流变改性型ADR比单纯增粘型更对症。
添加量与搭配要点：三条记住不走偏
扩链剂用量跟着回收料的“病况”走，先化验再下药。下面三条是行业反复验证的逻辑。
回收料降黏先上ADR，别一上来就猛掺新料硬凑成本。
◆ 回收PET瓶片通用增粘：环氧ADR 0.2%-0.4%，配合适量抗氧，IV回升到目标区间即可，过量防晶点。
◆ 高要求片材/热成型：流变改性型ADR 0.3%-0.5%，兼顾IV和熔体强度，配合成核剂调节结晶。
◆ 回收PA体系：噁唑啉类0.3%-0.8%，边扩链边封端羧基，加工前务必烘干。
搭配要点还有三条：一是ADR和水分“八字不合”，加工前回收料必须充分干燥，否则水分会竞争性消耗环氧基团；二是扩链常和相容剂、增韧剂搭用——回料来源杂、组分乱，单靠扩链救不回相容性；三是每批回收料批次差异大，建议固定取样测IV和酸值，按批微调ADR用量，别一张配方用到底。
断链：接上就好。
回收不废，扩链回本。
加工与合规红线：这几个坑别踩
扩链剂用得好是救星，用不好就是晶点和麻点。下面这张表把加工参数和后果列清楚。
| 环节 | 参考值 | 做错的后果 |
|---|
| 回收料干燥 | PET 120-140℃×4-6h，PA 80-100℃×4-8h | 带水加工→环氧基团被水消耗，扩链失效 |
| 挤出温度 | PET 260-280℃，PBT 230-250℃ | 温度过高→ADR提前交联、出现凝胶 |
| 螺杆剪切 | 中等剪切、充分混炼 | 剪切不足→分散不均、局部增粘不够 |
| 停留时间 | 避免死角，控制短停留 | 停留过久→过度交联、晶点增多 |
| 用量控制 | 先测IV/酸值再定0.1%-0.5% | 盲目加量→晶点、麻点、力学下降 |
合规红线：回收料做食品接触制品（如再生PET片材），必须符合GB 4806.7及国家对食品接触再生材料的相关规定，并保留来源可追溯文件；出口需符合REACH、FDA相关条款。ADR残留与迁移要随货检测报告归档。
FAQ：配方和采购常问的五个问题
Q1：国产扩链剂能不能替代进口料？
通用回收PET增粘，国产ADR的增粘效率已经能满足大多数场景；但在纺丝、高端片材这类对凝胶和晶点零容忍的场景，进口在批次一致性上仍有积累。稳妥做法是先公斤级平行对比IV回升、凝胶含量和外观晶点，过了再小批量放量。平行测试用的小样，科隆新材可按公斤级寄送，附环氧当量和IV数据供比对。
Q2：加了ADR为什么片上还是有晶点？
先查三点：一是ADR加过量导致交联；二是回收料没烘干，水分消耗反应同时引发局部凝胶；三是螺杆分散不均。把用量按IV倒推、料烘干、分散做好，晶点通常能压下去。
Q3：扩链剂和增韧剂是一回事吗？
不是。扩链剂解决“分子量低、黏度稀”，把长链接回来；增韧剂解决“材料脆、抗冲差”，靠弹性体分散相吸收冲击。回收改性常两者并用：ADR先把料接长提黏，再加POE类增韧剂扛冲击。
Q4：回收料要加多少ADR合适？
没有固定值，靠初始IV和目标IV倒推。一般在0.1%-0.5%之间：新料边角料回掺加0.1%-0.2%即可；多次回收、IV掉得多的瓶片加到0.3%-0.5%。宁少试加、逐步补，别一次堆够。
Q5：扩链剂会让材料变脆吗？
正常扩链增粘反而会改善力学。但过量交联、或分散不良产生凝胶，会让料变脆、表面麻点。所以核心不是“加不加”，而是“加多少、怎么分散”。
选型三步清单：照着做不踩坑
◆ 第1步·化验底账：先测回收料的初始IV（特性粘度）、端羧基值和灰分，明确要把分子量补到哪个区间。
◆ 第2步·对号选剂：PET/PBT回收选环氧ADR，PA回收看噁唑啉类，需发泡/热成型选流变改性型；按IV差定0.1%-0.5%用量，并核对与相容剂、增韧剂的搭配。
◆ 第3步·小试验证：公斤级平行对比IV回升、凝胶/晶点、力学保留和外观，过客户书面确认后再小批量放量。
回收料能不能用，粘度计上见分晓
扩链剂主要用于回收PET、PC、PA等的粘度恢复和流变改性，环氧类ADR通过多环氧基团对接羧基和羟基。科隆新材供应环氧ADR类扩链剂，可提供环氧当量和推荐用量范围；回收料增粘和挤出涂覆场景可推荐对应牌号，公斤级试样支持先做特性粘度和力学性能对比，注意控制用量避免交联。
去年，一家做回收PET改性的厂，瓶片回炉后粘度太低拉不了片。科隆新材给他们推荐了环氧ADR扩链剂，添加量约0.3%，寄了公斤级样品。客户试产后，特性粘度从约0.55升到约0.72，片材弯折不再开裂，终于能卖到拉丝级的价格。老板算了一笔账，每吨多赚约一千五百元，扩链剂成本只增加约三十元。
回炉三次的PET，直接拉片还是先扩链？
声明：本文涉及的品牌、商标及产品名称权归各自原厂所有。本文为第三方选材知识分享，文中提及的牌号、参数、价格、认证及应用案例仅供参考，具体以各生产企业官方最新资料及批次检测报告为准。本文不构成任何采购或投资建议，读者据此操作风险自担。
After recycled PET bottle flakes were reprocessed three times, the intrinsic viscosity dropped from 0.65 to 0.50, and the sheets pulled out would crack at a single fold. The modification plant owner stared at the viscometer in a daze—if the viscosity can't be raised, the material can only be sold as low-grade recycled material, losing two thousand yuan per ton. He knew that chain extenders should be added, but he had previously tried one type; after adding too much, crosslinking occurred at nucleation points, and the entire batch of material was ruined.
Every time recycled material goes through the furnace, its molecular weight drops, and the chain extender is responsible for restoring it.
This article is compiled by Ningbo Kolong New Materials Co., Ltd., which has long been engaged in the business of plastic raw materials and additives. The grade and batch information are subject to the actual supply channels.
Quick Reference Table for Chain Extenders: See Two Types of Active Groups on One Page
The essence of a chain extender is a 'small molecule with a reactive tail,' which grabs the carboxyl group at the broken end of a molecular chain with one end and the hydroxyl group with the other end, stitching the two chain segments back together. According to the different active groups, the mainstream approaches are the epoxy type and the oxazoline type. The table below clearly lists representative varieties, parameters, and uses.
| system | Representative variety | Key parameters | Typical products | Add ratio |
|---|
| Epoxy (ADR) | BASF Joncryl series, domestic counterpart ADR | Multiple epoxy functional groups, melt grafting thickening | Recycling PET bottle flakes, PBT, PC | 0.1%-0.5% |
| Oxazoline class | Varieties containing a bisoxazoline structure | Chain extension reaction with carboxyl groups | PA, recycled polyester system | 0.2%-0.8% |
| Isocyanate/Others | Bifunctional | Moisture-sensitive, temperature control required | TPU, partial recycling system | 0.1%-0.5% |
Note: The above epoxy equivalent and viscosity increase are for reference only. The actual effect is influenced by the quality of recycled materials, and the official TDS and actual measurements shall prevail.
Figure 1 Chain Extender – Reconnecting the Broken Molecular Chains of Recycled Material
A broken chain is not scrap; once reconnected, it can be used again.
The protagonist here is a doctor for recycled materials. Ningbo Kolon New Materials Co., Ltd. has long been engaged in various plastic additives and modified raw materials, covering sources from multiple domestic and foreign brands. It has stable supply channels for epoxy ADR chain extenders and recycled PET viscosity-increasing systems. Essentially, chain extenders are 'molecular weight restorers' for recycled plastics—each time plastic undergoes extrusion or injection molding, some of its molecular chains are broken by heat and shear, resulting in more terminal carboxyl and hydroxyl groups, the molecular weight decreases, viscosity thins, and the products become increasingly brittle or soft.
A chain extender is like hiring an orthopedic doctor for recycled material, reconnecting the broken molecular chains bit by bit.
The action of epoxy ADRs is quite elegant: a single molecule carries multiple epoxy groups, and once it enters the melt, the epoxy rings simultaneously undergo ring-opening reactions with the carboxyl and hydroxyl groups at the broken chain ends, essentially connecting one end to another. One ADR molecule can 'handle' several chain ends at the same time, so the short chains are woven back into long chains, the intrinsic viscosity IV rises again, and the melt strength and mechanical properties return. This is what the industry refers to as 'chain extension and viscosity increase.'
The brilliance of ADR lies in the fact that a single molecule can simultaneously connect several chain breaks—0.1%-0.5% of the material is enough to do the work of reweaving broken chains into fabric.
But there's a sense of moderation here: chain extension isn't better the more you add. If there's too much ADR, reaction sites become too dense, and the molecular chains will be over-crosslinked, turning 'lengthening' into 'clumping.' Gel particles appear in the melt, small crystals show up on the film, and the surface of injection-molded parts will have a rough texture. That's why the industry repeatedly emphasizes: first measure the initial IV and acid value of the recycled material, then back-calculate the amount of ADR to use.
Oh, are you taking PET that's been through the furnace three times and directly turning it into sheets? It's so brittle that it cracks at a single bend, and you still want to sell it as new material—this is setting a trap for the customer.
Quick reference by variety: Check the epoxy equivalent for ADR, check the application for the grade
There are many grades of chain extenders, but if you focus on the two key points—'epoxy equivalent' and 'substrate compatibility'—you can filter out 80% of the interference factors.
The extra zero point something read on the viscometer is the dividing line where the returned material goes from 'scrap price' to 'drawing price'.
Epoxy ADRs (multi-epoxy functional chain extenders represented by BASF Joncryl ADR series): the main agents for increasing the viscosity of recycled PET flakes. In molecular design, multiple epoxy functional groups are attached to an acrylate backbone, enabling uniform reaction and high thickening efficiency after melting, making them suitable for the recycling chain PET flakes → sheets → fibers. Signal to choose: recycled PET, PBT, PC require increased melt strength and IV. Note: the processing temperature window must be appropriate; too high a temperature can cause the ADR to crosslink prematurely.
Supply Notice: Cologne New Materials can stably supply epoxy ADR-type chain extenders, with epoxy equivalent data provided for each batch. Kilogram-scale samples are available to first conduct viscosity enhancement comparisons.
Oxazoline-based chain extenders: They are particularly reactive with terminal carboxyl groups and are frequently used in PA recycled materials and polyester recycling systems. While increasing viscosity, they also cap carboxyl groups, which is beneficial for subsequent hydrolysis resistance. The signal for choosing them: recycling PA and requiring both chain extension and end-capping. Note: The dispersion and reaction temperature window is narrower than that of ADR, and small-scale testing is needed to confirm.
Rheology modifiers (high melt strength additives): Strictly speaking, they are an extended application of chain extension, aiming not just to increase viscosity but also to adjust melt strength and strain hardening, allowing recycled materials to be used in foaming, blow molding, and sheet thermoforming—processes that have 'requirements for the melt.' Signals for choosing it: when recycled materials are to be used for foam sheets or thermoformed cups.
The more recycled material is reused, the thinner it becomes. ADR brings the viscosity back, allowing the scrap pieces to truly turn waste into treasure.
Alternative comparison: Can imported ADR be exchanged? First, look at this table
Purchasers dealing with recycled PET are all concerned: imported ADRs like BASF Joncryl are expensive, so can domestic equivalent products replace them? Frankly speaking, for general recycled PET viscosity boosting scenarios, domestic ADRs can already compete in terms of thickening efficiency, but in terms of reaction uniformity, gel content control, and long-term batch stability, each batch still needs to be verified. The table below clearly outlines the alternative options and prerequisites for switching.
| Original Import Direction | Typical Applications | Benchmark solution | Switch premise |
|---|
| BASF Joncryl ADR (High Viscosity Grade) | Increasing viscosity by recycling PET bottle flakes | Domestic epoxy ADR reference product | Preliminary test comparing IV recovery range, gel/crystallization point content |
| BASF Joncryl ADR (General Purpose) | Sheet / Thermoforming Adhesive | Domestic ADR | Comparison of melt strength, strain hardening, and thermoforming window |
| High-viscosity recycled PET spinning | Fiber-grade thickening | Domestic high epoxy equivalent ADR | Compare spinning stability, breakage rate, and whiteness |
| PA recycling system oxazoline chain extension | PA6/66 Recycled Viscosity Enhancer | Domestic oxazoline class | Comparison of carboxyl end decrease and IV rebound |
The directions in the table are for alternative reference only; each batch still needs to be tested before switching. Alternative to the old process: small-scale parallel comparison of IV, gel content, and mechanical retention; after written confirmation from the customer, proceed to small batches, and then scale up.
The replacement of chain extenders depends on the degree of viscosity increase. When Kolon New Materials sends kilogram-level samples of epoxy ADR, they include the epoxy equivalent data, allowing the customer to directly perform IV comparisons and mechanical property tests to confirm the viscosity recovery effect before switching.
Chain extenders are not better the more you add; excessive amounts will crosslink the crystal points, so don’t turn the material into a pot of paste.
Industry Scene Quick Lookup: Who is Relying on Chain Expansion to Rescue Materials
Adding ADR is the same, but for recycling PET sheets and for engineering plastic modification, the requirements for the increase in viscosity differ by orders of magnitude. The table below breaks it down by industry.
| Industry | Typical products | The parameters the customer asked about first | Recommended plan | Certification requirements |
|---|
| Recyclable Packaging | PET bottle flakes → sheets, thermoforming cups | IV recovery range, wax content | Epoxy ADR 0.2%-0.4% | Food Contact GB 4806.7 |
| synthetic fiber | Recycling PET staple fiber, regenerated spinning | Spinning stability, breakage rate | High viscosity ADR 0.15%-0.3% | OEKO-TEX, Traceable |
| Car | Recycling PP/PA Modified Interiors | Melt strength, odor | ADR compatible agent system | IATF 16949, low VOC |
| Sheet Thermoforming | Takeout Box and Tray Recycling Sheet | Thermoformed window, uniform wall thickness | Rheologically modified ADR | GB 4806 Series |
| Electronics and electrical appliances | Recycle PC/PBT alloy for toughening and enhancing adhesion | Gap impact, appearance | ADR Toughening Compound | UL Yellow Card, RoHS |
For example: When recycling PET blister cups, customers require the sheet to not tear during thermoforming and to have uniform wall thickness. Simply increasing IV is not enough; melt strength and strain hardening must also be considered. In this case, choosing a rheology-modified ADR is more appropriate than a simple viscosity-increasing type.
Dosage and key points of combination: Remember these three to stay on track
The amount of chain extender should follow the 'condition' of the recycled material; test it first before adding chemicals. The following three points are the logic repeatedly validated by the industry.
Reduce the viscosity of recycled material by first adding ADR, don't just immediately mix in a lot of new material to forcibly cut costs.
◆ General viscosity increase for recycled PET flakes: Epoxy ADR 0.2%-0.4%, combined with an appropriate amount of antioxidant, regenerate IV to the target range, avoid crystallization points with excess.
◆ High-demand sheets/thermoforming: Rheology-modified ADR 0.3%-0.5%, balancing IV and melt strength, combined with nucleating agents to adjust crystallization.
◆ Recycled PA system: Oxazoline 0.3%-0.8%, simultaneously chain-extending and end-capping carboxyl groups, must be dried before processing.
There are three more key points for matching: First, ADR and moisture are 'incompatible'; recycled material must be fully dried before processing, otherwise moisture will competitively consume epoxy groups. Second, chain extenders are often used together with compatibilizers and toughening agents—since recycled materials come from various sources and have mixed components, chain extenders alone cannot restore compatibility. Third, there is significant batch-to-batch variation in recycled materials; it is recommended to consistently sample each batch to measure IV and acid value, and to slightly adjust the amount of ADR per batch, rather than using one formula for everything.
Broken chain: Just reconnect it.
Recycling is not wasted, expanding the chain returns the capital.
Processing and Compliance Red Lines: Avoid These Pitfalls
Using a chain extender well is a lifesaver; using it poorly results in crystal spots and rough spots. The table below clearly lists the processing parameters and their consequences.
| link; segment; part | Reference value | The consequences of doing wrong |
|---|
| Recycled material drying | PET 120-140℃ × 4-6h, PA 80-100℃ × 4-8h | Water processing → epoxy groups are consumed by water, chain extension fails |
| Extrusion temperature | PET 260-280℃, PBT 230-250℃ | Excessive temperature → ADR crosslinks prematurely, forming gel |
| Screw shear | Medium shear, fully mixed | Insufficient cutting → uneven dispersion, inadequate local tackiness |
| Duration of stay | Avoid dead spots, control short stays | Staying too long → excessive cross-linking, increased crystal points |
| Dosage control | First measure the IV/acid value, then determine 0.1%-0.5% | Blindly increasing the amount → pinholes, specks, mechanical degradation |
Compliance Red Lines: Recycled materials used for food contact products (such as recycled PET sheets) must comply with GB 4806.7 and the relevant national regulations on recycled materials for food contact, and source traceability documents must be retained; exports must comply with relevant REACH and FDA provisions. ADR residues and migration must be filed along with the inspection report of the shipment.
FAQ: Five Common Questions About Formulas and Procurement
Q1: Can domestically produced chain extenders replace imported materials?
General PET recycling adhesion enhancers: the adhesion efficiency of domestic ADRs can already meet most scenarios; however, in situations like spinning and high-end sheet production, where zero tolerance for gels and crystalline spots is required, imported products still have an advantage in batch consistency. The prudent approach is to first perform a kilogram-scale parallel comparison of IV recovery, gel content, and appearance of crystalline spots, and only proceed to small-batch scaling if successful. For the parallel testing samples, Kolon New Materials can send them at kilogram scale, along with epoxy equivalent and IV data for comparison.
Q2: Why are there still crystal spots on the film after adding ADR?
First, check three points: one is that excessive ADR causes cross-linking; two is that the recycled material wasn’t dried, and the moisture consumes the reaction while also causing localized gelation; three is uneven screw dispersion. By calculating the amount based on IV, drying the material, and ensuring good dispersion, the crystallization point can usually be lowered.
Q3: Are chain extenders and toughening agents the same thing?
No. Chain extenders solve the problem of 'low molecular weight, low viscosity' by reconnecting the long chains; toughening agents solve the problem of 'brittle material, poor impact resistance' by absorbing impact through the elastomer dispersed phase. In recycled modification, both are often used: ADR first extends the chains to increase viscosity, then POE-type toughening agents are added to resist impact.
Q4: How much ADR should be added to the recycled material?
There is no fixed value; it is deduced based on the initial IV and the target IV. Generally, it is between 0.1%-0.5%: for new material scrap, blending 0.1%-0.2% is sufficient; for repeatedly recycled bottle flakes with a significantly reduced IV, add 0.3%-0.5%. It’s better to add slightly and gradually rather than pile it all in at once.
Q5: Will the chain extender make the material brittle?
Proper chain extension and tackiness increase can actually improve mechanical properties. However, excessive crosslinking or poor dispersion leading to gelation will make the material brittle and cause surface graininess. So the key is not 'whether to add,' but 'how much to add and how to disperse it.'
Three-step checklist for choosing: Follow it to avoid pitfalls
◆ Step 1 · Test the baseline: First, measure the initial IV (intrinsic viscosity), end carboxyl value, and ash content of the recycled material to determine the target molecular weight range.
◆ Step 2 · Select the agent accordingly: For PET/PBT recycling, choose epoxy ADR; for PA recycling, use oxazoline types; for foaming/thermoforming, choose rheology-modified types. Determine the dosage according to IV difference at 0.1%-0.5%, and verify the combination with compatibilizers and toughening agents.
◆ Step 3 · Small-scale verification: Conduct kilogram-level parallel comparisons for IV recovery, gel/crystallization point, mechanical retention, and appearance. Only after written confirmation from the customer should small-batch scale-up be carried out.
Whether recycled material can be used can be seen on the viscometer
Chain extenders are mainly used for viscosity recovery and rheological modification of recycled PET, PC, PA, etc. Epoxy ADR links with carboxyl and hydroxyl groups through multiple epoxy groups. Kolon New Materials supplies epoxy ADR chain extenders and can provide the epoxy equivalent and recommended dosage range; for viscosity increase and extrusion coating scenarios of recycled materials, the corresponding grades can be recommended. Kilogram-level samples support preliminary comparison of intrinsic viscosity and mechanical properties. Be careful to control the dosage to avoid cross-linking.
Last year, a plant that modified recycled PET found that the viscosity of bottle flakes after re-melting was too low to produce sheets. Kolon New Materials recommended an epoxy ADR chain extender, with an addition of about 0.3%, and sent kilogram-level samples. After trial production, the intrinsic viscosity increased from about 0.55 to about 0.72, sheet bending no longer cracked, and finally, it could be sold at fiber-grade prices. The boss calculated that he earned about 1,500 yuan more per ton, while the chain extender cost increased by only about 30 yuan.
For PET re-melted three times, should it be sheeted directly or chain-extended first?
Disclaimer: The brands, trademarks, and product names mentioned in this article belong to their respective manufacturers. This article is a third-party material selection knowledge sharing. The mentioned grades, parameters, prices, certifications, and application cases are for reference only. Specifics should be based on the latest official information from manufacturers and batch test reports. This article does not constitute any procurement or investment advice, and readers operate at their own risk.
