The direct use of natural rubber latex (NRL) as a binder for emulsion paints did not produce emulsion paints with good opacity, washability resistance, and regulated touch drying time, even when mixed with polyvinyl acetate (PVAc). This study aimed to study the properties of opacity (hiding power), washability resistance, and set drying touch time of emulsion paint with a binder added from a mixture of modified natural rubber latex (NRL) and PVAc. NRL modifications included UV photodepolymerization with TiO2 catalyst and grafting copolymerization of methyl methacrylate and styrene (NRL-g-(MMA-co-St)). NRL was mixed with PVAC at ratios of 0/100; 15/85; 25/75; 35/65; 50/50; 100/0% w/w before being used as a binder for emulsion paint. Emulsion paint samples had different binder contents, namely 2, 4, 6, and 8% w/w. Tests on paint samples included opacity using a UV-Vis spectrophotometer (EASYSPEC safas Monaco), washability using the Digital BGD 526 Wet Abrasion Scrub Tester, and drying time set using the ASTM STP500 procedure. The results showed that the opacity (hiding power), washability resistance, and set drying touch time met the emulsion paint standards for all binder levels, except the 100% w/w modified NRL composition. The higher level of NRL in the binder causes these properties to decrease and become unstable. The best opacity (hidden power), washing resistance, and drying touch time were obtained on modified NRL with a concentration of 15% w/w. The binder content in the paint was around 4% w/w, with an opacity of about 1.78% abs, washing resistance of 12 times, and the set drying touch time to 80 min.

Kabupaten Kuantan Singingi merupakan daerah produsen komoditi karet alam terbesar di Provinsi Riau. Sejumlah besar gabungan kelompok tani (GAPOKTAN) karet di beberapa desa dan didukung oleh pemerintah daerah sudah membentuk Asosiasi Petani Karet Kuantan Singingi (APKARKUSI), untuk melakukan pengendalian kualitas dan pelelangan bahan olah karet (bokar). Asosiasi ini juga berencana akan mengembangkan industri hilir berbahan baku utama bokar. Tujuan kegiatan ini adalah untuk melakukan persiapan awal terkait dengan rencana pengembangan produk hilir karet tersebut. Kegiatan tahap awal ini meliputi penentuan kualitas bokar dari petani yang berafiliasi dengan APKARKUSI, jenis produk hilir karet tahap awal dan perencanaan tata letak mesin dan sarana produksinya, dan spesifikasi yang diinginkan pasar dari produk sandal karet sebagai salah satu jenis produk hilir karet yang akan dikembangkan. Kualitas bokar yang dikelola oleh APKARKUSI relatif sangat baik (yaitu dengan kadar karet kering berkisar 60-65 %). Jenis produk hilir karet yang siap diproduksi adalah brown crepe rubber, dimana kinerja proses produksinya masih perlu dioptimalkan. Spesifikasi produk sandal karet yang akan diproduksi bersifat dinamis, yaitu dengan mempertimbangkan faktor model, kualitas, kenyamanan dan harga. Untuk proses produksinya, perlu merujuk kepada tata letak mesin dan sarana produksi yang dapat menhasilkan kinerja yang efektif dan efisien.

Infrastructure developments in recent decades have led to increasing demand for high-performance paints for construction and decorative purposes. Emulsion paint is water-based paint that is commonly used for coating the internal and external surfaces of a building. The quality and performance of this emulsion paint are highly dependent on its constituent components, such as binders, pigment, solvents, and additives. Emulsion paints initially used conventional formaldehyde-based binders and were, for some reason, prohibited from being used in paints due to health and environmental issues. The development of bio-based paints with natural rubber latex (NRL) has the potential to be developed as an emulsion paint binder. The results showed that NRL grafting of styrene monomer or MMA showed much better resistance to wet scrub and abrasion than PVAc at a monomer concentration of 20%, for styrene, and 30%, for MMA, with washability values reaching each of 11 and 12 cycles at 4% binder concentration. The NgSt20-4 and NgMMA30-4 binders’ abilities to overcome wet scrub and abrasion increased with increasing paint binder concentrations, reaching 22 and 23 cycles at 10% binder concentration. Overall, the combination of NRL grafted with MMA monomer and 30% PVAc showed better performance and could compete with commercial binders such as PVAc. Adding methyl methacrylate monomer increases the adhesion and cohesion properties of the binder and increases the binder’s resistance to scrubbing and wet abrasion. However, the combination of NRL grafted MMA and 30% PVAc showed the same effectiveness as NRL grafted MMA without PVAc, with more economical production costs.

The molecular weight of natural rubber varies greatly, from only a few hundred thousand to more than one million. Liquid natural rubber (LNR) products generally use natural rubber in the form of latex with a relatively low molecular weight, which ranges from a molecular weight of 600,000 g / mol. This study aims to determine the molecular weight of LNR products made from the chemical depolymerization process of natural rubber latex with a molecular weight of more than one million. The natural rubber used latex with 20% Dry Rubber Content (KKK). The natural rubber depolymerization process used NaNO2 and H2O2 degrading agents with a CoCl2 catalyst at 80 °C. H2O2 levels were kept constant at 1 parts per hundred rubber (phr), and NaNO2 levels vary at 0; 2; 3; and 4 phr. After the reactor temperature reaches 80°C, the CoCl2 catalyst was added, which level varied at 0; 1; 3; and 5 phr. The reaction time was varied, which 7, 8, and 9 hours. The results of LNR product was purified to form a semi-gel, and molecular weight was analyzed using gel permeable chromatography (GPC). The results showed that the lowest molecular weight of the resulting LNR product was 108,335 g / mol from the initial molecular weight of 1,384,638 g / mol.

Polyvinyl acetate (PVAc) has long been known as a binder material to improve the washability, opacity (hiding power), and viscosity of commercial emulsion paints. This study aims to study the properties of opacity (hiding power), washability resistance, and viscosity of emulsion paint added with a binder from a mixture of natural rubber latex (NRL) and PVAc. Emulsion paint samples were made with a binder content of 4, 6, and 8% w/w. The binder was made from a mixture of NRL and PVAc with various NRL levels of 0%, 15%, 25%, 35%, 50%, and 100% w/w. Testing of paint samples includes washability using a digital BGD 526 Wet Abrasion Scrub Tester and viscosity testing using a HAAKE 6R digital viscometer. At the same time, the opacity test uses the Indonesian Standard (SNI 3564:2009). The results showed that the opacity met the standard emulsion paint for all binder levels, except for the composition of NRL 100% w/w at all binder levels. The higher the NRL content in the binder causes the washability resistance and paint viscosity to decrease and become unstable. The best washability resistance and viscosity properties were obtained at NRL in a binder of 15% w/w and a binder content of 8% w/w, with washability resistance properties of 50 times and a viscosity of 3300 cp.